Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!


Forgot your password?
Power Technology

World's First Molten-Salt Solar Plant Opens 316

An anonymous reader writes "Sicily has just announced the opening of the world's first concentrated solar power (CSP) facility that uses molten salt as a heat collection medium. Since molten salt is able to reach very high temperatures (over 1000 degrees Fahrenheit) and can hold more heat than the synthetic oil used in other CSP plants, the plant is able to continue to produce electricity long after the sun has gone down. The Archimede plant has a capacity of 5 megawatts with a field of 30,000 square meters of mirrors and more than 3 miles of heat collecting piping for the molten salt. The cost for this initial plant was around 60 million Euros."
This discussion has been archived. No new comments can be posted.

World's First Molten-Salt Solar Plant Opens

Comments Filter:
  • by Antony T Curtis ( 89990 ) on Friday July 23, 2010 @02:09AM (#33000074) Homepage Journal

    This is big news!

    The larger the temperature difference, the more efficiently we can turn the heat into electricity. Superheated steam is just too difficult to manage over distances so this would make a great first step of collecting the solar energy and transporting it to a single location to make superheated steam.

    The best part is that NaCl is non-toxic and doesn't need to be kept under pressure. If you have a natural gas Bunsen burner and good test tubes handy, it is just about possible to melt salt and prove to yourself how stable it is. Just be careful about spilling it because it is hot enough to get things like wood and paper to auto-ignite on contact. The hottest temperature you can expect to achieve with natural gas is around 700 degrees Celsius, if I remember correctly.

    (as a side note, this is why low pressure nuclear power plants have such poor efficiency - because the water is only at 100 degrees Celsius after being heated by the nuclear fuel).

  • Re:Already done? (Score:5, Informative)

    by Xandar01 ( 612884 ) on Friday July 23, 2010 @02:16AM (#33000102) Journal
    This one doesn't use salt, but we have had one very similar built here back in 2008. http://www.renewableenergyworld.com/rea/news/article/2010/07/areva-boosts-solar-supersteam-parameters-in-bakersfield [renewableenergyworld.com]
  • "Salt" != "NaCl" (Score:5, Informative)

    by billstewart ( 78916 ) on Friday July 23, 2010 @02:19AM (#33000112) Journal

    The article isn't specific about *what* salts they're using, but says "molten salts solidify at around 425 degrees F" - NaCl's melting point is about 800 C.
    One of the articles they reference refers to another project that uses a mixture of sodium and potassium nitrates.

  • by not5150 ( 732114 ) on Friday July 23, 2010 @02:20AM (#33000120)
    The article is incorrect... Barstow had a molten salt plant in 1995 I believe. Excerpt from the Wiki - "1995 Solar One was converted into Solar Two, by adding a second ring of 108 larger 95 m (1,000 ft) heliostats around the existing Solar One, totaling 1926 heliostats with a total area of 82,750 m (891,000 ft). 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," - http://en.wikipedia.org/wiki/The_Solar_Project [wikipedia.org]
  • Re:Conversions... (Score:4, Informative)

    by Anonymous Coward on Friday July 23, 2010 @02:22AM (#33000132)

    30,000 square meters = 0.03 square kilometers

  • by QuantumG ( 50515 ) * <qg@biodome.org> on Friday July 23, 2010 @02:29AM (#33000170) Homepage Journal

    5MW for $60M (euro).. really?

    At 10c/kWh it can earn $500/hr. So it'll only take ~13.7 years to pay it off.. oh it's solar, right, well, with the seasons and everything I guess it's more like double that. Let's say ~27 years. How much is maintenance? Oh yeah, and the time value of money.

    Another way of looking at it: it's $12B/GW + operations. Nuclear power plants take 5-10 years and cost $4-10 billion to build, and $4-6 billion for fuel and operation over their lifetime, so $8B/GW to $16B/GW. So the cheapest nuclear reactor beats this by at least 35% and the most expensive nuclear reactor probably beats it also.

