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Policy, Education, and Legal Aspects of Energy

2010;():1-12. doi:10.1115/ES2010-90029.

Complex environmental systems are frequently broken into politically manageable pieces, and a policy focusing on a single environmental issue can undermine other policy priorities. It is a nontrivial concern that domestic and international legislation focused on reducing emissions of climate-related pollution have not adequately considered policy effects on related systems like water. The goal of this work is to assess the possible effects of the American Clean Energy and Security Act of 2009 (ACES, passed by the House of Representatives in June) on water resources in Texas.

Topics: Water
Commentary by Dr. Valentin Fuster
2010;():13-23. doi:10.1115/ES2010-90071.

South Africa is a “canary in a coal mine” for the world’s upcoming ecological crises, especially regarding electrical energy provision for a developing modern society, because aspects of the South African situation may be repeated elsewhere when ecological limits constrain economic activity. We describe the South African context in terms of social issues and economic development policies, environmental issues, and the electrical energy situation in the country. We explore implications of the South African context for the provision of electrical energy in terms of development objectives, climate change, the electrical grid, water, and solar, wind, ocean, and hydro energy resources. Thereafter, we explore future directions for electrical energy provision in the country, including some important questions to be answered. Next, we offer a rational way forward, including an assessment favoring concentrated solar power (CSP) as a path of least resistance for decoupling South Africa’s energy use from upstream and downstream environmental impacts. We conclude with some learnable lessons from the South African context for the rest of the developing and developed world.

Commentary by Dr. Valentin Fuster
2010;():25-34. doi:10.1115/ES2010-90130.

The American Clean Energy and Security Act of 2009 (H.R. 2454) introduces a combined federal standard for efficiency and renewable electricity. This standard requires utilities to supply a portion of their customer’s demand using energy efficiency measures and renewable electricity generation. (1) This manuscript discusses an analysis conducted on the effect of H.R. 2454 on Texas’s electricity generation mix. In order to benchmark the net opportunity for energy efficiency, this analysis includes the historical trends in electricity consumption by sector and per capita for two states, Texas and California. This manuscript contains discussion on findings in two key areas. First, the overall consumption patterns seen historically in Texas compared to California including key differences found in each sector: residential, industrial and commercial/other. Second, the factors that contributed to these patterns including policy mechanisms, technological advances, and shifts in industry that contributed to these patterns. These findings are then applied to electricity consumption and generation mix projections in Texas. Evaluating these projections reveals the potential environmental impacts of H.R. 2454 on Texas.

Commentary by Dr. Valentin Fuster
2010;():35-44. doi:10.1115/ES2010-90179.

In this work we estimate the amount of energy required to produce the food consumed in the United States in 2002 and 2007. Data from government sources and the scientific literature were used to calculate the energy intensity of food production from agriculture, transportation, manufacturing, food sales, storage and preparation. Most data were from 2002; consequently we scaled all data from other years to 2002 by using ratios of total energy consumption in 2002 to total energy consumption in the year data were reported. We concluded that food production required at least 7,880±733 trillion BTU in 2002 and 8,080±752 trillion BTU of energy in 2007, over a third of which came from food handling in homes, restaurants and grocery stores. The energy used to produce food represents approximately 8% of energy consumption. Our estimate is for the energy required to produce the food consumed in the United States and takes into account food imports and exports. To account for net food exports in the agriculture sector we calculated values for the energy intensity of ten food categories and then used the mass of domestic food consumption in each category to calculate the energy embedded in the food consumed in the United States. The amount of energy required to produce the food consumed in the United States has policy implications because it is a substantial fraction of total energy consumption and is responsible for a commensurate amount of greenhouse gas emissions. There are many opportunities for decreasing the energy intensity of food production at all steps of the food system. Education of the public and policy measures that promote energy efficiency in the food sector have the potential for decreasing food waste and the energy intensity of the food system.

Commentary by Dr. Valentin Fuster
2010;():45-55. doi:10.1115/ES2010-90185.

Although consensus has not been reached regarding the most efficient mechanism to curb anthropogenic greenhouse gas emissions, rising concern over the consequences of global climate change and consequent shifts in public and political sentiment suggest that carbon legislation will be instituted in the US in the near future. The recent climate change bill passed in the House of Representatives titled The American Clean Energy and Security Act of 2009 (HR 2454) includes provisions for a cap-and-trade system intended to reduce the nation’s greenhouse gas emissions 83% by 2050. Consequently, it is likely that some means of carbon pricing will take effect that will make it more expensive to emit greenhouse gases. In a carbon constrained economy, it will become increasingly important to consider every stage of food production and consumption in order to evaluate the potential opportunities for emission reductions. This analysis uses Life-Cycle Assessment to estimate the social cost of food production by quantifying the associated negative externalities under a range of potential carbon prices, using meat and grain as examples. It concludes that 0.42 and 16.0 kg of lifecycle CO2 e are embedded in 1 kg of grain and beef production, respectively. Consequently, the marginal cost associated with the emissions caused by grain production under a carbon price range of $10 and $85 per t CO2 e is estimated to be between $.004 and $0.036 per kg of grain. By comparison, the estimated marginal cost associated with beef production over the same range of carbon pricing is $0.16 and $1.36 per kg of beef. Considering that the US produces 12 billion kg of beef per year, this range indicates that the carbon cost of beef production alone might fall anywhere between $1.9 and $16.3 billion per year, depending on whether and how a carbon price is applied. This uncertainty and potential carbon price could significantly impact the cost of carbon-intensive foods.

Commentary by Dr. Valentin Fuster
2010;():57-64. doi:10.1115/ES2010-90348.

Our vision at Texas Tech University is to develop work force through education and training that can provide a steady stream of personnel for the rapidly growing wind energy industry. Our objectives are to establish interdisciplinary curricula at all levels of higher education which can educate and train people to work in the wind energy industry including design and construction, maintenance, business, finance, supervision, management, policy making, environmental impact, as well as research and development. The nature and breadth of the wind energy industry demands that the degree programs be interdisciplinary with flexibility to provide emphasis in various areas. Two degree programs, bachelor and doctoral degree curricula are presented in the paper.

Topics: Wind energy
Commentary by Dr. Valentin Fuster
2010;():65-73. doi:10.1115/ES2010-90349.

Presently the sustainable development stratagem has made the green buildings to be a trend of building industry in China, and the assessment to the green buildings is becoming more and more important in developing the green buildings. In this paper the meaning of the green building assessment is explained, several main domestic and foreign green building assessment systems are analyzed and compared, and the common ground and limitations of these assessment methods are presented. Then a novel assessment index system which is more comprehensive, scientific and suitable for green buildings in China is developed by using the life cycle assessment method. This system contains six categories including land saving and outdoor environment, energy saving and utilization, material saving and utilization, water saving and utilization, indoor environment quality and economy. According to the decision-making stage, design stage, construction stage, operation and maintenance stage, each category is divided into more concrete indexes. At last the established assessment system is used to evaluate a typical building in Xi’an, China. The final novel assessment index system is of theoretical and practical significance for the assessment and development of green buildings in China.

Commentary by Dr. Valentin Fuster
2010;():75-84. doi:10.1115/ES2010-90365.

An equilibrium economic model for policy evaluation related to electricity generation has been developed; the model takes into account the non-renewable and renewable energy sources, demand and supply factors and environmental constraints. The non-renewable energy sources include three types of fossil fuels: coal, natural gas and petroleum, and renewable energy sources include nuclear, hydraulic, wind, solar photovoltaic, biomass wood, biomass waste and geothermal. Energy demand sectors include households, industrial manufacturing and commercial enterprises (non-manufacturing businesses such as software firms, banks, restaurants, service organizations, universities, etc.). Energy supply takes into account the electricity delivered to the consumer by the utility companies at a certain price which maybe different for retail and wholesale customers. Environmental risks primarily take into account the CO2 generation from fossil fuels. The model takes into account the employment in various sectors and labor supply and demand. Detailed electricity supply and demand data, electricity cost data, employment data in various sectors and CO2 generation data are collected for a period of seventeen years from 1990 to 2006 in U.S. The model is calibrated for the aggregate data. The calibrated model is then employed for policy analysis experiments if a switch is made in sources of electricity generation, namely from fossil fuels to renewable energy sources. As an example, we consider a switch of 10% of electricity generation from coal to 5% from wind, 3% from solar photovoltaic, 1% from biomass wood and 1% from biomass waste. It should be noted that the cost of electricity generation from different sources is different and is taken into account. The consequences of this switch on supply and demand, employment, wages, and emissions are obtained from the economic model under three scenarios: (1) energy prices are fully regulated, (2) energy prices are fully adjusted with electricity supply fixed, and (3) energy prices and electricity supply both are fully adjusted.

Commentary by Dr. Valentin Fuster
2010;():85-93. doi:10.1115/ES2010-90410.

The attention towards the topic of reducing the energy expenditures has dramatically grown in recent crisis times that have forced firms to reduce them. This reduction in energy expenditures of a firm can be pursued through a wise energy procurement (we can call it “administrative energy efficiency”), thus with a reduction in the specific cost of energy (both electricity and other energy sources). But, the highest effective saving — for the whole system — would come from a direct reduction of the consumption, thus increasing the so-called “operational energy efficiency”, the unique true energy efficiency, implying the effort of the whole firm, since it requires a lower and wiser use of energy, and new and more efficient technologies. It is quite diffused the perception that governments are now taking measures to reach a common and more efficient environmental and energetic policy, but the effort is still not sufficient. The attention has obviously been paid towards the industrial sector, that covers about 30% of the consumption, second just after transportation: since now several actions have been taken to achieve the energy performance of buildings, but very few in the operations. Furthermore, it should be clear that to be really effective in this field governments should focus their attention on Small & Medium Enterprises (SMEs), usually less efficient than Large Enterprises (LEs), since SMEs represent the vast majority of the total number of industries and cover a consistent share of the energy consumption of a whole domestic industrial sector. This paper aims at providing an overview of the most effective interventions for reducing energy consumption in industrial operations that have been successfully implemented in a large number of case studies investigated in North America and Europe. The paper provides different scenarios according to the implementation of those interventions, characterized all by being Best Available Technologies and Practices, showing the impact on the energy consumption for a set of Italian industrial districts. The final results show that, under certain assumptions, the financial support of the most effective interventions eventually provided by governments’ energy efficiency policies, would lead to a widespread increase of the overall energy efficiency of a district with strong benefits for the whole industrial system.

Commentary by Dr. Valentin Fuster
2010;():95-102. doi:10.1115/ES2010-90430.

Alternative energy laboratory experiences have been developed to help support a new Green Concentration recently offered for the first time in the mechanical engineering program at Western New England College. These laboratories, which give students hands-on experience and a better understanding of basic concepts in wind energy, solar energy, and fuel cell technology, utilize an improved Alternative Energy Active Learning Platform, as well as newly developed indoor/outdoor Alternative Energy Laboratory facilities. The alternative energy indoor/outdoor laboratory facility includes six 195 Watt photovoltaic panels, a 30,000 Btu/clear day flat-plate solar collectors, a Thermomax evacuated tubes solar collector, as well as a full scale 1 kW wind turbine, whose scale allows for useful power and heat to be provided to the engineering building. This facility will be fully instrumented for the collection of key performance data and allows for large scale demonstration of alternative energy systems to students. Additionally, the improved Alternative Energy Active Learning Platform, which uses wind and solar energy to power an electrolyzer, which disassociates water into hydrogen and oxygen, and then subsequently uses the hydrogen and oxygen produced within a fuel cell to power a fan, has been automated to allow better visualization of each system in operation and more efficient data collection. This paper describes the development, operation and capabilities of both the new indoor/outdoor Alternative Energy Laboratory facilities, and the improved Alternative Energy Active Learning Platform, and their utilization within the Green Concentration of the undergraduate mechanical engineering program.

Commentary by Dr. Valentin Fuster
2010;():103-111. doi:10.1115/ES2010-90434.

Arizona recently dedicated its first utility-scale wind plant, the 63-MW Dry Lake Wind Project on private, state and BLM land near Holbrook. While Arizona has developable wind resources and some available transmission capacity, wind power development has not taken off in the state, and this is often attributed to policy issues and resource quality. The National Renewable Energy Laboratory’s Western Wind & Solar Integration Study quantified the wind capacity that should be built in Arizona under various wind development scenarios, including all-in-state development, least-cost wind resource across the western electric grid in the inter-mountain west, and a scenario providing some accounting for local economic impacts of wind development. In scenarios in which up to 20% of Arizona’s electrical energy was served by wind resources developed within Arizona, the study found that instate wind development actually resulted in a lower overall system operating cost of energy to state consumers than any other scenario (despite higher capacity factor sites being available outside of Arizona). In addition, the economic impacts of this potential development offer revitalization to many of the rural areas in the state. However, the state lacks coherent policies to attract wind power development and to bolster the services available in rural areas to meet the needs of developers during construction and operation of wind power plants. This study presents and evaluates policy mechanisms for use by the state, county, or tribal governments to increase wind penetration, attract wind development through financial incentives, and increase the local economic impacts of the development once it takes place. Example policies from other states, counties, and tribal governments are evaluated with regard to their appropriateness in Arizona, and suggestions are made for changes to federal policy that would increase the viability and impact of wind development projects on tribal land nationwide.

Topics: Wind
Commentary by Dr. Valentin Fuster
2010;():113-119. doi:10.1115/ES2010-90508.

The Energy Conservation Act 2001 was the first major initiative in India to channelize and catalyze energy efficiency improvement in various sectors of economy. The Bureau of Energy Efficiency was set up per the provision of this act, which in 2007 brought out Energy Conservation Building Code (ECBC) with an overall purpose of providing minimum requirements for the energy efficient design and construction of buildings. ECBC covers building envelope, heating, ventilation and air-conditioning system, interior and exterior lighting system, service hot water, electrical power and motors. Since the launch of this code in May 2007, efforts are being made to promote and facilitate the adoption of this code through several training and capacity building programs. A program committee has been set to take care of the comments from stakeholders and inconsistencies, due to which revision of the code was brought out in May 2008. Currently the code is voluntary in the initial phase, but it is designed to be mandatory in future. One major feature of the code is that implementation is left under the scope of State and local governments. During the capacity building effort, a need was felt to provide additional guidance to design and construction professionals on the rationale behind the ECBC specifications and provide explanations to the key terms and concepts. The ECBC User Guide was therefore developed and released in July 2009 for this purpose. This paper describes the current status, experiences during capacity building and market transformation required for successful implementation of this code. It also covers commentary on how various stakeholders are contributing towards one common goal in different ways. With successful implementation, the code is expected to reduce the energy consumption of the upcoming new buildings by 20–40% from their average performance level at the time of launch of ECBC. Having this huge potential of energy saving, there is an urgent need to address the problems and issues for early adoption of the energy conservation building code in the country.

Commentary by Dr. Valentin Fuster

Climate Control and the Environment

2010;():121-130. doi:10.1115/ES2010-90037.

This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using conventional No. 2 diesel fuel. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform engine combustion simulations. The simulation approach is a predictive combustion simulation, direct-injection jet modeling, which is primarily used to predict the burn rate and NOx emissions. Crank angle dependent fuel injector sac pressure profiles have been measured during combustion tests and used as fuel jet inputs in the combustion modeling to predict injected fuel mass and fuel jet velocity as a function of time. In each emissions test, an in-cylinder pressure profile was measured and used for combustion model calibration to assure a correct burn rate profile was predicted and the exhaust emissions prediction was based on a calibrated burn rate profile which closely resembled the one measured in the test. Engine emissions, which include NOx , HC, CO, and CO2 , measured at various engine speeds and loads were compared to those predicted by the combustion simulations. The maximum differences between simulation-predicted and test-measured emissions data are 30% for the NOx emissions and 68% for the CO2 emissions. However, the results for CO and HC emissions could differ by more than an order of magnitude under the conditions tested. The modeling and testing evaluation of conventional diesel was chosen to provide a comparative baseline analysis that can be extended for predicting combustion emissions of renewable feedstock fuels in development.

Commentary by Dr. Valentin Fuster
2010;():131-140. doi:10.1115/ES2010-90038.

This paper presents emissions modeling and testing of a four-stroke single cylinder diesel engine using pure soybean, cottonseed, and algae biodiesel fuels. A system level engine simulation tool developed by Gamma Technologies, GT-Power, has been used to perform predictive engine combustion simulations using direct-injection jet modeling technique. Various physical and thermodynamic properties of the biodiesel fuels in both liquid and vapor states are required by the GT-Power combustion simulations. However, many of these fuel properties either do not exist or are not available in published literatures. The properties of the individual fatty esters, that comprise a biofuel, determine the overall fuel properties of the biofuel. In this study, fatty acid profiles of the soybean, cottonseed, and algae methylester biodiesel fuels have been identified and used for fuel property calculations. The predicted thermo-physical properties of biodiesels were then provided as fuel property inputs in the biodiesel combustion simulations. Using the calculated biodiesel fuel properties and an assumed fuel injector sac pressure profile, engine emissions of the conventional diesel and biodiesel fuels have been predicted from combustion simulations to investigate emission impacts of the biodiesel fuels. Soybean biodiesel engine emissions, which include NOx, HC, CO and CO2 , measured at various engine speeds and loads in actual combustion emissions tests performed in this study were also compared to those predicted by the combustion simulations.

Commentary by Dr. Valentin Fuster
2010;():141-151. doi:10.1115/ES2010-90315.

The goal of this study is to evaluate the economic and environmental performance of power plants based on integrated gasification combined cycle (IGCC) technology, and to compare it with currently relevant renewable and nuclear power generation options in China, until the year 2020. First, electricity demand is predicted, based on up-to-date policies made by Chinese government organizations. From this, a business as usual (BAU) study, in which coal-fired power plant technology is assumed to be unchanged from 2010 to 2020, is carried out as a reference. Different scenarios of IGCC technology adoption are then studied using a newly developed model, and the result show, for example, that there could be 10.05 billion tons of CO2 emission avoided from 2010 to 2020 if 50% of newly built coal-fired plants are based on IGCC technology with CO2 capture. When compared with other options, the cost of avoided CO2 emissions in this scenario is more expensive than hydroelectric, nuclear, and wind, but cheaper than solar (thermal and photovoltaic). The results also show that IGCC, although more expensive, could still be important in China’s coal-dominated electricity industry.

