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And there's always been one big problem with solar power. It only generates electricity when the sun is shining. There are batteries to store electricity, but they're expensive. Here's another option. A company has built a large solar plant in the Nevada desert that can store the sun's energy for up to 10 hours. NPR's Jeff Brady traveled to Nevada to learn how it works.
JEFF BRADY, BYLINE: In the small town of Tonopah, Nev., locals like Vicki Walker have taken notice of the unusual-looking power plant that was built north of here.
VICKI WALKER: And then in the middle of this valley is a huge, tall, tall tower surrounded by circle after circle after circle of what looks like solar panels. Turns out they're mirrors.
BRADY: Those circles of mirrors cover an area one-and-three-quarters of a mile wide. Each mirror is the size of a billboard. Collectively, they direct heat from the sun to a 640-foot-tall tower in the middle. The top of that tower is glowing white-hot. It's an impressive sight from far off, but we want to get a closer look. I head out to meet Kevin Smith, CEO of SolarReserve. His company built the Crescent Dunes Solar Energy Plant.
KEVIN SMITH: This is really the first utility-size project of this type in the world.
BRADY: At full capacity, Smith says, the plant generates enough electricity to power 75,000 homes in Nevada. But it's how the power is generated that's most interesting. The key is molten salt. You can't see this special kind of salt because it's flowing through a contained system of pipes.
SMITH: It actually looks like water. It's clear. It flows like water.
BRADY: Smith says the molten salt has to stay above 450 degrees to remain liquid. Then it's sent up that tower to the glowing tip. When the salt comes back down, it's been heated to over 1,000 degrees. The heat from the salt makes steam to power a generator. That can be done right away and for up to 10 hours later. Smith says that flexibility is very important to the local utility.
SMITH: That's the whole concept here, is that this facility would operate just like a natural gas or a coal or a nuclear facility - turn this on and off when they want. We have energy and storage so we can generate at night.
BRADY: Imagine that - a solar power plant electrifying the Las Vegas Strip at night. Of course, in the energy world, things are never simple. During a test last year at the plant, observers with a video camera recorded birds flying into the heat from all of those mirrors and being incinerated.
(SOUNDBITE OF YOUTUBE VIDEO)
UNIDENTIFIED MAN #1: Poof.
UNIDENTIFIED MAN #2: Got it. Got it. I recorded that one. Yep.
UNIDENTIFIED MAN #1: Poof. There goes another one.
UNIDENTIFIED MAN #2: Got it.
BRADY: The plant is on federal land. The Bureau of Land Management says the company fixed the problem by adjusting where mirrors are pointed at certain times. And there's been fewer than five bird deaths a month since. The group Basin and Range Watch is suing the agency to get raw data from biologists to confirm that. Laura Cunningham is the executive director.
LAURA CUNNINGHAM: We support solar, and most environmental groups do, of course. So we're in a little bit of an unpopular position of trying to defend solar but then criticizing some solar.
BRADY: Cunningham wants plants like this built closer to where people live and away from wild areas. Another issue is cost. Electricity from this facility is more expensive than power from, say, a natural gas plant. Back at SolarReserve, CEO Kevin Smith says his company learned a lot from building this first project. He says subsequent plants will be cheaper. That'll reduce the cost of electricity because once the plant is built, the fuel is free. And the ability to store solar power adds value.
SMITH: And we really think we've cracked the code here with energy storage. And we can take this technology and bring it worldwide.
BRADY: Smith says work should begin soon on the company's second solar plant with heat storage. It'll be built in South Africa. Jeff Brady, NPR News.
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