1. Department of Mechanical Engineering, School of Engineering, Aalto University, Otakaari 4, 02150 Espoo, Finland
2. School of Energy System, Lappeenranta-Lahti University of Technology LUT, Skinnarilankatu 34, 53850 Lappeenranta, Finland
3. Department of Mathematics and Systems Analysis, School of Science, Aalto University, Otakaari 1, 02150 Espoo, Finland