Commentary by Dr. Valentin Fuster
2010;():153-162. doi:10.1115/ES2010-90346.

In this paper the feasibility of using photovoltaic cells to reduce electricity generation from fossil fuels in North Cyprus (N. Cyprus) was studied. In this work it is proposed to use photovoltaic systems to power heating and cooling systems (i.e., mainly heat pumps) in household units and it was found that this is economically feasible. It was also discovered that despite the extensive use of solar water heaters in N. Cyprus, the awareness of photovoltaic cells is still very low and few house owners take advantage of its economic and environmental friendliness. It was also observed that PV cells are not widely available in the local market; coupled with the fact that formal awareness of energy friendly electricity means is not well promoted in developing countries. The result of this work shows that about 40% of yearly electricity consumption in N. Cyprus, which is mainly generated from plants using fuel oil no. 6, can be reduced if all household units use PV systems to heat or cool the house depending on the weather conditions. According to the electricity forecast carried out in this paper it was observed that the annual net electricity consumption is expected to increase by 30.65% in the year 2015. This means that the utility company will need to augment its current facilities to accommodate the increment; by expanding its facilities or opting for energy conservation policies. The latter has proved to be inefficient in this part of the world; the former will increase the use of fossil fuel thereby increasing the CO2 emission. This work also provides economic analysis for PV systems investment for household owners and policies to help increase availability of PV cells in N. Cyprus market.

Commentary by Dr. Valentin Fuster
2010;():163-169. doi:10.1115/ES2010-90358.

With the rapid development of modern economy in China, the concept of “green building” is paid more attention, and the assessment to green buildings becomes more important than before. In green building assessment systems, the assessment to the environmental quality is one of the most important content. The research to the assessment index systems of environmental quality is of great significance to developing green buildings in China. In this paper, based on the technical requirements and design outlines of green buildings, the assessment rule, object, method and mode that are suitable for the situations in China are discussed by combining the characteristics of indoor and outdoor environment of green buildings, and the assessment index and system of environmental quality are set up. In the process, the evaluation models of AHP (analytic hierarchy process) are established. The weight factor of the indexes of environmental quality are made certain using the method of AHP, which will be the basis of the whole assessment system of green building and the reference for the implement of green building evaluation policy in China. All the work is to promote the development of green buildings.

Commentary by Dr. Valentin Fuster
2010;():171-182. doi:10.1115/ES2010-90376.

We present brief comparative economic and environmental appraisals of the alternatives that have received the most attention in recent years: conventional biofuels (agrofuels), cellulosic ethanol (CE), microalgae, electric vehicles (EVs), plug-in hybrids (PEHVs), compressed natural gas (CNG) vehicles, “semi-clean” (SCPC) coal, clean coal, wood co-firing, nuclear, photovoltaic solar (PV), concentrated solar power (CSP), geothermal, hydropower, wind, and a novel alternative energy solution known as “WindFuels”. Critical reviews of the projections of both Levelized Cost of Energy (LCOE ) and life-cycle CO2 emissions of these primary alternatives for clean, sustainable energy are presented. We identify and review the major challenges faced by these alternatives — many of which have received incomplete treatment in previous studies. Then from the projected LCOE, carbon neutrality, resource availability, technological challenges, and recent market data; the probable growth rates for the various alternatives are projected, and the environmental benefit and economic burdens associated with these alternatives are assessed.

Commentary by Dr. Valentin Fuster

Fuel Cells and Hydrogen Energy Technologies

2010;():183-192. doi:10.1115/ES2010-90125.

A basic concept for a receiver-reactor for solar sulfuric acid decomposition as the key step of thermochemical cycles for hydrogen production has been developed and realized. A prototype reactor has been built and is specialized for the second part of the reaction, the decomposition of sulfur trioxide. For a detailed understanding of the operational behaviour of the developed reactor type a mathematical model was developed. The reactor model was validated using experimental data from the prototype reactor test operation. The present work deals with the optimization of process and design parameters and the evaluation of the achievable performance of the reactor type. Furthermore the reactor model is used for numerical simulations to predict operational points, which are not easy to realize in experiments due to hardware limitations, to save the experimental effort, and to predict the performance of a large-scale reactor on a solar tower. The results of the simulation confirm a central finding of the experiments: Depending on the operation conditions an optimum of reactor efficiency emerges if one parameter is varied. This is in particular true for the absorber temperature. Two oppositional effects compensate each other in a way that the reactor efficiency exhibits a maximum at a certain temperature: by increasing process temperature the reradiation losses increase disproportionately high whereas the chemical conversion decreases when lowering the temperature. Beyond that influences of other operational parameters like feed mass flow, residence time, and initial concentration of the acid were also analyzed. In a scale-up study the reactor was simulated as being part of the aperture area of a large scale tower receiver. The main differences to the prototype system are the diminished gradients of solar flux on the receiver front face and the reduced thermal conduction losses due to the presence of several neighbor modules at comparable temperature level. This leads to higher chemical conversions and better efficiencies. Reactor efficiencies up to 75% are predicted. Even higher efficiencies are possible if re-radiation losses can be decreased, e.g. by considering a cavity design.

Commentary by Dr. Valentin Fuster
2010;():193-199. doi:10.1115/ES2010-90138.

3D dynamic models are developed for polymer electrolyte fuel cells (PEFCs) and hydrogen tanks, respectively. In the fuel cell model, we consider the major transport and electrochemical processes within the key components of a single PEFC that govern fuel cell transient including the electrochemical double-layer behavior, mass/heat transport, liquid water dynamics, and membrane water uptake. As to modeling hydrogen tanks, we consider a LaNi5 -based system and develop a general formula that describes hydrogen absorption/desorption. The model couples the hydride reaction kinetics and mass/heat transport. The dynamic characteristics of the PEFC and hydrogen tank, together with the possible coupling of the two systems, are discussed.

Commentary by Dr. Valentin Fuster
2010;():201-206. doi:10.1115/ES2010-90139.

In this paper, we develop a model to investigate the cold-start operation of polymer electrolyte fuel cell (PEFC). The model describes the electrochemical kinetics, heat/mass transport, and solid water formation in polymer electrolyte fuel cell (PEFC) during cold start. A simplified analysis is developed to investigate the temperature-dependent change of the ohmic voltage loss based on the ionic conductivity of the membrane at subfreezing temperature. 3D numerical simulation is also conducted to study the dynamics of the solid water during cold start and the distributions of ice volume fraction and current density. This study is valuable for improving the characteristics of PEFC cold-start.

Commentary by Dr. Valentin Fuster
2010;():207-211. doi:10.1115/ES2010-90140.

In this paper, we propose a relatively new fabrication technique for micro proton exchange membrane fuel cell (μPEMFC) fabrication. Microgrooves are fabricated on the polymer Circlex plate first which is relatively easy to manufacture comparing with directly patterning on carbon, cheap, and mechanically robust (in contrast to graphite). By carbonizing the machined polymer at high temperature, the bipolar plates are produced for a μPEMFC assembly to distribute the reactants via its micro groove structure. A μPEMFC with 0.64 cm2 active surface is fabricated. A maximum power of ∼70 mW/cm2 is achieved for 1 atm at 25 °C, which is comparable with most of data reported in the literature. The Electrochemical Impedance Spectroscopy (EIS) and performance test are conducted on fuel cell steady-state operation.

Commentary by Dr. Valentin Fuster
2010;():213-223. doi:10.1115/ES2010-90149.

The macro level model of a solid oxide fuel cell (SOFC) system was developed considering fundamental equations of thermodynamics, chemical reactions, and electrochemistry. The SOFC model was implemented in a hybrid SOFC-gas turbine (GT) cycle model using Aspen Plus® to simulate two configurations, system with and without anode recirculation. In order to monitor the performance of the system, parameters such as SOFC and system thermal efficiency; SOFC, GT, and cycle net and specific work; as well as air to fuel ratio, and air and fuel mass flow rate were investigated. The results of simulation for different types of fuel, namely, pure methane, natural gas, coal syngas, different types of biomass syngas, and farm and sewage biogas showed that system output and operation parameters were greatly influenced by changes in the fuel composition. Therefore, in feasibility study of a SOFC-GT hybrid cycle fueled by biogas, gasified biomass, and syngas, it is vital that possibility of variation of inlet fuel composition and its impacts on system performance to be considered and investigated.

Commentary by Dr. Valentin Fuster
2010;():225-232. doi:10.1115/ES2010-90215.

In this work, a biogas fuelled power generation system is considered. The system is constituted by a molten carbonate fuel cell (MCFC) coupled with a micro gas turbine for electricity generation and supplying heat to an anaerobic digester which produces biogas from urban wastes. The work starts with a time dependent model of the digester, obtained from measured data, relating the waste characteristics with the biogas mass flow rate. The thermal flux required by the digester is also related to the waste disposal. The optimal design of the MCFC system is then investigated considering both thermodynamic and economic objective functions, calculated in a proper design condition. The effects of variation in fuel quality, ambient temperature and component performances are finally analyzed.

Commentary by Dr. Valentin Fuster
2010;():233-240. doi:10.1115/ES2010-90252.

The present study proposes a combination of solar-powered components (two heaters, an evaporator, and a steam-reformer) with a Proton Exchange Membrane fuel cell to form a powerplant that converts methanol to electricity. The solar radiation heats up the mass flows of methanol-water mixture and air and sustains the endothermic methanol steam-reformer at a sufficient reaction temperature (typically between 220 and 300°C). In order to compare the different types of energy (thermal, chemical, and electrical), an exergetic analysis is applied to the entire system, considering only the useful part of energy that can be converted to work. The effect of the solar radiation intensity and of different operational and geometrical parameters like the total inlet flow rate of methanol-water mixture and the size of the fuel cell on the performance of the entire system is investigated. The results of the exergetic analysis prove that the proposed solar methanol fuel cell system has the potential to be operated with a high efficiency and power density by combining methanol steam-reforming and a PEM fuel cell with solar-powered heating. The chemical exergetic efficiency can be increased by a factor of around 1.6 (e.g. from 36% to 60% for the 1000 W m−2 incoming solar heat flux) by using solar radiation as a heat source instead of any other source (e.g. by burning a chemical fuel). This enhancement of effective exergetic efficiency by using solar power for heating the system amounts to even much higher values of up to above 10 for lower solar heat fluxes and very low flow rates of inlet fuel. The effective exergetic efficiency for the herein presented solar-powered system is significantly higher than any non-solar fuel cell system fed by hydrocarbon or alcoholic fuels. At the same time, an electrical power density per irradiated area of more than 986 W m−2 is obtained for a solar heat flux of 1000 W m−2 . Comparable photovoltaic systems would need excessive sunlight-to-electricity efficiencies of more than 98%. Even for decreased intensities of solar radiation as low as 300 W m−2 , the system achieves very satisfactory results regarding the solar power density (89.3 W m−2 ) and the chemical exergetic efficiency (61%). Therefore, the combination of exergy input in form of chemical fuel and solar radiation can be promising to achieve both, a high exergetic efficiency and a high power density per area irradiated by sunlight.

Commentary by Dr. Valentin Fuster
2010;():241-254. doi:10.1115/ES2010-90323.

This paper presents a thermo-economic assessment of three different hydrogen production processes using fossil fuels as feedstock. First, the paper provides process-step level energy and cost analysis for the solar reforming of natural gas. The same analysis is given for the solar cracking of natural gas. The results are compared with the thermo-economic process-step analysis of the steam reforming process. Based on the benchmark results, the paper discusses these three processes with respect to their economic viability. The data for the analysis is collected from literature, various vendors, and personal communications with people from industry and universities. The results are presented for unit hydrogen production by each technique and compared with the market price for hydrogen. An energy balance around each process-step is made to reveal the energy intensity of each process. Although the results show that the steam reforming of methane is still the most economical pathway for hydrogen production, it is only valid when the sequestration, storage, and transportation of hazardous emissions are not taken into account. Finally, this paper provides some ideas for the improvement of the most environmentally friendly hydrogen production technique; the solar cracking of natural gas.

Commentary by Dr. Valentin Fuster
2010;():255-263. doi:10.1115/ES2010-90324.

In this work, we present a thorough reaction engineering analysis on the modeling of a vortex-flow reactor to show that commonly practiced one-plug reactor approach is not sufficient to explain the flow behavior inside the reactor. Our study shows that N-plug flow reactors in series is the best approach in predicting the flow dynamics based on the computational fluid dynamics (CFD) simulations. We have studied the residence time distribution using CFD by two different methods. The residence time distribution characteristics are calculated by approximating the real reactor as N-ideal reactors in series, and then estimated the number of ideal reactors in series for the model. We have validated our CFD model by comparing the simulation results with experimental results. Finally, we have done a parametric study with a different sweeping gas to identify the best screening gas to avoid carbon deposition inside the vortex-flow reactor. Our results have shown that hydrogen is a better screening gas than argon.

Commentary by Dr. Valentin Fuster
2010;():265-272. doi:10.1115/ES2010-90341.

COP15, Copenhagen, December 09, failed partly for lack of a credible, comprehensive vision for how we may, and must soon, “run the world on renewables”. We cannot, and should not try to, accomplish this entirely with electricity transmission. The world’s richest renewable energy (RE) resources — of large geographic extent and high intensity — are stranded: far from end-users with inadequate or nonexistent gathering and transmission systems to deliver the energy. Electricity energy storage cannot affordably firm large, intermittent renewables at annual scale, while gaseous hydrogen (GH2) and anhydrous ammonia (NH3 ) fuels can: GH2 in large solution-mined salt caverns, NH3 in surface tanks, interconnected via underground pipelines in RE systems for gathering, transmission, distribution, and end use. Thus, we need to think beyond electricity as we plan new “transmission” systems for bringing large, stranded RE resources to distant markets as annually-firm C-free energy, to empower subsequent efforts to COP15. Recent press has extolled the global RE vision, but without adequate attention to the diverse transmission and storage systems required for achievement. [21] At GW scale, renewable-source electricity from diverse sources can be converted to hydrogen and byproduct oxygen, and/or to NH3 , pipelined underground to load centers for use as vehicle fuel and combined-heat-and-power generation on the wholesale or retail side of the customers’ meters. The ICE, CT, and fuel cell operate very efficiently on GH2 and NH3 fuels. USA has extensive extant NH3 pipeline and tank storage infrastructure.

Commentary by Dr. Valentin Fuster

Energy Systems: Design, Integration, Implementation

2010;():273-277. doi:10.1115/ES2010-90012.

Everyone with green ambitions wants to see a full fleet of 100 percent renewable energy sources drive the world’s electric power grids. Until that happens, the next best solution integrates renewable energy generators with existing gas-fired power plants to improve their warmer-weather efficiency when generating on their larger scale by using methods of energy storage and distribution. Relatively clean burning on their own, large gas turbine generators are examples of proven opportunities to gain significant efficiency and recover output by using stored thermal energy to cool their inlet air when called to operate during hotter seasons of the year. Sustainable energy sources like wind and solar, which today generate in peaks and troughs that are hard to manage on electric power grids, beckon to be put into service for thermal energy storage instead of direct on-line grid interconnection. This article steps through the implementation of such storage.

Commentary by Dr. Valentin Fuster
2010;():279-284. doi:10.1115/ES2010-90041.

Many natural gas well sites produce significant quantities of oil as a byproduct of gas production. Producers use standard gas separation techniques to recover gas dissolved in the oil, but additional light hydrocarbons are released during final depressurization and storage of the oil at atmospheric pressure. Gas produced in oil storage is often contaminated with air, cannot be introduced into midstream pipelines, and is flared at the well site. The flare gas represents a significant energy resource that could be utilized to improve overall site efficiency. This work documents a comprehensive energy analysis performed on a non-electrified site in Colorado. Data collection and simulations demonstrated that energy available in flare gas is sufficient to support the major energy loads at the well site. However, due to low flare gas pressures, high and variable air contamination, and temporal misalignment between the gas availability and energy needs, on-site utilization requires modified engine technology and application of energy buffering. Simulation results are presented, along with conceptual designs for well site modifications.

Commentary by Dr. Valentin Fuster
2010;():285-294. doi:10.1115/ES2010-90094.

This paper details the calculation of the environmental loads associated with the construction of each piece of equipment (considering that the materials were not reused at the end of the equipment’s lifetime, which is the worst case scenario) and operation of a trigeneration system. The purpose of a trigeneration system is to meet the demands of a consumer center — in this case, a medium-sized hospital located in Zaragoza, Spain. The evaluation extended over a period of one year, considering previously specified energy service demands (electricity, heat - sanitary hot water and heating -, and cooling). The system interacted with the economic environment (market) through the purchase of natural gas and electricity from the grid, and also through the sale of autogenerated electricity to the grid, according to Spanish regulations. Therefore, the environmental loads regarding the operation of the system were associated with the consumption of natural gas and electricity purchased/sold from/to the grid. Technical information on each piece of equipment was obtained from catalogs and from consultation with manufacturers. Regarding natural gas, special care was taken to correctly identify the natural gas supplied to a user in Spain (it was considered that the gas comes from Algeria, transported in Liquefied Natural Gas (LNG) carriers, including pipeline transportation to the user and controlled burning). The electricity supplied by the Spanish electric grid was also properly specified and characterized. The environmental loads were calculated utilizing SimaPro, a specialized Life Cycle Assessment tool, and then incorporated into a linear programming model, solved by LINGO optimization software. Environmental criteria were used to obtain the optimal configuration and operation of the system simultaneously.

Topics: Stress
Commentary by Dr. Valentin Fuster
2010;():295-306. doi:10.1115/ES2010-90116.

