Development and evaluation of an integrated operation strategy for a poly-generation system with electrical and thermal storage systems

In this study, a renewable energy-assisted poly-generation system with energy storage systems has been investigated with a newly developed integrated operation strategy (IOS). The IOS was designed to simultaneously decide the operation of the energy generation unit and energy conversion systems by considering the state of electrical and thermal storage systems. Subsequently, the developed strategy was applied to the poly-generation system for hospital building applications and it was compared with the system under typical operation strategies, including the minimum distance (MD) strategy and the following maximum electrical efficiency load (FML) strategy. A simulation model with validated and verified components was developed, and the performance of the system was evaluated in terms of multi-criteria (energy, environment, and economy). The results showed that poly-generation systems with the new operation strategy showed the best performance among those using the different strategies; 30.79% of primary energy saving ratio, 28.35% of carbon dioxide emission reduction ratio, and 36.86% of operating cost saving ratio with optimal operation variables, as compared to the conventional system. The results of the economic feasibility study indicated a payback period of 6.6 years for system under IOS, which was 1.4 and 3.9 years less compared to the payback period of the systems under MD and FML, respectively. The IOS flexibly controlled the electric cooling/heating ratio and prime mover operation to prevent energy storage systems from overcharging and over-discharging, which led to maximum utilization of the energy produced by the renewable energy system.