They may not be gas-guzzlers, but electric cars have a raging thirst for water.
A comparison of the volume of coolant water used in the thermoelectric power plants that provide most of our electricity and that used in extracting and refining petroleum suggests that electric vehicles require significantly more water per mile than those powered by gasoline.
The findings could bode ill for drought stricken areas in the event of a large scale switch to plug-in vehicles.
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鈥淚 wouldn鈥檛 sound the alarm that this is going to ruin the day,鈥� says from the University of Texas, Austin, US, noting that no mass-market electric vehicle is currently available. 鈥淏ut looking into the future, this is something we should take into account.鈥�
Dry cooling
King and colleagues found that cars, light trucks, and SUVs running off the electric grid consume three times more water and withdraw 17 times more water per mile than their equivalent gasoline-powered vehicles.
For electricity generation, 鈥渃onsumed鈥� water is the amount of water lost to evaporation whereas 鈥渨ithdrawn鈥� water is the amount of surface water a power plant uses and later returns to its source, typically a nearby lake or river.
King says one way to mitigate water-use impacts of electric vehicles is by switching to dry cooling 鈥� using forced air instead of water to cool steam in power plants. The technology has been around for years but remains more expensive than water cooling; something King says could change as available surface water becomes more scarce.
Another alternative is to move away from thermoelectric energy sources such as coal, nuclear, and natural gas, to renewable sources. 鈥淚f we use only wind or solar energy, water use would be essentially zero,鈥� King says.
鈥楳odest impact鈥�
Paul Denholm of the US Department of Energy鈥檚 National Renewable Energy Laboratory in Golden, Colorado agrees that water scarcity will become an increasing problem for utilities, but he doesn鈥檛 think electric vehicle usage will have much of an impact.
鈥淎s electricity demand increases in general, water requirements 鈥� especially in drought prone areas 鈥� will become increasingly important,鈥� Denholm says. But 鈥渢he overall impacts of plug-in vehicles are modest in the larger scheme of things鈥�.
Denholm co-authored a based on data from Colorado showing that if 30% of gasoline-powered vehicles were replaced with plug-in hybrid electric vehicles getting 39% of their energy from the grid, the region would experience only a 3% increase in total electricity demand.
The current infrastructure could easily handle this increase because most vehicles would be charged overnight during off peak hours.
鈥淚t鈥檚 going to be several decades before we see enough plug-in vehicles to have any kind of impact,鈥� Denholm says. 鈥淚t鈥檚 hard to say if the grid we have now will be the same grid we have when we begin to see a large number of plug-ins.鈥�
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