This joint workshop and seminar series was an international collaborative research program between German institutions and SESP UI. The seminar was conducted in 4 sessions which delivered by Reiner Lemoine Institute (RLI), SESP UI, Technische Universität (TU) Berlin, and Wuppertal Institute (WI). The German institutions presented about their current projects on sustainable energy systems for islands, such as the on-going one of off-grid solar PV in an isolated island in Philippines. SESP UI delivered the recent publication titled Multi-objective optimization of a multiregional electricity system in an archipelagic state: The role of renewable energy in energy system sustainability. The main goal of the event is to share sustainable energy supply concepts for islands and gather key future research to accelerate sustainable energy system transition as well to develop off-grid systems for archipelagic country like Indonesia.