What does remain a growing concern for many users of Data Centers is their continuing availability following the explosive growth of internet services in recent years, The recent maximizing of Data Center IT virtualization investments has resulted in improving the consolidation of prior (under utilized) server and cabling resources resulting in higher overall facility utilization and IT capacity. It has also resulted in excessive levels of equipment heat release, e.g. high energy (i.e. blade type) servers and telecommunication equipment, that challenge central and distributed air conditioning systems delivering air via raised floor or overhead to rack mounted servers arranged in alternate facing cold and hot isles (in some cases reaching 30 kW/rack or 300 W/ft2 ) and returning via end of isle or separated room CRAC units, which are often found to fight each other, contributing to excessive energy use. Under those circumstances, hybrid, indirect liquid cooling facilities are often required to augment above referenced air conditioning systems in order to prevent overheating and degradation of mission critical IT equipment to maintain rack mounted subject rack mounted server equipment to continue to operate available within ASHRAE TC 9.9 prescribed task psychometric limits and IT manufacturers specifications, beyond which their operational reliability cannot be assured. Recent interest in new web-based software and secure cloud computing is expected to further accelerate the growth of Data Centers which according to a recent study, the estimated number of U.S. Data Centers in 2006 consumed approximately 61 billion kWh of electricity. Computer servers and supporting power infrastructure for the Internet are estimated to represent 1.5% of all electricity generated which along with aggregated IT and communications, including PC’s in current use have also been estimated to emit 2% of global carbon emissions. Therefore the projected eco-footprint of Data Centers into the future has now become a matter of growing concern. Accordingly our paper will focus on how best to improve the energy utilization of fossil fuels that are used to power Data Centers, the energy efficiency of related auxiliary cooling and power infrastructures, so as to reduce their eco-footprint and GHG emissions to sustainable levels as soon as possible. To this end, we plan to demonstrate significant comparative savings in annual energy use and reduction in associated annual GHG emissions by employing a on-site cogeneration system (in lieu of current reliance on remote electric power generation systems), introducing use of energy efficient outside air (OSA) desiccant assisted pre-conditioners to maintain either Class1, Class 2 and NEBS indoor air dew-points, as needed, when operated with modified existing (sensible only cooling and distributed air conditioning and chiller systems) thereby eliminating need for CRAC integral unit humidity controls while achieving a estimated 60 to 80% (virtualized) reduction in the number servers within a existing (hypothetical post-consolidation) 3.5 MW demand Data Center located in southeastern (and/or southern) U.S., coastal Puerto Rico, or Brazil characterized by three (3) representative microclimates ranging from moderate to high seasonal outside air (OSA) coincident design humidity and temperature.

Commentary by Dr. Valentin Fuster
2010;():307-314. doi:10.1115/ES2010-90123.

The supersonic steam ejector is widely used in many industries which are steam powered such as oil, thermoelectric, refrigeration and so on. Many scholars analyzed the steam ejector by using ideal gas model and they ignored phase change, this may bring some errors for the flowing field of the ejector. In this study, the supersonic steam ejector was simulated using CFD (Computational Fluid Dynamics). Flowing field of the ejector was analyzed by using different state equations. The results shows that performance of the ejector was underestimated under the ideal gas model, and the entrainment ratio is 20%–40% lower than using real gas model. When phase changing was considered under real gas state equations, influences of working fluid pressure and back pressure were investigated. The results illustrates that working critical pressure and back flow critical pressure exist in the flow, and the entrainment ratio reaches its peak at working critical pressure. The performance of the ejector was almost the same when the outlet pressure was lower than critical back pressure. Effects of ejector geometries were also investigated in this paper. It shows that there are optimums of the relative position of the steam nozzle and the taper of the mixing section, length of mixing chamber and diameter of throat according to mass flow rate of second fluid. There are also critical length of diffuser and throat. Mass flow rate stayed the same when the length of diffuser or throat grows. This paper will provide a theoretical basis for ejector’s energy-saving and geometry optimization.

Commentary by Dr. Valentin Fuster
2010;():315-321. doi:10.1115/ES2010-90127.

This paper designed several dual-fuel nozzle structures for the chemically recuperated gas turbine (CRGT) combustor and then the numerical simulation in regard to the combustion flow fields of the combustors with these nozzle structures was carried out with the aid of CFD method and finally the contrastive analysis was made. Realizable k-ε turbulence model, PDF combustion model and the SIMPLE algorithm method were applied in the numerical simulation. According to the contrast of these nozzle structure models’ flame length, position of the high temperature zone, wall temperature and the evenness of exit temperature field as the key influencing factors of the combustor, we could know that the gas swirling dual-fuel nozzle with oblique holes, on the one hand, can produce preswirl flow in the gas channel to enable a better mixing of the pyrolysis gas and air; on the other hand, can protect the nozzle and the wall of flame tube from fire and keep the exit temperature in a moderate level.

Commentary by Dr. Valentin Fuster
2010;():323-329. doi:10.1115/ES2010-90135.

Building energy consumption analysis is a difficult task because it depends on the characteristics and interaction among the building, the heating/cooling system, and the surroundings (weather). Since building energy profiles are usually required on an hourly basis, which often is not available for existing buildings, the hourly energy consumption must be estimated or predicted. The dynamic behavior of the weather conditions and building operation makes computer simulations a good practice for reliable solutions. However, energy building computer simulations require considerable amount of detailed input data and user time, which is a drawback for a cost-effective solution. Therefore, simplified models based on statistics or a combination of statistics and simulations may be a better solution with reasonable uncertainty. This paper presents the tool Small Office Hourly Energy Consumption Estimator (SOHECE). The tool estimates hourly building energy consumption for small office buildings. The proposed tool has been developed in Microsoft Excel and it uses simulation data from EnergyPlus benchmark models to convert monthly energy consumption from utility bills into hourly energy consumption. Since benchmark models were developed by the U.S. government to provide a consistent baseline of comparison, energy consumption data from simulations of the benchmark models are considered reasonable representations of energy consumption profiles. Results account for baseline and variable energy consumption for electricity and fuel. The site weather conditions, for which the energy consumption is estimated, are considered using the sixteen climate zones of the U.S. benchmark models. The tool has been applied to a hypothetical building placed in Meridian, MS, and errors obtained for the estimated hourly energy consumption are mainly lower than ten percent.

Commentary by Dr. Valentin Fuster
2010;():331-338. doi:10.1115/ES2010-90159.

In Turkey, “Thermal Insulation Requirements for Buildings” was implemented to provide energy saving in buildings in 2000. After this, more then seven hundred thousand new buildings are constructed. Determining the correct material and optimum insulation thickness are very important issues in these buildings for thermal insulation. Calculations using monthly outdoor temperatures and solar radiation are done for XPS insulation material and 4 different climatic regions in Turkey. Natural gas, the most preferred in our country is selected as fuel. P1 -P2 method is used to obtain energy saving and payback period. New correlations are specified to determine optimum insulation thickness depending on building heat gains and areas. Furthermore, buildings are categorized into three building class according to external wall area and floor/roof area. Effect of change in building external wall area, floor or roof area, window area to payback period, energy saving and optimum thickness are investigated. As a result, effect of architectural design is determined on thermal insulation. All calculation results are shown in a table for four different climatic regions and three different types of buildings which have the same gross volume.

Commentary by Dr. Valentin Fuster
2010;():339-348. doi:10.1115/ES2010-90213.

Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design point and inefficiently. This work analyzes the revamping options of an existing upstream gas facility, which is chosen because representative of a wide set of plants. A flexible numerical model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, includes the performance maps of all turbo machineries and the main characteristics of the investigated modifications in order to run simulation for many gas input conditions and to predict the performance over a year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to that calculated with state-of-the-art technologies. In addition, an exergy and an environmental analyses are executed.

Commentary by Dr. Valentin Fuster
2010;():349-355. doi:10.1115/ES2010-90221.

District Heating is an efficient way to provide heat to residential, tertiary and industrial users. Heat is often produced by CPH plants, usually designed to provide the base thermal load (40–50% if the maximum load) while the rest is provided by boilers. This choice is made on the basis of economic criteria, in fact the investment cost of a CHP plant is much higher than the cost of boiler, thus its use is convenient when it operates for a large number of hours. The use of storage tanks would permit to increase the annual operating hours of CHP: heat can be produced when the request is low (for instance during the night), stored and then used when the request is high. The use of boilers results partially reduced, thus the thermal load diagram is flattered. Depending on the type of CHP plant this may also affect the electricity generation. All these considerations are crucial in the free electricity market. In this paper, the use of storage systems connected to the district heating systems, is examined. A thermo fluid dynamic model of the tanks is considered in order to calculate the amount of energy actually provided, taking the real operating conditions into account. These considerations are applied to the Turin district heating system, in order to determine the impact of storage systems on the primary energy consumption required to supply heat to the users over the entire heating season.

Commentary by Dr. Valentin Fuster
2010;():357-362. doi:10.1115/ES2010-90330.

Since the regeneration step in the Temperature Swing Adsorption (TSA) process requires time enough to heat and cool the bed, it is often the time-limiting step in the TSA cycle and it consumes a huge amount of energy for regeneration. Therefore, a valid management of the regeneration process can minimize the energy consumption of the TSA process which is involved with regeneration time, purge gas requirements, and heat load. Simulation software was developed for industrial scale bed of TSA. A new isotherm equation which performs well in predicting experiment data was extended to multi-component form and then used to interpret the adsorption equilibria of water vapor and carbon dioxide on adsorbents. Preliminary linear drive force mass transfer coefficients and the heat transfer coefficients were calculated by empirical equations and then refined by matching breakthrough curves obtained from industrial field process monitoring to theoretical curves. Under a wide range of regeneration conditions, the temperature effluence and breakthrough were drawn and studied. With the application of this simulation software, the performance and operation data of the TSA beds under various conditions can be obtained conveniently. This enables the manager to minimize their TSA’s heat consumption.

Commentary by Dr. Valentin Fuster
2010;():363-370. doi:10.1115/ES2010-90347.

Nowadays the residential central air conditioning systems are being widely used in China, and there are several different system options in the actual applications. Different residential central air conditioning systems will have different initial costs and operating costs. It is quite important for the decision-makers to choose an economical air conditioning system. In this paper six residential central air conditioning systems are introduced, which are the air-source heat pump system, household gas-fired air conditioning system, air-cooled chiller unit/gas-fired boiler system, water loop heat pump system, ground-source heat pump system and solar heat pump system. By using the method of dynamic total annual cost with an example of residential building in Beijing, the total annual costs of chosen six air conditioning systems are calculated and compared, and the sensitivity of total annual cost are analyzed with the rates of electricity and natural gas being used as the sensitive factors. The results show that the total annual cost of water loop heat pump system is the minimum among the six systems, which is the optimal option under the given conditions. The rates of electricity and natural gas will influence the raking of systems.

Commentary by Dr. Valentin Fuster
2010;():371-383. doi:10.1115/ES2010-90360.

In this paper, the new approach of Constructal theory has been employed to design shell and tube heat exchangers. Constructal theory is a new method for optimal design in engineering applications. The purpose of this paper is optimization of shell and tube heat exchangers by reduction of total cost of the exchanger using the constructal theory. The total cost of the heat exchanger is the sum of operational costs and capital costs. The overall heat transfer coefficient of the shell and tube heat exchanger is increased by the use of constructal theory. Therefore, the capital cost required for making the heat transfer surface is reduced. Moreover, the operational energy costs involving pumping in order to overcome frictional pressure loss are minimized in this method. Genetic algorithm is used to optimize the objective function which is a mathematical model for the cost of the shell and tube heat exchanger and is based on constructal theory. The results of this research represent more than 50% reduction in costs of the heat exchanger.

Commentary by Dr. Valentin Fuster
2010;():385-390. doi:10.1115/ES2010-90361.

The energy consumption of AC (air conditioning) systems in large buildings is normally higher than the energy consumption in smaller buildings, and its indoor air flow field is also more complex than that in small building. To study the air flow mode and the indoor air flow fields in large spaces is of great significance to the energy conservation of AC systems and thermal comfort of the occupants. This paper presents an example using a large building that uses stratified air conditioning delivered through the linear slot sidewall diffusers and perforated sidewall diffusers. Using CFD simulation methods, three air flow field situations were simulated: (1) total air volume supplied from linear slot diffusers located in the middle of a side wall, (2) 50% flow through the linear slot diffusers the remainder supplied through the perforated sidewall diffusers, (3) 30% of the volume supplied with linear slot diffusers, 70% supplied through the perforated sidewall diffusers. The simulated results show that the third airflow mode is the optimal one for the three modes, which is good for achieving energy conservation and a comfortable building thermal environment in buildings with large spacial areas.

Commentary by Dr. Valentin Fuster
2010;():391-396. doi:10.1115/ES2010-90369.

The study of “Heat Balance ” in a domestic pressure cooker is an important investigation for energy conservation. In the present study, experiments were conducted on a domestic pressure cooker to measure Input Heat, Utilized Heat and Heat Lost for different volumes of water filled in a pressure cooker. Experiments were conducted on 0.008m3 (8litre) pressure cooker filled with water at 12.5%, 25%, 37.5% and 46.25% of its capacity, respectively 1.0kg, 2.0kg, 3.0kg and 3.7kg of water. Two approaches were adopted to determine an optimum condition of the pressure cooker. In first approach, the pressure cooker was insulated and the other in non-insulated. In both cases, cookers of similar capacity, make and design were used. Outer surface of the cooker was insulated with asbestosrope, clay and cow-dung bindings. Interesting results were arrived during the study that, there was not having much difference in heat input, heat utilization for insulated and non insulated cookers when the water level was only about 12.5% volume. In other cases the insulated cooker consumes more heat input than the non-insulated cooker. The reason was found that thermal mass capacity of the insulated cooker was more and stores heat energy. When the pressure cooker is filled with 46.25% of its volume by water, it utilizes a maximum of 30% of total heat supplied. On reducing the volume of water filled in the cooker, the heat loss increased and consumes more thermal energy.

Topics: Pressure , Heat
Commentary by Dr. Valentin Fuster
2010;():397-404. doi:10.1115/ES2010-90389.

Experience has shown that buildings on average may consume 20% more energy than required for occupant comfort which by one estimate leads to $18 billion wasted annually on energy costs in commercial buildings in the United States. Experience and large scale studies of the benefits of commissioning have shown the effectiveness of these services in improving the energy efficiency of commercial buildings. While commissioning services do help reduce energy consumption and improve performance of buildings, the benefits of the commissioning tend to degrade over time. In order to prolong the benefits of commissioning, a prototype fault detection and diagnostic (FDD) tool intended to aid in reducing excess energy consumption known as an Automated Building Commissioning Analysis Tool (ABCAT) has been developed. ABCAT is a first principles based whole building level top down FDD tool which does not require the level of expertise and money often associated with more detailed component level methods. The model based ABCAT tool uses the ASHRAE Simplified Energy Analysis Procedure (SEAP) which requires a smaller number of inputs than more sophisticated simulation methods such as EnergyPlus or DOE-2. ABCAT utilizes a calibrated mathematical model, white box method, to predict energy consumption for given weather conditions. A detailed description of the methodology is presented along with test application results from more than 20 building years worth of retrospective applications and greater than five building years worth of live test case applications. In this testing, the ABCAT tool was used to successfully identify 24 significant energy consumption deviations in five retrospective applications and five significant energy consumption deviations in four live applications.

Commentary by Dr. Valentin Fuster
2010;():405-409. doi:10.1115/ES2010-90391.

Synthetic refrigerants such as CFCs and HCFCs deplete ozone and cause greenhouse effect. CO2 as a natural working fluid has zero Ozone Depletion Potential and its Global Warming Potential is equal to 1, is receiving more and more attention in the refrigeration field. Because the critical temperature of CO2 is only 31.1°c, the trans-critical cycle can be used to improve the coefficient of performance of the system. The thermodynamic analysis and experimental investigation on trans-critical carbon dioxide heat pump system are carried out in this paper. It points out that there is an optimum operational pressure on trans-critical carbon dioxide heat pump cycle, when the outlet temperature of gas cooler is constant, the coefficient of performance increases with increasing evaporating temperature at the same conditions, and the operational efficiency increased with decrease of gas cooler exit temperature. So in order to obtain the optimum performance, the influence of evaporating temperature, gas cooler exit temperature, and the operational pressure should be considered during the designing and operating transcritical carbon dioxide heat pump system.

Commentary by Dr. Valentin Fuster
2010;():411-419. doi:10.1115/ES2010-90472.

Thermal storage systems were originally designed to shift on-peak cooling production to off-peak cooling production to reduce on-peak electricity demand. Recently, however, the reduction of both on- and off-peak demands is becoming an exceedingly important issue. Reduction of on- and off-peak demands can also extend the life span and defer or eliminate the replacement of power transformers due to potential shortage of building power capacity caused by anticipated equipment load increases. Next day daily average electricity demand is a critical set point to operate chillers and associated pumps at the appropriate time. For this paper, a mathematical analysis of the annual daily average cooling of a building was conducted, and three real-time building load forecasting models were developed: a first-order autoregressive model, a random walk model, and a linear regression model. A comparison of results shows that the random walk model provides the best forecast. A complete control algorithm integrated with forecast model for a chiller plant including chillers, thermal storage system and pumping systems was developed to verify the feasibility of applying this algorithm in the building automation system. Application results are introduced in this paper as well.

Commentary by Dr. Valentin Fuster
2010;():421-429. doi:10.1115/ES2010-90480.

Rising energy costs and the desire to reduce energy consumption dictates a need for significantly improved building energy performance. Three technologies that have potential to save energy and improve sustainability of buildings are dedicated outdoor air systems (DOAS), radiant heating and cooling systems and tighter building envelopes. Although individually applying innovative technologies may incrementally improve building energy performance, more significant payoffs are realized when compatible technologies are integrated into an optimized system. Fortunately, DOAS, radiant heating and cooling systems and improved building envelopes are highly compatible. To investigate the energy savings potential of these three technologies, whole building energy simulations were performed for a barracks facility and an administration facility in 15 U.S. climate zones and 16 international locations. The baseline facilities were assumed to be existing buildings with VAV HVAC systems (admin facilities) and packaged HVAC systems (barracks facilities). The energy simulations were adjusted for each location for optimal energy and humidity control performance. The results show that the upgraded facilities realized total building energy savings between 20% and 40% and improved humidity control when compared to baseline building performance.

Commentary by Dr. Valentin Fuster
2010;():431-437. doi:10.1115/ES2010-90486.

