New operation strategy and multi-objective optimization of hybrid solar-fuel CCHP system with fuel thermochemical conversion and source-loads matching

Multi-energy hybrid energy systems are a promising option to mitigate fluctuations in the renewable energy supply and are crucial in achieving carbon neutrality. Solar-fuel thermochemical hybrid utilization upgrades solar energy to fuel chemical energy, thereby achieving the efficient utilization of solar energy, reducing CO2 emission, and improving operation stability. For hybrid solar-fuel thermochemical CCHP systems, conventional integration optimization methods and operation modes do not account for the instability of solar energy, thermochemical conversion, and solar fuel storage. To improve the utilization efficiency of solar energy and fuel and achieve favorable economic and environmental performance, a new operation strategy and the optimization of a mid-and-low temperature solar-fuel thermochemical hybrid CCHP system are proposed herein. The system operation modes for various supply-demand scenarios of solar energy input and thermal-power outputs are analyzed, and a new operation strategy that accounts for the effect of solar energy is proposed, which is superior to conventional CCHP system strategies that primarily focus on the balance between system outputs and user loads. To alleviate the challenges of source-load fluctuations and supply-demand mismatches, a multi-objective optimization model is established to optimize the system integration configurations, with objective functions of system energy ratio, cost savings ratio, and CO2 emission savings ratio, as well as decision variables of power unit capacity, solar collector area, and syngas storage capacity. The optimization design of the system configuration and the operation strategy improve the performance of the hybrid system. The results show that the system annual energy ratio, cost saving ratio, and CO2 emission saving ratio are 52.72%, 11.61%, and 36.27%, respectively, whereas the monthly CO2 emission reduction rate is 27.3%-47.6% compared with those of reference systems. These promising results will provide useful guidance for the integrated design and operational regulation of hybrid solar-fuel thermochemical systems.