Seite - 167 - in Clean Water Using Solar and Wind - Outside the Power Grid

Water operations using renewables – some cases 167 Example 14.3: Abu Dhabi The United Arab Emirates (UAE) is considered a “water-scarce” country. It has just 83 m3 of water per person per year – well below the UN scarcity threshold of 1,000 m3. As a consequence, UAE relies to a large extent on seawater desalination to satisfy the demand for water supply. Mascara Renewable Water has developed an off-grid, solar- powered desalination solution in Abu Dhabi (Masdar, 2018). The plant uses a beach well to obtain seawater from a borehole near the sea. The natural sand filtration of the beach well eliminates the need for a dedicated pre-treatment system. The intermittent power production is compensated for by a hydraulic energy accumulator used as storage. The system is powered by a 30 kWp PV plant, and the system operates only during sunlight hours, producing 30 m3/day. Biofouling is avoided by automatically flushing the membranes before sunset every day. A number of identical desalination plants have been designed, based on solar energy and located in isolated desert areas of Abu Dhabi, outside the power grid. A typical solar system is built up of 300 m2 panels that will produce a maximum of 45 kW, in other words 150 W/m2, which is in the same order of magnitude as described in Chapter 8. The first installation was completed in 2009. The desalination plants designed by Hitachi are pumping saline groundwater and applying reverse osmosis to clean the water. The salinity ranges from brackish water to 35,000 mg/l, similar to seawater. The production of the system is 4 m3/hour of fresh water. The groundwater is first pumped to a storage tank before treatment in the RO unit. Even in a sunny area like the Abu Dhabi desert the sunlight may be shaded during the day, for example due to sandstorms. Therefore, a battery backup is provided. There is an evaporation pond, designed to get rid of the brine reject (see 5.3.4). Example 14.4: Gran Canaria, Spain A solar PV-powered system for the desalination of seawater, called DESSOL, has been installed close to the beach on Gran Canaria (Espino et al., 2003). The desalination system is based on RO and produces an annual average flow of 3 m3/day (or 0.4 m3/hour) during Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user