Thermoeconomic optimization for a solar power generating system capable of storing energy by using calcium looping process

Abstract

Energy storage facilities play a crucial role in mitigating the fluctuations of renewable energy sources such as solar and wind. These facilities can be used in solar-driven power plants to store solar energy during the day for use during periods of low or no sunlight to increase the plant’s capacity factor. This study evaluates the application of calcium looping reaction as a thermochemical energy storage unit in solar power plants to produce renewable electricity 24 h per day. Supercritical and trans-critical CO2 cycles are employed as upper and bottoming cycles, respectively, to produce power from solar energy. The energy storage unit absorbs energy during the day through a chemical reaction and releases it at night via a reverse chemical reaction. The proposed system is evaluated from both thermodynamic and economic points of view. A genetic algorithm-based multi-objective optimization is also carried out considering different scenarios. Energy and exergy efficiencies of the power generation cycle and levelized cost of electricity are found to be 46.4%, 50%, and 132.5 $/MWh, respectively, under the base case operating conditions. The obtained energy efficiency is 2% higher than a similar design operating with subcritical CO2 Brayton and steam cycles. Furthermore, under the optimization conditions, the power cycle exergy efficiency is improved by 1.2%, and the levelized cost of electricity is decreased by 5.1% compared with the base case conditions.