1. The Bartlett School of Sustainable Construction, University College London, London, WC1E 7HB, U.K.
2. Center for Energy, Environment & Economy Research, Zhengzhou University, Zhengzhou 450001, China
3. School of Public Policy and Management, Tsinghua University, Beijing 100084, China
4. Center for Energy Economics and Sustainability, Peking University, Beijing 100871, China