bluuebunny/crossref_metadata_2025 huggingface dataset:
Combustion of Biomass in Fluidized Beds: Problems and Some Solutions Based on Danish Experiences
Authors: Lin Weigang , Jensen Anker D. , Johnsson Jan E. , Dam-Johansen Kim
Published: January 2009

This paper summarizes the major problems in firing and co-firing the annual biomass, such as straw, in both lab-scale and full-scale fluidized bed combustors. Two types of problems were studied: operational problems, such as agglomeration, deposition and corrosion; and emission problems, e.g. emissions of NO and SO2. Measurements of deposition and corrosion rate on the heat transfer surfaces, as well as gas phase alkali metal concentrations, were performed in full scale CFB boilers (an 80 MWth and a 20 MWth plant), which have been co-firing coal with straw and other biomass. Severe corrosion and deposition were observed in the superheater located in the loop-seal of the 80 MWth boiler. The boiler load variation has impact on the operation parameters. When the fraction of biomass with a high K-content (>1 wt. %) was higher than 60% on a thermal basis, the boiler suffered from severe agglomeration problems. Lab-scale experiments were carried out for the fundamental understanding of phenomena found in full-scale boilers and for testing possible solutions to the problems. The results showed a strong tendency of agglomeration in fluidized beds during combustion of straw, which normally have a high content of potassium and chlorine. The results indicate that the operational problems may be minimized by a combination of additives, improved boiler design, split of combustion air and detection of agglomeration at an early stage.
Operational Experience and Design Consideration of a Large Scale Anthracite Fired CFB Boiler in China
Authors: Lu Xiaofeng , Wang Dajun , Chen Qinghua , Amano Ryo S.
Published: January 2009

Since the first 410t/h CFB boiler was built and put into business operation in 1996, CFB boiler has gotten a rapid development in China because of low emission and good availability for low rank coal. The CFB boiler technology has been selected to build a 300MW coal-fired boiler and to replace many pulverized coal-fired boilers with a capacity range from 220t/h to 410t/h in China. Most of these CFB boilers burn local low rank coals. To investigate the combustion characteristics of anthracite and optimize the operation of CFB boilers, a series of thermal tests were done on a 220t/h CFB boiler, in AIXI power plant, and on a 410t/h CFB boiler (the largest CFB boiler in China), in GAOBA power plant. The coal burned in these two CFB boilers came from the same coal mine. The properties of the boilers include: operating and designing parameters affected by the carbon content in the fly ash, the distribution of oxygen and temperature in the furnace, a limestone milling and transfer system, and operation under a lower load. All tests were aimed at how to optimize the operation of CFB boilers when anthracite is burned. Based on these test results, the technical requirements for a 300MW CFB boiler were investigated and are presented in this paper. The contents of the investigation included design considerations and ash utilization. An investigation on converting a pulverized coal-fired (PC) boiler to a CFB boiler is also presented in this paper. The content of the investigation includes basic design consideration of the conversion, and utilization of the milling system from an old PC boiler.
Bubbling Fluidized Bed Co-Combustion of Different Sustainable Fuels: Trace Element Behaviour
Authors: Wolski N. , Berger R. , Maier J. , Hein K. R. G.
Published: January 2009

With this paper the author will show interesting results of the co-combustion of coal in combination with bark and paper sludge in fluidized bed combustion. The results presented were collected during two measurement campaigns at a 30 kW electrically stabilized bubbling fluidized bed. The fluidized bed combustor was compared to large scale combustors in different campaigns before and thus gives an idea of the output of industrial plants. The main focus of the measurements was the behavior of trace elements of Ni Pb, Zn, Cr and Cu with a changing bed material. One bed material was pre-used under the exposure of combustion of a ternary fuel mixture of coal, bark and paper sludge over a long period of time resulting in a bed composition of 2/3 SiO2 and 1/3 Al2O3. The second bed material utilized, which was a sand (primarily SiO2) not used before thus not enriched in any compounds. When comparing the results of all trials three different trace metal partitioning effects were monitored. First an increase in the elemental concentration in the bed material which was primarily due to the higher input concentration with the pre-used bed material which was found for all three alternatives plus a decrease in filter and cyclone concentrations (Ni, Pb). Secondly an increase in all three ash fractions was detected for Cu. The third was a mixture of both with increasing filter concentrations but decreasing cyclone concentrations (Zn, Cr). An attempt was made to link the before primarily to the enrichment in Al-compounds and to a bed capacity of retention. The results presented indicate the need for longer periods of testing even at small scaled facilities if the comparison to large scale facilities is attempted.
Green Energy From Wood Based Fuels Using Foster Wheeler CFB Boilers
Authors: Hiltunen Matti A. , Vilokki Harri A. J. , Holopainen Hannu A.
Published: January 2009

