Studies on the performance of distributed combined cooling, heat and power system under off-design conditions based on exergy analysis

This paper adopts the exergy analysis method of second law of thermodynamics to analyze the characteristics of off-design conditions of distributed combined cooling, heat and power system (CCHP). The research results show that off-design conditions are the primary cause of the performance decline of the system. Under the off-design conditions, although the system’s power generation and cooling capacities decline with the reduction of load, the cooling capacity declines more slowly than generating capacity. When the gas turbine load drops under 60%, the distributed combined cooling, heat and power system may not save energy. If the low grade residual heat in the system could be effectively used, it will obviously improve the system’s performance under off-design conditions. Combustor, high pressure producer, and turbine change significantly in grade differences during the change of load in gas turbine, which also means that these three parts are the areas with the highest potential for improvement of the system’s performance. The biggest loss of system exergy occurs in combustor and high-pressure producer.