ASME Conference Presenter Attendance Policy and Archival Proceedings

2018;():V06AT00A001. doi:10.1115/IMECE2018-NS6A.

This online compilation of papers from the ASME 2018 International Mechanical Engineering Congress and Exposition (IMECE2018) 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presenter attendance policy, if a paper is not presented at the Conference by an author of the paper, the paper will not be published in the official archival Proceedings, which are registered with the Library of Congress and are submitted for abstracting and indexing. The paper also will not be published in The ASME Digital Collection and may not be cited as a published paper.

Commentary by Dr. Valentin Fuster

Energy: CMS: Biofuel Production, Gasification, and Combustion

2018;():V06AT08A001. doi:10.1115/IMECE2018-87974.

Torrefaction is a thermal pretreatment process which usually takes place at temperatures between 200–300°C. Torrefied biomass has been proven in numerous studies to have superior combustion properties compared to raw biomass. The objective of this study is to develop a model to estimate solid energy yield, elemental compositions and enthalpy of solid and volatile yield. Formation enthalpy of raw and torrefied biomass is calculated using the correlations developed for elemental compositions and HHV of torrefied biomass. Solid yield is determined by anhydrous weight loss model for torrefied wood. Specific heat correlations for raw biomass and char are used to calculate the sensible heat required for torrefaction process. Sensible heat and formation enthalpy give the total enthalpy for raw and torrefied biomass. During torrefaction, a mixture of volatile compositions is released. Experimental mass fractions of the volatiles components are taken from published literature, which allowed us to determine the enthalpy of formation and specific heat of the volatiles. Finally, the model results associated with the torrefaction process are compared with experimental data.

Topics: Biomass , Modeling
Commentary by Dr. Valentin Fuster
2018;():V06AT08A002. doi:10.1115/IMECE2018-88010.

Biomass gasification is the devolatilization and incomplete combustion of biomass resulting in the production of a combustible gas mixture including carbon monoxide (CO), hydrogen (H2) methane (CH4), and traces of other hydrocarbons (CnHm), and referred to as producer gas. Producer gas can be cleaned and then used in various engines or can be converted to various biofuels. This paper presents an experimental and simulation-based evaluation of producer gas quality resulting from corn kernel gasification in a two-stage downdraft gasifier. Test conditions were selected, based on the results of previous studies, to yield high conversion efficiency and low tar production. Experimental tests were performed with an air flow of 25 Nm3/h and with 80% of the air supplied to the first gasification stage. Simulations based on a chemical and thermal equilibrium model were carried out to examine the effect of equivalence ratio (ER) changes. Both the experimental and modelling results show that using a two-stage air supply leads to a significant reduction in the tar content of the producer gas, while maintaining a high gasification efficiency.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A003. doi:10.1115/IMECE2018-88386.

Activated carbon is one of the most effective materials for removing a wide range of contaminants from water, e.g., industrial and municipal wastewater. In this paper, physical (steam) activation of peach pit biochar obtained from a biomass gasification power plant is explored. Activation experiments were carried out at various temperatures, steam flow rates, and activation times. The initial biochar and activated biochar samples have been analyzed for porosity, chemical composition and surface morphology. From the porosity analyses it was determined that the raw biochar had a surface area in the order of 1 m2/g, whereas the activated samples had surface areas ranging from 379 m2/g to nearly 600 m2/g. The burn off ranged from 29 % to 56 %. Energy wise, the biochar sample processed for the shortest time with the lowest flow rate had the largest ratio of surface area-to-consumed energy.

Commentary by Dr. Valentin Fuster

Energy: CMS: Biofuels Production, Conversion, and Simulation

2018;():V06AT08A004. doi:10.1115/IMECE2018-86301.

Biofuels have received considerable attention as a more sustainable solution for heating applications. Used vegetable oil, normally considered a waste product, has been suggested as a possible candidate. Herein we perform a life cycle assessment to determine the environmental impact of using waste vegetable oil as a fuel. We present a cradle to fuel model that includes the following unit processes: soybean farming, soy oil refining, the cooking process, cleaning/drying waste oil, preheating the oil in a centralized heating facility and transportation when required. For soybean farming, national historical data for yields, energy required for machinery, fertilizers (nitrogen, phosphorous and potassium), herbicides, pesticides and nitrous oxide production are considered. In soy oil refining, steam production using natural gas and electricity for machinery are considered inputs. Preprocessing, extraction using hexane and post processing are considered. In order to determine a mass balance for the cooking operation, oil carryout and waste oil removal are estimated. During waste oil processing, oil is filtered and water removed. Data from GREET is used to compute global warming potential (GWP) and energy consumption in terms of cumulative energy demand (CED). Mass allocation is applied to the soy meal produced in refining and oil utilized for cooking. Results are discussed with emphasis on improving sustainability. A comparison is made to traditional fuels, e.g., commercial fuel oil and natural gas. The production of WVO as fuel has significantly less global warming potential but higher cumulative energy consumption than traditional fuels. The study should provide useful information on the sustainability of using waste cooking oil as a fuel for heating.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A005. doi:10.1115/IMECE2018-86490.

The change in laminar burning speed and ignition delay time of iso-octane with the addition of oxygenated fuels are investigated. As oxygenated fuels, ethanol and 2,5 dimethyle furan (DMF) are used. To confirm the process and mechanism a detailed validation is done on laminar burning speed and ignition delay time. Further, three different blending ratios of 5%, 25% and 50% for both ethanol/iso-octane and DMF/iso-octane are investigated separately. Wide range of equivalence ratio from 0.6–1.4 is considered in calculating laminar burning speed. Ignition delay time is measured under various temperatures from 650 K to 1100 K. Results of each blending are compared with the pure fuels. A comparison is also done between the effects of these two oxygenates. It has found that for each blending case presence of DMF brings larger change in the behavior of iso-octane than ethanol. This observation refers to further study on comparison of these two oxygenates.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A006. doi:10.1115/IMECE2018-86552.

This work was focused on the development of a hybrid engine which was fueled with three different fuels; gasoline as original fuel, Liquid Petroleum Gas (LPG) and biogas as two alternative fuels. The developed engine consisted of fuel storage tanks, a small gas reducer, a fuel premixer and the engine of a Suzuki Skydrive 125CC motorcycle. Performances of the prototype and developed engines were compared in terms of wheel speed. The developed engine could be started, idled and accelerated with the average maximum speed of 1276 revolutions per minute when it was connected directly with the biogas reservoir. Then, the biogas was compressed and stored in a standard gas tank which was connected with the developed engine, the average maximum speed of 1273.67 revolutions per minute was obtained from three experiments. This work emphasized not only biogas usage as the alternative fuel for the engine but also pointed out that biogas quality could affect the engine performance. The developed engine could be applied as vehicle engine or it could drive household self-power generators by using household biogas as fuel.

Commentary by Dr. Valentin Fuster

Energy: Design and Analysis of Energy Conversion Systems

2018;():V06AT08A007. doi:10.1115/IMECE2018-86114.

This paper puts forward a new kind of SOFC - GT distributed energy system with methanol as fuel, through the absorption refrigeration (AR) and heat exchanger (HE) to recover the waste heat of GT. Based on thermodynamic analysis model, the performances, especially the exergy losses of the unit as well as its subsystems mainly including eight parts were obtained. The chemical energy of the fuel will directly be changed into electricity. Energy conversion efficiency can be as high as 85% above. The theoretical value has been paid attention by the researchers from all over the world. Comparative study in this paper, the simulation calculation and thermal performance analysis of the performance of two kinds of SOFC - GT is conducted. The results show that the total power generation efficiency of pure SOFC system, Case A and Case B are 19.28%, 55.79% and 52.26% respectively. The total thermal efficiency of Case A and B are 83.44 % and 82.79 % respectively. Additionally, the changing laws of total exergy loss, energy and exergy efficiency of integrated system at different loads also were studied. The results provide not only theory basis and scientific support for the design of the SOFC - GT distributed energy system with absorption refrigeration and heat exchanger recovering waste heat, but also a new scheme of energy saving and optimization for the units.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A008. doi:10.1115/IMECE2018-86115.

Distributed energy technology is an important developing direction of the future energy technology. This paper puts forward a distributed energy system named SOFC-GT-RC with LNG as fuel and recovering carbon dioxide. In the system, the cold energy of LNG can not only cool the compressor inlet air to reduce consumption of compressor work, but also to supply cold energy and to get zero-CO2 and other emissions. Based on mathematical model of each part, the thermodynamic calculation model of the whole system is built by FORTRAN, which is embedded in ASPEN PLUS. The results of calculation indicate the thermal efficiency and total power efficiency are 74.5% and 56.7% while the exergy efficiency is 61.8%. In addition, some operating parameters such as fuel utilization factor and fuel flow rate are selected. Based on these operating parameters, the new system thermodynamic performance is studied. The results point that this SOFC-GT-RC system fueled by LNG increases the total power, decreases waste of cold energy and the pollution of the environment, which would be an effective utilization style of energy in China’s LNG satellite stations.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A009. doi:10.1115/IMECE2018-86250.

This paper firstly educes an energy-based ecological function (EF) which is a compromise between energy pumping rate (EPR) and dissipation of EPR for an endoreversible chemical pump (CP) cycle. By solving the equations of Euler Lagrange, the fundamental optimization relationships of the EF and coefficient of performance (COP) for the CP cycles with linear mass transfer (MT) law and diffusive MT law are derived. The numerical calculations to analyze the influences of the cycle parameters on the relationship between the EF and COP are provided, and the influence of two different MT laws on the EF and COP characteristic is discussed in detail. The maximum EF of the cycle with the linear MT law is bigger than that with the diffusive MT law. The results obtained in this paper can be applied to design a class of devices, such as photochemical, electrochemical and solid-state apparatus as well as mass exchangers, etc.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A010. doi:10.1115/IMECE2018-86378.

