1. State Key Laboratory of Clean Energy Utilization, Dept. of Energy EngineeringZhejiang UniversityHangzhou 310027 P.R. China
2. SINTEF Energy ResearchTrondheim N‐7465 Norway
3. Dept. of Energy and Process EngineeringNorwegian University of Science and Technology Kolbjørn Hejes vei 1BTrondheim NO‐7491 Norway