After decades of disappointment, with the consistent failure of our friends in the scientific community to produce a viable source of clean energy, a ray of light may be finally emerging. WAN’s Michael Hammond talks to Dr Gerry Wolff, the co-ordinator of the UK branch of the Trans-Mediterranean Renewable Energy Cooperation (TREC-UK)5.
Not only has a “new” technology surfaced but a joined-up plan has been put forward to power the whole of Europe. And it could work. This radical plan could provide the blueprint for a global solution to the provision of clean energy.
Solar power, whether using photovoltaic cells (PV) to generate electricity or direct heating through heat exchangers has been promising a breakthrough in economically viable power since I was at school, and believe me, that was a long time ago. So far it hasn’t delivered. Sure it’s got more efficient but the message now, as it always has been is, “it will be viable soon”
This century, we have entered the age of wind power in earnest but, as already reported on WAN (20 December 2007), claims for wind farm efficiency have often been over hyped and many proposals produce far more PR than electricity (the most frequent scam being to report the max possible power output rather the actual, often some 65% less). Bio- fuels have come and almost gone. Just a few years ago, they were forecast to be a major component of the clean energy solution but now the wider implications of the damage to the environment and in particular, the loss of food producing land have been exposed, this sector has been all but destroyed with a few exceptions. "The clearance of grassland releases 93 times the amount of greenhouse gas that would be saved by the fuel made annually on that land, said Joseph Fargione, lead author of a paper on the subject, and a scientist at the Nature Conservancy. The only possible exceptions could be sugar cane grown in Brazil, which takes relatively little energy to grow and is readily refined into fuel and bio-fuels that do not require cropping, such as those from agricultural waste products.
This all adds up to a very depressing picture with hopes of a real impact on Global Warming disappearing quicker than the polar ice caps. Until now. All eyes in the energy world are on an exciting solar experiment on the outskirts of Seville in Spain. Here, a new form of solar power, called Concentrating Solar Power (CSP), is being tested on a huge scale. Actually it’s not even new technology, having been trialled in California since the mid 1980s but on this scale it’s new. Currently, about 100,000 Californian homes are powered by CSP plants, new plants came on stream recently in Arizona and Spain, and others are being planned or built in several different parts of the world.
The principle of CSP is blindingly simple: take a collection of mirrors and use them to focus sunlight into one place. This super-heat is used to drive steam turbines to generate electricity in the conventional way. And yes, it is exactly the same principle as that magnifying glass we all used at school to burn a hole in a piece of paper. So the technology is not new. The only really new part is the computer tracking of the sun to maintain the optimum angle of the mirrors.
PS 10, as the “James Bond” like complex at Sanlucar la Mayor in Spain is cunningly called, comprises an 11 megawatt (MW) solar power tower fed by 624 large movable mirrors called heliostats. The focused sunlight produces extremely high temperatures (from 400 to over 1,000° c), enabling the production of steam, which is used to drive turbines in much the same way as conventional coal power stations. PS10’s capacity will be expanded to 300MW by 2013 thus providing power for the whole city of Seville.
Operator Abengoa claim their plant will prevent the emission of some 18,000 tonnes of CO2 per year.
Where this gets really interesting, and we see some real joined-up-thinking applied to major infrastructure, is TREC’s plan to roll this out to the whole of Europe. Their European Super Grid would transmit electricity collected from the southern desert belts via low-loss high voltage direct current (HVDC) transmission lines which only lose about 3% over 1,000 KM. Conventional coal-fired power stations can lose as much as 50-70% in the electricity generation process.
So where’s the catch? Well it’s not the cost. Using CSP, the cost of producing energy equivalent to a barrel of oil is currently about $50USD, (the real thing costs around $90USD) and TREC expect the cost to reduce in time to around $20USD. And if you were thinking the entire world would be taken up with solar farms, consider this: Current estimations show that an area less than 1% of the planet’s hot deserts could in theory provide the world’s entire electricity needs. Dr Wolff, who admits that his team are “starry eyed” about the project says, “It is rare for any technology to be totally positive in its effects, without any offsetting disadvantages. That said, I believe that there are good answers to most of the queries or doubts that may be raised about CSP.”
Dr Wolff believes the main objections will come from groups opposed to building on vast sections of desert. Even 1% is a huge area. Also, the transmission lines would have to traverse whole countries although he says it may be possible to run long sections under the sea and also to either convert or “piggy-back” some the of the existing AC transmission lines.
So do the lights go out when the sun goes in? Dr Wolff, “A useful feature of CSP is that it is possible to store solar heat in melted salts (such as nitrates of sodium or potassium, or a mixture of the two) so that electricity generation may continue through the night or on cloudy days. This overcomes a common objection to solar power: that it is not available when there is no sun.”
If you thought that things couldn’t get any better, well, there is a major fringe benefit to all of this. The waste heat created from CSP power generation can be used to desalinate large quantities of seawater – up to 40 litres per KW hour. Because many of the most suitable sites are in arid conditions and suffer chronic water shortages, this could help alleviate drought. Combine the provision of fresh to water with the shade from the collectors, (hectares of mirrors will produce hectares of shade) and you have a have a huge potential for a new horticultural industry to develop.
The implications of this plan are huge. Some 90% of the world’s population live within 2,700 km of a hot desert and are thus within the reach of TREC’s grid. So when we charge up our electric cars in 2020, we are not just hiding the carbon footprint back at the power plant, there will be no footprint.
Smoke and mirrors? I’m going with the real thing.
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