Biomass fuels are one important way to meet the Kyoto requirements for the reduction of global CO2 emissions in power generation. For years, Foster Wheeler CFB-boilers have been used for combustion of waste wood and forest residues. The latest CFB-projects in Germany are utilizing demolition wood and production waste from wood-working industries. Compared to coal, wood-based fuels have some special characteristics. To ensure smooth fuel feeding, the wood fuels have to be carefully crushed and chipped. From demolition wood it is necessary to remove metals and other large uncombustible impurities. Moisture content of wood waste may vary in a wide range from 10–60%. To ensure steady heat input into the boiler using volumetric feeders, a good homogenization at fuel yard is required. Fuel ash contents are low and particle sizes are fine. Due to high potassium contents, ash melts at low temperature; hence, ashes have a tendency for fouling and slagging in boilers. Biomass fuels also contain some chlorine, which together with alkalies, induces aggressive corrosion. The demolition wood may contain additional heavy metals. Corrosion abatement is discussed and related to the novel INTREX superheater technology. In INTREX boilers, final superheater and reheater are placed in the hot solid return flow back from the cyclone to the combustion chamber, thus avoiding high temperature corrosion. This allows steam temperature after superheater in the flue gas channel to be kept below 400°C. The arrangement also prevents effective fouling of heating surfaces. The longtime experience of demolition wood-fired plants in Hornitex Beeskow, 86.3 MWt, 110 t/h, 480°C, 89 bar (startup 1996), Hornitex Horn 94 MWt, 120 t/h, 480°C, 89 bar (startup in 1999) is presented. Operational results from Ko¨hler Kehl 44 MWt, 59 t/h, 500, 90 bar (startup in 2002) are discussed. The used steam parameters allow an increase of power production efficiency from 25–30% to 33–35.5% using steam cycle without reheat and with reheat up to 36.4% (gross) in condensing operation.
An Evaluation of Hybrid Coal Combustion Technology for Repowering H.F. Lee Unit 2
Authors: Castagnero Steven J. , Weinstein Richard E. , King Thomas J. , Bonk Donald L. , Toll Edward B.
Published: January 2009

Combustion-based hybrid systems use coal as fuel, and employ combustion technologies in combination with a gas turbine in a number combined cycle configurations. One of these hybrid systems is known by its acronym: CHIPPS, for: ‘combustion-based high-performance power system.’ CHIPPS is a coal-fueled technology that is suited for repowering units that have boilers in good condition, as it continues the use of the existing furnace and steam tubes. This paper describes a conceptual evaluation to establish the feasibility of using CHIPPS technology to repower an existing coal-fired steam plant. The H.F. Lee power plant, owned by CP&L Progress Energy, is located on the Neuse River, just outside Goldsboro, North Carolina. CHIPPS would repower Unit 2, a 1950’s era non-reheat steam unit, one of the three units at this site. If CHIPPS repowering proved feasible for Unit 2, it would likely be a good choice for a wide range of other similar units throughout the U.S. CHIPPS retains the use of the existing Unit 2 furnace and steam turbine/generator, but adds a combustion turbine to increase energy efficiency in a way that makes this coal-fired plant nearly as efficient as a combined cycle power plant that would otherwise use more expensive natural gas. The CHIPPs technology concept used employs a Foster Wheeler circulating fluidized bed partial gasifier that would supply syngas to a General Electric 6B combustion turbine. Only a portion of the coal is gasified to syngas. The remaining coal energy is transferred as char to the lower of three boiler burner rows of the existing Unit 2 furnace that would be fitted with special burners for the char. The upper two rows are not changed and continue to burn coal from the existing mills. With CHIPPS: • Output is expected to increase from 78,520 kW to 139,750 kW, • 7 percent less fuel would be needed per kWh generated, • Environmental improvement would become exemplary, however, • Cost is high, about $214,606,000; Unit 2 is too small for attractive economics, and a non-reheat unit leads to only modest efficiency improvement. Future CHIPPS repowering might be better suited for a larger reheat steam plant instead of at H.F. Lee Unit 2. This paper summarizes the CHIPPS repowering power plant concept and describes: • An overview of the CHIPPS process; • A description of the existing H.F. Lee Unit 2; • An estimate of the performance improvements expected with Unit 2 repowered with CHIPPS; • An estimate of the environmental performance expectation from the unit with CHIPPS; and, • An estimate of the expected costs to upgrade the unit. Significant conclusions and suggestions for where this class of hybrid combustion technologies might best be applied.
Performance Results With ALSTOM’s Circulating Moving Bed Combuster™
Authors: Jukkola Glen , Levasseur Armand , Turek Dave , Teigen Bard , Jain Suresh , Thibeault Paul
Published: January 2009

ALSTOM is developing and testing a new and more efficient coal combustion technology, including a new type of steam generator known as a “circulating moving bed (CMBTM) combustion system combustor.” The CMBTM combustion system technology involves a novel method of solid fuel combustion and heat transfer. In this design, a heat exchanger will heat the energy cycle working fluid, steam or air, to the high temperature levels required for advanced power generation systems. This will produce a step change in both performance and capital costs relative to today’s pulverized coal and fluid bed boiler designs. In addition to high temperature Rankine cycles, the CMBTM combustion system is an enabling technology for hydrogen production and CO2 capture from combustion systems utilizing innovative chemical looping airblown gasification and syngas decarbonization. ALSTOM’s 3MWth Multi-Use Combustion Test Facility has been modified to allow operation in CMBTM combustion system mode. This paper summarizes the results of this program, which includes performance results from pilot plant testing. Participants include the U.S. DOE, ALSTOM, the University of Massachusetts, and the Massachusetts Institute of Technology. The total program cost is $2,485,468 with the DOE’s National Energy Technology Laboratory (NETL) providing 60% of the funding under Cooperative Agreement No. DE-FC26-01NT41223.
The Behavior of Free Lime in CFBC Ashes
Authors: Bulewicz E. M. , Go´ra K. , Anthony E. J.
Published: January 2009

