Volume 8: Advances in Energy Innovation and Development

Modelling and Thermodynamic Analysis of Small Scale Compressed Air Energy Storage Systems with Thermal Recovery Lakshmanan S, Gnanavel B K

Abstract

The global fossil fuel source is limited and is getting depleted rapidly. The growth in energy demand worldwide is ever increasing, thus increasing fossil fuel consumption. Use of fossil fuels in electrical energy generation have environmental impacts like global warming , CO2 emissions etc., This necessitated use of alternate renewable energies like solar, wind to meet energy requirements. But the limitation of renewable energy sources are that they are intermittent in supply, uncertainty of availability etc., lead to difficulties in ensuring stability in electrical grid networks. These constraints led to the development of various energy storage technologies so that available surplus energy from renewable sources can be stored and released as and when needed to maintain grid supply stability both in terms of power and frequency. Thus Electrical Energy Storage (EES) is of great importance to ensure striking a balance between demand and supply .Many storage technologies have been developed and used at present like pumped hydro, solar thermal, batteries, compressed air, flywheel etc., Compressed air storage technology has the advantage of reduced emission and possibility of large capacity plants. About 440 MW installations of CAES are available at present around the world. Compared with other energy storage technologies, CAES is proven to be a clean and sustainable type of energy storage with the unique features of high capacity and long-duration of the storage.
The intention of this paper is to model and analyse a small scale compressed air storage system useful for standalone and micro-grid applications. The economics of CAES is also discussed. Thermodynamic analysis of the charging and discharging cycles in the storage tank is modelled and analysed for a small capacity CAES. A thermodynamic study on the proposed system covering all components like compressor, expander is also done and related models analysed. The heat energy released during compression

stage is recovered, utilized during expansion so that the round trip efficiency improves. This paper also covers this aspect, comparing the efficiencies of systems with and without heat recovery.

Keywords Compressed air Energy storage System (CAES), Heat Recovery, Thermodynamic analysis