Indirect power cycles integration in concentrated solar power plants with thermochemical energy storage based on calcium hydroxide technology

Abstract

Thermochemical energy storage is attracting interest as a relevant alternative energy storage system in concentrating solar power plants. Efficient, low-cost, and environmentally friendly thermal energy storage is one of the main challenges for the large-scale deployment of solar energy. The reversible hydration/dehydration process of calcium oxide is one of the most promising concepts for energy storage integration at intermediate temperatures in solar plants. The efficient integration of concentrated solar power with a thermochemical energy storage system based on the calcium hydroxide concept, individually or integrated into a hybrid system with sensible heat storage, can be a feasible solution for long-term energy storage. Efficient energy recovery and subsequent power production are crucial. This work presents a novel analysis of the indirect integration of different power cycle configurations to optimise the roundtrip efficiency of the system. Steam Rankine, closed CO2 Brayton, and organic Rankine cycles are considered. The analyses show power block efficiencies in the range of 38–50%, with a global roundtrip efficiency of 37.1% in the case of the CO2 supercritical cycle.