Absorption seasonal thermal storage cycle with high energy storage density through multi-stage output

Absorption thermal storage is attractive due its small thermal loss during long term storage, which is advantageous for seasonal solar thermal storage. For the long term storage, high energy storage density is favorable to ensure a compact system. In this paper, the novel absorption seasonal thermal storage cycles with multi-stage output processes are proposed. Comparing to the conventional cycle with single stage output, larger concentration glide could be achieved by the proposed cycles under the same condition, resulting in high energy storage density. Performances of the water-LiBr absorption thermal storage cycles with double stage output and triple stage output are calculated and compared with that of the conventional single stage cycle. Energy flows, effects of temperature parameters, and working pair comparison are analyzed. For typical condition of solar thermal charging in summer and heat output in winter with output temperature of 50 °C, the proposed cycles with double stage output and triple stage output have 75.4% and 82.3% less heat losses, and achieve 7.32 times and 6.78 times higher energy storage densities than the single stage cycle. The proposed absorption thermal storage cycle with multi-stage output could be a good option for seasonal solar thermal energy storage.