Tapping Solar for Places Where the Sun Don't Shine

We've got deserts with no people and people with no power. So, like an electrical Reese's Peanut Butter Cup, we've got thinkers with an idea ...
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We've got deserts with no people and people with no power. So, like an electrical Reese's Peanut Butter Cup, we've got thinkers with an idea ...

Solar researchers will tell you that energy from the sun striking the Earth for a mere 40 minutes is equivalent to global energy consumption for a year. But then they'll admit that solar has been a dark horse in the race to a clean-power future.

Sometimes, though, horses come from behind to win. Researchers on four continents are putting their money on a new way of harnessing solar energy that, they say, could render fossil fuels obsolete.

Some renewables, notably solar and wind, stay in the backfield because they don't provide power on a 24/7 basis. If the energy they generate could be stored and doled out around the clock, there might be some new favorites.

Three U.S. researchers laid out such a scenario for the United States in an article titled "The Solar Grand Plan," which appeared in the January issue of Scientific American. Meanwhile, the Club of Rome, an international think tank of leaders in politics, business and science, is shepherding a similar concept for Europe.

Central to both plans is the need for high-voltage direct current, or HVDC, lines to transmit vast wattages from the desert solar arrays to urban areas — from the Southwest desert to air conditioning terminals throughout the United States or from sun-baked North Africa to Europe.

And amid a backdrop of worries about climate change and spiraling energy prices, more people are willing to bend an ear to these grand schemes.

Made in America
The Solar Grand Plan calls for erecting photovoltaic arrays and concentrating solar parabolic troughs over massive areas of desert land in the Southwest. The authors say this could provide 69 percent of the U.S.'s electricity and 35 percent of its total energy needs (including transportation) by 2050.

Excess power — stored in the form of compressed air — from a system of photovoltaic-powered plants would be fed by pipeline to caverns throughout the country to be released (much as compressed natural gas is released) to provide a constant source of power. Molten salt or other thermal storage materials could hold energy — stored as heat — from the concentrated solar troughs to power a plant when the sun goes down.

Two other studies — albeit from solar partisans — support the feasibility of the plan. The National Solar Energy Society and another by the (anti-nuclear) Nuclear Policy Research Institute and the Institute for Energy and Environmental Research have come to similar conclusions.

Blue Skies in the Mediterranean
The Club of Rome's Trans-Mediterranean Renewable Energy Cooperation initiative, known as Desertec, is also looking to desert lands. Europe doesn't have any, but Middle Eastern and North African (MENA) countries do. Population-dense European countries, meanwhile, have a continuing need for energy and are particularly keen on green energy to offset global warming concerns, while many MENA countries are looking for new clean water sources.

The Desertec plan is at least as "grand" as the American vision, calling for a "supergrid" of sustainable power systems along the North African desert and coast, connecting to the Middle East and spanning the Mediterranean to Europe.

Wind, solar, hydro, geothermal and biomass are included in the mix, although solar is by far the biggest projected producer.

Excess solar in MENA countries would be used to run energy-hungry desalination plants, helping meet those nation's demands for additional potable water.

Projections are that by 2050 such a system could result in MENA-supplied green energy comprising 17 percent of European energy, while domestic renewables would provide about 65 percent.

Technical Differences
The Desertec plan relies much more on "concentrated solar" than the Solar Grand Plan, which calls for about an 80/20 mix of photovoltaic farms and concentrated solar plants. (Authors are now estimating the mix could be 50/50, depending on how each technology pans out.)

A concentrated system uses mirrors and troughs to capture solar energy, which heats a fluid to produce steam to run a turbine. Excess thermal energy is stored in molten salt to be released for power at night or during peak periods. Unlike photovoltaic solar cells, which can produce electricity with varying levels of exposure to the sun, concentrated solar systems require direct sunlight.

With photovoltaics, the sun creates electricity in a single step without the intervening steam-production of the concentrated method. But traditional photovoltaic cells are expensive and fiddly, while concentrated methods are straightforward and comparatively cheap.

To get around the cost issues with silicon solar cells, thin-film solar cells are the chosen photovoltaic method for the Solar Grand Plan. Thin-film ultimately should be cheaper to manufacture than the more widely known silicon solar cells and as efficient.

Both plans boast massive potential electrical generation in which even the leftovers would have enormous benefits. The U.S. plan estimates enough excess electricity to power to 80 percent of the country's transportation needs by 2050 (using plug-in electric cars). The Europe-MENA plan, meanwhile, addresses water shortages that it estimates could triple in MENA countries by the same year.

Pipe Dreams?
Of course, both plans still rest comfortably only in the heads of their respective progenitors.

Hans Muller-Steinhagen of the German Aerospace Center, a spokesperson for Desertec, recently noted that such a large endeavor was much more of a "natural" for the United States, given that the first concentrating solar plants were built in California and Nevada and cross-country collaboration isn't required, as it is for Desertec.

But Desertec is further along with plans for an HVDC line, itself an economic and engineering challenge. HVDC lines have been built, but they are still relatively rare and will require an investment in technology to bring down unit cost, just as both plans depend on investment in technology to bring down solar generating costs. Which brings us to money.

Huge sums of money and huge swaths of land and are needed for both plans — as is a desire to plough ahead regardless of market changes. President Jimmy Carter championed solar energy in the late 1970s when oil embargoes threatened the country's energy security, but Ronald Reagan didn't have the same devotion to renewables and falling prices for oil and gas in the mid-1980s cooled the fervor for the more-costly alternatives.

James Mason, one of the authors of the Solar Grand Plan, predicts this time we won't see another fall in the cost of fossil fuels. The good news, he says, is that a clean energy source could be supplying 3,000 gigawatts of power to the country by 2050, assuaging global warming worries, slashing energy import costs and ending a decades-long oil-dependent foreign policy.

The price tag: $420 billion in subsidies for solar companies and another $500 billion for the HVDC lines criss-crossing the continent. (For comparison purposes, the U.S. Department of Energy budget request for fiscal 2009 is $25 billion with $1.3 billion requested for its Office of Energy Efficiency and Renewable Energy.)

Desertec estimates power plants in its plan would cost roughly $542.5 billion in U.S. dollars, while several HVDC lines from North Africa to Europe would cost about $77.5 billion. (The key manufacturers of HVDC lines are currently European.)
According to Mason, an economist and director of both the Solar Energy Campaign and the Hydrogen Research Institute, the rising price of fuel makes these price tags look more attractive.

Mason refers to a compressed air thermal storage system used in conjunction with a natural gas plant that went online in 1991 in McIntosh, Ala. — the only system built in the United States to date.

It turned out to be a money loser because gas and oil generation remained cheaper, but, Mason said, when the average contract price for peak load electricity from natural gas plants reaches $7 per million BTU, the solar compressed/air system will be competitive with oil and gas generation.

In 2006, the natural gas contract price for electricity was $6.38/million BTU and Mason expects the 2007 numbers, released in October, will exceed $7/million BTU.

And that assumes the fossil fuels remain accessible. Developing countries such as China and India have huge population bases and their need for fuel will assure increased demand into the horizon as their standards of living rise. Recently Dutch Royal Shell estimated that demand for oil will exceed supply within seven years.

Mason is so sure of his vision — and his math — that he says the transition period between fossil fuels and alternative energy sources will be so narrow as to require a "World War II-type" effort.

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