In this paper, an experimental assessment and thermal performance of a prototype ammonia-water absorption heat pump are carried out. The experimentations are conducted for different operating conditions such as: filling up concentration (40 and 47%), inlet brine temperature (-5, +5 and +15 °C) and inlet cooling water temperature (20 [25], 30 and 40 °C). The effects of performance parameters like refrigerant vapor concentration leaving rectifier, mass fraction spread and specific solution circulation ratio are also investigated. The results are divided into two categories. The first one is an external analysis of the absorption system considering thermal loads and system performance. However, the second one represents the internal analysis of the heat pump taking into account the temperature glide and degree of subcooling. Little effect is found for the filling up concentration on the thermal loads for different heat pump components as well as the heating capacity and the coefficient of performance. The refrigerant vapor concentration of the refrigerant vapor should not be less than 0.999 to avoid the effect of temperature glides on the system performance. Temperatures of the cooling water, brine and generator all have large effects on the system performance as any sorption system. Inaccurate expansion valve control leads to lower heating COP. Controlling the mass fraction spread or the specific circulation ratio affects considerably thermal loads of different absorption system components. The control of these two parameters can be accomplished by controlling the solution pump and flow rates in the solution loops.

Commentary by Dr. Valentin Fuster
2010;():439-445. doi:10.1115/ES2010-90490.

This work involves measurements, analyses, and evaluations of the performance of add-on, Heat Pump Water Heater (HPWH) systems in residential and small commercial applications. Two air-source Heat Pump (HP) systems rated at 7,000- and 12,000-BTU (2.051- and 3.517-kWh), were utilized in this work. The two HPs were retrofitted to two 50-gallon (189.3 liters) electric-resistance storage water-heaters with their electric heating elements removed. A third, standard electric water-heater (EWH), was used for comparison. The testing set-up was fully instrumented for measurements of pertinent parameters, including inlet and outlet water temperatures, inlet and outlet air temperatures of the HPs, temperature and humidity of the air in the surrounding space, volume of water draws out of the storage heater tanks, as well as electric energy consumptions of the systems. Several performance measures were used in this work, including the Coefficient of Performance (COP), which is a measure of the instantaneous energy output in comparison with the energy input; Energy Factor (EF), which is an average measure of the COP taken over extended periods of time; and the First Hour Rating (FHR), which is a measure of the maximum volume of hot water that a storage type water-heater can supply to a residence within an hour. The results obtained clearly indicate that, HPWH systems are much more efficient as compared to standard EWHs. While the average value of the EF for a standard EWH is close to 1.0, the HPWH systems yield EFs averaging more than 2.00, resulting in annual energy savings averaging more than 50%. The results also showed that, HPWH systems are effective at reducing utility peak demand-loads, in addition to providing substantial cost savings to consumers.

Topics: Stress , Heat pumps , Water
Commentary by Dr. Valentin Fuster

Renewable and Alternative Energy Technologies

2010;():447-450. doi:10.1115/ES2010-90006.

This paper explores and challenges the underlying basis of the Second Law of Thermodynamics. The second law of thermodynamics and its related equations define the relationship between thermal energy and its conversion into mechanical work. The second law of thermodynamics and its equations are based on theory developed by analysis of the Carnot cycle, then with a leap of faith, applies this theory and these equations to the Rankine cycle and to the general conversion of thermal energy into mechanical energy. This paper explores the original analysis, which forms the basis of the second law of thermodynamics, and offers new analysis which may form a new understanding of thermodynamics. If proven correct, this new understanding may unlock tremendous resources for the production of mechanical and electrical energy.

Commentary by Dr. Valentin Fuster
2010;():451-455. doi:10.1115/ES2010-90015.

An analytical model and a thermodynamics study of the steady airflow inside a solar chimney are performed in this paper. A simplified Bernoulli equation combined with fluid dynamics and ideal gas equation are modeled and solved using EES solver to predict the performance of a solar chimney power plant. The analytical model is validated against an experimental and numerical data available in the literature. The developed analytical model is used to evaluate the effect of geometric parameters on the solar plant power generation. The analysis is showing that the height and diameter of the tower are the most important physical variables for the solar chimney design. The collector area has minimal effect on second-law efficiency but strong effect on harvested energy. The second law efficiency has non-monotonic relation with the turbine head.

Commentary by Dr. Valentin Fuster
2010;():457-468. doi:10.1115/ES2010-90067.

The increased use of intermittent renewable power in the United States is forcing utilities to manage increasingly complex supply and demand interactions. This paper evaluates biomass pathways for hydrogen production and how they can be integrated with renewable resources to improve the efficiency, reliability, dispatchability, and cost of other renewable technologies. Two hybrid concepts were analyzed that involve co-production of gaseous hydrogen and electric power from thermochemical biorefineries. Both of the concepts analyzed share the basic idea of combining intermittent wind-generated electricity with a biomass gasification plant. The systems were studied in detail for process feasibility and economic performance. The best performing system was estimated to produce hydrogen at a cost of $1.67/kg. The proposed hybrid systems seek to either fill energy shortfalls by supplying hydrogen to a peaking natural gas turbine or to absorb excess renewable power during low-demand hours. Direct leveling of intermittent renewable electricity production is accomplished with either an indirectly heated biomass gasifier, or a directly heated biomass gasifier. The indirect gasification concepts studied were found to be cost competitive in cases where value is placed on controlling carbon emissions. A carbon tax in the range of $26–40 per metric ton of CO2 equivalent (CO2 e) emission makes the systems studied cost competitive with steam methane reforming (SMR) to produce hydrogen. However, some additional value must be placed on energy peaking or sinking for these plants to be economically viable. The direct gasification concept studied replaces the air separation unit (ASU) with an electrolyzer bank and is unlikely to be cost competitive in the near future. High electrolyzer costs and wind power requirements make the hybridization difficult to justify economically without downsizing the system. Based on a direct replacement of the ASU with electrolyzers, hydrogen can be produced for $0.27 premium per kilogram. Additionally, if a non-renewable, grid-mix electricity is used, the hybrid system is found to be a net CO2 e emitter.

Commentary by Dr. Valentin Fuster
2010;():469-478. doi:10.1115/ES2010-90089.

A supercritical Rankine cycle using zeotropic mixture working fluids for the conversion of low-grade heat into power is proposed and analyzed in this paper. A supercritical Rankine cycle does not go through two-phase region during the heating process. By adopting zeotropic mixtures as the working fluids, the condensation process happens non-isothermally. Both of the features create a potential in reducing the irreversibility and improving the system efficiency. A comparative study between an organic Rankine cycle and the proposed supercritical Rankine cycle shows that the proposed cycle improves the cycle thermal efficiency, exergy efficiency of the heating and the condensation processes, and the system overall efficiency.

Commentary by Dr. Valentin Fuster
2010;():479-484. doi:10.1115/ES2010-90129.

Since many renewable energy technologies use low cost or free primary energy sources such as solar insolation or wind, the capital cost of conversion equipment can become the dominant factor in determining economic feasibility. A natural approach to lowering the capital cost per unit of electricity is to strive for high efficiency equipment, i.e., increase the amount of electricity produced. Another approach is to seek out low cost conversion technologies, i.e., lower the capital cost. Capital equipment costs must be significantly lower than currently available off-the-shelf technologies to make solar power generally attractive economically for small-scale electricity generation. One potential low capital cost energy conversion technology is the liquid piston Stirling engine. A necessary design component for liquid piston Stirling engines is estimation of the frictional losses in the oscillating liquid columns. While frictional losses for fully developed laminar and turbulent pipe flow are characterized quite completely, average frictional loss factors for the continually starting and stopping liquid flow in oscillating columns are less complete. Direct measurements of frictional loss using a log-decrement method are reported in the paper. Measurements were completed for a variety of piping and tubing sizes and configurations. It was found that liquid volume correlated damping coefficient data well. A comparison with an equivalent fully developed laminar flow damping coefficient is presented.

Commentary by Dr. Valentin Fuster
2010;():485-494. doi:10.1115/ES2010-90193.

Recent years have seen a surge of interest in renewable energy sources. Most renewable energy sources are intermittent in their production of power. One solution is to store the energy and draw from that stored energy in a controlled fashion. Recent advances have been made in solar thermal storage that would allow a solar thermal power system to operate year round and around the clock at nearly constant levels of electrical power production. This paper outlines how this can be accomplished.

Commentary by Dr. Valentin Fuster
2010;():495-501. doi:10.1115/ES2010-90195.

As energy usage across the world continues to rise, there is a strong need to develop new methods for energy conservation and power generation, particularly approaches that have less environmental impacts. Although human power is not ideal in terms of life cycle costs [1], there are promising application areas for human power in emerging regions where electric power is either not available or not affordable [2]. There is also untapped potential for harnessing human power at most fitness facilities. This paper focuses on the feasibility of capturing this energy at fitness facilities, particularly the Recreational Sports Facility (RSF) at University of California, Berkeley, which averages over 2,800 patrons per day. In particular, we estimated that patrons using 28 elliptical machines would supply approximately 10,000 kWh into the electric grid over a year. This amounts to only 0.7% of the RSF’s total energy needs, but is valuable nonetheless. An additional benefit in human power generation is its positive social impact. A survey of the RSF users has evinced remarkable enthusiasm for implementing energy generation technology into the facility, both as a power generation tool and as an educational resource. This paper will also address the social benefits of human power generation technology in the gym.

Commentary by Dr. Valentin Fuster
2010;():503-514. doi:10.1115/ES2010-90211.

The objective of this work is to evaluate thermodynamic and economic performance of a small-scale combined cycle plant with microturbine and ORC. The primary source of fuel for the plant is wood. The biomass is converted into a gaseous fuel by means of gasification in a downdraft fixed bed reactor. Size of the plant is limited to 350 kg/h of wet biomass input into the gasifier. Two alternative configurations of the bottoming ORC cycle are taken into account: single stage cycle and cascade cycle. In the first case R123 and n-pentane are analyzed as potential working fluids. In the cascade cycle toluene and n-pentane are selected for top and bottom cycle respectively. Electricity generation efficiency of the proposed small-scale plant is at the level of 23%, that is comparable with direct combustion based systems of much higher electric output. An initial economic evaluation of a sample project gives an outlook on economic effectiveness, that nowadays is strongly dependent on stimulation measures for “green” electricity generation.

Commentary by Dr. Valentin Fuster
2010;():515-522. doi:10.1115/ES2010-90218.

Synthesis gas (Syngas), a mixture of hydrogen and carbon monoxide, can be manufactured from natural gas, coal, petroleum, biomass, and even from organic wastes. It can substitute fossil diesel as an alternative gaseous fuel in compression ignition engines under dual fuel operation route. Experiments were conducted in a single cylinder, constant speed and direct injection diesel engine fuelled with syngas-diesel in dual fuel mode. The engine is designed to develop a power output of 5.2 kW at its rated speed of 1500 rpm under variable loads with inducted syngas fuel having H2 to CO ratio of 1:1 by volume. Diesel fuel as a pilot was injected into the engine in the conventional manner. The diesel engine was run at varying loads of 20, 40, 60, 80 and 100%. The performance of dual fuel engine is assessed by parameters such as thermal efficiency, exhaust gas temperature, diesel replacement rate, gas flow rate, peak cylinder pressure, exhaust O2 and emissions like NOx , CO and HC. Dual fuel operation showed a decrease in brake thermal efficiency from 16.1% to a maximum of 20.92% at 80% load. The maximum diesel substitution by syngas was found 58.77% at minimum exhaust O2 availability condition of 80% engine load. The NOx level was reduced from 144 ppm to 103 ppm for syngas-diesel mode at the best efficiency point. Due to poor combustion efficiency of dual fuel operation, there were increases in CO and HC emissions throughout the range of engine test loads. The decrease in peak pressure causes the exhaust gas temperature to rise at all loads of dual fuel operation. The present investigation provides some useful indications of using syngas fuel in a diesel engine under dual fuel operation.

Commentary by Dr. Valentin Fuster
2010;():523-530. doi:10.1115/ES2010-90219.

In this paper, we design a supply-side infrastructure for data centers that runs primarily on energy from digested farm waste. Although the information technology and livestock industries may seem completely disjoint, they have complementary characteristics that we exploit for mutual benefit. In particular, the farm waste fuels a combined heat and power system. The data center consumes the power, and its waste heat feeds back into the combined system. We propose a resource management system to manage the resource flows and effluents, and evaluate the direct and indirect economic benefits. As an example, we explain how a hypothetical farm of 10,000 dairy cows could fulfill the power requirements of a 1MW data center.

Topics: Design , Data centers
Commentary by Dr. Valentin Fuster
2010;():531-540. doi:10.1115/ES2010-90227.

In the United States, installation of emission-free sources of power generation, such as wind and solar photovoltaics, has increased recently. Unfortunately, these generation technologies present unique challenges to utilities and grid operators because they are variable and not dispatchable. While energy storage can provide capacitance to the system and thereby make renewable power more dispatchable, storage implementation at the municipal scale is poorly understood. This paper examines future applications of energy storage to reduce costs and improve system reliability for electric utilities at the local level. The city of Austin, Texas was selected as the study area because the city has set aggressive targets of 30–35% of total electricity generation from renewable sources, primarily wind and solar photovoltaics, by 2020. For this analysis, generation assets currently used and those planned for future development by the local utility, Austin Energy, are treated in a unit commitment model using a mixed integer programming (MIP) approach. The model has been developed such that it can be provided any objective function and generation portfolio, and the results can be used by whatever stakeholder has generated those particular inputs. To best simulate operational dispatch conditions, the model includes ramp rate constraints, generator turn-on penalties, and minimum operation levels. Energy storage is included by allowing the model to assign an unconstrained asset throughout the study period, 24 hours, to whatever values will minimize the objective function. For this initial analysis, storage system efficiency, capital and marginal costs were not included, though they may significantly affect total allocated storage. Modeling results indicate that storage availability yields a reduction of as much as $600,000/day in marginal costs for the study area, based primarily on improved utilization of more efficient generating units. This result does not consider savings associated with NOx reductions. Such reductions were studied with a second objective function. While NOx reductions of approximately 9–23% were observed, these emission reductions were accompanied by significant increases in operating costs. Energy storage requirements and potential cost savings under the scenarios examined might be beneficial to researchers interested in grid-scale storage. These results can also be used to determine appropriate cost targets for storage researchers and manufacturers.

Commentary by Dr. Valentin Fuster
2010;():541-546. doi:10.1115/ES2010-90303.

In this paper we present a road-map for rural electrification in developing countries by means of Renewable Energy based MiViPPs (Microutility virtual power plants). First and foremost a feasibility and viability analysis of the various upcoming and alternative renewable energy options is performed with respect to rural environmental constraints and demands. Renewable Energy based DDG’s (Decentralized Distributed Generation Units) offer the potential for affordable, clean electricity with minimal losses and effective maintenance and local cost recovery. But Independent DDG projects are fraught with their own issues mainly stemming from the unreliable and intermittent nature of the generated power and high costs. We propose an alternative approach to rural electrification which involves off grid DDG units operated at the local level taking advantage of feasible renewable energy technologies, which can effectively serve rural areas and reduce the urgency of costly grid extension. In MIVIPP model, a multitude of decentralized units (renewable energy based units and a non-renewable energy based unit for last mile backup) are centrally controlled and managed as part of an interconnected network, resulting into a virtual power plant that can be operated as a distributed power plant large enough to reliably serve all the local electricity demands in a cost effective manner. Finally, by a set of simulation results we establish how an automated MIVIPP (based on an Intelligent Auto Control System) effectively addresses all the issues pertaining to Dispersed DDG units by leveraging the scalability achieved by mutually augmenting the supplies from different Renewable Energy Based DDG units.

Commentary by Dr. Valentin Fuster
2010;():547-557. doi:10.1115/ES2010-90350.

This paper describes the Sailboat Integrated Hydroelectric Generator (SIHG). This turbine is intended to be fixed to the transom of a 30–40 foot sailing vessel to produce green power for the vessel’s electrical systems. The design goal for the SIHG was the generation of a minimum of 225 watts at 6 knots and an ideal output of 400 watts at 6 knots. Power is generated by the SIHG when water moving over five turbine blades creates rotational motion, which is transferred through a gear box to a three-phase electrical generator. The three-phase electrical output is then rectified and used to recharge the boat’s battery. Presently, most sailboats of this size run their engines in order to recharge their batteries. The SIHG produces no emissions and has no operating costs. Extensive testing in the Thames River at the U.S. Coast Guard Academy in New London Connecticut produced data that was then used to determine the power output and efficiency of the SIHG at various speeds through the water. The turbine was fixed to the transom of a dinghy which was then towed behind a rigid hulled inflatable vessel to simulate a sailboat under wind power. Novel data collection methods and instrumentation were then used to gather power and drag data for the turbine at various speeds. Power output plots and efficiency curves were calculated from this data and are represented in this paper. Actual performance shows that the SIHG is capable of producing 275 watts at 6 knots and 400 watts at 8 knots. The maximum efficiency of the SIHG is calculated to be 37% and occurs when traveling through the water at a speed of 5 knots. Due to the substantial power generation at relatively low speeds, tidal applications are discussed.

Topics: Testing
Commentary by Dr. Valentin Fuster
2010;():559-565. doi:10.1115/ES2010-90351.

This paper describes a method for the design of a low r.p.m water turbine designed for an operating point of 5 knots that would be suitable for use as a generator on a recreational sailboat. The low flow speed also means that this design process is also suitable for the hydraulic design of stationary tidal or current generators. The turbine example described in this pare has subsequently been manufactured and successfully tested with a hydraulic efficiency of 13%. Details of the testing are described in a separate paper. (Bredariol et al (2010)).

Commentary by Dr. Valentin Fuster
2010;():567-576. doi:10.1115/ES2010-90374.

