Gemasolar solar thermal power plant supplies power for 24 hours straight

Jul 11, 2011 by Lisa Zyga weblog
Gemasolar is located near Seville, Spain, on 185 hectares (about 0.7 square miles) of land. Image credit: Torresol Energy

(PhysOrg.com) -- Last week, the Gemasolar power plant near Seville, Spain, became the first commercial solar thermal power plant to supply uninterrupted power for a full 24 hours, according to builders Torresol Energy. In contrast to photovoltaic solar cells, which use the sun’s light to generate electricity, solar thermal plants use the sun’s heat to run steam turbines and generate electricity. One of the biggest advantages of using heat is that it can be stored more easily than light, allowing for electricity production to continue even after the sun sets.

The Gemasolar 19.9-MW Concentrated Solar Power system is a “power tower” plant, consisting of an array of 2,650 heliostats (mirrors) that aim solar radiation at the top of a 140-m (450-ft) central tower. The radiation heats molten salts that circulate inside the tower to temperatures of more than 500 °C (932 °F). The hot molten salts are then stored in tanks that are specially designed to maintain the high temperatures. This cutting-edge heat storage system enables the power plant to run steam turbines and generate electricity for up to 15 hours without any incoming solar radiation.

Gemasolar’s ability to generate 24 hours of electricity marks an important step toward demonstrating the reliability of solar technology, which is one of the industry’s biggest challenges. In addition to providing continuous power on cloudy days and at night, Gemasolar’s storage capacity makes it possible to manage the supply of electricity sent to the network and respond to spikes in demand. As noted in a press release from Torresol Energy, “The reliability of solar energy becomes comparable to that of conventional fossil-fuel , which is decisive as the demand for renewable energy increases.”

As the company explained, Gemasolar had only been operating commercially for one month prior to its 24-hour run.

"Gemasolar achieved optimal performance in its systems in the last week of June,” said Diego Ramírez, Director of Production at Torresol Energy. “The high performance of the installations coincided with several days of excellent solar radiation which made it possible for the hot-salt storage tank to reach full capacity. We're hoping that in the next few days our supply to the network will reach an average of 20 hours a day."

The power generated by Gemasolar is sent to a nearby power substation, where it is injected into the grid. Torresol Energy estimates that Gemasolar will generate 110 GWh of electricity per year, enough to about 25,000 homes, as well as reduce carbon dioxide emissions by more than 30,000 tons per year.

Torresol Energy is a joint venture between Abu Dhabi’s future and clean technology company Masdar and the leading Spanish engineering and construction company SENER.

Explore further: A platform to help consumers achieve sustainable energy consumption

More information: Torresol Energy news
via: Gizmag

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User comments : 28

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Newbeak
2.8 / 5 (4) Jul 11, 2011
Why not double or triple the storage capacity of the salt tanks? I guess it's a matter of keeping costs down.
hyongx
4.5 / 5 (11) Jul 11, 2011
Tripling the capacity of the storage tank wouldn't help them if the limiting factor is solar radiation. Also, my guess would be that the heat storage system operates at maximum efficiency if it is closer to full, rather than mostly empty, so designing too much extra storage space would be detrimental.
pauljpease
3.8 / 5 (11) Jul 11, 2011
Yes, a plant like this costs tens of millions of dollars, you can be sure they did their math and it's working about as good as current technology allows. The amount of salt is not the limiting factor, you only need enough salt to absorb the solar energy, no more and no less. Otherwise, why not put 1,000 times as much salt and get 1,000 times the energy?!
Newbeak
not rated yet Jul 11, 2011
My idea was that the salt tank would be "charged",ie melted,and then the heat could be drawn out to generate power.While doing this,the solar tower would be feeding fresh heat to the salt to remelt it.
eachus
3.3 / 5 (7) Jul 11, 2011
Torresol Energy estimates that Gemasolar will generate 110 GWh of electricity per year, enough to power about 25,000 homes, as well as reduce carbon dioxide emissions by more than 30,000 tons per year.


I hate bogus numbers like this from "green" energy producers that are not related to reality. 110 GWh/year is about 12.5 MWe average. Converting this to home consumption of 25000 means an average of 500 watts per home. (You know what your utility bill is--take KWh/month and divide by 360 to get average consumption in kilowatts.)