    But that fact that they've even made it into the right ballpark is impressive and perhaps once they scale it up to somewhere that is actually useful we'll have some idea how competitive it can be.

  • Re:Conversions... (Score:3, Informative)

    by mark-t ( 151149 ) <markt@@@nerdflat...com> on Friday July 23, 2010 @02:31AM (#33000180) Journal
    30,000 square meters = 3 hectares = 7.41 acres = 0.012 square miles.
  • by Anonymous Coward on Friday July 23, 2010 @02:45AM (#33000236)

    Interest at 4%
    2.4M a year
    loss per year .9M

    I wonder what it costs to operate ?

    I would love to find out how much liability insurance is on molten salt.

    Property tax might be cheap in Spain, or the tax bill on a couple hundred acres and a 60M plant would eat into that 5M subsidy they got.

  • Re:"Salt" != "NaCl" (Score:5, Informative)

    by c0lo ( 1497653 ) on Friday July 23, 2010 @02:48AM (#33000246)

    The article isn't specific about *what* salts they're using,

    This one [sicilyguide.com] does: the same as Solar One/Two - a mix of sodium/potassium nitrate.

  • by Anonymous Coward on Friday July 23, 2010 @03:13AM (#33000318)

    30000 sq. m = 0.03 sq. km

  • by c0lo ( 1497653 ) on Friday July 23, 2010 @03:19AM (#33000336)

    30 square kilometers of land for 5 megawatts output? To me that doesn't seem very viable...there's single wind turbines with more output than that.

    30000 sqm does not make 30 sq km. Let's try some computations of achieved efficiency:

    • Input - going maximal here. Solar energy flux - 1.44 kW/sqm (ignore absorption in atmosphere). Thus total input= 43.2 MW. Say it for 10 hours/day = 432 MWh
    • output - 5 MW for 24 hours=120 MWh

    Minimal modelled efficiency: 27%. - I'd say definitely a decent efficiency.

    Can they improve? Keeping into account the last step of energy transformation (thermal->electric) operates between say 825 K (molten salt) and 400 K (water at 120 C - moving the turbines) and assuming a perfect Carnot cycle, the maximum efficiency achievable would be lower than 52%.

  • by Anonymous Coward on Friday July 23, 2010 @03:30AM (#33000362)


    France had one of these, inaugurated in 1983, called "Thémis".
    (danger! websites in French).

    It used a circuit of molten salt, just like the OP's "world's first molten-salt solar plant"

    Both this and the Barstow plant were subsequently adapted for gamma-ray astronomy (on which I work, and spent much time there).

    The plant was experimental, and I believe only produced a surplus of energy on one day! It was set up ostensibly on a green agenda, but may have been done mainly to research molten salt for the Superphenix nuclear reactor (now shut down).

  • by gedw99 ( 1597337 ) on Friday July 23, 2010 @03:36AM (#33000410)

    The costs for this plant are very high of course because its a new thing.

    This simple power point PDF reallyshows the numbers of the solar thermal salt plant in spain that is run as a research plant.
    http://www.dlr.de/tt/Portaldata/41/Resources/dokumente/institut/thermischept/Solar_Thermal_Energy_Storage_Technologies_Hannover2008.pdf [www.dlr.de]

    They actually concluded that Salt is Not the only option. The problem with salt is rust, and so you have to use carbon coating on all the steel parts, which makes it expensive.

    Simple using concrete was a very attractive option also.
    And then that means that hemp concrete is also possible which is much cheaper again.

  • by TapeCutter ( 624760 ) * on Friday July 23, 2010 @03:58AM (#33000536) Journal
    N. Africa seems to be high on the list of places where the EU want to go with solar [guardian.co.uk].
  • by interkin3tic ( 1469267 ) on Friday July 23, 2010 @04:05AM (#33000554)

    LFTR's will render these things irrelevant.