NREL and research partner GE are conducting the Western Wind and Solar Integration Study (WWSIS) in order to provide insight into the costs and operational impacts caused by the variability and uncertainty of wind, photovoltaic, and concentrated solar power employed to serve up to 35% of the load energy in the WestConnect region (Arizona, Colorado, Nevada, New Mexico, and Wyoming). The heart of the WWSIS is an hourly cost production simulation of the balancing areas in the study footprint using GE’s Multi-Area Production Simulation Model (MAPS). The estimated 2017 load being served is 60 GW, with up to 30 GW of wind power and 4 GW of existing hydropower. Because hydropower generators are inherently flexible and often combined with reservoir storage, they play an important role in balancing load with generation. However, these hydropower facilities serve multiple higher priority functions that constrain their use for system balancing. Through a series of comparisons of the MAPS simulations, it was possible to deduce the value of hydropower as an essential balancing resource. Several case comparisons were performed demonstrating the potential benefits of hydro and to ascertain if the modeled data was within the defined hydro parameters and constraints. The results, methodologies, and conclusions of these comparisons are discussed, including how the hydro system is affected by the wind power for different wind forecasts and penetration levels, identifying the magnitude and character of change in generation pattern at each of the selected hydro facilities. Results from this study will focus on the appropriate benefits that hydropower can provide as a balancing resource including adding value to wind and solar and reducing system operating costs to nearly one billion dollars when offsetting more expensive generation systems as large penetration levels of renewable, especially wind power, are introduced to the grid system.

Commentary by Dr. Valentin Fuster
2010;():577-584. doi:10.1115/ES2010-90377.

The levelized costs of delivered energy from the leading technologies for grid-scale energy storage are calculated using a model that considers likely number of cycles per year, application-specific expected lifetime, discount rate, duty cycle, and likely trends in the markets. The expected capital costs of the various options evaluated — pumped hydrostorage, underground pumped hydrostorage (UPHS), hydrogen fuel cells, carbon-lead-acid batteries, advanced adiabatic compressed air energy storage (AA-CAES), lead-acid batteries, lithium-ion batteries, flywheels, sodium sulfur batteries, ultra capacitors, and superconducting magnetic energy storage (SMES) — are based on recent installation cost data to the extent possible. The marginal value of the delivered stored energy is analyzed using recent grid-energy prices from regions of high wind-energy penetration. Grid-scale energy storage is expected to lead to significant reductions in greenhouse gas (GHG) emissions only in regions where the off-peak energy is very clean. These areas will be characterized by a high level of wind energy with cheap off-peak and peak prices. At the expected price differentials, the only conventional options expected to be commercially viable in most cases are hydro storage, especially via dam up-rating, and UPHS. The market value of energy storage for short periods of time (under a few hours) is expected to be minimal for grid-scale purposes. Only low-cost daily storage is easily justified both from an economic and environmental perspective.

Topics: Energy storage
Commentary by Dr. Valentin Fuster
2010;():585-594. doi:10.1115/ES2010-90396.

Capacitive deionization relies on carbon aerogel or nanofoam having a surface area of 400 square meters/ gram to attract sodium and chlorine ions to the cathode and anode respectively by applying a voltage of about 1.5 VDC across the anode and cathode. By first physically isolating at least two anodes and two cathodes during charge accumulation, at least two positive monopoles and two negative monopoles are created. Positive/negative monopoles are formed by the enclosure of the cathodes/anodes by an electrically conductive material surrounding the sodium/chlorine ions. At least five or six like charged monopoles are created. At least four of the like charged monopoles (all negative or all positive) can be arranged on a disc. At least one stationary monopole of the same charge is placed adjacent to the disc and positioned so that a repulsive electric field is formed between the stationary monopole and at least one of the monopoles positioned on the disc so that the disc is then forced to rotate a shaft at the center of the disc. The Coulomb force between the monopoles is given by Coulomb’s Law, i.e.,

F = (k/ε)[(q1)(q2)/(r2)]    (1)
where k = 9E+09 Newtons-meter2 /coul2 , q1 and q2 are the charge in coulombs, r is the distance between the charges in meters and ε = 75–81 dielectric constant assuming water between the charges (more likely air having ε = 1). Only a very small amount of charge in each monopole is required, i.e., 10 millicoulombs, (less than a milligram) to provide a force of about 44,000 Newtons (almost 10,000 lbs) if monopoles are separated by 0.5 meters (assuming this equation for Coulomb’s Law for this application is directly applicable without modification-this may not be the case). (For air, the force would be multiplied by 75–81). In a related approach, solute ions are accelerated by an electrostatic field from solute ions collected on electrodes +,-. Using an orthogonal electric field, partition electrodes are closed to capture like charged ions. Polarity is reversed via a transverse (longitudinal) electric field. Linear alignment of ions results in vector alignment of Coulomb forces to create an ion jet for propulsion or particle acceleration. The result is ionic marine propulsion and a possible ionic jet engine that obtains propulsion energy from Coulomb repulsion forces of homopolar separated charge. No combustion or jet fuel is required. Details are available in WO 2008/024927 A2 Ref. [1].

Commentary by Dr. Valentin Fuster
2010;():595-608. doi:10.1115/ES2010-90397.

Wastewater treatment is the method by which sewage of both residential and industrial sources is processed to promote public health and reduce environmental impacts on receiving waters. This physical and biological process generates sludge, which after being treated to reduce pathogens, is referred to as biosolids. In the US there are over 16,000 wastewater treatment plants (WWTP), and every year they produce approximately 7 million tons of biosolids according to the EPA.1 These biosolids are handled differently depending upon local conditions, but most are either buried in landfills, land applied for agriculture or incinerated. Reducing the volume of biosolids produced by each facility is desirable for improving operational efficiency since lower volumes are easier to manage and cheaper to handle and dispose. Most facilities utilize either aerobic digestion to process sludge into biosolids, but larger facilities use anaerobic digestion because this process reduces the overall volume of solids left for management. Anaerobic digestion is more complex and capital intensive, so typically only those facilities treating flows higher than 5 million gallons per day (MGD) use anaerobic digestion. Given current economic conditions and rising energy costs, however, anaerobic digestion is becoming more attractive to utility managers as they attempt to offset energy costs. The anaerobic process produces methane gas. Also called biogas, methane can be utilized not only to fire boilers for heating digesters and nearby buildings, but also to fuel internal combustion engines, microturbines or fuel cells to generate power for plant processes such as blowers in the aeration system. There is also the potential for WWTPs to obtain carbon credits for utilizing renewable energy, especially in those states with renewable portfolio standards. Because anaerobic digestion has limited application in the US, this study evaluated economic viability at plants with design flows less than 5 MGD by incorporating codigestion of food waste to improve the production of biogas for use as energy to reduce operational costs and recover capital costs.

Commentary by Dr. Valentin Fuster
2010;():609-616. doi:10.1115/ES2010-90446.

Reliable energy provision to poor island communities is a challenging problem, particularly in developing countries. This paper presents a pre-feasibility analysis of a wind-solar-diesel electricity generation system to satisfy residential demand in a small, poor island community located in the Gulf of Guayaquil in Ecuador, using HOMER as an analysis tool. The community currently has unreliable diesel generated electricity that energizes homes and street lights, but wishes to replace it with renewable sources as they see that these sources are more aligned with their intention to move into sustainable tourism as a source of income. Relevant meteorological data is lacking and there is only anecdotal evidence that wind is strong in summer time nights at the site. Data for solar irradiance and wind speed were taken from a meteorological station located in Guayaquil, a city relatively close to the island. Wind speed was estimated during a field visit. The community is composed of 85 households for a total of 650 people. Domestic demand data was available and categorized into two types of households. HOMER was used to model four generation system types combining wind turbines, PV panels and Diesel generators to satisfy five different demand models with varying proportions of total households of each type. Selection of the best system is based in both energy and cost optimization, with low use of diesel and low excess of electricity. A sensitivity analysis of the wind and solar resources is included to account for the unavailability of reliable data for wind speed and solar irradiance. The expansion of the system due to population and ensuing demand growth is considered in the analysis using a 25 years project lifetime. The results show that there is potential to install a wind-solar-diesel system under medium-high weather conditions (more than 4 kWh/m2 d for solar irradiance and 3.5m/s for wind speed). As a sample, at a 4.5kWh/m2 d solar irradiance and 4.6m/s wind speed, a wind-solar-diesel system presents a total NPV of $1,616,615 and a LCOE of $0.23 per kWh, with a diesel reduction use of 81.8% and a excess energy percentage of 3.44%.

Commentary by Dr. Valentin Fuster
2010;():617-627. doi:10.1115/ES2010-90479.

The Town of Avon Colorado and the Eagle River Water and Sanitation District have partnered to design, construct, and operate a mechanical “Community Heat Recovery System” which extracts low-grade waste heat from treated wastewater and delivers this heat for beneficial use. Immediate uses include heating of the community swimming pool, melting snow and ice on high pedestrian areas in an urban redevelopment zone in order to improve pedestrian safety, and space heating for project buildings and an adjacent water plant pump station building. Points of use are located within one mile of the treatment plant. The initial system is sized to extract heat from 170 m3 /hr (1.08 mgd) of wastewater plant effluent with a 298 kW (400 hp) heat pump. The heat pump will deliver 1,026 kW (3,500,000 BTU/hr) energy to the heat recovery system. A supplemental natural gas boiler provided to meet peak demands will provide an additional 1,026 kW (3,500,000 BTU/hr) energy. The system is expandable allowing the installation of a second heat pump in the future and roof-mounted solar thermal panels. Power for the waste heat recovery system is provided by wind-generated electricity purchased from the local electric utility. The use of wind power with an electric-powered heat pump enables the agencies to fulfill energy needs while also reducing the carbon footprint. The system will achieve a reduction in the temperature of the treated wastewater, which is currently discharged to the Eagle River during low river flow, fish-sensitive periods. The agencies expect to save tax payers and rate payers money as a result of this project as compared to other alternatives or the status quo because it results in a more sustainable long-term operation. At 2008 utility commodities pricing, delivery of heat generated from this system was estimated to cost about one-third less than that from a conventional natural gas boiler system. This facility is the first of its kind in the U.S. and received a “New Energy Community” grant from the State of Colorado. This project shows how local agencies can work cooperatively for mutual benefit to provide infrastructure which accommodates growth and urban renewal and simultaneously demonstrate strong environmental leadership. The potential application of this technology is broad and global. The installed system is expected to cost about $5,000,000; construction will be completed in 2010.

Topics: Heat recovery
Commentary by Dr. Valentin Fuster
2010;():629-638. doi:10.1115/ES2010-90488.

Fort Huachuca, AZ, located 60 mi Southeast of Tucson, has had over 30 years of experience with various renewable energy systems. This session discusses lessons learned from the successes and failures in that experience, including: an indoor pool solar water heating system (installed 1980); a solar domestic hot water (DHW) system (installed 1981); a grid connected Photovoltaic system (installed 1982); transpired air solar collectors (Solarwalls,™ installed 2001); day-lighting (installed 2001); a 10-KW wind turbine (installed 2002); photovoltaic powered outdoor lighting (installed 1994); a prototype Dish/Stirling solar thermal electric generator (installed 1996); two 30-KW Building Integrated Photovoltaic systems (installed on new membrane roofs in 2009); and a 36-KW Photovoltaic system moved from the Pentagon in June 2009 and became operational November 2009 at Fort Huachuca. Also discussed is an experimental solar attic system (first installed in 2003 and now being fully monitored) that collects hot air in an attic, and via a heat exchanger and tank, produces solar DHW. This paper discusses system design, installation, metering, operation and maintenance, and also work in progress on the installation of commercial, off-the-shelf 3-KW Dish/Stirling solar thermal electric generators and solar thermal/natural gas-to-electric systems at a central plant. Discussions include biogas (methane from a wastewater digester) and biomass (wood chip boiler) being installed at a central heating/cooling plant.

Commentary by Dr. Valentin Fuster
2010;():639-649. doi:10.1115/ES2010-90510.

Many alternative fuels have been introduced in the fuel market in the recent years. But, still there is a lot of research work going on around the world in the conversion of waste substances into useful energy. Some of the researchers show a remarkable interest in using pyrolysis oil as an alternative fuel for diesel engines. Tire pyrolysis oil (TPO) from waste automobile tires has been found to be an energy source. It could be blended with diesel fuel and used as an alternative fuel for diesel engines. But, it cannot be used as the sole fuel in diesel engines due to its poor ignition quality. Diethyl ether (DEE) is a good ignition improver having a cetane number of more than 125. In the present investigation, two different blends of Tire pyrolysis oil and DEE (with addition of DEE at 0.5 and 1%) were used in a single cylinder four stroke water cooled direct injection diesel engine developing a rated power of 3.7 kW at 1500 rpm. The engine was able to run with 100% Tire pyrolysis oil with a maximum DEE addition of 1%. Results indicated that nitric oxide emission reduced by about 4% with an 8% increase in smoke emission at full load when the engine was fueled with TPO and 1% of DEE compared to that of diesel fuel operation. The brake thermal efficiency of the engine fueled with TPO-DEE blends was found to be lesser than that of diesel operation at full load. Brake specific energy consumption was also found to be higher with TPO DEE blends compared to that of diesel fuel operation. The results of the performance and emissions of the DI diesel engine are presented in this paper.

Commentary by Dr. Valentin Fuster

Low/Zero Emission Power Plants and Carbon Sequestration

2010;():651-661. doi:10.1115/ES2010-90146.

Technical and economic metrics of electricity generation from a Waste to Energy (WTE) plant are compared to coal, natural gas combined cycle, biomass, and landfill gas generation alternatives for Austin, Texas under a range of greenhouse gas emissions prices. The WTE technology and history is described, as well as details relevant to a WTE plant in Austin. Technical and economic values for WTE from the literature are discussed. The upper limit of electricity generation from Austin’s MSW stream is 5% of Austin’s 2007 annual electricity consumption. Selection of appropriate values for capital, operating, and fuel costs indicates that WTE is more expensive than all of the alternative generation technologies considered (coal, natural gas combined cycle, landfill gas, and biomass). If greenhouse gas emissions are priced and offsets from fugitive landfill gas emissions are allowed, WTE becomes more cost-competitive by taking credit for offset landfill gas emissions. Under this scenario WTE becomes cost-competitive with biomass at $33 per ton CO2 equivalent, coal at $92 per ton CO2 equivalent, and natural gas at $115 per ton CO2 equivalent.

Commentary by Dr. Valentin Fuster
2010;():663-672. doi:10.1115/ES2010-90147.

There is broad scientific agreement that anthropogenic greenhouse gases are contributing to global climate change and that carbon dioxide (CO2 ) is the primary contributor. Coal-based electricity generation produces over 30% of U.S. CO2 emissions; however, coal is also an available, secure, and low cost fuel that currently provides roughly half of U.S. electricity. As the world transitions from the existing fossil fuel-based energy infrastructure to a sustainable energy system, carbon dioxide capture and sequestration (CCS) will be a critical technology to allow continued use of coal-based electricity in an environmentally acceptable manner. Post-combustion amine absorption and stripping is one leading CO2 capture technology that is relatively mature, available for retrofit, and amenable to flexible operation. However, standard system designs have high capital costs and can reduce plant output by approximately 30% due to energy requirements for solvent regeneration (stripping) and CO2 compression. A typical design extracts steam from the power cycle to provide CO2 capture energy, reducing net power output by 11–40%. One way to reduce the CO2 capture energy penalty while developing renewable energy technologies is to provide some or all CO2 capture energy with a solar thermal energy system. Doing so would allow greater power plant output when electricity demand and prices are the highest. This study presents an initial review of solar thermal technologies for supplying energy for CO2 capture with a focus on high temperature solar thermal systems. Parabolic trough and central receiver (power tower) technology appear technically able to supply superheated steam for CO2 compression or saturated steam for solvent stripping, but steam requirements depend strongly on power plant and CO2 capture system design. Evacuated tube and compound parabolic collectors could feasibly supply heat for solvent stripping. A parabolic trough system supplying the energy for CO2 compression and solvent stripping at a gross 500 megawatt-electrical coal-fired power plant using 7 molal MEA-based CO2 capture would require a total aperture area on the order of 2 km2 or more if sized for an average direct normal solar insolation of 561 W/m2 . The solar system’s capital costs would be roughly half that of the base coal-fired plant with CO2 capture. This analysis finds that irrespective of capital costs, relatively high electricity prices are required for additional electricity sales to offset the operating and maintenance costs of the solar thermal system, and desirable operational periods will be further limited by the availability of sunlight and thermal storage. At CO2 prices near 50 dollars per metric ton of CO2 , bypassing CO2 capture yields similar operating economics as using solar energy for CO2 capture with lower capital cost. Even at high CO2 prices, any operating profit improvement from using solar energy for CO2 capture is unlikely to offset system capital costs. For high temperature solar systems such as power towers and parabolic troughs, direct electricity generation is likely a more efficient way to use solar energy to replace output lost to CO2 capture energy. However, low temperature solar systems might integrate more seamlessly with solvent stripping equipment, and more rigorous plant design analysis is required to definitively assess the technical and economic feasibility of using solar energy for CO2 capture.

Commentary by Dr. Valentin Fuster
2010;():673-680. doi:10.1115/ES2010-90148.

CO2 capture and storage (CCS) systems are technologies that can be used to reduce CO2 emissions by different industries where combustion is part of the process. A major problem of CCS system utilization in electricity generation industry is their high efficiency penalty in power plants. For different types of power plants fueled by oil, natural gas and coal, there are three main techniques that can be applied: • CO2 capture after combustion (post-combustion); • CO2 capture after concentration of flue gas by using pure oxygen in boilers and furnaces (oxy-fuel power plant); • CO2 capture before combustion (pre-combustion). More than 90% of electricity generation in Iran is based on fossil fuel power plants. Worldwide, electricity generation is responsible for 54% of GHG emissions. Thus, it is vital to reduce CO2 emission in fossil fuel-fired power plants. In this paper, it is shown that, by applying CO2 capture systems in power generation industry, very low CO2 emission intensity is possible but the energy and economic penalties are substantial. The analyses showed that for different technologies efficiency penalty could be as high as 25% and cost of electricity might increase by more than 65%. Two scenarios for Iranian electricity generation sector were investigated in this paper: installing CCS in the existing power plants with current technologies and replacing existing power plants by natural gas combined cycle plants equipped with CO2 capture system. The results revealed that the GHG intensity can be reduced from 610 to 79 gCO2 eq/kWh in the first scenario and to 54 gCO2 eq/kWh in the second scenario.