Ash disposal and ash use are critical to FBC technology and in turn the reactions of FBC ash with water are key to both of these two issues. An effective ash reactivation technology would improve the economics for FBC firing of high-sulphur fuels. Similarly, controlled ash hydration before disposal is the standard method for conditioning FBC ashes when firing high-sulphur fuels with limestone addition. Ashes can be hydrated with liquid water or by steam under pressure and our earlier work suggested that when FBC ashes were hydrated by either method, the components derived from the coal and those from the sorbent can interact chemically. As a result, the amount of “free CaO” (defined as the proportion of CaO and Ca(OH)2, expressed as CaO) may change. Usually, “free CaO” increases after hydration, particularly under pressure. However, there is also evidence that some of the CaO, derived from excess limestone sorbent, enters into reaction with the ash components, possibly silica or silicates. Such processes must modify the exothermicity of the ashes with water and affect their subsequent behaviour. This implies that it is incorrect to assume, as has often been done, that the heat of the hydration process is directly proportional to the CaO content of the ash. Furthermore, the results presented here also strongly support the view that one must include these interactions when looking at FBC hydration.
Combustion of Wood Processing Residues in a Circulating Fluidized Bed
Authors: Preto Fernando
Published: January 2009

The combustion of wood processing residues was tested in the 0.8 MWth CANMET Circulating Fluidized Bed Combustor (CFBC) pilot plant. The specific residues tested were three different types of coniferous tree bark (i.e. from different locations to represent a range of possible fuels and fuel properties). Combustion conditions may be summarized as follows: fuel moisture levels 42–60%, fluidizing velocity 2.1–2.4 m/s; bed temperature 785–910 °C; maximum freeboard temperature 980–1070 °C and excess air levels 20–75%. The CFBC unit was able to burn the high moisture level fuels with no detrimental effect. In all trials the residues burned very well, with combustion efficiency greater than 99% based on overhead carbon loss. Emissions measurements were made of the following pollutant species CO, NOx, N2O, SO2, and dioxins and furans. The emissions levels were: 100–130 ppm NOx; <1 ppm N2O; 5–20 ppm SO2 and 400–1800 ppm CO. These emission levels are well below pollution guidelines for all major pollutants except CO. This however can be traced to the non-homogeneous nature of the coarse feed in the pilot plant. The problem can reasonably be addressed in a full-scale unit by a more stable feed system. A preliminary economic analysis of a new 25 MW FBC power plant firing these fuels was performed. Conservative inputs give a cost of 6 cents/kWh for the electricity produced and a economic wood haulage radius of 70 km.
Perspectives on the Use of Molten Carbonate Fuel Cells with Renewable Energy Sources
Authors: Desideri Umberto
Published: January 2009

This paper presents the state of the art and the perspectives of the use of molten carbonate fuel cells with renewable energy sources. The molten carbonate fuel cell is the only technology that can use fuels containing carbon monoxide and carbon dioxide in the anode gas. It has been even shown in experimental tests in single cells that carbon monoxide can be considered as a fuel in this type of fuel cell. The fuels that can be used in MCFC are landfill gas, biogas from anaerobic digestion processes and syngas from gasification of biomass and waste. The commercial size of MCFC stacks (125 to 250 kW) is the right size for use with such fuels which are generally not available for power plants with output larger than some MW. All the above fuels are characterized by the presence of contaminants that need be removed before their use in the fuel cell. Among the contaminants hydrogen sulfide and chlorine compounds seem to cause the worst damage. To be used with such fuels, MCFC still need to be deeply investigated and duration tests are needed to determine the highest tolerable concentrations in the anode gases.
Fabrication of Micro-Actuated Galvanic Cells as Power on Demand for Lab on a Chip Applications by Means of Novel PCB/MEMS Technology
Authors: Cardenas-Valencia A. M. , Fries D. P. , Steimle G. , Broadbent H. , Langebrake L. C. , Benson R. F.
Published: January 2009

