Solar power gets thirsty

I’d love to believe that all renewable energy projects are a great way to generate power without putting a strain on our resources and the planet. Unfortunately, many projects present uncomfortable tradeoffs. The New York Times’ greeninc blog reported recently that utility-scale solar power projects can be incredibly water intensive.

Solar power projects are all about concentrating the energy of the sun, which is, well, hot. The problem is most machinery doesn’t have a limitless tolerance for heat and so must be cooled down. In one common, simple technology called “wet-cooling”, solar thermal projects are cooled with running water. The two projects mentioned in the Times article will use more than a billion gallons of water every year. While this isn’t anywhere near the volumes of water used for agriculture, it’s not a drop in the bucket either: look at the specifics of one particular project.

NextEra Energy Resources, a subsidiary of the utility FPL Group, is developing the Genesis project in the Chuckwalla Valley in the Californian Sonoran Desert. This project. combined with a similar one nearby, would tap about 5 percent of the valley’s available water.

Five percent of the water resources of the local ecosystem is significant, even for an undeveloped desert environment. I’m not saying I’m opposed to solar, but rather that it’s important that we look at all the impacts of these projects and consider other options. In this case “dry cooling” technology uses significantly less water (but costs significantly more). As these projects progress through California’s permitting process, it will be interesting to see how decision makers balance these tradeoffs. It’s a great reminder that no renewable energy project is a silver bullet and that it will take a mix of technologies to address our growing energy demands responsibly.

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13 Comments

  1. Jerry Rickert - November 11, 2009

    Instead of wasting all that water to dissipate heat, can’t a way be found to use that dissipated heat to increase the electricity generated. Sounds like our typical cheap and dirty approach. Charge the real value of the water and I am sure ingenuity would thrive.

  2. Mala - November 14, 2009

    Can someone offer a solution to dissipate heat in places where there is acute shortage of water

  3. Angus Powelson - November 14, 2009

    So right – if only water were priced every at something that reflected its value at a given time….

  4. Angus Powelson - November 14, 2009

    So right – if only water were priced every at something that reflected its value at a given time….

  5. lexiecassidy - November 15, 2009

    Once again, the basic physics prove that small-scale and decentralized is the best way to generate renewable electricity. But it’s so heard to make monopoly profits off a million rooftop grid-tied 5- or 10-KW generators…
    Oh, where is the new generation of engineers? The old ones are so wedded to the power-plant approach that they simply cannot see any other way.

  6. Don - November 18, 2009

    Tell us about water use of coal fired power plants.

  7. Bryan - November 18, 2009

    Jerry, cheap and dirty? It has nothing to do with motive and everything to do with thermodynamics. If you can create the need for lots of hot water in the desert (a big spa?) then you might be able to use some of the low-grade heat; otherwise, it has to be removed from the system in order to generate electricity.

  8. westomoon - November 18, 2009

    Hm, how about a molten-salt-based system for desert sites? See http://www.grist.org/article/2009-11-09-solarreserve-revives-decades-old-solar-power-technology
    As to cooling the existing systems, would a closed-loop water circulating system that did a loop deep underground to lose its heat not do the trick? We just don’t like thinking about that much infrastructure, IMO, and engineers don’t like passive anything.

  9. veek - November 18, 2009

    It isn’t just solar.
    The 23 October 09 issue of Science includes an article by R. Service, showing calculations of water requirements for various means of energy production (given in liters per megawatt hour). Solar was not reported, but oil extraction and refining requires at least 190 L, oil shale retorts require at least 170 L, coal gassification around 900 L, closed loop nuclear plants require between 230 and 30,000 L, and … irrigation for corn ethanol or soy biodiesel would take between 2.3 and 27.9 million L (yes, “million” is not a misprint). Many of those liters wind up in the Gulf of Mexico, where they contribute to further problems (like eutrophication). Some costs could conceivably be managed (you can try to use waste products from existing corn production or locate nuclear plants near river outlets, for example), but some (like depleting aquifers to irrigate crops in the Great Plains) cannot. The article also concludes that some proposals (like modifying corn to use less water) many not make much effective difference.
    FWIW, indirect environmental costs of energy are often ignored by politicians or corporate execs (i.e. wars-for-oil, oil-associated terrorism, etc.) but they are as much a credible part of the equation as easily calculated direct costs (such as carbon emissions). Credible solutions may take time — The Science article appeared several years after we began investing in ethanol — and this may indicate the value of accuracy over speed whenever we can use accuracy, and the price of looking for “quick fixes” when we cannot.