Commentary by Dr. Valentin Fuster
2010;():681-690. doi:10.1115/ES2010-90156.

Global focus on greenhouse gas emissions has led the United State’s legislature to discuss various strategies to reduce carbon dioxide (CO2 ) emissions. With coal-fired plants responsible for roughly half of United States (U.S.) electricity generation and approximately 30% of the nation’s CO2 emissions, coal-fired plants will be largely affected by any future CO2 emission regulations. However, coal-based generation could continue to meet our electricity demands while complying with future CO2 emissions restrictions with the addition of carbon dioxide capture and sequestration (CCS) technology. Most studies of CCS systems have demonstrated a permanent energy requirement of 11–40% of a plant’s output when operating continuously at a 90% CO2 removal rate. This study, however, used a dynamic model of the Electric Reliability Council of Texas (ERCOT) electric grid to consider post-combustion CO2 capture systems that can operate flexibly. Post-combustion CO2 capture systems using chemical absorption and stripping are particularly suited for retrofitting existing plants and operating in a flexible manner. Flexible carbon capture allows plant operators to vary the energy used for CO2 capture and compression in order to regain this generation capacity when desirable. Thus, flexibility can be used to choose the CO2 capture rate that allows the most economical combination of operating costs, electricity price, and output levels. Furthermore, operating at lower CO2 capture energy requirement levels and increasing output capacity during peak demand periods could dramatically reduce the amount of replacement capacity needed to replace potential output lost when CO2 capture systems are in operation. This research uses an existing modeling framework of a dynamic hourly dispatch system to study the economic, environmental, and performance implications of flexible CO2 capture over an investment lifetime. The effects of CO2 prices, natural gas fuel prices, and replacement capacity costs were analyzed along with various operating strategies. The fuel mixture behavior and emissions effects are presented, showing that large emissions reductions can be achieved using the current ERCOT plant fleet with the addition of flexible CO2 capture. An annual system-level cash-flow analysis is used to determine a net present value (NPV) for a group of CO2 capture plants under a range of possible replacement capacity costs. If replacement capacity costs are accounted for, flexibility can improve the NPV of a CO2 capture investment by substantially lowering the associated capital costs to replace output lost to CO2 capture energy requirements.

Commentary by Dr. Valentin Fuster
2010;():691-700. doi:10.1115/ES2010-90186.

A thermoeconomic analysis of microalgae co-firing process for fossil fuel-fired power plants is studied. A process with closed photobioreactor and artificial illumination is evaluated for microalgae cultivation, due to its simplicity with less influence from climate variations. The results from this process would contribute to further estimation of process performance and investment. The concept of co-firing (coal-microalgae or natural gas-microalgae) includes the utilization of CO2 from power plant for microalgal biomass culture and oxy-combustion of using oxygen generated by biomass to enhance the combustion efficiency. As it reduces CO2 emission by recycling it and uses less fossil fuel, there are concomitant benefits of reduced GHG emissions. The by-products (oxygen) of microalgal biomass can be mixed with air or recycled flue gas prior to combustion, which will have the benefits of lower nitrogen oxide concentration in flue gas, higher efficiency of combustion, and not too high temperature (avoided by available construction materials) resulting from coal combustion in pure oxygen. Two case studies show that there are average savings about $0.386 million/MW/yr and $0.323 million/MW/yr for coal-fired and natural gas-fired power plants, respectively. These costs saving are economically attractive and demonstrate the promise of microalgae technology for reducing greenhouse gas (GHG) emission.

Commentary by Dr. Valentin Fuster
2010;():701-710. doi:10.1115/ES2010-90199.

Dimethyl ether (DME) is a promising alternative fuel, but direct combustion of DME will result in extra energy penalty for CO2 separation. In this paper, an advanced power-generation system with CO2 recovery integrating DME-fueled chemical-looping combustion is proposed. In the reduction reactor, DME is oxidized by Fe2 O3 into CO2 and H2 O, and Fe2 O3 is reduced into FeO simultaneously. Since the endothermic reduction of Fe2 O3 with DME requires relatively low-grade thermal energy around 180°C, waste heat is used to provide the reaction heat. FeO is oxidized into Fe2 O3 by air in the oxidation reactor, producing high-temperature flue gas to generate electricity through a thermal cycle. The gas production from the fuel reactor only consists of CO2 and H2 O, so CO2 can be easily separated through condensing with no extra energy penalty. As a result, the thermal efficiency could be expected to be 58.6% at a turbine inlet temperature of 1288°C. Additionally, experiments on DME-fueled Chemical-looping combustion are carried out to verify the feasibility of the core process. This proposed system may provide a new approach for high efficient use of DME in the industrial fields, and offer a possibility of chemical-looping combustion with inherent CO2 capture for the alternative fuel.

Commentary by Dr. Valentin Fuster
2010;():711-722. doi:10.1115/ES2010-90237.

Thermal power plants provide the majority of electricity used around the world and will continue to do so for some time. The goal of this paper is to provide an understanding of technology and fuels used in thermal power plants and the byproducts they create. The emphasis is on magnitudes of fuels used, emissions created and the sustainability and practicality of methods of production and control. A basic thermal power plant burns fuel to produce steam, which turns a turbine generator to produce electricity. The basic elements of thermodynamics apply to all thermal power plants: a heat source, a heat engine and a heat sink. Heat sources for thermal power plants include boilers fueled by coal, natural gas and biomass; gas turbines fueled by natural gas; and nuclear reactors fueled by uranium. Topics of discussion include the logistics involved in supplying fuels and handling their byproducts, including carbon compounds; types of heat engines utilized; methods to improve efficiency to reduce the fuel consumed; byproducts generated; and the heat sink required. The focus is on Rankine (vapor) and Brayton (gas) cycles. Although not directly affecting carbon byproducts, the heat sink used affects the heat engine efficiency and the consumption of water, a valuable resource. The types of heat sinks discussed include open-cycle water cooling, closed-cycle water cooling and air cooling. Thermal power plants provide many benefits to the electrical power system. They provide power 24 hours a day and 365 days a year, regardless of the weather. They are relatively compact, making them easier to build, operate and maintain. They also can be located close to electrical load concentrations reducing the need for transmission lines that disrupt the environment. The technologies involved in thermal power plant operation are proven effective and in use today. The challenges are to manage the fuel supply and byproduct disposal in an environmentally acceptable manner.

Commentary by Dr. Valentin Fuster

Transportation Energy Systems

2010;():723-733. doi:10.1115/ES2010-90027.

California’s main source of greenhouse gas emissions is transportation, a relatively uncontrolled sector. Of the major energy commodities used by individuals, transport fuels are alone in lack of utility regulation: the dominance of refineries as transportation fuel suppliers suggests there may be an opportunity for California to engage its refining industry about transitioning into a transportation fuel utility role. While this concept could be extended beyond California, it is uniquely suited to California because of the State’s fuel isolation from the rest of the country: with its demand for a boutique low-pollution fuel, California is served almost exclusively by Californian refineries that face a different set of regulations than most other American refineries do. Due to infrastructural barriers and long vehicle lifetime, most forecasts predict slow penetration of alternative transportation technologies, even as policymakers suggest an urgent need for rethinking the transportation system. These infrastructural barriers, including the chicken-and-egg problem of building fuel supply stations and vehicles that use alternative fuels, may be more easily overcome by a single planning body than by a market that only uncertainly rewards first movers. By ensuring supply of fuels the state wishes to promote, California can more easily launch alternative vehicle policies and incentives.

Commentary by Dr. Valentin Fuster
2010;():735-746. doi:10.1115/ES2010-90058.

An external combustion engine design using steam is described which has good efficiency at full power and even better efficiency at the low power settings common for passenger vehicles. The engine is compact with low weight per unit power. All of its components fit in the engine compartment of a front-wheel drive vehicle despite the space occupied by the transaxle. It readily fits in a rear-drive vehicle. Calculated net efficiencies, after accounting for all losses, range, depending on engine size, from 28–32% at full power increasing to 33–36% at normal road power settings. A two-stage burner, 100% excess air, and combustion temperature below 1500°C assure complete combustion of the fuel and negligible NOx. The engine can burn a variety of fuels and fuel mixes, which should encourage the development of new fuels. Extensive software has been written that calculates full power and part-load energy balances, structural analysis and heat transfer, and performance in specified vehicles including using SAE driving cycles. Engines have been sized from 30 to 3200 hp. In general, fuel consumption should be at least 1.5 times lower than gasoline engines and about the same as diesels operating at low to moderate load settings. Due to this analysis, a prototype, when built, should perform as expected.

Topics: Heat engines , Stress
Commentary by Dr. Valentin Fuster
2010;():747-759. doi:10.1115/ES2010-90291.

Diesel buses of public transportation in the main cities of Colombia are formed by turbocharger engines, such machines could operate in dual Diesel-NG way using the gaseous fuel as main energy source and the liquid fuel to pilot ignition of the air-NG mixture previously formed. This research is centered on the studies about formation process of the mixture in the intake system in a turbocharger dual engine. In this study the transport equations are established, it is associated to the fluids which enter to the intake engine during a period of engine operation. This model is simulated by means of CFD tools, using an electronic injector to provide natural gas. Also it is considered the fluidynamic behavior of mixture. Finally an experimental design applied to the simulations is made with the goal of optimize operational conditions of the injector that allow to get the most homogeneous mixture on the inlet runner to one of the cylinders engine. This mixture was obtained injecting natural gas at a pressure of 10 bars and placing the injector as close to the intake manifold.

Commentary by Dr. Valentin Fuster
2010;():761-773. doi:10.1115/ES2010-90294.

Fuel costs, which are the single most important driver of marginal costs for marine transportation, account for almost 50% of total voyage costs for typical configurations and operational modes. Hence, there has developed a desire among operators and manufacturers of all classes of ships to embrace innovative ways to reduce the demand for fuels. The luxury yacht segment presents an attractive market for investigating and assessing the impacts of fuel-saving technologies because the large ships benefit from the fuel savings, have more flexible performance requirements and have owners who are more likely to embrace the required premiums for experimental technologies. This report analyzes the effects of fitting such a yacht with a sail system, a solar panel system, and an energy storage system (ESS). Integrating a sail system to reduce propulsion loads provides significant benefit with respect to fuel economy. In contrast, the total amount of power provided by the solar panel system provides very little benefit, even when extensive deck paneling is used and panels are fit to rigid wing sails. Utilizing an ESS in the same manner as with a terrestrial hybrid vehicle to manipulate load distribution provides insignificant benefit for fuel consumption reduction, but seems to present opportunities for emissions reduction, which has played an increasingly important role in marine environmental concerns.

Commentary by Dr. Valentin Fuster
2010;():775-784. doi:10.1115/ES2010-90362.

Three major challenges — grid stability, domestic oil limitations, and climate change — could all be addressed simultaneously by using off-peak electrical energy to recycle CO2 into liquid fuels (such as gasoline, jet fuel, and diesel). Simulations have shown that recent innovations should make it practical to reduce CO2 to CO at over 66% of theoretical efficiency limits. When combined with other process advances, it would then be possible to synthesize most hydrocarbons and alcohols from point-source CO2 and clean off-peak grid energy (wind or nuclear) at system efficiencies in the range of 51–61%. Energy storage density in renewable, carbon-neutral kerosene is 44 MJ/kg, compared to ∼0.4 MJ/kg for Li-ion batteries. This process begins by electrolyzing water using clean energy to get the hydrogen required by the Reverse Water Gas Shift (RWGS) reactor and by a novel Renewable Fischer Tropsch Synthesis (RFTS) process. Off-peak grid energy averaged only $13/MWhr in the Minnesota hub in 2009. At such prices, the synthesized liquid fuels (“WindFuels”) should compete even when petroleum is only $50/bbl. Considerable effort over the past decade has been put into exploring high-temperature (HT) paths toward the production of renewable syngas (H2 + CO) that could lead to sustainable synthesis of liquid fuels; but competitive fuel production from these HT thermo-chemical routes still appears to be decades away. An alternative path — the RWGS reaction — utilizes much less aggressive conditions and should be much more practical. With low-cost hydrogen becoming available from off-peak wind and nuclear, efficient reduction of CO2 to CO becomes viable at moderate temperatures (750–1000 K) via the RWGS reaction. Challenges arise because of equilibrium limits imposed by the reaction thermodynamics below 800 K and because of competing methanation and coking reactions above 800 K to 1000 K, depending on the catalysts. Several promising sets of conditions and catalysts are being evaluated. To drive the reaction to the right, a multi-stage process is required with efficient separation processes. This in turn depends on advances in cost-effective gas-to-gas recuperators for relatively low pressures to limit parasitic methanation reactions. Another challenge may be passivation of the recuperator surfaces to minimize hydrogenation of the CO during the heat recovery. Preliminary simulations indicate reduction of CO2 to CO with about 2.2 MJ/kg-CO should be practical at commercial scale.

Topics: Fuels , Carbon dioxide
Commentary by Dr. Valentin Fuster
2010;():785-793. doi:10.1115/ES2010-90363.

In U.S, the ground vehicles consume about 77% of all (domestic and imported) petroleum; 34% is consumed by automobiles, 25% by light trucks and 18% by large heavy duty trucks and trailers. It has been estimated that 1% increase in fuel economy can save 245 million gallons of fuel/year. Additionally, the fuel consumption by ground vehicles accounts for over 30% of CO2 and other greenhouse gas (GHG) emissions. Moreover, most of the usable energy from the engine goes into overcoming the aerodynamic drag (53%) and rolling resistance (32%); only 9% is required for auxiliary equipment and 6% is used by the drive-train. 15% reduction in aerodynamic drag at highway speed of 55mph can result in about 5–7% in fuel saving. The goal of this paper is to demonstrate by numerical simulations that the active flow control (AFC) technology can be easily deployed /retrofitted to reduce the aerodynamic drag of ground vehicles by 15–20% at highway speed. For AFC, we employ a few oscillatory jet actuators (also known as synthetic jet actuators) at the rear face of the ground vehicle. These devices are easy to incorporate into the existing vehicles with very modest cost. The cost may come down significantly for a large volume — in hundreds of millions, especially for ground vehicles. Numerical simulations are performed using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations on solution adaptive structured grids in conjunction with a two-equation realizable k-ε turbulence model. The commercially available grid generator “GAMBIT” and the CFD solver “FLUENT” are employed in the simulations. Three generic ground vehicle configurations are considered in the simulations; the experimental data has been available for these configurations without and with AFC. The numerical simulations are in good agreement with the experimental data. These studies clearly demonstrate that the AFC techniques can be effectively employed to achieve significant reduction (10–15%) in aerodynamic drag of ground vehicles thereby reducing the fuel consumption by 5–7%.

Commentary by Dr. Valentin Fuster
2010;():795-801. doi:10.1115/ES2010-90366.

Doty Energy is developing advanced processes to permit the production of fully carbon-neutral gasoline, jet fuel, diesel, ethanol, and plastics from exhaust CO2 and off-peak clean energy (wind and nuclear) at prices that can compete with fossil-derived products. Converting CO2 into fuels will eliminate the need for CO2 sequestration, reduce global CO2 emissions by 40%, and provide a nearly insatiable market for off-peak wind. It has long been known that it is theoretically possible to convert CO2 and water into standard liquid hydrocarbon fuels at high efficiency. However, the early proposals for doing this conversion had efficiencies of only 25% to 35%. That is, the chemical energy in the liquid fuels produced (gasoline, ethanol, etc.) would be about the 30% of the input energy required. The combination of the eight major technical advances made over the past two years should permit this conversion to be done at up to 60% efficiency. Off-peak grid energy averaged only $16.4/MWhr in the Minnesota hub throughout all of 2009 (the cheapest 6 hours/day averaged only $7.1/MWh). At such prices, the synthesized standard liquid fuels (dubbed “WindFuels”) should compete even when petroleum is only $45/bbl. A more scalable alternative for transportation fuels is needed than biofuels. It is in our economic and security interests to produce transportation fuels domestically at the scale of hundreds of billions of gallons per year. WindFuels can scale to this level, and as they are fully carbon-neutral they will dramatically reduce global CO2 emissions at the same time. Switching 70% of global transportation fuels from petroleum to WindFuels should be possible over the next 30 years. WindFuels will insure extremely strong growth in wind energy for many decades by generating an enormous market for off-peak wind energy. WindFuels is based largely on the commercially proven technologies of wind energy, water electrolysis, and Fischer Tropsch (FT) chemistry. Off-peak low carbon energy is used to split water into hydrogen and oxygen. Some of the hydrogen is used to reduce CO2 into carbon monoxide (CO) and water via the Reverse Water Gas Shift (RWGS) reaction. The CO and the balance of the hydrogen are fed into an FT reactor similar to those used to produce fuels and chemicals from coal or natural gas. The processes have been simulated, and key experiments are being carried out to help optimize process conditions and validate the simulations.

Commentary by Dr. Valentin Fuster
2010;():803-809. doi:10.1115/ES2010-90411.

The Embry-Riddle HyREV system is an innovative combination of power-split Hybrid and Extended-Range Electric Vehicle technologies, designed to reduce petroleum energy consumption and improve vehicle efficiency across a range of operating conditions on a captured GM fleet vehicle. The HyREV system was developed for the EcoCAR Challenge, and features a high degree of vehicle electrification including all electric accessories, plug-in charging and electric all-wheel-drive through the integration of three electric motors. The proper packaging and integration of components used in the EcoCAR vehicle development process required a comprehensive understanding of element interaction from both a static (space claim) and dynamic (feasibility) standpoint. The research conducted in this competition is used as a capstone project for a wide array of majors, as well as being integrated extensively in several courses in the form of projects and lectures. The overall vehicle design requires expertise in mechanical, electrical, aerospace, computer, software, and controls engineering, as well as incorporating human factors students into the failure modes and effects analysis. The team is split into the different majors for organizational hierarchy; however, there are many tasks that require multidisciplinary ideas and experiences to properly design. The first year of EcoCAR incorporated an entirely virtual design, with the teams receiving hardware in year two. The team is currently in year two, and is assembling the physical components of the vehicle, along with the controls architecture that will drive the vehicle’s power systems. This 65% “mule” vehicle will be tested May 2010 at GM’s Desert Proving Grounds, located in Yuma, Arizona.

