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ASME Conference Presenter Attendance Policy and Archival Proceedings

2011;():i. doi:10.1115/ES2011-NS.
FREE TO VIEW

This online compilation of papers from the ASME 2011 5th International Conference on Energy Sustainability (ES2011) represents the archival version of the Conference Proceedings. According to ASME’s conference presenter attendance policy, if a paper is not presented at the Conference, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in the ASME Digital Library and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Advances in Solar Buildings and Conservation; Climate Control and the Environment; Solar Heating and Cooling

2011;():1-6. doi:10.1115/ES2011-54017.

The application of greenhouse technology for cultivation of high value crops is rapidly expanding worldwide. But the requirement of electricity imposes a restriction on the emanation of this technology to areas which are remote. In a developing country like India, where a significant number of villages are yet to be connected to any national or regional grid, this restriction assumes considerable significance. The present paper has been divided into two parts: The first part dealing with the performance analysis of a floriculture greenhouse located in the plains of Indian subcontinent equipped with fan induced ventilation system and wet pad along with shading screens. The second part deals with the performance analysis of the greenhouse integrated power system comprising of solar photovoltaic array, electrolyser and fuel cell stacks. The hourly photovoltaic generation, load consumption, cumulative daylong hydrogen gas generation and consumption have been computed for various seasons of a climatic cycle and presented in this paper.

Topics: Fuels , Solar energy
Commentary by Dr. Valentin Fuster
2011;():7-11. doi:10.1115/ES2011-54029.

The fundamentals of how PCM materials works need more consideration. It has been reported that using PCM materials may reduce the cooling/heating loads in buildings. PCM can only affect the fluctuation of the load and not the magnitude of the load. Thus PCM materials should be considered as an energy management tool only. For PCM to operate effectively the cycle of charging and discharging of PCM material should be completed over the period of the day, i.e. PCM must be melted and solidified over the 24 hrs of the day. Using the appropriate amount of the PCM will maximize its usage. Fewer amounts will show more fluctuation in the load and larger amount will be a waste without benefit. The appropriate amount for an application is found to be function of PCM properties, k, Cp, density and melting temperature. For PCM to complete the whole cycle in a day period melting temperature need to be near the average between the indoor and outdoor design temperature of the conditioned space. In this investigations a one dimensional model were investigated and solved numerically using finite difference technique. The effect of the amount of PCM material on load fluctuation is calculated and presented. Packing capsulated PCM material of linearly varying melting temperatures is found to maximize the effectiveness of the technique.

Topics: Structures
Commentary by Dr. Valentin Fuster
2011;():13-22. doi:10.1115/ES2011-54043.

A model for the combined spectral radiative and convective heat transfer analysis of solar chimneys is developed. The radiation part of this model is based on the spectral distribution of the solar heat flux and spectral radiative properties solar chimney components. Two methods are used for the convective part of this model, empirical correlations and a CFD analysis. The empirical correlations consist of stack effect correlation for air flow motion and convective heat transfer correlation for heat transfer coefficient calculations. The empirical correlations were used to obtain an initial estimation of surface temperatures which were then used in a CFD model to determine an improved estimation of the heat transfer coefficients and flow rates. By iterating between the spectral radiative and CFD models a converged value for the solar chimney flow rate and its thermal characteristics is obtained. The model is used to predict the volume flow rate of air moved for various configurations of solar chimneys (slopes and air gap distance).

Commentary by Dr. Valentin Fuster
2011;():23-28. doi:10.1115/ES2011-54052.

Composite adsorbents synthesized from zeolite 13X and CaCl2 were investigated for applications in solar adsorption systems. The effect of Ca-ion-exchange on the adsorption properties of zeolite 13X was studied. Sodium ions in the zeolite structure were replaced by calcium ions by ion exchange. It was found that the Ca-ion-exchange process decreased the specific surface areas of the Ca-ion-exchanged zeolites while the total pore volumes were increased. The optimized Ca-ion-exchange condition existed when soaking zeolite 13X in 46wt% CaCl2 solution for 36 hours. The increase in the total pore volume is good for further impregnating the zeolite with CaCl2 . A large difference in equilibrium water uptake, 0.404g/g, between 25°C and 100°C under 870Pa was recorded for the 13X/CaCl2 composite adsorbent impregnated in 40wt% CaCl2 solution. This was 295% of that of zeolite 13X under the same condition. The 13X/CaCl2 composite adsorbent showed a high potential in replacing vapor compression chillers in producing chilled water for central air-conditioning systems.

Commentary by Dr. Valentin Fuster
2011;():29-34. doi:10.1115/ES2011-54056.

In this paper, we will present a method for estimating the stored thermal energy in a building wall that is adjacent to an unglazed transpired collector. We also discuss how this value should be incorporated in the collector efficiency calculations. An unglazed transpired collector is made of a relatively thin, dark, perforated metal wall that is installed approximately 14 inches (35.5 cm) away from a south facing building wall to create an enclosed plenum. Typically, the outside air is drawn into the collector by fans that are located on the top of the collector. These types of solar collectors are used to preheat the intake air using solar energy before the air enters existing HVAC systems. They are generally used in situations and buildings where large ventilation volume flow rates are required. Most of the studies related to unglazed transpired collectors deal with estimation of air temperature rise due to solar gain and recaptured heat loss from the adjoining building wall. In the past, studies have neglected the amount of thermal energy that is stored in the building wall. However, as shown in this study, the stored thermal energy is of significant amount, and if incorporated correctly in the collector efficiency calculations, it would lead to higher efficiency values.

Commentary by Dr. Valentin Fuster
2011;():35-40. doi:10.1115/ES2011-54063.

