The research entitled “Energy systems flexibility for islands’ decarbonisation” is part of a broad endeavor to support islands in the development of specialized renewable energy systems modeling capabilities relevant to environmental systems. The projects are a wide range of investigations ranging on hybrid renewable energies in several islands. Four projects have been done in cooperation with NTNU, considering, in particular, an Italian case study (Sicily Island) and Norwegian (Hinngya island) and also Iranian islands. In this process, the researcher developed a range of new methodologies, devised practically implementable energy, economic and environmental schemes.