This month’s National Geographic has an interesting followup article on possible power sources after oil. Europe is way ahead of the U.S. in developing solar, wind and biomass. Excerpts from the article by Michael Parfit:
SOLAR:
On a cloudy day near the city of Leipzig in the former East Germany, I walked across a field of fresh grass, past a pond where wild swans fed. The field was also sown with 33,500 photovoltaic panels, planted in rows like silver flowers all turned sunward, undulating gently across the contours of the land. It's one of the largest solar arrays ever. When the sun emerges, the field produces up to five megawatts of power, and it averages enough for 1,800 homes.
Nearby are gaping pits where coal was mined for generations to feed power plants and factories. The skies used to be brown with smoke and acrid with sulfur. Now the mines are being turned into lakes, and power that once came from coal is made in a furnace 93 million miles (150 million kilometers) away.
Solar electric systems catch energy directly from the sun—no fire, no emissions. Some labs and companies are trying out the grown-up version of a child's magnifying glass: giant mirrored bowls or troughs to concentrate the sun's rays, producing heat that can drive a generator. But for now, sun power mostly means solar cells.
The idea is simple: Sunlight falling on a layer of semiconductor jostles electrons, creating a current. Yet the cost of the cells, once astronomical, is still high. My modest system cost over $15,000, about $10 a watt of capacity, including batteries to store power for when the sun doesn't shine.
Like most things electronic, solar power has been getting cheaper. "Thirty years ago it was cost-effective on satellites," says Daniel Shugar, president of PowerLight Corporation, a fast-growing California company that has built solar installations for clients including Toyota and Target. "Today it can be cost-effective for powering houses and businesses," at least where utility power is expensive or unavailable. Tomorrow, he says, it will make sense for almost everyone.
Martin Roscheisen, CEO of a company called Nanosolar, sees that future in a set of red-topped vials, filled with tiny particles of semiconductor. "I put some of that on my finger, and it disappeared right into my skin," he says. He won't say exactly what the particles are, but the "nano" in the company name is a hint: They are less than a hundred nanometers across—about the size of a virus, and so small they slip right through skin.
Roscheisen believes those particles promise a low-cost way to create solar cells. Instead of making the cells from slabs of silicon, his company will paint the particles onto a foil-like material, where they will self-assemble to create a semiconductor surface. The result: a flexible solar-cell material 50 times thinner than today's solar panels. Roscheisen hopes to sell it in sheets, for about 50 cents a watt.
"Fifty cents a watt is kind of the holy grail," says David Pearce, president and CEO of Miasolé, one of many other companies working on "thin-film" solar cells. At that price solar could compete with utilities and might take off. If prices continued to drop, solar cells might change the whole idea of energy by making it cheap and easy for individuals to gather for themselves. That's what techies call a "disruptive technology."
"Automobiles were disruptive to the horse and buggy business," Dan Shugar says. "PCs were disruptive to the typewriter industry. We believe solar electric systems will be disruptive to the energy industry."
With solar now providing less than one percent of the world's energy, that would take "a massive (but not insurmountable) scale-up," NYU's Hoffert and his colleagues said in an article in Science. At present levels of efficiency, it would take about 10,000 square miles (30,000 square kilometers) of solar panels—an area bigger than Vermont—to satisfy all of the United States' electricity needs. But the land requirement sounds more daunting than it is: Open country wouldn't have to be covered. All those panels could fit on less than a quarter of the roof and pavement space in cities and suburbs.
Wind:
One afternoon I stood in a field near Denmark's west coast under a sky so dark and heavy it would have put my own solar panels into a coma. But right above me clean power was being cranked out by the megawatt. A blade longer than an airplane wing turned slowly in a strong south breeze. It was a wind turbine.
The turbine's lazy sweep was misleading. Each time one of the three 130-foot (40-meter) blades swung past, it hissed as it sliced the air. Tip speed can be well over 100 miles (160 kilometers) an hour. This single tower was capable of producing two megawatts, almost half the entire output of the Leipzig solar farm.
In Denmark, turning blades are always on the horizon, in small or large groups, like spokes of wheels rolling toward a strange new world. Denmark's total installed wind power is now more than 3,000 megawatts—about 20 percent of the nation's electrical needs. All over Europe generous incentives designed to reduce carbon emissions and wean economies from oil and coal have led to a wind boom. The continent leads the world in wind power, with almost 35,000 megawatts, equivalent to 35 large coal-fired power plants. North America, even though it has huge potential for wind energy, remains a distant second, with just over 7,000 megawatts. With the exception of hydroelectric power—which has been driving machines for centuries but has little room to grow in developed countries—wind is currently the biggest success story in renewable energy.
