Storing solar energy with chemistry: the role of thermochemical storage in concentrating solar power

Concentrating solar power (CSP) with thermal energy storage has the potential for grid-scale dispatchable power generation. Thermochemical energy storage (TCES), that is, the reversible conversion of solar-thermal energy to chemical energy, has high energy density and low heat loss over long periods. To systematically analyze and compare candidate reactions for TCES, we design an integrated process and develop a general process model for CSP plants with TCES systems. We illustrate our model applicability by using ammonia and methane systems with two gas storage options. The analysis allows us to identify critical issues as well as key targets for fluid phase TCES systems. Gas storage is identified as the main cost driver and compressor electricity consumption as the main energy driver. The impacts of reaction temperature, operating pressure and plant characteristics are also studied.