bluuebunny/crossref_metadata_2025 huggingface dataset:
CBM Liquefaction Processes Integrated With Adsorption Separation of Nitrogen
Authors: Gao Ting , Lin Wensheng , Gu Anzhong , Gu Min
Published: June 2009

Coalbed methane (CBM) is a kind of important energy resources in the world. Liquefaction is a good option for recovery of CBM. Generally, CBM consists of a lot of nitrogen besides methane, which is usually required to be separated by adsorption before liquefaction, or by distillation after liquefaction. For the CBM adsorption-liquefaction processes, two novel processes are proposed, which integrate the two parts of adsorption and liquefaction together by utilizing the residue pressure of the waste nitrogen: the released nitrogen expanded directly to precool CBM, or further compressed and then expanded to liquefy CBM. Taking the unit product liquefaction power consumption as the major index and nitrogen content of CBM feed gas together with residue pressure of waste nitrogen as variables, the system performance of these two integrated processes is studied and compared with that of the nitrogen expansion liquefaction process without integration. By simulation and calculation with HYSYS, it is confirmed that system power consumption can be reduced by both methods to utilize the residue pressure, and for CBM with high nitrogen content, the energy conservation effect is considerable, furthermore, it is better to use waste nitrogen to precool CBM than to liquefy it.
An Integrated Evaluation Method for Energy Supply System
Authors: Zhang Chun-Fa , Wang Jiang-Jiang , Jing You-Yin , Zhang Xu-Tao
Published: June 2009

The introduction of sustainable energy systems is strongly associated to what choices real estate owners make among different energy supply system options. This paper reviews briefly the evaluation criteria and methods of energy supply system, from technical, economical, environmental and social aspects. A new methodology for the integrated evaluation of the energy supply system’s feasibility is presented, which adopts the grey relational analysis method. As an example, three energy supply systems to provide cooling, heating and power to users are synthetically evaluated and compared in multi-criteria. The weights, used in multi-criteria evaluation, is discussed and suggested. The results prove that the grey relational analysis is an effective tool for decision making compared to single criteria evaluation.
Cost/Performance Tradeoffs for Reflectors Used in Solar Concentrating Dish Systems
Authors: Andraka Charles E.
Published: June 2009

Concentrating Solar Power (CSP) dish systems use a parabolic dish to concentrate sunlight, providing heat for a thermodynamic cycle to generate shaft power and ultimately, electricity. Currently, leading contenders use a Stirling cycle engine with a heat absorber surface at about 800°C. The concentrated light passes through an aperture, which controls the thermal losses of the receiver system. Similar systems may use the concentrated light to heat a thermochemical process. The concentrator system, typically steel and glass, provides a source of fuel over the service life of the system, but this source of fuel manifests as a capital cost up front. Therefore, it is imperative that the cost of the reflector assembly is minimized. However, dish systems typically concentrate light to a peak of as much as 13,000 suns, with an average geometric concentration ratio of over 3000 suns. Several recent dish-Stirling systems have incorporated reflector facets with a normally-distributed surface slope error (local distributed waviness) of 0.8 mrad RMS (1-sigma error). As systems move toward commercialization, the cost of these highly accurate facets must be assessed. However, when considering lower-cost options, any decrease in the performance of the facets must be considered in the evaluation of such facets. In this paper, I investigate the impact of randomly-distributed slope errors on the performance, and therefore the value, of a typical dish-Stirling system. There are many potential sources of error in a concentrating system. When considering facet options, the surface waviness, characterized as a normally-distributed slope error, has the greatest impact on the aperture size and therefore the thermal losses. I develop an optical model and a thermal model for the performance of a baseline system. I then analyze the impact on system performance for a range of mirror quality, and evaluate the impact of such performance changes on the economic value of the system. This approach can be used to guide the evaluation of low-cost facets that differ in performance and cost. The methodology and results are applicable to other point- and line-focus thermal systems including dish-Brayton, dish-Thermochemical, tower systems, and troughs.
Effects of High Figure of Merit Bi2Te3 Based Superlattices on Thermoelectric Power Generation
Authors: Howells Christopher A. , Watkins Cynthia , Venkatasubramanian Rama
Published: June 2009

We have investigated the power generation characteristics of thermoelectric devices made from high Figure of Merit p-type Bi2Te3/Sb2Te3 and n-type Bi2Te3/Bi2Te2.7Se0.3 superlattice materials. The Figure of Merit, ZT (where Z is a measure of the material’s thermoelectric properties and T is the absolute temperature) of the p-type and n-type superlattices were each measured at 300K and found to be 2.4 and 1.2 respectively [1]. Sixteen p-n couples were developed using these superlattice materials and they were configured into a 4×4 thermoelectric module. The electrical measurements (Current, Voltage, and Power) of the 4×4 superlattice thermoelectric modules under various resistive loads and temperature differentials in a standard pressure environment are presented and from these, we have determined the peak power and internal resistance of the module. We also discuss other opportunities to further investigate this device as well as its suitability for power applications.
Predicted Performance of an Integrated Solar Thermal and Photovoltaic System With Hybrid Turbine-Fuel Cell Cogeneration System
Authors: Kowalski Gregory J. , Zenouzi Mansour
Published: June 2009

