Sunrise for solar heat power

“Twenty years ago, everyone thought the solar era was upon us, and then the industry basically went away when oil and gas got cheap,” says Cara Libby, project manager at the Electric Power Research Institute (EPRI) in Palo Alto, Calif. Now, “it certainly appears that solar is here to stay.”

For their part, power companies like CSP for old-fashioned reasons. For one, it uses a technology – steam-driven turbines – that is familiar after decades of use in coal-fired plants.

CSP plants also have thermal inertia. That means that, if a cloud passes overhead, they can continue operating for a time with the heat already gathered, and that’s without storage.

Assuming no rechargeable batteries, photovoltaic fields, by contrast, stop producing electricity when clouds arrive.

Technology for storing heat in molten salts, meanwhile, promises to extend CSP plants’ generating capacity well into the night.

But the bottom line is that natural-gas prices are volatile, an unknown for anyone trying to turn a profit. By comparison, CSP costs – when stretched over the life of a plant – are mostly (80 percent, by one estimate) related to installation. CSP maintenance costs are relatively small, and the sun, its fuel, is free.

“There’s a hedging aspect in building a solar thermal plant,” says Nathaniel Bullard, a solar-sector analyst with New Energy Finance in Washington. “Right now it makes sense to burn gas; it’s really cheap. But you could, in the future, end up losing your shirt on it.”

Inventor Thomas Edison, a contemporary of Shuman’s and the man who gave us the system of steam-generated electricity distributed by wires, told friends late in his life that “I’d put my money on the sun and solar energy. What a source of power!”

Earth has a natural “sun belt,” a swath of relatively empty subtropical deserts including the US Southwest, the Sahara, the Middle East, and much of Australia. By one estimate, installing CSP plants in just 1 percent of the world’s deserts – an area slightly larger than Ireland – could supply all the world’s electricity.

The German Aerospace Center calculates that, assuming high voltage, transmediterranean transmission lines, just 6,023 square miles of CSP in North Africa could keep all of Europe electrified.

In the US, CSP plants in the Southwest could generate 11,000 gigawatts (GWs) of electricity, says Mark Mehos, principal program manager of concentrating solar power at the National Renewable Energy Laboratory (NREL) in Golden, Colo. That’s roughly 10 times all the electrical generating capacity currently in place, including coal, nuclear, solar, and hydroelectric – more than enough for the country’s energy needs.

In other words, there’s plenty of sun. The real challenge is making CSP technology competitive with coal.

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