To study the fluid flow and heat transfer in a Stirling Engine Heater Head (HH), two benchtop test rigs were designed and manufactured. One is to evaluate flow loss in oscillating flow conditions and another is to evaluate heat transfer in unidirectional flow conditions. The main test section-heater head, is additively manufactured; the test section also consists of an additively manufactured regenerator and a heat rejecter. For fluid flow test rig, a linear actuator from Parker generates and maintains the oscillating flow by driving a piston in sinusoidal motion. The piston is sealed against the charged fluid using Trelleborg seals. At room temperature, by varying the charge pressure, frequency, and stroke length, multiple test conditions can be achieved. For heat transfer test rig, a Gast’s high-flow, low-pressure compressed air blower is used to deliver the flow. The data acquisition (DAQ) is comprised of National Instruments’ cDAQ and modules to measure the piston’s motion in real time, pressure with Kistler’s pressure transducers, and the temperatures with OMEGA’s thermocouples, located at both the inlet and outlet of the heater head. Presented also are the testing procedures, some expected results, and the Sage outputs that will be used to check against the measured data from the test rigs, including some preliminary results. Based on the preliminary results, pressure and position curves were sinusoidal, which is expected of oscillating motions, meaning the test rig is operating well.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A011. doi:10.1115/IMECE2018-86853.

This paper describes design and principles of operation of a novel rotary type Stirling cycle machines based on rotary positive displacement mechanisms such as twin-screw, gate rotor screw, scroll, and conical screw compressors and expanders. When these mechanisms are used as separate expanding or compressing machines, the flow of the gas is one-directional with volumes of chambers varying in accordance with a saw-tooth type function. The proposed design solution combines at least two units of gas-coupled compressor and expander arrangements with a required shift in the shaft angle. Every unit has a series of gas channels for timing the connection of its compressor and expander parts. Units are connected to each other via a set of heat exchangers, which are conventional for Stirling cycle machines: recuperative cooling and warm heat exchangers with a regenerator, built between them. The operational capability is demonstrated using three-dimensional CFD simulations. Computational results demonstrate reciprocating flow of the gas between units, as in conventional Stirling machines, and functioning of the proposed design as a multi-cylinder, double acting Stirling machine. The suggested design makes it possible to achieve full dynamic balancing, especially in the case of twin-screw and gate rotor mechanisms, due to the rotation of screws around their axes. It also eliminates a number of problems, which are specific to Stirling machines with reciprocating pistons and their kinematic drive mechanisms.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A012. doi:10.1115/IMECE2018-86878.

Magnetic gearing is a developing technology that utilizes magnetic forces to transmit torque through a system. Unlike traditional gears that rely on teeth engagement to transmit motion and torque, interacting magnetic fields in a magnetic gear transfer the torque with no contact area required. Early magnetic gearbox designs stemmed from an electromagnetic design, however, at larger scales the assembly process as well as electromagnetic design drives the overall mechanical design, due to high magnetic forces and stresses during the assembly. The development of magnetic gearboxes involves the optimization of the assembly process, the electromagnetic design and the mechanical performance to achieve a design that is robust, efficient, manufacturable, and economical. Each of these attributes is necessary to advance the technical readiness for applications as varied as wind turbines or robotics. These qualities were sought in the design of two new magnetic gearboxes which have been manufactured and tested. The mechanical design of the multistage gearbox established a repeatable assembly process that could be upscaled without compromising the structural integrity of the components. Design variants were simulated and tested to limit bending and shear stresses in the gearbox, whilst maintaining the electromagnetic performance of the system. The mechanical design of the modular magnetic gearbox established a new rotor design where manufacturability and configurability were improved to make the gearbox ideal for applications that require varying gear ratios.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A013. doi:10.1115/IMECE2018-86881.

Carbon dioxide emissions reduction in the atmosphere is the major driver of technological innovations, in particular in energy and industrial sectors. Those sectors are dominated by the use of fossil fuels whose main concern on the combustion gases is the presence of CO2. Their emission in atmosphere accumulates Carbon, the main cause of global warming. The only way to continue to make reference to fossil fuel in the medium-long term and to avoid the carbon accumulation in the atmosphere is to use technologies capable to capture and sequester the carbon in the flue gases (CCS). In the sector of electricity production, several technologies have been proposed for the capture CO2, including absorption, adsorption, cryogenic distillation or membrane separation. All of them offer flexibility and easiness of application, but they need external energy to operate. On the other hand, particular interest is reversed to those technological options that are able to remove CO2 without energy consumption; even more attention is reserved to those technologies which, suitably integrated with other conversion systems, can produce electrical energy at the same time, so increasing the electricity production with respect to the original plant. They are defined active systems and one of these is represented by Molten Carbonate Fuel Cells (MCFCs). In fact, MCFCs are fuel cell capable to concentrate CO2 at anode exhaust, making easier its capture, separation and storage and in parallel to contribute to the electricity production.

In this paper, a comprehensive model of the MCFC is used to assess the opportunity related to its use as a CO2 remover from a flue gas as a CCS active device, without energy penalties related to traditional carbon capture methods (MEA, pre and post-combustion, oxy-combustion, etc.). Hence, it has been integrated in a wider system with auxiliary components: compressors to overcome pressure drops, steam generator (also using heat recovered from MCFC exhausts) for fuel dilution, fresh air integration in cathode inlet section, heat exchangers for thermal management and recovery. A CO2 compression and drying section has been considered and represented as a multi-step intercooled compression.

The so-defined system can be used as a plug-in device able to be coupled to flue gases with different compositions and thermodynamic operating parameters (temperature, pressure, flow rates). Finally, it has been applied to a case study (a Natural Gas Combined Cycle power plant - NGCC) and the performance of the MCFC in terms of CO2 removal capacity, electrical power generation and size have been evaluated as well the energetic and environmental impact on the reference NGCC power plant.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A014. doi:10.1115/IMECE2018-86999.

The shell condenser is a key component for the underwater vehicles. To study its heat transfer performance and flow characteristics and to design a more efficient structure, a mathematical model is generated to simulate condensation inside the straight and helical channels. The model combines empirical correlations and MATLAB based on an iterative algorithm. Here, quality is used as a sign of the degree of condensation. The computational model is verified by comparison of simulations and experiments. Several cases are designed to reveal the effects of the initial condition. The inlet temperature varies from 160 to 220°C and the inlet mass velocity ranges between 133 and 200 kg/m2·s. The results show that the inlet temperature and mass velocity significantly affect flow and heat transfer in the condensation process. In addition, comparisons of the straight channel and helical channel with different Dh/R indicate that the heat transfer capability of the helical channel is obviously better than that of the straight channel, and the heat transfer coefficient and total pressure drop increase with the decrease of Dh/R. This study may provide useful information for performance prediction and structure design of shell condensers, and provide a relatively universal computational model for condensation in channels.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A015. doi:10.1115/IMECE2018-87272.

The supercritical carbon dioxide (sCO2) power generation system holds tremendous potential in nuclear, chemical and renewable energy utilization fields due to its compactness, security and high efficiency. However, the dramatic variation in the physical property of sCO2 complicates the system analysis and optimization. Recent researches usually took simple stack of all governing equations of individual components as the physical model of system. Besides, based on the traditional heat transfer modeling method, some researches apply the segmentation method to take fluid property variation into consideration. These methods exacerbate the multivariate nonlinearity of the system and are not suitable to analyze complex sCO2 thermal systems. Moreover, taking the consideration of the strong nonlinearity of sCO2 system, most researches adopt single parameter analysis to obtain the optimum solution, which may not achieve global optimization. In this contribution, introduction of a new definition of thermal resistance of heat exchanger disassembles the original implicit nonlinear properties of heat transfer processes as the linear relation between inlet temperature difference of fluids and heat flow rate, and the explicit nonlinear expression of thermal resistance. For the nonlinearity caused by the variable properties of sCO2, segmentation is also used in heat exchanger modeling. However differently, the introduction of new defined thermal resistance enables the elimination of most intermediate variables produced by segmentation, which contributes to the connection of all segments in heat exchanger into a heat exchanger network. Furthermore, based on the system layout, the equivalent power flow diagram of the system is built to derive the corresponding governing equations revealing the overall transfer and conversion laws of heat. Combining the flow resistance balance equations of all components and the accompanying power flow processes constraints offers the inherent physical constraints among operating parameters. Benefit from the conciseness of system model, the genetic algorithm can be used for the model optimization. Taking thermal efficiency of the system as the optimization objective, the optimal matching of the operating parameters under variable working conditions is obtained.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A016. doi:10.1115/IMECE2018-87324.

Marine current energy is a clean energy source and is a solution to the problems faced by burning fossil fuels such as global warming and climate change. Once tapped, the useful shaft power can be converted into electrical energy. To make this practical, the designed energy converter should be capable of operating at low marine current velocities, it should be suitable for installation at locations that have low water depths and should have lower manufacturing, installation and maintenance costs. A ducted cross-flow turbine has all the above features and it will be suitable for Pacific Island countries (PICs) for extracting marine current energy. The ducted cross-flow turbine was designed, modelled and analyzed in commercial Computational Fluid dynamic (CFD) code ANSYS-CFX. The inlet and outlet duct sizes were optimized for maximum output. Before the analysis of full model, the CFD results were validated with experimental results. Simulations for the 1:10 ducted cross-flow turbine (having a diameter of 150 mm) were performed with 400,000 nodes, as increase in the grid size did not make much difference other than increasing the simulation time significantly. The maximum difference in the power coefficient between CFD and experimental results was 6%. Simulations were then performed for the full-scale prototype, which has a duct (nozzle) inlet of 3.5 m × 3.5 m and a turbine diameter of 1.5 m, at three freestream velocities of 0.65 m/s, 1.95 m/s and 3.25 m/s. Analysis of the prototype performance showed that the ducted cross-flow turbine can reach a maximum efficiency of 56% and can produce 21.5 kW of power at a current speed of 1.95 m/s and 103.6 kW at 3.25 m/s. The designed cut-off speed was 4 m/s.

Topics: Design , Turbines , Cross-flow
Commentary by Dr. Valentin Fuster
2018;():V06AT08A017. doi:10.1115/IMECE2018-87673.

Shamsl is hybrid solar/natural-gas concentrated solar power (CSP) plants. The plant is also integrated with a booster gas-fired-heaters for steam superheating. In addition to direct fire-heaters to the heat transfer fluid (HTF) for supplying thermal energy during the night or whenever the solar irradiance level is dimmed. However, there is a more sustainable way to avoid power-generation-outages caused by transient weather conditions without a significant plant reconstruction, i.e. integration with gas turbines. In this study, a thermodynamic model of Shamsl integration with gas turbines is developed to investigate the gas turbine capacity and the exergitic efficiency of the supplied gas with and without the gas turbine involvement. The HTF heaters will receive the needed thermal energy from the gas turbines exhaust gases instead of the direct fire-heater (case1). Another potential is replacing the booster fire heaters with the gas turbine system as well. (case2). A parametric study is conducted to determine the size and the requirements of a gas turbine system for the specified power target demand in addition to a feasibility study for the proposed system. The results showed that using two gas turbines for the HTF heater significantly improved the overall efficiency and reduces the CO2 emission. Replacing the booster heater with two gas turbines improves the efficiency up to excess air factor of 2.5.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A018. doi:10.1115/IMECE2018-87678.

