bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on Sulfur Trioxide Decomposition in a Volumetric Solar Receiver-Reactor
Authors: Noglik Adam , Roeb Martin , Sattler Christian , Pitz-Paal Robert
Published: June 2009

Process conditions for the direct solar decomposition of sulfur trioxide have been investigated and optimised by using a receiver-reactor in a solar furnace. This decomposition reaction is a key step to couple concentrated solar radiation or solar high temperature heat into promising sulfur based thermochemical cycles for solar production of hydrogen from water. After proof-of-principle a modified design of the reactor was applied. A separated chamber for the evaporation of the sulfuric acid, which is the precursor of sulfur trioxide in the mentioned thermochemical cycles, a higher mass flow of reactants, an independent control and optimisation of the decomposition reactor were possible. Higher mass flows of the reactants improve the reactor efficiency because energy losses are almost independent of the mass flow due to the predominant contribution of re-radiation losses. The influence of absorber temperature, mass flow, reactant initial concentration, acid concentration, and residence time on sulfur trioxide conversion and reactor efficiency have been investigated systematically. The experimental investigations was accompanied by energy balancing of the reactor for typical operational points. The absorber temperature turned out to be most important parameter with respect to both conversion and efficiency. When the reactor was applied for solar sulfur trioxide decomposition only, reactor efficiencies of up to 40% were achieved at average absorber temperature well below 1000 °C. High conversions almost up to the maximum achievable conversion determined by thermodynamic equilibrium were achieved. As the reradiation of the absorber is the main contribution to energy losses of the reactor a cavity design is predicted to be the preferable way to further raise the efficiency.
Molten Nitrate Salt Development for Thermal Energy Storage in Parabolic Trough Solar Power Systems
Authors: Bradshaw Robert W. , Siegel Nathan P.
Published: June 2009

Thermal energy storage can enhance the utility of parabolic trough solar power plants by providing the ability to match electrical output to peak demand periods. An important component of thermal energy storage system optimization is selecting the working fluid used as the storage media and/or heat transfer fluid. Large quantities of the working fluid are required for power plants at the scale of 100-MW, so maximizing heat transfer fluid performance while minimizing material cost is important. This paper reports recent developments of multi-component molten salt formulations consisting of common alkali nitrate and alkaline earth nitrate salts that have advantageous properties for applications as heat transfer fluids in parabolic trough systems. A primary disadvantage of molten salt heat transfer fluids is relatively high freeze-onset temperature compared to organic heat transfer oil. Experimental results are reported for formulations of inorganic molten salt mixtures that display freeze-onset temperatures below 100°C. In addition to phase-change behavior, several properties of these molten salts that significantly affect their suitability as thermal energy storage fluids were evaluated, including chemical stability and viscosity. These alternative molten salts have demonstrated chemical stability in the presence of air up to approximately 500°C in laboratory testing and display chemical equilibrium behavior similar to Solar Salt. The capability to operate at temperatures up to 500°C may allow an increase in maximum temperature operating capability vs. organic fluids in existing trough systems and will enable increased power cycle efficiency. Experimental measurements of viscosity were performed from near the freeze-onset temperature to about 200°C. Viscosities can exceed 100 cP at the lowest temperature but are less than 10 cP in the primary temperature range at which the mixtures would be used in a thermal energy storage system. Quantitative cost figures of constituent salts and blends are not currently available, although, these molten salt mixtures are expected to be inexpensive compared to synthetic organic heat transfer fluids. Experiments are in progress to confirm that the corrosion behavior of readily available alloys is satisfactory for long-term use.
Heat Conduction of Inert Gas-Hydrogen Mixtures in Parabolic Trough Receivers
Authors: Burkholder Frank , Brandemuehl Michael , Kutscher Chuck , Wolfrum Ed
Published: June 2009

The annulus of a parabolic trough receiver is normally evacuated to prevent heat conduction between the internal absorber pipe and the external glass envelope. In the past, this vacuum has sometimes been compromised by hydrogen permeation from the heat transfer fluid through the absorber pipe. Heat conduction, and consequently receiver thermal loss, can be significantly increased by the presence of hydrogen in the annulus. Supplying receivers with inert gases in the annulus, or injecting receivers with inert gases after the vacuum has been compromised, could mitigate these heat losses. This study measures parabolic trough receiver heat conduction in the transition, temperature jump, and continuum regimes for argon-hydrogen and xenon-hydrogen mixtures at an absorber temperature of 350°C. Test results show that small heat loss increases over evacuated values are associated with the 95% inert gas/5% hydrogen mixtures and that from a performance perspective gas-filled HCEs would likely induce a 1–3% plant revenue decrease relative to evacuated receivers, but would protect against hydrogen-induced heat loss as long as there was sufficient quantity of inert gas in the annulus. Sherman’s interpolation formula predicted the inert gas and 95% inert gas/5% hydrogen mixture test results within experimental and model uncertainty, but did not accurately capture the larger hydrogen molar fraction test results. The source of this discrepancy will be further investigated.
Lifetime Exergy Consumption as a Sustainability Metric for Enterprise Servers
Authors: Hannemann Christopher R. , Carey Van P. , Shah Amip J. , Patel Chandrakant
Published: June 2009

