Meeting the challenges in the transport sector

This paper provides an industry leader's perspectives on the potential for transportation fuel cells, reviewing their development progress, describing their advantages and barriers, and identifying paths to successful commercial deployment. UTC Power has developed proton exchange membrane (PEM) fuel cell technology for transportation since 1998, building upon applicable innovations from the company's space fuel cell and stationary fuel cell programs. PEM fuel cell durability improvements are discussed, highlighting achievements in the understanding of decay mechanisms and the design of effective mitigations. The potential for high-volume production to make automotive fuel cells cost competitive with internal combustion engines is explained. The paper underscores the important role that initial deployment of PEM technology for transit buses can play, although development of automotive fuel cells must continue in parallel as the hydrogen infrastructure develops. Suggestions are offered on how policies and regulations, communication and education, and improved codes and standards can all help to promote the widespread use of fuel cells in transportation.     

Exergoeconomic analysis of a vehicular PEM fuel cell system

In this study, we deal with the exergoeconomic analysis of a proton exchange membrane (PEM) fuel cell power system for transportation applications. The PEM fuel cell performance model, that is the polarization curve, is previously developed by one of the authors by using the some derived and developed equations in literature. The exergoeconomic analysis includes the PEM fuel cell stack and system components as compressor, humidifiers, pressure regulator and the cooling system. A parametric study is also conducted to investigate the system performance and cost behaviour of the components, depending on the operating temperature, operating pressure, membrane thickness, anode stoichiometry and cathode stoichiometry. For the system performance, energy and exergy efficiencies and power output are investigated in detail. It is found that with an increase of temperature and pressure and a decrease of membrane thickness the system efficiency increases which leads to a decrease in the overall production cost. The minimization of the production costs is very crucial in commercialization of the fuel cells in transportation sector.     

An off-peak energy storage concept for electric utilities: Part I—Electric utility requirements

The water battery, a reversible water electrolyser device being developed in a long-term research effort at Battelle's Columbus Laboratories, was evaluated in an analytical and conceptual design study as a load-levelling system for an electric utility. During periods when off-peak electrical power was available, the water battery would produce hydrogen and oxygen by electrolysis of water; during peak demand periods the water battery would be operated in the reverse mode, functioning as a fuel cell by producing electrical power through the recombination of the oxygen and hydrogen held in its storage vessels.The analysis involved characterisation of the PSE&G system demand requirements now and in the future, its current off-peak energy availability, the typical sizing and placement of energy storage units and the approximate break even economics and potential advantages to the utility of a water battery energy storage system. In the economic analysis, the water battery was compared with the gas turbine and the fuel cell for cost effectiveness in meeting peak and intermediate power demands, respectively.Compared with a ‘reformer-type’ fuel cell (costed at $300/kW for intermediate duty) the break even capital cost of a 50% efficient water battery would be $100/kW plus about $200/kW for each increase of $1/10⁶ Btu above the reference cost of $1/10⁶ Btu for fossil fuel. The available margin would increase about $50/kW for each decrease of 1 mill/kWh in off-peak energy cost below the reference cost of 8 mills/kWh. In a similar comparison with the gas turbine (costed at $135/kW) for peaking duty, the break even cost of a 50% efficient water battery would be $100/kW. The break even cost could rise about $100/kW for each increase in fossil fuel cost of $1/10⁶ Btu and about $20/kW for each decrease in off-peak energy cost of 1 mill/kWh.     

Importance and applications of DOE/optimization methods in PEM fuel cells: A review

Although proton exchange membrane (PEM) fuel cells are seen as one of the energy conversion technologies of the future due to their high energy conversion efficiency, low levels of emissions, low temperature operation, and compact systems, studies continue to reduce their cost, which is the biggest obstacle to commercialization. Design of experiment (DOE) methods are frequently used in optimization of PEM fuel cells to reduce their cost by decreasing experimental runs. This paper reviews the main gains subsuming the usage of several DOE and optimization methods in PEM fuel cell components, design, operation conditions, and model parameters. It firstly focuses on the Taguchi method and response surface methodology (RSM) known to be applied usually in PEM fuel cell studies. In addition to these known methods, other experimental design and optimization methods used in PEM fuel cells are discussed, and the results are summarized.     