A general approach, the HLRP technique, for determining the performance of a hybrid turbine-fuel cell cogeneration system with a renewable energy sources is presented for a domestic residence. The hybrid-cogeneration system provides the electric power as well as satisfying heating loads. In this paper a system level analysis that includes practical values of heat exchangers, pumps, and storage equipment is presented. The use of the ratio of the thermal load to required power parameter (HLRP), which has been used by the authors to scale energy systems, allows the performance to be quickly determined and preliminary carbon dioxide production rates and cost effects to be estimated. The present paper includes solar energy systems as renewable energy to illustrate the development of this technique and its integration with the hybrid fuel cell cogeneration system. Practical values of solar collector efficiency and storage tank and battery storage efficiency are included. The analysis focused on matching the transient characteristics of the power and thermal loads with those of the renewable energy system. The results demonstrate that for a typical winter day in the location studied there are not large variations in the energy utilization factors for the four different systems investigated. There is a 23% reduction in the carbon dioxide produced using the solar thermal or combined system as compared to the no renewable energy or photovoltaic systems. The information provided by the performance graphs is used to estimate costs for each system and to easily determine which system is the most efficient for satisfying energy requirements and reducing green house gas emissions. The results provide site planners and physical plant operators with initial information that can be used to design new facilities or effectively integrate large plant expansion that include renewable energy systems in a manner that will minimize energy requirements and reduce pollution effects.
Solar Flash Desalination Under Hydrostatically Sustained Vacuum
Authors: Abutayeh Mohammad , Goswami Yogi
Published: June 2009

Creating vacuum conditions above liquids increases their evaporation rates. This phenomenon can be integrated into a practical continuous desalination process by repeatedly flashing seawater in vacuumed chambers to produce water vapor that condenses afterwards producing fresh water. Gravity can be used to balance the hydrostatic pressure inside the flash chambers with the outdoor atmospheric pressure to maintain that vacuum, while low grade solar radiation can be used to add heat to seawater before flashing. The proposed desalination system consists of a saline water tank, a concentrated brine tank, and a fresh water tank placed on ground level plus an evaporator and a condenser located several meters above ground. The evaporator-condenser assembly, or flash chamber, is initially filled with saline water that later drops by gravity creating a vacuum above the water surface in the unit without a vacuum pump. The vacuum is maintained by the internal hydrostatic pressure balanced by the atmospheric pressure. The ground tanks are open to the atmosphere, while the flash chamber is insulated and sealed to retain both heat and vacuum.
Optimization for Heating System Schemes Based on GRA Method
Authors: Bing Wei , Li Li
Published: June 2009

In China, the overall economical performances of heating systems are not very high, there are still some problems of high energy consumption, high gas emission and low heat utilization. The energy conversation and emission reduction are two most important things. The option of the heating system schemes is the key to improve such situation. An optimal heating scheme will be a good beginning to the whole heating system. In this paper, the GRA (Grey Relation Analysis) method is introduced and used, and with the example of a heating district, the most used and upcoming used heating schemes are listed, calculated and compared by using the method of GRA. The option of a heating system scheme is a typical multi-objective decision-making problem. The schemes are the district boiler heating system (including gas-fired, oil-fired, and coal-fired boilers), solar energy heat pump system and combined heating and power system etc. In the process of optimization calculation, the aspects of energy saving, economics benefit, environment benefit and social benefit are concerned about, and the initial cost, operating cost, employment life, environment influence and system reliability are taken into account. According to the calculation results, combined heating and power system is proposed to be optimal heating system scheme.
Effect of Operation Conditions on Hydrogen Production by PSB in Immobilized-Cells Packed Bed
Authors: Wang Y. Z. , Liao Q. , Zhu X. , Tian X.
Published: June 2009

Effect of multiple operation conditions on behaviors of H2 production from organic substrate by photo-fermentation in immobilized-cells packed bed using Rhodoseudomonas palustris CQK 01 were investigated in a continuous culture. It revealed that in limited light intensity or below 590 nm of light wavelength the H2 production rate of the immobilized-cells bioreactor increased with increase of value of the experimental parameters. And the optimal operation factor of inlet concentration of substrate and inlet temperature of liquid for H2 production was 50 mmol/L and 30 °C, respectively. However, when these parameters value in the experiment became suppressive conditions the H2 production rate would went down with parameter ascending.
Application of Entropy Method in Fuzzy Synthetic Evaluation for Micro-Turbine Performance
Authors: Shi Guohua , Jing Youyin , Wang Songling , Gao Yuefen
Published: June 2009

