ABSTRACT
This chapter presents an introduction to the compressed air energy storage (CAES) concept and applications. The use of compressed air and compressed air storages is diverse and has a long history (de.wikipedia.org/wiki/Druckluft 2013). Compressed air was and is still being used in many applications, including: pneumatic control systems, pneumatic hammers and other tools, diving, brakes and weapons. In 1840 the first compressed air car was presented in Paris, and recently plans to build compressed air cars are booming due to environmental concerns. Compressed air locomotives are in use in tunnels ormines.All these applications have compressed air storages, i.e. smaller or bigger pressure vessels. In summary, it can be deduced that the compressed air is a well-known technology and an established form of storing energy. A CAES plant consists mainly of an electric motor driven compressor, a compressed air storage
(e.g. a cavern), an expansion engine that drives a generator, connecting pipes and control systems. Also, it might involve a heat exchanger, a heat storage, a heat recovery steam generator (HRSG) and a steam turbine with a generator. Instead of air, other gases could be used also. Some propose the use of water as working medium, such that a generator consuming surplus electricity drives a pump charging water into a pressure vessel with an air cushion. At demand, the stored water can then be utilized to drive a water turbine with a generator to generate electricity. Two underground caverns with different cushion air pressure are proposed to be connected via a water pump/turbine with a motor/generator, which can be placed on the ground due to high enough pressure. Not only turbo engines can be used. In particular, for small capacity plants, reciprocating or screw type engines are preferable. Therefore, a wide range of combinations can be utilized and already have been proposed. This chapter focuses on the use of compressed air as an electricity storage with turbomachinery
in the scale of MWh or GWh. This kind of storages are capable of providing the electricity of usual utility power plants with a capacity of some hundred MW for some hours or even days. In Section 13.1 the motivation to build electricity storages and their use in electrical grids is described. In Section 13.2 the fundamentals of compressed air energy storages are presented and finally in Section 13.3 the best known CAES-cycles are presented.