A comprehensive assessment on the durability of gas diffusion electrode materials in PEM fuel cell stack

Polymer electrolyte membrane (PEM) fuel cell is the most promising among the various types of fuel cells. Though it has found its applications in numerous fields, the cost and durability are key barriers impeding the commercialization of PEM fuel cell stack. The crucial and expensive component involved in it is the gas diffusion electrode (GDE) and its degradation, which limits the performance and life of the fuel cell stack. A critical analysis and comprehensive understanding of the structural and functional properties of various materials involved in the GDE can help us to address the related durability and cost issues. This paper reviews the key GDE components, and in specific, the root causes influencing the durability. It also envisages the role of novel materials and provides a critical recommendation to improve the GDE durability.     

Challenges towards large-scale fuel cell production: Results of an expert assessment study

Fuel cell electric vehicles are a promising alternative on the way to emission-free mobility. However, there is still a great deal of uncertainty as to how this change can be implemented technologically. Despite various research and development activities on fuel cells in the past two decades, a real breakthrough of fuel cell technology has not yet been reached. The aim of this paper is therefore to identify barriers to a commercialized production of PEM fuel cell stacks. For this purpose, a comprehensive expert study is performed, consisting of a qualitative, exploratory and a quantitative, hypothesis-confirming step. As a result, technical and non-technical barriers are examined and described in this paper. A cost estimation of today's actual manufacturing cost is presented as identified in the study. Conclusively, future research topics and needs for action are derived.     

Technical design and economic evaluation of a PEM fuel cell system

The main objectives of this study are to develop the economic models and their characterization trends for the common unit processes and utilities in the fuel cell system. In this study, a proton electrolyte membrane fuel cell (PEMFC) system is taken as a case study. The overall system consists of five major units, namely auto-thermal reformer (ATR), water gas shift reactor (WGS), membrane, pressure swing adsorber (PSA) and fuel cell stack. Besides that, the process utilities like compressor, heat exchanger, water adsorber are also included in the system. From the result, it is determined that the specific cost of a PEM fuel cell stack is about US$ 500 per kW, while the specific manufacturing and capital investment costs are in the range of US$ 1200 per kW and US$ 2900 per kW, respectively. Besides that the electricity cost is calculated as US$ 0.04 kWh. The results also prove that the cost of PEM fuel cell system is comparable with other conventional internal engine.     

Exergy and exergo-economic investigation of a novel hydrogen production and storage system via an integrated energy system

The main purpose of the current research work is to suggest a novel integrated multi-generation energy system and scrutinize 4E evaluation. This system consists of a solid oxide fuel cell, a PEM electrolyzer for hydrogen production, and an ejector-based absorption chiller for the coefficient of performance improvement. All parts of this system are verified with existing reports and papers. Effect of fuel cell current density, SOFC fuel cell temperature, absorption chiller evaporator temperature, and condenser temperature, and outlet turbine pressure has been investigated and reported. The effect of mentioned parameters on the exergy and cost rate has been considered. Data illustrate that the maximum exergy destruction rate belongs to the SOFC contributing 60% of the total exergy destruction rate of the system. Under the given condition of the system, the net produced power is about 200 kW with an exergy efficiency of 30.2% and thermal efficiency of 60.4%. At the considered condition the total cost rate of the system is estimated about 22.29 $/hr. The results of the present work provide a scientific base for designing poly-generation systems with high efficiency and reasonable cost rate.     

Metal bipolar plates for PEM fuel cell—A review

The polymer electrolyte membrane (PEM) based fuel cells are clean alternative energy systems that hold excellent potential for cost effectiveness, durability, and relatively high overall efficiency. PEM fuel cell is recognized by the U.S. Department of Energy (DOE) as the main candidate to replace the internal combustion engine in transportation applications. Metallic bipolar plates and membrane electrode assembly (MEA) are two crucial components of a PEM power stack and their durability and fabrication cost must be optimized to allow fuel cells to penetrate the commercial market and compete with other energy sources.     

