Abstract
We have introduced "heat factor" for the evaluation of the total energy efficiency of cogeneration system in Japan. According to our analysis based on exergy basis, the "heat factor" for Japan is calculated to be 0.24 - 0.28, which is much smaller than the factor for US and Europe, which are 0.5 or higher. This result implicates the difficulty of the use of thermal output of cogeneration in Japan, which has little heat demand compared to the US and Europe. By comparing the adjusted total efficiency of cogeneration with the grid power plant (all average, fossil fuel average, state of art LNG combined cycle), we found that it was inappropriate to regard cogeneration as highly efficient just by the simple total efficiency. The adjusted total efficiency was calculated to be nearly equal or a little higher than the average fossil fired power plant depending on the type of demand, and much smaller than the state of art LNG combined cycle for all demand assumed in our study.
