Heat Pump and Steam Accumulator Electrical Energy Storage System (Esheatpac System)

Abstract

Esheatpac is an electricity storage system that combines heat pump, steam accumulator, and steam-water cycles technologies. It includes a heat pump, powered by an electric compressor, which produces saturated steam that is stored in steam accumulators as pressurized liquid water. Later, this steam produces electricity in a turbo-generator. Combination of efficiency of heat pump and Rankine cycle heat rate allows reaching efficiencies of up to 100% or higher, without requiring any auxiliary fuel. Efficiencies of up to 124.5% can be achieved by providing natural gas, with the combination of heat pumps with COP equals 2.65 and Rankine cycles with heat rate of 47%. The above means that it is possible to extract from the system the same or higher amount of electricity that enters it, after remaining stored for the time required, up to almost 25% more. Esheatpac is an optimal solution for when it is required to store large amounts of electricity and medium discharge times. Today, the only storage systems that meet these conditions are pumped hydro storage (PHS) and compressed air energy storage (CAES). Compared to PHS, Estheapc presents the advantages of its better performance, a maximum of 85%, and less environmental and public opposition problems, in addition to the limitations to find suitable locations. Compared to CAES, it presents the advantages of its better performance, 50% in current plants, and much lower storage capacities, on the order of seven times less, which also means a lower material investment.