Technical cost analysis for PEM fuel cells

The present cost of fuel cells estimated at about $200 kW⁻¹ is a major barrier for commercialization and use in automotive applications. In the United States the target costs for fuel cell systems for the year 2004 as formulated by PNGV are $50 kW⁻¹. Lomax et al. have estimated the costs of polymer electrolyte membrane (PEM) fuel cells to be as low as $20 kW⁻¹. These estimates are based on careful consideration of high volume manufacturing processes. Recently, Arthur D. Little (ADL) has estimated the cost of a fuel cell system for transportation at $294 kW⁻¹. This estimate considers a fuel processor and directly related balance of plant components. The difference of the cost estimates results from the vastly different design assumptions. Both of these estimates are based on considering a single high volume of production, 500,000 fuel cells per year. This work builds on these earlier estimates by employing the methods of technical cost modeling and thereby including explicit consideration of design specifications, exogenous factor cost and processing and operational details. The bipolar plate is analyzed as a case study. The sensitivity of the costs to uncertainty in process conditions are explored following the ADL design. It is shown that the PNGV targets can only be achieved with design changes that reduce the quantity of material used. This might necessitate a reduction in efficiency from the assumed 80 mpg.     

Characterisation and modelling of a 5 kW PEMFC for transportation applications

In the framework of the French inter lab SPACT project (fuel cell systems for transportation applications), a 10 kW PEM fuel cell testing bench has been installed in 2002 in the national fuel cell test platform located in Belfort, France. The behaviour of a 5 kW fuel cell, fed with humidified pure hydrogen gas and compressed air, has been investigated by the Laboratory of Electrical Engineering and Systems (L2ES) in association with the French National Institute for Transport and Safety Research (INRETS).     

Technology learning for fuel cells: An assessment of past and potential cost reductions

Fuel cells have gained considerable interest as a means to efficiently convert the energy stored in gases like hydrogen and methane into electricity. Further developing fuel cells in order to reach cost, safety and reliability levels at which their widespread use becomes feasible is an essential prerequisite for the potential establishment of a ‘hydrogen economy’. A major factor currently obviating the extensive use of fuel cells is their relatively high costs. At present we estimate these at about 1100 €(2005)/kW for an 80 kW fuel cell system but notice that specific costs vary markedly with fuel cell system power capacity. We analyze past fuel cell cost reductions for both individual manufacturers and the global market. We determine learning curves, with fairly high uncertainty ranges, for three different types of fuel cell technology – AFC, PAFC and PEMFC – each manufactured by a different producer. For PEMFC technology we also calculate a global learning curve, characterised by a learning rate of 21% with an error margin of 4%. Given their respective uncertainties, this global learning rate value is in agreement with those we find for different manufacturers. In contrast to some other new energy technologies, R&D still plays a major role in today’s fuel cell improvement process and hence probably explains a substantial part of our observed cost reductions. The remaining share of these cost reductions derives from learning-by-doing proper. Since learning-by-doing usually involves a learning rate of typically 20%, the residual value for pure learning we find for fuel cells is relatively low. In an ideal scenario for fuel cell technology we estimate a bottom-line for specific (80 kW system) manufacturing costs of 95 €(2005)/kW. Although learning curves observed in the past constitute no guarantee for sustained cost reductions in the future, when we assume global total learning at the pace calculated here as the only cost reduction mechanism, this ultimate cost figure is reached after a large-scale deployment about 10 times doubled with respect to the cumulative installed fuel cell capacity to date.     

Reforming options for hydrogen production from fossil fuels for PEM fuel cells

PEM fuel cell systems are considered as a sustainable option for the future transport sector in the future. There is great interest in converting current hydrocarbon based transportation fuels into hydrogen rich gases acceptable by PEM fuel cells on-board of vehicles. In this paper, we compare the results of our simulation studies for 100 kW PEM fuel cell systems utilizing three different major reforming technologies, namely steam reforming (SREF), partial oxidation (POX) and autothermal reforming (ATR). Natural gas, gasoline and diesel are the selected hydrocarbon fuels. It is desired to investigate the effect of the selected fuel reforming options on the overall fuel cell system efficiency, which depends on the fuel processing, PEM fuel cell and auxiliary system efficiencies. The Aspen-HYSYS 3.1 code has been used for simulation purposes. Process parameters of fuel preparation steps have been determined considering the limitations set by the catalysts and hydrocarbons involved. Results indicate that fuel properties, fuel processing system and its operation parameters, and PEM fuel cell characteristics all affect the overall system efficiencies. Steam reforming appears as the most efficient fuel preparation option for all investigated fuels. Natural gas with steam reforming shows the highest fuel cell system efficiency. Good heat integration within the fuel cell system is absolutely necessary to achieve acceptable overall system efficiencies.     

