A phosphoric acid fuel cell cogeneration system retrofit to a large office building

A fuel cell based cogeneration system retrofit to a large office building in Pittsburgh, USA, has been designed and its technical and economic performance, evaluated. The present heating, ventilation and air conditioning (HVAC) system was considered and the power, heating and cooling requirements of the building over the period of a year were characterized in detail. Five cogeneration systems have been studied. These systems were designed to meet either the peak, average or base electrical loads of the building. The peak and average load systems were designed with and without absorption refrigeration equipment for air conditioning. The average load system included battery storage so that the system might provide for the daily electric demand profile of the building. All the cogeneration systems were based on the commercially available ONSI PC25C, phosphoric acid fuel cell (PAFC) unit. They all made use of the existing water based, hydronic, heating and cooling arrangements and heat rejection equipment of the building. They also used the current natural gas fired water heaters, the electric motor driven vapor compression chillers and electric domestic water heaters as auxiliary equipment. Annual energy requirements and costs were calculated for each of the five cogeneration systems. These energy quantities and costs were compared with those for the current, conventional building operation. The calculated cost savings were then used to estimate the economically justified capital cost of the fuel cell power generation units based on a desired rate and period of return.