Heating, Ventilating, and Air Conditioning Systems (HVAC) consume nearly one-third of household energy in the United States. The optimization of the control parameters in HVAC equipment allows for a reduction in energy consumption. In this study, a supervisory control method is applied to a lumped parameter model of an HVAC system of interest containing a chiller and three dampers. The method determines the choice of control parameters that minimize the energy consumption for 1000 sampled steady-state loads. An energy savings of 39% was achieved using the method in this study compared to the base case.

Commentary by Dr. Valentin Fuster
2011;():41-46. doi:10.1115/ES2011-54065.

An irreversible solar powered absorption refrigeration system is put forward, in which finite-rate heat transfer with the convection mode from the solar collector to the absorption refrigerator and the radiation-convection heat loss from the solar collector to the ambient, the internal irreversibility inside the working fluid are taken into account. On the basis of thermodynamic analysis and log mean temperature difference (LMTD) methods, the expression between the overall coefficient of performance (COP) of the solar powered absorption refrigeration system and the operating temperature of the solar collector is derived. The influences of heat loss of the solar collector, the irreversibility inside the working fluid, the isobaric temperature ratio, the ratio of heat-transfer coefficients on the optimal performance characteristic of the solar powered absorption refrigeration system are revealed. The results obtained in the present paper are helpful to the optimal parameter design of actual solar powered absorption refrigerators.

Commentary by Dr. Valentin Fuster
2011;():47-55. doi:10.1115/ES2011-54079.

Using Computational Fluid Dynamics (CFD), four 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) a combined air and hydronic radiant system (overhead system with a chilled ceiling), (c) an all-air raised floor system (displacement ventilation), and (d) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall to compare the four cooling systems. The second set of computations consider a glass window, a phase change material layer and the plastic shade configuration for the exterior wall to examine the effect of the phase change material (PCM) layer on the cooling energy requirements. Both sets of simulations assumed an external wall that changed temperature as a function of time simulating the temperature changes on the exterior wall of the room during a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

Commentary by Dr. Valentin Fuster
2011;():57-61. doi:10.1115/ES2011-54114.

This paper presents the physical design and experiments of the Concentrating Transpired Air Heating (CTAH) system as a combination of subsystems of parabolic primary and circular secondary reflector that concentrates incident solar radiation onto an inverted perforated absorber. Optical efficiency of the CTAH system has been analysed using a 2D ray tracing model. Experiments have been carried out for 50% perforated black painted aluminium inverted absorber for glazed and unglazed systems. Results show a significant temperature rise of the absorber surface in both cases. The maximum temperature of the absorber for the unglazed system is 52.1°C at 22.5°C ambient temperature, where as for the covered system, it is 67.9°C at 23.2°C ambient temperature.

Topics: Design , Heating
Commentary by Dr. Valentin Fuster
2011;():63-70. doi:10.1115/ES2011-54127.

A novel building façade surface configuration is proposed. This façade consists of grooved cavities that are configured in a manner that reflects summer (cooling season) insolation and absorbs winter (heating season) insolation. The effective absorptivities of the façade for various cavity reflectance characteristics, i.e., a wide range of diffuse and specular reflectance characteristics, are evaluated using a Monte Carlo model. It was determined the best cavity surface reflectivity is the one with fully diffuse surfaces and absorptivity of 0.7 or more. This reflectance characteristic of cavity results in a small depth of façade cavity and thicker divider fin between two adjacent cavities. The calculations in the present work are performed for the latitude of 41°N where both heating and cooling loads are significant. The same model can be applied to locations with different latitude which may result in slightly different cavity configurations and effective absorptivities.

Commentary by Dr. Valentin Fuster
2011;():71-78. doi:10.1115/ES2011-54129.

Cross ventilation is a more effective ventilation strategy in comparison to single-sided ventilation. In the NSW Residential Flat Design Code1 (RFDC) the majority of apartments are required to adopt cross ventilation. However, in the case of studio and one-bedroom apartments, it is acknowledged that single-sided ventilation may prevail. Deep plan studio and one-bedroom apartments may achieve lower amenity of summer thermal comfort and indoor air quality where mechanical ventilation is not provided by air conditioning. Since compliance with the code may allow up to 40% of apartments in a development in Sydney to be single sided, it is important to understand the natural ventilation performance of such apartments. The objective of this paper is to investigate the natural ventilation potential in single-sided ventilated apartments to improve indoor air quality and thermal comfort. This investigation includes simulating various facade treatments involving multiple opening and balcony configurations. Balcony configurations are included in this study because, in Sydney, a balcony is a compulsory architectural element in any apartment building. The study uses computational fluid dynamics (CFD) software to simulate and predict the ventilation performance of each apartment configuration. This study suggests that properly configured balconies and openings can significantly improve indoor ventilation performance for enhanced indoor air quality and thermal comfort, by optimizing the available prevailing wind. However, it is important to note that inappropriately designed façade treatments also could diminish natural ventilation performance.

Commentary by Dr. Valentin Fuster
2011;():79-84. doi:10.1115/ES2011-54130.

Anthropogenic production of cold is necessary for the preservation of the food industry, industrial processes, ice making, refrigeration and domestic conditioning of fixed and mobile spaces, emphasizing the importance in the health sector for the preservation of vaccines, biological and vital organs. Al ready exist technology who use power supply to produce cold, causing global warming as part of the side effect of CO2 from burning fossil fuel for power plants. Currently being researched and developed alternative technology that who operates with solar energy and requires no power supply. The market is looking for competitive cooling technologies operating systems generally, to raise the development of a solar refrigerator design for hot humid climate in Mexico, for the most critical environmental conditions of sunlight in a highly demanding cold technology.

Topics: Solar energy
Commentary by Dr. Valentin Fuster
2011;():85-90. doi:10.1115/ES2011-54162.

