Clean Power

Published on October 14th, 2013 | by Giles Parkinson


World’s Largest Solar Thermal Plant With Storage Comes Online

October 14th, 2013 by  

Originally published on RenewEconomy

solanaConcentrated solar thermal is again making the news, with the world’s largest parabolic trough array with thermal storage – opening for business in Arizona.

The 280 MW Solana Generating Station constructed by Spanish group Abengoa has six hours of molten storage capacity that will allow it to produce energy into the evening, and deliver output according to the needs of the customer.

“Solana is a monumental step forward in solar energy production,” said Don Brandt, the president of APS, the local utility. “This provides a huge boost toward our goal to make Arizona the solar capital of America.”

The opening of Solana is one of three major new projects that are coming on stream, as CSP begins to recover the ground lost, and projects ceded, to solar PV when that technology delivered massive cost reductions in recent years.

The 375 MW Ivanpah project, the largest solar power tower in the world, has delivered to the grid for the first time and is due to start full operations within the next few months, as is the 110 MW Crescent Dunes facility in Nevada, which will be the world’s largest solar power tower project with molten salt.

Also, the first commercial scale solar thermal plant with storage, the Gemasolar plant in Spain, recently marked its second anniversary by delivering electricity 24/7 for 36 consecutive days. On Thursday, Dr Keith Lovegrove, the head of solar thermal at Australia’s IT Power, said CSP with storage is ”virtually unbeatable” as a technology, and the costs are coming down quickly.

The Solana plant’s CSP technology produces electricity by collecting the sun’s heat to create steam that turns conventional turbines. It has 2,700 parabolic trough mirrors,which follow the sun to focus its heat on a pipe containing a heat transfer fluid.

This fluid, a synthetic oil, can reach a temperature of 735 degrees Fahrenheit. The heat transfer fluid then flows to steam boilers, where it heats water to create steam. The steam drives two 140 MW turbines to produce electricity, much like a traditional power plant.

APS says that shat separates Solana from other solar power plants is the ability to store the heat from the sun up to six hours for electrical production at night. In addition to creating steam, the heat transfer fluid is used to heat molten salt in tanks adjacent to the steam boilers.

The thermal energy storage system includes six pairs of hot and cold tanks with a capacity of 125,000 metric tons of salt, and the molten salt is kept at a minimum temperature of 530 degrees Fahrenheit.

When the sun goes down, the heat transfer fluid can be heated by the molten salt to create steam by running it through the tanks instead of the field of parabolic mirrors.

APS says this means that Solana can deliver power whenever its customers need it most, including evenings.

The opening of Solana boosts the solar capacity operated by APS to more than 750 MW. It as 1.1 million customers.

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About the Author

is the founding editor of, an Australian-based website that provides news and analysis on cleantech, carbon, and climate issues. Giles is based in Sydney and is watching the (slow, but quickening) transformation of Australia's energy grid with great interest.

  • ArtaGene

    I somehow missed this type of technology, was reading an article about home cookers using this salt storage…..same unit could be used to heat home at night or cook with after the sun was gone.
    Not much information on return on investment, so other than it is “Green” hard to decide how effective or who and how it will be used.

    • gellero

      if it worked, the Chinese would have done it a decade ago….

  • 24/7 solar plants must be a nightmare for the coal industry. I wonder if they are lobbying to make them illegal in the states…

    • OnceTwice


    • gellero

      if you actually studied physics you’d know how ridiculous that statement is…..

      • Bob_Wallace

        If you were paying attention to what is happening in the coal business you’d know how ridiculous that statement is…..

        Thermal plants (coal and nuclear) are getting killed by PV solar. The profitable peak hours are going away as only modest amounts of solar come on line. Take a look at what has happened to the price of electricity in Germany.

        Now look at the remaining peaks. Thermal solar with storage can grab those peaks and further whack coal.

        And, do remember, wind is tearing up off-peak profits for traditional generators.

        (That last graph, Disqus doesn’t let one delete mistakes.)

  • Marion Meads

    So far, amongst the other design layout that I have seen, they have more densely packed solar interceptors and don’t waste a lot of land compared to other designs. It could be packed some more and the overall land use and utility efficiency increased. Densely packed means not a lot of sunlight go to waste, and you use shorter amount of piping which help cut down on cost and minimizing energy loses too while not wasting a lot of land for nothing.

  • Jouni Valkonen

    The cost of solar plant is two billion dollars. The projected annual generation is 944 GWh. As the nominal output is 280 MW we get 38% for capacity factor. If we assume 20 year investment period, then the capital costs are $160 per MWh, including 4% annual interests. This does not include operating and maintenance costs which are presumably low.

    I wonder what would be the cost of solar PV + battery storage? Perhaps it is $250 per MWh. But I assume that solar PV + natural gas would be cheaper.

    • Ivor O’Connor

      All articles should include a basic set of details similar to what you have included. All the way down to the PPA. Perhaps along with current PPA pricing of other plants in the area. RE is nice but RE because it is the best financial solution is nicer.

    • Morgan

      I think in a lot of ways it is meant to take the strain off of Palo Verde our nuclear power plant and normal power plants. Arizona is gaining a lot of people from California. We need the power.

  • AegysLTS

    “The thermal energy storage system includes six pairs of hot and cold tanks with a capacity of 125,000 metric tons of salt”

    125,000 tons!….thats an entire ship…

    • Marion Meads

      Only one ship? I was hoping for a fleet size thermal storage.

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