There are other challenges. Like sailboats, wind turbines can be becalmed for days. To keep the grid humming, other sources, such as coal-fired power plants, have to stand ready to take up the slack. But when a strong wind dumps power into the grid, the other generators have to be turned down, and plants that burn fuel are not quickly adjustable. A wind-power bonanza can become a glut. Denmark, for example, is sometimes forced to unload power at uneconomic rates to neighbors like Norway and Germany.
What's needed for wind as well as solar is a way to store a large energy surplus. Technology already exists to turn it into fuels such as hydrogen or ethanol or harness it to compress air or spin flywheels, banking energy that can later churn out electricity. But most systems are still decades from becoming economically feasible.
On the plus side, both wind and solar can provide what's called distributed energy: They can make power on a small scale near the user. You can't have a private coal plant, but you can have your own windmill, with batteries for calm days. The more houses or communities make their own wind power, the smaller and cheaper central power plants and transmission lines can be.
In Europe's big push toward wind power, the turbines keep growing. But in Flagstaff, Arizona, Southwest Windpower makes turbines with blades you can pick up in one hand. The company has sold about 60,000 of the little turbines, most of them for off-grid homes, sailboats, and remote sites like lighthouses and weather stations. At 400 watts apiece they can't power more than a few lights.
But David Calley, Southwest's president, whose father built his first wind turbine out of washing machine parts, is testing a new product he calls an energy appliance. It will stand on a tower as tall as a telephone pole, produce up to two kilowatts in a moderate wind, and come with all the electronics needed to plug it into the house.
Many U.S. utilities are required to pay for power that individuals put back into the grid, so anyone in a relatively breezy place could pop up the energy appliance in the yard, use the power when it's needed, and feed it back into the grid when it's not. Except for the heavy loads of heating and air-conditioning, this setup could reduce a home's annual power bill to near zero. If, as Calley hopes, he can ultimately sell the energy appliance for under $3,000, it would pay for itself with energy savings within a few years.
Somewhere in this mix of the grand and the personal, there may be big numbers in wind too.
Biomass:
In Germany, driving from the giant wind turbine near Hamburg to Berlin, I regularly got an odd whiff: the sort-of-appetizing scent of fast food. It was a puzzle until a tanker truck passed, emblazoned with the word "biodiesel." The scent was of burning vegetable oil. Germany uses about 450 million gallons (1,700 million liters) of biodiesel a year, about 3 percent of its total diesel consumption.
Biomass energy has ancient roots. The logs in your fire are biomass. But today biomass means ethanol, biogas, and biodiesel—fuels as easy to burn as oil or gas, but made from plants. These technologies are proven. Ethanol produced from corn goes into gasoline blends in the U.S.; ethanol from sugarcane provides 50 percent of automobile fuel in Brazil. In the U.S. and other nations, biodiesel from vegetable oil is burned, pure or mixed with regular diesel, in unmodified engines. "Biofuels are the easiest fuels to slot into the existing fuel system," says Michael Pacheco, the National Bioenergy Center director.
What limits biomass is land. Photosynthesis, the process that captures the sun's energy in plants, is far less efficient per square foot than solar panels, so catching energy in plants gobbles up even more land. Estimates suggest that powering all the world's vehicles with biofuels would mean doubling the amount of land devoted to farming.
At the National Bioenergy Center, scientists are trying to make fuel-farming more efficient. Today's biomass fuels are based on plant starches, oils, and sugars, but the center is testing organisms that can digest woody cellulose, abundant in plants, so that it too could yield liquid fuel. More productive fuel crops could help as well.
One is switchgrass, a plant native to North America's prairies that grows faster and needs less fertilizer than corn, the source of most ethanol fuel made in the U.S. It also thrives on land unfit for other crops and does double duty as a source of animal food, further reducing the pressure on farmland.
"Preliminary results look promising," says Thomas Foust, the center's technology manager. "If you increase automobile efficiency to the level of a hybrid and go with the switchgrass crop mix, you could meet two-thirds of the U.S. transportation fuel demand with no additional land."
But technically possible doesn't mean politically feasible. From corn to sugarcane, all crops have their own lobbyists. "We're looking down a lot of alleys," says Pacheco. "And every alley has its own vested interest group. Frankly, one of the biggest challenges with biomass is that there are so many options."
additional portions of the magazine article at:
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