Distributed generation (DG) is becoming the indispensable supplement to the centralized generation. Micro-turbine is paid more and more attention in scientific research and commercial application due to its unique advantages and gradually becomes the core of distributed generation. It is essential to make a synthetic and scientific evaluation on the performance of micro-turbine in order to promote the progress of the distributed generation technology using micro-turbine. This article gives the synthetic performance evaluation of micro-turbine. Some performance characters (rated capacity, generating efficiency, rotation speed, pressure ratio, fuel consumption, multi-fuel, intake temperature, exhaust temperature, NOx emission level, noises and life time) were chosen as evaluating indicators and some common micro-turbines were taken as evaluating objects in this paper. Considering the difficulty of fuzzy synthetic evaluation method in calculation of the multiple factors and the ignorance of the relationship among evaluating objects, a new weight evaluation process using entropy method was introduced. The entropy method is an objective way for weight determination. The improved method for weight determination of the evaluating indicators was applied in performance assessment of the micro-turbines. The evaluation result of the example showed that this method was favorable for fuzzy synthetic evaluation when there was more than one evaluating objects and the entropy method for determination of weight was a very effective method for evaluating indicators. The method predigested the fuzzy synthetic evaluation process greatly and the evaluation results are more reasonable.
Design and On-Sun Testing of a Solid Particle Receiver Prototype
Authors: Siegel Nathan , Kolb Greg
Published: June 2009

A prototype direct absorption central receiver, called the solid particle receiver (SPR), was recently built and tested on-sun at Sandia National Laboratories. The SPR consists of a 6 m tall cavity through which a 1 m wide curtain of spherical ceramic particles is dropped and directly heated with concentrated solar energy. The focus of this current effort is to provide an experimental basis for the validation of computational models that have been created to support the development of the solid particle receiver as a solar interface for thermochemical hydrogen and solar power systems. In this paper we present detailed information on the design and construction of the receiver as well as test data including the temperature change of the particles and internal cavity walls. We conclude with a discussion of the steps needed to demonstrate the overall feasibility of the SPR concept.
What is the Best Solution to Improve Thermal Performance of Storage Tanks With Immersed Heat Exchangers: Baffles or a Divided Tank?
Authors: Wade Aaron D. , Davidson Jane H. , Haltiwanger Julia F.
Published: June 2009

Prior studies of indirect water storage tanks that employ an immersed heat exchanger to discharge the stored energy have identified two potential methods of improving the rate of energy extraction: 1) an internal baffle to increase the velocity across the heat exchanger, and 2) a divided storage compartment to achieve thermal stratification. Thermal performance of these two options is compared to that of a conventional cylindrical tank during transient discharge. Each tank has a storage volume of 350 liters and a 10 m long, 0.3 m2 coiled tubular heat exchanger. For the specific configurations evaluated, the baffled heat exchanger provides the highest energy delivery rates and heat exchanger outlet temperatures. An analytic model shows the advantage of the divided storage depends on the NTU of the immersed heat exchanger. The heat exchanger employed in the present study is too small to realize the potential benefit of a divided storage. Both options, if used in the appropriate system, can improve thermal performance as measured by the rate and quality of delivered energy. The baffle is most appropriate when storage-side natural convection is the largest thermal resistance of the heat exchanger. The divided tank is useful when the NTU of the heat exchanger exceeds three.
CFD Analysis of the Cool Down Behaviour of Molten Salt Thermal Storage Systems
Authors: Schulte-Fischedick Jan , Tamme Rainer , Herrmann Ulf
Published: June 2009

CFD analysis has been conducted to obtain information on heat losses, velocity and temperature distribution of large molten salt Thermal Energy Storage (TES) systems. A two-tank 880 MWh storage system was modeled according to the molten salt TES containment design proposed for the 50 MWel commercial parabolic trough solar thermal power plants in Spain. Heat losses were established using the Finite Element Method (FEM), and used to determine the boundary conditions for the subsequent two- and three-dimensional Computational Fluid Mechanics (CFD) calculations. The investigations reveal that a high heat loss flux occurs at the lower edges of the salt storage tanks (between side wall and bottom plate). Thus the maximum temperature difference can be found at this location, resulting in the onset of local solidification within 3.25 days in the case of the empty cool tank. As a consequence, the detailed design of the lower edge has a large impact on both the overall heat losses and the period until the onset of local solidification.
Simulation and Experimental Analysis of a Solar Driven Absorption Chiller With Partially Wetted Evaporator
Authors: Albers Jan , Nurzia Giovanni , Ziegler Felix
Published: June 2009

