Thursday, Jan. 15, 2009

Out of Africa: Saharan Solar Energy

Take off from almost any city in Europe and head south across the Mediterranean, and you will notice a dramatic shift in the light within an hour or two. An angled brightness pierces the windows as passengers peel off sweaters and jackets. Then for the next four or five hours you can gaze out at the forbidding landscape below: a sweltering expanse of yellow sand and rock roughly double the size of Western Europe but almost totally devoid of buildings, roads and people. You are looking at the world's biggest desert.

For years the Sahara has been regarded by many Europeans as a terra incognita of little economic value or importance. But this perception may be headed for a drastic overhaul. Politicians and scientists on both sides of the Med are beginning to focus on the Sahara's potential to power Europe for centuries to come. These people believe the 3.32 million-sq.-mi. (8.6 million sq km) desert's true worth lies in the very thing long regarded as its biggest liability: its arid emptiness. Some patches of the Sahara reach 113 degrees F (45 degrees C) on many afternoons. It is, in other words, a gigantic natural storehouse of solar energy.

A few years ago, scientists began to calculate just how much energy the Sahara holds. They were astounded at the answer. In theory, a 35,000-sq.-mi. (90,600 sq km) chunk of the Sahara — smaller than Portugal and a little over 1% of its total area — could yield the same amount of electricity as all the world's power plants combined. A smaller square of 6,000 sq. mi. (15,500 sq km) — about the size of Connecticut — could provide electricity for Europe's 500 million people. "I admit I was skeptical until I did the calculations myself," says Michael Pawlyn, director of Exploration Architecture, one of three British environmental companies comprising the Sahara Forest Project, which is testing solar plants in Oman and the United Arab Emirates. Pawlyn calls the Sahara's potential "staggering."

At this point, no one is proposing the creation of a solar power station the size of a small country. But a relatively well developed technology exists, which proponents say could turn the Sahara's heat and sunlight into a major electrical source — concentrating solar power (CSP). Unlike solar panels, which convert sunlight directly into electricity, CSP utilizes mirrors to focus light on water pipes or boilers, generating superheated steam to operate the turbines of generators. Small CSP plants have produced power in California's Mojave Desert since the 1980s. The Sahara Forest Project proposes building CSP plants below sea level (the Sahara has several such depressions) so that seawater can flow into them and be condensed into distilled water for powering turbines and washing dust off the mirrors. Wastewater would be used to irrigate areas around the stations, creating lush oases — hence the forest in the group's name.

But scaling up the technology to produce meaningful quantities of electricity means building sprawling arrays of mirrors and pipes across hundreds of miles of remote terrain — and that will be expensive. Gerry Wolff, an engineer who heads DESERTEC, an international consortium of solar-power scientists, estimates it will cost about $59 billion to begin transmitting Sahara power by 2020.

Follow the Sun
Building plants is just part of the challenge. One of the drawbacks to CSP technology is that it works at maximum efficiency only in sunny, hot climates — and deserts tend to be distant from population centers. To supply Europe with 20% of its electricity needs, more than 12,000 miles (19,300 km) of high-voltage direct-current (HVDC) cables would need to be laid under the Mediterranean, says Gunnar Asplund, head of HVDC research at ABB Power Technologies in Ludvika, Sweden. Indeed, to use renewable sources of power, including solar, wind and tidal, Europe will need to build completely new electrical grids. That's because the aging alternating-current lines, built largely for the coal-fired plants that supply 80% of Europe's power, are inadequate for a larger load. Germany's government-run Aerospace Center, which researches energy, estimates that replacing those lines could raise the cost of building solar plants in the Sahara and sending significant amounts of power to Europe to about $465 billion over the next 40 years. Generous government subsidies will be needed — a potentially unpopular idea while Europe is in recession. "Of course it costs a lot of money," says Asplund. "It's a lot cheaper to burn coal than to make solar power in the Sahara."

Perhaps for this reason, political support has been slow to build. French President Nicolas Sarkozy proposed new solar-power construction in the Sahara last year, when he founded the Mediterranean Union, a loose grouping of 43 countries in Europe, North Africa and the Middle East. But critics say that such ambitious plans ignore the huge costs and political complications involved. "They underestimate the real production costs of the Sahara's sandstorms, and the fact that it would take many, many years to build the transmission grid," says Hermann Scheer, a German MP who backed government-subsidized rooftop solar panels for German households. "It is not true that it would lead to cheaper power if you take into account all these elements."

But the dreamers are pushing ahead. Seville engineering company Abengoa is building one hybrid solar-thermal plant in Algeria and another in Morocco, while a third is being built in Egypt by a Spanish-Japanese joint venture. The next step will be to get cables in place. Although the European Parliament recently passed a law that aids investors who help the continent reach its goal of getting 20% of its power from renewable energy by 2020, it could take years to create the necessary infrastructure. "I fear the E.U. could talk this thing to death," says Nicholas Dunlop, secretary-general of the London-based NGO e-Parliament.

In late November Dunlop organized a meeting in Paris of about 60 European and North African engineers and environmentalists to discuss how to prod officials into action. Almost all of those who gathered in a conference room in France's Environment Ministry said there was widespread ignorance about solar power within their governments, and no sense of urgency to spur its development. Dunlop believes it is futile to wait for a Europe-wide program to build plants and create a supergrid capable of transmitting clean energy across the continent. Instead, he thinks companies should begin transmitting small amounts of solar power as soon as the North African plants begin operating, by linking a few cable lines under the Med. "I call it the Lego method," he says. "Build it piece by piece." If it can be shown that power from the Sahara can be produced profitably, he says, companies and governments will soon jump in. If they do, perhaps airplane passengers will one day count the mirrors and patches of green sprouting across the Sahara instead of staring at sand.

Hotting Up
Vast solar fields in the Sahara might become the biggest sustainable energy source the world has ever seen, powering whole continents. A glimpse of the desert's potential in numbers:

The average constant amount of solar energy reaching the earth in watts per sq m Source: Univ. of Oregon Solar Monitoring Lab

Percentage of light falling on the Sahara and Middle East deserts that could provide all of Europe's energy needs Source: German Aerospace Center

Area in sq. mi. (slightly smaller than Portugal) that could, with the right solar technology, yield the same energy as all the world's power plants combined Source: German Aerospace Center