Integration of a thermochemical energy storage system in a Rankine cycle driven by concentrating solar power: Energy and exergy analyses

This paper proposes and investigates novel concepts on the integration of a thermochemical energy storage (TCS) system in a concentrating solar power (CSP) plant. The TCS material used is calcium oxide reacting with water and the power cycle studied is a Rankine cycle driven by CSP. Firstly, three integration concepts on the coupling of the TCS system with the Rankine cycle are proposed, including the thermal integration concept, the mass integration concept and the double turbine concept. Then, an energy analysis is performed to determine and compare the theoretical overall energy efficiency of the proposed concepts. After that, an exergy analysis is carried out for the selected integration concepts so as to evaluate and compare the overall exergy efficiency of the installation with TCS integration. The results show that the turbine integration concept has the highest overall energy efficiency (0.392), followed by the thermal integration concept (0.358) and the mass integration concept (0.349) under ideal conditions (11 h of charging; 13 h of discharging). The energy storage density is estimated to be about 100 kWhel∙t−1. Exergy analysis results also indicate that the turbine integration concept seems to be the best option under the tested conditions. •Novel integration concepts of a thermochemical TES in a Rankine cycle driven by CSP.•Calcium hydroxide used as TCS material, with energy storage density ∼100 kWhel∙t−1.•Performance modelling of the proposed concepts based on energy and exergy analyses.•Reduced overall energy efficiency of the installation caused by different losses.•Turbine integration seems to be the best option with the highest overall efficiencies.