Compressed air energy storage for a small size standalone plant powered by a solar power unit and a gas turbine

Energy storage can balance heat and power demand and production over different time scales, with both technical and economic benefit. Several devices have been proposed, but only two are really utilized: hydro-pumped storage, for large size plants, and electrochemical battery energy storage, for medium and small plants. Compressed Air Energy Storage (CAES) was proposed as an alternative, and two well-known plants, Hunthorf (Germany) and Mac Intosh (United States) have been successfully working for many years. However, due to the huge capital costs, this concept never became widely popular. Here, a bit different approach is proposed: one or more reciprocating compressors and pressurized reservoirs can supply an additional amount of air to a gas turbine. During the “charging” phase, the reciprocating compressors pump air into the reservoirs; during the “discharging” phase, the turbo-expander is fed by both the turbo-compressor and the reservoirs in parallel. The turbo-compressor is partially relieved and fuel can be saved for the same power. This paper focuses on a standalone small size user, served by a solar power unit coupled with a micro gas turbine. The aim is to lay down rules for a proper storage managing.