The Energy Information Administration of the United States Department of Energy projects that more than 80% of the energy consumption of the U.S. by 2035 will come from fossil fuels. This projection should be the fuel to promote projects related to renewable energy in order to reduce energy consumption from fossil fuels to avoid their undesirable consequences such as carbon dioxide emissions. Since solar radiation match pretty well building cooling demands, solar cooling systems will be an important factor in the next decades to meet or exceed the green gases reduction that will be demanded by the society and regulations in order to mitigate environmental consequences such as global warming. Solar energy can be used as source of energy to produce cooling through different technologies. Solar thermal energy applies to technology such as absorption chillers and desiccant cooling, while electricity from solar photovoltaic can be used to drive vapor compression electric chillers. This study focuses on the comparison of a Solar Thermal Cooling System that uses an absorption chiller driven by solar thermal energy, and a Solar Photovoltaic Cooling System that uses a vapor compression system (electric chiller) driven by solar electricity (solar photovoltaic system). Both solar cooling systems are compared against a standard air cooled cooling system that uses electricity from the grid. The models used in the simulations to obtain the results are described in the paper along with the parameters (inputs) used. Results are presented in two figures. Each figure has one curve for the Solar Thermal Cooling System and one for the Solar Photovoltaic Cooling System. One figure allows estimation of savings calculated based the net present value of energy consumption cost. The other figure allows estimating primary energy consumption reduction and emissions reduction. Both figures presents the result per ton of refrigeration and as a function of area of solar collectors or/and area of photovoltaic modules. This approach to present the result of the simulations of the systems makes these figures quite general. This means that the results can be used to compare both solar cooling systems independently of the cooling demand (capacity of the system), as well as allow the analysis for different sizes of the solar system used to harvest the solar energy (collectors or photovoltaic modules).

Commentary by Dr. Valentin Fuster
2011;():91-101. doi:10.1115/ES2011-54200.

The Earth is faced to decreasing of energy resources due to increasing of energy consumption. This reason accelerates the global warming which leads the Earth to a place in which quality of life is reducing year by year. A considerable portion of total energy consumption is used in residential sector in the world. The usage of energy in residential sector effectively ensures large amount of energy saving. Nowadays, the buildings have been aiming to design which consume low energy and supply high comfort. In order to design energy efficient buildings, all the designing parameters which include passive systems must be taken into consideration together considering versatile interior and exterior conditions. In this study the energy efficient building was described and the applications were explained for the sample building. The office building designed to obtain LEED certification was taken into consideration as a current application in Turkey and it was modeled using TRNSYS simulation program during the year. The heating and cooling loads were calculated. According to results some suggestions were recommended for reducing the heating and cooling demands of the office building and any suggestion was simulated and analyzed for the designed building.

Commentary by Dr. Valentin Fuster
2011;():103-111. doi:10.1115/ES2011-54254.

Concentrating solar thermal systems offer a promising method for large scale solar energy collection. It is feasible to use concentrating solar thermal systems for rooftop applications such as domestic hot water, industrial process heat and solar air conditioning for commercial, industrial and institutional buildings. This paper describes the thermal performance of a new low-cost solar thermal micro-concentrating collector (MCT), which uses linear Fresnel reflector technology and is designed to operate at temperatures up to 220°C. The modules of this collector system are approximately 3 meters long by 1 meter wide and 0.3 meters high. The objective of the study is to optimize the design to maximise the overall thermal efficiency. The absorber is contained in a sealed enclosure to minimise convective losses. The main heat losses are due to natural convection inside the enclosure and radiation heat transfer from the absorber tube. In this paper we present the results of a computational investigation of radiation and convection heat transfer in order to understand the heat loss mechanisms. A computational model for the prototype collector has been developed using ANSYS-CFX, a commercial computational fluid dynamics software package. Radiation and convection heat loss has been investigated as a function of absorber temperature. Preliminary ray trace simulation has been performed using SolTRACE and optical efficiency has been evaluated. Finally, the MCT collector efficiency is also evaluated.

Commentary by Dr. Valentin Fuster
2011;():113-118. doi:10.1115/ES2011-54256.

Transpired solar collectors are simple and cost-effective devices suited for preheating ventilation air for buildings. They work by drawing outside air through a south-facing perforated metal absorber. The absorber is heated by solar radiation, heat is transferred to the air as it is drawn through the perforations in the absorber, and the pre-heated air is delivered to the building. Often overlooked in the design of transpired collector systems is the effect on collector efficiency of pressure drop across the absorber. The pressure drop is a function of the air flow rate through the perforations, the overall porosity of the absorber, and the properties of the air. The National Renewable Energy Laboratory (NREL) conducted a series of laboratory tests to characterize the pressure drop as a function of the relevant parameters for six commercially-available absorber configurations; three porosities in aluminum and three in steel. Each absorber material is roll-punched to one of three depths to create absorbers with three different porosities. Pressure drop, air flow rate, air temperature, and air relative humidity data were collected during the tests. The data were fit to a model that can be used to predict pressure drop across the absorber as a function of air properties and flow rate. Use of these correlations is expected to aid designers in ensuring that transpired collector systems are designed for optimal thermal efficiency and cost effectiveness.

Commentary by Dr. Valentin Fuster
2011;():119-125. doi:10.1115/ES2011-54294.

The goal of the project is to evaluate various types of facades’ behavior and effects on building energy, focused primarily on building fenestrations such as windows. Development of the façade evaluation facility and requirements are presented in this paper. The test facility is a complete standalone unit designed to replicate a section of a building. Accommodation for facilitating a wide range of fenestrations was an important criterion. An effective solution was developed that allowed instant interchangeability of the façade setup. Although, due south orientated facades was of primary interest, integration of a rotating carousel base allowed flexibility in adjusting the orientation of the test facility. Experimental procedures and instrumentation layout are discussed in detail. The temperature of the indoor environment is continuously controlled and monitored. The measured fenestration characteristics include thermal and optical properties of the windows. The test results reveal the fenestration performance. The outcome of these tests enumerates the effects of the façade on the overall heating and cooling loads of buildings. Further investigation into these characteristics assists in improving building energy efficiency. Due to the versatility of the facility, quick replacement of the façade can accommodate several tests in short durations of time. Furthermore, correlation of the results can be scaled appropriately for residential or commercial settings providing practical information for wide utilization, contingent upon the window type.