A novel copper-clad liquid crystal polymer material is proposed as a basic material for the construction of galvanic cells. Copper is an ideal material that allows not only the formation of conductor patterns in the material but also can be electroplated selectively with a wide variety of metals to create heterogeneous systems. The use of a novel mask-less patterning system described herein opens up the opportunity for micro fabrication of different microstructures that can be layered to form complex two and potentially three-dimensional micro fluidic networks. Achieving the photo-imprinting by the use of a novel mask-less system not only reduces the cost but also allows for ease and flexibility in making systems and is ideal for research and development environments. In this paper micro galvanic cells actuated by means of fluidic actuators have been designed and constructed. The electrochemical galvanic cells used as power source examples are a Daniell’s (Copper-Zinc) electrochemical battery, and an aluminum-air galvanic system. The choice for the electrochemical systems is discussed and some preliminary results are presented to show the levels of energy available. In addition, the basic concept of an electrically induced expansion mechanism for circuit activation on demand is described. Lastly, the mechanics of the suggested actuation mechanism are discussed.
Exergy Analysis of Polymer Electrolyte Fuel Cell Systems Using Methanol
Authors: Ishihara Akimitsu , Mitsushima Shigenori , Kamiya Nobuyuki , Ota Ken-Ichiro
Published: January 2009

An exergy (available energy) analysis has been conducted on a typical polymer electrolyte fuel cell (PEFC) system using methanol. The material balance and enthalpy balance were calculated for the PEFC system using methanol steam reforming, and the exergy flow was obtained. Based on these results, the exergy loss in each unit was obtained, and the difference between the enthalpy and exergy was discussed. The exergy loss in this system was calculated to be 178kJ/mole MeOH for the steam reforming process of methanol. Although the enthalpy efficiency approached unity as the recovery rate of the waste heat from the cell approached unity, the exergy efficiency remained around 0.45 since the cell’s operating temperature of 80°C is low. It was also found that the cell voltage should exceed 0.82V in order to obtain the exergy efficiency of 0.5 or higher. A direct methanol fuel cell (DMFC) was analyzed using the exergy and compared with the methanol reforming PEFC. In order to obtain the exergy efficiency higher than that of PEFC with steam reforming, the cell voltage of the DMFC should be 0.48V or greater at the current density of 600mA/cm2.
Thermodynamic Modeling and Performance Analysis of a Power Generation System Based on the Solid Oxide Fuel Cell
Authors: Bae Bong-Hyang , Sohn Jeong L. , Ro Sung Tack
Published: January 2009

Performance analysis with detailed thermodynamic models of a power generation system based on the solid oxide fuel cell (SOFC) is presented. The proposed power system in this study is composed of an external reformer, a SOFC with an internal reformer, an afterburner, and preheaters. Natural gas (CH4) as supplied fuel to the SOFC is reformed to hydrogen (H2) by external and internal reformers. Necessary steam for the use in reformers is either externally supplied or internally recirculated from exit of the SOFC. Exhaust gas of the SOFC containing steam and other chemical compositions is combusted in afterburner to raise its temperature to preheat supplied fuel and air. It is found from the results of performance analysis that the system performance can be enhanced by the use of internally recirculated steam from the exhaust gas of the SOFC. It is also found that the benefit of the high-pressure operation is not so secure if the power to compress supplied air is consumed from the produced power of the system. Installation of a turbine at the system exhaust produces necessary power to pressurize supplied air and, additionally, extra power to enhance total power density of the system.
Simulation of a 25 kW Steam-Methanol Fuel Processor/PEM Fuel Cell System
Authors: Wheeldon I. R. , Amphlett J. C. , Fowler M. , Hooper M. , Mann R. F. , Peppley B. A. , Thurgood C. P.
Published: January 2009

The transition to a hydrogen economy will require an intermediate energy carrier until a sufficient hydrogen infrastructure can be implemented. A likely near-term candidate is the on-board or on-site production of hydrogen from steam-methanol reforming. The low tolerance of PEM fuel cell anode electrocatalyst, to the carbon monoxide produced during reforming, necessitates a hydrogen purification or carbon monoxide clean-up sub-system. Considerable advantages can be gained from the use of a steam-methanol reformer with a palladium-silver alloy membrane, hydrogen purification unit. In the present work we have examined such a system. A simulation comprised of a Polymer Electrolyte Membrane Fuel Cell electrochemical model, a membrane permeation model and a commercially available thermodynamics calculation package was constructed. The case investigated in this work is of a 25 kW nominal DC power generating system. A maximum efficiency of 40% was achieved at reformer and membrane unit conditions of 200°C and 300 psia with 97% conversion of the inlet methanol. The effects of variation in temperature and pressure where also investigated. It was found that the reformer and membrane unit pressure had the most significant effect on overall system efficiency. The system efficiency increases with pressure reaching a maximum at the upper limit of the operating region, 300 psia.
Process Integration and Optimization of Molten Carbonate Fuel Cell System
Authors: Shihn Harmanjeet , Shah Ramesh K.
Published: January 2009

This paper presents a framework for the system integration and optimization of a molten carbonate fuel cell (MCFC) working under stationary conditions using process integration. Here, the analysis is focused on two systems in terms of the efficiency and process requirements: (i) an MCFC system alone and (ii) an MCFC system integrated with the steam turbine cycle, now onwards referred to as fuel cell combined cycle system for electric power generation. In the first system, a steady state direct internal reforming MCFC system is being simulated using desulphurized natural gas. A heat exchanger network is developed using process integration so that a minimum amount of external thermal energy is provided to the fuel cell system for electric power generation. In the second analysis, a steam turbine system is added to the first (fuel cell) one to form a fuel cell combined cycle system. The procedure for developing a network of heat exchangers and proper integration of the steam turbine system with an optimized minimum temperature difference is discussed. The results of the study elucidate the advantages of properly designed fuel cell combined cycle system to reach power demand with 17% higher efficiency as compared with the system without a combined cycle.
An Investigation of DIR-MCFC Based Cooling, Heating and Power System
Authors: Samanta Indraneel , Shah Ramesh K. , Ogut Ali
Published: January 2009

