Exergy Analysis of Concentrated Solar Power Plants with Thermochemical Energy Storage Based on Calcium Looping

It is important and urgent to overcome the intermittent nature of solar energy as a green substitute for fossil-based electricity. Concentrated solar power plants with thermochemical energy storage are considered as a potential option for cost-effective electricity generation and dispatchability. This study aims to propose a novel concentrated solar power plant that uses thermochemical energy storage based on calcium looping with a flexible operation sequence to eliminate the dependence of power generation on the carbonation reaction under sunshine. The flexible operation involves two successive phases: energy charging in the sunshine mode and discharging in the night mode. A comprehensive exergy analysis was used to characterize the system performance based on its storage and power efficiencies. The results, which demonstrated a global storage exergy efficiency of more than 37% and a global power efficiency of around 48%, are comparable to those of the state-of-the-art systems. Moreover, it was also observed that the highest exergy loss is caused by the compressor and cooling process under the sunshine and night modes, respectively. In addition, a sensitivity analysis was performed to examine the thermodynamic laws of our system. The results indicated a technical contradiction between the storage and power efficiencies (net power) under sunshine mode, while no such contradiction was observed under night mode. Overall, the main contribution of this study is the design of a novel system with competitive performance, which is expected to serve as a useful guideline for the future development of efficient and flexible concentrated solar power plants.