How much does it cost to build a desalination plant?

How much does it cost to build and operate a desalination plant and how much does desalted water cost?

I’m increasingly coming to the conclusion that this question is tricky to answer. I’m conscious that when I see figures presented at the IDA World Congress I’ve always got to think and question what’s actually being presented. The cost of water is usually valued in volumetric terms, X number of dollars per metre cubed of the stuff, but are we necessarily comparing like with like?

Where is this cubic metre? Is it as delivered to your house or is it at the point of production?

Does the production cost reflect the capital and/or operational costs of the desalination plant? Where is the energy from? Are any of these component costs subsidised? Are we comparing like-for-like quality for our cubic metre?

Robert Huehmer’s presentation, titled Cost Modelling of Desalination Systems, answered some of these questions.

He notes that for the cost of a coffee you can have the equivalent of a week and a half of desalinated water. Maybe the coffee is too expensive? Getting the cost of desalination water right is an important element in the design, build and operation of the plant: get the estimate wrong, or carry too much contingency and the economic performance of the business is compromised.

Uncertainty is everywhere. Some are tangible, most are probabilistic, but the goalposts can change and Huehmer notes that historical baseline values can change – energy, interest rates, land values, subsidy and even currency devaluation. Is it any wonder when I ask around the Hall about the opportunity-risks for desalination in southern Africa I hear very cautious answers?

Cost Models provide a means for project managers to begin to make sense of the economics although I like the idea of ‘The Swag’ – phone a friend! – is right up there in terms of predictive performance.

Twitter link duly noted! http://t.co/wziOhSV

Note to self >>> investigate subsidies and the extent to which desalination is supported (or otherwise) by cost externalities…