The fuel cell is an emerging technology for stationary power generation because of their higher energy conversion efficiency and extremely low environmental pollution. Fuel cell systems with cogeneration have even higher overall efficiency. Cogeneration can be defined as simultaneous production of electric power and useful heat from burning of single fuel. A fuel cell produces electrical energy by electrolytic process involving chemical reaction between H2 (fuel) and O2 (Air). Previous works have focussed on running the system in combination with gas turbines. We investigate the possibility of running an absorption chiller as a cogeneration system focussing on a 250 kW Direct Internal Reforming Molten Carbonate Fuel Cell (DIR-MCFC) powering a LiBr-Water absorption chiller. The objective of this work is to propose a cogeneration system capable of enhancing the profitability and efficiency of a MCFC for independent distributed power generation. Natural gas is used as fuel and O2 is used from atmospheric air. Two possibilities are evaluated to recover heat from the exhaust of the MCFC: (1) all waste heat available being used for providing hot water in the building and powering an absorption chiller in summer, and (2) hot water supply and space heating in winter. There is an increased cost saving for each case along with improved system efficiency. Based on these considerations payback period for each case is presented.
Systems Analysis of Diesel Based Fuel Cells for Auxiliary Power Units
Authors: Berry David A. , James Robert , Gardner Todd H. , Shekhawat Dushyant
Published: January 2009

The near-term commercial success for many fuel cell technologies will rely on their ability to utilize current infrastructure fuels. Several large ready-markets exist for fuel cell systems that utilize middle distillate petroleum fractions like diesel fuel. One particular application is diesel-based auxiliary power units (APU). Unfortunately, very little research and development has been devoted to this application. Ongoing research at the National Energy Technology Laboratory (NETL) and other organizations is trying to address this need. In order for a fuel cell to utilize diesel fuel, it must be reformed into a synthesis gas containing primarily hydrogen, carbon monoxide, carbon dioxide, steam and possibly methane. Because catalytic reforming of hydrocarbon fuels is conducted at the same relative operating temperatures of technologies like solid oxide fuel cells (800–1000°C) a high degree of thermal integration is possible. Unfortunately, carbon deposition and sulfur poisoning of catalysts in the reformer and fuel cell make system operation potentially complicated and costly. To help understand and quantify the impact of these issues on technology development and component, a number of systems analysis was conducted for a diesel-based fuel cell system. One particular system based on a hybrid combustor/reformer concept allowed for excellent utilization of available heat from the fuel cell and yielded an overall fuel to electric conversion efficiency of nearly 50%. This paper discusses its salient features and compares its characteristics to other possible system configurations.
An Engineering System for Automated Design and Optimization of Fuel Cell Powered Vehicles
Authors: Wipke Keith , Chintawar Prashant , Weller Rick , Willis Gordon
Published: January 2009

NREL has contracted Vulcanworks to provide an Advanced Engineering Environment (AEE) configured for development of automotive vehicles powered by fuel cell/fuel processor systems. Nuvera Fuel Cells, Inc, provided information for development of relationships and mathematical models of fuel cell and fuel processors. The Vulcanworks AEE product is an integrated set of tools, tailored to solve design problems in specific environments and processes. The AEE allows extremely rapid iteration of system designs, with automated analysis capability. It contains a database of design and manufacturing rules, an automated geometry creation engine, links to a variety of CAE analysis packages, and a Web-browser interface. This paper describes a prototype AEE developed for design of vehicles powered by fuel cell/fuel processor systems, including an optimization capability for packaging the propulsion components. It also describes the use of the prototype to assess the following design task: Optimize the percentage of full power available for the first five minutes of operation from startup. The last section of the paper briefly describes the characteristics of the final design of the AEE, which is planned for developed in further phases of the contract.
Modeling of Two-Phase Flow in a Cathode Duct of PEM Fuel Cells
Authors: Yuan Jinliang , Rokni Masoud , Sunde´n Bengt
Published: January 2009

In this study, a fully three-dimensional model has been developed to simulate two-phase, multi-component gas and heat transport processes in a PEMFC cathode duct. The effects of the electrochemical reactions on the heat generation and mass transfer have been taken into account. Based on the calculated values of water vapor partial pressure and temperature, occurrence of liquid water has been predicted and its effects on the heat generation (caused by water condensation) are also considered. Variable thermal-physical properties, local pressure and non-uniform temperature are calculated and updated in the simulation. It is revealed that the mass fraction and location of the regions of the liquid water are very sensitive to the operating parameters. The gas species convection transport in the porous layer is of significance and must be considered in PEMFC modeling.
The Influence of Water and Thermal Conditions on the Performance of PEM Fuel Cell
Authors: Yan Y. Y. , Sung L. Y. , Chu H. S. , Tsay K. C. , Tsu F. S. , Chen F. , Shyu R. J.
Published: January 2009

