1. Energy Engineering Section, Department of Mechanical Engineering, Technical University of Denmark, Nils Koppels Allé 402, DK-2800 Kgs. Lyngby, Denmark, Department of Energy and Process Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway, and ReaTech, c/o Centre for Advanced Technology, Post Office Box 30, DK-4000 Roskilde, Denmark