The growth of demand for energy is increasing rapidly, and most current power generation is heavily dependent on fossil fuels. Using fossil fuels for power generation is not a secure future and is limited. The most abundant source of energy is solar energy. Concentrated solar power collectors have become one of the most effective choices to convert solar energy to heat, which can then be used to drive heat engines. Over the past decade, research on hybrid solar-gas turbines have shown good promise. This paper examines and studies the performance and design aspects of a hybrid micro solar-biogas turbine and its component technology for supplying low-carbon electricity on off-grid regions. Brayton cycle based several cycles are analyzed including a recuperator system. 100 kW unit system is designed.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A019. doi:10.1115/IMECE2018-87761.

Increased utilization of natural-gas (NG) in the transportation sector can decrease the use of petroleum-based fuels and reduce greenhouse-gas emissions. Heavy-duty diesel engines retrofitted to NG spark ignition (SI) can achieve higher efficiencies and low NOx, CO, and HC emissions when operated under lean-burn conditions. To investigate the SI lean-burn combustion phenomena in a bowl-in-piston combustion chamber, a conventional heavy-duty direct-injection CI engine was converted to SI operation by replacing the fuel injector with a spark plug and by fumigating NG in the intake manifold. Steady-state engine experiments and numerical simulations were performed at several operating conditions that changed spark timing, engine speed, and mixture equivalence ratio. Results suggested a two-zone NG combustion inside the diesel-like combustion chamber. More frequent and significant late burn (including double-peak heat release rate) was observed for advanced spark timing. This was due to the chamber geometry affecting the local flame speed, which resulted in a faster and thicker flame in the bowl but a slower and thinner flame in the squish volume. Good combustion stability (COVIMEP < 3 %), moderate rate of pressure rise, and lack of knocking showed promise for heavy-duty CI engines converted to NG SI operation.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A020. doi:10.1115/IMECE2018-87783.

3D CFD IC engine simulations that use a simplified combustion model based on the flamelets concept can provide acceptable results with minimum computational costs and reasonable running times. More, the simulation can neglect small combustion chamber details such as valve crevices, valve recesses and piston crevices volume. The missing volumes are usually compensated by changes in the squish volume (i.e., by increasing the clearance height of the model compared to the real engine). This paper documents some of the effects that such an approach would have on the simulated results of the combustion phenomena inside a conventional heavy-duty direct-injection CI engine, which was converted to port-fuel injection SI operation. 3D IC engine simulations with or without crevice volumes were run using the G-equation combustion model. A proper parameter choice ensured that the simulation results agreed well with the experimental pressure trace. The results show that including the crevice volume affected the mass of unburned mixture inside the squish region, which in turn influenced the flame behavior and heat release during late-combustion stages.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A021. doi:10.1115/IMECE2018-87836.

Long heavy-haul trains are now a reality, especially for ore transportation. In some railways, compositions of up to 330 wagons are in service, requiring several locomotives. Trains like that travel long distances, sometimes through cities or in uninhabited regions. They are driven by just one driver which must keep the whole train working safely on the track. The wagons don’t have any source of electrical energy to power sensors and to transmit their signals to the locomotive; nor wireless communication. In fact, in some of these railways, there is no internet along with the track out of the cities. One important indicator of the safety of the train is the force between the wagons during the trip, through the shunting. Using strain gauges to measure these forces is a possible solution and ultrasonic stress sensors (UST) is a suitable alternative. UST with Lcr waves requires a low amount of energy and can be employed in rusty and dirty places. However, they also need an energy source. Wind and solar solutions are not always adequate because, unfortunately, there are places where these components have economic value and they can be stolen. A possible source of energy to power the USTs could be the Vibration Energy Harvester (VEH). These simple and not expensive systems can be built in small packs, giving the energy to measure the forces and transmit the data to the locomotive or designated sites along the track. This work aims to evaluate the possibility of using VEH to power USTs to measure the forces between the wagons during the journey. Knowing that the oscillation in the shunting has a very low frequency, the work intent to optimize a multi-beam VEH to be able to capture the highest amount of energy possible, in a very small arrangement, using genetic algorithm. The result shows that VEH is an adequate alternative to power autonomous UST sensors.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A022. doi:10.1115/IMECE2018-87843.

Reverberatory furnaces improper burners and chimney location would cause a significant scape of hot gases and shorten their residence time in the furnace and therefore reduce the convective heat transfer opportunity to the metal and walls surfaces. Appropriate burners location and orientation, as well as the chimney location, are very expensive to adjust in practical furnaces by trial and error to maximize the furnace performance. This study aimed to develop a validated 3-D CFD furnace model for studying the effect of burners’ location and orientation, chimney location and flow momentum on the hot gases residence time, heat transfer, flow and temperature distribution as well as the overall exergetic efficiency of the furnace. The results reflect the optimum design parameters for maximizing the furnace performance.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A023. doi:10.1115/IMECE2018-88046.

The manufacture of relatively low commercial value ceramic products for construction is an energy intensive industry. It is important to improve and optimize the energy equation of the plant operation while simultaneously introducing renewable primary energy sources for the heat supply.

The present paper concerns the analysis of the energy usage in a brick plant. This unit operates continuously on a 3 shift schedule. The overall annual production of five types of bricks is over 62 kton and the main energy consumption unit is the furnace. For this unit, the thermal load is supplied mainly by biomass coupled with fuel oil (80%–20% split, respectively) which yield a maximum temperature of 950 °C. The process is controlled by adjusting the air mixing in the kiln. A secondary furnace provides the heat for a rotating dryer for biomass drying which is supplied to the main furnace.

The fuel is a mixture of various sources and its characteristics were determined by means of an elemental analysis, ash content and the measurement of the heat value. Measurements of mass fluxes along with the operating temperature on critical elements of the plant and chemical composition of the flue gases were used to calculate the energy balances to the plant. Because of the diversity of the product mix the production was normalized using the mass/surface area ratio of the various types of bricks. From the results, the energy intensity is 44 kg of oil equivalent per ton.

The exergy analysis of the plant shows that most of the energy degradation occurs in the kiln. The analysis also enabled to assess the influence of the replacing fossil fuel by biomass on the increase of exergy efficiency of the plant.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A024. doi:10.1115/IMECE2018-88079.

Deterioration of environment caused by the release of harmful greenhouse gases (mainly CO2) from the power plants has become an area of growing concern. At the present, various methods are being investigated for capturing and storing CO2. Current technologies require a huge amount of energy leading to reduction in overall efficiency. The introduction of Allam cycle, which uses high pressurized super critical CO2 as working fluid has added a new dimension to solve this problem. This is an innovative oxy-fuel power cycle which ensures a near zero emission through inherent capture of all CO2. This paper concentrates on performance modeling of an Allam cycle. The effects of various input parameters are analyzed for achieving highest efficiency. Performance of each component in the cycle is investigated separately and combined therefore to get the overall performance of the cycle. The impact of using an ASU without intercooling and then supplying the high temperature outlet gases except oxygen to the recuperator is investigated. Although, a high power is consumed within ASU, the overall energy requirement decreases as extra energy becomes available in the recuperator to preheat the recycled CO2. An efficiency of 55% is predicted for the cycle.

Topics: Modeling , Cycles
Commentary by Dr. Valentin Fuster

Energy: Electrochemical Energy Conversion and Storage

2018;():V06AT08A025. doi:10.1115/IMECE2018-86111.

Parasitic power requirement is a key criterion in selection of suitable battery thermal management system (TMS) for EV applications. This paper presents a hybrid TMS with negative parasitic requirements, designed by integrating phase change material (PCM) with thermoelectric devices. The proposed system does not require any power consumption to maintain tight control over battery cell temperature during aggressive use and repetitive cycling. In addition, it can recover a portion of waste heat produced during the typical operation of EV battery packs.

Commercially available LiFeP04 20 Ah pouch cell has been chosen as a test battery sample for validating the conceptual design presented herein. The commercial battery cells, submerged in a PCM-filled polycarbonate casing, are subjected to a cyclic discharge process to elucidate their heat generation characteristics at 27 °C. Charging and discharging is conducted at 0.5C and 1C, respectively. A thermoelectric circuit is used to recover the heat energy absorbed by the PCM and to convert it to electrical energy. The manuscript further details some of the major findings of this experiment.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A026. doi:10.1115/IMECE2018-86582.

In this study, the low-temperature energy efficiency of lithium-ion batteries (LIBs) with different chemistries and nominal capacities at various charge and discharge rates is studied through multi-physics modeling and computer simulation. The model is based on the irreversible heat generation in the battery, leading to the charge/discharge efficiency in LIBs with graphite/LiFePO4, graphite/LiMn2O4, and graphite/LiCoO2 electrode materials in which the effects of the battery nominal capacity at various charge and discharge rates are studied. Using characterized sources of the heat generation in the LIB leads to providing a battery efficiency plot at different operation condition for each LIBs. The results of this study assist the battery engineers to have much more accurate prediction over the efficiency of the LIBs at low temperatures.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A027. doi:10.1115/IMECE2018-87311.

Solid electrolyte interphase (SEI) film resistance is an important parameter in the study of charge transfer kinetics of a Li-ion battery. The passive film affects diffusion process of Li-ions. As such, it becomes essential to include film resistance in battery modelling. However, the traditional method of estimating the SEI film resistance is costly and time consuming. An indirect approach based on Ohm’s law is thus presented in this paper. It relies on determining the interfacial polarisation from the difference of open-circuit voltage measured immediately after switching off the applied current and the equilibrium voltage. The technique is simple, easy to implement and can be used for a quick estimation of SEI film resistance with reasonable accuracy. For instance, average value of SEI film resistance for commercial LFP battery cell is measured as 0.004 Ohm · m2 , which was found to be consistent with the values determined using the impedance spectroscopy techhnique in the published literature for lithium-carbon film electrodes.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A028. doi:10.1115/IMECE2018-87661.