The conditions of water content in the proton exchange membrane fuel cell (PEMFC) are studied in this research. It is known that the hydrogen proton should accompany with water molecule in order to drift through the membrane from anode to cathode. This drift force will concern to the fuel cell performance. However, too much water content may result of flooding. When flooding appears, some catalyst surfaces may be covered with water and result of the catalysts inactive. This will reduce the electrochemical reaction rate. Furthermore, due to the water molecule will occupy the space, this will hinder the reactant molecules approaching to the catalyst. Therefore, the management of water for the fuel cells is very important. The performance can be optimized with a better control of cell conditions. Some important conditions that concern to the heat and water management are investigated. They include cell temperature, reactant flow rate, humidity and pressure. A standard single cell stack with active area of 25cm2 was set for this study.
The Vision for Solid Oxide Fuel Cells: Development of a SOFC APU for the Transportation Industry
Authors: Mukerjee S. , De Minco C.
Published: January 2009

Delphi Corporation is developing Solid Oxide Fuel Cell (SOFC) technology for applications in the transportation and residential markets. Delphi is developing this technology for the automotive and heavy duty trucking markets primarily as an on-board Auxiliary Power Unit (APU). In the first application of this program, the APU will be used to power “hotel loads” i.e. an electric air conditioning system without the need for operating the vehicle’s engine.
Validation and Application of a CFD-Based Model for Solid Oxide Fuel Cells and Stacks
Authors: Rogers William A. , Gemmen Randall S. , Johnson Christopher , Prinkey Michael , Shahnam Mehrdad
Published: January 2009

The National Energy Technology Laboratory (NETL) has developed a solid oxide fuel cell (SOFC) model based on commercial computational fluid dynamics (CFD) software. This new tool is being used to support the US DOE Solid State Energy Conversion Alliance Fuel Cell Program, which will require advanced fuel cell designs in order to meet the program goal of reaching $400/kW for small (∼5kW) systems. The NETL model combines a special SOFC electrochemical model with an electrical potential field model in the finite-volume commercial CFD code from Fluent Incorporated (Lebanon NH). Mass and energy sources and sinks resulting from the electrochemical reactions and electrical current flow are coupled to the fluid flow, chemical species transport, heat transfer, porous media flow, and gas phase chemistry capabilities available in the base CFD model. The NETL SOFC model has also been recently extended to model SOFC stacks with cells connected in electrical series. The model is able to predict detailed, spatially resolved current flow through the electrolyte and through all conducting media in three-dimensional SOFC cells and cell stacks. In conjunction with the SOFC model development program, NETL has an experimental facility in place to generate data for validation of the SOFC model. The experimental program includes collaboration with the University of Utah, a supplier of test specimens and preliminary cell performance data. Well-characterized SOFC test specimens are being tested in the NETL fuel cell test stands for single cell and short-stack arrangements. Anode-supported cells with controlled electrode microstructures, electrode thickness, and electrolyte thickness are being tested. Operating data from the test stands includes cell and stack polarization curves, temperature data, and chemical composition of reactant streams. Using NETL and University of Utah data, an extensive validation program is now underway for the NETL SOFC model. The model is being tested using a simple button-cell configuration. A parametric study of varying operating conditions, cell geometries and cell properties is being performed. Good agreement between predicted and measured cell performance has been observed and is presented. The model has also been applied to planar single cell and cell stack configurations to help in the design of NETL experimental test facilities.
Techno-Economic Challenges for PEMFCs and DMFCs Entering Energy Sector
Authors: Srinivasan S. , Dillon R. , Krishnan L. , Arico A. S. , Antonucci V. , Bocarsly A. B. , Lee W. J. , Hsueh K.-L. , Lai C.-C. , Peng A.
Published: January 2009

Proton Exchange Membrane Fuel Cells (PEMFC) and Direct Methanol Fuel Cells (DMFC) have been in the forefront of all fuel cell technologies for transportation and portable power applications. This is mainly because of the quantum/semi-quantum jumps in these technologies. However, there are several techno-economic challenges for these types of fuel cells to enter the energy sector. The cell structures and operating principles of PEMFC and DMFC are similar to each other. However, techno-economic challenges for PEMFCs are significantly different from those for DMFCs, due to their applications, associated competing technologies, global market, and manufacturing environment. Both types of fuel cell are close to entering the energy sector now, more than ever before. Significant reduction of PEMFCs capital cost and miniaturization of DMFCs are two critical issues. Intense research and development efforts are needed with respect to (i) finding better and less expensive electrocatalysts and proton conducting membranes (ii) optimization of structure and composition of membrane and electrode assemblies, (iii) automation of techniques to fabricate cell and stack components, and (iv) finding efficient and cost effective methods for thermal and water management.
Performance of a Solar Thermal Parabolic Trough Concentrator for Industrial Process Heat (IPH) Applications in Egypt
Authors: Fatouh M. , Nabil M. , Mahmoud E. , Mahmoud M. K.
Published: January 2009