Commentary by Dr. Valentin Fuster
2011;():127-136. doi:10.1115/ES2011-54296.

Evaporative cooling is among the most cost effective methods of air conditioning, but is less efficient in humid climates. An evaporative system coupled with a desiccant wheel can operate effectively in broader climatic conditions. These cooling systems can substitute traditional vapor compression air conditioning systems as they involve environmentally friendly cooling processes with reduced electricity demand (which is commonly generated from fossil fuels) along with no harmful CFC based refrigerant usage. Furthermore, direct utilization of low grade energy sources such as solar thermal energy or flue gas heat can drive the desiccant regeneration process, thus providing economic benefits. This study presents the results of simulations of desiccant cooling system performance for different climate zones of the United States. Solar assisted desiccant air conditioning is particularly useful where there are abundant solar resources with high temperature and humidity levels. Building energy simulations determined cooling energy requirements for the building. Simulation of an evacuated solar hot water collector model provided the heat energy available for regeneration of the desiccant. Solid desiccant of common material such as silica gel used in a rotary wheel is simulated using established validated computer models; this is coupled with evaporative cooling. Transients of the overall system for different cooling loads and solar radiation levels are presented. Finally, feasibility studies of the desiccant cooling systems are presented in comparison with traditional cooling system. Further analysis of the data presents optimization opportunities. Energy savings were achieved in all climatic conditions with decreased effectiveness in more humid conditions.

Commentary by Dr. Valentin Fuster
2011;():137-146. doi:10.1115/ES2011-54321.

The closed greenhouse concept has been studied in this paper. The closed greenhouse can be considered as the largest commercial solar building. In principle, it is designed to maximize the utilization of solar energy through seasonal storage. In an ideal fully closed greenhouse, there is not any ventilation window. Therefore, the excess heat must be removed by other means. In order to utilize the excess heat at a later time, long and/or short term thermal storage technology (TES) should be integrated. A developed model has been evaluated due to different situations. The closed greenhouse is compared with conventional greenhouse using a case study respect to the energy analysis. A parameter has been defined in this paper in order to compare performance of the closed greenhouse concept in different conditions. This parameter has been called ESR. Finally a preliminary thermo-economical study has been assessed in order to investigate on feasibility of the closed greenhouse concept.

Topics: Solar buildings
Commentary by Dr. Valentin Fuster
2011;():147-152. doi:10.1115/ES2011-54419.

While solar energy provides a source for passive space heating across a variety of climates, other ambient energy sources may be more appropriate for passive space cooling. These ambient resources include ambient air at dry-bulb and wet-bulb temperatures, ground temperature at locations where the soil is cooler than the indoor comfort temperature, and night-sky radiant temperature, which is substantially lower than ambient air in most climates. The focus of this study was on comparing these sources to cooling loads across climates in the US. Using a degree-day approach, annual cooling potentials were calculated for over 800 TMY3 locations. Color-themed maps for each ambient source at several indoor comfort temperature ranges were constructed as visual references for design purposes. In addition, eight US cities (Denver, CO, Los Angeles, CA, Louisville, KY, Madison, WI, Miami, FL, New Orleans, LA, Phoenix, AZ and Washington DC) were selected to represent a range of climate characteristics, including seasonal ambient temperature, diurnal temperature swings, humidity and sky clearness. For each city, an ambient potential to cooling load ratio (ALR) was calculated, with the potential based on an indoor comfort temperature range of 68°F – 72°F and the load calculated with a base temperature of 65°F. ALR, which neglects phase lags between source and load and the associated need for thermal storage, exceeded one for dry-bulb air and for ground temperature for all locations except Miami, New Orleans and Phoenix. Wet-bulb ALR exceeded one for all locations except Miami, and sky ALR exceeded one for all locations. Finally, the effect of limited thermal storage was estimated by calculating daily ambient source fraction, fas , which is the daily ambient cooling potential divided by the daily cooling load. fas thus approximates the cooling potential of systems with one day’s worth of thermal storage, and has an upper limit of one. Fas , the annual sum of fas , equaled one for ground temperature for Los Angeles and Madison and for sky temperature for Denver and Los Angeles. Fas for ground temperature was above 0.9 for all locations except Miami, New Orleans and Phoenix. Fas for sky temperature exceeded 0.6 for all locations. By utilizing all possible combinations of ambient sources, half of the selected locations attained Fas equal to one and the minimum for all locations still exceeded 0.65.

Topics: Cooling
Commentary by Dr. Valentin Fuster
2011;():153-158. doi:10.1115/ES2011-54421.

