ENERGY STORAGE AND TRANSFERENCE BY MEANS OF LIQUID HEAT RETENTION MATERIALS

1524236 Steam turbine plant EXXON RESEARCH & ENG CO 28 Nov 1975 [16 Dec 1974(2)] 48997/75 Heading FIT [Also in Division F4] In an electricity generating plant comprising a constant output nuclear reactor or fossil fuel furnace, a boiler and a steam turbine, steam reheating and feed-water pre-heating is effected at part-load operation by bled steam whereas at full load the bleed is reduced and the reheating and pre-heating effected by heat exchange with a liquid heat storage material at atmospheric pressure. The plant comprises a boiler 1 supplying steam through lines 2, 7 to a high-pressure turbine 6 and thence through reheater 5 to lower pressure turbine 6a. During part-load operation steam bled from turbines 6, 6a through lines 22a, b and 18a, b heats feedwater in line 16 flowing through preheaters 21a, b and 17a, b. In addition some of the bled steam is branched-off through lines 27a, b and 39a, b to heat oil and water respectively flowing in lines 30, 42 through heat exchangers 28a, b and 40a, b. The oil may be additionally heated in heat exchanger 31 by live steam tapped through line 32. The hot oil and water are stored at atmospheric pressure in tanks 34, 43. At full load, pre-heating and reheating by steam is terminated by closing valves 15, 25, 26, 33, 37, 38, 66 and opening valve 50 so all the feedwater passes along line 52 through pre-heaters 53, 55, 59 to be heated by the stored hot water and oil flowing from tanks 43, 34. Some of the hot oil also heats the steam in reheater 5. Thus the plant output is increased without increasing the output of boiler 1. In a modification Fig. 4, (not shown) an additional heat storage stage is provided using a molten salt, sodium or potassium hydroxide or mixtures thereof, or a metal. In another arrangement the heat storage material may be additionally heated by solar energy or waste heat.