Enabling fast charging of Li-ion batteries (LiB) is essential for mainstream adoption of electric vehicles (EVs). A critical challenge to fast charging is lithium plating, which can lead to drastic capacity loss and safety risks. Fundamentally, fast charging is restricted by anode surface reaction kinetics, lithium diffusion in anode solid particles and Li+ diffusion and conduction in electrolyte. In this work, we present an analysis of the contributions of these different physicochemical processes to the total overpotential during fast charging, using an electrochemical-thermal (ECT) coupled model. Special attention is paid to the effect of increasing electrode thickness, a common approach for raising energy density of EV cells, on fast charging capability. It is found that lithium plating is more prone to occur in thicker anodes due to larger electrolyte transport resistance. Furthermore, we present a novel approach of thermal stimulation to enable 10-minutes (6C rate) fast charging of an EV cell with 170Wh/kg energy density.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A029. doi:10.1115/IMECE2018-88024.

The development of a novel electrochemical energy storage system, specifically a redox flow batteries (RFB), is discussed in this work. It has the distinction of not requiring an ion-selective membrane due to novel chemical compounds. The techno-economic aspects of a low-cost 3D printed flow cell and system design tailored for a novel chemistry is discussed. The organic compounds employed are inexpensive, have a long lifespan, and as mentioned enable the system to be membraneless. All these substantially decrease the capital and maintenance costs. Suitable systems were developed and tested using chemically compatible 3D printed materials for the flow cells. The estimated cost per kWh is lower than the Department of Energy’s target cost of $150/kWh for grid storage capacity. A commercial scale system, rated for a 1 MW, 5-hour discharge time, has an estimated cost of $65/kWh. The proposed technology could revolutionize the energy storage industry and help with the construction of a more stable and efficient energy grid.

Commentary by Dr. Valentin Fuster

Energy: Energy Systems Components

2018;():V06AT08A030. doi:10.1115/IMECE2018-86104.

To support the broader development of isothermal compressor technology for natural gas systems, an experimental system has been designed and constructed to determine void fraction of a gas over time. The goal of this project was to determine how much time it takes for a gas, already statured in a working fluid, to separate from the working fluid. The result is a pressure vessel paired with a data acquisition system that could operate at a maximum of 3600 psi. A medium and high pressure system were designed, and the medium pressure system has been tested using visual methods.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A031. doi:10.1115/IMECE2018-86463.

Oil injection is widely used in screw compressors for lubrication, sealing and cooling purposes. More recently other, mainly lower viscosity fluids are used for the purpose, for example water. Water introduces new phenomena into the screw compressor process, one among them is evaporation. 3D numerical modelling is employed and presented in this paper for the detailed analysis of flow and thermodynamics process during injection of water in screw compressors. The advantage of such simulations is that realistic geometry of the rotors and the ports can be captured. In addition, the physical effects of fluid thermal interactions and leakage are directly taken into account by these models. Recent studies have shown that for oil free and oil injected air compressors a good agreement is achieved with measurements, in prediction of performance parameters. In these simulations the Eulerian-Eulerian multiphase modelling has been applied. To implement the same model for water injected compressors presents an additional challenge as the liquid water injected into the compression chamber changes phase and evaporates depending on the local saturation and thermodynamic conditions. Water also forms liquid film on the rotors and housing and thereby influences thermal changes.

In this paper a numerical model for water injected screw compressor that accounts for evaporation effects has been presented. Empirical form of the Lee (9) evaporation-condensation model for phase change has been applied in the compression chamber using the phase specific mass and energy sources. Calculation of the amount of water required to just saturate the compressed air at delivery pressure is used to set the mass flow rate of water at two operating speeds. The effect of the suction air temperature and relative humidity is studied. Evaporation inside compression chamber has two important physical effects, one is that the latent heat of evaporating water lowers the gas temperature and the other is the change of state from water to vapour. Including vapour as a third phase adds complexity to already challenging deforming grids required for screw domains. Hence a mass and energy source formulation is proposed in the presented study to account for the vapour phase change and evaporation effects, thus limiting the number of phases to be modelled. Local drop in gas temperature, distribution of water and regions of evaporation were identified by the simulations. Thermal hot spots on the rotor were located. Reduction in the leakage of gas and its exit temperature was well predicted by the model. Such simplified evaporation model can be further used in the design of water injected screw compressors and extended to predict thermal deformation of the rotors and the housing.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A032. doi:10.1115/IMECE2018-86702.

The Stirling engine is a high efficiency and high reliability energy converter which is expected to be a solution for future space power generation and commercial applications. One of the key components in a Stirling engine, to keep high efficiency, is the regenerator. Currently, woven screens or random fibers are mostly used as the regenerator material. However, since both woven screen and random fiber regenerators are composed of wires, the flow across the wires is similar to cylinders in cross flows. As a result, flow separation occurs and the regenerator results in high friction losses and thermal dispersion. In the previous study, a robust foil type regenerator is designed and CFD analysis of the regenerator was conducted to predict the friction coefficient and the thermal efficiency under oscillating flow conditions. In this research, a regenerator test bench was designed and constructed to investigate the friction coefficient and thermal efficiency of the regenerator. The experiment conditions are decided based on the one-dimension thermodynamic modeling software SAGE. The experiment result shows that the friction coefficient of the experiment is close to CFD prediction at high Reynolds number.

Topics: Flow (Dynamics)
Commentary by Dr. Valentin Fuster
2018;():V06AT08A033. doi:10.1115/IMECE2018-86761.

Many off highway machinery companies have begun to transfer their products from hydraulic drives to electric drives, but there is not a clear study found in the literature that shows a comparison between these two drives in order to demonstrate the benefits for this transformation. In this paper, a nondimensional comparison between electric and hydraulic motors is made in terms of losses, efficiency, and energy consumption. The loss analyses for both types of motors is conducted and an efficiency map for these motors is produced. The energy consumption is compared for both motors for the same load during a common duty cycle.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A034. doi:10.1115/IMECE2018-87733.

The Measurement While Drilling (MWD) tool is used by oil and gas industry to provide the directional survey information while drilling. With rig rates exceeding $1 million per day and wells that are drilled at depths of over 30,000 ft (9144 m), operators needs to have an MWD tool that can self-power itself to provide high data rates and strong signal strength. Among different types of MWD tool, the Continuous Mud-Pulse Telemetry (C-MPT) can generate high data rates and signal strength. The C-MPT has a rotating valve that propagates signal upstream through the drilling fluid in the drill string. However, the ability to power a C-MPT for the MWD tool using the existing hydraulic forces of the drilling fluid has not been extensively researched. The focus of this study was to propose the 2-lobe and 3-lobe turbo siren designs that can provide power to an alternator while maintain high data rates and signal strength. All turbo siren designs are based on a vein, rotor, and stator. The turbo siren systems were manufactured with 3D printing. An experimental wind tunnel was designed and built to simulate the downhole drilling environment. The testing results of the turbo siren systems are presented and discussed, including no-load rotation speed (RPM), stall torque, power and data rate. The results provide the guidance for the optimization of the self-powered MWD turbo siren design.

Topics: Turbochargers , Design
Commentary by Dr. Valentin Fuster
2018;():V06AT08A035. doi:10.1115/IMECE2018-87852.

Minichannel tubes have been successfully integrated into automotive, aerospace and HVAC due to their performance superiority and cost effectiveness. Recently, they have also been introduced in the solar thermal industry for similar reasons. Considering the indirect and limited contact area for heat exchange between absorber and fluid in a conventional solar collector, a minichannel tube has the advantage of providing an absorber surface with large heat transfer area and has less thermal resistance. Due to the method of construction, in many cases, minichannel tubes are separated by a few millimeters from each other, leaving a gap in between tubes that wastes collector area. The addition of a back plate to these minichannel-tube collectors will enhance the thermal output as they together provide a larger surface area for absorption. This effectively increases the thermal output. However, the balance between heat transfer and pumping power needs to be analyzed, thereby the need arises to optimize these geometric parameters. This paper attempts to determine these performance values while optimizing the minichannel-tube geometry and back plate width. From energy analysis, it is deduced that a back plate of 40mm width with the corresponding hydraulic diameter for a constant heat exchange width of 100mm maximizes the thermal performance. The exergy analysis further shows that when the back plate width was between 40mm–45mm, maximum of 73% exergy efficiency can be achieved.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A036. doi:10.1115/IMECE2018-88067.

A membrane humidifier is a device to provide water vapor into the proton exchange membrane fuel cell stack that is used for transportation application due to global warming. Since inadequate humidification severely affects the performance and durability of a fuel cell stack, it is necessary to equip the humidifier for delivery humidification into the fuel cell vehicle.

In this study, the performance of humidification in hollow fiber membrane is investigated. While the test section is exposed to external humidity condition, dry air is provided through hollow fiber membrane so that the water transport is facilitated. Since various parameters can change the performance, the performance investigation has to be carried out with parameters. In this study the water transport of hollow fiber membrane is investigated in terms of principle operating conditions such as temperature, pressure, and flow rate.

Topics: Fibers , Membranes , Water
Commentary by Dr. Valentin Fuster
2018;():V06AT08A037. doi:10.1115/IMECE2018-88260.

A external methane-steam reformer is applied to fuel delivery of high temperature fuel cell system. When the reformer is equipped for high temperature fuel cell system, the heat supply of the methane steam reformer is critical to improve the system efficiency. Typically, system efficiency is improved as the waste heat is utilized. However, the general performance of steam reformer is designed to provide the rated performance at high temperature. In this study, characteristics of mid-temperature steam reformer are investigated. At mid-temperature operation of steam reformer, it is important to understand the performance of the reformer include inlet flow rate, temperature, and reformer geometry, and so on. Among them, the characteristics of the reforming catalyst are the most fundamental and most important in the performance of the reformer. Also, it is possible to optimize the performance of the reformer by understanding the reforming rate depending on the reformer inlet temperature, the amount of heat source, and the SCR (Steam to Carbon Ratio). Therefore, experimental study was carried out to understand the characteristics of the reforming catalyst. In order to carry out the experiment, the length of the reformer and the number of the heat source tubes were made variously so that the performance characteristics according to the volume of the reforming catalyst layer were confirmed. Through analysis of the experimental results, the characteristics of the reforming catalyst, which is an important factor in the performance of the reformer, can be understood under various conditions.

Topics: Temperature , Methane , Steam
Commentary by Dr. Valentin Fuster
2018;():V06AT08A038. doi:10.1115/IMECE2018-88526.