Alkaline falling-film fuel cell A breakthrough in technology and cost

The work described in this paper was oriented towards fuel cells for practical applications, but mainly presents data obtained using half-cells. The economic significance of these data is discussed, together with the technical concept of fuel cell power stations and for transportation applications. The proposed fuel cell with generate power at much lower costs than conventional power plants, and a zero-emission vehicle with fuel cells will operate at lower fuel cost than a car with an internal combustion engine. The simple falling-film process leads to high power densities (6 kW/l) and low cost. The details given are valid for the use of hydrogen produced from fossil energy sources. Concentrated CO₂, a byproduct of this technology can be stored in discussed oil and gas fields at a very low cost to avoid global warming. Thus, this ‘down-to-earth’ hydrogen technology is a free from CO₂ emissions as solar-hydrogen technology.     

Highly stable Pt and PtPd hybrid catalysts supported on a nitrogen-modified carbon composite for fuel cell application

The durability and cost of fuel cell cathode catalysts are major technical barriers to the commercialization of fuel cells for vehicle applications. In this work, novel Pt and PtPd hybrid catalysts are developed that use a nitrogen-modified carbon composite (NMCC), which is itself active for the oxygen reduction reaction (ORR), instead of a conventional carbon black support. The fuel cell accelerated stress test (AST) for supports and catalysts demonstrated that the Pt₃Pd₁/NMCC and Pt/NMCC hybrid catalysts possess much higher stability than Pt/C catalysts in polymer electrolyte membrane (PEM) fuel cells. Moreover, the hybrid catalysts exhibit higher mass activity than the Pt/C catalysts. The origin of the hybrid catalysts’ improved performance relative to Pt/C is discussed in light of pore size distribution and surface area analysis, XRD, XPS, and TEM analyses and electrochemical measurements.     

Performance improvement of a heat recovery system combined with fuel cell and thermoelectric generator: 4E analysis

In the present work, the performance improvement of a waste heat recovery system is investigated by applying a fuel cell and thermoelectric generator. With the use of energy, exergy, exergo-economic, and environmental analyses (4E analysis), the performance of the improved system is evaluated. A mathematical simulation in the Engineering Equation Solver (EES) is developed for basic and modified systems. Comparative analysis is carried out to demonstrate the benefit of the suggested system. The logical and correct combination of appropriate subsystems can lead to the maximum exploitation of an energy source, which is the innovation of the present work. The comparison of suggested system (PR/FC-TEG) with the CHP system indicates that the net output power of the PR/FC-TEG system is 3881 kW compared with 958.4 kW for the CHP system. However adding fuel cell to the PR/FC-TEG system increase output power by about 2162 kW, and it imposes 4823 kW exergy destruction rate to the system. The exergy destruction rate of the PEM FC, regenerator, and vapor generator are about 88.96% of the total exergy destruction rate, which infers the importance of these components in the PR/FC-TEG system improvement. Parametric analysis on the PR/FC-TEG performance with changing four influencing parameters is performed. Results indicate that increasing the turbine 1 inlet temperature by about 1.1% increases the cost of generated electricity from 72.92 to 73.88 $/GJ and decreases the sustainability index from 1.68 to 1.65. The multi-objective optimization of the developed system can be a promising option for future study.     

Techno-economic study of off-grid hybrid photovoltaic/battery and photovoltaic/battery/fuel cell power systems in Kunming,China

The objective of this study is to evaluate the technical and economic feasibility of stand-alone hybrid photovoltaic (PV)/battery and PV/battery/fuel cell (FC) power systems for a community center comprising 100 households in Kunming by using the Hybrid Optimization Model for Electric Renewable (HOMER) software. HOMER is used to define the optimum sizing and techno-economic feasibility of the system equipment based on the geographical and meteorological data of the study region. In this study, different hybrid power systems are analyzed to select the optimum energy system while considering total net present cost (NPC) and levelized cost of energy (COE). The results showed that the optimal hybrid PV/battery system comprised 500 kW PV modules, 1200 7.6-kWh battery units, and 500 kW power converters. The proposed system has an initial cost of $6,670,000, an annual operating cost of $82,763/yr, a total NPC of $7,727,992, and a levelized COE of $1.536/kWh. While the PV/battery/FC power system is possible, the cost increases were due to the investment cost of the FC system. The optimal PV/battery/FC system has an initial cost of $6,763,000, an annual operating cost of $82,312/yr, a total NPC of $7,815,223, and a levelized COE of $1.553/kWh.     

