Recently, co-generation system (CGS) is introduced to small scale objective that heat demands changes through the year, such as household use and business place. However, as capacity of prime mover is small, the power generation efficiency becomes low. And heat-using ratio becomes low in middle season such as spring and autumn. Therefore, it is necessary to examine the influence of low capacity of prime mover and low heat to power ratio on effective use of energy. In this study, we evaluate the effective use of energy using heat quantity and exergy for 200kW gas engine cogeneration system introducing to Energy Conversion Research Center in Doshisha University. As the result, it was shown that it is necessary to optimize the heat recovery devices and the heat utilization devices for the improvement of the thermal efficiency of CGS, and to improve the power generation efficiency of prime mover for the improvement of the exergy efficiency of CGS. Moreover, the amount of primary energy use can be reduced throughout the year by introducing an absorption refrigerator of the output 210kW and a heat to power conversion system of the thermal efficiency over 10% into CGS.