The efficient operation of a solar cooling system strongly depends on the chiller behaviour under part-load conditions since driving energy and cooling load are never constant. For this reason the performance of a single stage, hot water driven 30 kW H2O/LiBr-absorption chiller employed in a solar cooling system with a field of 350 m2 evacuated tube collectors has been analysed under part-load conditions with both simulations and experiments. A simulation model has been developed for the whole absorption chiller (Type Yazaki WFC-10), where all internal mass and energy balances are solved. The connection to the external heat reservoirs of hot, chilled and cooling water is done by lumped and distributed UA-values for the main heat exchangers. In addition to an analytical evaporator model — which is described in detail — experimental correlations for UA-values have been used for condenser, generator and solution heat exchanger. For the absorber a basic model based on Nusselt theory has been employed. The evaporator model was developed taking into account the distribution of refrigerant on the tube bundle as well as the change in operation from a partially dry to an overflowing evaporator. A linear model is derived to calculate the wetted area. The influence of these effects on cooling capacity and COP is calculated for three different combinations of hot and cooling water temperature. The comparison to experimental data shows a good agreement in the various operational modes of the evaporator. The model is able to predict the transition from partially dry to an overflowing evaporator quite well. The present deviations in the domain with high refrigerant overflow can be attributed to the simple absorber model and the linear wetted area model. Nevertheless the results of this investigation can be used to improve control strategies for new and existing solar cooling systems.
Integrated Energy Strategy: A Case for Sustainability
Authors: Hobbs Raymond
Published: June 2009

The Integrated Energy Strategy (IES) is a systemic approach to pursue several goals by applying technologies that have not been integrated before. The concept was to maximize the use of proven technologies that reduce the risk while focusing on the key enabling developments that leverage the benefits of a systems approach. Each of the component operations illustrated in the paper will be part of the US energy infrastructure in the future. Additional economies of scale and advantages of earlier availability result from the APS-NETL approach. The future of America’s energy infrastructure must support utilities becoming leaders in transitions rather than just forced customers of risky solutions.
Energy Saving Potentials of All Cold Air Distribution System With Stratified Air Conditioning in Large Space Building
Authors: Bing Wei , Li Li , Gao Yuefen , Yang Xianliang
Published: June 2009

So far the energy saving potentials in refrigeration and air conditioning systems are the focuses of researchers all over the world. The all cold air distribution systems are being widely used due to the advantages of saving building space, less energy consumption in some given conditions and less initial cost, mostly in the residential or office buildings. The stratified air conditioning technology is adopted mainly for large space buildings to reduce the system energy consumption, normally at conventional supply air temperature. In this paper, with an example of large space building, the energy consumptions of four all outdoor air systems are calculated and compared from the view of the total annual primary energy consumption. The detailed analysis shows that comparing the conventional all outdoor air system for the whole indoor space or that with stratified air conditioning technology, the all cold outdoor air system with stratified air conditioning has the energy saving potentials. It will be promoted in the future application of HVAC systems in large space buildings.
Indoor Environment Numerical Simulation of All Cold Air Distribution System With Stratified Air Conditioning
Authors: Bing Wei , Li Li , Lu Jiang , Wei Zhang
Published: June 2009

At present all cold air distribution systems are being used widely due to their advantages of smaller ductwork, shorter floor-to-floor height and less energy consumption etc. They are mostly used in VAV (Variable Air Volume) systems or with the radiant panel systems in the office and residential buildings at the supply air dew point temperature of 6∼10°C, rarely used in large space buildings. The technology of stratified air conditioning is one of the energy saving technologies to large space buildings, which has been popularly used in the conventional air supply systems with the supply air dew point temperature of 11∼16°C. In this paper, the cold air distribution system and the stratified air conditioning technology in a large space building are combined to study. With the method of CFD, the indoor thermal environment of a large space workshop is simulated. The velocity and the temperature as well as the relative humidity fields under different air flow modes are presented, analyzed and compared. With the help of numerical simulation results, the optimal airflow mode is proposed, which show that the all cold air distribution with the stratified air conditioning is a good option for large space buildings. All these above will be good references to the application of cold air distribution system and the selection of the airflow mode in large space buildings.
Utilization of Heat, Power and Recovered Waste Heat for Industrial Processes in the US Chemical Industry
Authors: Ozalp Nesrin
Published: June 2009

This paper presents energy end-use model of the U.S. Chemical Industry. The model allocates combustible fuel and renewable energy inputs among generic end-uses including intermediate conversions through onsite power and steam generation. Results of this model provide the basis to scale energy process-step models. Two federal databases used to construct energy end-use models are Manufacturing Energy Consumption Survey of the U.S. Energy Information Administration, and the Energy Information Administration’s “EIA-860B: Annual Electric Generator Report”. These databases provide information on energy consumption for each end-use, electricity generation, and recovered waste heat at the prime mover level of detail for each industry on a national scale. Results of the model show that the majority of the fuel input is used directly for the end-uses. Although the rest of the fuel is used to generate steam and power, most of this energy contributes to the end-uses as steam. Therefore, the purpose of fuel consumption at non-utility plants is to run their end-uses. During the course of this study, the most recent U.S. federal energy database available was for the year 1998. Currently, the most recent available U.S. federal energy database is given for the year 2002 based on the data collected from 15,500 establishments.
Energy Process-Step Model of Hydrogen Production in the US Chemical Industry
Authors: Ozalp Nesrin
Published: June 2009