As the use of information technology becomes more ubiquitous, the need for data processing and storage capabilities increases. This results in the construction and operation of large data centers—facilities that house thousands of servers and serve as the backbone for all types of computational processes. Unfortunately, as processing power and storage capacity increases, so does the corresponding power and cooling requirements of the data centers. Several studies have examined the efficiency of data centers by focusing on server and cooling power inputs, but this fails to capture the data center’s entire impact. To accomplish this, the use of a lifetime exergy (available energy) analysis is proposed. This study first details the development of a lifetime exergy consumption model designed specifically for data center analysis. To create a database of computer components, a disassembly analysis was performed, and the results are detailed. By combining the disassembly analysis of a server with the aggregation of energy and material data, a more rigorous and useful assessment of the server’s overall impact is demonstrated. The operation of the lifetime exergy consumption model is demonstrated by case studies examining the effects of variance in transportation and cooling strategies. The importance of transportation modes and material mass, which are greatly affected by supply chain parameters, is shown. The impact of static and dynamic cooling within data centers is also demonstrated.
Immobilization of Calcium Oxide Absorbent on a Fibrous Alumina Mat for High Temperature Carbon Dioixde Capture
Authors: Lee Man Su , Goswami D. Yogi , Kothurkar Nikhil , Stefanakos Elias K.
Published: June 2009

Anthropogenic carbon dioxide emission from its sources must be reduced to decrease the threat of global warming. Calcium oxide is considered as an effective carbon dioxide absorbent in biomass or coal gasification process as well as conventional power plants. It reacts with carbon dioxide to form calcium carbonate which can be decomposed into the original oxide and carbon dioxide at high temperature by calcination. In order to make this method practical for the carbon dioxide capture and sequestration, the performance of the calcium oxide absorbent must be maintained over a large number of carbonation/calcination cycles. For this reason, loss in the surface area of the absorbent due to pore plugging and sintering of particles in cyclic operation must be avoided. To prevent or minimize this problem, a simple and effective procedure for immobilization of calcium oxide on a fibrous alumina mat was developed in this study. The prepared samples were observed by SEM and the cyclic performance of the calcium oxide absorbent was evaluated by TGA experiments and compared to the previous studies in literature. 75% and 62% maximum carbonation conversions of the prepared absorbents with 23 wt % and 55 wt % calcium oxide content were achieved respectively and remained stable even after ten cycles whereas conversion in the literature data dropped steeply with the number of cycles.
Demonstrating the Use of High-Blend Ethanol (E85) in Snowmobiles
Authors: Davis Gregory W.
Published: June 2009

Kettering University has developed a cleaner and quieter snowmobile using technologies and innovative methods which can be applied to existing snowmobile designs with a minimal increase in cost. Specifically, a commercially available snowmobile using a two cylinder, four-stroke engine has been modified to run on high-blend ethanol (E-85) fuel. Further, a new exhaust system which features a catalytic converter and mufflers to minimize engine noise and exhaust emissions was developed. A number of additional improvements have been made to the track to reduce friction and diminish noise. This paper provides details of the snowmobile development to make best use of E-85, documenting the results of these efforts on performance and emissions.
Integration of the Active Desiccant Wheel in CHP System Design
Authors: Zhai Chaoqin , Archer David H. , Fischer John C.
Published: June 2009

A solid desiccant based ventilation system has been installed to provide ventilation, and cooling/heating as needed, to the Intelligent Workplace (IW) of Carnegie Mellon University, as part of the IW Energy Supply System (IWESS). Since its installation, extensive testing data have been collected and analyzed to characterize the operating performance and cost of each major component, namely the enthalpy recovery module, the active desiccant module, the heat pump module, and the overall system. It has been determined that the active desiccant wheel is expensive to operate due to the high price of natural gas in the current fuel market. In order to improve the energy efficiency and reduce the operating cost of the overall system, it has been proposed to regenerate the active desiccant wheel using the rejected heat from a bio diesel engine generator. Given the temperature and quantity of the rejected heat available, performance maps that relate the supply air temperature and humidity with various system operating variables have been constructed for the proposed integrated system, based on the predictions from an equation-based performance model of the active desiccant wheel. Using the IWESS project as a specific example, a procedure has been outlined for developing operating strategies for the active desiccant wheel integrated Combined Heating and Power (CHP) system.
Development of a Wind Tunnel Test Apparatus for Horizontal Axis Wind Turbine Rotor Testing
Authors: McWillam Michael , Johnson David
Published: June 2009

