Basic Study on Heat Supply Temperature Level of Combined Heat and Power System

Abstract

We made a basic study on the heat supply temperature level of Combined Heat and Power (CHP) system, from both sides of enthalpy and exergy, by defining performance indices. Rising temperature level does not affect the total thermal efficiency of the CHP plant with a back-pressure turbine, but decreases it with an extraction-condensing turbine. The total exergy efficiency increases slightly or barely varies of both type as supply temperature rising. The saving ratio of primary energy to the conventional system in which power and heat energy are generated individually, increases with supply temperature lowering as far as the CHP plant itself. However, taking acount of power demand and heat loss for conveyance of heat, it has been seen that there exist optimal points in heat supply temperature.