Economic assessment of renewable energy systems integrating photovoltaic panels, seawater desalination and water storage

This paper presents a novel methodology for the management of the solar energy and seawater desalination, using water storage systems. The investigated plant includes photovoltaic panels, supplying a reverse osmosis unit for freshwater production. This novel methodology, based on the use of a water storage basin, allows one to avoid electric storage systems, determining a stable water production and maximizing the water self-consumption. The water storage basin allows one to obtain a significantly different trend of the freshwater availability with respect to the photovoltaic production, mainly occurring during the central hours of the day. The plant is dynamically simulated in TRNSYS environment. The proposed plant is assumed to operate in small Mediterranean islands, rich in solar energy and seawater availability, featured by a scarce freshwater availability and dramatically high freshwater costs. As main case study, Pantelleria Island (South Italy) is selected. The system energy performance is calculated in detail implementing accurate models for all the system components. Special control strategies are implemented in order to maximize the system profitability, evaluated by considering both capital and operating costs. The developed system is extremely profitable: the achieved payback period is about 1.3 years, mainly due to high capital cost of freshwater in the reference scenario. A remarkable water saving equal to 80% is obtained, also reducing the dependency of the Island from the water transported by the tank ships. For the selected case study, the sensitivity analyses suggest adopting a solar field area equal to 6436m2, avoiding an increase of the water storage basin and of the maximum and minimum operating pressures of the reverse osmosis unit single train.