Performance Comparison of Internal Reforming Against External Reforming in a SOFC, Gas Turbine Hybrid System

2003 ◽  
Author(s):  
Eric A. Liese ◽  
Randall S. Gemmen
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Waste Heat ◽  
Performance Comparison ◽  
Internal Reforming ◽  
Base Concept ◽  
Thermodynamic Performance ◽  
Cell Current ◽  
Hybrid Configuration ◽  
Better Than

Solid Oxide Fuel Cell (SOFC) manufacturers are presently considering both internal and external reforming fuel cell designs. Generally, the endothermic reforming reaction and excess air through the cathode provide the cooling needed to remove waste heat from the fuel cell. Current information suggests that external reforming fuel cells will require a flow rate twice the amount necessary for internal reforming fuel cells. The increased airflow could negatively impact system performance. This paper compares the performance among various external reforming hybrid configurations and an internal reforming hybrid configuration. A system configuration is introduced that uses interstage external reforming. Results show that that the thermodynamic performance of an interstage reforming system is an improvement over a base-concept external approach, and may be slightly better than the hybrid with an internal reforming fuel cell.

Performance Comparison of Internal Reforming Against External Reforming in a Solid Oxide Fuel Cell, Gas Turbine Hybrid System

2005 ◽  
Vol 127 (1) ◽  
pp. 86-90 ◽  
Author(s):  
Eric A. Liese ◽  
Randall S. Gemmen
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Hybrid System ◽  
Waste Heat ◽  
Performance Comparison ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Internal Reforming ◽  
Hybrid Configuration

Solid Oxide Fuel Cell (SOFC) developers are presently considering both internal and external reforming fuel cell designs. Generally, the endothermic reforming reaction and excess air through the cathode provide the cooling needed to remove waste heat from the fuel cell. Current information suggests that external reforming fuel cells will require a flow rate twice the amount necessary for internal reforming fuel cells. The increased airflow could negatively impact system performance. This paper compares the performance among various external reforming hybrid configurations and an internal reforming hybrid configuration. A system configuration that uses the reformer to cool a cathode recycle stream is introduced, and a system that uses interstage external reforming is proposed. Results show that the thermodynamic performance of these proposed concepts are an improvement over a base-concept external approach, and can be better than an internal reforming hybrid system, depending on the fuel cell cooling requirements.

A Numerical Investigation of Heat and Mass Transfer in Air-Cooled Proton Exchange Membrane Fuel Cells

2019 ◽  
Author(s):  
Torsten Berning
Keyword(s):  
Heat Transfer ◽  
Fuel Cells ◽  
Fuel Cell ◽  
Proton Exchange Membrane ◽  
Waste Heat ◽  
Proton Exchange ◽  
Fuel Cell Performance ◽  
Air Stream ◽  
Multi Phase ◽  
Exchange Membrane

Abstract A numerical analysis of an air-cooled proton exchange membrane fuel cell (PEMFC) has been conducted. The model utilizes the Eulerian multi-phase approach to predict the occurrence and transport of liquid water inside the cell. It is assumed that all the waste heat must be carried out of the fuel cell with the excess air which leads to a strong temperature increase of the air stream. The results suggest that the performance of these fuel cells is limited by membrane overheating which is ultimately caused by the limited heat transfer to the laminar air stream. A proposed remedy is the placement of a turbulence grid before such a fuel cell stack to enhance the heat transfer and increase the fuel cell performance.

Conversion of Syngas From Biomass in Solid Oxide Fuel Cells

2006 ◽  
Author(s):  
Ju¨rgen Karl ◽  
Nadine Frank ◽  
Sotiris Karellas ◽  
Mathilde Saule ◽  
Ulrich Hohenwarter
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Liquid Metal ◽  
Waste Heat ◽  
Heat Pipes ◽  
Economic Feasibility ◽  
Small Scale ◽  
Cell Systems ◽  
Exhaust Heat ◽  
Integrated Gasification