In the current study, CFD simulations and static structural analysis were carried out to estimate the wind loads for up and downstream wind directions on ground mounted arrayed solar panels. The goal of simulations is to estimate the loads (i.e. drag and lift forces and also moment coefficients) and wind pressure that act upon their surface. Static structural analysis coupled with CFD simulation is done to determine the total deformation due to wind loads on each panel. The motive of the study is to protect the integrity of the solar panels in a situation like cyclone and typhoon so that energy production is not hindered throughout their service life. Simulations were carried out on arrayed nine panels with changing various parameters (i.e. clearance height, inter row spacing between panels and panel inclination) that effect wind loading on the panels.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A039. doi:10.1115/IMECE2018-88689.

Free Piston Linear Engines and Alternators (FPLEA) may be designed following several different baseline configurations. Common designs include a translator that carries permanent magnets, with either one piston attached to one end of the translator, or a piston at each end of the translator. The single cylinder engine requires a reversing force from a spring so that it can operate whereas the dual cylinder version can operate without a spring, but inclusion of a stiff springs would serve to raise operating frequency. Higher spring constants drive higher frequencies and also reduce the variability of the FPLEA compression ratio. The major component choices include the use of one or two cylinders, a spring constant, a bore and a stroke, and volumetric heat release. For design, the alternator is a component with translating mass that depends by design on the frequency, stroke and electrical power. The alternator demand must be matched to the engine power or the operating condition will change for the next cycle. Though there are many different FPLEA configurations, the performance comparisons of several baseline configurations have not been completely explored. A MATLAB®/Simulink numerical model with translator rod dynamics and in-cylinder thermodynamics is employed to predict the overall performance and efficiency of diesel-fueled FPLEA. This allowed comparisons of different FPLEA configurations for a variety of design variables. First, a two-cylinder FPLEA design is considered where the spring constant is varied, changing the frequency of operation and the motion of the translator. The simulation results show that without springs the motion is far from sinusoidal, and low in frequency and power, whereas the presence of stiff springs in the system strongly dictates nearly sinusoidal motion and high power at high frequency. Further, Fourier coefficients are used to characterize the motion of springs for different configurations. Effects of other parameters such as stroke and bore are also examined. Comparison is also performed for competing designs with the same power, but with one or two cylinders. The results provide a basis for selecting major design parameters before proceeding with a detailed design.

Commentary by Dr. Valentin Fuster

Energy: Energy Systems for Buildings

2018;():V06AT08A040. doi:10.1115/IMECE2018-86033.

Buildings account for significant energy consumption worldwide particularly in regions where energy patterns influenced primarily by weather. Air conditioning system became an essential evaluation factor during building design and construction. The level of curiosity about air conditioning system efficiency in terms of energy usage is increasing quickly. In Kuwait; which is a hot climate country; air conditioners account for 70% of total electrical power. Electricity in Kuwait is produced entirely by the non-renewable energy resources. This work aims to assess the potential electrical savings that could be acquired by reducing building’s façade area towards East-West directional orientation in Kuwait. For this purpose, a detached building model with uniform geometry; was simulated by Energy Plus Thermal Simulation Engine through its interface with DesignBuilder software. Two cases were developed for the analysis; both have the same simulation inputs. The only difference was the orientation of the facades. The results show a reduction of about 900 kWh cooling annually if the largest facades were positioned towards north and south. The obtained saving in annual basis is attributed to about 420 kWh electrical power. Equivalent CO2 emissions associated with the saved electrical energy from power plants in Kuwait were estimated. The resulted savings are promising for early decision making for prospective buildings to be built in future.

Topics: Cooling
Commentary by Dr. Valentin Fuster
2018;():V06AT08A041. doi:10.1115/IMECE2018-86400.

This paper investigates a strategy for energy saving in the Italian residential sector that includes in the assessment the embodied energy related to the efficiency measures. Simulations are run in three main cities (Milan, Rome and Naples) covering different climate zones. The purpose is, firstly, to estimate the baseline of the buildings energy consumption, secondly, to simulate the implementation of realistic retrofit solutions and, finally, to assess the retrofitting’ embodied energy and its energy payback time.

The energy payback is based on the comparison between the net saved operational site energy and the embodied energy of the selected measures.

By running the simulations, it is possible to estimate the maximum potential for energy savings and realistic estimation of achievable results in short-medium period.

Results show the energy efficiency measures more convenient in terms of energy payback depending on the climate zone.

For Naples, a focus on façade insulation has been held and the results defined the optimal material thickness in terms of embodied energy and net saved operational site energy in a life cycle of 15 years.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A042. doi:10.1115/IMECE2018-86477.

Distributed electric generation systems are increasingly considered to offset energy costs and carbon emissions of large building complexes. College campuses, with their physical compactness, and diversity in building loads, present a common application for distributed generation systems. This paper presents the analysis approach and the main results of a feasibility study of a distributed generation system to supply electric and thermal energy for a large university campus, incorporating energy efficiency measures, to reduce carbon emissions at minimal life cycle cost.

The presented study uses a load profile developed based on calibrated detailed simulation energy models for prototypical campus buildings. The calibration analysis is carried out using measured energy consumption data, at the individual building level, and the whole-campus level. Several combinations of distributed generation options are evaluated, using an hourly optimization analysis tool, to meet the entire campus hourly electrical and thermal loads. Proposed efficiency measures and distributed generation options are evaluated using different indicators, including life cycle cost and carbon emissions.

The analysis results indicate that implementing energy efficiency measures to reduce electrical and thermal loads before implementing distributed generation options is the most cost-effective approach to reducing the campus’s energy-related carbon emissions. The results of the study are summarized to guide college campuses and managers of other urban districts as they adapt to a changing energy landscape.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A043. doi:10.1115/IMECE2018-86974.

This paper addresses the thermal performance of integrating Earth Air Heat Exchanger (EAHE) systems with the conventional air conditioning systems in residential buildings in UAE. The proposed system was designed and simulated using a transient analysis tool TRNSYS. The system components were optimized by evaluating the effect of varying several design parameters on the performance of the system. It was found that the optimized design of the earth tubes could potentially reduce the temperature of the ambient air from 46 °C to around 29 °C, when the earth tubes were buried at 4 meters depth below the ground surface. This pre-cooled fresh (atmospheric) air from earth tubes was then mixed with the return air in the mixing chamber of conventional air cooling systems before supply to the building. In order to assess the system feasibility, the proposed system was modelled and implemented on a realistic case study represented by a four-floor residential building located in Dubai. This building comprised a total roof area of 400 m2 and an annual cooling load requirement of 366 kW. The results showed good potential of savings in terms of lowering the Annual Energy Consumption (AEC) and the consequent reduction in CO2 emissions.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A044. doi:10.1115/IMECE2018-87051.

Solar chimney (thermal chimney) is a device which absorbs solar radiation to heat the air. The heated air, becoming buoyant, rises through the chimney’s passage and induces further air currents. When fitted to a building, solar chimney can thus induce fresh outside air to flow through the building for ventilation. Because only natural means (solar radiation here) are involved to cause the air flow, solar chimney is considered a natural-ventilation device. This work investigates computationally natural ventilation induced by a roof-mounted solar chimney through a real-sized 3-dimensional room, using a commercial CFD (Computational Fluid Dynamics) software package which employs the Finite Volume Method. Chien’s turbulence model of low-Reynolds-number K-ε is used in a Reynolds-Averaged Navier-Stokes (RANS) formulation. Computational domain that includes regions outside the room’s inlet opening and chimney’s exit allows for employing realistic boundary conditions for the computational model. Ventilation rate and air-flow pattern through the room are considered in terms of the location of the room’s inlet opening. It is found that while ventilation flow-rate through the room is higher with the room-inlet opening being located high on the wall opposite to the chimney’s entrance, a room-inlet opening being located near the ground results in better flow pattern with more flow through the living area in the lower part of the room.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A045. doi:10.1115/IMECE2018-87246.

An adsorption chiller is a type of chiller that uses heat input as the driving force for chemical compression of a refrigerant and provides cooling with low electrical consumption. An experimental setup was designed, instrumented, and constructed to meet constant inlet temperature and flow rate requirements for the commercially available adsorption chiller unit tested. Two types of tests were conducted, one with a constant hot water temperature which represents a district style heating system and another with a varying hot water temperature, representing a system using flat plate solar collectors. Numerous tests were run with constant inlet temperatures across the complete operating range of the chiller and at varying flow rates for each of the three main inputs. It was determined that variations in temperature had a much more significant impact on the performance of the chiller, compared to the variations in flow rate, which were almost negligible within tested range. Dynamic inlet temperature tests were run using the modified system which uses data from a weather file to simulate a system using flat plate solar collectors and vary the hot water inlet temperature to the system. The results showed that when the average hot water inlet temperature is lower than 60°C and higher than 75°C, the difference in performance between constant inlet temperature and dynamic inlet temperature tests was very small. However, the cooling capacity at 75°C was about 4 kWth greater than at 60°C. Majority of the test produced a thermal COP between 0.45 and 0.50. Therefore, based off the solar collector system’s capacity to maintain a suitable average hot water temperature, the cooling performance of the chiller can be deemed suitable for residential applications.

Topics: Cooling , Solar energy
Commentary by Dr. Valentin Fuster
2018;():V06AT08A046. doi:10.1115/IMECE2018-87340.

One of the important parameters in the reduction of greenhouse gas emission can be considered as the energy efficiency of the building. The building sector is constantly innovating in its use of materials with regards to sustainability. There is a need to use cost-effective, environmentally friendly materials and technologies which lessen the impact of a construction in terms of its use of non-renewable resources and energy consumption. For the reduction in energy consumption, thermally insulating materials can be installed inside the building envelope. It prevents heat loss and provides thermal comfort for the occupants. The introduction of the organic waste materials for thermal insulation is recent and little is known for their environmental effect in comparison with the conventional materials. Present study consists of experimental analysis to investigate the composition of wood powder and ash brick as a brick. Different modifications have been performed to determine the best methodology for the change in standard ash brick. The study has been concluded with the help of heat transmission factor and compressive strength.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A047. doi:10.1115/IMECE2018-87456.