A review of solid oxide fuel cell component fabrication methods toward lowering temperature

The solid oxide fuel cells (SOFCs) emerge as an alternative power generation system for high-scale stationary application and power plant station. The SOFC consumption leads to the high-efficiency energy production that forms variety of fuels up to 60% energy conversion; the operation system does not involve the burning process and minimizes the air pollution. Also, the aptitude to provide the cogenerative energy production from the heat waste during the operation process serve SOFC as an attractive green technology and environmentally friendly. However, the SOFC consumption remains limited for transportation and portable applications because the simple design of power source compartment is still the major hurdle in each SOFC component development and commercialization. Therefore, the appropriate fabrication method of each SOFC component is important to achieve the reliability of the SOFC application for the small-scale power generation design. In this paper, an overview of the design types and SOFC components and properties following electrode, electrolyte, interconnect and sealant are discussed and summarized. As the third-generation fuel cells, which entice the commercialization stage, this paper concentrates more on the fabrication method of each SOFC components that were explored including the working principle, advantage, disadvantage and several previous works on each fabrication method, which are described to finding the appropriate fabrication method toward lowering the operating temperature and develop the simple design of SOFC power sources system for the transportation and portable application. The targeted market power production of SOFC system for transportation application is about 5 kW and 250 W for portable application.     

Hydrogen as a long-term,large-scale energy storage solution when coupled with renewable energy sources or grids with dynamic electricity pricing schemes

One of the key challenges that still facing the adoption of renewable energy systems is having a powerful energy storage system (ESS) that can store energy at peak production periods and return it back when the demand exceeds the supply. In this paper, we discuss the costs associated with storing excess energy from power grids in the form of hydrogen using proton exchange membrane (PEM) reversible fuel cells (RFC). The PEM-RFC system is designed to have dual functions: (1) to use electricity from the wholesale electricity market when the wholesale price reaches low competitive values, use it to produce hydrogen and then convert it back to electricity when the prices are competitive, and (2) to produce hydrogen at low costs to be used in other applications such as a fuel for fuel cell electric vehicles. The main goal of the model is to minimize the levelized cost of energy storage (LCOS), thus the LCOS is used as the key measure for evaluating this economic point. LCOS in many regions in United States can reach competitive costs, for example lowest LCOS can reach 16.4¢/kWh in Illinois (MISO trading hub) when the threshold wholesale electricity price is set at $25/MWh, and 19.9¢/kWh in Texas (ERCOT trading hub) at threshold price of $20/MWh. Similarly, the levelized cost of hydrogen production shows that hydrogen can be produced at very competitive costs, for example the levelized cost of hydrogen production can reach $2.54/kg-H₂ when using electricity from MISO hub. This value is close to the target set by the U.S. Department of Energy.     

Two strategies for multi-objective optimisation of solid oxide fuel cell stacks

This paper focuses on multi-objective optimisation (MOO) to optimise the planar solid oxide fuel cell (SOFC) stacks performance using a genetic algorithm. MOO problem does not have a single solution, but a complete Pareto curve, which involves the optional representation of possible compromise solutions. Here, two pairs of different objectives are considered as distinguished strategies. Optimisation of the first strategy predicts a maximum power output of 108.33 kW at a breakeven per-unit energy cost of 0.51 $/kWh and minimum breakeven per-unit energy cost of 0.30 $/kWh at a power of 42.18 kW. In the second strategy, maximum efficiency of 63.93%at a breakeven per-unit energy cost of 0.42 $/kWh is predicted, while minimum breakeven per-unit energy cost of 0.25 $/kWh at efficiency of 48.3% is obtained. The present study creates the basis for selecting optimal operating conditions of SOFC under the face of multiple conflicting objectives.