The engineering of wind turbines is not fully mature. There are still phenomena, particularly dynamic stall that cannot be accurately modeled. Dynamic stall contributes to fatigue stress and premature failure in many turbine components. The three dimensionality of dynamic stall make these structures unique for wind turbines. Currently flow visualization of dynamic stall on a wind turbine rotor has not been achieved, but these visualizations can reveal a great deal about the structures that contribute to dynamic stall. Particle Image Velocimetry (PIV) is a powerful experimental technique that can take non-intrusive flow measurements of planar flow simultaneously. High-speed cameras enable time resolved PIV can reveal the transient development. This technique is suited to gain a better understanding of dynamic stall. A custom 3.27 m diameter wind turbine has been built to allow such measurements on the blade. The camera is mounted on the hub and will take measurements within the rotating domain. Mirrors are used so that laser illumination rotates with the blade. The wind turbine will operate in controlled conditions provided by a large wind tunnel. High-speed pressure data acquisition will be used in conjunction with PIV to get an understanding of the forces associated with the flow structures. Many experiments will be made possible by this apparatus. First the flow structures responsible for the forces can be identified. Quantitative measurements of the flow field will identify the development of the stall vortex. The quantified flow structures can be used to verify and improve models. The spatial resolution of PIV can map the three dimensional structure in great detail. The experimental apparatus is independent of the blade geometry; as such multiple blades can be used to identify the effect of blade geometry. Finally flow control research in the field of aviation can be applied to control dynamic stall. These experiments will be subject of much of the future work at the University of Waterloo. Potentially this work will unlock the secrets of dynamic stall and improve the integrity of wind turbines.
CSULA Campus Energy Assessment Project
Authors: Chude Ricson , Gil Hugo , Jarrous Daniel , Hernandez Jaime , Choi Brian , Reyes Ryan , Upadhyay Sonu
Published: June 2009

As concerns over the rapid depletion of our natural resources, air quality, and the environment continue to grow, so do the technologies being developed to address those issues. Thus it’s essential that government agencies and educational institutions alike become leaders in the promotion of “green” technologies and “green” design as they are becoming more than ever before concrete solutions to our environmental concerns. This report describes the project undertaken by a multi-disciplinary group of Engineering and Technology students at California State University, Los Angeles. This project looked into a sustainable approach to reduce the overall campus energy use and its environmental impact. Over the course of the project, a detailed investigation of the campus energy demand was conducted and solutions to improve the aging campus energy infrastructure were drafted. Some of thee short term solutions included Energy Conservation Measures (ECM) that focused on the operation and management of our energy with respect to lighting, air conditioning, and building envelope. Some mid-range solutions included the increase in capacity of the TES and an overall design of a hydrogen generation station was developed for future consideration.
Experiment Based Performance Analysis of a Solar Absorption Cooling and Heating System in Carnegie Mellon University
Authors: Qu Ming , Archer David H. , Yin Hongxi
Published: June 2009

The center for building performance and diagnostic (CBPD) at Carnegie Mellon University has successfully designed, installed and tested a solar cooling and heating system to assess the feasibility of solar cooling for small scale commercial buildings or residential buildings with aspects of technology and energy efficiency. This solar cooling and heating system is primarily comprised of parabolic trough solar collectors, PTSC’s and a 16 kW dual energy source double effect (2E) absorption chiller. The 2E absorption chiller driven by PTSCs was tested to produce chilled water or hot water throughout a number of clear days in summer and winter. The analyses of the experimental data defined the system performance: the efficiency of the solar collector, the capacity and COP of the chiller, and the heat transfer coefficient of the heat recovery exchanger, by using a statistical approach, based on the energy balance equation. In the solar cooling tests during July 2007 in Pittsburgh, PA, the average efficiency of PTSCs was 35% when they were operated at about 155°C for driving the 2E absorption chiller and the chiller was able to provide 8 to 14 kW cooling with COP in the range 1.0 to 1.2; the overall system efficiency is in the range 0.35 to 0.41. In the near future, this solar absorption cooling and heating test system and its operation will be integrated with the cooling, heating and ventilation units for long term utilization.
The Spark Spread as a Measure of Economic Viability for a Combined Heating and Power Application With Ideal Loading Conditions
Authors: Graves Rhett D. , Hodge B. K. , Chamra Louay M.
Published: June 2009

“Spark spread” refers to the difference between the cost of electricity and the cost of fuel on a per-MMBTU basis. This metric is often considered when recommending equipment retrofits that require fuel switching. A spark spread of at least $12 per MMBTU is considered the threshold for economic viability of Combined Heat and Power (CHP) systems. However, this study shows that an increase in the electric utility rate has an impact on the spark spread required to maintain the economic viability of a CHP project. This challenges the paradigm that a single value for spark spread can be used as a “rule of thumb” for determining the economic viability of CHP projects. As utility rates increase, so does the importance of understanding the relationship between spark spread and the economic viability of projects.
Economic Analysis of a Nuclear Reactor Powered High-Temperature Electrolysis Hydrogen Production Plant
Authors: Harvego E. A. , McKellar M. G. , Sohal M. S. , O’Brien J. E. , Herring J. S.
Published: June 2009

