Title: Exergy analysis and assessment of performance criteria for compressed air energy storage concepts

Authors: Friederike Kaiser; Uwe Krüger

Addresses: Forschungszentrum Energiespeichertechnologien, Clausthal University of Technology, Am Stollen 19A, 38640 Goslar, Germany ' Power Plants Group Wilhelmshaven, Uniper Kraftwerke GmbH, E.ON-Platz 1, 40479 Duesseldorf, Germany

Abstract: Compressed air energy storage (CAES) systems provide power reserve to compensate for intermittent renewable electric energy. The compressed air is stored to drive an open gas turbine. Enthalpy is close to zero at ambient air temperatures, which implies low storage efficiencies of the CAES open gas turbine cycle. Thus, in this project, the characterisation of CAES concepts based on exergy in contrast to enthalpy is discussed. The CAES energy efficiency defined as η_caes = W_el,G / (W_el,M + Q_fuel), resulting in approximately 42% for Huntorf and 54% for McIntosh, is unsuitable for characterizing CAES as an electrical energy storage. Instead, an alternative round trip energy efficiency η_rt4 is presented. An exergy-based counterpart is deemed ideal to evaluate storage properties of CAES. Calculations emphasize the efficient generation characteristics of fuel-driven CAES (e.g., McIntosh with 82% fuel efficiency of the turbine process as compared to a Carnot value of 75%).

Keywords: compressed air energy storage; CAES; Huntorf; energy storage efficiency; exergy; steady state thermodynamics; performance criteria; comparison.

DOI: 10.1504/IJEX.2019.098613

International Journal of Exergy, 2019 Vol.28 No.3, pp.229 - 254

Received: 04 May 2018
Accepted: 30 Oct 2018
Published online: 28 Mar 2019 *

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