Solar energy could help to reduce the request of electric energy which is generated via hydrocarbons, having the possibility to provide energy to rural communities which do not have it through the conventional distribution. The application of solar system on refrigeration has a great range of development, that will have a competitive cost when the hydrocarbons diminish. An intermittent solar refrigerator that works with the absorption cycle is studied in the Center of Research on Energy of UNAM. It was designed to produce 8 kg of ice. The refrigerator consists of a condenser, an expansion valve, an evaporator and a generator/absorber. A compound parabolic concentrator (CPC) receives solar energy and turns into thermal energy. It is concentrated in the cylindrical receiver that works as generator or absorber. Being intermittent, the refrigerator performs two stages to complete a refrigeration cycle: a generation-condensation stage and another of evaporation-absorption stage. The present work focuses on the evaluation of the generation-condensation stage. One of the working mixture is ammonia-lithium nitrate (NH3 – LiNO3 ) that presents some advantages over the common mixtures such as the avoiding of rectification and working with relatively low manometric pressures. A disadvantage is that it presents crystallization at low concentrations. The other working mixture is ammonia-lithium nitrate-water (NH3 – LiNO3 – H2 O) with higher conductivity and lower viscosity than the ammonia/lithium nitrate. Several test were made at different solution concentrations for both mixtures, binary mixture (NH3 – LiNO3 ) and ternary mixture (NH3 – LiNO3 – H2 O). Comparing the performance of the system operating with the two mixtures, it was found that with the ternary mixture the solar coefficients of performance can be up to 24% higher than those obtained with the binary mixture.

Topics: Solar energy , Water
Commentary by Dr. Valentin Fuster
2011;():159-165. doi:10.1115/ES2011-54425.

The lighting systems of homes and workplaces today must be constantly redesigned to be environmentally friendly, sustainable, healthy and ergonomic. This requires maximizing the flow of daylight into indoors, minimizing the amount of pollutants used in their manufacture, long durability materials considered in the design, maximizing energy efficiency of the lighting system components, mimicking the spectrum of natural light and providing some control of lighting modes by the user. Taking into account all these considerations, it is proposed the design and construction of an intelligent lighting system that regulates the use of natural and artificial light, prioritizing the availability of the former over the latter in order to be implemented in housing in the region of the Yucatán peninsula. To achieve this goal, it is designed and built a light sensor with its own signal conditioning circuit, a light tube of stainless steel with luminous flux control, a dimming circuit for a lamp that uses light-emitting diodes (LEDs) and a control system with a PIC18f4550 micro controller.

Topics: Construction , Design
Commentary by Dr. Valentin Fuster
2011;():167-173. doi:10.1115/ES2011-54456.

Available solar heaters, particularly for baking, have not enjoyed wider success because of their inability to address issues of ease-of-integration to existing infrastructure, unit size, frequent tracking adjustment, tracking system failure, use of ‘exotic’ materials, glare, and reflector fouling from the exposure of the optical system to the close proximity of the cooking vessel. The author created a series of ‘user-friendly’ features and criteria for a proposed unit to meet these challenges.

Commentary by Dr. Valentin Fuster
2011;():175-180. doi:10.1115/ES2011-54482.

A methodology is presented that uses readily available information such as energy consumption data, limited building characteristics, and local daily temperature data to identify energy-inefficient homes in a heating-dominated climate. Specifically, this methodology is applied to 327 owner-occupied, single-family homes in Boulder, Colorado, which are compared to simulated prototype homes. A home’s energy-efficiency is characterized by its construction properties, such as insulation R-values, infiltration rates, and mechanical equipment efficiencies. Previous research indicates a close relationship between these properties and inverse modeling parameters, such as the heating slope (HS) values from variable-base degree-day (VBDD) models. The methodology compares the HS values from VBDD models of monthly natural gas consumption data to simulated HS values of reference homes. The difference, ΔHS, is the primary criterion for quantifying a home’s energy-efficiency and energy retrofit potential. To validate the results of the methodology, the results from a detailed energy assessment of a field-test home are used. Using the natural gas consumption noted in the utility data and historical weather data for the dates of bill, a VBDD model is created and the HSfield-test is calculated. HSreference of a 2009-IECC reference home of identical size is calculated and the difference, ΔHS, is calculated. Using UA-values and mechanical efficiencies from the energy assessment report, the theoretical HS values are calculated for both the assessed home and the reference home. The difference, ΔHStheoretical , is calculated. Overall, a 24% difference is found between the ΔHS and ΔHStheoretical . While the accuracy can be improved, the implication is that the energy-efficiency of homes can be inferred from inverse modeling of utility data under a specific set of conditions.

Commentary by Dr. Valentin Fuster
2011;():181-186. doi:10.1115/ES2011-54513.

The present article examines the technical, economic and environmental feasibility of installing a cooling-only ground source heat pump in a tropical country. The study is based on an existing university building at Universidad Centroamericana in El Salvador. The building was modeled using an energy simulation program in order to characterize its energy performance and compare the energy efficiency of the proposed ground source heat pump system to a conventional direct expansion system. In addition to standard energy modeling, a finite-element model was also developed in order to determine ground temperature distribution and heat island effects due to the ground source heat pump system. Modeling results predicted that the proposed system would reduce energy consumption by 23% annually, compared to a conventional system. Additional cost savings, associated with a reduction in maintenance and replacement costs, reduce operational costs by 37% over the life of the project. The proposed design was also optimized using energy modeling and a first cost estimate was obtained. An economic analysis predicted that the simple payback period of the system would be on the order of six years. The paper analyzes the technical, economic and environmental advantages of the concept and the potential barriers for implementation.

Topics: Cooling , Heat pumps
Commentary by Dr. Valentin Fuster
2011;():187-195. doi:10.1115/ES2011-54524.

This paper presents a heat transfer model for thermally active drilled-shaft foundations used for heating and cooling buildings. Specifically, this paper presents a numerical approach to evaluate the unsteady temperature distribution within the ground medium surrounding the foundation as well as indoor/outdoor heat fluxes. In particular, a 2-D numerical solution was obtained using the finite difference technique with a purely implicit solution scheme. The results of the sensitivity analysis indicate that the efficiency of the thermo-active foundation can be significantly improved with a proper selection of design parameters including flow velocity, foundation depth, and foundation materials.

Commentary by Dr. Valentin Fuster
2011;():197-203. doi:10.1115/ES2011-54525.

