A solar solution for world power

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 kilometre.

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% 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% 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 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 400 degrees Celsius and is used to power conventional steam turbines.

The mirrors are very large and create shaded areas underneath that 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 that really boosts the overall energy efficiency of these kinds of plants up to 80% to 90%,'' says Knies.

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

The German reports put an approximate cost on power derived from CSP. This is now about $50 per barrel of oil equivalent for the cost of building a plant. That cost is likely to fall sharply, to about $20, as the production of the mirrors reaches industrial levels. So CSP is competitive with oil, currently priced at about $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 desert land is plentiful and cheap but, more importantly, there is roughly three times as much sunlight in hot deserts as in Northern Europe.

This is why the reports recommend a collaboration between countries of Europe, the Middle East and Africa to construct a high-voltage direct current grid for the sharing of carbon-free energy.

"Contrary to what is commonly supposed it is entirely feasible, and cost-effective, to transmit solar electricity over long distances. Solar electricity imported to Europe would be among the cheapest source of electricity and that includes transporting it,'' he says. "CSP imports would be much less vulnerable to interruption than are current imports of gas, oil and uranium.''

Algeria already exports huge quantities of oil and gas to Europe via pipelines but has a vast potential resource in sunlight that could make it a complete energy supplier to Europe. Many members of the Opec oil cartel, which have worried that alternative energies would kill demand for their oil, are blessed with hot, sunny deserts that could become a further source of energy income.

The two reports make it clear that an HVDC grid around Europe and North Africa could provide enough electricity by 2050 to make it possible to phase out nuclear power and hugely reduce use of fossil fuels. - © Guardian News & Media 200

How To Build a Solar Generator

Affordable solar power using auto parts could make this electricity source far more available.

A set of prototype solar concentrators installed in Lesotho. (Courtesy of Amy Mueller.)

Demand for solar power is rapidly heating up (see "New Solar Technologies Fueled by Hot Markets"). But constructing and deploying large photovoltaic panels to generate electricity remains expensive. Now two groups at MIT are working on alternative approaches to solar-based electricity that could significantly cut costs -- and put the ability to harvest electricity from the sun into the hands of villagers in poor countries and backyard tinkerers alike.

During a stint in the Peace Corps in Lesotho in southern Africa, Matthew Orosz, an MIT graduate student advised by Harold Hemond, professor of civil and environmental engineering, learned that reflective parabolic troughs can bake bread. Now he plans to use these same contraptions to bring power to parts of Africa baked in sun but starved for electricity. His solar generators, cobbled together from auto parts and plumbing supplies, can easily be built in a backyard.

The basic design of Orosz's solar generator system is simple: a parabolic trough (taking up 15 square meters in this case) focuses light on a pipe containing motor oil. The oil circulates through a heat exchanger, turning a refrigerant into steam, which drives a turbine that, in turn, drives a generator.

The refrigerant is then cooled in two stages. The first stage recovers heat to make hot water or, in one design, to power an absorption process chiller, like the propane-powered refrigerators in RVs. The solar-generated heat would replace or augment the propane flame used in these devices. The second stage cools the refrigerant further, which improves the efficiency of the system, Orosz says. This stage will probably use cool groundwater pumped to the surface using power from the generator. The water can then be stored in a reservoir for drinking water.

The design uses readily available parts and tools. For example, both the feed pump and steam turbine are actually power-steering pumps used in cars and trucks. To generate electricity, the team uses an alternator, which is not as efficient as an ordinary generator, but comes already designed to charge a battery, which reduces some of the complexity of the system. And, like power-steering pumps, alternators, including less-expensive reconditioned ones, are easy to come by.

As a result, the complete system for generating one kilowatt of electricity and 10 kilowatts of heat, including a battery for storing the power generated, can be built for a couple thousand dollars, Orosz says, which is less than half the cost of one kilowatt of photovoltaic panels.

"You can't afford something that's designed for solar. You have to buy something that's mass-produced for something else -- that way the cost is reasonable," says Duane Johnson, owner of Red Rock Energy, in White Bear Lake, MN, who developed and sells thousands of the inexpensive LED-based sun-tracking devices Orosz uses to orient the solar concentrators. Most of the devices are used to position photovoltaic panels, he says, but some people are using them with old satellite dishes to concentrate heat and make steam. Sales of his devices have been growing 25 percent a year, a rate similar to that of the solar photovoltaics industry.

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