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Power Science Technology

Largest US Power Storing Solar Array Goes Live 377

Posted by samzenpus
from the here-somes-the-sun dept.
Lucas123 writes "A solar power array that covers three square miles with 3,200 mirrored parabolic collectors went live this week, creating enough energy to power 70,000 homes in Arizona. The Solana Solar Power Plant, located 70 miles southwest of Phoenix, was built at a cost of $2 billion, and financed in large part by a U.S. Department of Energy loan guarantee. The array is the world's largest parabolic trough plant, meaning it uses parabolic shaped mirrors mounted on moving structures that track the sun and concentrate its heat. A first: a thermal energy storage system at the plant can provide electricity for six hours without the concurrent use of the solar field. Because it can store electricity, the plant can continue to provide power during the night and inclement weather."
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Largest US Power Storing Solar Array Goes Live

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  • Re:6 hours? (Score:4, Informative)

    by djupedal (584558) on Thursday October 10, 2013 @07:25PM (#45097249)

    Nighttime lasts longer than that.

    RTFA - "These six hours will satisfy Arizona's peak electricity demands during the summer evenings and early night time hours . . "

    Someone do the math. $2 bil over 30 years for 70k homes.

  • Re:6 hours? (Score:4, Informative)

    by mythosaz (572040) on Thursday October 10, 2013 @07:36PM (#45097325)

    In Arizona, we use most of our power during the day, cooling homes.

  • Re:6 hours? (Score:5, Informative)

    by bob_super (3391281) on Thursday October 10, 2013 @07:45PM (#45097401)
    Economics. You don't need nearly as much power between midnight and 6 (7? 8?), during which time the nukes and coal, which can't be throttled too much, will oblige. Designing heat storage capacity for around-the-clock is wasting money, at least in the current grid configuration and state of the tech.
  • Re:6 hours? (Score:5, Informative)

    by Frobnicator (565869) on Thursday October 10, 2013 @07:50PM (#45097435) Journal

    Yes, night is longer than the 6 hours mentioned in the story summary. But the story summary is a bit misleading.

    That is six hours running at full capacity and also running entirely from the salt tanks. Neither of those conditions are likely to be true overnight.

    Solar plants continue operating at reduced power during cloud cover and at night time. Even at times of reduced sunlight or at night there is still energy available. It does not need to run entirely from the salt tanks.

    Secondly, nighttime is not peak usage hours.

    The Solana salt tanks are about 740 cubic meters so they could probably store around 16TJ of energy. (For physics impaired, 1 joule per second == 1 watt.) That is a lot of power. Since it will mostly be relying on that stored energy at night and not running at full capacity, that stored energy could reasonably last through the night and on through a good portion of the following day.

  • Re:14c/kWh (Score:4, Informative)

    by mythosaz (572040) on Thursday October 10, 2013 @07:51PM (#45097443)

    Most of the other Arizona plants under construction are already committed to sell solar to PG&E, so... ...wish granted.

    http://en.wikipedia.org/wiki/Mesquite_Solar_project [wikipedia.org]
    http://en.wikipedia.org/wiki/Agua_Caliente_Solar_Project [wikipedia.org]

  • Re:WTF (Score:5, Informative)

    by icebike (68054) on Thursday October 10, 2013 @08:09PM (#45097531)

    Well after sunset?

    Actually, when you read up on it, the storage capacity is exhausted shortly after sunset. 6 Hours max.
    The efficiency falls off at low sun angles.

    Sunset usually happens right at peak demand time, evening cooking, and late afternoon air conditioning.
    Plus the site has high ground to the immediate west, sunset comes earlier for them.

    Don't get me wrong, this is an impressive feat of engineering.

    It was installed very fast, hacked out of prime farm land (or as prime as it gets in Arizona).
    Google Maps Satellite view, with imagery dated 2013 http://goo.gl/maps/Qh7e5 [goo.gl] shows nothing
    but desert with truck roads laid out, and now they are up and running.

    (Either that or Google is Playing Fast and Loose with image dates, because Google Earth shows the same
    images but has a 2010 date on them)

  • by jklovanc (1603149) on Thursday October 10, 2013 @08:38PM (#45097675)

    According to this [seattle.gov] it is a bit lower than that at about 94.2%. It is also a bit skewed by the fact that Seattle is close to mountain ranges with lots of valleys that can produce hydroelectric power. If you remove the hydroelectric, 89.8% the percentage drops to 4.4%.

    Not everyone lives in an area that has plentiful hydroelectric generation. It is like Arizona touting how much solar based electricity they are generating and slagging Seattle for falling behind.

    Meanwhile, I just shelled out $150 to buy one unit of the Seattle Aquarium solar panel array, which will reduce my annual already green electric bill by about $46 until around 2035.

    That is only because you are getting credited for $1.15/KWh [slashdot.org] when electricity sells locally for $0,0672. You are being paid over 17 times the going rate. Making money due to tax incentives really skews the picture.
    By the way according to Seattle Power [seattle.gov] the credits amount to "an estimated annual credit of almost $29 per solar unit"
    I really don't think comparing a highly subsidizes small , 49 kW, project with al large commercial project is very valid at all.

