Phosphoric Acid Fuel Cell System Research Articles

Expansion and optimization of ammonia import to the Republic of Korea for electricity generation

Ammonia is considered a promising energy source for achieving carbon neutrality because it is carbon-free. This study aims to evaluate the feasibility of ammonia-based power generation by conducting techno-economic and carbon footprint analyses of an integrated ammonia decomposition and phosphoric acid fuel cell system. Using a commercial process simulator, the power generation process is designed to reveal an energy efficiency of 46.7% and an upper limit for the ammonia price to compete with industrial electricity prices is identified as 421.3 $ tNH3–1 through economic analysis. Furthermore, the study establishes five different scenarios for ammonia import from the top ten exporting countries to the Republic of Korea (KOR), according to historical data, for optimization. Ammonia import is optimized in terms of exporting countries and quantities to satisfy the ammonia price while minimizing overall emissions using the Monte Carlo method for ammonia production costs and carbon dioxide emissions in each nation. The results show that carbon intensity falls within the range of 0.707–0.736 kgCO2-eq kWh−1, which exceeds the 20-year average value of carbon intensity in KOR if carbon-based ammonia is solely imported. However, the system can be competitive in terms of both economic and environmental aspects if the carbon–neutral ammonia ratio is over 78% (more than Scenario 4). In conclusion, this study statistically investigates the optimization results focusing on major ammonia export countries, identifies the trend of carbon intensity in the scenarios, and provides guidelines for reducing overall carbon intensity by considering the production, transportation, and utilization of ammonia.

A combined phosphoric acid fuel cell and direct contact membrane distillation hybrid system for electricity generation and seawater desalination

In order to gradually and efficiently harvest the exhaust heat, a novel hybrid system model containing a phosphoric acid fuel cell and a direct contact membrane distillation is established for electricity generation and seawater desalination. Power output, energy efficiency, exergy destruction rate, and exergy efficiency of the proposed hybrid system, as crucial performance indicators, are mathematically derived by taking a series of irreversible losses into account. The basic performance characteristics of the hybrid system are revealed. The maximum power output density of the hybrid system, its corresponding energy efficiency and exergy efficiency are approximately 57.1%, 82.2% and 82.3% larger than that of the single phosphoric acid fuel cell system, respectively. Furthermore, extensive parametric studies are carried out to study the dependence of the proposed hybrid system performance on some operating conditions. It is found that an increase in the operation temperature, exchange current density, feed water temperature, flow velocity of permeate water or flow velocity of feed water is beneficial to the hybrid system performance, while an increase in phosphoric acid concentration or permeate water temperature is detrimental to the hybrid system performance. The results can provide some theoretical guidance for optimally running such a hybrid system.

Energetic, exergetic and ecological evaluations of a hybrid system based on a phosphoric acid fuel cell and an organic Rankine cycle

The waste heat from phosphoric acid fuel cells is available and suitable for additional power generation by means of organic Rankine cycles. A new hybrid system model is proposed by integrating a phosphoric acid fuel cell with an organic Rankine cycle, where the organic Rankine cycle model is modified in absence of complex working fluid properties. The energetic, exergetic and ecological performances for the phosphoric acid fuel cell-organic Rankine cycle hybrid system are evaluated based on thermodynamic laws and steady-state mathematical models. Numerical results show that maximum power output density and maximum ecological objective function density of the hybrid system are 6036.7 W m−2 (at 9470.8 A m−2) and 2913.1 W m−2 (at 7050.8 A m−2), which are increased about 25.2% and 57.5% by comparing to that of the single phosphoric acid fuel cell system, respectively. Optimum working regions of various performance parameters are determined considering the trade-offs between multiple optimization criteria. Furthermore, the impacts of the operating temperature, exchange current density, electrolyte thickness and pinch temperature ratio on the hybrid system performance are analyzed. The derived results may offer some help for understanding the energetic, exergetic and ecological performances of such an actual cogeneration system.

