Improving Performance of Refrigerant Cooled Steam Power Plant by Using Cooling Thermal Storage

Abstract

It is proposed in the current paper to combine the steam plant with two refrigeration cycles and a cooling storage container. Throughout the time of a day, the steam plant is made to work at full power, where the excess power generated over the electric power demand is used to drive the compressors of the refrigeration cycles. The stored cooling is used for dissipating the heat absorbed by the cooling refrigerant in the steam condenser during the period of peak-loads, while the two refrigeration machines are stopped. In this way, the energy used for driving the refrigeration machine is saved so that the whole power generated by the steam plant is exported to the grid. Energy analyses of the proposed combined system has led to inferring that the net power of the steam plant during the period of exclusive direct cooling of the steam condenser (only the first refrigeration machine is running) is about 70–86% of the whole power generated by the steam plant when the coefficient of performance of the first refrigeration cycle lies in the range of 4–10. Also, it has been found that relatively small coefficients of performance of the first and second cycles, less than 6 and 1.5, respectively, result in low net power of the steam plant over the period of charging the cooling storage container (both refrigeration machines run in unison). In this case, the net plant power amounts to less than 26% of the total generated plant power when the time of storing the cooling is lower than double the time of the peak-loads. This necessitates increasing the storing time to assure reasonable available power to be exported to the grid. Economical analyses of the proposed system have showed that both the capital cost and energy charges are less for the proposed system than that of the steam plant without cooling storage for practically possible operating conditions.