Reverse osmosis-plant
Reverse osmosis-plant.
Photo credit: James Grellier

1.8 billion people are predicted to live in areas of extreme water scarcity by 2025. As drinkable water reserves are getting scarce and population increases globally, desalination, a process that derives freshwater from sea or brackish water, is becoming more and more widespread.

But before desalination can make a real contribution to water availability, several obstacles that make the process expensive and inefficient need to be overcome. Indeed high costs have been one of the principle reasons why desalination has been mainly used only in countries with high water scarcity and relatively inexpensive energy such as Saudi Arabia or the United Arab Emirates.

In general there are two types of desalination technologies – energy intensive thermal based, that involves phase change of water; and a less energy intensive membrane based process that presses salty water through ultra-thin, semipermeable membranes. Currently, reverse osmosis (RO), a membrane based process accounts for 60% of the global desalination-based water production. However, a typical reverse osmosis plant can still spend up to 40 percent of its overall operating costs on electricity.

Research conducted by the International Water Management Institute (IWMI) is looking at the high costs of energy use in desalination technology. The results of the study were presented at the Water in the Anthropocene conference which is taking place in Bonn this week. The researchers attempted to answer the question of whether desalinated water, will ever become affordable through technological innovation and the use of clean energy. They also asked how soon this might happen.

“We examined historical trends in desalination and broke up the costs involved into energy-based and non-energy-based”, explains IWMI researcher Aditya Sood. “Assuming that photovoltaic (PV) will become the dominant form of energy used for desalination, we explored the possibility of its large-scale adoption in the future.”

Based on historic data, relationships were developed between the production levels and cost of production for desalination. It is well known that with newer technologies, as the scale of operations grows and technologies develop, the cost goes down. In this case, the results show that, if energy is not a limitation, desalination technology has reached a stage where it can provide water for the domestic and industrial sectors with between 1 to 8 doublings of its global production by 2020 or 2030, depending on the region. From an energy perspective, however, global production rates of PV will have to increase further (9 to 12 doublings by 2040) to bring prices down to an affordable level; even more so for sub-Saharan Africa and South Asia (20 doublings). Overall the global PV production will have to grow by 1 million MW per year to meet the projected demand except for sub Saharan Africa and South Asia. Similarly, without energy constraints, desalination can meet the water demand affordably except for sub-Saharan Africa, Eastern Europe and Central and South Asia. For these regions, to bring the cost down, the global capacity of desalination needs to increase at a rate of 31.8 (sub-Saharan Africa), 3.7 (Eastern Europe and Central Asia) and 56.3 (south Asia) million m3/day annually.

“Our analysis has shown that the future of desalination to meet increasing water demands looks promising”, says Sood.  “But how fast the future growth in production takes places will depend on the investment made in this sector. Exact predictions are difficult to make as there are many other players, such as political will and water use efficiency that would influence the development of desalination technology. Also costs related to environmental issues need to be taken into account and have not been considered in this study.”

Water in the Anthropocene: Challenges for Science and Governance. Indicators, Thresholds and Uncertainties of the Global Water Systemis taking place at the Maritim Hotel Bonn, Germany on 21-24 May 2013. The focus of the conference is to address the global dimensions of water system changes due to anthropogenic as well as natural influences. It is organized by the Global Water System Project.


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