Developing nations face increasing economic and environmental challenges and the search for housing design solutions that approach sustainability by meeting thermal comfort, energy efficiency, environmental and low initial cost criteria is underway. This paper presents the results of a multidisciplinary research project that aimed at designing a low-income house and a middle-income house that perform well from the architectural, thermal comfort, and energy efficiency standpoint while being cost-competitive. Multiple passive cooling strategies were considered and evaluated by energy modeling tools. The thermal and energy performance of the proposed designs were analyzed throughout the design process and the various design iterations. A full budget was prepared for the proposed low-income housing design and first-costs were found to be competitive with conventional housing. The paper discusses the proposed design features, their impact on thermal comfort and energy efficiency and the feasibility of integrating alternative energy systems to the proposed designs.

Commentary by Dr. Valentin Fuster
2011;():205-211. doi:10.1115/ES2011-54543.

Solar heating systems are widely used in several European countries for domestic hot water heating, and in the past decade, an increasing number of solar combined space and hot water heating systems (typically referred to as “combisystems”) have begun to take precedence. In Canada, however, the majority of all residential solar thermal installations are for heating domestic hot water. To date, various combisystem configurations have been investigated under the auspices of the International Energy Agency, Task 26 and Task 32. Within these tasks, various system configurations were modelled and test procedures developed to allow standard performance evaluations to be conducted. This work, although extensive, has limited application within the North American context. At present, little research has been conducted on the applicability of these systems for residential housing. In particular, due to Canada’s more severe winters, larger solar collector arrays would be required to significantly contribute to the space heating load. This has drawbacks, as much of the solar capacity would not be utilized during the summer, leading to poor economic performance and possible overheating that could accelerate degradation or scald occupants. Therefore, there is a need to optimize the configuration of solar combisystems to avoid over-sizing while maximizing the utilization of solar energy in a safe and economic manner. This paper presents a review of the current literature on solar combined space and domestic hot water heating systems, with a particular emphasis on the work which has been conducted by the International Energy Agency. In addition, a review of combined space and domestic hot water systems currently installed in Canada are also discussed.

Commentary by Dr. Valentin Fuster
2011;():213-224. doi:10.1115/ES2011-54549.

Flex House is a flexible, modular, pre-fabricated zero energy building that can be mass produced and adapted easily to a variety of site conditions and plan configurations. The key factor shaping the design is central Florida’s hot humid climate and intense solar radiation. Flex house combines the wisdom of vernacular Florida houses with state of the art Zero Energy House technologies (ZEH.) A combined system of photovoltaic panels and solar thermal concentrating panels take advantage of the region’s abundant insolation in providing clean renewable energy for the house. Conservation is achieved with state of the art mechanical systems and innovative liquid desiccant dehumidification technology along with highly efficient lighting and appliances. The hybrid nature of the Flex house allows for both an open and closed system to take advantage of the seasonal temperature variation. Central Florida buildings can conserve energy by allowing natural ventilation to take advantage of passive cooling in the mild months of the year and use a closed system to utilize mechanical cooling when temperatures are too high for passive cooling strategies. The building envelope works equally well throughout the year combining an optimum level of insulation, resistance to air infiltration, transparency for daylight, and flexibility that allows for opening and closing of the house. Flex House is designed with a strong connection between interior spaces and the outdoors with carefully placed fenestration and a movable wall system which enables the house to transform in response to the temperature variations throughout the year. The house also addresses the massive heat gain that occurs through the roof, which can generate temperatures in excess of 140 degrees. Flex House incorporates a parasol-like outer structure that shades the roof, walls and courtyard minimizing heat gain through the building envelope. To be implemented on a large scale, ZEH must be affordable for people earning a moderate income. Site built construction is time consuming and wasteful and results in higher costs. Building homes in a controlled environment can reduce material waste, and construction costs while increasing efficiency. Pre-fabricating Flex House minimizes preparation time, waste and safety concerns and maximizes economy, quality control, efficiency and safety during the construction process. This paper is an account of the design and construction of Flex House, a ZEH for central Florida’s hot humid climate.

Commentary by Dr. Valentin Fuster
2011;():225-234. doi:10.1115/ES2011-54552.

The development of social housing In Mexico during the last decade has been supported by the different levels of government (federal, state, and municipal) in order to assist low-income families. The accelerated construction that takes place in order to address the housing deficit causes a reduction in the quality of design and construction, which is also affected by rising building costs. Environmental comfort conditions inside the dwellings are reduced drastically when houses are constructed without considering climate conditions, especially in hot arid regions. This situation generates uncomfortable thermal conditions for users and high-energy costs due to the unavoidable need of air conditioning. User profiles, architectural program, comfort preferences and guidelines for design and construction of future dwellings in the city of Hermosillo, in northwest Mexico, were determined by surveying beneficiaries of government affordable housing programs. One survey measured the degree of satisfaction of inhabitants in a sample of over 370 households; a second survey sampled 200 households and was aimed at determining aspects of comfort. This paper describes the results of thermal simulations carried out on two housing models. The first model represents the type usually constructed by commercial developers, and the second is a proposal developed by the research team according to guidelines based on the results of the research project described before. This study is a preliminary step in the construction of a physical model for experimental research and demonstration.

Commentary by Dr. Valentin Fuster
2011;():235-242. doi:10.1115/ES2011-54610.

According to the National Energy Balance (1), the electricity consumption in the residential and commercial sector represents thirty-three percent of the total consumed in the country. Most of the energy is consumed during the summer, when it is necessary to use air conditioning to maintain comfort conditions inside buildings. This aspect takes relevance in warm-dry climates, where a deficient design of building envelope and a wrong location of windows can increase the thermal loads producing an extra load to air conditioning systems and high costs by electricity energy consumption. For this reason, adequate design strategies and thermodynamic concepts have to be applied in order to make dwellings comfortable. Two dwellings are simulated and analyzed, the first one is made of regional materials like traditional concrete block walls, reinforced concrete roofs and economic finishes, the second one is proposed with a green roof and insulation in walls. The heat gains through the different constructive elements have been obtained, to analyze their impact on global thermal comfort and the electricity energy consumption of air cooling systems. Also, an exergy analysis has been applied to analyze exergy efficiency of air cooling systems and the influence that the building envelope can have in them with the proposed changes. The minimum exergy expenditure of air conditioning systems required to achieve comfort conditions inside dwellings could be a useful benchmark for the comparison of various dwelling designs.