Conversion of biomass in syngas by means of indirect gasification offers the option to improve the economic situation of any fuel cell systems due to lower costs for feedstock and higher power revenues in many European countries. The coupling of an indirect gasification of biomass and residues with highly efficient SOFC systems is therefore a promising technology for reaching economic feasibility of small decentralized combined heat and power production (CHP). The predicted efficiency of common high temperature fuel cell systems with integrated gasification of solid feedstock is usually significantly lower than the efficiency of fuel cells operated with hydrogen or methane. Additional system components like the gasifier, as well as the gas cleaning reduce this efficiency. Hence common fuel cell systems with integrated gasification of biomass will hardly reach electrical efficiencies above 30 percent. An extraordinary efficient combination is achieved in case that the fuel cells waste heat is used in an indirect gasification system. A simple combination of a SOFC and an allothermal gasifier enables then electrical efficiencies above 50%. But this systems requires an innovative cooling concept for the fuel cell stack. Another significant question is the influence of impurities on the fuel cells degradation. The European Research Project ‘BioCellus’ focuses on both questions — the influence of the biogenious syngas on the fuel cells and an innovative cooling concept based on liquid metal heat pipes. First experiments showed that in particular higher hydrocarbons — the so-called tars — do not have an significant influence on the performance of SOFC membranes. The innovative concept of the TopCycle comprises to heat an indirect gasifier with the exhaust heat of the fuel cell by means of liquid metal heat pipes. Internal cooling of the stack and the recirculation of waste heat increases the system efficiency significantly. This concept promises electrical efficiencies of above 50 percent even for small-scale systems without any combined processes.

Effects of Operating Conditions on the Heat Management of a Microscale Fuel Cell

2019 ◽  
Author(s):  
Liyong Sun ◽  
Adam S. Hollinger ◽  
Jun Zhou
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Waste Heat ◽  
Heat Removal ◽  
Current Collector ◽  
Ambient Air ◽  
Operating Conditions ◽  
Heat Management ◽  
Fuel Flow ◽  
Fuel Stream

Abstract Higher energy densities and the potential for nearly instantaneous recharging make microscale fuel cells very attractive as power sources for portable technology in comparison with standard battery technology. Heat management is very important to the microscale fuel cells because of the generation of waste heat. Waste heat generated in polymer electrolyte membrane fuel cells includes oxygen reduction reaction in the cathode catalyst, hydrogen oxidation reaction in the anode catalyst, and Ohmic heating in the membrane. A novel microscale fuel cell design is presented here that utilizes a half-membrane electrode assembly. An ANSYS Fluent model is presented to investigate the effects of operating conditions on the heat management of this microscale fuel cell. Five inlet fuel temperatures are 22°C, 40°C, 50°C, 60°C, and 70°C. Two fuel flow rate are 0.3 mL/min and 2 mL/min. The fuel cell is simulated under natural convection and forced convection. The simulations predict thermal profiles throughout this microscale fuel cell design. The exit temperature of fuel stream, oxygen stream and nitrogen stream are obtained to determine the rate of heat removal. Simulation results show that the fuel stream dominates heat removal at room temperature. As inlet fuel temperature increases, the majority of heat removal occurs via convection with the ambient air by the exposed current collector surfaces. The top and bottom current collector removes almost the same amount of heat. The model also shows that the heat transfer through the oxygen channel and nitrogen channel is minimal over the range of inlet fuel temperatures. Increasing fuel flow rate and ambient air flow both increase the heat removal by the exposed current collector surfaces. Ultimately, these simulations can be used to determine design points for best performance and durability in a single-channel microscale fuel cell.

Performance Analysis on SOFC-HCCI Engine Hybrid System

2012 ◽  
Author(s):  
Sung Ho Park ◽  
Young Duk Lee ◽  
Sang Gyu Kang ◽  
Kook Young Ahn
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Hybrid Systems ◽  
Hybrid System ◽  
Gas Turbines ◽  
Waste Heat ◽  
Metal Catalyst ◽  
Molten Carbonate ◽  
Hcci Engine ◽  
Ci Engines

Fuel cell systems are currently regarded as a promising type of energy conversion system. Various types of fuel cell have been developed and investigated worldwide for portable, automotive, and stationary applications. In particular, in the case of large-scale stationary applications, the high-temperature fuel cells known as the molten carbonate fuel cell (MCFC) and the solid oxide fuel cell (SOFC) have been used as a power source due to their higher efficiency compared to low-temperature fuel cells. Because SOFCs have many advantages, including a high power density, low corrosion, and operability without a metal catalyst, many efforts to develop a SOFC hybrid system have been undertaken. SOFC hybrid systems with a gas turbine or engine show improved system efficiency through their utilization of waste heat and unreacted fuel. Especially, the internal combustion engine has the advantage of robustness, easy maintenance, and a low cost compared to gas turbines, this type is more adaptable for use in a hybrid system with a SOFC. However, the engine should be operated stably at a high air fuel ratio because the SOFC anode exhaust gas has a low fuel concentration. The homogeneous charge compression ignition (HCCI) engine has both the advantages of SI and CI engines. Moreover, the lean burn characteristics of the HCCI engine make it a strong candidate for SOFC hybrid systems. The objective of this work is to develop a novel cycle composed of a SOFC and a HCCI engine. In order to optimize the SOFC-HCCI hybrid system, a system analysis is conducted here using the commercial software Aspen Plus®. The SOFC model is validated with experimental data. The engine model is developed based on an empirical equation that considers the ignition delay time. The performance of the hybrid system is compared with that of a SOFC stand-alone system to confirm the optimization of the system. This study will be useful for the development of a new type of hybrid system which uses a fuel cell and an optimized system.