In Egypt, surveying the industrial sectors revealed that in the last few years the industrial process heat (IPH) consumed more than 60% of the annual industrial energy demand, of which about 50% is in the temperature range from 80 to 150°C. Among different renewable energy resources, it is found that solar thermal technologies, especially parabolic trough concentrators (PTC) are more convenient for the IPH applications. Thus, the present work deals with studying the main design and performance characteristics that enable the local manufacturing of a PTC for IPH applications in the range of 80 to 150°C in Egypt. It includes theoretical and experimental parts. The theoretical part was conducted using a specially developed computer program based on the energy balance equations of each component of PTC. The experimental part was carried out on a test rig designed and constructed using mainly local manufacturing capabilities. Effects of concentration ratio, radiation, inlet temperature and mass flow rate of the heat transfer fluid, glass envelope diameter and top thermal insulation on the theoretical and experimental performance of PTC are graphically reported. Finally, a brief discussion of the local manufacturing possibilities as well as some identified barriers that can hinder promotion of the technology in a very suitable and huge market like Egypt is presented in this paper.
Effect of Voltage Level on Power System Design for Solar Electric Propulsion Missions
Authors: Kerslake Thomas W.
Published: January 2009

This paper presents study results quantifying the benefits of higher voltage, electric power system designs for a typical solar electric propulsion spacecraft Earth orbiting mission. A conceptual power system architecture was defined and design points were generated for system voltages of 28-V, 50-V, 120-V and 300-V using state-of-the-art or advanced technologies. A 300-V “direct-drive” architecture was also analyzed to assess the benefits of directly powering the electric thruster from the photovoltaic array without up-conversion. Fortran and spreadsheet computational models were exercised to predict the performance and size power system components to meet spacecraft mission requirements. Pertinent space environments, such as electron and proton radiation, were calculated along the spiral trajectory. In addition, a simplified electron current collection model was developed to estimate photovoltaic array losses for the orbital plasma environment and that created by the thruster plume. The secondary benefits of power system mass savings for spacecraft propulsion and attitude control systems were also quantified. Results indicate that considerable spacecraft wet mass savings were achieved by the 300-V and 300-V direct-drive architectures.
A Deterministic Method for Aligning Multiple Optical Waveguides to a Paraboloidal Collector
Authors: Maxey L. C. , Hilson B. J.
Published: January 2009

For solar lighting systems employing fiber optic waveguides1,2, to conduct the collected light, paraboloidal mirrors are the preferred reflector choice. To achieve optimum performance in systems with relatively small collection apertures, both the quality of the mirror and the quality of optical system alignment must be well controlled. In systems employing multiple waveguides with a single paraboloid, the focus of the paraboloid must be segmented into several separate focal points directed into individual fibers. Each waveguide entrance aperture must be accurately co-located with its designated focal point so that the image that is formed on the fiber will have the fewest possible aberrations and thus, the smallest possible focused spot size. Two methods for aligning individual optical waveguides in a multi-aperture paraboloidal collection system are described. The first method employs a commercially available collimation tester to incrementally improve the alignment. The second, a deterministic method, employs a cube corner retro-reflector and an easily constructed imaging system to reliably align the fibers to their respective segments of the parent paraboloid. The image of the focused spot formed by the light that is returned from the retro-reflector reveals alignment information that is easily interpreted to enable pitch, yaw and focus errors to be systematically removed. This ensures that the alignment of the system is optimized to reduce aberrations prior to final adjustment of the system “on-sun”.
Exergetic, Thermal, and Externalities Analyses of a Cogeneration Plant
Authors: Bailey Margaret B. , Curtiss Peter , Blanton Paul H. , McBrayer Thomas B.
Published: January 2009

A thermodynamic study of an 88 MW cogeneration plant located in the United States is presented. The plant is singled out for consideration since the feedstock consists of waste anthracite culm banks. The culm banks remain on the ground surface after decades of active coal mining in the region. Before combustion, usable coal within the culm is separated from the indigenous rock and conveyed to circulating fluidized bed (CFB) boilers. The indigenous rock and ashes from combustion are used as fill in adjacent land previously scared by strip mining. Trees and grass are planted in these areas as part of a land reclamation program. The research reported here includes the results of thermodynamic analyses of the cogeneration plant cycle and processes. Analyses based on the First and Second Laws of Thermodynamics are first presented to acquaint the reader with the plant’s components and operation. Data used in the calculations are based on actual operating data obtained at the cogeneration plant during a mass and energy balance study conducted in the late 1990’s. The data are average values and indicative of the plant’s base load operating state. Using emission and other relevant environmental data from the plant, an externalities study is outlined that estimates the plant’s effect on the local population.
The Holographic Solar Photon Thruster (SPT) : A Low-Earth Orbit Solar Sail
Authors: Matloff Gregory L.
Published: January 2009