A reference design for a commercial-scale high-temperature electrolysis (HTE) plant for hydrogen production was developed to provide a basis for comparing the HTE concept with other hydrogen production concepts. The reference plant design is driven by a high-temperature helium-cooled nuclear reactor coupled to a direct Brayton power cycle. The reference design reactor power is 600 MWt, with a primary system pressure of 7.0 MPa, and reactor inlet and outlet fluid temperatures of 540°C and 900°C, respectively. The electrolysis unit used to produce hydrogen includes 4,009,177 cells with a per-cell active area of 225 cm2. The optimized design for the reference hydrogen production plant operates at a system pressure of 5.0 MPa, and utilizes an air-sweep system to remove the excess oxygen that is evolved on the anode (oxygen) side of the electrolyzer. The inlet air for the air-sweep system is compressed to the system operating pressure of 5.0 MPa in a four-stage compressor with intercooling. The alternating-current (AC) to direct-current (DC) conversion efficiency is 96%. The overall system thermal-to-hydrogen production efficiency (based on the lower heating value of the produced hydrogen) is 47.1% at a hydrogen production rate of 2.356 kg/s. An economic analysis of this plant was performed using the standardized H2A Analysis Methodology developed by the Department of Energy (DOE) Hydrogen Program, and using realistic financial and cost estimating assumptions. The results of the economic analysis demonstrated that the HTE hydrogen production plant driven by a high-temperature helium-cooled nuclear power plant can deliver hydrogen at a competitive cost. A cost of $3.23/kg of hydrogen was calculated assuming an internal rate of return of 10%.
The Heat Transfer Characteristics of a 16 kW Steam Driven Double Effect Absorption Chiller
Authors: Yin Hongxi , Archer David H. , Qu Ming
Published: June 2009

A 16 kW (4.6 refrigerant tons) steam driven, double effect, parallel flow absorption chiller has been designed, manufactured, and installed in the Intelligent Workplace (IW) of Carnegie Mellon University (CMU). This chiller is driven by 6 bar saturated steam and uses a 57% LiBr-H2O sorbent. It is the smallest absorption chiller available in the existing market. The absorption chiller consists of five major and four minor heat transfer components. The manufacturer of the chiller has provided information on detailed configuration and dimensions of these components to support the calculation of their heat transfer areas, A’s, and the estimation of overall heat transfer coefficients, U’s. A steady state computational performance model for the chiller has been developed based on the applicable scientific and engineering principles. The model has been used to calculate all chiller internal working conditions and to analyze the experimental data over a wide range of operating conditions. Heat transfer coefficients inside and outside of the tubes making up the chiller’s heat transfer components have been estimated by published empirical correlations. The product of the overall heat transfer coefficient and the surface contact area, UA’s, for the 5 major heat transfer components have been estimated using the chiller model and measured performance data. Significant variations, 30%, in this parameter are observed under partial load, reduced flow conditions. Deviations between the experimental measurements and the model solutions have been analyzed to evaluate the model accuracy. At design operating conditions, the overall deviation is about 6%.
Design of a 200 kWe Solar Thermal Power Plant for Ontario
Authors: Cooper Thomas A. , Wallace James S.
Published: June 2009

A preliminary design and feasibility study has been conducted for a 200 kWe solar thermal power plant for operation in Ontario. The objective of this study is to assess the feasibility of small-scale commercial solar thermal power production in areas of relatively low insolation. The design has been developed for a convention centre site in Toronto, Ontario. The plant utilizes a portion of the large flat roof area of the convention centre to accommodate the collector array. Each power plant module provides a constant electrical output of 200 kWe throughout the year. The system is capable of maintaining the constant output during periods of low insolation, including night-time hours and cloudy periods, through a combination of thermal storage and a supplemental natural gas heat source. The powerplant utilized the organic Ranking cycle (ORC) to allow for relatively low source temperatures from the solar collector array. A computer simulation model was developed to determine the performance of the system year-round using the utilizability-solar fraction method. The ORC powerplant uses R245fa as the working fluid and operates at an overall efficiency of 11.1%. The collector is a non-concentrating evacuated tube type and operates at a temperature of 90°C with an average annual efficiency of 23.9%. The system is capable of achieving annual solar fractions of 0.686 to 0.874 with collector array areas ranging from 30 000 to 40 000 m2 and storage tank sizes ranging from 3.8 to 10 × 106L respectively. The lowest possible cost of producing electricity from the system is $0.393 CAD/kWh. The results of the study suggest that small-scale solar thermal plants are physically viable for year round operation in Ontario. The proposed system may be economically feasible given Ontario’s fixed purchase price of $0.42 CAD/kWh, but the cost of producing electricity from the system is highly dependent on the price of the solar collector.
Application of an Exhaust Heat Recovery System for Domestic Hot Water
Authors: Liu Lanbin , Fu Lin , Jiang Yi
Published: June 2009

