Resumen
The use of photovoltaics (PVs) to power reverse osmosis (RO) desalination can potentially break the dependence of this desalination process on conventional energy sources (oil, coal, electricity from national grid), reduce operational costs, and improve environmental sustainability. In this paper, a methodology for the optimal sizing and performance evaluation of a stand-alone PV system to power an RO desalination unit is presented. This unit covers the water needs of inhabitants of a small isolated village called Mrair-Gabis, near the Ajdabiya city in north-eastern Libya. A photovoltaic-reverse osmosis (PV-RO) system offers good possibilities for satisfying this need. Due to the many technical problems with batteries, as well as their high cost, the system studied in this paper will not consider the use of batteries; the viability of a batterryless system is facilitated by the high solar radiation at the selected site, and long daily average insolation duration. From the water consumption records it was noticed that during some days in summer the water produced by the RO unit does not meet the water demand; on the other hand, during some days of the month there will be an excess of water production. The above considerations led to the design of a freshwater tank, to cover the potable water needs for people in cases of the desalination unit breaking down, either due to technical problems or on the cloudy days. The purpose of the water tank is therefore to store excess water when production exceeds supply. Simulations were carried out using MATLAB Software to size and assess the performance of a stand-alone PV system. The computer program can be applied to any site with different weather conditions.