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New Design Delivers Round-the-Clock Solar Power

By Paul Brown, Climate News Network

LONDON - Solar power’s greatest drawback has always been that it is intermittent and, even in the sunniest climes, peak electricity demand is frequently in the evening when the Sun is going down.

The Gemasolar plant, built by Torresol Energy, can store enough heat to operate for 18 hours at full capacity without any additional power from the Sun. For many months of the year it can run for 24 hours a day.
Credit: Torresol Energy

The engineering challenge has been to design a system in which enough of the Sun’s heat can be stored to produce full power continuously even on cloudy days – and better still, all night.

Many different designs have been tried, but finally a commercial plant in Spain seems to have cracked the problem, and as a result has won an award from a panel of independent judges.

The Gemasolar plant near the Spanish city of Seville, built by Torresol Energy, can store enough heat to operate for 18 hours at full capacity without any additional power from the Sun. For many months of the year it can run for 24 hours a day.

The plant is small by power station standards, producing 20 megawatts of electricity – enough for 25,000 homes, reducing carbon dioxide emissions by 30,000 tonnes a year.

It has 2,650 mirrors, known as heliostats, which cover an area of 457 acres (185 hectares). These train the Sun’s rays onto a central tower, where they heat molten salt to more than double the boiling point of water. More heat is produced than is needed for maximum power, so the surplus is stored in molten salt tanks until it can be used during cloudy periods or at night.

‘Pioneering Design’

The award comes from DESERTEC, an organization dedicated to providing energy from arid regions, which had shortlisted four power plants, all able to store power from the Sun and produce electricity at night. It described the Gemasolar plant as “a pioneer for future power stations.”

The plant has been working for three years, showing that the technology works effectively summer and winter. The company and DESERTEC both believe that it, or a series of similar plants, can be scaled up to provide much larger populations with renewable energy.

There are now 105 similar installations – known as concentrated solar power plants – across the world. One has been operating for 30 years in California, and a large number of newer ones have been built in desert areas of the western United States. Spain is a world leader in the technology, and a number of Middle Eastern desert states have built plants of different designs with molten salt storage capacity. Gemasolar is described as the most successful design so far.

Gemasolar and DESERTEC both believe that a series of similar plants can be scaled up to provide much larger populations with renewable energy.
Credit: DESERTEC Foundation via Climate News Network

The eventual aim of concentrated solar power companies is to build large plants in the deserts of the world and transfer the electricity by super-conducting cables to large centers of population hundreds of miles away.

Fast-Growing Technology

The most obvious application is from the Sahara desert across the Mediterranean to Europe. Germany is particularly interested in the potential from this source of large-scale clean power.

It is quite distinct from photovoltaic panels, which produce electricity directly from sunlight. Here the problem of intermittent power remains, particularly where the weather is very changeable, as in north-west Europe. Despite the difficulties, engineers are working on ways of balancing the output from various solar, wind and biogas plants to keep the grid evenly supplied.

The industry is growing at an enormous pace worldwide, because the cost of solar panels has fallen by half and now is far cheaper per watt than nuclear power; and in the U.S. it is only marginally more expensive than coal.

Those keen on preventing climate change reaching dangerous levels point out that a one-kilowatt solar system can each month eliminate the burning of approximately 170 pounds of coal, preventing the release of 300 pounds of CO2 into the atmosphere, and saving up to 105 gallons of water consumed in cooling towers. 

Paul Brown is a joint editor for Climate News Network. Climate News Network is a news service led by four veteran British environmental reporters and broadcasters. It delivers news and commentary about climate change for free to media outlets worldwide.


By Bill Stewart (San Francisco CA 94107)
on May 4th, 2014

Correction - The 185 hectares are 457 acres, not 457 miles, for those of us using obscure traditional measurement systems.  It’s about 2/3 of a square mile, which seems like a lot of space for powering that many homes.

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By David Midgley (Leeds)
on May 6th, 2014

No, it’s not a lot of space - if each home occupies a 1/4 acre plot, the power station will occupy 7.5% of the area of the homes supplied.

Of course this is more than a fossil fuel power station, but this neglects the fact that here the energy is actually produced on site, not just transformed from stored energy to electrical energy.

If you take into account the land used in extracting the fuel, a coal fired power station uses nearly this much land per megawatt of capacity - despite the fact that it is still not producing energy, only using up (solar) energy that was stored millions of years ago.

I would also imagine that if these plants were scaled up, they would be more efficient in land use than this relatively small plant.

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By Mike McClory (Cambridge UK)
on May 6th, 2014

True, it is a large area, but CSP schemes like this are only economical in areas of strong sunlight such as Spain, Saharan Africa, the Middle East and SW USA.  These are areas that are particularly arid, so tthe ground isn’t much use for anything else.  The shade produced by the heliostats may actually be useful in it’s own right.

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By Dave (Basking Ridge, NJ 07920)
on May 4th, 2014

Great report of the new Spanish solar plant, but this one item of commentary is inaccurate / out of date.

“The most obvious application is from the Sahara desert across the Mediterranean to Europe.”

This was the original Desertec export idea – generate in the Sahara and export to the EU. It sounded great at the time – still does. But it turned out that there were major issues. That particular idea was finally abandoned last year.

BTW: I am not trying to be picky - but also 185 ha is 457 acres not “miles” as stated here.

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By Hanens
on May 5th, 2014

For what it’s worth, the plant can be found @ (37.560544, -5.331616) wink

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By Joe
on May 9th, 2014

Hell of a lot prettier than a coal plant.

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By Dhugal Fletcher (Melbourne)
on May 5th, 2014

This is an awesome achievement, we need CSP plants in Australia.  They’ve been trying to get them built in South Australia for a few years new and the campaign continues.

In terms of the space it takes up, we have plenty here, look at this:

On the topic of power connections, there’s one to connect the north west of Australia to Asia…

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By Ray Barnes (Francistown)
on May 6th, 2014

Any idea on approximate total capital cost or cost per MW on a plant like this?

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By John Whitney (Louisville, KY 40206)
on May 9th, 2014

Per the US Energy Information Agency (2013 numbers):  Capital cost for a 50 MW solar thermal plant should be $5,067 per kW.  See page 6 at:

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By Bonnie Ford (Gresham, Ore)
on May 14th, 2014

How do these systems affect birds.  Can they land on the equipment with out getting burned?

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By alchemist of bristol
on May 24th, 2014

“Ask the majority of climate scientists: Carbon pollution from dirty energy is the main cause of global warming.”

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