This paper gives a representative energy process-step model of hydrogen production in the U.S. Chemical Industry based on federal data. There have been prior efforts to create energy process-step models for other industries. However, among all manufacturing industries, creating energy flow models for the U.S. Chemical Industry is the most challenging one due to the complexity of this industry. This paper gives concise comparison of earlier studies and provides thorough description of the methodology to develop energy process-step model for hydrogen production in the U.S. Chemical Industry. Results of the energy process-step model of hydrogen production in the U.S. Chemical Industry show that steam allocations among the end-uses are: 68% to process cooling (steam injection to product combustion gases), 25% to process heating, and 7% to other process use (CO2 converter). The model also shows that the major energy consuming step in hydrogen production is the reformer, which consumes approximately 16 PJ fuel. During the course of this study, the most recent U.S. federal energy database available was for the year 1998. Currently, the most recent available U.S. federal energy database is given for the year 2002 based on the data collected from 15,500 establishments.
Performance of a Small Network of Grid Interactive, Residential Solar Photovoltaic Systems
Authors: Prusa Joseph M. , Morris John D. , Morris John D.
Published: June 2009

The performance of a network of five recently installed, grid interactive residential solar photovoltaic (PV) systems in Palm Beach County, FL is analyzed, and a probabilistic model for estimating the performance the network is developed. To first order, integrated network performance — whatever the combination of individual PV arrays — can be estimated using generalized tilt factors. These take into account basic geometrical information such as array size/orientation and solar position; as well as atmospheric effects, and module efficiencies. They are computed using a model termed the solar simulator that integrates the instantaneous solar irradiation striking a given PV system over a day. The resulting estimates for mean network performance are within ∼ 6% of the observed values. At present, work on estimators of higher moments of the energy production distribution is incomplete, but local meteorological factors that may influence their values as well as data (Pearson correlations and distribution skewness) useful for future developments are discussed.
Performance of a Constrained Microscale Film Bubble Absorber Under System Operating Conditions
Authors: Cardenas Ruander , Jenks Jeromy , Jo Myeong Chan , Narayanan Vinod
Published: June 2009

Absorption of ammonia vapor bubbles into a constrained thin film of ammonia-water solution is presented in the context of potential reduction in size of a heat-actuated heat pump component. A large-aspect-ratio channel with a depth of 600 μm restricts the thickness of the weak solution film, while ammonia vapor bubbles are injected from a porous wall. Experiments are performed at a nominal system pressure of 6.2 bar absolute and at an inlet weak solution temperature of 75 °C. A counter flowing coolant at a fixed inlet temperature of 58 °C removes the generated heat of absorption. The mass flow rate of the weak solution, vapor flow rate, and mass flow rate of the coolant solution are varied. Results indicate that a desirable operating condition for the absorber considering both heat and mass transfer attributes is obtained for a flow rate of 1.5 g/min of vapor and 35 g/min of weak solution. Variation of the coolant flow rate does not significantly affect the overall heat transfer coefficient at a low vapor flow rate of 1 g/min. Under these operating conditions, preliminary geometric scaling estimates indicate that a 11.3 kW heat load absorber would require a heat exchange surface area of 0.88 m2. The excess pressure drop penalty on the vapor side across the porous plate for this absorber needs to be considered in terms of the overall absorption cycle performance.
Combined Solar Heating and Cooling Systems: Simulation and Design Optimization
Authors: Nurzia Giovanni , Franchini Giuseppe , Perdichizzi Antonio
Published: June 2009

The deployment of solar driven air conditioning is a feasible target in all countries where high solar irradiation matches high cooling loads in buildings: the goal is to gradually replace compression chillers and reduce peak electricity demand during summer. Moreover, as solar thermal collectors are installed, solar cooling systems can be profitably employed during winter. In the present work a code has been implemented for the simulation and the design optimization of combined solar heating and cooling systems. The following system layout has been considered: in warm months the cooling demand is satisfied by means of an absorption chiller — driven by a solar collector field — and a reversible heat pump operating in series. A hot storage matches the variability of solar radiation, while a cold storage smoothes the non-stationarity of cooling demand. During winter, the reversible compression heat pump operates for space heating. Solar collectors are used as thermal source at the evaporator of the heat pump, increasing its coefficient of performance. The code, based on TRNSYS platform, is able to simulate the system throughout a year. Besides TRNSYS standard components a detailed model of the absorption chiller has been included, in order to accurately simulate its off-design operation. Using an optimization tool the size of each component is identified for a given space heating and cooling demand. The minimization of life cycle costs of the system has been chosen as the objective of the optimization. Results of a case study are presented and discussed for a solar heating and cooling plant in an office building. The optimization procedure has been carried out with simulations for a typical Northern Italy town (Alpine climate) and a typical Southern Italy town (Mediterranean climate).
Solar Energy Resource Assessment for Chile
Authors: Ortega Alberto , Escobar Rodrigo , Colle Sergio
Published: June 2009