Typically there is a great deal of waste heat available in drainage system of large-scale public bathhouses, such as public bathhouses in schools, barracks and natatoriums. The paper advances a heat pump system used in bathhouses for exhaust heat recovery. The system consists of solar energy collection system, drainage collection system and heat pump system for exhaust heat recovery. In the system, tap water is heated by energy from solar energy collection system, and is used as hot water for bathing at the beginning. At the same time, drainage collection system collects sewage from bathhouses, and then electric heat pump starts up and recovers the exhaust heat in sewage and heats the tap water. In this way, heat is recycled. Practical operation of the system was introduced, and drainage temperature as well as equipment capacity was optimized based on a practical example. Compared with gas-fired (oil-fired, coal-fired, electric) boilers, the system has advantages of lower energy consumption, less pollution and lower operating cost. Therefore, the system has great superiority in energy conservation and has a good application prospect.
Reducing Emissions and Improving Energy Efficiency in the Upstream Oil and Gas Industry
Authors: Underbakke Harald , Gytri Inge Brigt , Jakobsen Jon , Hove Stig
Published: June 2009

Energy efficiency and emission control has traditionally been a priority area in refining and petrochemical industries. In the last 15–20 years these issues has increasingly been focused in the upstream oil and gas industry. Emission taxes and commitment from the industry has led to significant improvements. Energy consumption and emission to air, especially CO2 and NOx has been reduced by typically between 10 to 30% by relatively simple and cost-effective methods. In parallel, change in design practise for new plants has contributed to similar reductions. This paper outlines the analysis and methods used and the results achieved.
Effect of Biodiesel-Ethanol Blended Fuel Spray Characteristics on the Reduction of Exhaust Emissions in a Common-Rail Diesel Engine
Authors: Yoon Seung Hyun , Park Su Han , Suh Hyun Kyu , Lee Chang Sik
Published: June 2009

An experiment was performed to analyze the effects of biodiesel-ethanol blended fuel spray on the combustion and exhaust emission characteristics of a single-cylinder common-rail diesel engine. To analyze the macroscopic and microscopic characteristics of biodiesel blended fuel spray, measurements of the injection rate, droplet diameter, and spray tip penetration were taken using an injection rate meter, spray visualization and a droplet measuring system. The combustion, exhaust emission characteristics and size distributions of particulate matter were determined for various engine operating conditions using biodiesel-ethanol blends, and the results were compared to those of conventional diesel fuel. In this investigation, the measured results of biodiesel-ethanol blended fuels show that the Sauter mean diameter (SMD) decreased with an increase of relative velocity between the injected fuel and ambient gas. Comparing the combustion characteristics of diesel fuel and biodiesel-ethanol blended fuels, both diesel and blended fuel showed similar trends in combustion pressure and the rate of heat release. However, the combustion of biodiesel-ethanol blends had lower combustion characteristics such as combustion pressures and heat release rates than those of diesel fuel because of their lower heating values. In the case of exhaust gas recirculation (EGR), the indicated specific NOx (ISNOx), and soot concentrations were lower than those of conventional diesel fuel.
Computation of Air Flow in CMU’s Intelligent Workplace and Its Effect on Occupant Health and Comfort
Authors: Li Rong , Zhang Yongjie , Archer David
Published: June 2009

In this paper, computational fluid dynamics (CFD) is utilized to investigate thermal comfort and energy efficiency of an office in the Intelligent Workplace (IW) of Carnegie Mellon University. First, a comprehensive geometric grid model is constructed to represent the office including the walls, floor, roof, windows, doors, fan coil units, and furnishings. Then the air flow and accompanying heat exchange with the bounding surfaces of the office are calculated based on indoor and outdoor ambient conditions, the operating conditions of the fan coil units and windows, and the occupancy of the space. The computational results of the air flow provide the means to measure whether comfort conditions have been established based on the outside conditions and on the operation of the fan coil units. The operating conditions of the fan coil units, fan speed, and chilled/heated water flow, determine their effectiveness in cooling/heating and their operating costs. This CFD air flow simulation, therefore, when generalized, provides a design support system for architects and engineers. The numerical solutions of office space are calibrated and validated by empirical operational data from the fan coil units. The design support system will enable the evaluation of the annual performance and operating cost of given fan coil units in a given building space.
A Fuels Cost Comparison of Gasoline and Electric Powered Vehicles
Authors: Ford George , Yanik Paul
Published: June 2009

