Phosphoric acid fuel cell PAFC

Similar to PEMFCs, this cell operates in the middle temperature range at around 200°C. This means it can tolerate some impurities. It employs a phosphoric acid proton conducting electrolyte and platinum or platinum-rhodium electrodes. The main difference from a PEMFC is that it uses a liquid electrolyte.

The system efficiency is currently in the 37-43% range, but this is expected to improve. This technology seems particularly popular in Japan where electricity costs are high and dispersed generation is preferred. A 200 kW unit which uses sewage gas provides heat and power for Yokohama sewage works. The largest installation to date for the Tokyo Electric Power Company had an output of 11 megawatts until it finally expired.

PAFC units have been used experimentally in buses. However, it is likely that its future lies in stationary systems.

The New Scientist editorial referred to above predicts that 'Larger, static fuel cells will become attractive for hotels and sports centres, while power companies will use them as alternatives to extending the electricity grid'. An example of this is the police station in

Figure 7.4 Solid oxide fuel cell (SOFC) in its tubular configuration

Central Park, New York, which found that installing a PAFC of 200 kW capacity was cheaper than a grid connection requiring new cables in the park. One year after this prediction the Borough of Woking, Surrey, UK installed the first commercial PAFC fuel cell to operate in the UK. It also has a capacity of 200 kW and is providing heat, cooling, light and dehumidification for the Pool in the Park recreation centre. The fuel cell forms part of Working Park's larger combined heat and power system.

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