Performance analyzes of an integrated phosphoric acid fuel cell and thermoelectric device system for power and cooling cogeneration

In addition to electricity generation, phosphoric acid fuel cell (PAFC) produces a significant amount of waste heat. In this study, a hybrid system mainly consisting of a PAFC, a thermoelectric generator, and a thermoelectric cooler is proposed to recover the produced waste heat aiming for performance enhancement. Considering thermodynamic and electrochemical irreversible losses within the system, an analytical relationship between the dimensionless electric current of the thermoelectric element and the current density of the PAFC is derived. Analytical formulas for power density and efficiency of the hybrid system are derived. The characteristics and the optimum criteria evaluating the performance parameters are revealed for the studied system. Numerical solutions show that the power density and efficiency of the hybrid system allow 2.3% and 2.8% larger than that of a stand-alone PAFC, respectively. The present hybrid system is found to be feasible and effective. Comprehensive parametric studies are conducted to analyze the effects of operating conditions and design parameters on the proposed system. The conclusions drawn can provide theoretical guidance for PAFC performance enhancements and system designs.

Various control schemes of power management for phosphoric acid fuel cell system

Abstract In this paper, the analysis of phosphoric acid fuel cell (PAFC) system is presented. Various control schemes of power management e.g. current, voltage, power, reactants flow pressure and temperature based control schemes are proposed with simple and easy to implement PI controller for PAFC operation. These control schemes can be utilized for power management purpose. The proposed model of PAFC along with these control schemes is realized in the MATLAB/Simulink environment. The performance of a PAFC system along with these proposed control schemes is found to be satisfactory even under dynamic conditions.

Modeling and Control of a Grid Connected PAFC System

This paper presents a closed-loop control of a 440kW fuel cell system including power electronics and grid side filters. Simulation results show the dynamics of a phosphoric acid fuel cell (PAFC) and its associated power electronics including grid connection. The proposed model is based on empirical equations and Simulink blocks. The modeling and simulation is done in Matlab/Simulink software with its Power System Blockset (PSB). This model mathematically calculates cell output voltages and their consequent losses. Moreover, this model includes dc power conversion of fuel cell output into ac and grid interface. Presented model is simple and easy to understand.

Multi-objective optimisation analysis and load matching of a phosphoric acid fuel cell system

Based on the current model of a phosphoric acid fuel cell (PAFC) system, the electrolyte concentration is optimised. New analytical expressions for the power output and efficiency of the PAFC system are derived by considering the effects of multi-irreversibilities resulting from the activation overpotential, concentration overpotential, ohmic overpotential, and leakage resistance on the performance of the PAFC system. These parameters are used to evaluate the general performance characteristics of the PAFC system. Accordingly, the upper and lower limits of the optimised values for some main parameters, such as the current density, power output, and efficiency, are determined. Moreover, a multi-objective function, including both the power output and efficiency, is introduced and used to further subdivide the parametric optimum regions according to different requirements. In addition, a general formula for the load of the system is derived. The relations between the power output and efficiency of the system and the load are discussed in detail, and the optimum matching conditions of the load are obtained.

Optimizing the Design and Deployment of Stationary Combined Heat and Power Fuel Cell Systems for Minimum Costs and Emissions—Part II: Model Results

The maximizing emission reductions and economic savings simulator (MERESS) is an optimization tool that evaluates novel strategies for installing and operating combined heat and power (CHP) fuel cell systems (FCSs) in buildings. This article discusses the deployment of MERESS to show illustrative results for a California campus town and, based on these results, makes recommendations for further installations of FCSs to reduce greenhouse gas (GHG) emissions. MERESS is used to evaluate one of the most challenging FCS types to use for GHG reductions, the phosphoric acid fuel cell (PAFC) system. These PAFC systems are tested against a base case of a CHP combined cycle gas turbine (CCGT). Model results show that three competing goals (GHG emission reductions, cost savings to building owners, and FCS manufacturer sales revenue) are best achieved with different strategies but that all three goals can be met reasonably with a single approach. According to MERESS, relative to a base case of only a CHP CCGT providing heat and electricity with no FCSs, the town achieves the highest (1) GHG emission reductions, (2) cost savings to building owners, and (3) FCS manufacturer sales revenue each with three different operating strategies, under a scenario of full incentives and a $100/tonne carbon dioxide (CO2) tax (scenario D). The town achieves its maximum CO2 emission reduction, 37% relative to the base case with operating strategy V: stand-alone (SA) operation, no load following (NLF), and a fixed heat-to-power ratio (FHP) (SA, NLF, and FHP; scenario E). The town’s building owners gain the highest cost savings, 25% with strategy I: electrically and thermally networked (NW), electricity power load following (ELF), and a variable heat-to-power ratio (VHP) (NW, ELF, and VHP; scenario D). FCS manufacturers generally have the highest sales revenue with strategy III: NW, NLF with a FHP (NW, NLF, and FHP; scenarios B, C, and D). Strategies III and V are partly consistent with the way that FCS manufacturers design their systems today, primarily as NLF with a FHP. By contrast, strategy I is novel for the fuel cell industry, in particular, in its use of a VHP and thermal networking. Model results further demonstrate that FCS installations can be economical for building owners without any carbon tax or government incentives. Without any carbon tax or state and federal incentives (scenario A), strategy I is marginally economical with 3% energy cost savings but with a 29% reduction in CO2 emissions. Strategy I is the most economical strategy for building owners in all scenarios (scenarios A–D) and, at the same time, reasonably achieves other goals of large GHG emission reductions and high FCS manufacturer sales revenue. Although no particular building type stands out as consistently achieving the highest emission reductions and cost savings (scenarios B-2 and E-2), certain building load curves are clear winners. For example, buildings with load curves similar to Stanford’s Mudd chemistry building (a wet laboratory) achieve maximal cost savings (1.5% with full federal and state incentives but no carbon tax) and maximal CO2 emission reductions (32%) (scenarios B-2 and E-2). Finally, based on these results, this work makes recommendations for reducing GHG further through FCS deployment. (Part I of II articles discusses the motivation and key assumptions behind the MERESS model development.)