Recent developments of plasmonic emitters that emit infra-red radiation in the range of 8–13 micron wavelengths that can be transmitted through the atmosphere have opened up the potential of cooling buildings passively by radiating heat through this atmospheric window into the deep space. This paper presents an analysis of the potential of this method to cool buildings radiatively 24 hours per day. Air conditioning units consume a large amount of electricity and are the main drivers of peak electricity loads. A transient thermal model of a building integrated radiative cooling (BIRC) system was carried out for passive radiative cooling of buildings. A MATLAB code was developed for solving the heat transfer model of the BIRC system using a numerical iterative approach. The effects of operating parameters such as cooling emissive power and ambient conditions on the performance of the system were studied. Furthermore, effects of non-radiative heat transfer processes were studied by considering different heat transfer coefficients. Based on this analysis, energy savings potential of radiative cooling of buildings was estimated for the climatic conditions of Miami, FL, and Chicago, IL, USA for a fraction of a roof surface covered with a radiative cooler. Further, the results of this analysis are in line with previous studies estimating the cooling potential of up to 100 W/m2 with radiative cooling systems. These results will help in estimating the economic value of cooling buildings by using plasmonic emitting surfaces on the building skins.

Topics: Cooling , Modeling
Commentary by Dr. Valentin Fuster
2018;():V06AT08A048. doi:10.1115/IMECE2018-87525.

The paper studies the ventilated façade as a potential alternative to conventional coating technologies for the thermal insulation of building’s external walls. The ventilated façade is modeled by means of a CFD approach that accounts for the full 3D-geometry of the building, the walls thickness and materials’ thermal properties. The effects of the windows on the heat losses and in the performance of the ventilated façade are modeled in order to accurately characterize the thermal behavior of the system. The solar radiative heat transfer during two representative days of the year is considered in the analysis and a multiband thermal radiation is adopted to capture the different nature of radiative heat exchange according to the light wavelengths.

The numerical approach enables to estimate the thermo-fluid dynamic behavior of the system and the temperature distribution and the velocity flow field within the air gap between the walls are addressed and their influence on the heat transfer through the building’s external walls is determined. The CFD analysis is employed to compare different configurations of the ventilated façade for improving the thermal insulation of the building; the performance of each scenario is determined in terms of electric energy and fuel consumption for the air conditioning and the heating system. Thus, the potential saving of the energy cost for ambient thermal conditioning is evaluated.

The analysis investigates the effects on the energy efficiency of different geometrical features of the system such as the height of the building and the air gap thickness and theoretical correlations are derived in order to estimate the best tradeoff between the energy efficiency of the building and the investment of the ventilated façade configuration.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A049. doi:10.1115/IMECE2018-87738.

This research analyzes the tidal effect in the thermal properties of the ground for a case study in Guayaquil, Ecuador. A thermal response test (TRT) performed near the shore of the Guayas river presented periodic fluctuations in the thermal behavior concurrent with the tide cycle. First, an analytical solution for tide-induced water table fluctuations was used for the determination of the phreatic level for the days of the test. The analytical model accounted for the horizontal distance from the shore, the ground porosity, and permeability. Afterward, a geometric mean model was used to predict the thermal conductivity of soil considering the groundwater level fluctuations. Finally, a correlation between the effective thermal capacity of the ground and the phreatic level in the soil was found.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A050. doi:10.1115/IMECE2018-88090.

To meet the increasing energy demand and to shave the peak, the Kingdom of Saudi Arabia (KSA) is currently planning to invest more on renewable energy (RE) seeking diversity of energy resources. Through the integration of demand side management measures and renewable energy distributed generation (DG) systems, the study outlined in this paper aims at investigating the potential of hybrid renewable energy systems in supplying energy demands for residential communities in an oil-rich country. The residential community considered in this study, located in the eastern region of KSA, has an annual electrical usage of 1,174 GWh and an electrical peak load of 335 MW that are met solely by the grid. The results of the analyses indicated that the implementation of cost-effective energy efficiency measures (EEMs) reduced electricity usage by 38% and peak demand by 51% as well as CO2 emissions by 38%. While, the analysis of the hybrid systems showed that purchasing electricity from the grid is the best option with a levelized cost of energy (LCOE) of $0.1/kWh based on the current renewable energy market and economic conditions of KSA, RE systems can be cost-effective to meet the loads of the residential communities under specific electricity prices and capital cost levels. This study can assist KSA decision makers establish effective and targeted policies that can facilitate and promote renewable technologies.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A051. doi:10.1115/IMECE2018-88211.

Heating, ventilation and cooling (HVAC) is the largest source of residential energy consumption in United States, encompassing about 25% of total residential energy usage. A significant portion of energy is wasted by unnecessary operation, such as overheating/overcooling or operation without occupants. Wasteful behaviors will consume twice the amount of energy compared to energy conscious behaviors. Many market programmable thermostats exist to address this problem, however, difficulties in persistent programming of such products and lack of understanding of underlying physics prevent users from achieving tangible impact. Hence, fully autonomous energy control system is desirable to engage as many people into energy conscious behaviors as possible. Occupancy measurement is necessary components to enable fully autonomous control. Occupancy information can save energy by automatically turn off the HVAC system when the building is not occupied, or floats to a more energy-efficient setback temperature when the activity level is low. A number of existing sensor solutions available on the market include Passive Infrared (PIR), ultrasonic, Bluetooth/GPS, and CO2 sensors, but these are either too expensive, not user-friendly, or limited in detection scope. These sensors are also incapable of detecting whether or not the occupant is an animal or a human. The work in this paper proposes an economical, reliable, non-invasive package to both detect human presence in a residence of a wide variety of geometries at the time and predict future occupancy pattern, by utilizing temperature sensors. To accomplish this, thermal sensors will be attached to both ends of door handles to collect the temperature data. This data will allow us to create a schedule to identify human activity leaving and exiting the space. At the same time, we will be collecting the skin temperature to determine the human activity level for better identification of the thermal comfort zone for occupants. The prediction model for occupancy pattern will be developed from previous data by using machine learning algorithm. For verification, experimental setup was built to verify our model by comparing actual human presence data from a house with the measured and predicted occupancy pattern from the temperature sensors. Future steps include implementing a data fusion scheme into the model to combine information from multiple types of sensors.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A052. doi:10.1115/IMECE2018-88359.

This study evaluates potential aggregate effects of net-zero energy home (NZEH) implementations on the U.S. electrical grid in a simulation-based analysis. The aggregate impact of large-scale NZEH implementations on the U.S. electrical grid is evaluated through a simulation-based study of prototype residential building models with distributed photovoltaic (PV) generation systems. An EnergyPlus residential prototype building model (i.e., a multi-family low-rise apartment building) is used to determine the detailed electricity consumption of each residential building model using U.S. climate weather files. This study assumes that net-metering is available on the electrical grid so that the surplus on-site electricity generation can be fed to the electrical grid. This study also considers the impact of electrical energy storage (EES) within NZEHs to effectively use on-site generated electricity on the electrical grid. Finally, surveyed residential building permits in 2017 are used to estimate net-electricity demand profiles of NZEHs on a national scale. Results indicate that adding distributed PV systems to enable annual multi-family NZEH performance can significantly increase changes in imported and exported electricity demand from and to the electrical grid during the daytime. However, using the EES within NZEHs helps reduce the peak electricity demand during the daytime. The stored electricity in the EES can also be used during the evening time. The peak net-electricity differences on the U.S. electrical grid-level could potentially be reduced during the daytime and shifted to the evening. Comparison of hourly electricity demand profiles for the actual U.S. demand versus the calculated net-demand on a national scale indicates that the percentage differences of U.S. net-electricity demand include about 4.5% and 4.8% for the multi-family NZEH without the EES on representative winter and summer days, respectively, at a maximum point. In addition, when the EES is added within the multi-family NZEH, the peak percentage differences could be reduced to about 3.4% and 4.3% on representative winter and summer days, respectively, at a maximum point.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A053. doi:10.1115/IMECE2018-88502.

With an increase in the need for energy efficient data centers, a lot of research is being done to maximize the use of Air Side Economizers (ASEs), Direct Evaporative Cooling (DEC), Indirect Evaporative Cooling (IEC) and multistage Indirect/Direct Evaporative Cooling (I/DEC). The selection of cooling configurations installed in modular cooling units is based on empirical/analytical studies and domain knowledge that fail to account for the nonlinearities present in an operational data center. In addition to the ambient conditions, the attainable cold aisle temperature and humidity is also a function of the control strategy and the cooling setpoints in the data center.

The primary objective of this study is to use Artificial Neural Network (ANN) modelling and Psychrometric bin analysis to assess the applicability of various cooling modes to a climatic condition. Training dataset for the ANN model is logged from the monitoring sensor array of a modular data center laboratory with an I/DEC module. The data-driven ANN model is utilized for predicting the cold aisle humidity and temperatures for different modes of cooling. Based on the predicted cold aisle temperature and humidity, cold aisle envelopes are represented on a psychrometric chart to evaluate the applicability of each cooling mode to the territorial climatic condition. Subsequently, outside air conditions favorable to each cooling mode in achieving cold aisle conditions, within the ASHRAE recommended environmental envelope, is also visualized on a psychrometric chart. Control strategies and opportunities to optimize the cooling system are discussed.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A054. doi:10.1115/IMECE2018-88518.

The growing world-wide energy demand and environmental considerations have attracted immense attention in building energy efficiency. Climate zone plays a major role in the process of decision making for energy efficiency projects. In the present paper, an office building located in Melbourne, FL is considered. The building is built in 1961 and the goal is to identify and prioritize the potential energy saving opportunities and retrofit the existing building into a Net-Zero Energy Building (NZEB). An energy assessment is performed and a baseline model is developed using eQUEST to simulate the energy performance of the building. Several possible energy efficiency improvement scenarios are considered and assessed through simulation including improving insulation on the walls and roof, replacing HVAC units and upgrade their control strategies, use of high efficiency lighting, and more. Selected energy efficiency improvement recommendations are implemented on the building model to achieve the lowest energy consumption. It is considered that photovoltaic (PV) panels will be used to supply the energy demand of the building. Simulations are also performed to determine the number of required PV panels and associated cost of the system is estimated. The results from this paper can help with the decision making regarding retrofit projects for NZEB in humid subtropical climate.

Topics: Structures , Climate
Commentary by Dr. Valentin Fuster

Energy: Energy-Related Multidisciplinary

2018;():V06AT08A055. doi:10.1115/IMECE2018-86242.

