Sustainable desalination: integration of power supply with renewable energy sources

The production of fresh water through the desalination of brackish water or seawater looks a reliable solution to satisfy the water needs of human settlements in areas with enduring water scarcity. However, when a desalination plant is called to work with large seasonal fluctuations in fresh water demand, as in areas with a strong tourist season, daily and seasonal variability of water demand mismatch with the usual needs of plants operation which ensure the maximum efficiency and the minimum cost of desalinated water. In addition, the necessary intake devices for all these technologies have always an impact on the area where the plant is installed also in terms of chemicals use, concentrated brine release. The proposed case study concerns the Asinara Island, whose entire surface and coastal area is now a national park. In this context the paper analyses the complexity of desalination plants design and operation for a respectful use of the soil and a wide seasonal swing of water demand. It aims at selecting the most energy efficient solution endowed with a good sustainability by obtaining power with renewable sources of energy [1],[2]. The analysis is further developed taking into account the impact of governance actions aiming at a more responsible use of water resources, including the reuse of wastewater of sewage for irrigation. A mathematical model is presented and applied: it allows to analyse the integrated system performance to search for the optimum solution, once the time trends, statistical water demand and renewable energy sources (wind, solar) availability, the features of the desalination system (Reverse Osmosis or Mechanical Vapour Compression), the capacities and catching areas of the basins have been defined and calculated.