Page - 75 - in Clean Water Using Solar and Wind - Outside the Power Grid

Water treatment 75 (>100,000 m3/day) is 0.91 USD/m3 (3.3 Emirati dirham AED/m3), compared to the current average water production cost of 1.42 USD/m3 (5.16 AED/m3) (Masdar, 2018). Energy is the largest variable cost for seawater RO (SWRO) plants, varying from a third to more than half of the cost of produced water. According to Voutchkov (2016) there are no major technology breakthroughs expected in the next few years to dramatically lower the cost of seawater desalination. However, there is a steady reduction of production costs and technology advances. As Table 5.3 demonstrates, the cost will decrease significantly in the next few years. Table 5.3 Reverse osmosis costs for medium and large best-in-class projects (Voutchkov, 2016). Year 2016 By 2021 By 2035 Cost of water USD/m3 0.8–1.2 0.6–1.0 0.3–0.5 Electric energy use kWh/m3 3.5–4.0 2.8–3.2 2.1–2.4 As mentioned, the source of energy, the water source salinity, the plant size and cost of land are factors that will affect the desalination cost. Typical desalination costs can vary from 0.5 to 3 USD/m3. Example 5.1: Required Power for Small-Scale Desalination Assume that we wish to produce 1 m3 of desalinated seawater per day. To be conservative, this will require 8 kWh using RO technology. Assuming that a solar PV-based array can deliver power for six hours, this will require an electric power of 1.3–1.4 kW. In a subtropical or tropical country, a solar array of 2 kWp would be sufficient to provide this average power during the day. If the plant were downsized to 0.1 m3 per day the required power would be 0.2 kWp. 5.3.6 Operation and maintenance issues There were some important lessons learnt from early installations of RO desalination powered by renewable energy (Cipollina et  al., 2015). Solar PV will only produce electric power in daylight. This has Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user