    I try not to anticipate future technology that seems right around the corner, because otherwise I'll just get depressed thinking about where I am now: in an apartment, most appliances in which are not connected to the internet to manage themselves as I fly to Hawaii in my flying car, playing Duke Nukem Forever on my VR headset.

    And no that wouldn't be unsafe because cars today are supposed to be driving themselves, I'm assuming that would work for flying cars too.

    Anyway, if molten salt solar plats really do become obsolete because of whatever not-here-yet power source you're talking about, we'll have a good mass-popcorn maker.

  • by Basje ( 26968 ) <bas@bloemsaat.org> on Friday July 23, 2010 @04:07AM (#33000564) Homepage

    The location of the plant in Priolo Gargallo is not that far from the Sahara. It's actually a little more south than the northernmost part of the Sahara in Tunesia, which is roughly 250 miles west of the plant. The solar radiation will be roughly equivalent, no need for undersea cables. Most importantly Sicily is a (slightly) more stable region that does not rely on income from oil like many of the North Sahara states.

  • Re:Already done? (Score:5, Informative)

    by Forge ( 2456 ) <kevinforge.gmail@com> on Friday July 23, 2010 @04:40AM (#33000672) Homepage Journal
    Do you mean the one mentioned in the middle of this article [earthlink.net]

    "Molten salts have been used in many industries as a high temperature heat transfer medium. The 'highest profile' use of molten salts in this regard is the Solar Power Tower near Dagget, California (excuse the pun). It uses a Sodium Nitrite/Nitrate mixture to absorb and store the sun's heat from the focus of many mirrors in the desert upon a central tower. The heat from the salt is then transfered via a heat exchanger to produce steam to drive a conventional steam turbine and generator to produce electricity from the sun for Southern California.3a"

    "Last modified, 20 Nov 97"
  • by c0lo ( 1497653 ) on Friday July 23, 2010 @05:17AM (#33000860)
    You're right. 10 mils kWh/year [enel.com]. Meaning 1 mil at EU 0.1/kWh. Minus operational costs, will take more than 60 years to pay back at the current level of prices.
  • by Ancient_Hacker ( 751168 ) on Friday July 23, 2010 @05:51AM (#33001034)

    Try estimating what the basic maintenance costs are for 3 miles of piping that can handle molten salt.

    Molten salt is rely, really *corrosive*. Either they're spending tons of money up front on miles of stainless steel, or even more every year replacing the pipes as they corrode away.

    Either way it's hard to even break even-- 5MW of electricity is only about $2 million a year wholesale, far less than the interest cost on a $60M plant, and likely less than the cost to maintain 3 mmiles of molten salt piping and collectors.

  • by RichiH ( 749257 ) on Friday July 23, 2010 @05:53AM (#33001042) Homepage

    You forgot that

    a) nuclear power plants are the only industrial plants in the world which do not need to be insured to the full extent of possible damages they might cause. The insurance industry made politics cap the max at a mere 5 billion Dollar which may sound like a lot, but it's not. The population at large would shoulder those costs.

    b) the countries in which the plants operate are charged with long-term storage. So the population at large shells out for that.

    A prime example of privatizing earnings and socializing losses if there ever was one.

    It's high time we got rid of fission (other than what we need for medical & research reasons). The claimed cost-efficiency _does not exist_. Period.

  • "Really corrosive" (Score:5, Informative)

    by Kupfernigk ( 1190345 ) on Friday July 23, 2010 @06:20AM (#33001144)
    Very few things are generally corrosive. It depends on the chemistry involved. For instance, dilute sodium hydroxide can be kept perfectly safely for years in mild steel tanks exposed to the air, whereas water or concentrated hydroxide would rapidly corrode them. It's a mistake to assume that even A4 (316), the industry standard, is suitable for everything; there are plenty of things that corrode it.

