Thu, Nov 30, 2006 - Page 9 News List

How mirrors can light up the world

Scientists say the global energy crisis can be solved by using the desert sun, rather than investing billions of dollars in nuclear fusion experiments

By Ashley Seager  /  THE GUARDIAN , LONDON

In the desert of North Africa is a vast source of energy that holds the promise of a carbon-free, nuclear-free electrical future for the whole of Europe, if not the world.

We are not talking about the vast oil and gas deposits underneath Algeria and Libya, or uranium for nuclear plants, but something far simpler -- the sun. And in vast quantities. Every year it pours down the equivalent of 1.5 million barrels of oil of energy for every square kilometer.

Many people think of solar power as a few panels on the roof of a house producing hot water or a bit of electricity. But according to two reports prepared for the German government, Europe, the Middle East and North Africa should be building vast solar farms in North Africa's deserts using a simple technology that more resembles using a magnifying glass to burn a hole in a piece of paper than any space age technology.

Two German scientists, Gerhard Knies and Franz Trieb, calculate that covering just 0.5 percent of the world's hot deserts with a technology called concentrated solar power (CSP) would provide the world's entire electricity needs, with the technology also providing desalinated water to desert regions as a valuable byproduct, as well as air conditioning for nearby cities.

Focusing on Europe, North Africa and the Middle East, they say, Europe should build a new high-voltage direct current electricity grid to allow the easy, efficient transport of electricity from a variety of alternative sources. Britain could put in wind power, Norway hydro, and central Europe biomass and geo-thermal. Together the region could provide all its electricity needs by 2050 with barely any fossil fuels and no nuclear power. This would allow a 70 percent reduction in carbon dioxide emissions from electricity production over the period.

CSP technology is not new. There has been a plant in the Mojave desert in California for the past 15 years. Others are being built in Nevada, southern Spain and Australia. There are different forms of CSP but all share in common the use of mirrors to concentrate the sun's rays on a pipe or vessel containing some sort of gas or liquid that heats up to around 400oC and is used to power conventional steam turbines.

The mirrors are very large and create shaded areas which can be used for horticulture irrigated by desalinated water generated by the plants. The cold water that can also be produced for air conditioning means there are three benefits.

"It is this triple use of the energy which really boosts the overall energy efficiency of these kinds of plants up to 80 percent to 90 percent," Knies said.

This form of solar power is also attractive because the hot liquid can be stored in large vessels which can keep the turbines running for hours after the sun has gone down, avoiding the problems associated with other forms of solar power.

The two German reports put an approximate cost on power derived from CSP. This is now around US$50 per barrel of oil equivalent for the cost of building a plant. That cost is likely to fall sharply, to about US$20, as the production of the mirrors reaches industrial levels.

It is about half the equivalent cost of using the photovoltaic cells that people have on their roofs. So CSP is competitive with oil, currently priced around US$60 a barrel.

Knies says CSP is not yet competitive with natural gas for producing electricity alone. But if desalination and air conditioning are added CSP undercuts gas and that is without taking into account the cost of the carbon emissions from fossil fuels. The researchers say a relatively small amount of the world's hot deserts -- only about half a percent -- would need to be covered in solar collectors to provide the entire world's electrical needs.

This story has been viewed 3815 times.
TOP top