Design, exergy and exergoeconomic analysis and optimization of a CCHP + TES for the use in a complex building

The present paper aims at the optimization and exergy and thermoeconomic analyses of a combined cooling, heat, and power generation system equipped with a thermal energy storage for the use in a residential complex with a gas-fueled internal combustion engine as the prime mover. The system is optimized using the direct search method by minimizing annual cost in two cases of using/not using a thermal energy storage. In case of the use of a thermal energy storage, an engine with a capacity of 2 MW and an operating time of 4000 h are found to be optimal, but when a thermal energy storage is included, an engine with a capacity of 2 MW and an operating time of 5268 hours and a thermal energy storage with a capacity of 18.93 m3 are found to be the optimal options. Both systems are evaluated assuming selling/not selling surplus power to the public power grid. The best case for the performance of the system is to use a thermal energy storage and to sell surplus electricity to the grid. In this case versus the case of excluding the thermal energy storage, primary energy consumption, CO2 emission, operating cost of the system, and power purchase from the public grid are decreased by 20.8, 19.5, 14.3 and 17%, respectively while return on capital is increased by 3.1% resulting in 10.7% higher annual cost of the system.