An Investigation of DIR-MCFC Based Cooling, Heating and Power System

2003 ◽  
Author(s):  
Indraneel Samanta ◽  
Ramesh K. Shah ◽  
Ali Ogut
Keyword(s):  
Power Generation ◽  
Fuel Cell ◽  
Gas Turbines ◽  
Waste Heat ◽  
Hot Water ◽  
Molten Carbonate Fuel Cell ◽  
Molten Carbonate ◽  
Absorption Chiller ◽  
Internal Reforming ◽  
Cogeneration System

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.

Fuel Cells: What’s Up Next?

2003 ◽  
Author(s):  
Kas Hemmes
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Chemical Process ◽  
Waste Heat ◽  
Exothermic Reaction ◽  
Process Industry ◽  
Chemical Process Industry ◽  
Cell Technology ◽  
Fuel Cell Technology ◽  
Direct Carbon Fuel Cell

Fuel cells are defined as devices that convert chemical energy into heat and electric power. However, depending on their type, fuel cells have special features that can be used advantageously in for instance the chemical process industry of which examples will be given. Nevertheless these new applications use existing fuel cells like the MCFC. This is very exiting and many new possibilities are yet to be explored. However there is no principle reason why we should limit fuel cell technology to present types and the well known fuels like hydrogen, methane and methanol and air as oxidant. Recently interest in the direct conversion of carbon as a fuel has revived which has led to the development of a DCFC (direct carbon fuel cell) based on MCFC technology. Lawrence Livermore National Lab has demonstrated the DCFC successfully on a bench scale size. Also H2S is considered as a fuel. Further ahead opportunities are to be explored by replacing exothermic reaction in the chemical process industry such as partial oxidation reactions by their electrochemical counterpart. Thereby electricity is generated instead of excessive waste heat. Now that fuel cell technology is getting mature we can think of adopting this technology in new dedicated fuel cell types, with relatively short development trajectories, for application in totally new fields where electricity may just be a by-product.

scholarly journals Three-Dimensional Based Model of a Planar SOFC Fuelled by Biomass Gas

2006 ◽  
Author(s):  
Stefano Cordiner ◽  
Massimo Feola ◽  
Vincenzo Mulone ◽  
Fabio Romanelli
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Electrochemical Reaction ◽  
Electrical Response ◽  
Operating Conditions ◽  
Cell Performance ◽  
Gas Composition ◽  
Minimization Method ◽  
Fuel Cell Performance ◽  
Internal Reforming

Efficient and low polluting production of electricity and heat is an issue which cannot be postponed. Fuel cells, which convert the chemical energy stored in a fuel into electrical and thermal energy, are an efficient solution for such a problem. These devices rely on the combination of hydrogen and oxygen into water: oxygen is extracted from the air while hydrogen can be obtained from either fossil fuels or renewable sources. The use of biomass as hydrogen source in connection with fuel cells is an argument of particular interest, since high temperature gasification processes are actually utilized. Solid Oxide Fuel Cells (SOFC), working at high temperatures, have become therefore an interesting candidate to realize the internal reforming of the feed gas from a gasifier. The reforming reaction occurs at the anode of the SOFC, upstream and separated from the fuel cell reaction. The section of the anode where reforming occurs is adjacent to the section where electrochemical reaction occurs. So, heat produced by the electrochemical reaction can be transferred internally with minimal losses. Simulation models of the performance of SOFC stacks and biomass gasifiers are useful to visualize temperature, current and concentration distributions, which are difficult to measure by experimental techniques, allowing the definition of optimal choices in terms of geometries and operating conditions. In this work, an analysis of a SOFC coupled with a biomass gasifier is performed. The objective of this study is the identification of the main effects of the operating conditions on the fuel cell performance in terms of efficiency, and the distribution of the main electro-thermal-fluid-dynamics variables, namely current and temperature. A gasifier model has been implemented to calculate the equilibrium compositions using the Gibbs free energy minimization method. The obtained results are directly used to estimate the inlet gas composition for the SOFC. The SOFC has been modelled by a 3D approach (FLUENT), which solves the energy and mass transport and the internal reforming, coupled with a 0D electrolyte model which, starting from the local information in terms of gas composition, temperature and pressure, is able to predict the fuel cell performance in terms of electrical response and mass-energy fluxes. The whole model has been applied to the analysis of an integrated SOFC-gasifier system to address a planar SOFC response by varying the gasifier operating conditions and the global system performance.

