What is sustainability – water use in energy generation

20130403-183924.jpgWater use has been a favourite topic of mine recently, whether it was about the water footprint of our daily food intake or the idea of virtual water.

I also posted some time ago about a dubious use of water to make energy from a giant shower in the desert, calculating that it would need some 2 swimming pools of water an hour. But I came across some data from Arizona State University that showed that all forms of power generation consume water in the production of energy.

Water is one of our most precious resources, and we know instinctively that we need it to grow food but the extent to what we need it for energy generation was a surprise to me.

The data:


Gallons / MWh



Solar CSP






Natural Gas 




Solar Photovoltaic




Wow, that is a lot of water!

The crazy shower tower scheme in the desert would consume about 900 gallons / MWh, so solar CSP and Hydro are as bad or worse than the shower tower!

So, how does water get used in energy production?

Well, in hydropower it is lost through evaporation from reservoirs and rivers. In solar CSP it is used to generate steam to drive a turbine. In nuclear it is used for cooling. In coal and gas power stations it is used for cooling. In solar PV it is used for washing the panels.

Now the problem with using embodied water in assessments is that, as was pointed out to me recently, the water used evaporates into the atmosphere where it falls as rain and completes the cycle. So water isn’t like coal or gas where once you have used it it has gone forever. But in times of drought how we use the water before it evaporates into the atmosphere is vitally important.

When faced with drought (water shortage) would you rather have a water efficient power generation system (PV and Wind) and keep the water for drinking and food or stick with water inefficient power generation? I know wish I would chose.

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