Application of heat storage reservoirs to improve the performance of Brayton cycle nuclear power plants with atmospheric heat rejection

Abstract

Large power plants, and in particular nuclear power plants, are wasting some 60–70% of the thermal energy produced during the conversion of heat into electricity. The favored site locations have been near an abundant source of constant temperature water (i.e. river or ocean). Sites close to rivers and the ocean, and close to consumers are difficult to find. Future sites for new power plants will likely be in remote locations and depend on atmospheric air cooling as a heat sink. One of the major drawbacks to these new sites is the daily and monthly fluctuations of the atmospheric temperature affecting the conversion efficiency of heat into electricity. The present study examines the performance improvement vs economic cost of using heat storage reservoirs to maximize the net energy output of these power plants using dry cooling towers. A case study is presented for an HTGR (high temperature gas-cooled reactor) operating on a Brayton direct closed cycle (He coolant) and located on a desert site (Blythe, California). The capacity of the HTGR in the desert environment on average is 1060 MWe without reservoir cooling. When provided with the reservoir cooling system, the capacity of the HTGR is increased to an average value of 1090 MWe. During the hottest summer month, the efficiency of the HTGR is increased from 34.24 to 35.20 during the hottest hour of the day. For this same period, the capacity is 977 MWe without reservoir cooling and is increased by 6% to 1034 MWe with reservoir cooling. Generally, the direct cycle HTGR with natural draft dry cooling towers and a reservoir cooling system is economically feasible if the future worth of the capital investment of the additional components does not exceed the revenues from the sale of the increased output. Assuming that the worth of electricity, at the bus bar, is 2 cents kWh −1 the value of the additional capital investment in equipment and maintenance could be as high as $3.6 million at a 10% return on the investment.