Use of Cooling Thermal Storage as a Heat Sink for Steam Power Plant

Abstract

In the present paper, a system is proposed for improving the performance of steam power plant with air-cooled condenser during peak loads. In this system, the power plant comprises two steam turbines, and the air-cooled condenser is replaced by two condensers. The first one is air-cooled (dry) and used for condensing the exhaust steam of the first turbine, while the second is water-cooled and serves to condense the steam outlet of the second turbine. The warm cooling water exiting the wet condenser is pumped to a cooling storage container, where it is cooled and re-circulated to the wet condenser. Cooling is produced by a refrigeration machine driven by the extra electric power generated by the two turbines during the time of the off-peak-loads (low electricity rates). Simple energy analyses have been developed to predict the energy characteristics of this system. The results of this paper showed that the proposed system leads to improving the plant power output at peak-loads. About 6, 16, 24 and 33% increase in generated plant power can be achieved at peak-loads (high electricity rates) when the ambient temperature is 20, 30, 40 and 50°C respectively, and the whole steam exiting both turbines is cooled in a wet condenser to a design temperature of 20°C. The results showed also that choice of the capacity of each turbine is essentially affected by the quality of the refrigeration machine and ambient temperature.