Optimal sizing of a hybrid PV-WT-battery storage system: effects of split-ST and combined ST + ORC back-ups in circuit charging and load following

This study explores the opportunities in deploying split Stirling and combined Stirling and organic Rankine cycle (ORC) in circuit charging and load following dispatch modes, respectively as the back-up of a hybrid renewable energy system. The optimal number of system components in each dispatch mode that simultaneously minimises the loss of power supply probability (LPSP), levelised cost of energy (LCOE) and dumped power have been found by implementing an evolutionary algorithm-based multi-objective optimisation approach. Then, a multi-criteria decision making tool is deployed to select the best configuration from the Pareto set. The optimal hybrid system configuration obtained have been compared to the traditional diesel generator back-up system base case, to demonstrate performance improvements with the deployment of the proposed back-ups. The results show deploying Stirling + ORC back-up in load following leads to 60.70% and 33.71% reductions in the LCOE and CO<inf>2</inf> emissions, respectively compared to the base case but with slightly higher LPSP. While 61.4%, 33% and 24.47% reductions in the LCOE, CO<inf>2</inf> emissions and LPSP have been observed with the deployment of split Stirling in circuit charging mode. Further results from the dynamic simulation highlight the energy cost, reliability, dumped power and battery performance of the optimal system respond to seasonal changes in the test location. Other observed results show the change in the market price and number of the photo-voltaic generator that generates 50% of the total power, strongly affect the performance of the optimal system. The proposed biomass powered Stirling based back-ups are promising alternatives to replace the traditional diesel generator back-ups in improving the green energy system's reliability.