  10. Randy - November 18, 2009

    It is so obvious to me that using wind turbines to generate electricity is the way to go. We should be conducting a massive build out of wind farms, personal windmills like those built by Southwest Windpower out of Scottsdale, AZ., for home use where possible. They are poping up around Maine regulary. Homeowners who have enough capital and are tired of paying Central Maine Power for electricity are purchasing these small units that can actually put excess power generated, back into the grid and receive a monthly check from CMP, instead of paying them. The Govenor of Maine, Balldacci, recently returned from a fact finding mission to Europe where he visited the Spanish owner of Central Maine Power. Shortly thereafter, a conference was held at the Maine Civic Center in Augusta, where I ran into a small group of protesters outside the conference. Intrigued by their oppostion to windmills, I engaged them in a short dialogue. Short because none of them seemed very bright and their oppostion was simply,”not in my backyard, as it were.” They spoke of birds being killed by the rotating blades, the noise they make that would bother them, and lastly the visual pollution.
    I submit to you that every windmill I see is beautiful. The noise of the large fuel tankers that routinely traverse our highways, keep me awake at night, and create a noise much more hideous than the windturbines manufactured by G.E. I stood directly under one, mounted on 220′ poles. There are three of them in the town of Liberty, Maine., and they produce enough electricity to power 2,200 homes.(Ironic, the town being named Liberty). The subjects of birds being killed, probably has some truth to it, but birds have hit my windshield and my picture window and been killed. If we do not do something fast, there won’t be many birds left.
    President Obamam has been spending our children and their childrens money, putting this country in grave financial peril, with a devaluation of the dollar coming, I believe. Let us at least creat a huge number of jobs in creating a power source generating system that has free fuel, once having been built. Let us stop the transfer of wealth to the middle east, a part of the world where most of the people hate us. T. Boone Pickens, to me, is a real American hero! As most of you, are probably aware he has purchased large tracts of land in East Texas and has ordered millions of dollars of wind turbines as HE SIMPLY BECAME TIRED OF WAITING FOR OUR ELECTED OFFICIALS TO DO SOMETHING!
    The protesters at aforementioned conference brought up the subject of visual pollution. I watch the sky near and around Cousins Island Power plant in Casco Bay, Portland Maine, turn the horizon a hideous pinkish gray as the smokestacks spew, Co2 and more carcinogens into our atmosphere. The papermill in Westbrook, Maine creates a smell so hideous it can make you sick. Although that pollution is not from generating electricity per say, the plant would seem less offensive to the local denizens, if its power was from a non polluting source, like the wind.
    You want construction jobs, then let us start by instituting a massive build of windmills, a rebuild of the national power grid so as to more readily accept, access spots, to locations where the windmills must go to harness this states’ wind.(and tidal, geothermal,etc.) Govenor Balldacci’s stated goal is to take the lead in New England by putting up deep water wind turbines as well as on shore ones. I hope he succeeds! He is true visionary and recognizes that the very survival of humanity is at stake. The debate is over. Global warming, Hurricanes like Katrina, the melting polar ice caps, sunamies, are getting worse wityh each passing week! Did you know that the world leader in manufacturing wind turbines is not American? They are Dutch, I believe, the company is called “Vestas”. The Spanish, Chinese, Indians,are all ahead of us! Running near the middle of the top ten is our own General Electic. The owner of CMP, has 5,500 windmills in operation around the globe and can monitor them, switch them on and off according to need and wind conditions, all from one central location. Why are we so far behind in this greenest of green technologies? Why not power our automobiles from power produced by windmills? We have the technology now! Who killed the electric car, by the way?
    SIGNED: An ordinary guy who wants to leave a planet that is habitable for our children and their children. We are doing a horrible job at that endeavor.

  11. Bryan - November 19, 2009

    Westomoon,
    Thanks for the Grist article. The take-away there is that molten salt addresses the storage problem. You still have a steam cycle to deal with. A geothermal sink is a possibility, but the engineering is beyond me. I don’t want to dismiss it out of hand, but you’re talking trying to dump a lot of heat underground. Don’t forget, the deeper you go, the hotter it gets.
    Going further off topic, I wonder what the limits of geothermal for heat rejection. A few geothermal heat pumps here and there shouldn’t be an issue, particularly if some of the heat stored during the cooling season is retrieved during the heating season. But a one-way trip of constantly sending heat into the earth has to reach a limit sometime, at least locally, no?

  12. Susan Kraemer - December 7, 2009

    Don’t let the Heartland Institute put their talking points in your blogs, guys.
    Here’s who was behind that sudden spate of solar thirst stories:
    Fossil-Funded Group Succeeds in Spreading Lies About How Much Water Desert Solar Uses
    Same group started the wind kills birds meme
    and it happened as CA is considering 10 GW of solar. Just signed up 25 GW more gas plants.
    The fact is gas plants use ten times as much and coal and nuclear can use 60 times as much water.

  13. Bryan - December 8, 2009

    Susan,
    I’ll make the same comment here that Peter made in your blog post (that you didn’t address), but in my own words:
    You are not comparing apples to apples. Do you not understand that the steam cycle is the same regardless of the means used to generate the steam? It doesn’t matter if it’s coal, nuclear or CSP, the water requirements are the same for a wet system.
    The report you cite states plainly that a combined-cycle gas plant uses 200gal/MWh while a parabolic-trough plant uses 800gal/MWh. The report goes on to study how using different cooling technologies (air-cooled, wet/dry hybrid) can reduce the water requirement for CSP, but those same technologies are available to any plant, fossil-fueled or solar-powered, that uses a steam cycle.
    You don’t help the cause of advancing renewable energy by setting up straw-man arguments. Your misinterpretation or misuse of the facts in the report makes you look ignorant if not biased.
    Let’s focus on making a strong argument for renewable energy based on the fundamentals (lower GHG emissions, energy independence). Let’s also not be afraid to acknowledge that no energy source is perfect and trade-offs are required. Fighting strawmen is a waste of time.