Commentary by Dr. Valentin Fuster
2010;():811-817. doi:10.1115/ES2010-90492.

In this paper the impact of different utilization scenarios of electric vehicles on the German grid is analyzed. Two different charging strategies are tested. Firstly the impact of unmanaged charging of electric vehicles on the national grid is simulated. Secondly charging and usage of the mobile storage in off-peak times is simulated. An important part of the simulation is to analyse the availability of electric vehicles. This part determines the percentage of vehicles, which can be plugged into the grid on hourly basis for all days of a typical week. The analysis of the availability of vehicles shows an overall high availability of plug-in electric passenger cars in Germany. A significant difference in the characteristics between weekdays, Saturdays and Sundays is evident. A high potential to use electric passenger cars for balancing the fluctuating renewable energy can be presumed, on the one hand due to the high availability of electric vehicles and on the other hand due to the large number of vehicles being plugged into the grid in the evening hours for which charging could be delayed into the night. In conclusion the simulation shows that with an unmanaged charging strategy the fluctuations of the demand increase above average assuming a rising number of electric vehicles introduced in Germany. If the whole vehicle fleet is substituted by electric vehicles, the national electricity consumption would increase only by about 18%. Concurrently the fluctuations of the national demand in Germany would almost double. However with an optimized charging strategy, a positive impact of the usage of the mobile storage on the national grid (reduction of fluctuations) can be recognized. Thereby the electric vehicles can be charged completely during the night, when the electricity consumption is low.

Commentary by Dr. Valentin Fuster

Micro and Nano Technologies in Energy Systems

2010;():819-824. doi:10.1115/ES2010-90022.

Direct-absorption solar thermal collectors have recently been shown to be a promising technology for photothermal energy conversion but many parameters affecting the overall performance of such systems haven’t been studied in depth, yet alone optimized. Earlier work has shown that the overall magnitude of the extinction coefficient can play a drastic role, with too high of an extinction coefficient actually reducing the efficiency. This study investigates how the extinction coefficient impacts the collector efficiency and how it can be tuned as a function of depth to optimize the efficiency, and why this presents a unique design over conventional solar thermal collection systems. Three extinction profiles are investigated: uniform, linearly increasing, and exponentially increasing.

Commentary by Dr. Valentin Fuster
2010;():825-832. doi:10.1115/ES2010-90055.

Concentrated solar energy is becoming the input for an increasing number of thermal systems [1]. Recent papers have indicated that the addition of nanoparticles to conventional working fluids (i.e. nanofluids) can improve heat transfer and solar collection [2–4]. Thermal models developed herein show that nanofluid collectors can be more efficient than conventional concentrating solar thermal technology. This work indicates that power tower schemes are the best application for taking advantage of potential nanofluid efficiency improvements. This study provides a notional design of how such a nanofluid power tower receiver might be built. Using this type of design, we show a theoretical enhancement in efficiency of up to a 10% by using nanofluids. Further, we compare the energy and revenue generated in a conventional solar thermal plant to a nanofluid one. It was found that a 100MWe capacity solar thermal power tower operating in a solar resource similar to Tucson, AZ could generate ∼$3.5 million more per year by incorporating a nanofluid receiver.

Commentary by Dr. Valentin Fuster
2010;():833-839. doi:10.1115/ES2010-90197.

To effectively harvest waste heat from larger devices, a MEMS-based boiler is fabricated to boil working fluids for use in a low temperature steam system. The boiler is designed and fabricated to collect waste heat and drive working fluid phase change through novel microstructures. This boiled working fluid can then be made available for expansion by other MEMS-based components like piezoelectric membranes or cantilevers. Two different boiler designs are studied and compared in these experiments. Both designs rely on capillary channels to pump working fluid from surrounding reservoirs out across heated boiling surfaces. First, a baseline silicon device is fabricated using standard RIE techniques to produce silicon capillary channels. Channel widths of 300 and 100 μm are studied with maximum aspect ratios of 1:1. Improved aspect ratio capillary channels are investigated through the use of SU-8 polymer structures. The maximum aspect ratios of the SU-8 based channels are 20:1 with channel widths down to 10 μm. SU-8 based boilers deliver improved performance compared to their silicon counterparts. The maximum mass transfer rate was 4.49 mg/s for SU-8 channels with 20:1 aspect ratios. By contrast, the maximum mass transfer rate was 3.18 mg/s for silicon capillary channels with 1:1 aspect ratios. Working fluids like 3M™ HFE 7200 are used in these experiments.

Commentary by Dr. Valentin Fuster
2010;():841-845. doi:10.1115/ES2010-90293.

Nanofluids are synthesized by doping solvents with nano-particles at minute concentrations (typically less than 1 percentage by volume). Experimental studies have shown that nano-particles can dramatically enhance thermal conductivity of various liquid solvents. This is also associated with enhancement of other transport properties (e.g., viscosity, specific heat, diffusivity, etc.). Hence, nanofluids are attractive materials for solar thermal applications. The objective of this study is to investigate the optimum performance of various nanofluids for solar thermal storage applications. Dimensional analyses and similitude techniques will be used to theoretically estimate the enhancement of transport properties of various nanofluids to predict their efficacy for solar thermal storage applications.

Commentary by Dr. Valentin Fuster

Exergy Applications: Sustainability, Renewable Energy

2010;():847-857. doi:10.1115/ES2010-90082.

In this paper, we explore a reduced-order framework to predict the sustainability of a given system. The approach combines concepts from economic theory, thermodynamics, and the environmental sciences into a simple scheme that allows evaluation of system sustainability in terms of a small number of variables. The underlying hypothesis behind the work is that sustainability can be correlated to reversibility, and therefore should bear a relationship with transitions from an initial benign state. We propose evaluation along three dimensions: (i) physical; (ii) economic; and (iii) social. The measure of physical damage follows from the second law of thermodynamics, and specifically we show when and how second-law derived metrics (such as lifetime exergy consumption) can be extended to capture additional impacts. The measure of economic impact is derived by correlating physical transformations of objects with their relative economic value, specifically through use of input-output models that have been previously published in the literature. Lastly, we explore capturing social value through a proxy of indexed measures that correlate to the notion of a ‘social entropy’, which is suggested as an approximation for the deviation of society from a general state of well-being. We propose unifying all three of these approaches through a generalized framework, and thus suggest a simple but broad ‘sustainability performance’ metric. The paper concludes by discussing the challenges associated with widespread implementation, validation, and completeness of such a framework.

Commentary by Dr. Valentin Fuster
2010;():859-868. doi:10.1115/ES2010-90144.

Performance analysis of a 500 MWe steam turbine cycle is performed combining the thermodynamic first and second-law constraints to identify the potential avenues for significant enhancement in efficiency. The efficiency of certain plant components, e.g. condenser, feed water heaters etc., is not readily defined in the gamut of the first law, since their output do not involve any thermodynamic work. Performance criteria for such components are defined in a way which can easily be translated to the overall influence of the cycle input and output, and can be used to assess performances under different operating conditions. A performance calculation software has been developed that computes the energy and exergy flows using thermodynamic property values with the real time operation parameters at the terminal points of each system/equipment and evaluates the relevant rational performance parameters for them. Exergy-based analysis of the turbine cycle under different strategic conditions with different degrees of superheat and reheat sprays exhibit the extent of performance deterioration of the major equipment and its impact to the overall cycle efficiency. For example, during a unit operation with attemperation flow, a traditional energy analysis alone would wrongly indicate an improved thermal performance of HP heater 5, since the feed water temperature rise across it increases. However, the actual performance degradation is reflected as an exergy analysis indicates an increased exergy destruction within the HP heater 5 under reheat spray. These results corroborate to the deterioration of overall cycle efficiency and rightly assist operational optimization. The exergy-based analysis is found to offer a more direct tool for evaluating the commercial implication of the off-design operation of an individual component of a turbine cycle. The exergy destruction is also translated in terms of its environmental impact, since the irretrievable loss of useful work eventually leads to thermal pollution. The technique can be effectively used by practicing engineers in order to improve efficiency by reducing the avoidable exergy destruction, directly assisting the saving of energy resources and decreasing environmental pollution.

Commentary by Dr. Valentin Fuster
2010;():869-878. doi:10.1115/ES2010-90162.

In today’s society in which energy costs are high, the use of renewable energy sources has gained importance in cooling and heating systems. In recent years, solar cooling, which is a type of renewable energy source, is increasing rapidly in use in Europe. A solar assisted absorption cooling system was designed for acclimatizing villas in Mardin, Turkey, and the performance of the system under different temperatures was analyzed using Matlab. The cooling load of the villas was calculated assuming a cooling season of May 15 to September 15. The cooling capacity was calculated to be 106 kW. Changes in the coefficient of performance, the capacity of the hot water driven absorption cooling system and the exergy destruction values of the system according to our country’s meteorological data were calculated using Matlab. The amounts of inlet and outlet exergy were calculated separately for each component. Calculations were performed for two dead state temperatures: 25 °C and the environmental temperature, which is a more realistic approach. Therefore, the effect of varying the dead state temperature on the results was determined. It is observed that the greatest source of exergy destruction in the system was the solar collectors and the second greatest source of exergy destruction was the generator. The hourly distributions of exergy destruction values are given in a table. The effects of environmental temperature and solar insulation were stated for the optimization of energy and exergy in the combined system, which are planned to be established.

Commentary by Dr. Valentin Fuster
2010;():879-888. doi:10.1115/ES2010-90255.

The idea of this study is to investigate possibilities to use sunlight as the main energy source to generate and store electrical energy via different methods and technologies. Several systems consisting of photovoltaics, photoelectrolytic converters and solarthermal reformers in combination with fuel cells have been investigated in terms of efficiency and costs. A simple energetic approach would not account for these different kinds of energy and their differing availabilities (radiant, thermal, chemical, and electrical energy). To consider different forms of energy and compare them in a fair manner, exergy as the useful part of energy (the part that can theoretically be completely converted to work) provides a perfect instrument for dealing with complex energy conversion systems. In this study, four different scenarios have been investigated: Scenario A describes the direct conversion of sunlight to electricity by photovoltaics. The electric power is used in a Polymer Electrolyte Membrane (PEM) electrolyzer to split water to hydrogen which is stored in a pressure tank. A PEM fuel cell converts hydrogen to electricity on demand. Scenario B deals with a photoelectrolytic cell splitting water to hydrogen by solar irradiation combined with a storage tank and a fuel cell. In Scenario C, solar radiation is converted by photovoltaic cells to electricity which is stored in different types of batteries. Scenario D combines a methanol steam reformer heated by solar power with a PEM fuel cell to generate electricity. The reformate gas mixture can be stored at elevated pressure in a gas tank. In contrast to routes A–C, scenario D has two exergy inputs: Solar radiation and chemical exergy in form of methanol as fuel. All systems are analyzed for an average day in July and February in Central California, including a storage device sufficient to store the energy for one week. Scenario D reaches an overall exergetic efficiency of more than 25% in summer at the expense of an additional exergy input in the form of methanol. The exergetic efficiency of scenario C amounts to 10–17% in summer (4–6% in winter) depending on the battery type and scenarios A and B achieve less than 10% efficiency even in summer. The systems of scenarios A and C would cost around $20k–$45k per 1 kW average electricity generation during the day in July. Scenario D leads to significantly lower costs and scenario B is the most expensive design due to the current immaturity of photoelectrolytic devices.

Commentary by Dr. Valentin Fuster
2010;():889-897. doi:10.1115/ES2010-90258.

In this paper, energy and exergy analyses of a trigeneration system based on an organic Rankine cycle (ORC) and a biomass combustor are presented. This trigeneration system consists of a biomass combustor to provide heat input to the ORC, an ORC for power production, a single-effect absorption chiller for cooling process and a heat exchanger for heating process. The system is designed to produce around 500 kW of electricity. In this study, four cases are considered, namely, electrical-power, cooling-cogeneration, heating-cogeneration and trigeneration cases. The effects of changing ORC pump inlet temperature and turbine inlet pressure on different key parameters have been examined to evaluate the performance of the trigeneration system. These parameters are energy and exergy efficiencies, electrical to cooling ratio and electrical to heating ratio. Moreover, exergy destruction analysis is presented to show the main sources of exergy destruction and the contribution of each source to the exergy destruction. The study shows that there are significant improvements in energy and exergy efficiencies when trigeneration is used as compared to electrical power. The results show that the maximum efficiencies for the cases considered in this study are as follows: 14.0% for electrical power, 17.0% for cooling cogeneration, 87.0% for heating cogeneration and 89.0% for trigeneration. On other hand, the maximum exergy efficiency of the ORC is 13.0% while the maximum exergy efficiency of the trigeneration system is 28.0%. In addition, this study reveals that the main sources of exergy destruction are the biomass combustor and ORC evaporator.

Commentary by Dr. Valentin Fuster
2010;():899-908. doi:10.1115/ES2010-90395.

Exergy is a thermodynamic concept that has been widely promoted for assessing and improving sustainability, notably in the characterization of resources and wastes. Despite having notable benefits, exergy is often misused by authors who tend to apply it as an intrinsic characteristic of an object (i.e., as a static thermodynamic property). Using both theoretical and empirical evidence the authors introduce the challenges involved with applying exergy as an intrinsic characteristic matter with particular focus on resource value and waste impact. These challenges lead to an in-depth discussion of current major reference environment formulations and reveals that the properties of exergy reference environments are not reconcilable with the properties of the natural environment. The authors conclude by arguing that exergy practitioners should abandon attempts to formulate standard comprehensive reference environments and return to process dependent reference environments that exergy was originally based upon. In this regard, the authors are proposing that exergy be seen as a context- or environment-dependent decision-making tool and not as an intrinsic characteristic of matter.

Commentary by Dr. Valentin Fuster

Geothermal Energy, Ocean Energy and Other Emerging Technologies

2010;():909-916. doi:10.1115/ES2010-90048.

The wind energy available over the globe’s vast ocean areas offers the opportunity to make a decisive contribution to the solution of the energy and climate crisis. In this paper we propose the use of sailing ships equipped with hydropower generators to convert the ocean wind energy into electricity. We describe a new oscillating-foil hydropower generator to achieve this objective. Our preliminary performance estimates indicate the feasibility of generating at least one megawatt of electrical power output per ship for electrolytic conversion of sea water into hydrogen and oxygen. Tests of a small-scale prototype confirmed the expected operational characteristics of the new generator.

Commentary by Dr. Valentin Fuster
2010;():917-927. doi:10.1115/ES2010-90069.

Survivability is a term that is widely used in the ocean wave energy industry, but the term has never been defined in that context. The word itself seems to have an intrinsic meaning that people understand; this fact often leads to the term’s misuse and its confusion with “reliability”. In order to design systems that are capable of long term survival in the ocean environment, it must be clear what “survivability” means and how it affects the design process and ultimately the device being deployed. Ocean energy is relatively predictable over the span of months, days, and even hours, which makes it very promising as a form of renewable energy. However, the variation of the energy content of ocean waves in a given location is likely high due to the effect of storms and the seasons. Wave energy converters must be built to be reliable while operating and survivable during severe conditions. Therefore, probabilistic design practices must be used to insure reliability and survivability in conditions that are constantly changing. Reliability is used to numerically express the failures of a device that occur while the system is operational, and it is usually expressed in terms of the mean time between failure (MTBF). However, in the context of ocean wave energy converters, the devices are likely to be continuously deployed in conditions that push them beyond their operating limits. During these times it is likely that wave energy converters will be placed in some sort of “survival mode” where the device sheds excess power, reducing system loading. Survivability is focused specifically on failures that occur during these times, when the device is experiencing conditions that surpass its operational limits. Developing a highly survivable wave energy converter is an outstanding goal, but without a standard definition of the term survivability, progress towards that goal cannot be measured. The purpose of this paper is to provide an initial definition for survivability, and to introduce a simple metric that provides an objective comparison of the survivability of varying wave energy converter technologies.

Topics: Ocean energy
Commentary by Dr. Valentin Fuster
2010;():929-936. doi:10.1115/ES2010-90394.

Renewable Energy has a crucial interest for a remote area like Reunion Island. The supply of electricity based on renewable energy has many advantages but the major drawback is the production of electricity which varies highly according to the availability of the resource (wind, solar, wave, etc...). This causes a real problem for non interconnected electrical grid where intermittent renewable energies should be limited to a maximum of 30%. The ocean Thermal Energy Conversion (OTEC) provides an alternative of electricity production from the available energy of the oceans present all the time. By using surface hot water and deep cold water from the ocean, it is possible to operate a thermodynamics cycle, which will then generate electricity. In this article, in the first part a literary and technological review is carried out in two areas: electricity production and cooling of buildings with deep water. This study establishes a knowledge base on thermodynamic cycles consistent with the OTEC and on dimensional and functional parameters associated with this technology. Steady state simulations are presented to understand the operation of the system. Steady state models will evaluate the potential of the OTEC in distributing base electricity. These simulations will help evaluating the potential for new thermodynamic cycles such as the Kalina cycle. With these tools, a sensitivity study will evaluate the influence of different parameters on the cycle.

Commentary by Dr. Valentin Fuster

Thermoeconomic Analysis

2010;():937-943. doi:10.1115/ES2010-90143.

In January 2008 the Governor of Hawaii announced the Hawaii Clean Energy Initiative; an initiative that aims to have at least 70 percent of Hawaii’s power come from clean energy by 2030 [4]. In July 2009, the Hawaii Department of Accounting and General Services awarded NORESCO, an energy service company, a $33.9M contract to improve the energy efficiency of 10 government buildings. The avoided utility cost of the energy and water savings from the improvements is the project funding mechanism. The energy savings realized by the project will reduce carbon dioxide emissions associated with utility power generation. However, as renewable energy becomes a larger portion of the utility generation profile through the Hawaii Clean Energy Initiative, the carbon dioxide emissions reductions from specific energy efficiency measures may erode over time. This work presents a method of analysis to quantify the carbon dioxide emissions reduction over the life of a project generated by energy efficiency upgrades that accounts for both the impact of policy initiatives and climate change using DOE-2/eQUEST. The analysis is based on the fact that HVAC energy usage will vary with climate changes and that carbon dioxide emission reductions will vary with both energy savings and the corresponding utility’s power generation portfolio. The energy savings related to HVAC system energy efficiency improvements are calculated over the life of a 20 year performance contract using a calibrated DOE-2/eQUEST model of an existing building that utilizes weather data adjusted to match the predictions of the Intergovernmental Panel on Climate Change. The carbon dioxide emissions reductions are calculated using the energy savings results and a projection of the implementation of the Hawaii Clean Energy Initiative. The emissions reductions are compared with other analysis methods and discussed to establish more refined expectations of the impact of energy efficiency projects in context with climate changes and policy initiatives.

