World's First Molten Salt Concentrating Solar Power Plant Opens

You are probably familiar with concentrating solar power (CSP), but a new type of CSP plant, a molten salt CSP plant, has just gotten rolling and you may not yet know why that is important.

The “Archimede” (as this new power plant is called) was built by the Italian utility Enel and ENEA, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development. It is a 5 MW plant located in Priolo Gargallo (Sicily), inside Europe’s largest petrochemical district.

Older CSP plants, completely reliant on direct sunlight, can only operate in daytime. Newer CSP plants, however, use molten salts storage so that they can operate for longer. But Archimede is the first CSP plant that is using molten salts to collect heat from the sun, not only store it.

This is good because molten salts can work at higher temperatures than the synthetic oils used in traditional CSP plants (up to 550°C rather than 390°C). So, efficiency and power output of the plant is higher.

Such plants can also operate for much longer. They can go 24 hours a day for several days without sunshine.

Additionally, no oil-to-salts heat exchangers are needed and safety and environmental concerns related to the use of oils are also eliminated. As Carlo Ombello of Guardian News writes, “molten salts are cheap, non-toxic common fertilizers and do not catch fire, as opposed to synthetic oils currently used in CSP plants around the World.”

Additionally, here is a big one: “the higher temperatures reached by the molten salts enable the use of steam turbines at the standard pressure/temperature parameters as used in most common gas-cycle fossil power plants. This means that conventional power plants can be integrated – or, in perspective, replaced – with this technology without expensive retrofits to the existing assets.”

The problem with molten salt CSP plants is that salts tend to solidify at around 220°C, and in order to address that, some expensive technological developments were needed that currently drive the price of the plants up a bit. Archimede was built for a whopping €60 million ($77.5 million)! Quite a lot for a 5 MW power plant. But, Ombello writes, “there is overwhelming scope for a massive roll-out of this new technology at utility scale in sunny regions like Northern Africa, the Middle East, Australia, the US.” We will see.

via Green Building Elements and Guardian News

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Photo Credit: Enel via Guardian News

http://bmworangecounty.org/ Susan

This gave Solar Two the ability to produce 10 megawatts. Solar Two used molten salt, a combination of 60% sodium nitrate and 40% potassium nitrate, as an energy storage medium instead of oil or water as with Solar One.”
http://www.opportunityenergy.org Carlo Ombello

Hi guys,

The Guardian subtitle to my post was misleading, as I promptly wrote to them when they posted. Nonetheless, if you read the full article (and comments) you will not find wrong information, the “world first” claims are correct.

The Archimede plant is indeed the first in the world to use molten salts to transfer heat from the pipes in the parabolic troughs, and then also to store the high level heat. The very point of the whole article is highlighting the differences such a solution makes in the “quality” of the heat collected in the troughs, and in the simplified design it conveys compared to current technology.

Also, the steam turbine used is the one existing in the adjacent gas plant, to which Archimede is connected. Archimede is the first CSP plant in the world to match standard gas-cycle steam turbines parameters.

For any further queries you’re more than welcome to check my blog and add comments. Also, links are provided to retrieve further information from ENEA, ENEL, or pipe developers Archimede Solar Energy.

Hope this helps.

Regards

Carlo Ombello

http://www.zacharyshahan.com Zachary Shahan

Thank you for the response, Carlo! Clears some things up for me. Hopefully, for others as well.

Rif

@Jesse, @Chris, @Zachary

No, read the article again! The Archimedes power plant is first because it uses molten salt as heat transfer fluid in the tubes of the mirror array. All previous parabolic trough plants have used a sort of oil in a closed system as heat transfer from mirror array to boilers/storage system.

The Solar Two plant was a (solar thermal) tower design, not a parabolic trough design and hence do not use heat transfer fluid. So the reference is not relevant to the article.

The central tower design has the advantage of having the mirrors directly reflecting on to the boiler/storage system. However the disadvantage is that the central power tower design cannot scale very far, as additional mirrors would have to be placed to far away from the central boiler to be effective.

Arrays of parabolic trough does not have the same need to be that close to boiler/storage system and hence can scale up to much larger plants.

The largest tower design is the PS20 (20MW) at Seville in Spain, whereas the typical parabolic trough plants are 50MW and could without much problems be made several 100MW.

I salute Archimedes in Italy for trying a new heat exchange method. If this method do not run into problems with corrosion, solid salt blocked in pipes or other unforeseen complications, this may become the standard CSP design in 5-10 years time.

Doei RIF
http://MoneyAisle.com Andrew

But maybe Solar Two used oil to collect heat and salt to store heat, whereas this uses salt for both…

http://www.zacharyshahan.com Zachary Shahan

right, the point made in the article, and now by some others in the comments here. thank you.

Chris V

Solar Two outside of Barstow, CA, was a molten salt concentrating solar power plant. It was build in 1995.
Jesse Williams

As far as I know Solar Two was the first to use molten salt. Here’s a wikipedia quote:

“In 1995 Solar One was converted into Solar Two, by adding a second ring of 108 larger 95 m² (1,000 ft²) heliostats around the existing Solar One, totaling 1926 heliostats with a total area of 82,750 m² (891,000 ft²). This gave Solar Two the ability to produce 10 megawatts. Solar Two used molten salt, a combination of 60% sodium nitrate and 40% potassium nitrate, as an energy storage medium instead of oil or water as with Solar One.”

http://www.zacharyshahan.com Zachary Shahan

Thank You, Jesse & Chris V. Looks like a really need to start fact-checking Guardian News — thought it was a reliable source, but second time in the past week or two.

Karl

By any chance is it known which types of small turbines they use? Capstone microturbines which are extremely low maintenance are being used with the heliofocus solar unit and that looks VERY promising. I really like the microturbine coupled idea. What a way to squeeze as much energy out of the sun as possible!