Cell stack subsystem

J2617. Performanee Test Proeedures of PEM Fuel Cell Stack Subsystem for Automotive Applications (final draft)... 

High temperature fuel cell stacks and materials Currently, UK companies are active at the short stack and subsystem level. For the longer term the industry expects to build on this materials research strength to provide competitive advantage through enhanced performance and lower costs. 

The critical technology development areas are advanced materials, manufacturing techniques, and other advancements that will lower costs, increase durability, and improve reliability and performance for all fuel cell systems and applications. These activities need to address not only core fuel cell stack issues but also balance of plant (BOP) subsystems such as fuel processors hydrogen production, delivery, and storage power electronics sensors and controls air handling equipment and heat exchangers. Research and development areas include ... 

While different developers are addressing improvements in individual components and subsystems in automotive fuel cell propulsion systems (e.g., cells, stacks, fuel processors, balance-of-plant components), we are using modeling and analysis to address issues of thermal and water management, design-point and part-load operation, and component-, system-, and vehicle-level eificiencies and fuel economies. Such analyses are essential for effective system integration. 

Nuvera will design, build, test, and deliver a 15 kilowatt electrical (kWe ) direct current (DC) fuel cell power module that will be specifically designed for stationary power operation using ethanol as a primary fuel. Two PEM fuel cell stacks in parallel will produce 250 amps and 60 volts at rated power. The power module will consist of a fuel processor, carbon monoxide (CO) clean-up, fuel cell, air, fuel, water, and anode exhaust gas management subsystems. A state-of-the-art control system will interface with the power system controller and will control the fuel cell power module under start-up, steady-state, transient, and shutdown operation. Temperature, pressure, and flow sensors will be incorporated in the power module to monitor and control the key system variables under these various operating modes. The power module subsystem will be tested at Nuvera and subsequently be delivered to the Williams Bio-Energy Pekin, Illinois site. 

Research, develop, assemble, and test a 50 kW net polymer electrolyte membrane (PEM) fuel cell stack system comprised of a PEM fuel cell stack and the supporting gas, thermal, and water management subsystems. The PEM fuel cell stack system will be capable of integration with at least one of the fuel processors currently under development by Hydrogen Burner Technology (HBT) and Arthur D. Little, Inc. 

The PEM fuel cell stack system consists of the fuel cell stack and supporting gas, thermal and water management systems as shown in Figure 1. Overall system performance depends on the careful integration of these subsystems. The system developed under this contract was designed to accept reformed gasoline from a fuel processor. Development of the fuel processor was not part of this program. 

Naturally, for more powerful fuel cell systems (1-100 kW) such as developed for the power train of cars, the passive approach of the low power systems is not feasible. Powerful systems require fuel cell stacks with power densities of the order of lkWkg to be competitive with internal combustion engines. In such stacks active areas of several hundred square centimeters with current densities of over 1 Acm are required. This leads to the need for forced air supply by a blower or compressor and also for very efficient heat removal as the heat load to be removed is also in the order of 1W cm of active area. Therefore, the complexity of such fuel cell systems increases considerably. Generally, at least four subsystems complementing the fuel cell stack are required ... 

Fuel subsystem, including tank for hydrogen, piping, valves and controls to deliver the hydrogen fuel at the required pressure mass flow and humidity to the fuel cell stack. 

Air supply subsystem, including blower or compressor, air humidification, heat exchanger and pressure control devices to deliver process air at the required mass flow, pressure temperature and humidity to the fuel cell stack. Separation of water from the used air stream and, in some cases, an expander add more complexity to the air supply subsystem ... 

Cooling subsystem, including pump, heat exchanger and conductivity control for the coolant. In mobile systems the heat is dumped unused into the ambient air, in the case of stationary systems, the waste heat of the fuel cell stack can be used or distributed. 

MW, GT power of 6.1 MW, and parasitic power of 1.4 MW). The key operating parameter assumptions for the SOFC in this case are 0.7 V cell voltage, 70% one-pass FU, 100°C temperature rise, and 5 atm pressure. The optimal number of stacks and the stack size are determined for this system using an approach to examine stack size effects on the performance, cost, and reliability of the system. In this case, a cell diameter of 45.7 cm is chosen based on system cost and reliability projections [26]. From stack cost optimization and PE subsystem loss studies, the optimal SOFC stack configuration for this 25 MW hybrid has 400 cells 45.7 cm in diameter. Assuming a ceU power density of 0.5 Wcm, this SOFC stack size translates into a 320 kW stack power. Given the 20 MW total SOFC stack subsystem power requirement, a minimum of 62 stacks is required to construct the 25 MW hybrid plant... 

The combination of a fuel cell stack and the subsystems that are required to support its operation for the intended... 

The parallel system configuration shows two thermal oil subsystems, a low temperature (160-180 °C) and a high temperature (300 °C) subsystem. The low temperature subsystem includes the fuel cell stack, the evaporator for... 

Of interest is the view that the majority of the cost is dominated by the fuel cell stack and the fuel processing subsystems. Further, the primary cost reduction for smaller SOFC units will stem from improvements to the fuel cell subsystem, whilst cost reductions for the fuel processing system will be difficult balance of plant component costs reduction opportunities, such as compressors, pumps, sensors and heat exchangers, are considered to be fairly small. Similarly, other subsystems such as power electronics are considered fairly stable cost wise. 

This zinc/air battery consisted of modular cell stacks, each containing a series of individual bicells. Each bicell consists of an anode cassette containing a zinc-based electrolyte slurry, contained between air cathodes, and a separator system. The slurry is maintained in a static bed without circulation. In addition, the battery contains subsystems for air provision and heat management and is adapted for fast mechanical replacement of the cassettes. 

Table 10.1 shows variations in gas consumption rates, water production rate, and heat generation rate for different fuel cell stack power. As we can see, with increased power level, subsystems such as air and fuel delivery system, and water and heat management systems also scale up in size and complexity. 

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