Also notice that it would take about 60 of these to replace one 1 GWe nuclear plant. The American Southwest and even Spain have lots of suitable sites. But Portugal? Maybe one or two...
Eikka
3 / 5 (2) Jul 11, 2011
My idea was that the salt tank would be "charged",ie melted,and then the heat could be drawn out to generate power.While doing this,the solar tower would be feeding fresh heat to the salt to remelt it.


It's always molten. Otherwise you can't pump it around.

Anyways, the easiest way to get the plant to output 24 hours a day is to simply output less.
Newbeak
3.3 / 5 (3) Jul 11, 2011
My idea was that the salt tank would be "charged",ie melted,and then the heat could be drawn out to generate power.While doing this,the solar tower would be feeding fresh heat to the salt to remelt it.


It's always molten. Otherwise you can't pump it around.

Anyways, the easiest way to get the plant to output 24 hours a day is to simply output less.


Sorry,I meant that more salt could be added to extra storage containers and when all the salt was melted,energy extraction could begin.I guess only as much heat could be extracted each day as the solar collectors could replace,otherwise you would have solidified salt in the storage containers.I wonder if solidified salt would float in the storage containers or sink? Either way,heat extraction coils could be placed so they always sat in molten salt.That way,the insulated storage containers could act as heat batteries,could they not?
mrwolfe
3 / 5 (2) Jul 11, 2011
It would be possible to use grid power to heat the salt tank as well, although not implimented here. In Australia we use the snowy hydro-electric scheme as off-peak energy storage, although it is inefficient. Salt tanks might be a viable alternative for energy storage.
plaasjaapie
2.8 / 5 (5) Jul 11, 2011
I wonder what their electricity production cost per kwhr are before subsidies are applied?
Skepticus
3.4 / 5 (8) Jul 12, 2011
I wonder what their electricity production cost per kwhr are before subsidies are applied?


Why wondering? It's always cheaper to spend trillions to kill towel heads and keep the ME cheap and flowing, as we have always done. Ahh..the heady smell of burnt gas, the godly noises, the warmth of the exhaust blasts from a V8...
antialias
5 / 5 (1) Jul 12, 2011
The American Southwest and even Spain have lots of suitable sites. But Portugal? Maybe one or two...

Portugal has PLENTY of space. The entire south (Algarve and Alentejo) is mainly desert/plains (and very sparsely populated). They have problems getting water down there to do any serious farming. Putting up solar power plants in that region could be a major game changer for such a poor area.

I guess only as much heat could be extracted each day as the solar collectors could replace,otherwise you would have solidified salt in the storage containers

If it were otherwise you would have just created a perpetuum mobile.

Solidifying salt in the tanks isn't the problem. Solidifyig salt in the pipes is. But for that case conventional backup is included (gas burners) which should be rarely - if ever - needed given the high number of sunny days in that region.
antialias
not rated yet Jul 12, 2011
Couldn't find a source for the average household energy consumption but I did find a source that said that space heating is used, on average, for only about 1 month per year (airconditioning is almost unheard of in private homes - certainly at a much, MUCH lower level than in the US). So that 500W figure may actually be enough to run an average houshold.

Interesting side note: Wikipedia states that 70% of national energy production in Portugal is already from renewable sources (and they are a net exporter). Mostly wind (and water for storage)
ShotmanMaslo
1 / 5 (1) Jul 12, 2011
Interesting side note: Wikipedia states that 70% of national energy production in Portugal is already from renewable sources (and they are a net exporter). Mostly wind (and water for storage)


Please post a link, because I doubt it. According to this, wind power generates just 17 % of Portugal energy:

http://en.wikiped...Portugal
antialias_physorg
not rated yet Jul 12, 2011
Please post a link, because I doubt it.

Just citing wikipedia (wikipedia: portugal. Go to the section 4.7. on 'Energy')

They cite an article in Portuguese. Though I don't speak portuguese the last sentence seems to say that 70% of the electricity production from January to May was accomplished using renewables.
finitesolutions
5 / 5 (2) Jul 12, 2011
This type of plant is perfect for Africa and all desert nations.
They are relatively simple and if built by the hundreds they will transform entire regions.
They can also try to elevate the mirrors on polls so they can still use the shadowed cooled land underneath for some sort of agriculture.
JMDC
5 / 5 (1) Jul 12, 2011
Being Portuguese, I must warn that, about the weight of renewables in electricity production in Portugal, Wikipedia is not a very good source...
Try http://www.pordat...ime/?n=4

The real weight of renewables in the production of electricity in Portugal is neither 17% nor 70%. The more realistic number which is considered, over here, is between 38% and 45%...Good, but not Excelent...
ShotmanMaslo
1 / 5 (1) Jul 12, 2011
This is far better:
http://nextbigfut...lar.html
antialias
not rated yet Jul 12, 2011
The real weight of renewables in the production of electricity in Portugal is neither 17% nor 70%. The more realistic number which is considered, over here, is between 38% and 45%...Good, but not Excelent..

