Pumped thermal grid storage with heat exchange

A thermal heat-pump grid storage technology is described based on closed-cycle Brayton engine transfers of heat from a cryogenic storage fluid to molten solar salt. Round-trip efficiency, computed as a function of turbomachinery polytropic efficiency and total heat exchanger steel mass, is found to be competitive with that of pumped hydroelectric storage. The cost per engine watt and cost per stored joule based are estimated based on the present-day prices of power gas turbines and market prices of steel and nitrate salt. Comparison is made with electrochemical and mechanical grid storage technologies.