Small Mediterranean islands are a type of remote and off-grid communities characterized by a carbon-intensive electricity system coupled with energy-intensive drinking water production (desalination) technologies. The purpose of this study is to propose a new multi-objective dynamic optimization approach to improve the sustainability of small islands through the introduction of renewable energy sources. The main contributions of our approach include (i) dynamic modeling of desalination plant operations,

(ii) joint optimization of system design and operations,

(iii) multi-objective optimization to explore trade-offs between potentially conflicting objectives.

The approach is tested on the real case study of the Italian island of Ustica, through a comparative analysis using a traditional non-dynamic, cost-minimization approach. Numerical results show the effectiveness of the approach in identifying optimal system configurations, which have better performance of different sustainability indicators than traditional design, by limiting structural interventions, investment costs and environmental impacts. In particular, optimal dynamic solutions capable of meeting the entire water demand enable high levels of penetration of renewable energy sources (up to over 40%), reducing the net present cost by about €2-3M and CO₂emissions by more than 200 tons/year.