    Having said that, it's been known for a long time that certain austenitic high-chrome alloys resist molten alkali nitrates very well. I would imagine that the designers of this plant have optimised the piping for the salt mixture in use, using the usual lifetime/costs tradeoffs in corrosion engineering. (The same tradeoffs that make it much cheaper, for instance, to make a boat out of steel with sacrificial anodes than out of stainless steel or aluminum)

  • by wisdom_brewing ( 557753 ) on Friday July 23, 2010 @06:46AM (#33001226) Homepage
    Square Root 30,000.

    173.2m by 173.2m.

    square 0.1732 km .

    0.03 km - Doh!
  • by TapeCutter ( 624760 ) * on Friday July 23, 2010 @06:56AM (#33001258) Journal
    "when it's produced in bursts, you will have to find a way to store it, which means a loss in efficiency."

    Yes, however you're only looking at energy loss in one particular circumstance rather than looking at the overall efficientcy of the system in dollar terms.

    Currently coal plants produce too much at night and not enough during the day. This means they waste fuel at nightly lows and have to be supplemented by "busrts" from gas turbines during daily peaks. Therefore (if it was possible**) there's much more value in producing energy that matches the peaks and troughs of consumption rather than trying to produce it at a constant rate capable of handling the peaks, especially if you have to pay for fuel.

    The fact is that producing electricity at a constant rate capable of handling the peaks is not how electricity is generated on a commercial scale. All methods of generating electricity are intermittent. The idea that we currently have an efficient steady stream of "base load" power provided by constantly running coal plants is largely a myth created by the coal industry.

    Coal plants are shut down for regular maintenance for ~45 days/year. Meaning one redundant coal plant needs to be built for (roughly) every seven coal plants in use. Plus to handle peaks you still need to build gas turbines that will sit idle for 20 or more hrs/day (or "inefficiently" pump water uphill). The advantage with wind, solar, etc, over fossil fuels is that; when it comes to handling the unavoidable peaks you can pump water uphill, (melt salt, whatever), during "bursts" and it will cost you some percentage of nothing in fuel costs.

    Sure, windfarms also require maintenance but you can do it one windmill at a time, the whole farm very rarely needs to be shut down all at once.

    ** = Regardless of how you produce the electricity the most economically efficient answer to the inherent problems of peaks, troughs, bursts and breakdowns is a large well managed grid with built in generation/transmission redundancy and plenty of pump storage capacity.
  • by 140Mandak262Jamuna ( 970587 ) on Friday July 23, 2010 @07:36AM (#33001426) Journal

    and not *way* out of line compared to other power sources like coal plants, but it's not aggressively cheap either.

    First the whole idea of melting salt and storing it is to provide a steady energy capacity. The 5MW is steady output 24/7. Not the 10 hours you assumed. The article does not say so explicitly. But the peak solar output is slightly over 1 kW/m^2. The peak production capacity would be 30 MW for an hour or so at around noon. Accounting for the angle of incidence, cloud cover, nights, storage losses etc averages the output to 5 MW steady. So the revenue is $12000 a day at 0.1 $/kWh. or 4.4 m$ a year. works out to 5% return on investment (at 1.3 euro/USD). Cost of maintenance, salaries etc would reduce the return to may be 3%.

    On a coal plant the initial investments are lower and the return would be much higher. But it has a large running cost. Price of coal. Sunlight is free. Coal plant economics is, smaller initial investment, and a larger revolving credit to buy coal, make electricity, collect payments and pay off the coal company, rinse and repeat.

    Anyway, it is incredible that this technology that is just born is already competitive with a technology that has been fine tuned and developed for nearly a century. Its costs can fall steeply in the coming years. Coal tech, is nearly as low cost as we can humanly get, and no further reduction is coming without compromising safety.

  • by DrSkwid ( 118965 ) on Friday July 23, 2010 @08:12AM (#33001614) Homepage Journal

    Tax might be cheap in Spain, but Sicily is in Italy.

