A field of 600 mirrors reflects rays from the Sun
Posted on 05/03/2007 4:51:50 AM PDT by yankeedame
Last Updated: Wednesday, 2 May 2007, 21:12 GMT 22:12 UK
By David Shukman
Science correspondent, BBC News, Seville
A field of 600 mirrors reflects rays from the Sun
There is a scene in one of the Austin Powers films where Dr Evil unleashes a giant "tractor beam" of energy at Earth in order to extract a massive payment.
Well, the memory of it kept me chuckling as I toured the extraordinary scene of the new solar thermal power plant outside Seville in southern Spain.
From a distance, as we rounded a bend and first caught sight of it, I couldn't believe the strange structure ahead of me was actually real.
A concrete tower - 40 storeys high - stood bathed in intense white light, a totally bizarre image in the depths of the Andalusian countryside.
The tower looked like it was being hosed with giant sprays of water or was somehow being squirted with jets of pale gas. I had trouble working it out.
In fact, as we found out when we got closer, the rays of sunlight reflected by a field of 600 huge mirrors are so intense they illuminate the water vapour and dust hanging in the air.
The effect is to give the whole place a glow - even an aura - and if you're concerned about climate change that may well be deserved. It is Europe's first commercially operating power station using the Sun's energy this way and at the moment its operator, Solucar, proudly claims that it generates 11 Megawatts (MW) of electricity without emitting a single puff of greenhouse gas.
Ultimately, the entire plant should generate as much power as is used by the 600,000 people of Seville.
It works by focusing the reflected rays on one location, turning water into steam and then blasting it into turbines to generate power.
As I climbed out of the car, I could hardly open my eyes - the scene was far too bright. Gradually though, shielded by sunglasses, I made out the rows of mirrors (each 120 sq m in size) and the focus of their reflected beams - a collection of water pipes at the top of the tower.
It was probably the heat that did it, but I found myself making the long journey up to the very top - to the heart of the solar inferno.
Feeling the heat
A lift took me most of the way but cameraman Duncan Stone and I had to climb the last four storeys by ladder. We could soon feel the heat, despite thick insulation around the boiler.
David had to wear sunglasses
to shield his eyes from the glare
It was like being in a sauna and for the last stages the metal rungs of the ladders were scalding.
But our reward was the cool breeze at the top of the tower - and the staggering sight of a blaze of light heading our way from down below.
So far, only one field of mirrors is working. But to one side I could see the bulldozers at work clearing a second, larger field - thousands more mirrors will be installed.
Letting off steam
I met one of the gurus of solar thermal power, Michael Geyer, an international director of the energy giant Abengoa, which owns the plant. He is ready with answers to all the tricky questions.
What happens when the Sun goes down? Enough heat can be stored in the form of steam to allow generation after dark - only for an hour now but maybe longer in future.
The power station works by focusing
the reflected rays on one location.
Anyway, the solar power is most needed in the heat of summer when air conditioners are working flat out.
Is it true that this power is three times more expensive than power from conventional sources? Yes, but prices will fall, as they have with wind power, as the technologies develop.
Also, a more realistic comparison is with the cost of generating power from coal or gas only at times of peak demand - then this solar system seems more attractive.
The vision is of the sun-blessed lands of the Mediterranean - even the Sahara desert - being carpeted with systems like this with the power cabled to the drizzlier lands of northern Europe. A dazzling idea in a dazzling location.
Global Dewing.
Pretty neat I have to say.
Neat. I had a doubt though. If global warming is caused by the higher frequency rays of the sun coming into the earth’s atmosphere, getting converted to lower frequency rays after bouncing off the earth’s surface, and then getting trapped within the earth’s atmosphere because of the CO2 gas, instead of it simply escaping into space, then won’t this solar cell make matters much worse, by essentially “trapping” that heat and keeping it closer to the earth’s surface, far more efficiently? Whew.
Interesting. However, 11 Megawatts is not that much energy. Oyster Creek, one of the US’s oldest Nuke Plants produces 600 Megawatts and it is completely outdated. TMI-1 produces 850 MW.
Nukes are the way to go.
Now there's a thought!
Actually in Daggett, California (but even less people know where that is, about 10 miles east of Barstow) and unless your picture is 20 years old, it is of Solar Two. The same facility but after it was redesigned after 4~5 years of operation it was also renamed.
Solar One was built in 1981. Two and a half decades later and with all the advances in technology, it is still 3 times as expensive as conventional generation consuming fuel.
There's lots to be learned here from the good old "try, fail, learn; repeat as necessary model of problem solving.
Quote Beavis: Cook! Cook! Cook!
I used to work within sight of the tower, on old route 66.
All it will take is $180/Gallon oil (and free real estate) to make in competitive. I can hardly wait.
Hmmm... but can we build 100,000 of them in the US? (Based on the 11 MW reached, enough to power 4,000 homes, plus industrual use.)
How many acres does each plant consume? I’m thinking this would be excellent for California, where the need is most dire, and the weather is best nearby (Mojave Desert).
I’ve driven by that Barstow facility several times. First time (and really every time after that), it was an amazing sight. Looks like the air is on fire at the top of the tower. A photo just doesn’t capture the feel of actually seeing it...
Kinda like looking at arc welding from a distance....
France did something quite like this in the mid-70s.
The Themis solar power tower was opened by EDF in May 1983 in Targassonne, France (French Cerdagne). It had a power output of 2 MW. Construction started in 1979 at a cost of 300 millions French francs. It was based on an array of 201 mirrors which heated a boiler (a cavity lined with coolant tubes) at the top of a 100 m tower where the coolant (molten salts) carryied the thermal energy to a vapor generator, itself powering an electric turbine. The molten salts were potassium nitrate (53%), sodium nitrite (40%) and sodium nitrate (7%).
The coolant entry temperature was 250 °C and the exit temperature 450 °C. The vapor produced in the vapor generator was at 50 bar and 430 °C.
Rehabbed now, it will produce 1MW and half of the mirror mounts will be converted to hold solar cell panels.
Expensive, but fascinating.
Yeah, but just try siting it there. Plant siting is an environmental nightmare for these things. The environmentalists will kill you over it (harm to a "fragile" desert ecosystem, you know).
So the efficiency is only about 15%.
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