The sustainability of an energy-independent system with a relatively large heating load and that is driven by multiple renewable energy sources such as a photovoltaic battery and a biofuel generator has been investigated. The utilization of renewable energy has become one of the most important areas of interest for residential houses, as seen in zero energy house trends. In particular, technologies for energy-independent residential houses that can be categorized as off-grid systems have gained importance. In this paper, the design concept and the detail of the constructed pilot scale test system comprising a photovoltaic power (PV) generator and a biofuel power generator (BFG) are explained. Experimental results prove that continuous system operation is possible based on an effective control of these multiple renewable energy sources, even for relatively large heating loads. The results also imply that usage of multiple-source renewable energy is effective for the sustainable operation of an energy-independent residential house. Moreover, optimizing the energy consumption of the energy-independent system with heating is discussed. Here, mixed integer linear programming has been applied to the system driven by multiple renewable energy sources to optimize the sustainable operation of the system. The simulation results show that it is possible to reduce the cost incurred on biofuel by about 40% as compared with that of the system driven only by biofuel energy. Consequently, multiple sources of renewable energy are effective for the sustainable operation of an energy-independent residential house even with relatively large heating loads.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A056. doi:10.1115/IMECE2018-86562.

The continuous demand for oil and gas forces the petroleum industry to develop new and cost-effective technologies to increase recovery from new fields and enhance extraction from existing fields. Subsea wet gas compression stands out as a promising solution for increasing production capacity, utilizing remote regions and reducing costs.

A prerequisite for successful oil and gas production utilizing subsea wet gas compressors is operability. This includes the system’s ability to cope with operational changes, without having to shut down. One of the fundamental operational changes is the liquid content in the inlet pipe, which may fluctuate considerably at certain time intervals. The current study investigates how changes in liquid content impacts compressor performance.

An experimental test campaign has been performed at the Norwegian University of Science and Technology (NTNU). The test facility is an open loop configuration consisting of a single shrouded centrifugal impeller, a vaneless diffuser and a symmetrical circular volute.

The main objectives were to document how the presence of liquid impacts the compressor characteristics and further, how the operating point moves within the characteristics when solely subjected to an increase of liquid content. The compressor was exposed to liquid contents ranging from gas mass fraction 1.0 to 0.60. The test reveals that the compressor pressure ratio at wet conditions is higher in comparison to dry conditions. Care should be taken when analysing stability and surge margins at variations in fluid liquid content. Further, the compressor behaves in a predictable manner, revealing several linear trends, when subjected to stepwise changes in liquid content from a fixed operating point.

Topics: Gas compressors
Commentary by Dr. Valentin Fuster
2018;():V06AT08A057. doi:10.1115/IMECE2018-86717.

Contact angle measurements are important to determine surface and interfacial tension between solids and fluids. A ‘water-wet’ condition on the rock face is necessary in order to extract oil. In this research, the objectives are to determine the wettability (water-wet or oil-wet), analyze how different brine concentrations will affect the wettability, and study the effect of the temperature on the dynamic contact angle measurements. This will be carried out by using the Cahn Dynamic Contact Angle. Analyzer DCA 315 to measure the contact angle between different fluids such as surfactant, alkaline, and mineral oil. This instrument is also used to measure the surface properties such as surface tension, contact angle, and interfacial tension of solid and liquid samples by using the Wilhelmy technique. The work used different surfactant and oil mixed with different alkaline concentrations. Varying alkaline concentrations from 20ml to 1ml were used, whilst keeping the surfactant concentration constant at 50ml.. It was observed that contact angle measurements and surface tension increase with increased alkaline concentrations. Therefore, we can deduce that they are directly proportional. We noticed that changing certain values on the software affected our results. It was found that after calculating the density and inputting it into the CAHN software, more accurate readings for the surface tension were obtained. We anticipate that the surfactant and alkaline can change the surface tension of the solid surface. In our research, surfactant is desirable as it maintains a high surface tension even when alkaline percentage is increased.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A058. doi:10.1115/IMECE2018-86902.

Accurately online state of health estimation is one of the key issues in battery management system (BMS), which enable the batteries function safely and efficiently. With excellent performance in in-situ degradation modes detection and precise state of health estimation modeling ability, incremental capacity (IC) analysis is widely used to analyze the situation of aged batteries. This paper discussed the difficulties in IC analysis application at first, and a robust method is then proposed, which parameterize the IC curve with Gaussian function. Battery cycle life experiment is conduced to validate the feasibility and accuracy of the proposed method. A capacity is constructed based the parameters of Gaussian function in each peak. The results show that the model estimation error is less than 3% of normalized capacity in each aging state, promising to be implemented in real BMS.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A059. doi:10.1115/IMECE2018-86922.

Fuel supply system, the regulation system for fuel delivery to the combustor, is one of the most important auxiliary systems in a gas turbine engine. Commonly, the fuel supply system was always simplified as a linear system. In fact, gas turbine engines almost use a hydromechanical main fuel control system which consists of electro-hydraulic servo actuator and fuel metering unit. These components have several nonlinear characteristics such as hysteresis, dead zone, relay, and saturator. These nonlinear characteristics can directly affect the performance a gas turbine engine. In this paper, a three-shaft gas turbine engine was taken as a research object. Firstly, a mechanism model of the fuel control system considering the nonlinear links was developed based on the hydro-mechanical theory. Then, the effect of dead zone-relay characteristic of the servo amplifier in electro-hydraulic servo actuator was analyzed. The results show that the dead zone width has great effect on the dynamic performance of the gas turbine engine. The fuel flow rate will be oscillating with small dead zone width. The parameters of the gas turbine engine will be stable with the increase of dead zone width. However, the larger dead zone width causes the hysteresis and the increase of the dynamic response time. At the same time, an improvement method with a two-dimensional fuzzy compensation was proposed. The results show that the fuzzy compensation can effectively solve the oscillation problem caused by the dead zone-delay. Finally, a Hardware-In-the-Loop (HIL) system is developed which is based on an electro-hydraulic servo actuator facility and a real-time software component of the gas turbine engine. An experiment is conducted on the HIL test rig to validate simulation result. The results show that the experiment matches well with the simulation results.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A060. doi:10.1115/IMECE2018-87575.

Sustainable energy transition requires a critical prediction for the long-term evolvement of energy systems around the world. It is affected by several factors: the changes in the oil economy, the climate change, and the development of renewable energy supply technologies. The aim of this research is to compare and analyze Abu Dhabi’s generation sector in its transition from complete conventional gas to a mix of conventional and Photovoltaic (PV) energy systems. Employing a Mixed Integer Linear Program (MILP) and PLEXOS software, two capacity expansion scenarios of Abu Dhabi’s generation sector for five years are optimized, analyzed, and compared using a real data from the generation and demand sides. This research means to highlight, to the UAE government, the effect of introducing more renewable energy and to evaluate the performance of the generation side in meeting the forecasted demand. Furthermore, this work opens the doors wide for further development and optimization in the GCC area.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A061. doi:10.1115/IMECE2018-87610.

High voltage plasma-based technologies have the ability to impact multiple fields from medicine to engineering. The goal of the most recent study was to investigate the efficacy of a novel high voltage plasma system to generate oxygen (O2) from carbon dioxide (CO2) through dissociation. The general endothermic plasma-chemical process of CO2 decomposition is presented, with CO2 destruction accompanying production of oxygen (and carbon monoxide) at a mole ratio of 2 to 1. A high voltage plasma reactor was developed for this purpose. SEM analysis was conducted on electrodes used for plasma discharges, to better elucidate characteristics of the plasma. CO2 gas samples were analyzed using an FTIR spectrometer. Baseline scans were taken of CO2 inside the reactor before plasma power was turned on; subsequent scans were taken after 10 min of plasma treatment. Results of FTIR analysis presented here have indicated a 30% decrease in CO2 concentration upon application of the developed plasma reactor. This paper reports on various aspects of the instrumented high voltage plasma reactor; and experimental results which further explore the capability to decrease CO2 concentrations in various environments, while also generating O2.

Commentary by Dr. Valentin Fuster

Energy: Environmental Aspects of Energy Systems

2018;():V06AT08A062. doi:10.1115/IMECE2018-86126.

Computational models are developed to predict scale formations, compatibility and injection performance of produced water re-injection in mature hydrocarbon aquifer fields. The models are based on a robust numerical strategy that considered representative K-factors to predict correction for injectivity decline profiles. Simulations in COMSOL Multi-physics environment evaluate scaling effect to determine multi-reservoir commingling phenomenon in matured fields. Results demonstrated that geochemical scaling limit feasible and sustainable water injection performance that could impact petroleum recovery. Fracturing out of water zone was also significant near top and bottom interval cross flow of injection well requiring additional pressure of 100 to 200 psi to initiate fracturing. This requirement excluded fracturing in produce water most re-injection fields with attendant scaling effect.

Topics: Modeling , Water
Commentary by Dr. Valentin Fuster
2018;():V06AT08A063. doi:10.1115/IMECE2018-87374.

The twentieth century has seen a rapid twenty-fold increase in the use of fossil fuels. Personal and commercial transportation consumes 2% of the total world energy. The main products of combustion of fossil fuel are carbon mono oxide (CO), unburned hydrocarbons (HC), Carbon dioxide (CO2), oxides of sulfur (SOx), oxides of nitrogen (NOx) and particulate matter. Oxides of nitrogen (NOx) are the major diesel engine pollutants and referred to as mixtures of nitric oxide (NO) and nitrogen dioxide (NO2). NOx emissions are required to be controlled because NO and NO2 contribute to the formation of smog, an environmental and human health hazard. NO2 is also directly of concern as a human lung aggravation. To reduce NOx emissions from a diesel engine, the introduction of water in the combustion chamber of a diesel engine is a promising option as vaporization of water reduces adiabatic flame temperature and micro-explosion phenomena lead to improved mixing. In the present study, stable D/W emulsion, with varying water content, up to 3% were prepared using span 80 as a surfactant. The results indicated a reduction in NOx and smoke with increasing water volume fraction in the emulsion compared to diesel baseline. However, beyond 2% water content led to increased ignition delay and higher diffusion phase heat release resulting in noisy engine operation. Therefore, it can be concluded that diesel-water emulsion with 2% water could be used for significant reduction of NOx emissions from diesel and biodiesel operation of a CI Engine.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A064. doi:10.1115/IMECE2018-87732.

