CAES: Reduced to Practice

Abstract

With the deregulation of the power industry, the use of peaking power solutions such as Compressed Air Energy Storage (CAES) is receiving increasing attention. The CAES plant located in McIntosh, Alabama, owned and operated by Alabama Electric Cooperative, Inc. (AEC) is the subject of this paper. It is the only such plant in the USA and one of two in the world. In off-peak hours the plant pressurizes a cavern with compressed air. During peak hours the stored cavern air is then valved through the combustion turbines to produce any level of peaking power required between 10 and 110 megawatts. This prototype plant began operating in May 1991 and its reliability has been steadily improved. This paper describes the learning process and plant-wide equipment modifications that were made to bring the plant to its present state of reliable operation. Because the CAES operating conditions and operating modes differ from conventional gas turbines, anticipated and unanticipated problems arose. The plant is made up of “combustion turbine” type components, but because of the way the plant operates (- valving of air input - relatively high pressure and air flows at startup - abrupt air flow shutoff at shutdown), certain operating experiences are unique to a CAES plant and not seen on standard gas turbine plants. Among the areas discussed are: controls, stand-by combustor, low-pressure (LP) expander, cavern well liner, lube oil, exhaust flow damper, high-pressure (HP) combustors, LP combustors, fuel injectors, fuel handling, and hot gas path instrumentation. These topics are discussed in the problem, solution, recommendation format. The learning process described in the paper will serve as an invaluable guide to plant designers as future CAES plants are built.