Per British thermal unit (BTU), in the United States, gasoline currently costs about 7.6 times as much as coal. Due to the prevalence of coal fired electricity generating stations in the country, electrically powered vehicles may provide a fuel cost savings over similar gasoline powered vehicles. Fuel costs for electric vehicles have been reported to cost about $0.045 per mile to operate. Higher efficiency, gasoline operated automobiles such as the Toyota Corolla have reported fuel costs of about $0.093 per mile. This paper provides a first glance examination of electrically powered and gasoline powered vehicles in the United States. While gasoline costs continue to rise, a cheap, environmentally safe transportation alternative is needed to maintain the flexible lifestyle currently enjoyed by Americans. The cycle energy efficiency of coal produced electricity for personal transportation is much lower than the energy efficiency of gasoline, but the large cost differences between these two forms of fossil fuels may provide a temporary fix to a looming transportation crisis in the United States. The long-term environmental effects of an electrically powered, private transportation fleet could prove catastrophic due to increased use of coal and accompanying combustion product air pollution, but clean, renewable, electricity producing technologies may support more prolific long-term use of electrically powered transportation modes.
Analysis of Thermodynamics of Two-Step Solar Water Splitting
Authors: Roeb Martin , Gathmann Nils , Neises Martina , Sattler Christian , Pitz-Paal Robert
Published: June 2009

A two-step thermo-chemical cycle for solar production of hydrogen from water has been developed and investigated. It is based on metal oxide redox pair systems, which can split water molecules by abstracting oxygen atoms and reversibly incorporating them into their lattice. After proof-of-principle, successful experimental demonstration of several cycles of alternating hydrogen and oxygen production, and elaboration of process strategies presented in previous contributions, the present work describes a thermodynamic study aiming at the fine tuning of the redox system, at the improvement of process conditions, and at the evaluation of the potential of the process. For the redox material the oxygen uptake capability is an essential characteristic, because it is directly connected to the amount of hydrogen which can be produced. In order to evaluate the maximum oxygen uptake potential of a coating material and to be able to find new redox materials theoretical considerations based on thermodynamic laws and properties are helpful and faster than actual tests. Through thermodynamic calculations it is possible to predict the theoretical maximum output of H2 from a specific redox-material under certain conditions. Calculations were focussed on the two mixed iron oxides nickel-iron oxide and zinc-iron oxide. In the simulation the amount of oxygen in the redox-material is calculated before and after the splitting step on the basis of laws of thermodynamics and available material properties for the mixed-iron oxides used. For the simulation the commercial Software FactSage and available databases for the necessary material properties were used. The analysis showed that a maximum hydrogen yield is achieved if the regeneration temperature is raised to the limits of the operation range, if the temperature for the water splitting is lowered below 800 °C and if the partial pressure of oxygen during regeneration is decreased to the lower limits of the operational range. The increased hydrogen yield at lower splitting temperature of about 800 °C could not be confirmed in experimental results, where a higher splitting temperature led to a higher hydrogen yield. As a consequence it can be stated that kinetics must play an important role especially in the splitting step.
Comparing the Eco-Footprint of On-Site CHP vs. EPGS Systems
Authors: Meckler Milton , Hyman Lucas B. , Landis Kyle A.
Published: June 2009

This paper compares the Eco-Footprint of three (3) sustainable on-site CHP system alternatives vs. a representative 30% thermally efficient conventionally designed remote electric utility/merchant power generation station (EPGS) serving a 3.5 MW gas turbine installation proposed for a central California university campus. It has been demonstrated (ASHRAE Transactions # DA-07-009) that sustainable on-site cooling-heating-power (CHP) systems for large multi-building projects employing a simplified design approach from that of a conventionally designed mini-utility-type CHP systems employing large volume/footprint, costly, high thermal mass heat-recovery steam-generators (HRSG’s), and 24/7 stationary engineers, can result in lower annual owning and operating costs. The above peer-reviewed 2007 paper illustrated the use of prefabricated, skid-mounted hybrid steam generators with internal headers, fully integrated with a low-pressure drop heat extraction coil (in lieu of a HRSG) located in the combustion gas turbine (CGT) exhaust. Subject CGT extraction coil utilized environmentally benign heat transfer fluid to redistribute extracted CGT exhaust waste to serve campus multi-building annual space cooling, heating, and domestic hot water loads with system thermal balance facilitated via maintenance of a high year-round log-mean-temperature-differential at the CGT extraction coil, also resulting in a lower CGT back-pressure, and significant life-cycle cost savings. This paper also takes an alternative look at the above referenced CHP plant designs for greater operating economies along with a third CHP alternative employing a direct CGT exhaust gas fired 2-stage absorption chiller, and then compare the Eco Footprint and life cycle cost for each of the three CHP options with the above referenced EPGS supplying comparable annual electric power requirements. Finally, using the Eco Footprint of the EPGS as a baseline, the most promising CHP alternative of the above three will also be explored as a potential “cap and trade” candidate to further reduce its first cost and therefore enhance its sustainability from both an energy with greenhouse gas emissions standpoint.
Successfully Eliminating the Barriers to Solar Photovoltaic Implementation
Authors: Goodbody Stephen A.
Published: June 2009