Fuel Cell Development and Demonstrations in Australia

This paper focuses primarily on three significant fuel cell projects: the 200kW phosphoric acid fuel cell system demonstration carried out between 1998 and 2001 at the Australian Technology Park in Sydney, the Perth Hydrogen Fuel Cell Bus trial started in September 2004, the Ceramic Fuel Cells Ltd, the only fuel cell company in Australia and world competitive in developing and commercialising planar solid oxide fuel cell technology.

Evaluating low-temperature fuel cell performance for power generation: fluid dynamics study of phosphoric acid fuel cell systems at the cell level

The development of a detailed mathematical modelling approach for phosphoric acid fuel cells (PAFCs) is described and typical results are presented, discussed, and compared with experimental data found in the literature. A three-dimensional, integrated electrochemical computational-fluid dynamic analysis of a steady-state operation was attempted. The developed model was applied for validation purposes to a specific electrochemical system found in the literature; however, it can be applied to a variety of fuel cell systems. The model has been applied to investigate the effects of various parameters on system performance, justifying the claim that such studies can be very useful tools for optimizing the operation of a PAFC unit or stack. The predictions obtained of the average cell and stack voltage as well as of the generated power show good agreement with the limited experimental data found in the literature.

Wood-fired fuel cells in selected buildings

The positive attributes of fuel cells for high efficiency power generation at any scale and of biomass as a renewable energy source which is not intermittent, location-dependent or very difficult to store, suggest that a combined heat and power (CHP) system consisting of a fuel cell integrated with a wood gasifier (FCIWG) may offer a combination for delivering heat and electricity cleanly and efficiently. Phosphoric acid fuel cell (PAFC) systems, fuelled by natural gas, have already been used in a range of CHP applications in urban settings. Some of these applications are examined here using integrated biomass gasification/fuel cell systems in CHP configurations. Five building systems, which have different energy demand profiles, are assessed. These are a hospital, a hotel, a leisure centre, a multi-residential community and a university hall of residence. Heat and electricity use profiles for typical examples of these buildings were obtained and the FCIWG system was scaled to the power demand. The FCIWG system was modelled for two different types of fuel cell, the molten carbonate and the phosphoric acid. In each case an oxygen-fired gasification system is proposed, in order to eliminate the need for a methane reformer. Technical, environmental and economic analyses of each version were made, using the ECLIPSE process simulation package. Since fuel cell lifetimes are not yet precisely known, economics for a range of fuel cell lifetimes have been produced. The wood-fired PAFC system was found to have low electrical efficiency (13–16%), but much of the heat could be recovered, so that the overall efficiency was 64–67%, suitable where high heat/electricity values are required. The wood-fired molten carbonate fuel cell (MCFC) system was found to be quite efficient for electricity generation (24–27%), with an overall energy efficiency of 60–63%. The expected capital costs of both systems would currently make them uncompetitive for general use, but the specific features of selected buildings in rural areas, with regard to the high cost of importing other fuel, and/or lack of grid electricity, could still make these systems attractive options. Any economic analysis of these systems is beset with severe difficulties. Capital costs of the major system components are not known with any great precision. However, a guideline assessment of the payback period for such CHP systems was made. When the best available capital costs for system components were used, most of these systems were found to have unacceptably long payback periods, particularly where the fuel cell lifetimes are short, but the larger systems show the potential for a reasonable economic return.