Commentary by Dr. Valentin Fuster
2011;():243-248. doi:10.1115/ES2011-54707.

Solar collector is a type of heat exchanger which transfers solar radiation energy into the heat energy. Conventional solar air collectors have poor thermal efficiency primarily due to high heat losses and low convective heat transfer coefficient between the absorber plate and flowing air stream, leading to higher absorber plate temperature and greater thermal losses. Attempts have been made to improve the thermal performance of conventional solar air collectors by employing various design and flow arrangements. Double pass counter flow solar air collector with porous material in the second air passage is one of the important and effective design improvement that has been proposed to improve the thermal performance. This paper presents the performance and economic analysis of double pass solar air collector with and without porous material. Effects of various parameters on the thermal performance and pressure drop characteristics have been studied experimentally. The study concludes that double pass arrangement with porous material is economical and having short payback period. Also, the thermal performance of double pass solar air collector with porous material is significantly higher compared to double pass solar air collector without porous material and single pass arrangement.

Commentary by Dr. Valentin Fuster
2011;():249-257. doi:10.1115/ES2011-54708.

For the past few decades sea surface temperatures across the globe have been increasing, causing changes in the global and regional climates. The focus of this study is to determine the impacts of these climate changes in coastal California region and possible linkages to energy infrastructure. The specific goal of this study is to determine the changes in cooling degree days (CDD) for the Northern Pacific Coast of the U.S., with emphasis on the California region for the years 1970 to 2007. Daily, monthly and annual temperature trends in months May, June, July, August and September are used to complement this analysis. Temperature data from more than 300 surface weather stations were obtained from the National Climatic Data Center (NCDC). The work follows recent findings by the authors where the decreasing of maximum summer temperatures in two coastal air basins of California was attributed to the increase in sea breeze flow. This was caused by regional climate changes which led to induced sealand asymmetric warming and referred to as a reverse-reaction of global warming. This study aims to analyze temperature trends along the entire North Pacific Coast and over time, showing how it relates in the same temporal and spatial scales to changes in CDD. Finally, the study explores the possible correlations of decadal trends of CDD with actual summer peak electric utility data demonstrating how regional climate changes are affecting regional energy demands.

Commentary by Dr. Valentin Fuster
2011;():259-271. doi:10.1115/ES2011-54738.

Heating Degree Days (HDDs), calculated from hourly weather data, are often used to estimate energy savings for a variety of energy efficiency measures (EEMs) to be applied to conditioned spaces in buildings. More specifically, application of HDDs is useful for estimating savings from weather-dependent EEMs. For first order estimation, it is often problematic to calculate HDDs for a given base temperature, when temperature setbacks are used in the conditioned spaces. This paper provides a set of correlations to characterize HDDs for selected ASHRAE Climate Zones as functions of three key parameters including the base temperature, setback temperature level (delta-T), and setback duration. In addition to the well-documented pattern of decreasing HDDs for decreasing base temperature, it was also shown that HDDs are inversely proportional to both setback duration and temperature setback differential levels. In the analysis presented in this paper, corrections to estimate HDDs when temperature setbacks are used for typical residential space heating schedules during unoccupied periods which occurred from 8 am to 5 pm Monday through Friday. In particular, regression correlations using two- and three-parameter models have been developed to estimate HDDs for multiple US locations that account for the impact of temperature setbacks on the heating requirements of residential buildings. For the two-parameter model, the input variables for the regression correlations are setback hours and delta T; for the three-parameter model, the input variables for the correlations include setback hours, delta T, and base temperature. The prediction accuracy for the energy savings, due to a set of EEMs, obtained from the HDD method —using the developed correlations— is tested against whole-building detailed energy simulation analysis for two single family homes. Detailed energy audits including utility data analysis have been carried out for both homes to calibrate the detailed simulation model and evaluate the effectiveness of the EEMs in reducing building energy use. The results from the detailed simulation analysis are then compared to those obtained from the HDD with temperature setbacks.

Commentary by Dr. Valentin Fuster
2011;():273-283. doi:10.1115/ES2011-54739.

Recently, the city of Boulder, CO has recently approved mandatory energy efficiency standard, called SmartRegs Program, for rental properties. Improving residential energy efficiency is a goal of the city as they strive to meet the green house gas reduction targets of the Kyoto Protocol. However, energy efficiency is typically not implemented in rental units because of a split incentive between landlords and tenants. This paper evaluates the various retrofit measures that improve rental homes energy efficiency as well as the effectiveness of SmartRegs Program. First, various energy efficiency measures are evaluated through walk-through and detailed energy audits to assess their effectiveness in improving the energy performance of rental homes. Based on the results of the energy audits and survey of various stake holders, a set of recommendations have been defined to ensure that the SmartRegs program be successfully implemented in order to improve the overall performance and quality of rental homes. Moreover, it is found that energy efficient can increase the thermal comfort levels and decrease the energy costs for tenants, increase the value of the property for landlords, and help the city meet their green house gas reduction goals.

Commentary by Dr. Valentin Fuster
2011;():285-290. doi:10.1115/ES2011-54769.