Commentary by Dr. Valentin Fuster
2010;():945-951. doi:10.1115/ES2010-90145.

An attempt is made to utilize exhaust gases of a small gas turbine in augmenting power output through the employment of a thermoacoustic system. It is assumed that the thermoacoustic system is powered only by the waste heat of the gas turbine. A comprehensive cycle analysis of the integrated gas turbine thermoacoustic engine “IGTTE” is carried out from energy and exergy point of view. Results indicate the thermodynamic advantages of the IGTTE.

Commentary by Dr. Valentin Fuster
2010;():953-958. doi:10.1115/ES2010-90279.

This work describes the thermoeconomic study of an integrated combined cycle parabolic trough power plant. The parabolic trough plant will economize boiler activity, and thus the thermoeconomic optimization of the configuration of the boiler, including the parabolic trough plant, will be achieved. The objective is to obtain the optimum design parameters for the boiler and the size of the parabolic field. The proposal is to apply the methodology employed by Duran [1] and Valdés et. al. [2], but with the inclusion of the parabolic trough plant into the optimization problem. It is important to point out that the optimization model be applied to a single pressure level configuration. For future works, it is proposed that the same model be applied to different configurations of integrated combined cycle solar power plants. As a result the optimum thermoeconomic design will be obtained for a parabolic trough plant used to economize the HRSG.

Commentary by Dr. Valentin Fuster
2010;():959-967. doi:10.1115/ES2010-90408.

A renewable or “clean” energy system pays back the user in three ways. First, it typically avoids the use of hydrocarbon fuel, so for every kilowatt-hour or BTU that it produces it displaces or avoids a quantity of CO2 emission due to combustion of hydrocarbon. Second, the system requires an energy investment during its manufacture, so the embodied energy is paid back over its life cycle, and this aspect of renewable energy systems is often analyzed in standardized life cycle analyses. Third, the system represents a financial investment that should be preferably paid back before the end of the system life in order for the investment to be profitable. Deterministic assessments may inaccurately assess variables that can affect the ROI in any of these three categories, such as resource availability, equipment reliability or failure, and efficiency factors. Probabilistic modeling, on the other hand, can account for some of this uncertainty and reflect the uncertainty in the output. Use of this modeling technique will be demonstrated via examples to show how feasibility or ROI projections can be augmented with the use of probabilistic models.

Commentary by Dr. Valentin Fuster
2010;():969-978. doi:10.1115/ES2010-90414.

Business investments rely on creating a whole system of different parts, technologies, field and business operations, management, land, financing and commerce using a network of other services. Using the example of a wind farm development, a typical life cycle assessment (LCA) focuses upon the primary technology inputs and their countable embodied direct impacts. What LCA omits are the direct and indirect impacts of the rest of the business system that operates the primary technology, the labor, commerce and other technology employed. A total environmental assessment (TEA) would include the physical costs to the environment of the labor, commerce and other technology too. Here a simplified “system energy assessment” (SEA) is used to combine a “top-down” method of measuring implied indirect business impacts using econometric methods, with a “bottom-up” method of adding up the identifiable direct impact parts. The top-down technique gives an inclusive but rough measure. The bottom-up technique gives a precise accounting for the directly identifiable individual parts that is highly incomplete. SEA allows these two kinds of measures to be combined for a significantly improved understanding of the whole business system and its impacts, combining the high and low precision measures indentified by each method. The key is exhaustively accounting for energy uses within the natural boundary of a whole business system as a way of calibrating the measure. That allows defining a standardized measure of complex distributed system energy flows and their energy returns on invested energy resources (EROI). The method is demonstrated for a generic business operation. Starting from the easily accountable inputs and outputs, SEA successively uses larger natural system boundaries to discover a way of finding the limiting value of EROI after all parts of the whole are included. Some business choices and a net present value model of cash flow for the 20 year project help illustrate the related financial issues. The business model used shows that the EROI of a generic “Texas Wind Farm” is 31 when accounting for direct and indirect fuels only, but decreases to 4–6 after accounting for the economic energy consumed by all necessary business units and services.

Commentary by Dr. Valentin Fuster

Low/Zero Energy Buildings

2010;():979-984. doi:10.1115/ES2010-90035.

Phase Change Material (PCM) plays an important role as a thermal energy storage device by utilizing its high storage density and latent heat property. One of the potential applications of the PCM is in buildings by incorporating them in the envelope for energy conservation. During the summer cooling season, the main benefits are a decrease in overall energy consumption by the air conditioning unit and the time shift in peak load during the day. Experimental work was carried out by Arizona Public Service (APS) in collaboration with Phase Change Energy Solutions (PCES) Inc. with a new class of organic-based PCM. The experimental setup showed maximum energy savings of about 30%, a maximum peak load shift of ∼ 60 min, and maximum cost savings of about 30%.

Commentary by Dr. Valentin Fuster
2010;():985-991. doi:10.1115/ES2010-90036.

The reduction of anthropogenic green house gas emissions through increased building energy efficiency is a global effort, which is a responsibility of both developed and developing nations. The Passive House concept is a building design methodology that advocates for a systematic optimization and integration of the building envelope and internal loads in order to achieve a passive yet comfortable performance. Multiple passive houses have been built and monitored in Europe and the United States. The present paper attempts to determine what design features are required for tropical residential buildings to meet the Passive House Standard. This study was conducted in El Salvador, which experiences a warm and humid climate throughout the year. For economic and cultural reasons, few residential buildings in the country have air conditioning systems. However, the vast majority of residential buildings have not been designed using passive principles, causing great occupant discomfort and increasing energy consumption for cooling. Both the Passive House Planning Package (PHPP) software and EnergyPlus were used in order to determine the design parameters that would yield a passive house for this climate. In addition, the paper discusses the technical and economic feasibility of modifying a typical house to meet the standard. The potential benefits related to occupant comfort and energy cost savings are also discussed.

Commentary by Dr. Valentin Fuster
2010;():993-997. doi:10.1115/ES2010-90075.

We analyze the operating-energy histories of three homes of different ages that have approached or attained net-use of no fossil fuels and climate neutrality. The first house (H-60) with 1,200 ft2 is a conventional 1950s house that has been caulked, insulated and equipped with an airtight woodstove and a 3.3 kW photovoltaic system that reduced its annual use of fossil fuels by 86%. Its total annual energy use excluding any passive gain is ∼57 billion joules. House two (H-30) with 2,300 ft2 is a 1980s, passive-solar house with a recently added 4.0 kW photovoltaic system that reduced its annual use of fossil fuels by 71%. Its total annual energy use excluding any passive gain is ∼58 billion joules. House three (H-1) with 1,300 ft2 is a 1 year old, passive solar house with a 3.1 kW photovoltaic system and an evacuated-tube solar hot water system that uses no fossil fuels, exports annually ∼900 kWh to the grid making it energy and climate positive, and provides all operating energy from on-site sunshine. Its total annual energy use excluding any passive gain is ∼29 billion joules.

Topics: Climate
Commentary by Dr. Valentin Fuster
2010;():999-1008. doi:10.1115/ES2010-90141.

In spite of heightened interest in anthropogenic climate change, little attention has been paid to optimizing a building’s carbon emissions at the source. Most work in building efficiency has assumed that generating plant carbon emissions are constant at their long-term average values. This study sought to improve our understanding of the temporal variations in carbon emissions on a diurnal time scale and their relation to electric system dispatch and load in order to motivate future work in optimizing building operation to reduce carbon emissions. Hourly fossil fuel plant emissions and load data, available from the EPA, were used to characterize power system performance for four US locations (IL, NY, TX, and CA). The study had set out with a hypothesis hoping to find a simple relationship between electric system load and emissions. It was found that there is a significant correlation between increased system load and decreased emissions rates, yet this correlation is not easily defined. During high load conditions, emissions reductions are related to the increased use of gas generators, or may be related to operating plants at more efficient part load ratios. The work conducted in this study shows that, while more complex than hoped for, there is indeed a strong relationship between electric system load and carbon emissions rates.

Commentary by Dr. Valentin Fuster
2010;():1009-1017. doi:10.1115/ES2010-90225.

Until recently, large-scale, cost-effective net-zero energy buildings (NZEBs) were thought to lie decades in the future. However, ongoing work at the National Renewable Energy Laboratory (NREL) indicates that NZEB status is both achievable and repeatable today. This paper presents a definition framework for classifying NZEBs and a real-life example that demonstrates how a large-scale office building can cost-effectively achieve net-zero energy. The vision of NZEBs is compelling. In theory, these highly energy-efficient buildings will produce, during a typical year, enough renewable energy to offset the energy they consume from the grid. The NREL NZEB definition framework classifies NZEBs according to the criteria being used to judge net-zero status and the way renewable energy is supplied to achieve that status. We use the new U.S. Department of Energy/NREL 220,000-ft2 Research Support Facilities (RSF) building to illustrate why a clear picture of NZEB definitions is important and how the framework provides a methodology for creating a cost-effective NZEB. The RSF, scheduled to open in June 2010, includes contractual commitments to deliver a Leadership in Energy Efficiency and Design (LEED) Platinum Rating, an energy use intensity of 25 kBtu/ft2 (half that of a typical LEED Platinum office building), and net-zero energy status. We will discuss the analysis method and cost tradeoffs that were performed throughout the design and build phases to meet these commitments and maintain construction costs at $259/ft2 . We will discuss ways to achieve large-scale, replicable NZEB performance. Many passive and renewable energy strategies are utilized, including full daylighting, high-performance lighting, natural ventilation through operable windows, thermal mass, transpired solar collectors, radiant heating and cooling, and workstation configurations allow for maximum daylighting. This paper was prepared by the client and design teams, including Paul Torcellini, PhD, PE, Commercial Building Research Group Manager with NREL; Shanti Pless and Chad Lobato, Building Energy Efficiency Research Engineers with NREL; David Okada, PE, LEED AP, Associate with Stantec; and Tom Hootman, AIA, LEED AP, Director of Sustainability with RNL.

Topics: Structures , Roads
Commentary by Dr. Valentin Fuster
2010;():1019-1028. doi:10.1115/ES2010-90266.

We describe a method to generate statistical models of electricity demand from Commercial and Industrial (C&I) facilities including their response to dynamic pricing signals. Models are built with historical electricity demand data. A facility model is the sum of a baseline demand model and a residual demand model; the latter quantifies deviations from the baseline model due to dynamic pricing signals from the utility. Three regression-based baseline computation methods were developed and analyzed. All methods performed similarly. To understand the diversity of facility responses to dynamic pricing signals, we have characterized the response of 44 C&I facilities participating in a Demand Response (DR) program using dynamic pricing in California (Pacific Gas & Electric’s Critical Peak Pricing Program). In most cases, facilities shed load during DR events but there is significant heterogeneity in facility responses. Modeling facility response to dynamic price signals is beneficial to the Independent System Operator for scheduling supply to meet demand, to the utility for improving dynamic pricing programs, and to the customer for minimizing energy costs.

Topics: Signals
Commentary by Dr. Valentin Fuster
2010;():1029-1039. doi:10.1115/ES2010-90335.

Essential to the development of a low carbon economy will be the advancement of building product and process to reduce the capital and whole lifecycle cost of low, zero and net-positive energy buildings to allow these structures to be realized at a greater rate. On the whole, the built environment is responsible for one of the largest fractions of global energy consumption and thus anthropomorphic climate change, a result of the greenhouse gas emissions from power generation. When one also considers the energy required to design, fabricate, transport and construct the materials necessary to bring new building stock online, keeping pace with the rapid trend towards urbanization, the importance of the built environment in the energy sustainability equation is clearly evident. Yet, while technologically feasible, the realization of carbon neutral buildings is encumbered by the perception of increased annualized costs for operation and a greater upfront investment. This paper will review the design case of the Masdar International Headquarters, the flagship building of the net-zero carbon emission Masdar city currently being developed within the Abu Dhabi Emirates. Specifically, how an integrated approach enabled by computer simulation early within the design process allowed for improvements in economy and efficiency, setting a model for future high performance buildings. The five-story, 89,040-square-meter office building will incorporate eleven sculpted glass environmental towers to promote natural ventilation and introduce daylight to the interior of the building. These towers will also serve as the structural support for one of the world’s largest building integrated photovoltaic arrays, sized to supply 103% of the building’s total annual energy requirements while protecting the building and roof garden from intense heat and solar gains. Moreover, by integration into a separate structural trellis system, clean energy can potentially be generated to offset construction requirements while dually shading workers below during the heat of the day. This, along with other key sustainability design strategies such as a solar powered central district cooling system, thermoactive foundation piling, underfloor air distribution, desiccant dehumidification, a nanotechnology enabled building envelope and smart grid enabled facilities management infrastructure will allow the Masdar Headquarters to reach carbon neutrality within a decade, allowing for the remaining century of its operation to serve as a platform for clean energy generation.

Topics: Structures , Carbon
Commentary by Dr. Valentin Fuster
2010;():1041-1046. doi:10.1115/ES2010-90355.

This paper summarizes the results of a detailed energy analysis carried out for a typical Colorado residence using three different HVAC systems for 10 distinct locations in Colorado. The HVAC systems considered in the analysis include: • 78% efficient furnace with a 13 SEER air conditioner; • Vertical well ground source heat pump with a heating COP of 3.5 and a cooling EER of 17.1; • Slinky ground source heat pump with a heating COP of 3.5 and a cooling EER of 17.1. The results of the analysis indicate that relative to the conventional systems, ground source heat pumps (GSHPs) offer several benefits including lower annual energy costs, electrical peak demand, and carbon emissions. However, GSHPs use more electrical energy use. Specifically, it was found that relative to a 78 AFUE furnace / 13 SEER AC system, in all locations both GSHPs, vertical well and slinky, show on average a 41.2% increase in electricity use, a 10% decrease in energy cost, a 4.5% decrease in CO2 emissions, and a 16.8% average decrease in peak summer electric demand.

Commentary by Dr. Valentin Fuster
2010;():1047-1054. doi:10.1115/ES2010-90370.

Using Computational Fluid Dynamics (CFD) software, three different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare arrangements for (a) an all-air overhead system (mixing ventilation), (b) an all-air raised floor system (displacement ventilation), and (c) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one isothermal wall (simulating an exterior wall of the room) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations were conducted. The first set of computations utilized a constant temperature isothermal exterior wall, while the second set utilized an isothermal wall that changed temperatures as a function of time simulating the temperature changes on the exterior wall of a building throughout a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation, especially the displacement ventilation with a chilled ceiling over the conventional mixing ventilation system.

Commentary by Dr. Valentin Fuster
2010;():1055-1061. doi:10.1115/ES2010-90387.

This paper deals with the construction and implementation of the Off-Grid Zero Emissions Building (OGZEB), a project undertaken by the Energy Sustainability Center (ESC), formally the Sustainable Energy Science and Engineering Center (SESEC), at the Florida State University (FSU). The project involves the design, construction and operation of a completely solar-powered building that achieves LEED-NC (Leadership in Energy and Environment Design-New Construction) platinum certification. The 1064 square foot building is partitioned such that 800 square feet is a two bedroom, graduate student style flat with the remaining 264 square feet serving as office space. This arrangement allows the building to serve as an energy efficient model for campus designers in student living and office space. The building also serves as a prototype for developing and implementing cutting edge, alternative energy technologies in both residential and commercial settings. For example, hydrogen is used extensively in meeting the energy needs of the OGZEB. In lieu of high efficiency batteries, the excess electricity produced by the buildings photovoltaic (PV) panels is used to generate hydrogen via water electrolysis for long term energy storage. The hydrogen is stored on-site until needed for either generating electricity in a Proton Exchange Membrane (PEM) fuel cell stack or combusted in natural gas appliances that have been modified for hydrogen use. The use of hydrogen in modified natural gas appliances, such as an on-demand hot water heater and cook top, is unique to the OGZEB. This paper discusses the problems and solutions that arose during construction and includes detailed schematics of the OGZEBs energy system.

Commentary by Dr. Valentin Fuster
2010;():1063-1071. doi:10.1115/ES2010-90504.

Chinese Kang with two thousand years’ history is a typical heating method using biomass in cold rural areas. It contributes to reducing the demands of coal and to optimizing the energy consumption structure, but its development is limited for low energy efficiency, poor indoor environment and etc. Therefore, we had a study based on experiment on a new reformed hot-wall Kang. The experimental results show that: the hot-wall Kang improved indoor thermal environment to a great extent. The radiation was the main way of heat elimination through the Kang’s surface, and took up about 65% of the total heat supply. The total heat carried by gas was gained by Kang body and chimney, 64.6% and 9.1% respectivley, and the remaining 26.3% was lost by discharged gas. Under the operation simulating residents’ living habit, the heating efficiency of Kang was up to 80.5% in the period of one testing day. The heat loss transferred to the ground through Kang cave and Hot-wall combustion space was 3.17% and 8.27% respectely. It also showed that the dust-ash layer filled in the cave weakened the ground heat loss and had same effect as that of insulation. Other discoveries: the mass flow rate of flue gas during the burning periods varied in the range of 0.04∼0.08 kg/s. It was turbulent flow at a low velocity, companied with two gas temperature layers. Based on the experiment, the thermal and operation character of hot-wall Kang were made clear. Furthermore, a guide for further optimization of the structure was put forward. And the results also supplied some proofs for the study of gas flow and heat transfer with natural ventilation.

Commentary by Dr. Valentin Fuster

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