Energy saving system using by-product hydrogen

The authors in conjunction with Shikoku Electric Power and Toagosei have been developing a new energy saving system using by-product hydrogen assisted by the Agency of Industrial Science and Technology (AISI) of the Ministry of International Trade and Industry (MITI) since 1993. The main unit of the system is a 100-kW class phosphoric acid fuel cell (PAFC) utilizing by-product hydrogen. The development technology of this hydrogen PAFC system include the following items; (1) recycling technology for using unreacted exhaust hydrogen at the anode outlet (2) safe processing technology of exhaust hydrogen. The system was constructed at the Tokushima plant of Toagosei and has operated from December 1996. The total operating time reached over 3000 h as of June 1997. The demonstration test will be conducted from 1996 through FY 1998.

Investigation on Waste Heat Recovery of Fuel Cell Stack Cooling System. 1st Report. Proposition of Simple Dynamic Model of Steam Heat Recovery on Fuel Cell Stack Cooling System.

Waste heat recovery of the fuel cell stack cooling system is very important from the viewpoint of effective use of energy. Simultaneously, temperature control of the fuel cell stack is necessary to maintain high electrical efficiency and to prevent the cell stack from oxidation. In phosphoric acid fuel cell system, coolant temperature is controlled to keep constant the temperature of cell stack. The purpose of this paper is to propose the simple dynamic model for designing the temperature control system and heat recovery system of fuel cell stack cooling system. In addtion to this, experimental research and simulation analysis reveal the dynamic characteristics of fuel cell stack cooling system with control equipments. Throughout the researches, concentrated parameter dynamic model is proposed and the validity of the model is confirmed by experimental results. When the transient response to disturbances such as make-up water pump start up is calculated, it is clarified that the coolant temperature of fuel cell stack can be controlled.

97/02004 Issues in fuel cell commercialization

Abstract After 25 years of effort, the phosphoric acid fuel cell (PAFC) is approaching commercialization as cell stack assemblies (CAS) show convincingly low degradation and its balance-of-plant (BOP) achieves mature reliability. A high present capital cost resulting from limited cumulative production remains an issue. The primary PAFC developer in the USA (International Fuel Cells, IFC) has only manufactured 40 MW of PAFC components to date, the equivalent of a single large gas turbine aero-engine or 500 compact car engines. The system is therefore still far up the production learning curve. Even so, the next generation of on-site 40% electrical efficiency (LHV) combined heat-and-power (CHP) PAFC system was available for order from IFC in 1995 at US$ 3000/kW (1995). To effectively compete in the marketplace with diesel generators, the dispersed cogeneration PAFC must cost approximately US$ 1550/kW (1995) in the USA and Europe. At somewhat lower costs than this, dispersed cogeneration PAFCs will compete with large combined-cycle generators. However, in Japan, costs greater than US$ 2000/kW will be competitive, based on the late-1995 trade exchange rate of 100–105 Yen/US $). The perceived advantages of fuel cell technologies over developments of more conventional generators (e.g., ultra-low emissions, siting) are not strong selling points in the marketplace. The ultimate criterion is cost. Cost reduction is now the key to market penetration. This must include reduced installation costs, for which the present goal is US$ 385/kW (1995). How further capital cost reductions can be achieved by the year 2000 is discussed. Progress to date is reviewed, and the potential for pressurized electric utility PAFC units is determined. Markets for high-temperature fuel cell system (molten carbonate, MCFC, and solid oxide, SOFC), which many consider to be 20 and 30 years, respectively, behind the PAFC, are discussed. Their high efficiency and high-quality waste heat should make them attractive if technical progress and costs are acceptable. Commercialization of the proton-exchange membrane fuel cell (PEMFC) system is considered for stationary and mobile applications.