The Chilean government’s energy policy and the power generation sector plans include wind, geothermal, hydro and biomass powerplants in order to introduce renewable energy systems to the country, but they do not mention solar energy to be a part of the plan. This apparent lack of interest in solar energy is partly due to the absence of a valid solar energy database, adequate for energy system planning activities. The only available solar radiation database is relatively old, with measurements taken in 89 stations from the 60’s onwards, obtained with high-uncertainty sensors such as Campbell-Stokes devices and pyranographs. Moreover, not all stations have measured incoming solar radiation for an adequate time span. Here, we compare the existing database of solar radiation in Chile with estimations made with satellite measurements, obtained from the GOES program through collaboration with the Brazilian space institution, INPE. Monthly mean solar energy maps are created from both data sources and compared, using Krigging methods for spatial interpolation. It is found that a maximum 30 percent deviation exist, with snow covers in the Andes Mountains adding additional uncertainty levels. The solar energy levels throughout the country can be considered as high, and it is thought that they are adequate for energy planning given proper diffusion and support by editing a Chilean Solar Atlas.
Biodiesel Fueled Engine Generator With Heat Recovery
Authors: Betz Fred , Damm Chris , Archer David , Goodwin Brian
Published: June 2009

Carnegie Mellon University’s departments of Architecture and Mechanical Engineering have teamed with Milwaukee School of Engineering’s Mechanical Engineering department to design and install a biodiesel fueled engine-generator with heat recovery equipment to supply electric and thermal power to an office building on campus, the Intelligent Workplace (IW). The installation was completed in early September 2007, and is currently being commissioned. Full scale testing will begin in early 2008. The turbocharged diesel engine-generator set is operated in parallel with the local electric utility and the campus steam grid. The system is capable of generating 25 kW of electric power while providing 18 kW of thermal power in the form of steam from an exhaust gas boiler. The steam is delivered to a double-effect Li-Br absorption chiller, which supplies chilled water to the IW for space cooling in the summer or hot water for space heating in the winter. Furthermore, the steam can be delivered to the campus steam grid during the fall and spring when neither heating nor cooling is required in the IW. Additionally, thermal energy will be recovered from the coolant to provide hot water for space heating in the winter, and for regenerating a solid desiccant dehumidification ventilation system in summer. All relevant temperatures, pressures, and flows for these systems are monitored via a building automation system. Pressure versus time measurements can be recorded in each cylinder of the engine. Emissions of nitric oxide (NO), nitrous oxide (NO2), Particulate Matter (PM), and carbon dioxide (CO2) are also monitored. Upon completion of this installation and the system performance testing, the operation of the engine generator with its heat recovery components will be integrated with the other HVAC components of the IW including a parabolic trough solar thermal driven LiBr absorption chiller, a solid desiccant dehumidification ventilation system, and multiple types of fan coils and radiant heating and cooling devices. This energy supply system is expected to reduce the IW’s primary energy consumption by half in addition to the 75% energy savings already realized as compared to the average US office space.
Evaluation of Solar Electric Power Technologies in Jordan Using Fuzzy Logic
Authors: Badran Omar , Abdulhadi Emad , Mamlook Rustom
Published: June 2009

Jordan is considered one of the sun-belt countries, which possesses high solar radiation on its horizontal surface. The present study will be concerned on the uses of fuzzy sets methodology to perform evaluation between the most suitable solar technologies for power generation in Jordan, namely, solar ponds and photovoltaic (PV) technologies. The criterion of the evaluation were based on different parameters, i.e., power capacity, efficiency, availability, capacity factor, storage capability, cost, maturity, land usage and safety, they are planned as the technologies for the near foreseen term. Based on benefit to cost ratios, the results showed that photovoltaic technology found to be the better choice in terms of generating electricity, research and development and more effective programs of support and installation.
Performance Value Index of the Solar Air-Conditioning System-PVI
Authors: Gao Yuefen , Zhang Xutao , Shi Guohua
Published: June 2009

Presently, the performance of the air-conditioner or the air-conditioning system is usually valued based on some performance indices. However, it is deficient to evaluate the performance of the air-conditioning system which uses the new energy or renewable energy only based on the indices mentioned above. According to the defects and based on the works of the solar application, a new index defined PVI is put forward to evaluate the performance of the solar air-conditioning system rationally, which is significant to the new energy or renewable energy application.
Water Intensity of Transportation Fuels: Water Projections for Fuel Adoption Rates of Light Duty Vehicles
Authors: King Carey W. , Webber Michael E. , Duncan Ian J.
Published: June 2009

