Performance study on a new solar aided liquid air energy storage system integrated with organic Rankine cycle and thermoelectric generator

Abstract

In order to further improve the round trip efficiency (RTE) of the traditional liquid air energy storage (T-LAES) system, this paper proposes a new solar aided liquid air energy storage (SALAES) system, which uses the oil-air heat exchangers and molten salt-air heat exchangers connected in series to increase the air temperature in turbine inlet and couples an organic Rankine cycle (ORC) and a thermoelectric generator (TEG) to make full use of the waste heat. The effects of key parameters on the performance of the SALAES system are investigated, the research results show that the new system can obtain the highest RTE when the liquefaction pressure is 155 bar, the liquefaction temperature is −183 °C, the discharging pressure is 70 bar, and the ORC operating pressure is 110 bar. Meanwhile, an SALAES system without oil-air heat exchangers is established as the reference system, and the performances of the two systems are compared under the same parameters. The results show that the new SALAES system achieves an RTE of 72.38 % under design conditions, 22.6 % higher than that of the T-LAES system, and 7.06 % higher than that of the reference system. When the direct normal irradiance is greater than 900 W/m2, the RTE of the SALAES system reaches 75.08 %. When poor weather conditions prevent the solar collection field from operating, the new SALAES system can rely on the additional oil-air heat exchangers to achieve a 43.2 % RTE advantage over the reference system. The exergy analysis results show that the exergy efficiency of the new SALAES system is 38.02 % under design conditions, which is 3.71 % higher than that of the reference system. The exergy destruction of the solar collection field is the largest, reaching 57.09 %, and among other components, the TEG and the coolers have the largest exergy destruction. The new SALAES system is sensitive to the intensity of solar radiation and the solar proportion is inversely proportional to the overall exergy efficiency.