For the majority of commercial and industrial facilities in the United States, electrical power represents a significant portion of their total operating costs and a cost over which they have little or no control. The cost of electrical power has risen dramatically during the past three years, and is projected to continue to increase due to uncertainties in global fuel supply, production investments necessary to meet increasing demand, increased maintenance and repair costs of aging production and transmission infrastructure, the decommissioning and remediation of life-expired generating facilities, and the implementation of increasingly stringent pollution control measures. These trends and influences are seen, to a greater or lesser extent, across the entire nation, but their impact upon the northeast and mid-Atlantic states of Connecticut, Maryland, New Jersey and Delaware has been particularly significant. While solar photovoltaic systems can provide an excellent on-site power source for many commercial and industrial facilities, and would reduce the burden on the existing, over-stretched and aging national power transmission infrastructure, the high capital cost of solar photovoltaic systems represents a significant barrier to the wide-scale commercial adoption of this technology. In an attempt to overcome this barrier, individual states are implementing a variety of rebate and incentive programs designed to promote the installation and use of solar power systems. However a unifying Federal Renewable Portfolio Standard does not presently exist and the complex administration demand of state programs represents a further barrier to adoption for many companies. Further, while a Federal Investment Tax Credit is available, certain organizations for whom solar photovoltaic power would otherwise be an attractive cost-saving opportunity, notably municipalities and non-profits, are generally unable to take advantage of this benefit. In response to this unsatisfactory situation, Soltage, Inc. designs, installs, operates, maintains, and retains ownership of commercial-scale solar photovoltaic power stations at client sites, providing solar-generated power directly to the client. Our customers incur no capital, maintenance or operating costs, and have no administrative burden beyond purchasing solar-generated power at rates that are below their existing utility rate and which are stabilized and guaranteed into the future. For our clients, this is their most effective means of controlling and stabilizing energy expenses in the immediate and long terms. For our nation, this is the key to rapidly implementing the adoption and scale-up of solar photovoltaic power, with all of its inherent benefits.
Experimental and Theoretical Investigations of Performance of Multi-Stage Solar Still Water Desalination Unit Coupled With an Evacuated Tube Solar Collector
Authors: Shatat M. I. M. , Mahkamov K. , Johnson K.
Published: June 2009

At present scarcity of potable and drinking water is a pressing issue in certain parts of the Middle East region. Important advances have been made in desalination technologies but relatively high capital and running costs restrict their wide application even in cases when solar energy is used. Flat-plate solar collectors mainly have been employed in the past to distill water in compact desalination systems. Currently, it is possible to replace the above collectors by more advanced evacuated tube ones, which are available on the market at a similar price. This paper describes results of experimental and theoretical investigations of the operation of a solar still desalination system coupled with a heat pipe evacuated tube collector with the aperture area of about 1.7 m2. A multi-stage solar still water desalination system was designed to recover latent heat from evaporation and condensation processes in four stages. The variation in the solar radiation (insolation) during a typical mid-summer day in the Middle East region was simulated using an array of 110 halogen flood lights covering the area of the solar collector. The synthetic brackish lab water solution was used for experiments and its total dissolved solids (TDS), electrical conductivity and pH were measured prior to and after the distillation process. The system’s operation was numerically simulated using a mathematical model based on the system of ordinary differential equations describing mass and energy conservation in each stage of the system. The experimental and theoretical values for the total daily distillate output were found to be in good agreement. The results of tests demonstrate that the system produces about 6.5 kg of clean water per day and have the distillation efficiency equal to 76%. However, the overall efficiency of the laboratory test rig at this stage of investigations was found to be low at the level of 26% and this is due to excessive heat losses in the system. The analysis of the distilled water shows that its quality is within the World Health Organization guidelines. Further research is being performed to improve the performance of the installation.
Modelling of the Net Zero Energy Town House in Toronto Using TRNSYS, and an Analysis of the Impact Using Thermal Mass
Authors: Siddiqui Omar , Fung Alan , Tse Humphrey , Zhang Dahai
Published: June 2009

A detailed model of the Net Zero Energy Town House in Toronto is developed in TRNSYS, incorporating a ground source heat pump integrated with an in floor radiant heating system. In order to minimize the heating and cooling loads, the building envelope is well insulated with the exterior walls having an R-60 insulation value. Much of the work done previously on the use of thermal mass in buildings has been experimental in nature and has focussed mainly on conventional brick construction in hot climates such as Asia and Africa. This research will analyze the impact of using thermal mass with a building envelope that is highly insulated, and of a light construction, such as that used in Low Energy or Net Zero housing. Furthermore, this analysis would also evaluate the impact of using thermal mass in a cold climate such as that found in Canada. The simulations showed that, for colder climates, thermal mass can replace some of the insulation and still provide superior results. Also the impact of thermal mass was found to be more significant during the winter season than summer for Toronto.
Cogeneration System Performance Modeling
Authors: Marion Flore A. , Masson Sophie V. , Betz Frederik J. , Archer David H.
Published: June 2009

