California approves its first molten salt solar power plant


December 16, 2010

Molten salt technology was demonstrated at the Solar Two project

Molten salt technology was demonstrated at the Solar Two project

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One of the biggest problems with solar energy is that the sun doesn’t shine 24 hours a day. This means that unless users are only planning on using electricity when the sun is shining, some form of energy storage system is required. Since storing excess electricity in rechargeable batteries isn’t really practical for large-scale solar power plants, another storage system is needed. U.S. utility-scale solar project developer SolarReserve has now received approval for the first solar power plant in California that uses molten salt technology to store the sun’s thermal energy as heat so it can generate electricity when needed, at any time of the day or night.

The Rice Solar Energy Project is designed as a solar power tower, with thousands of tracking mirrors (heliostats) focusing concentrated sunlight on a receiver that sits at the top of a central tower to collect the thermal energy. Whereas most solar power towers use this thermal energy to heat water into steam to power a turbine, SolarReserve’s system uses the thermal energy to heat molten salt to store the energy. The molten salt is a mixture of sodium nitrate and potassium nitrate that is non-flammable and non-toxic and is an efficient and inexpensive energy storage medium.

In a Rankine cycle, the sunlight heats this molten salt to over 1,000 degrees Fahrenheit (537.8 degrees Celsius) before it flows through to a thermal storage tank where the company says it maintains 98 percent thermal efficiency. When needed, it is pumped to a steam generator to produce steam and drive a standard turbine to generate electricity. SolarReserve says the Rice Solar Energy Project has the ability to collect and store enough thermal energy each morning to operate at full power all afternoon and for up to eight hours after sunset.

Molten salt technology was demonstrated in the Solar Two project in the Mojave Desert that had the ability to produce 10 MW of electricity. Its molten salt system allowed the plant to store energy in large tanks and continue running for up to three hours after the sun had set. Starting in 1995, it was decommissioned in 1999 having successfully demonstrated the technology.

In an indication of California’s commitment to solar and other renewable energy solutions, SolarReserve received approval for the construction and operation of the 150 MW solar tower project in a record time of 13 months from the initial application. The Rice Solar Energy Project will be located 30 miles (48 km) northwest of Blythe in eastern Riverside County and will supply approximately 450,000 MWh of zero-emission electricity annually – enough to power up to 68,000 homes during peak electricity periods.

SolarReserve is aiming to start construction of the plant in the third quarter of 2011.

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About the Author
Darren Quick Darren's love of technology started in primary school with a Nintendo Game & Watch Donkey Kong (still functioning) and a Commodore VIC 20 computer (not still functioning). In high school he upgraded to a 286 PC, and he's been following Moore's law ever since. This love of technology continued through a number of university courses and crappy jobs until 2008, when his interests found a home at Gizmag. All articles by Darren Quick

Yup! I like the underlying tech but this will never be practical and/or ever generate a useful amount of power.


Italian Nobel for fisics Carlo Rubbia proposes a variant to this kind of power plant, it replaces the tower and the heliostats with parabolic mirrors which have an absorber tube as receiver.

a 3d model of the \"project archimede\" (actually running in Sicily since this july) can be found on Second life, enel\'s land, enel park

Giuseppe Picciuca

just build a nuclear power plant and stop eff\'ing around with all this garbage.


Don\'t listen to trash mouthed wrong headed nuke apologists. Build, baby, Build! But i\'m concerned; If that molten mixture of sodium and potassium nitrates (eutectic, yes?) cools off and congeals, would that not plug up the works?

Don Bill

The thermal system is interesting, but if they are not also using the steam cycle to desalinate water, they would be better off using sterling cycle engines to produce the electricity.


Why was Solar two shut down? Too expensive to operate? Can\'t make a profit with a measley 10 MW output? If its already built and functioning why kill it? 10 MW is 10 MW, no?


Thorium nuclear plants are the answer. Look it up!

John Weiss

Salt plants in Northern Africa should work very well, Large masses can be melted, from solid into gel, Providing needed power, to send beneath the sea, To European countries, that need electricity.

One day when this will happen, solar then will find, Its place in power production and a changing of the mind, That concentrated solar, with salt to hold the heat, Is a generation process that should help coal to unseat.

Adrian Akau

Good innovative approach for wider usage of Solar Power.

Dr.A.Jagadeesh Nellore(AP),India

Anumakonda Jagadeesh

I wonder what the payback time is for a plant of this size. Also why not just generate the electricity during the day, and let some other supplier provide night-time energy? Then you wouldn\'t need the molten salt. All the heliostats take a lot of maintenance. This whole project looks enormously expensive. Maybe someone has talked a lot of investors into parting with their money.


@ Don Bill: I would suggest to you that the salt mix is not flowing, rather, is a heat vessel that tubing holding the heated media lays in. Like a tankless hot water coil in a boiler. The salt just kinda sits there changing state accordingly.


Curious thing this salt towers and the other projects availible, They were first considered in the 1950\'s but fear or rather the suggestion of fear that this type of technolgy would leed to massive unemployment in the oil, gas industry. Grey Goo might have been one of the excuses for not proseeding. Much like the nano carbon fibre screen that separates Hydrogen at the point of use thru magnetic remediation,with minimal electrical use in production, is dormant because of similiar such fears.Like it might open a portal into another world and the sky might fall or you be forced to be a socialist and a dozen forms of fears purposely generated are more grey goo spread around by the folks like the Petroleum Institute. But eventually the conditions of useing out dated methods of energy production out weigh the need to protect the big cash cows, These projects are indications of the real concerns,which is no longer a laughing matter.

Tsh M E Aigo

Solar, Wind, Wave, Hydro, Tidal, Geothermal, biological, clean, domestic renewable = perpetual = eternal American energy sources, and thorium LFTR reactors from China will provide 21st century placement energy for current enriched uranium sources, oil and coal sources, as they diminish.

Bruce Miller
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