Conceptual design of compressed air energy storage electric power systems

Conceptual design studies have been conducted to identify Compressed Air Energy Storage (CAES) systems which are technically feasible and potentially attractive for future electric utility load-levelling applications. The CAES concept consists of compressing air during off-peak periods and storing it in underground facilities for later use. During peak-load periods the air would be withdrawn, heated by recuperation and combustion and expanded through turbines to generate power. By using off-peak electricity for compression and stored air for peak-load generation, the resulting oil consumption would be about 40 per cent of that consumed by conventional gas-turbine peaking plants. The turbomachinery requirements for this type of system could be met using existing equipment with relatively modest modifications. Although the study discussed herein focused on the storage of air in hydraulically compensated, mined, hard-rock caverns, the compressed air could also be stored in underground aquifers or leached-out salt cavities. Conventional underground excavation technology could be used to construct these storage caverns. A geological survey of the north-central and north-east regions of the United States indicated that sufficient siting opportunities exist such that a prudently designed CAES plant should have little long-term adverse impact on the environment. The competitive position of CAES relative to conventional generation alternatives is highly dependent on utility-specific factors. The cost of electric energy from CAES is generally competitive with costs from conventional peak-shaving systems such as gas turbines and will improve as low-cost off-peak energy from nuclear plants becomes available.