POSEIDON (Photo-driven Optimal Seawater Electrolysis for energy-IslanDs OperatioN) aims at investigating innovative renewable energy systems suitable for the operation in remote/scarcely-connected areas, yet having access to low-quality water. The proposed tri-generation technology yields electricity, hydrogen and freshwater. Hydrogen is either re-converted into power by a fuel cell for electricity management or undergoes further chemical processes to get so-called e-fuels for the heat and mobility sectors. The assortment of energy conversion pathways is fundamental for the independence and resilience of the targeted users' in all energy sectors.