Worldwide demand for petroleum grows steadily every year due to increasing demand in the United States as well as countries with fast-growing economies such as China and India, where the populations are striving to attain higher standards of living and lifestyle. Concern over this increased demand for petroleum in light of worries about reliable supply and global climate change has resulted in the US government passing new Corporate Average Fuel Economy (CAFE) standards and a Renewable Fuels Standard (RFS). The existing mandate in the US to blend ethanol into gasoline (approximately 15 billion gallons annually by 2015) had effectively committed 860 billion gallons of irrigation water in 2005 (approximately 2.4% of U.S. 2005 freshwater consumption) for producing fuel for the light duty vehicle (LDV) transportation sector. It is estimated that by 2030, nearly 2,700 billion gallons of water per year will be consumed and 4,700–6,400 billion gallons withdrawn to produce fuels used in LDVs. Irrigation for biofuels dominates the projected water usage for fuels production, but other alternatives to petroleum gasoline (coal to liquids, oil shale, and electricity via plug-in hybrid vehicles) will also contribute appreciably to future water consumption and withdrawal, especially on a regional level.
An Assessment and Comparison of Installed Solar and Wind Capacity in Texas
Authors: Keys Erin , Webber Michael E.
Published: June 2009

This paper presents the first-ever comprehensive assessment of the installed solar capacity in Texas. While the power generated from grid-tied solar photovoltaic installations can be tracked, an inventory including the capacity of these and other types of solar installations has never been performed. In contrast, installed wind capacity in Texas is closely tracked and widely publicized. Because of this discrepancy, decision-makers have lacked critical information to gauge the appropriateness of solar versus wind power for future installations, complicating their ability to prioritize which renewable power sources to incentivize. The work presented in this paper fills this knowledge gap by providing the methodology and results from a bottoms-up survey of major solar installers, large solar customers, and relevant government agencies (for example government agencies that are responsible for issuing rebates, or those that are major solar customers themselves). Over thirty entities were systematically contacted to obtain proprietary data that were then aggregated to determine the total installed solar capacity in Texas. Both power generation and heating applications are considered, including the following: photovoltaic (on- and off-grid), concentrating solar power (CSP), solar pond, and solar water heating (SWH). Other heating forms such as room and pool heating are not considered. An aggregate figure is presented and then benchmarked against installed wind capacity. Findings reveal that after 30 years and roughly $56 million in installation costs (at approximately $8300/kW), Texas possesses about 6.7 megawatts (MW) of installed solar electric capacity. Comparatively, in over 6 years and an estimated $6.9 billion in installation costs (at approximately $1600/kW), installed wind capacity in Texas approaches 5000 MW, which is more than any other state in the United States. Notably, at least another 8000 MW of new wind projects are in various stages of development, whereas few significant solar projects have been announced. This solar assessment exposes a stark difference in pace, cost and total size of installation for these two power sources, which is the likely experience for many other states. While these differences do not negate solar as a future power option, they raise further questions about the technical, social, and economic barriers each renewable technology faces, as well as the feasibility and design of incentives to further market penetration. Understanding this mixed history for these two power sources offers instructive guidance and useful insights to policymakers nationwide.
Reactivity of Iron-Containing YSZ for a Two-Step Thermochemical Water Splitting Using Thermal Reduction Temperatures of 1400–1500°C
Authors: Kodama Tatsuya , Hiraiwa Eiji , Gokon Nobuyuki
Published: June 2009

A thermochemical two-step water splitting cycle using a redox system of iron-based oxides or ferrites is one of the promising processes for converting solar energy into clean hydrogen in sunbelt regions. Fe3O4 supported on YSZ (Yttrium-Stabilized Zirconia) or Fe3O4/YSZ is a promising working material for the two-step water splitting cycle. In the water splitting cycle, an iron-containing YSZ or Fe2+-YSZ is formed by a high-temperature reaction between Fe3O4 and YSZ support at 1400°C in an inert atmosphere. The Fe2+-YSZ reacts with steam and generate hydrogen at 1000°C, to form Fe3+-YSZ that is re-activated by a thermal reduction in a separate step at 1400°C under an inert atmosphere. In the present work, the thermal reduction was performed in a higher temperature range of 1400–1500°C while the hydrolysis reaction was carried out at 1000°C. It was confirmed by XRD analysis that the cyclic redox reactions occurred based on the same reaction mechanism when using a thermal reduction temperature between 1400 and 1500°C. The conversions of Fe3O4 to Fe2+-YSZ were 20, 26 and 47% when the thermal reduction temperature were 1400, 1450, and 1500°C respectively, indicating that the x values in the formed Fe2+-YSZ or Fex2+YyZr1−yO2−y/2+x were 0.08, 0.11, and 0.19 respectively, where y = 0.15. The conversions of Fe2+-YSZ to Fe3+-YSZ in the hydrolysis reaction (at 1000°C), however, decreased from 90% to 60% when the thermal reduction temperature increased from 1400 to 1500°C. As the results, the hydrogen production reactivity of Fe3O4 supported on YSZ increased from 5.6 × 10−4 to 7.5 × 10−4 g per gram of Fe3O4/YSZ for one cycle on the cycle average by elevated thermal reduction temperature from 1400 to 1500°C.
Optimal Minimum Airflow for Air Circulation of Single-Duct VAV Terminal Boxes
Authors: Cho Young-Hum , Liu Mingsheng
Published: June 2009

