Abstract: A power plant (1) has an energy converter (3) for converting heat energy to another form of energy with use of a working fluid, and a heat exchanger (4) for rejecting heat from working fluid. A secondary circuit (6) provides coolant to the heat exchanger (4). The secondary circuit (6) includes a heat store (7) arranged to store coolant, a secondary heat exchanger (8), a coolant diverter (12), and a controller configured to route coolant from the working fluid heat exchanger (4) to the heat store (7) in order to reject heat to the store, or to the secondary heat exchanger (8). It chooses between these according to which provides more effective heat rejection from the coolant, and possible other factors. Typically, the controller uses the heat store during daytime and the secondary heat exchanger during night time. This means that heat working fluid is rejecting heat during day time at a temperature of the night time, thereby achieving improved plant efficiency.

Abstract: A power plant (1) has an energy converter (3) for converting heat energy to another form of energy with use of a working fluid, and a heat exchanger (4) for rejecting heat from working fluid. A secondary circuit (6) provides coolant to the heat exchanger (4). The secondary circuit (6) includes a heat store (7) arranged to store coolant, a secondary heat exchanger (8), a coolant diverter (12), and a controller configured to route coolant from the working fluid heat exchanger (4) to the heat store (7) in order to reject heat to the store, or to the secondary heat exchanger (8). It chooses between these according to which provides more effective heat rejection from the coolant, and possible other factors. Typically, the controller uses the heat store during daytime and the secondary heat exchanger during night time. This means that heat working fluid is rejecting heat during day time at a temperature of the night time, thereby achieving improved plant efficiency.