Level 5 Reading 5B

Reading 5B

PLUGGING INTO THE SUN Early on a clear November morning in the Mojave Desert, a full moon is sinking over the gigawatt glare of Las Vegas. Nevada Solar One is sleeping. But the day's work is about to begin. It is hard to imagine that a power plant could be so beautiful: 400 hectares of gently curved mirrors lined up like canals of light. Parked facing the ground overnight, they are starting to awaken— more than 182,000 of them—and follow the sun. "Looks like this will be a 700-degree day," says one of the operators in the control room. His job is to monitor the rows of mirrors as they concentrate sunlight on long steel pipes filled with circulating oil, heating it as high as 400 degrees Celsius. The heat produces steam, driving a turbine and dynamo, pushing as much as 64 megawatts onto the grid— enough to electrify 14,000 households, or a few Las Vegas casinos. When Nevada Solar One came online in 2007, it was the first large solar plant to be built in the United States in more than 17 years. During that time, solar technology blossomed elsewhere. The owner of Nevada Solar One, Acciona, is a Spanish company, and the mirrors were made in Germany. Putting on hard hats and dark glasses, plant manager Robert Cable and I drive out to take a closer look at the mirrors. Men with a water truck are hosing some down. "Any kind of dust affects them," Cable says. On a clear summer day with the sun directly overhead, Nevada Solar One can convert about 20 percent of the sun's rays into electricity. Gas plants are more efficient, but this fuel is free. "If we talk about geothermal or wind, all these other sources of renewable energy are limited in their quantity," says Eicke Weber, director of the Fraunhofer Institute for Solar Energy Systems, in Freiburg, Germany. "The total power needs of the humans on Earth is approximately 16 terawatts," he adds. (A terawatt is a trillion—1,000,000,000,000—watts.) In a few years, that number is expected to grow to 20 terawatts. "The sunshine on the solid part of the Earth is 120,000 terawatts," says Weber. "From this perspective, energy from the sun is virtually unlimited." Tapping the Sun Solar energy may be unlimited, but its potential is barely tapped. Today, solar power accounts for a tiny fraction of U.S. electricity production—just over 2 percent. "But," said Robert Hawsey, an associate director of the National Renewable Energy Laboratory (NREL) in Golden, Colorado, "that's expected to grow. Ten to 20 percent of the nation's peak electricity demand could be provided by solar energy by 2030." Achieving that level will require government help. Nevada Solar One was built because the state had set a deadline requiring utilities to generate 20 percent of their power from renewable sources by 2015. During peak demand, the solar plant's electricity is almost as cheap as that of its gas-fired neighbor— but that's only because a 30 percent federal tax credit helped offset its construction costs. The aim now is to bring down costs and reduce the need for subsidies and incentives. To achieve this, NREL's engineers are studying mirrors made from lightweight polymers instead of glass, and tubes that will absorb more sunlight and lose less heat. They're also working on solar power's biggest problem: how to store some of the heat produced during daylight hours for release later on. Nevada Solar One use solar thermal energy (STE) technology, which collects the sun's rays via mirrors to produce thermal energy (heat). Another method is to convert sunlight directly into electricity with photovoltaic (PV) panels made of semiconductors such as silicon. Back in the 1980s, an engineer named Roland Hulstrom calculated that if PV panels covered just three-tenths of a percent of the United States, they could electrify the entire country. Years later, PV panels contribute a small—but growing—amount to the nation's electricity supply. On rooftops in California, Nevada, and other states with good sunshine and tax incentives, they are increasingly common—almost as familiar as air conditioners. For years, PV power was not as developed as solar thermal, but today it is the dominant solar power technology. Massive investment, government incentives, and technological breakthroughs have caused prices for PV panels to fall dramatically. In 2009, the U.S. company First Solar became the first to manufacture thin-film solar cells at a cost of under a dollar a watt—close to what's needed to compete with fossil fuels.

Germany's Solar Solution On a cold December morning west of Frankfurt, Germany, fog hangs frozen in the trees, and clouds block the sun. In the town of Morbach, the blades of a 100-meter-high wind turbine appear and disappear in the gloom, while down below, a field of photovoltaic panels struggle for light. Considering its unpredictable weather, who would have thought that Germany would transform itself into one of the top producers of photovoltaic power in the world? A fraction of Germany's five-gigawatt photovoltaic power comes from centralized the plants like the one at Morbach. With land at a premium in Germany, solar panels can be found mounted on rooftops, farmhouses, even on soccer stadiums and along the autobahn. The panels, dispersed across the German countryside, are all connected to the national grid. The solar boom has completely transformed towns like "sunny Freiburg," as the tourist brochures call it. The town sits at the edge of the Black Forest in the southern part of the country. Towering walls of photovoltaics greet visitors as they arrive at Freiburg's train station. Across the street from a school covered with photovoltaic panels is Solarsiedlung (" solar settlement"), one of the town's condominium complexes. "We are being paid for living in this house," said Wolfgang Schnurer, one of Solarsiedlung's residents. The day before, when snow covered the roof, Schnurer's system produced only 5.8 kilowatt-hours, not enough power for a German household. But on a sunny day in May, it yielded more than seven times that much. In Germany, regulations require utility companies to pay even the smallest PV producers a premium of about 50 euro-cents a kilowatt-hour. In 2008, Schnurer's personal power plant yielded over 6,000 kilowatt-hours, more than double the amount the family consumed. When they subtracted their usage from the amount they produced, the family found they were more than 2,500 euros (nearly $3,000) in profit. Anybody who installs a PV system is guaranteed above-market rates for 20 years— the equivalent of an 8 percent annual return on the initial investment. "It is an ingenious mechanism," Eicke Weber said. "I always say the United States addresses the idealists, those who want to save the planet. In Germany, the law addresses anyone who wants to get 8 percent return on his investment for 20 years." In total, Germany now generates over 6.5 percent of its electricity annually from solar energy, whereas the United States generates less than half this amount. The largest photovoltaic installation in the United States— the Solar Star in California—is only the 11th largest in the world. Nearly all the bigger ones are located in either China or India. But in the United States, too, there is a gathering sense that the time for solar energy has arrived— if there is a commitment to jump-start the technology. "Originally it seemed like a pie-in-the-sky idea," said Michelle Price, the energy manager at the Nellis Air Force base outside Las Vegas. "It didn't seem possible." Many things seem possible now.

♪

♪