Water Week

EWN Publishing

Benefits of improved technology for seawater desalination wiped out by swift rise of energy costs

Posted by waterweek on 28 September 2007

Great complexities bedevilled the task of getting comparable cost figures for water produced by desalination compared to other water production or savings methods, according to the WWF’s Phil Dickie.

Free land skews analysis: “Such comparisons are usually conducted on the basis of the cost of product water,” wrote Dickie, “with the most efficient (and largest) RO (Reverse Osmosis) plant at Ashkelon, Israel initially producing water at $US 0.52/m3. However, the land for Ashkelon was provided at no cost by the Israeli government, and the Pacific Institute legitimately queried how production costs could be compared with California plants where expensive coastal land was a significant cost factor.”

Subsidies skew analysis too: “However,” Dickie continued, “in turn, the California project most likely to go ahead was quoted as producing water at $US 0.57/ m3 – after subsidy assistance of $US 0.20/m3. In addition to subidies, other issues in comparing desalination plants include varying capital amortization periods and rates. Figures produced by and about the desalination industry accordingly should be treated with a great deal of caution.”

Energy largest component of operating costs: According to Dickie: “What can be said with confidence on desalination costs is that local and site specific factors have a large influence on costs, with energy costs being the major factor. Also important are the salinity and other characteristics of the feedstock water, coastal land costs and costs of mitigating environmental impacts. Energy costs are the largest component of the operating costs of desalination plants. On 2003 estimates by the US Bureau of Reclamation, energy accounted for 44 percent of the ‘typical’ costs of an RO (Reverse Osmosis) desalination plant and close to 60 percent of the costs of a ‘typical’ large thermal distillation plant. The energy proportion of total costs rises with energy costs.”

Desalinated seawater an expensive option: “Desalinated seawater is expensive water compared to most alternatives in most locations,” Dickie wrote. “To some extent the high cost of desalinated water can be offset by the greater reliability of supply. However it has not generally been economic to maintain sizeable desalination plants as a reserve capacity to be activated as needed in times of drought. Rising energy costs are now counteracting or overwhleming the benefits of incremental improvements in desalination technology. This is a trend that is likely to continue.”

Reference: Phil Dickie, WWF for a living planet, ‘Making Water – Desalination option or distraction for a thirsty world?’, June 2007.

Erisk Net, 23/9/2007

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