Prof. Klaus Vajen served as ISES President from 2020-2024. He is director of the Institute of Thermal Engineering at the University of Kassel, Germany, where he holds the chair of Solar- and Systems Engineering, and furthermore distinguished professor of the Technical University of Kyrgyzstan in Bishkek. He holds a PhD in applied physics and is (co-)author of 300+ publications about (solar) thermal engineering, university education and energy policy. He is founder and director of the MSc-programme “Renewable Energies and Energy Efficiency” at the University of Kassel, as well as founder and head of the council “University Educations on Renewable Energies” with 150+ professors from German speaking countries.  .

Klaus was member of the ISES Board of Directors from 2003-2011 and is a member again since 2018. He was Vice-president of ISES 2006-2007, founder of Young ISES (together with J. McIntosh) as well as Chair of the Solar World Congress 2011 and of the EuroSun 2022, both in Kassel.