Modeling the Energy and the Water Systems in an open-access Energy System Optimization Model: the Pantelleria case study

In the framework of the Integrated Assessment Models (IAMs), the nexus approach is a systematic way to explore the interaction and interdependency between the climate, land, energy, and water (CLEW) systems in terms of synergies and trade-offs among themselves. The exploitation of dynamic relationships between CLEW domains should allow informed planning and policy decisions. The aim of the thesis is to perform an integrated water-energy system assessment for an isolated Mediterranean area, the Pantelleria island. A flexible, open access energy system optimization modeling framework (the Python-based TEMOA) has been selected to integrate the energy system and water system modeling. The structures of energy and water systems are first modelled considering production, distribution, and demand sectors, with a detailed sub--sectorial description. Likewise, the energy system, composed by the supply-side (upstream and power sector) and the demand-side (buildings and transport), also the water system includes processes for water production (rain, seawater, imported water and the desalination plant) and consumption (representing the seasonal and the fixed water demand of the island). Long-term scenario projections of the two systems have been performed separately. .For the energy system, a renewable energy transition scenario has been implemented, while for the water system two scenarios have been assumed: the first one keeps in-situ water production capacity unchanged; in the second one there is no limits on desalination capacities, such that the system is free to choose to import or to produce. At a later stage, the integrated reference energy-water system (WES) has been constructed to study the specific connection points of energy and water systems. The most relevant interconnections are associated to the desalination plants. To provide the best solution for powering the plants, two scenarios have been implemented. The first scenario considers two feeding options: the optimized electricity generation mix or to power the reverse osmosis plants using renewables sources; in the second one the system chooses between plants powered by wind, solar or wave energy. The results of the first scenario demonstrate how optimized electricity generation mix is also the most cost-effective desalination powering alternative, while the second one suggests wind energy supply to be more convenient. The renewables-desalination coupling becomes then a practical example of the importance of an integrated approach. The current TEMOA-Pantelleria model is a concrete implementation of a quantitative water-energy nexus approach and represents the starting point for a more comprehensive CLEW system modeling at regional and national level.