Multi-objective optimal operation strategy study of micro-CCHP system

As the practical load conditions vary with time, the performance of micro combined cooling heating and power (micro-CCHP) system depends a lot on the operation strategy. So, it is significant to study the system performance and find the optimal operation strategies for various load conditions. There are many devices can be considered in micro-CCHP system. In this study, a comprehensive micro-CCHP system is built, basing on gas engine and adsorption chiller. Auxiliary devices, such as gas boiler, heat pump and electric chiller, are also considered in the study of operational optimization. In order to find the optimal operation strategies and discuss why they are the optimal ones, a mixed-integer non-linear programming model is developed. Energy saving ratio and cost saving ratio are chosen as the objectives and they are calculated hierarchically. Operation strategies under various load conditions are analyzed in detail and two dimensional distributions of system performance are presented. Results show that, optimal operation strategy changes with load conditions for energy saving optimization while it also changes with energy prices for cost saving optimization. For energy saving optimization, micro-CCHP system is always superior to conventional separated system when the heating load is over 12 kW in CHP (combined heating and power) mode or over 21 kW in CCHP mode. For cost saving optimization, micro-CCHP system can be superior to conventional separated system when the dimensionless energy price ratio is less than 0.45.