1. Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Kyotodaigaku-katsura, Nishikyo-ku, Kyoto, Kyoto 615-8540, Japan
2. Department of Urban Management, Graduate School of Engineering, Kyoto University, Kyoto, Japan
3. Socio-Economic Research Center, Central Research Institute of Electric Power Industry (CRIEPI), Tokyo, Japan