Atmospheric drag limits most solar sails to altitudes>1000 km. A two-sail variant, the Solar-Photon Thruster (SPT) , could be used in Low-Earth Orbit (LEO). An SPT has a fixed-orientation collector sail that focuses light against a smaller, adjustable thruster sail. Maintaining the collector surface parallel to the Earth minimizes SPT drag in LEO. To minimize solar-radiation back pressure towards Earth, the upper collector surface is non-reflective. The reflective lower collector surface directs light reflected and reradiated from the Earth against the thruster. Thruster orientation is adjusted in LEO to increase the orbital energy by the net radiation-pressure. Experiments reveal that holograms are tolerant to solar-wind radiation. SPTs with white-light holographic thrusters are useful in LEO because small thruster rotations produce greatly altered reflectivity. It may be possible to holographically combine SPT collector and thruster.
Proposal of Simultaneous Production Method of Hydrogen and Hydrogen Peroxide From Water Using Solar Photo-Electrochemistry
Authors: Ando Yuji , Tanaka Tadayoshi
Published: January 2009

Authors have proposed a new hydrogen production system that simultaneously synthesizes hydrogen and hydrogen peroxide from water by electrochemical reaction. Experimental apparatus of this system is composed of a hydrogen electrode with platinum mesh, a hydrogen peroxide electrode with carbon material and an electrolyte with Nafion®. In this paper, the superiority of this system is outlined. In addition, the experimental results of electrolytic synthesis of hydrogen and hydrogen peroxide from water are reported. Furthermore, the possibility of the system that synthesizes hydrogen and hydrogen peroxide from water by the photochemical reaction using solar radiation is also discussed.
Development of Small-Scale Multi-Effect Solar Still
Authors: Yamaguchi Yuichi , Sato Haruki
Published: January 2009

The diffusion of solar distillation systems is necessary to solve a global problem on serious shortage of safe water resources in many developing countries such as Bangladesh. The solar still is required to be low cost, to have reliability for the safety and long durability, to be free from maintenance without any expendable supplies, having high performance, and it should be an environmentally friend device working without any fossil fuel. The economical balance to develop stills for residential purpose is considered. A 10 kg·day−1-scale solar still was developed and the characteristics are introduced. A conceptual design of a new 20–50 kg·day−1-scale multi-stage solar still is also introduced in this paper.
Model Calibration From Short-Term Test Data for Unpressurized Integral-Collector-Storage Systems
Authors: Burch Jay D. , Thornton Jeff W. , Liu Wei , Davidson Jane H. , Ruby Trisha S.
Published: January 2009

A method of test is defined and instantiated for integral-collector-storage solar systems with a load-side heat exchanger immersed in the storage. A “system test/model calibration” approach is used. The test protocol consists of short-term tests and an extended validation test. Short-term tests include warmup tests, a decay test, and heat exchanger tests. The model parameters to be determined are the normal incidence transmission-absorption product, an additive correction to the total heat loss, and heat exchanger parameters correlating the ratio of modeled to measured heat exchanger fluxes. The calibrated system model resulting from the short-term tests is then validated against typical operation data. The calibrated model presented here under-predicts delivered energy over a 5-day period of normal operation by 11%, perhaps because of the present lack of modeling for the tank stratification induced during charging by solar radiation.
Performance Study of Wind Turbine Generators
Authors: Bhagwatikar G. R. , Gandhare W. Z.
Published: January 2009

It is well known that the wind power has definitely certain impact on the grid power. Issues associated with the integration of wind power into the utility grid are interface issues, operational issues and planning issues. Interface issues include harmonics, reactive power consumption, voltage regulation and frequency control. Operational issues are intermittent power generation, operating reserve requirements, unit commitment and economic despatch. And planning issues are concerned with intermittent wind resources compared to conventional power resources. An important question, when connecting the wind turbine generators to the utility grid, is how much the power / voltage quality will be influenced, since the power production by wind turbines is intermittent, quantity wise as well as quality wise. This paper is focused on the on comparison between the constant speed wind turbines and variable speed wind turbines, reactive power consumption and harmonics generated by both wind turbines. Total harmonic distortion is calculated by the application of C++ software and a comparison is done between the generators with respect to the harmonics. It is observed that constant speed wind turbine generates low order harmonics and variable speed turbine generates high order harmonics. On the basis of results, some solutions are suggested to improve the wind power quality and to reduce reactive power consumption. It seems that variable speed wind turbines with electronic interface are better with respect to the utility grid point of view.
Simulation About Suitable Direction of Photovoltaic Array for Residential Solar Power Generation System
Authors: Sakai Koji , Ishihara Osamu , Tanaka Akio , Nakagami Hidetoshi , Manabe Masaki
Published: January 2009

In this paper, it is attempted in the present study to estimate the factors to reduce power generating efficiency using the results of measurements and to calculate the optimal tilt angle in Kyushu area. Also, the study was made as to how the annual power generation amount is influenced by the deviation of the optimal tilt angle from actual installation angle. We have obtained the results that modeling was performed on the factors to reduce the efficiency obtained from measurements, and PV power generation amount in Kyushu area was estimated. Also, from the results of calculation of the optimal installation angle of the fixed system at installation site, it was demonstrated that the installation of PV systems on roof surface as generally practiced at present did not lead to a greater loss.