1. Tokyo Gas Co., Ltd., Energy System Research Institute, 1-7-7, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan;
2. Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei 184-8588, Tokyo, Japan e-mail:
3. Institute of Engineering, Tokyo University of Agriculture and Technology, 2-24-16, Nakacho, Koganei 184-8588, Tokyo, Japan e-mail: