Abstract
We present analyses of three families of compressed air energy storage (CAES) systems: conventional CAES, in which the heat released during air compression is not stored and natural gas is combusted to provide heat during discharge; adiabatic CAES, in which the compression heat is stored; and CAES in which the compression heat is used to assist water electrolysis for hydrogen storage. The latter two methods involve no fossil fuel combustion. We modeled both a low-temperature and a high-temperature electrolysis process for hydrogen production. Adiabatic CAES (A-CAES) with physical storage of heat is the most efficient option with an exergy efficiency of 69.5% for energy storage. The exergy efficiency of the conventional CAES system is estimated to be 54.3%. Both high-temperature and low-temperature electrolysis CAES systems result in similar exergy efficiencies (35.6% and 34.2%), partly due to low efficiency of the electrolyzer cell. CAES with high-temperature electrolysis has the highest energy storage density (7.9 kWh per m3 of air storage volume), followed by A-CAES (5.2 kWh/m3). Conventional CAES and CAES with low-temperature electrolysis have similar energy densities of 3.1 kWh/m3.
Highlights
Large penetrations of wind and solar energies challenge the reliability of the electricity grid, due to their intermittency and uncertainty
Our analysis shows that the A-compressed air energy storage (CAES) system has the highest exergy storage efficiency, followed by conventional CAES, and the hydrogen based CAES systems
High exergy losses in electrolyzers constitute a key contributor to the overall low storage efficiency of CAES-high temperatures (HTE) and CAES-low-temperature electrolyzer (LTE)
Summary
Large penetrations of wind and solar energies challenge the reliability of the electricity grid, due to their intermittency and uncertainty. CAES stores electrical energy as the exergy of compressed air. Schematic of a generic conventional compressed air energy storage (CAES) system. Harnessing the energy stored in the compressed air Both utilize the temperature increase from the air greenhouse gas (GHG) emissions-free. Utilizing the high-temperature heat of compression the demand electricity hydrogen the high-temperature heat of compression lowers the lowers electricity of demand hydrogenofproduction production in the CAES-HTE system. This paper explores whether the compression heat at sufficiently high temperatures could reduce the electricity demand of hydrogen use of the compression heat at sufficiently high temperatures could reduce the electricity demand of production enough to make the efficiency of CAES-HTE competitive with A-CAES.
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