Fuel cell power plants design specifications

Electric Power System Design For specific applications, fuel cells can be used to supply DC power distribution systems designed to feed DC drives such as motors or solenoids, controls, and other auxiliary system equipment. The goal of the commercial fuel cell power plant is to deliver usable AC power to an electrical distribution system. This goal is accomplished through a subsystem that has the capability to deliver the real power (watts) and reactive power (VARS) to a facility s internal power distribution system or to a utility s grid. The power conditioning... 

The efficiency of the total fuel cell system can be calculated by accounting for the generation efficiency of the fuel cell stack, the efficiency of power conversion devices, and the accessory load of the related subsystems. In order to obtain the best overall fuel cell power system efficiency and better economics, a system optimization is required. The optimization involves minimizing the cost of electricity or heat and electric products as in a cogeneration system all the component processes of the system should be integrated into an efficient plant with low capital cost. Often, these objectives are conflicting, so compromises, or design decisions, have to be made. In addition, project-specific objectives, such as desired fuel, environmental emission levels, potential uses of rejected heat, desired output levels, volume (volume/kW)... 

This shows that all these systems have already left the experimental R D stage and become an economic reality. They have already demonstrated lower consumption of natural fossil fuels per unit of power generated and lower emission of greenhouse gases and other harmful products. Other advantages over thermal power plants are associated with fuel cell-based power plants. They can be produced in modules, from which power plants of different size and output can be put together. This attribute, known as scalability, facilitates the design and construction of plants adapted to specific local requirements. 

Oak Ridge National Laboratory (ORNL) has developed a carbon fiber composite molecular sieve designed specifically to absorb CO2 emitted from coal fired power plants and gas turbines. Petroleum pitch based chopped fiber is bonded with a phenolic resin and activated in steam, O2, or CO2 at 850°C, to form a product with a large surface area and pore volume with mesopores of 2 50 nm, capable of absorbing CO2. There are also macropores (50 100 pm) which allow sufficient fluid flow with low pressure drop. It also has potential to be used for removal of CO2 from natural gas for fuel cells. [25]. 

Specific details of the design are listed in Table 4. The most electrically efficient (highest cell potential) will be that of the highest cell area (lowest current density). For a 200 V stack voltage, a current of 500 A is needed to produce 100 kWe. At the maximum cell area of 900 cm, the current density is 0.556 A/cm, which then locates point A on the polarization curve of Fig. 3. The potential at this point is 0.75 V, and therefore 267 cells are required to achieve 200 V. With an assumed cell thickness of 0.3 cm, the stack volume is 72.03 1, thus giving a power density of 1.39 kWe/1 and a fuel cell plant cost of 7,203 according to Eq. 23 and TCI of 28,813 by Eqs. 22 and 24. 

Argonne National Laboratory developed the General Computational Toolkit (GCTool) specifically for designing, analyzing, and comparing fuel cell systems and other power plant... 

During the next two decades, some decline of interest in fuel cells can be noted, and fewer studies appeared in this field. Technical and design improvements were introduced into models of the AFC, MCFC, and SOFC systems, and some large power plants were built. The basic structure of fuel cells themselves (compositiou of electrodes and electrolyte) and also the specific performance figures (per unit surface area of the electrodes) changed little during this time. 

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