Power Cycle Integration and Efficiency Increase of Molten Carbonate Fuel Cell Systems

2005 ◽  
Vol 3 (4) ◽  
pp. 375-383 ◽  
Author(s):  
Petar Varbanov ◽  
Jiří Klemeš ◽  
Ramesh K. Shah ◽  
Harmanjeet Shihn
Keyword(s):  
Fuel Cells ◽  
High Temperature ◽  
Fuel Cell ◽  
Gas Turbines ◽  
Waste Heat ◽  
Combined Cycle ◽  
Molten Carbonate Fuel Cell ◽  
Steam Turbines ◽  
Molten Carbonate ◽  
Carbonate Fuel Cell

A new view is presented on the concept of the combined cycle for power generation. Traditionally, the term “combined cycle” is associated with using a gas turbine in combination with steam turbines to better utilize the exergy potential of the burnt fuel. This concept can be broadened, however, to the utilization of any power-generating facility in combination with steam turbines, as long as this facility also provides a high-temperature waste heat. Such facilities are high temperature fuel cells. Fuel cells are especially advantageous for combined cycle applications since they feature a remarkably high efficiency—reaching an order of 45–50% and even close to 60%, compared to 30–35% for most gas turbines. The literature sources on combining fuel cells with gas and steam turbines clearly illustrate the potential to achieve high power and co-generation efficiencies. In the presented work, the extension to the concept of combined cycle is considered on the example of a molten carbonate fuel cell (MCFC) working under stationary conditions. An overview of the process for the MCFC is given, followed by the options for heat integration utilizing the waste heat for steam generation. The complete fuel cell combined cycle (FCCC) system is then analyzed to estimate the potential power cost levels that could be achieved. The results demonstrate that a properly designed FCCC system is capable of reaching significantly higher efficiency compared to the standalone fuel cell system. An important observation is that FCCC systems may result in economically competitive power production units, comparable with contemporary fossil power stations.

Solid Oxide Fuel Cell - A Future Source of Power and Heat Generation

2013 ◽  
Vol 757 ◽  
pp. 217-241 ◽  
Author(s):  
Pankaj Kalra ◽  
Rajeev Garg ◽  
Ajay Kumar
Keyword(s):  
Fuel Cells ◽  
Fuel Cell ◽  
Solid Oxide Fuel Cell ◽  
Internal Combustion Engines ◽  
Electrical Energy ◽  
Solid Oxide ◽  
Intermediate Step ◽  
Oxide Fuel ◽  
Power Sources ◽  
Internal Reforming

Fuel cells are devices for electrochemically converting the chemical energy of a fuel gas into electrical energy and heat without the need for direct combustion as an intermediate step. The main advantages of fuel cells are that they rely on the high conversion efficiency and low environmental impact than traditional energy conversion systems. One promising fuel cell type, Solid oxide Fuel Cell, has all the components in the solid phase utilises nano-ceramic composite materials and operates at elevated temperatures in the range 500-1000°C. It has suitable perspectives to replace their classical counterparts for the distributed generation of electrical energy with small and medium power sources. The inherent advantages of such high temperature fuel cells are internal reforming of methane and waste heat production at high temperatures which lower the demands on the fuel processing system and lead to higher efficiency compared with low temperature fuel cells. Using natural gas as feed, an electric efficiency of more than 88% has been predicted. On the other hand, considerable research is going on to reduce the operating temperatures between 600°C to 800°C to increase life-time and thereby reduce costs. These can be achieved only by using electrolytes with proper ionic conductivity at the intermediate temperatures. In addition, this technology does not produce significant amounts of pollutants such as nitrogen oxides compared with internal combustion engines. Solid oxide fuel cells are seen as ideal energy sources in transport, stationary, and distributed power generators.

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