1. Department of Electrical & Electronic EngineeringThe University of Hong KongRoom 601, Chow Yei Ching Building, Pokfulam RoadHong Kong
2. Institute for Advanced Sustainability StudyBerliner Strasse 130Potsdam14467Germany
3. Department of Electrical and Electronic EngineeringSouth University of Science and Technology of ChinaShenzhen518055People's Republic of China
4. Technical University of BerlinBerlin10243Germany