A bioDiesel fueled engine generator with heat recovery from the exhaust as steam and from the coolant as hot water has been installed in the Intelligent Workplace, the IW, of Carnegie Mellon’s School of Architecture. The steam and hot water are to be used for cooling, heating, and ventilation air dehumidification in the IW. This cogeneration equipment is a primary component of an energy supply system that will halve the consumption of primary energy required to operate the IW. This component was installed in September 2007, and commissioning is now underway. In parallel, a systems performance model of the engine generator, its heat recovery exchangers, a steam driven absorption chiller, a ventilation unit, fan coil cooling/heating units has been programmed making use of TRNSYS transient simulation software. This model has now been used to estimate the energy recoverable by the system operating in the IW for different characteristic periods, throughout a typical year in Pittsburgh, PA. In the initial stages of this modeling, the engine parameters have been set at its design load, 27 kW, delivering up to 17 kW of steam and 22 kW of hot water according to calculation. The steam is used in the absorption chiller during the summer and in hot water production during the winter. Hot water is used in desiccant regeneration for air dehumidification during the summer, in IW heating during the winter, and in domestic hot water product year around. Systems controls in the TRNSYS simulation direct the steam and hot water produced in the operation of the engine generator system to meet the IW’s hourly loads throughout seasons.
Measurement of Solar Radiation for Renewable Energy Systems
Authors: Padovan Andrea , Del Col Davide
Published: June 2009

In this paper the authors present a new set of solar radiation data taken at the latitude of 45.4°, in Padova, Italy. These measurements are performed within a new laboratory for the study of solar energy conversion systems. The global and the diffuse irradiance is measured on the horizontal plane and the global irradiance is also measured on sloped planes. The experimental uncertainty of the measurement of solar radiation is fully analyzed. In the design of a solar system, it is crucial to know the solar radiation on the inclined surface, but generally only data on the horizontal is available and solar radiation on the tilted plane is predicted using the information collected on the horizontal. There is need for assessment of prediction methods for estimating the solar radiation on inclined surfaces. In this paper, new data of global and diffuse radiation is compared to some most used correlations. Besides, the values calculated for the tilted plane are compared against those directly measured by a pyranometer installed on the sloped plane.
Efficiency Enhancement Using Cold Storage for Solar Powered Absorption Cooling of Data Centers
Authors: Muren Russell , Carey Van P.
Published: June 2009

Use of solar powered absorption refrigeration to augment data center afternoon cooling has three advantages: (1) it replaces non-renewable electrically powered cooling with cooling provided by renewable power, (2) it reduces operating costs by reducing consumption of costly peak load electrical power, and (3) use of a carbon free energy source reduces the carbon footprint of the data center. In the investigation summarized here, a computational model of a lithium bromide (LiBr) and water absorption system performance was used to explore the advantages of using nighttime cooling and cold storage to enhance the performance of solar powered absorption refrigeration for peak cooling in data centers. In this study, the model accounts for thermodynamic property effects on the absorption cycle performance and finite heat exchanger effectiveness. The model is used to explore the impact of parametric changes on system coefficient of performance (COP) and system payback. The results indicate that COP enhancements above 15% can be achieved with simple cold storage strategies. The results indicate that that when optimally designed, this type of system achieves energy efficiency, offering environmental and economic advantages that make it an attractive initial step in incorporating solar powered absorption cooling into green data center designs. Strategies for maximizing the positive contributions of cold storage suggested by the results are discussed.
Energy Efficient Polymers for Gas-Liquid Heat Exchangers
Authors: Luckow Patrick , Bar-Cohen Avram , Rodgers Peter , Cevallos Juan
Published: June 2009

The present study explores the thermofluid characteristics of a seawater-methane heat exchanger that could be used in the liquefaction of natural gas on offshore platforms. The compression process generates large amounts of heat, usually dissipated via plate heat exchangers using seawater as a convenient cooling fluid. Such an application mandates the use of a corrosion resistant material. Metals such as titanium, expensive in terms of both energy and currency, are a common choice. The “total coefficient of performance,” or COPT, which incorporates the energy required to manufacture a heat exchanger along with the pumping power expended over the lifetime of the heat exchanger, is used to compare conventional metallic materials to thermally conductive polymers. The results reveal that heat exchangers fabricated of low energy, low thermal conductivity polymers can perform as well as, or better than, those fabricated of conventional materials, over the full lifecycle of the heat exchanger. Analysis of a prototypical seawater-methane heat exchanger, built from a thermally conductive polymer, suggests that a COPT nearly double that of aluminum, and more than ten times that of titanium, could be achieved.