Thanks for the 'heads up'. Still: those are impressive numbers. Since we are only at the beginning of the 'solar revolution' this seems promising for the future for Europe as a whole and Portugal in particular. I hope the current fiscal problems won't lead to drastic cuts in this sector.
lengould100
3.7 / 5 (3) Jul 12, 2011
Also relevant to this article is this study by independent engineering firm Sargent & Lundy Engineering (Chicago) who were commissioned by NREL in 2003 to do a standard analysis of the (then) current state of solar thermal generation technology, especially costs using industry standard construction estimates.

http://www.nrel.g...4440.pdf

Bottom line.

2003 costs of solar thermal generation - 12.5 cents / kwh.

2020 costs of last install if 2 to 8 GW would get built - 3.5 to 6.2 cents / kwh. (depending only on fairly straightforward improvements and volume production)

We should be REALLY encouraging solar thermal, especially with thermal storage.
lengould100
1 / 5 (1) Jul 12, 2011
Also interesting to compare the output of this 185 hectares of land to that of a 185 hectare bio-mass energy project after accounting for the cultivation, harvesting, fertilizing, pesticides, quality of output energy, etc. etc. Something approaching 300 times more efficient land use.
Scottingham
5 / 5 (1) Jul 12, 2011
@Lengould100

Compare it to 185 hectares of modern fission reactors and you're into the terawatt level of power!
SteveL
not rated yet Jul 12, 2011
@Lengould100

Compare it to 185 hectares of modern fission reactors and you're into the terawatt level of power!


That would require a massive amount of cooling water.
lengould100
2.3 / 5 (3) Jul 12, 2011
Scottingham: I don't entirely disagree, but am reaching the conclusion that, esp. for jurisdictions with high insolation resources (western US, mediteranean etc.) solar thermal as above, installed on relatively low-value land, is the smart way to go, ESPECIALLY if one could get to the lower costs of volume manufacturing and incremental design improvements.
wolvesman
5 / 5 (1) Jul 14, 2011
please check out beyond zero emissions and read the Zero Carbon Australia Stationary Energy Plan by 2020. it proposes 220MW towers and an area of 53 x 53 km of marginal land combined with 40% wind will power entire Australia with 145% energy!
CST is the technology of the future with Zero carbon emissions!
mrlewish
not rated yet Jul 17, 2011
Solar panels over roads. You have interstate 10 and 40 running through Arizona and into California. Put solar panels over the roads. There would be no land use impact for obvious reasons.
Newbeak
not rated yet Jul 17, 2011
Solar panels over roads. You have interstate 10 and 40 running through Arizona and into California. Put solar panels over the roads. There would be no land use impact for obvious reasons.

Nah. Solar Roadways is the way to go: http://www.solarr...ro.shtml
Sin_Amos
not rated yet Jul 18, 2011
Simple question? Why does it matter how many homes this can generate electricity for, when we all know each individual home should be self-sufficient with its own power generation. I laugh when people start to knock this technology comparing it to nuclear reactors, when the simplest answer is so obvious. Design energy efficient homes that are powered by geo-thermal and solar. So easy, but rarely done. Just sink pipes under the foundations and design homes meant to collect energy. The grid is obsolete.
antialias_physorg
3 / 5 (2) Jul 18, 2011
when we all know each individual home should be self-sufficient with its own power generation.

How exactly are you going to install sufficient power generators in cities for a skyrise to make it self suffcient? Do you want every block to be a major polluter in such a densely packed area? (because sinking geothermal pipes there is often neither an option nor sufficient)

How will you supply energy to businesses which are energy intensive but cannot afford on site generatory?

How do you handle shifts in energy availability and need (you must have the ability to get energy to your homes in the wniter when the sun isn't sufficient? It's then that you need extensive (solar/wind/hydro/biogas) powerplants elsewhere.

Your idea relies on people being able to affor much more expensive homes ans living evenly spaced apart. That's, unfortunately, not the case.