Can We Store Energy From the Sun and Wind?

26 November 2012
Published in Energy
Written by  Ross Chambless
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Can We Store Energy From the Sun and Wind? Ross Chambless

In the sagebrush desert between Milford and Delta, the constant wind can drive you mad. But in Utah this wind also means power. Fields of giant wind turbines turn here almost constantly, weaving wind into electricity that's transmitted to California. Still, most Utahns get 3 quarters of their electricity from fossil fuels like coal or natural gas.

Utah is 40th overall among U.S. states in generating renewable energy. But according to a 2010 Utah state collaborative study, this western pocket of the state has abundant resources for generating wind, solar, and geothermal energy. Energy developers are gauging the possibilities, but utilities hesitate to embrace renewable energy on a large scale. Sunlight and wind ebb and flow with the cycles of nature, making it difficult to integrate their energy into the utility grid. David Eskelson with Rocky Mountain Power says there are many difficulties with solar energy.

"Solar is great. But it doesn't follow customer behavior as a utility product. As a homeowner wanting to shave kilowatts off their bill, it's great." But says Eskelson, "As a large central station, a utility tool, it doesn't really help us because it peaks around mid-day. The peak demand for electricity on our system on a summer day, really gets started about 3 in the afternoon and stays high until 9 or 10 pm."

Capturing Wind and Solar Power in Salt Caverns

What if all this sporadic energy from the sun and wind could somehow be captured and stored for times when it's most needed? The solution might just be hidden below the ground says Rob Webster.

"When we identified this salt area in the West, about 5 years ago, it was in a very strategic location."

Webster is a geologist and co-founder of Magnum Gas Storage. He says his company began exploring an underground salt deposit in this region a few years ago. They partnered with the state of Utah and asked Sandia National Labs with the Department of Energy to help them drill core samples and do other tests.

"Low and behold, at the end of that period and a lot of money spent, we really have world-class salt deposit here in Utah, that has high feasibility for development," says Webster. "And one that we think will serve as an "energy hub" for gas and electric integration for decades to come."

The deposit is more than 2 miles across, 1 mile deep, and impermeable to the elements. Webster says Magnum is now looking to carve out its first large cavern – the size of the empire state building - for storing natural gas. But he says such a cavern could also be used for something called compressed-air-energy-storage, or CAES. Stephen Bauer is a geo-mechanics engineer with Sandia Labs.

"Basically, you store the energy as a compressed gas by pumping it underground when electricity is inexpensive, or there's extra energy that you can't use otherwise," says Bauer. "And you let it out, and harvest that energy."

CAES can store hundreds of megawatt-hours of surplus energy in the form of compressed air. When renewable power sources can't keep up with demand, stored compressed air is released, driving turbines that generate supplemental electricity for the grid.

"So it's simple in concept. It's simple in practice. And I think it's a viable industry the country could become involved in," says Bauer.

Utility-scale CAES facilities currently exist in only two places in the world – one in Germany, and the other in McIntosh, Alabama – and both are over 20 years old. And while other types of storage are being studied in Utah, like pumped hydro storage and large battery technologies, Bauer says CAES is a proven technology that can be cost-effective and reliable. That's why it's being explored and developed across the U.S.

Storing Renewable Energy in the Future

"We don't really need energy storage to support renewables right now. It's just preparing for the future," says Arun MakHijani.

Makhijani is president of the Institute for Energy and Environmental Research in Maryland, and he's studied Utah's renewable energy potential. He explains that storage would only be necessary once renewable energy makes up a sizable percentage of the energy that's feeding the grid.

"You begin to need storage when you have 20 to 25 percent of your capacity filled by renewables, on average," says Mahhijani. "So that sometimes it's 50 percent, 60 percent, 70-percent. So those are the times when storage helps make your system more flexible."

In 2010, Makhijani compiled a report commissioned by HEAL Utah, an environmental advocacy nonprofit. He projects that compressed air energy storage could help Utahns meet all of their energy needs. In fact, combined with a smarter grid, more transmission, and efficiency measures, his report says Utahns could get by with just wind and solar resources alone.

"You don't have to use all of them. A fraction of them would be enough," says Makhijani.

But developing a CAES facility would require time, and, of course, money. And with natural gas prices at record lows, Stephen Bauer says such a facility right now would be a risky bet for investors.

"A significant bet – a 2 to 3 hundred million dollar bet – that the economics are correct in 2 to 3 years," says Bauer. "It would take that long to develop the cavern. And at the same time, finance the surface facilities."

So far PacifiCorp – the utility that supplies most of Utah with power – has no plans for developing CAES. But since 2012, Utah permits large private power users to purchase electricity directly from renewable sources, meaning businesses could push the market for green energy. And considering that this age of cheap and abundant natural gas will eventually fizzle out, Makhijani says businesses with long-term vision will ultimately have the advantage.

"I think Magnum is doing a smart thing by initially building a gas storage reservoir that might also be used in the future as a compressed air reservoir, depending on how the demand for the various services changes over time," says Makhijani. "The reservoir is going to be there for them."

Here in the desert, north of Milford, most of this energy that blows from the west and shines from the sky, for now, remains untapped.

[Music: Boards of Canada, Dayvan Cowboy]


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