Solar power when the sun goes down — with help from United Technologies

Concentrated solar thermal with storage (aka solar baseload) remains “The technology that will save humanity.”  And we are seeing more and more plants in various phases of construction (see “World’s largest solar plant with thermal storage to be built in Arizona “” total of 8500 MW of this core climate solution planned for 2014 in U.S. alone“).

The easiest way to deal with the intermittency of the sun is cheap storage “” and thermal storage is much cheaper and has a much higher round-trip efficiency than electric storage.  The ability to provide power reliably throughout the day and evening in key locations around the world (including China and India) is why CSP delivers 3 of the 12 – 14 wedges needed for “the full global warming solution.”

Now “A Santa Monica, Calif., company called SolarReserve has taken a step toward making that a reality, filing an application with California regulators to build a 150-megawatt solar farm that will store seven hours’ worth of the sun’s energy in the form of molten salt,” as the NYT‘s Green Inc. reports today.  “Heat from the salt can be released when it’s cloudy or at night to create steam that drives an electricity-generating turbine.”  And SolarReserve has a big-time Fortune 50 clean energy partner:

United Technologies has licensed the technology to SolarReserve and will guarantee its performance “” a crucial advantage for the startup when it seeks financing from skittish bankers to build the Rice solar farm.

Below is an artist’s rendering of such a plant that focuses thousands of mirrors on millions of gallons of liquefied salt:


Here are more details:

The Rice Solar Energy Project, to be built in the Sonoran Desert east of Palm Springs, will “generate steady and uninterrupted power during hours of peak electricity demand,” according to SolarReserve’s license application.

So-called dispatchable solar farms would in theory allow utilities to avoid spending billions of dollars building fossil fuel power plants that are fired up only a few times a year when electricity demand spikes, like on a hot day.

SolarReserve is literally run by rocket scientists, many of whom formerly worked at Rocketdyne, a subsidiary of the technology giant United Technologies. Rocketdyne developed the solar salt technology, which was proven viable at the 10-megawatt Solar Two demonstration project near Barstow, Calif., in the 1990s….

As many as 17,500 large mirrors “” each one 24 feet by 28 feet “” will be attached to 12-foot pedestals. The mirrors, called heliostats, will be arrayed in a circle around a 538-foot concrete tower.

Atop the tower will sit a 100-foot receiver filled with 4.4 million gallons of liquid salt. The heliostats will focus the sun on the receiver, heating the salt to 1,050 degrees Fahrenheit. The liquefied salt flows through a steam-generating system to drive the turbine and is returned to the receiver to be heated again.

SolarReserve isn’t the only developer planning to tap molten salt to store solar energy. Abengoa Solar, for instance, intends to use salt storage at its 280-megawatt Solana solar trough plant outside Phoenix.

That project, however, will heat tubes filled with synthetic oil to create steam and transfer some of the heat to salt-filled storage tanks. By using salt for both steam and storage, SolarReserve can generate higher-temperature steam, which will allow the Rice power plant to operate much more efficiently, according to Kevin Smith, SolarReserve’s chief executive.

“Consequently, our system can capture three times the energy for the same pound of salt,” Mr. Smith wrote in an e-mail message. “Plus they have additional ‘bolt on’ equipment, plus multiple heat transfer steps to go from oil to salt to oil and then to steam for electricity generation.”

SolarReserve’s plant will be built on private land “” the site of a former World War II-era Army airfield “” near the desert ghost town of Rice. The company will air-cool the power plant, avoiding controversies over water use that have dogged other solar projects….

The company said it is negotiating with California utilities to buy the electricity generated from the Rice project and expects the solar farm to go online in October 2013, barring unforeseen delays.

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16 Responses to Solar power when the sun goes down — with help from United Technologies

  1. Sam Spade says:

    OOPS…The schematic doesn’t match the text. The all H2O system shown suggests that heat is stored as H2O, which would be at very high pressures…in an expensive pressure vessel…????

    The solar baseload reportage needs an artist who can draw the various systems in comparable schematics…for people like me, who are impatient with words.

    Molten salt technology isn’t new to central plant power production. Its been used with nuclear reactors.

  2. Chris Dudley says:

    It strikes me that having made new nuclear power illegal, California can move forward quickly with superior technologies without getting caught up in the kind of debate that San Antonio is facing where unreliable cost estimates from nuclear contractors are causing problems. More states should follow California’s example and provide a more certain atmosphere for business by making new nuclear power illegal as well.

  3. David Lewis says:

    The company is saying the projected yearly output will be 450,000 MW/hr, so that means they think the stated nominal 150 MW capacity will actually be available about 34%.

