Amid the green wheat fields, oak groves and ancient olive trees of Andalusia, a giant solar energy farm shimmers like a silver sea. Even under cloudy skies, the arrays of mirrors and massive towers sprawling over three square miles are an arresting sight.
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Twenty miles west of Seville, the Solúcar solar farm, built by the company Abengoa, is part of Spain’s push to produce more energy from renewable sources. The nation currently produces up to 3.65 gigawatts of power from the sun, second in the world after Germany. Those gigawatts make up about 3 percent of the country’s power, the highest percentage in the world. (The United States generates less than 1 percent of its energy from the sun.) Spain’s solar output is expected to rise in the next three years to seven gigawatts, enough to supply about ten million people—the combined population of Madrid and Barcelona—with electricity during the day.
The Solúcar farm is pioneering technologies that are being replicated in the United States, including concentrated solar power, or CSP. While traditional solar panels use photovoltaic cells to convert the sun’s rays directly into electricity, CSP deploys huge banks of mirrors to focus solar radiation; the intense heat drives steam turbines, producing electricity in a process similar to the one used in coal-or oil-fired plants, but without the greenhouse gas emissions.
At the Solúcar site, two concrete towers—one about 50 stories tall, the other 35—collect light reflected by 1,879 enormous glass mirrors, each one 33 feet high and 40 feet wide. The mirrors, called heliostats, cover some 345 acres. They face south and are turned to follow the sun as it crosses the sky.
The smaller CSP tower began providing power in 2007, the larger one in May 2009. Together, they produce 31 megawatts. By 2013, when Solúcar is finished adding another tower plant and other installations, Abengoa expects the CSP facility to generate 300 megawatts, enough energy to power 220,000 households, or all of metropolitan Seville.
“These commercial tower plants are unique in the world,” Valerio Fernández, Solúcar’s operations manager, told me in his office overlooking the mirrored fields. (He was not counting a small, five-megawatt power tower operated in Lancaster, California, by the American company eSolar, or a demonstration tower the Spanish government runs in Almería.) “Today, however, they’re on vacation,” he added, with a shrug.
When it’s raining or overcast—like the cool gray March day I visited—the solar installation shuts down. But photographs of the CSP site at its best are otherworldly: towers glowing with shafts of light, an effect caused by reflected sunlight passing through water vapor and dust in the air. Though you might think the south of Spain is an ideal solar energy site, Fernández said the company expects bad weather to reduce or halt energy production around 80 days a year, generally between November and March.
“If we are seeking to make solar power more efficient, there are better places than Seville,” Fernández told me. He gestured to a wall map of the world with shaded bands representing solar energy potential: Andalusia was tan, the Mojave Desert of California and Nevada brown, and the Sahara darker still.
“The Mojave has about 30 percent higher solar radiation than we have here, so installing the same plants there will reduce the cost of electricity by 30 percent,” he said. Efficiency is even higher for the scorching Sahara, where Abengoa and Desertec, a European consortium, aim to build solar facilities that will deliver power to Europe through cables beneath the Mediterranean.
Fernández hefted a three-inch-wide piece of steel pipe off a bookshelf and handed it to me. It was from a tube in which water is converted to steam atop a CSP tower, and it had been painted black. “The blacker they are,” he explained, “the better they absorb radiation.”