Climate change is a serious threat to sustainability. Anthropogenic climate change is due to the accumulation of greenhouse gases (GHG) in the atmosphere beyond natural levels. Anthropogenic GHG emissions are mostly associated with carbon-dioxide (CO2) originated in the combustion of fossil fuels used for heat, power, and transportation. Globally, transportation contributes to 14% of the global GHG emissions.

The transport sector is one of the main contributors to the greenhouse gas emissions of Ecuador. In Guayaquil, the road mass transportation system comprises regular buses and the bus rapid transit (BRT) system. Electricity in Ecuador is mostly derived from hydropower, hence incurs relatively low GHG emissions along its life cycle. Therefore, electrification of transport has been seen as an opportunity for mitigation of GHG emissions.

In this study, the effect of partial replacement of the bus rapid system fleet is investigated. Feeders have been chosen as the replacement target in five different scenarios. GHG emissions from diesel-based feeders have been calculated using the GREET Fleet Footprint Calculator tool. The GHG emissions associated with the electricity used for transportation is calculated using the life cycle inventory of the electricity generation system of Ecuador. Three energy mix scenarios are used for this purpose. The 2012 mix which had 61% hydropower; the mix of 85% hydropower and the marginal electricity scenario, which supposed the extreme case when the new demand for electricity occurs during peak demand periods.

Results indicate that mitigation of GHG emissions is possible for almost all scenarios of percentage fleet replacement and all mix scenarios. Electric buses efficiency and the carbon intensity of the electricity mix are critical for GHG mitigation.

Commentary by Dr. Valentin Fuster

Energy: Fuel Cell Systems Design and Applications

2018;():V06AT08A065. doi:10.1115/IMECE2018-86579.

Liquid water management is critical for Proton Exchange Membrane (PEM) fuel cell operation, as excessive humidity can lead to flooding and cell performance degradation. Water is produced in the cathode catalyst layer during the electrochemical reaction. If reactant gas streams become saturated, liquid water forms and must travel through anode and cathode Gas Diffusion Layers (GDLs) to reach flow channels for removal. Understanding the dynamic behavior of the droplet is critical to improve water removal strategies for PEM fuel cells. In this study a 3D, transient, two-phase model based on the Volume of Fluid (VOF) method was developed to study a single droplet in the gas channel. The formation, growth, and breakup of the droplet is tracked numerically and analyzed. The pressure drop across the droplet is monitored over time and compared with theoretical analysis. The droplet size and shape change over time for two different pore sizes are compared. The impact of various gases including air, helium, and hydrogen on droplet dynamics is presented. The viscous force and pressure force on the droplet and the drag coefficient are calculated.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A066. doi:10.1115/IMECE2018-86685.

The purpose of this study is to investigate the dynamic behavior of a Solid Oxide Steam Electrolyzer (SOSE) system without an external heat source which uses transient photovoltaic (PV) generated power as an input to produce compressed (to 3MPa) renewable hydrogen to be injected directly into the natural gas network. A cathode-supported crossflow planar Solid Oxide Electrolysis (SOE) cell is modeled in a quasi-3D thermo-electrochemical model that spatially and temporally simulates the performance of a unit cell operating dynamically. The stack is comprised of 2500 unit cells that are assumed to be assembled into identically operating stacks, creating a 300kW electrolyzer stack module. A 15-minute resolution dataset for operation of PV generation was obtained from a database that archives PV power dynamics of systems on the University of California, Irvine campus. The dataset (comprised of data for approximately 4.1 MW of peak solar power) was scaled to a maximum of 450kW of PV generation. For the designed 300kW SOSE stack (thermoneutral voltage achieved at design steady state conditions), powered by the dynamic 0–450kW output of PV systems, thermal management and balancing of all heat supply and cooling demands is required based upon the operating voltage to enable efficient operation and prevent degradation of the SOSE stacks. The PV generation dataset was analyzed to obtain a day in which the PV generated power has its highest dynamic behavior (a cloudy day) and another day in which the PV generated power and energy is maximum (a sunny day). Dynamic system simulation results show that the SOSE system is capable of following the dynamic PV generated power for both of these days while the SOSE stack temperature gradient is always maintained below a maximum set point along the stack for both days. The system efficiency based upon lower heating value of the generated hydrogen is between 0–75% and 0–78% with daily hydrogen production of 94kg and 55kg for sunny and cloudy days, respectively.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A067. doi:10.1115/IMECE2018-87770.

A major challenge with complex cyber-physical systems stems from long model computational time that creates a mismatch between the model system and the physical system. The numerical modeling of solid oxide fuel cells (SOFCs) presents particular challenges due to the highly coupled nature of the underlying equations and the multiphysics needed to fully resolve their behavior during a transient event. To this end current approaches revolve around splitting the computational efforts into resolving temperature effects and resolving electrochemical effects. Current methods employed for the transient simulation of an SOFC for implementation in the Hybrid Performance (HyPer) facility cyberphysical plant at the National Energy Technology Laboratory reveal a distinct need for accelerated results with a high degree of stability. To this aim, an investigation into the computational time for the code reveals that the underlying electrochemical algorithm takes an order of magnitude more time than its thermal counterpart and has a tendency to vary in terms of iteration time and as such a rework of the underlying system is proposed.

The primary method for accelerated electrochemical algorithm solutions is to employ higher order root finding recipes for the resolution of the highly coupled electrochemical equations. This is done with the intention to reduce the overall number of subiterations necessary for resolving voltage, current density, and species concentration, properties of the fuel cell that are all directly coupled and require nested iterative approaches. The overall objective of this approach is an order of magnitude reduction in calculation time without sacrificing stability and increasing accuracy. Specific approaches involve using both bounded and unbounded techniques, such as the False Position method and the Secant method (or if applicable Newton-Raphson) respectively, the drawbacks being slower convergence for False Position and instability for the Secant or Newton-Raphson methods.

Current preliminary results on simplified versions of the parent functions involved for electrochemical calculations indicate a reduction in computational steps by a factor of two for the secant method and a factor of three for Newton-Raphson. When implemented into new modified electrochemical algorithms, the results indicate a possible order of magnitude reduction in calculation time.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A068. doi:10.1115/IMECE2018-88119.

An exergy based analysis of the Environmental Control and Life Support System (ECLSS) aboard the International Space Station (ISS) is conducted to assess its overall performance. Exergy is chosen as a measure of performance because it accounts for both the first and second laws of thermodynamics. The exergy efficiency of a system is first defined as the total exergy destroyed by the system relative to the total exergy input to the system. To determine the ECLSS exergy efficiency, the system is divided into constituent subsystems which in turn are divided into assemblies and components. Based on this system decomposition, exergy balances are derived for each assembly or component. Exergy balances and supporting calculations are implemented in MATLAB® code. The major subsystems of the ECLSS considered in this analysis include the Atmosphere Revitalization Subsystem (ARS), Atmosphere Control and Supply Subsystem (ACS), Temperature and Humidity Control Subsystem (THC), Water Recovery and Management Subsystem (WRM), and Waste Management Subsystem (WM). This paper focuses on the ARS and its constituent assemblies and components. Exergy efficiency of the ARS and its constituent assemblies and components is first presented. The Oxygen Generation Assembly (OGA), an assembly within the ARS, is then highlighted because the exergy destruction by the OGA is a large magnitude contributor to the overall exergy destruction of the ECLSS. The OGA produces oxygen to meet the crew’s metabolic demand via water electrolysis in a proton exchange membrane (PEM) electrolyzer. The exergy destruction of the OGA’s PEM electrolyzer is a function of the amount of oxygen produced, which determines the necessary current density and voltage drop across the PEM electrolyzer. In addition, oxygen production in the PEM electrolyzer requires deviation from the Nernst potential, presenting trade-offs between the exergy efficiency and critical life support functions. The results of parametric studies of PEM electrolyzer performance are presented with an emphasis on the impacts of polarization and operational conditions on exergy efficiency.

Commentary by Dr. Valentin Fuster
2018;():V06AT08A069. doi:10.1115/IMECE2018-88271.

Hydrogen has often been studied as a possible fuel of the future due to its capabilities to support zero emissions and sustainable energy conversion. Hydrogen can be used in a fuel cell to generate electricity at high efficiencies and with zero emissions. In addition, hydrogen can be renewably produced via electrolysis reactions that are powered from otherwise curtailed renewable energy. One possible means of storing and delivering renewable hydrogen is to inject it into the existing natural gas (NG) system and thus decarbonize gas end-uses. The NG system has potential to serve as a storage, transmission and distribution system for renewably produced hydrogen. Despite the potential of hydrogen to reduce the carbon intensity of the NG system, the unique characteristics of hydrogen (low molecular weight, high diffusivity, lower volumetric heating value, propensity to embrittle pipeline materials) has led to justified concerns over the safety of introducing hydrogen blends into the NG system. While many studies have attempted to quantitatively predict leakage rates of hydrogen using classical fluid mechanics theories, such as Hagen-Poiseuille flow, there have been limited studies which quantitatively assess gaseous fuel leakage to support the predictions made from theoretical analyses and computations. In this paper we present a summary of the literature related to gaseous fuel leakage and results from preliminary experiments which support the idea that entrance effects may significantly affect gaseous fuel leakage from practical leak scenarios such as NG fittings, resulting in similar leakage rates between hydrogen and NG.

Topics: Fuels , Natural gas , Leakage
Commentary by Dr. Valentin Fuster
2018;():V06AT08A070. doi:10.1115/IMECE2018-88388.

Three-dimensional (3D) complex flow-fields of proton exchange membrane (PEM) fuel cells have attracted much attention owing to their excellent liquid water management and mass transport. However, due to their complex flow structure, PEMFCs with 3D complex flow-fields suffer from large pressure drops (> 0.1 bar) and hence large density variations along the flow direction, especially at high current density operations. In this work, the effect of gas density variation due to the frictional pressure loss is considered in the current three-dimensional computational model using the multi-phase mixture (M2) formulation, in order to elucidate the effect of frictional loss on cell performance. The current work shows that the gas density drop in flow-fields can be significant at high current densities (20% at 3.0 A cm−2 and 30% at 4.0 A cm−2) and causes gas flow expansion, resulting in better liquid water management in flow-fields and gas diffusion layers (GDL) due to the gradually increasing gaseous viscous force along the flow direction. However, it is also pointed out that the gas density drop in cathode flow-fields results in cell performance loss due to lower oxygen concentrations (15mV voltage loss at 0.5 bar pressure drop, 60mV voltage loss at 0.78 bar pressure drop).

Commentary by Dr. Valentin Fuster

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