Thermal comfort in an area is directly controlled by terminal boxes in variable air volume (VAV) air-handling unit (AHU) systems. The terminal box either modulates airflow or adjusts the discharge air temperature. Reduced air circulation will cause thermal discomfort in a conditioned space if the airflow and discharge air temperature are not suitable. The objective of this study is to identify an optimal value for airflow and discharge air temperature that will maintain room thermal comfort. Optimal room airflow and discharge air temperature is analyzed, and the impact of room airflow and discharge air temperature on thermal stratification is verified through CFD (Computational Fluid Dynamics) simulations.
Optimal Terminal Box Control Algorithms for Single Duct Air Handling Units
Authors: Cho Young-Hum , Liu Mingsheng
Published: June 2009

Terminal boxes are one of the major building HVAC components and directly impact building room comfort and energy costs. Current terminal boxes may cause occupant discomfort and waste energy if they have inappropriate operation control functions. The objective of this study is to develop and implement applicable optimal terminal box control algorithms. The thermal conditions and energy consumption are compared between conventional and improved control algorithms using measured data. The results of this study show that optimal terminal box control algorithms can stably maintain the set room air temperature and reduce energy consumption compared to conventional control algorithms.
Kinetics of CO2 Reforming of Methane by Catalytically Activated Metallic Foam Absorber for Solar Receiver-Reactors
Authors: Gokon Nobuyuki , Osawa Yusuke , Nakazawa Daisuke , Hatamachi Tsuyoshi , Kodama Tatsuya
Published: June 2009

Ni-Cr-Al alloy foam absorber with high porosity was catalytically activated using a Ru/γ-Al2O3 catalyst, and was subsequently tested with respect to CO2 reforming of methane in a small-scale volumetric receiver-reactor by using a sun simulator. A chemical storage efficiency of about 40% was obtained for a mean light flux of 325 kWm−2. Furthermore, the activity and the stability of the metallic foam absorber were compared with those of a SiC foam absorber activated with the same Ru/γ-Al2O3 catalyst for 50 h of light irradiation, and it was found that the metallic foam absorber has superior catalytic stability in comparison to the SiC form absorber. In addition, unlike ceramic foams such as SiC, metallic foams feature superior plasticity, which prevents the emergence of cracks caused by mechanical or thermal shock. The kinetics of CO2 reforming of methane over metallic foam absorbers were also examined for temperatures of 600–750°C using a quartz tube reactor and an electric furnace. The experiments were performed by varying the methane/CO2 ratios of 0.5–2.3. Moreover, the kinetic data were fitted to four different types of kinetic models, namely the Langmuir-Hinshelwood, Basic, Eley-Rideal, and Stepwise mechanisms. The kinetic model which provided the best prediction of the experimental reforming rates was the Langmuir-Hinshelwood mechanism.
Reactive Pellets for Improved Solar Hydrogen Production Based on Sodium Manganese Ferrite Thermochemical Cycle
Authors: Alvani Carlo , Bellusci Mariangela , La Barbera Aurelio , Padella Franco , Pentimalli Marzia , Seralessandri Luca , Varsano Francesca
Published: June 2009

Hydrogen production by water-splitting thermochemical cycle based on manganese ferrite /sodium carbonate reactive system is reported. Two different preparation procedures for manganese ferrite/sodium carbonate mixture were adopted and compared in terms of materials capability to cyclical hydrogen production. According to the first procedure conventionally synthesized manganese ferrite, i. e. high temperature (1250 °C) heating in Ar of carbonate/oxide precursors, was mixed with sodium carbonate. The blend was tested inside a TPD reactor using a cyclical hydrogen production/material regeneration scheme. After few cycles the mixture resulted rapidly passivated and unable to further produce hydrogen. An innovative method that avoids the high temperature synthesis of manganese ferrite is presented. This procedure consists in a set of consecutive thermal treatments of a manganese carbonate/sodium carbonate/iron oxide mixture in different environments (inert, oxidative, reducing) at temperatures not exceeding 750 °C. Such material, whose observed chemical composition consists in manganese ferrite and sodium carbonate in stoichiometric amount, is able to evolve hydrogen during 25 consecutive water-splitting cycles, with a small decrease in cyclical production efficiency.