  • by Myrv ( 305480 ) on Friday July 23, 2010 @08:38AM (#33001782)

    And the oil industry has a cap of $75 million on the possible economic impact of their mistakes so I fail to see your point. If the gulf has taught us anything it should be that fossil fuel usage can cause disasters just as bad, if not worst, than nuclear energy.

    As for nuclear storage, as others have pointed out, spent fuel can be recycled. The same can't be said for the waste products of fossil fuels. At the end of the day society pays a price for all our energy usage.

  • by goodmanj ( 234846 ) on Friday July 23, 2010 @09:25AM (#33002094)

    Oh god dammit. Units failure, I'm off by a factor of 1000, and boiling water and high-temperature salt are actually about equal in terms of heat storage.

    Mod parent down.

  • by GooberToo ( 74388 ) on Friday July 23, 2010 @09:28AM (#33002128)

    So you are saying that Tchernobyl

    First one to mention chernobyl not only loses, loses all credibility, but is immediately flagged for scare mongering. If you don't know why this is obvious, you clearly don't understand enough to even be invoking the name, "chernobyl".

    As for much of you other comments, you clearly don't understand economics, a government's role in an economy, are a variety of other factors as to why the comment I provided resolved much of your "concerns." *cough*

  • Re:Already done? (Score:5, Informative)

    by confused one ( 671304 ) on Friday July 23, 2010 @09:38AM (#33002222)
    Then you must know that solar plants are often stated to have a rating which is at peak output. And by peak I mean maximum you'll ever see on the ideal day in the ideal weather. For that matter, so is any other power plant -- the nameplate output is peak, not average.
  • by WindBourne ( 631190 ) on Friday July 23, 2010 @09:49AM (#33002330) Journal
    America R&D nearly all of the nuclear power plant types, and nearly all of the current AE being sought out. In fact, this molten salt approach was pushed by Boeing in the 90's, but W's admin shot it down. Check out my Journal. And yet, we said that Coal plants made all of them irrelevant.

    The problem that America (and the west) has, is that far too many ppl wants us to depend on EXACTLY ONE THING. Well, that is the attitude that gets us in trouble. Instead, our leaders need to push a MATRIX of energy. If we have Fossil fuel accounting for about .33% of our energy today, then we would have little issue with killing it to clean up our air. BUT, when fossil fuel provides about 85-90% of your energy (in China, fossil fuel provides well over 95-99% of their energy), well, it is hard to walk away from it.

    America needs to get rid of politicians that think like you. Instead, we need pols that put the needs of the nations ahead of their party, their religion, or their commercial buddies.
  • Re:Already done? (Score:5, Informative)

    by Bemopolis ( 698691 ) on Friday July 23, 2010 @10:31AM (#33002814)

    Theoretical maximum efficiency for any kind of solar plant (on the equator) is less than 200 Watts per square meter

    BZZZT. The solar constant is 1360 W/m2 (minus atmospheric effects). With this, the efficiency is a reasonable 12%.

    I suspect the number you have quoted there is the TMI of solar cells. This plant depends on thermal conversion, not liberating electrons across a silicon band-gap. I do respect your effort, and so will not request that you turn in your geek card.

  • by PybusJ ( 30549 ) on Friday July 23, 2010 @10:33AM (#33002846)

    Both the French and Californian plants were solar tower type where the mirrors all concentrate the sun on to one point (from where heat energy can be extracted with molten salt).

    The article is about a parabolic trough system where rows of mirrors with parabolic X-section concentrate the sun onto a pipe running along the focus point. This is easier to construct and scale than the towers you point to and is already deployed more widely. Previous trough systems have heated oil in the pipes then transferred the heat to salts for storage (then again to water to run a turbine).

    The advance here is to avoid this oil to salt transfer, while the slashdot headline is inaccurate (shock horror), this something new and a genuine step forward.

Where it is a duty to worship the sun it is pretty sure to be a crime to examine the laws of heat. -- Christopher Morley