At the Confluence of Water Use and Energy Production

Table comparing water use per million Btu of various energy supplies

On my commute on the NYC subway this morning (which by the way I discovered is decreasing in carbon intensity), I came across this New York Times story, "Alternative Energy Projects Stumble on a Need for Water" by Todd Woody that described the problem of water resource scarcity in driving potential new development of concentrating solar power (CSP).  CSP technologies show much promise as a relative low cost renewable energy resource that can tap into the very sunny American Desert Southwest.

One of the key takeaways from the article is on water scarcity shaping new technology development:

Conflicts over water could shape the future of many energy technologies. The most water-efficient renewable technologies are not necessarily the most economical, but water shortages could give them a competitive edge.

The article goes on to give dimension to the size of the CSP market under consideration and the amount of water that some projects will require:

In California alone, plans are under way for 35 large-scale solar projects that, in bright sunshine, would generate 12,000 megawatts of electricity, equal to the output of about 10 nuclear power plants. ...

Their water use would vary widely. BrightSource Energy's dry-cooled Ivanpah project in Southern California would consume an estimated 25 million gallons a year, mainly to wash mirrors. But a wet-cooled solar trough power plant barely half Ivanpah's size proposed by the Spanish developer Abengoa Solar would draw 705 million gallons of water in an area of the Mojave Desert that receives scant rainfall.  [I have included more numbers on these projects below.]

Our sentiments on this issue are captured well by one of our closest policy advisors quoted in the piece:

Daniel M. Kammen, director of the Renewable and Appropriate Energy Laboratory at the University of California, Berkeley, predicted that as intensive renewable energy development spreads, water issues will follow.

"When we start getting 20 percent, 30 percent or 40 percent of our power from renewables," Mr. Kammen said, "water will be a key issue."

However, contrary to the implicit "newness" of the water-energy issue conveyed by this NY Times article, water quantity and quality issues have long been at the center of all the various fuels and associated technologies of our energy supply (and making energy efficiency and conservation all the much more valuable).

Broadening the perspective of comparing water use for energy production, the Virginia Tech University Virginia Water Resources Research Center recently did a report giving an "apples to apples" comparison of water quantity required to produce energy from various energy sources (see figure below).  Conventional fossil fuel require anywhere from 5 to 8 times as much water per million BTU of energy produced.  Nukes come in even higher, ranging from 10 to 20 times as much water required to produce a million BTU than CSP (termed "solar thermoelectric" in the table below).  


How do the proposed projects in the NY Times article compare?  From my rough calculations,

BrightSource Energy's Ivanpah project will have 440 MW capacity and using 25 million gallons/year; (assuming a 25% utilization rate) the water 'efficiency' comes out to 76 Gallons per MMBtu.

Abengoa's Mojave project at 280 MW capacity will plan to use 705 million gallons of water/year; (Assuming a 25% utilization rate) the 'water efficiency' comes out to 3,369 Gallons per MMBtu.

Lastly, on the topic of scale in looking at water use and energy prodcution, my colleagues from our Nuclear Program would like you to keep in mind:

  • "Nearly two out of every three gallons of freshwater withdrawals in the Southeast are sent to electric power plants to meet cooling water demands.  About a gallon of water is consumed for each kilowatt hour (kWh) of electricity produced."  Reported by our advocacy partners at the Southern Alliance for Clean Energy (SACE).
  • Union of Concerned Scientists reported on the water quantity and water quality impacts from the 104 existing nuclear power facilities throughout the U.S.
  • "How the Nuclear Power Industry destroys endangered marine wildlife and ocean habitat to save money"

The confluence of water and energy resources issues will continue to be very important to us as we look to develop non global warming-polluting, renewable energy technologies.  But it is also important not to lose sight of the 'big picture' that some energy resources use significantly more water per unit of energy produced than others.