Issues in fuel cell commercialization

After 25 years of effort, the phosphoric acid fuel cell (PAFC) is approaching commercialization as cell stack assemblies (CAS) show convincingly low degradation and its balance-of-plant (BOP) achieves mature reliability. A high present capital cost resulting from limited cumulative production remains an issue. The primary PAFC developer in the USA (International Fuel Cells, IFC) has only manufactured 40 MW of PAFC components to date, the equivalent of a single large gas turbine aero-engine or 500 compact car engines. The system is therefore still far up the production learning curve. Even so, the next generation of on-site 40% electrical efficiency (LHV) combined heat-and-power (CHP) PAFC system was available for order from IFC in 1995 at US$ 3000/kW (1995). To effectively compete in the marketplace with diesel generators, the dispersed cogeneration PAFC must cost approximately US$ 1550/kW (1995) in the USA and Europe. At somewhat lower costs than this, dispersed cogeneration PAFCs will compete with large combined-cycle generators. However, in Japan, costs greater than US$ 2000/kW will be competitive, based on the late-1995 trade exchange rate of 100–105 Yen/US $). The perceived advantages of fuel cell technologies over developments of more conventional generators (e.g., ultra-low emissions, siting) are not strong selling points in the marketplace. The ultimate criterion is cost. Cost reduction is now the key to market penetration. This must include reduced installation costs, for which the present goal is US$ 385/kW (1995). How further capital cost reductions can be achieved by the year 2000 is discussed. Progress to date is reviewed, and the potential for pressurized electric utility PAFC units is determined. Markets for high-temperature fuel cell system (molten carbonate, MCFC, and solid oxide, SOFC), which many consider to be 20 and 30 years, respectively, behind the PAFC, are discussed. Their high efficiency and high-quality waste heat should make them attractive if technical progress and costs are acceptable. Commercialization of the proton-exchange membrane fuel cell (PEMFC) system is considered for stationary and mobile applications.

Electrical characterization of a 2.5 kW phosphoric acid fuel cell stack operating on simulated reformed biogas

An air-cooled 2.5 kW phosphoric acid fuel cell (PAFC) stack manufactured by Energy Research Corp., Danbury, CT, was fueled by dry simulated reformed biogas, and its steady-state electrical characteristics were determined. The energy-conversion efficiency was also determined and compared with the efficiency of the same stack operating on a gas mixture corresponding to that of reformed methanol or reformed natural gas. It is shown that PAFC systems can be efficiently applied to electrical load-following using abundant biomass-derived fuels in remote areas.

A phosphoric acid fuel cell coupled with biogas

During the last decade, advances in phosphoric acid fuel cell (PAFC) technology have brought this system almost to commercial status. The PAFC systems are intended for use with oxygen from ambient air and relatively clean hydrogen from reformed fuels such as light distillates, methanol and natural gas. In this paper, the techno-economic feasibility of a PAFC coupled with biogas is examined. Mass and energy balances for the system have been computed. It is shown that the PAFC stack price should be <$1000/kW to produce electricity at a price comparable to supply from the grid or other on-site options.

1. Summary of research recommendations

An overview of the phosphoric acid fuel cell (PAFC) technology is provided in this chapter. The various components that are part of PAFC stack and the working principles behind the PAFC are described in detail. The various fuels that can be used are discussed. Efficiency and performance considerations are important for any energy conversion technology. Achievable power densities and system efficiencies when using PAFC technology are outlined. The lifetime of fuel cell stacks is a critical factor in fuel cell commercialization. While PAFC stacks have demonstrated large lifetimes (greater than 40,000 h), there are still several challenges that need to be addressed before such reliability becomes routinely achievable. Various performance loss mechanisms are described in detail. The state-of-the-art in modeling of PAFC systems is explored, in brief. The advantages and disadvantages of PAFCs when compared with other fuel cell technology are described at appropriate locations. The chapter concludes with a discussion on the future prospects for the PAFC technology.

Coal gas as a feed fuel for phosphoric acid fuel cell power plants

Westinghouse Electric Corporation has assessed the effects of a number of coal gasification systems and their gas compositions on a 7.5 MW (c) dc Phosphoric Acid Fuel Cell (PAFC) power plant. Both low and medium BTU synthesis gases were considered from various promising gasification processes. Degree of development or commercialization, technical complexity, availability and coal restrictions were taken into account. System studies performed on the 7.5 MW (c) dc PAFC power plant for nonintegrated and integrated fuel conditioning systems are discussed for the various gasification processes. In all cases coal gas was assumed to be purchased “over-the-fence”. Representative characteristics for the derived coal gases and PAFC system performance data are presented. The direct capital costs of the PAFC power plant are evaluated for each system.