Numerical Modeling of the Thermal Behavior of Subsea Hydro-Pneumatic Energy Storage Accumulators Using Air and CO 2

Luke Jurgen Briffa, Charise Cutajar, Tonio Sant () and Daniel Buhagiar
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Luke Jurgen Briffa: Department of Mechanical Engineering, University of Malta, MSD 2080 Msida, Malta
Charise Cutajar: Department of Mechanical Engineering, University of Malta, MSD 2080 Msida, Malta
Tonio Sant: Department of Mechanical Engineering, University of Malta, MSD 2080 Msida, Malta
Daniel Buhagiar: FLASC B.V. Paardenmarkt 1, 2611 PA Delft, The Netherlands

Energies, 2022, vol. 15, issue 22, 1-20

Abstract: This paper numerically models the thermal performance of offshore hydro-pneumatic energy storage (HPES) systems composed of a subsea accumulator pre-charged with a compressed gas. A time-marching numerical approach combining the first law of thermodynamics with heat transfer equations is used to investigate the influence of replacing air within an HPES system with carbon dioxide (CO 2 ). The latter is able to experience a phase change (gas–liquid–gas) during the storage cycle in typical subsea temperatures when limiting the peak operating pressure below the critical point. The influences of integrating a piston and an inner liner within the accumulator to mitigate issues related to gas dissolution in seawater and corrosion are explored. It is found that the energy storage capacity of subsea HPES accumulators increases substantially when CO 2 is used as the compressible fluid in lieu of air, irrespective of the accumulator set up. It is also noted that the length-to-diameter ratio of the accumulator has a considerable influence on the round-trip thermal efficiency for both air- and CO 2 -based accumulators. Another factor influencing the round-trip thermal efficiency is the presence of the inner liner. Moreover, the CO 2 -based HPES system yields a lower round-trip thermal efficiency over that of air.

Keywords: offshore; energy storage; phase change; accumulator; carbon dioxide (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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