PHEV/EVs and water - Finally a good article

It seems that the first paper (regarding water for electric vs. gasoline miles) on our work on the "water intensity of transportation" has gotten quite a bit of attention in the media. I've reported on this already, but included here is finally a good and responsible article that properly demonstrates the scope of the issue.

For an example of an article that does a good job, see the following:

ScienceNOW published this article - online today (3/10/08)

Bottom line (I repeat), electric and plug-in hybrid electric vehicles will use more water because people will charge their cars from the general electric grid. This grid is dominated by thermoelectric power plants (coal, natural gas, and nuclear), and these plants consume and withdraw water as part of cooling. To lessen the water impact, we can focus on (1) generating electricity in thermoelectric plants using technology that consumes and withdraws less water and (2) using electricity from sources that don't consume and withdraw water (wind, PV solar).


For examples of articles that do a poor job, see any of the following:

Popular Mechanics

- The quote below is very misleading and incorrect. The water intensity, or gallons/mile, for withdrawal is 17 times greater. This is not a 17-fold increase in water demand, even if all light duty vehicles (cars, trucks, SUVs) ran on full electric power, because water is withdrawn for many other purposes AND if all miles (2.7 trillion) in 2005 were driven on electricity, that would amount to about 900 billion kWh, when the entire nation generated 3,883 billion kWh without any measurable amount of PHEV/EVs. Thus, all light duty vehicle travel by electric miles would be only 23% more electricity (and associated consumption and withdrawal), NOT 17 times more. See misleading quote from article:

"Though most of this water is returned to the source (albeit at a higher temperature), a 17-fold increase in demand would pose a real problem for water-stressed regions, making power plants more vulnerable to shut down during times of drought. "

New Scientist

Chemistry World

- The following quote is completely incorrect. The nation's water consumption (which includes that for irrigation, municipal use, mining, and thermoelectric generation) will NOT triple if we switch to PHEV/EVs. See above comment on the Popular Mechanics article, same argument goes for not tripling nation's water consumption with all electric light duty vehicle travel. See misleading quote from article:

"Michael Webber and Carey King, from the University of Texas at Austin, suggest that powering America's cars with electricity, rather than gasoline (petrol), could triple the nation's water consumption."


Have a good day.

Water for Transportation - publication on "electric miles"

A paper of mine has been published online today in the journal Environmental Science and Technology. The paper describes how much water is used, that means consumed and withdrawn (which are two different concepts) for driving a vehicle on electricity as "fuel". This pertains to electric vehicles (EV) or plug-in hybrid electric vehicles (PHEV) while they travel on battery power alone.

First, two basic definitions:

water withdrawal is that water which is taken from a source, run through a process, and returned to the source or some other source.

water consumption is water that is withdrawn but not returned to the source due to evaporation (for example - in cooling processes for steam power plants) or evapotranspiration (evaporation from through plants).

Due to water consumed and withdrawn for cooling steam electric power plants (coal, nuclear, geothermal, solar concentrated power, and most natural gas), we can associate that water usage with the electricity generated from the plant. Assuming that an EV or PHEV is charged with electricity from the generic U.S. grid, each mile driven by a average light duty vehicle (a car, pickup truck, or SUV) will consume 0.2-0.3 gallons of water and withdraw 8 gallons of water. This is approximately 2-3X more water consumption and 12X more water withdrawal than when driving a light duty vehicle on petroleum gasoline.

Does this mean we should not pursue EV and PHEV technology? ABSOLUTELY NOT.

There are many benefits to the integration of EV/PHEV vehicles which include the ability to use a diversity of fuels sources - anything that can end up generating electricity (burning stuff to produce steam, nuclear power, wind power, photovoltaic solar, etc.). The ability to use a variety of transportation fuels by way of the electric grid is very powerful and important.

While the water consumption and withdrawal is higher than using petroleum gasoline, we can easily plan and accommodate for the increase in water usage per mile. The use of EV/PHEVs will occur gradually, and water resources will not be the limiting factor for their adoption. Full speed ahead for electric cars.