  • Re:WTF (Score:5, Informative)

    by icebike (68054) on Thursday October 10, 2013 @08:52PM (#45097731)

    shortly after sunset. 6 Hours

    Those education cuts really did hurt :(

    The efficiency falls off at low sun angles.
    It falls off faster for solar hotwater (like this plant) than for photo-voltaic.
    You start drawing on your stored heat WELL BEFORE sunset, usually several
    hours before sunset, because as I pointed out that is the peak demand period, and your
    storage is exhausted in 6 hours, from the time you start drawing.

    So maybe two or three hours after sunset your storage is exhausted.
    Its a long time till sunrise.

  • Re:6 hours? (Score:5, Informative)

    by dbIII (701233) on Thursday October 10, 2013 @09:05PM (#45097775)
    Base load is the easy stuff in power generation. The peaks are vastly greater than the minimum demand at night.

    this system is more expensive to build and operate than a photovoltaic system would be

    Not at large scales. PV does not scale well since if you double the size you only double the output. With thermal solutions of all types you can get a lot more heat out of stuff if you have a lot of hot stuff, so doubling the size gives you more than double the output due to an increase in the amount of energy you can get out. For example, if you don't have much steam you can only have a high pressure turbine but if you have a lot you can use the leftover steam that comes out of the first turbine and feed it into another with a different blade pattern to extract more energy and so on.
    With thermal it has to be big so you have an enormous capital cost, but if it's big enough PV just will not match it. A 500MW PV array would cost a vast amount more than a 500MW thermal solution.

  • Re:pricing (Score:4, Informative)

    by Xyrus (755017) on Thursday October 10, 2013 @09:08PM (#45097783) Journal

    Covering your home in solar panels in Arizona can save you about $100/mo on your power bill, which for a single-family-residence runs about $200 in the winter and about $400 in the summer.

    Those panels aren't free. They can take 10+ years to pay for themselves.

    You're wrong. A 9 kw system (which fits on the average roof in Arizona) produces enough power to cover the average home's electricity usage for the year. The break even point is 10 years.

    [citations]
    http://www.eia.gov/consumption/residential/reports/2009/state_briefs/pdf/az.pdf [eia.gov] (Information about average power usage in Arizona)
    http://www.solar-estimate.org/ [solar-estimate.org] (solar system calculator for sizing systems, panel and installation costs, break-even points, etc.)

  • Re:14c/kWh (Score:5, Informative)

    by elashish14 (1302231) <profcalc4@gma[ ]com ['il.' in gap]> on Friday October 11, 2013 @12:35AM (#45098627)

    Unfortunately, the link you posted doesn't mention the timescale for energy generation. I am under the impression that, like nearly all solar energy technology, that the primary cost is up-front installation, and maintenance costs are virtually zero thereafter. Using this assumption, we have

    price / kWh = 2 (billion $) / (280 MW * t)

    This gives t = (2 billion hours) / (280e3 * [100 * price in cents/kWh]) as the amount of time it would take to break even, or with some simplification, 81.485 years / P where P is the price in cents / kWh at which you wish to sell.

    So if you were to sell at $.07 / kWh, it would ideally take 11.64 years to recoup investment (not taking into account additional costs and possible fluctuation in energy output). At double that price, it will take half the time. Either way, after that, I would say it's free energy. I don't see why there aren't more projects like this.

  • by rsborg (111459) on Friday October 11, 2013 @01:36AM (#45098851) Homepage

    Unless there are some nuclear reactions going on in there, I really don't think it is creating any energy at all, much less "creating enough energy to power 70,000 homes".

    Solar energy converts energy from the nuclear reactions in the sun into electricity. Ok, conversion.

    Hydroelectric - captures energy stored from gravitational potential energy and converts it using a turbine into electricity. Fine, conversion again.

    Coal/Nat. Gas - takes stored energy in the form of deposits of oil, coal and natural gas and uses them to drive turbines... oh, you get the picture. Check, conversion of energy again.

    Clearly nuclear energy reactions "create energy" - no wait, it's converting stored energy in the form of nuclear bonds into radiation, which can then be captured as a heat energy which can then drive a steam turbine turning into electricity.... uh... huh.

    Conversion is all we can do apparently. We might want to thank/curse this lousy law [1] .... who's with me for repeal?!?

    [1] http://en.wikipedia.org/wiki/First_law_of_thermodynamics [wikipedia.org]

  • Re:WTF (Score:5, Informative)

    by AmiMoJo (196126) * <mojo@NOspaM.world3.net> on Friday October 11, 2013 @04:04AM (#45099329) Homepage

    No, TFA clearly says that it can run for 6 hours after sunset, not six hours from some indeterminate point where the sun reaches a low angle before sunset.

    Anyway, peak time is during the day, not the evening. It's when people need air-con and industry is active. In the evening it gets cooler and commercial buildings shut down.

    You also make the classic mistake of judging the technology as if it were the only source of energy, which of course it isn't and was never intended to be.

  • by wytcld (179112) on Friday October 11, 2013 @08:45AM (#45100353) Homepage

    A loan guarantee is not financing. The DOE has provided no money. The financing is from private institutions.

    The loan guarantee means the private institutions get paid even if the project fails, true. But why should the project fail? This is proven tech that's cost competitive. It would take some true catastrophe for the loan guarantee to ever be called on.

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