Comparison of the characteristics of compressed air energy storage in dome-shaped and horizontal aquifers based on the Pittsfield aquifer field test

Abstract

Most studies have suggested that aquifers with anticlinal structures are the most favorable structures for compressed air energy storage (CAES) in aquifers because of their trapping ability, but this limits the potential locations for CAES plants, as horizontal aquifers are very common only in offshore areas rich in wind power. The comparison of the characteristics of CAES in dome-shaped and horizontal aquifers can help in understanding the quantitative differences between them. In this study, based on Pittsfield aquifer field test strata and parameters, the characteristics of CAES in dome-shaped and horizontal aquifers were investigated using a numerical simulation method by establishing two comparable conceptual models of a dome-shaped aquifer and a horizontal aquifer. Reasonable matches between the monitored data and simulated results were obtained for the initial air bubble development period of the Pittsfield aquifer field test. Comparisons of the initial air bubble, air cycling performance and energy recovery efficiency were carried out with the same calculation settings for the dome-shaped and horizontal aquifers. In the initial air bubble development period, when the same air volume was injected into the dome-shaped and horizontal aquifers, the radius of the air–water interface in the horizontal aquifer was 16.7% larger than that in the dome-shaped aquifer. In the air cycling period, an isothermal cycle type with a constant injection and production air pressure was designed. The energy recovery efficiency of CAES in aquifers is calculated in terms of the concept of exergy. In the case of isothermal compressor work and ignoring the energy loss in the compressor system, the energy recovery efficiency of the horizontal aquifer can reach approximately 80% of that in the dome-shaped aquifer. The effects of wellbore injection/production length and circulation mode on the performance of CAES in both aquifers were investigated. Wellbore injection/production length has obvious impacts on air mass flow rates during initial air bubble development and subsequent cycling, and a longer wellbore injection/production length can provide greater capacity. A comparison between the daily and weekly circulation periods in the dome-shaped and horizontal aquifers showed that the daily circulation has an efficiency advantage at the same energy storage scale, and the energy recovery efficiency of the horizontal aquifer in the weekly circulation can reach approximately 74% of that of the dome-shaped aquifer. In addition, a constant flow rate injection/production gas daily cycle mode was investigated, and the results showed that this mode has higher energy recovery efficiency than the constant pressure cycle mode, and the horizontal aquifer can reach 88.39% of the efficiency of the dome-shaped aquifer. The comparison of the characteristics of CAES in dome-shaped and horizontal aquifers shows that horizontal aquifers may be a potential choice for the storage media of CAES in the case that there are no suitable aquifers with anticlinal structures in offshore areas.