Comparison of CCHP Efficiencies Based on Off-design Characteristics

Indicators for evaluating the efficiency of combined cooling, heat and power (CCHP) systems are vital for optimal design and economic operation. Based on the typical analytical performances of gasturbine-based CCHP components, some intrinsic parameters related to the efficiencies with different definitions (i.e., total energy utilization efficiency, equivalent exergy efficiency, economic exergy efficiency and energy saving indicator) were thoroughly discussed. To compare the different efficiencies or indicators, overall off-design characteristics of two types of gasturbine-based CCHP systems were evaluated with the efficiencies. The results show that, none of the above efficiencies evaluate CCHP completely. However, energy saving indicator comparatively distinguishes the two systems studied, except for some incomplete evaluation conclusions. It is proposed that the optimal configuration and economic operation can be evaluated by integrating energy saving indicator with economic exergy efficiency at off-design conditions.