Abstract
NTT is developing a phosphoric-acid fuel-cell energy system for telecommunication co-generation systems to reduce energy costs and help preserve the environment. Fuel cells are used to provide electrical power to telecommunication equipment and the heat energy that is generated is used by the absorption refrigerators to cool the telecommunication rooms throughout the year. We fieldtested this fuel-cell energy system in a telephone office. Two heat recovery methods were applied in the test: one uses direct steam heat recovery from fuel-cell stack coolant to keep the heat recovery temperature high and to avoid requiring a heat exchanger for the recovery; the other uses heat recovery from the reformer exhaust gas that is directly in contact with the heat recovery water to recover heat more economically. Our field tests confirmed that the average efficiency of heat recovery from fuel-cell stack coolant is 16%, and from the reformer exhaust gas is 9% under 80-kW continuous operation. Maximum total efficiency including electrical power efficiency was comfirmed to be about 73% under the condition of 100-kW and an S/C ratio of 2.5 in the winter period: heat recovery from the fuel-cell stack coolant was 23%, from the reformer exhaust gas was 10%, and from electrical conversion was about 40%.
