Application and design studies of compressed-air energy storage for solar applications. Final report

Abstract

This report describes a study of adiabatic Compressed-Air Energy Storage (CAES), in which both the heat of compression and the compressed air are stored separately, and the applicability of this technology to solar power systems. The basic thermodynamics of ideal single- and two-stage adiabatic CAES is reviewed. Generic single-stage and two-stage types are discussed, and efficiency and mass flow rate as a function of storage pressure and stage pressure ratios are investigated. The performance and cost of available turbomachinery for the single- and two-stage adiabatic systems are given in detail as the basis for evaluating sixteen candidate near-term single-stage and two-stage designs. Both excavated caverns and abandoned mines are considered for storage reservoirs. Two scenarios are considered regarding joint application of CAES and Solar Thermal Energy (STE) systems. One is based on providing local CAES storage for STE systems, other on providing solar-augmentation to adiabatic CAES installations. Both solar-heated thermal storage and fuel firing are considered for provision of necessary backup during bad weather. Solar-heated heat-topping of adiabatic CAES is also considered, but rejected as an unattractive technology. The economics of all these systems is ranked on the basis of delivered busbar energy cost for three different charging energy costs. The adiabatic systems are compared to fired systems to determine the breakeven cost of fuel which yields the same busbar energy cost. An economic comparison with pumped hydro and peaking gas turbines is also given. Recommendations for future development of this technology are presented.