Cooling in residential buildings becomes more important due to the rising insulation requirements and the increasing human comfort. Therefore, systems that provide heating as well as cooling with a low primary energy consumption will be in future more preferred than conventional single-unit systems. Solar thermal installations can here provide in addition to the domestic hot water and heating demand a significant contribution to the cooling requirement in residential buildings. In this study, low-energy residential buildings with different solar heating and cooling systems are analyzed concerning their primary energy consumption. To cover a large range of different weather conditions, two locations (Madrid and Würzburg) with different solar energy supply are considered. Further, a conventional solar heating supply system including one or more typical room air-conditioners is as reference system selected. The different systems are modeled by the system simulation platform TRNSYS. In a first step, the question is addressed of whether a solar thermal system with standard dimensioning, taking the domestic hot water and heating demand into account, is sufficient to meet the cooling requirements. To cover the cooling demands, a small-scale thermally driven absorption chiller has been selected. In a next step, the studied systems are compared in terms of primary energy saving as a function of the solar cooling fraction. The simulation results have shown that regions with a high solar energy supply do not take advantage of solar thermal cooling, due to the higher cooling demand. On average, 70% of the cooling demands can be covered by a standard dimensioned solar thermal system. At the same time, a primary energy saving up to 90%, compared to currently installed room air-conditioning units can be achieved.

Commentary by Dr. Valentin Fuster
2011;():291-296. doi:10.1115/ES2011-54805.

In this paper, we will present a numerical model for estimating the thermal performance of unglazed transpired solar collectors located on the Breck School campus in Minneapolis, Minnesota. The solar collectors are installed adjacent to the southeast facing wall of a field house. The collectors preheat the intake air before entering the primary heating unit. The solar collector consists of 8 separate panels (absorber plates). Four fans are connected to the plenum that is created by the absorber plates and the adjoining field house wall. All fresh air for the field house is provided by the solar collectors before being filtered and heated by four, independent two stage natural gas fired heaters. Moreover, the following data were collected onsite using a data acquisition system: indoor field house space temperature, ambient air temperature, wind speed, wind direction, the plenum exit air temperature, the absorber plate temperature, and the air temperatures inside the plenum. The energy balance equations for the collector, the adjacent building wall, and the plenum are formulated. The numerical model is used to predict the air temperature rise inside the plenum, recaptured heat loss from the adjoining building wall, energy savings, and the efficiency of the collectors. The results of the numerical model are then compared to the results obtained from the onsite measurements; which are in good agreement. The model presented in this paper is simple yet accurate enough for architects and engineers to use it with ease to predict the thermal performance of a collector.

Commentary by Dr. Valentin Fuster
2011;():297-302. doi:10.1115/ES2011-54837.

An experimental rig was set up to test the thermal performance of a solar air heating system based on an unglazed transpired collector of 2.5 m2 . The experiment was carried out at Harbin Institute of Technology in the city of Harbin, which is located in northeastern China, at latitude 45°41′ N and longitude 126°37′ E. The tests were spread over a number of days, in which the 4-day experimental data within the period were selected as the sample for analysis. Experimental results show that solar collector’s surface temperature and exit air temperature increase with increasing solar irradiation. The influence of ambient temperature on surface temperature and exit temperature is negligible. Temperature rise decreases with increasing air flow rate, while collector efficiency increases with increasing air flow rate. For an air flow rate of 100 m3 /h in Test 1, the average air temperature rise and collector efficiency were 28.86°C and 72% respectively; for an air flow rate of 235 m3 /h in Test 2, the average air temperature rise and collector efficiency were 11.52°C and 78% respectively. Higher airflow rate tends to operate the collector at lower surface temperature, which results in lower overall heat losses from the collector to the surroundings, therefore increasing airflow rate reduces air temperature rise and enhances the collector efficiency. The average efficiency of the experimental solar air heating system in the 4-day experiment period was 72%, 78%, 61%, and 72% respectively, which are higher than most conventional glazed flat-plate solar air collectors. With better coordination with architectural design at early stage in a project, this building-integrated solar air heating system can be both aesthetically and technically viable.

Topics: Solar energy , Heating
Commentary by Dr. Valentin Fuster
2011;():303-309. doi:10.1115/ES2011-54854.

In this paper, the genetic algorithm is applied to calculate the optimum slope and surface azimuth angles for receiving maximum solar radiation in an area of Iran. Different components of solar radiation are employed in order to calculate the solar optimum angles. At first, the optimum angels are calculated in different days, months, seasons and the whole year and the energy gain is calculated. Then, this process is redone with considering different component of solar radiation. These conditions are direct, direct and ground reflect, direct and diffuse, and all together. The results showed that maximum solar energy in different days of a year is received at different slope angels; however, the optimum azimuth angle is zero for receiving maximum solar energy. In addition, adjusting the collector at the daily optimum slope angle can only save energy very little compared with the case at the monthly optimum slope angle. Furthermore, the results of analyzing different components of solar radiation show that the optimum slope angles are mostly related to the direct radiation, however, the gain of energy is considerably different. It is worth mentioning that genetic algorithm is more effective when the independent parameters are numerous and in this case, the optimum angles are easily determined, however, the computation time is reduced.

Commentary by Dr. Valentin Fuster
2011;():311-316. doi:10.1115/ES2011-54862.

During the past few decades, a wide range of studies have been performed to improve the performance of flat plate solar collectors by either reducing the heat loss from a collector or by increasing the amount of solar radiation absorbed by the absorber plate. Examples of these studies include adding transparent honeycomb to fill the air gap between the glazing and absorber plate to reduce convective heat loss, replacing the air in the gap by other gases such as Argon, Krypton, Xenon and Carbon Dioxide, or adding a chemical coating such as Copper Oxide to increase absorbtance and reduce the emittance of the absorber plate. While these methods improve the collector’s efficiency, they focus primarily on limiting the natural convection that occurs in the collector cavity, or on improving the optical properties of the absorber or