    If you wanted to build a number of these Solar Reserve plants to replace the power you’d otherwise get from a 1 GW nuclear plant, you’d need to come up with 17 plants.

    Joe’s post on a solar plant in Arizona in January that had salt storage although perhaps not the air cooling stated the cost of that one was $1 billion for a nominal 200 MW output. The capacity factor for that plant was said to be 38%, giving a capital cost per available kw of $13,000 or so.

    The Solar Reserve plant in this post has a nominal output of 150 MW and a 34% capacity factor, which means 51 MW would actually come out every hour, which means the cost, if the comparison of $13,000 per actually available kw for the large Arizona plant is remotely valid, would be roughly $663 million.

    If you needed to replace a nominal 1GW of nuclear with these Solar Reserve plants, you’d need a bit more than 17 of them.

    17 of these Solar Reserve plants at $663 million each adds up to $11.7 billion.

  4. At SolarReserve the heat is actually stored as molten salt in the 538 foot tower – which has viscosity like water but is not water.

    (The other schematic is about a different type of solar thermal)

    [JR: Yes. That is just the standard schematic I use on thermal storage.]

  5. Joe, you know that the water use controversy you mention is a bogus issue, right?

    The Heartland Institute (of the “500 climate denier scientists” campaign)is cooking up fake worries about that as I wrote about here:

  6. Scott Callaway says:

    IS much water use anticipated to keep the mirrors clean?

  7. David Lewis says:

    Re: water usage by this type of plant dept.

    “Desert Power: The Economics of Solar Thermal Electricity for Europe, North Africa and the Middle East” has a table showing “Raw water usage (liters per MWhr)”. According to this table, which is on page 19 of the study:

    500 MW coal plant – 2,472 liters/MW
    500 MW natural gas- 1,141 liters/MW
    CSP no storage – 70 liters/MW
    CSP with storage – 70 liters/MW

    The study was prepared to assess powering part of Europe with CSP from the best parts of North Africa and the Middle East.

  8. Bill Woods says:

    “thermal storage is much cheaper and has a much higher round-trip efficiency than electric storage.”

    Because it isn’t ‘round-trip efficiency’. Heat is collected, and stored, and then converted into electricity. As opposed to pumped-storage hydro or CAES, in which electricity is converted into elevated water or compressed air and then coverted back to electricity.

  9. paulm says:

    Surely this will change the renewable landscape overnight if it were applied everywhere?

    I can’t understand why governments haven’t done this full scale. It seems like such a straightforward solution.

    Japan accelerates purchase of surplus solar electricity at homes

  10. Great post…I think the idea of using sun as a source of energy is really good as it helps to reduce down the energy expenses.
    keep posting some more like this..

  11. russ says:

    Love the extreme bloggers! They all quote each other to build a case. The water consumption figures Susan points to are not correct.

    The hot water (after the turbine) has to be cooled to restart the cycle. The same whether it is a gas turbine combined cycle plant or a solar plant.

    Traditional cooling towers operate the same whether they are in a solar plant or any other type of plant. The water consumption is very similar. Anytime a plant uses a ‘once through’ system the requirements are high though less water is evaporated but heat is dumped into the river.

    If any plant chooses to use air cooling or a Heller cooling tower the water consumption goes down the same. If the above mentioned solar plant is using the traditional cooling towers the water consumption is 2.5 to 3 liters per kWh generated. The utilities themselves use this figure!

    Water for cleaning the mirrors is minimal – maybe 0.08 liters per kW

  12. russ says:

    The air cooling system is supposed to reduce water consumption to approximately 0.3 liters per kW.

  13. I had the pleasure of meeting Solar Reserve CEO Terry Murphy earlier in the year at a Solar Convention in Barcelona. His pitch about their product was very impressive. Most of the company originates from the aerospace industry, which is one of the reasons why their technology appears to be ahead of some of its competitors. They also have a good business plan, using some of the development strategies employed by the Wind business to plan their installations.

    The 7 hour storage has a massive impact on their economic viability. If this first plant can be completed more or less on time and budget, I think Solar Reserve will be one of the biggest players in the future.

    Tomas Martin, Solar Analyst, Wind Prospect Group

  14. Chris Dudley says:

    David (#3),

    That calculation seems a little silly doesn’t it? Nuclear power plants don’t provide dispatchable power. What matters is the rated capacity, not your dilution. If you want to see the cost of energy rather than capacity you have do the calculation right and if you do, nuclear power comes off very poorly:

  15. russ says:

    Again, regarding water use – please see the NREL site for good, unbiased information.

  16. Andy says:

    Well, the nice thing about building stuff in the desert – no rain delays!