Pushing wind power from night to day via compressed air
Posted on February 12th, 2009By Jessica Leber
Climatewire: Wind power has a dark side: Much of it is produced at night, just when the demand for electricity is lowest. Now, the breezes of change are blowing for a decades-old concept that could store nighttime energy and help solve this supply-and-demand disconnect.
The idea is simple. At night, use cheap energy to compress air, and during the day, when energy demand peaks, release that pent-up air to power a turbine.
No one knows more about compressed-air energy storage, or CAES, than Michael Nakhamkin, an engineer who has worked on the concept for more than two decades. He led the design of the second power plant ever built that uses the technology, a 110-megawatt Alabama facility that has, since 1991, stored energy produced by coal-fired power.
Fast-forward 17 years. The Alabama plant is still running, but no others have followed suit. “Natural gas and coal used to be cheap,” said Nakhamkin. “There was no huge motivation to store energy.”
But times are changing fast, as fossil fuel prices seesaw and more wind power makes its way onto the electric grid.
In August, Nakhamkin formed a joint venture with New Jersey-based PSEG Global LLC to develop the “second generation” of the technology, which he says could be deployed at a wider range of scales and could run more efficiently.
2 new demonstration plants and more to come
The venture, Energy Storage and Power LLC, is working to build two demonstration projects — one small plant that will store the compressed air above ground and another 300-megawatt plant that will pump the air into an underground reservoir such as a salt cavern or an aquifer — a common way to store natural gas today.
“Everything’s been proven,” said Roy Daniel, who came from PSEG to be CEO of the new venture.
Batteries and flywheels, which are other storage technologies often discussed, are not yet capable of economically storing the sheer bulk of energy needed to bring wind energy over the night-to-day hump, according to Richard Lordan, a technology director at the Electric Power Research Institute, a nonprofit that is exploring possibilities of working with Nakhamkin on the projects.
Pumping water uphill is the only other way to store energy at a similar scale, but those projects can take 10 years to build and are limited geographically. Air, however, can be stored in underground caverns throughout 80 percent of the nation, said Nakhamkin. The technology means that he can use the same amount of fuel to produce about three times as much energy as a traditional turbine.
But for PSEG, which so far has invested $20 million in the venture, the greatest benefits are in the economics.
“The key is the difference in what you pay for power while you’re compressing the air and what you’re paying when you discharge,” said Ralph Izzo, chairman, president and CEO of PSEG Inc., which through its subsidiary owns PSEG Global and also owns New Jersey’s largest electric and gas utility.
“That’s what makes it so attractive for wind,” he said. PSEG, he said, is interested in exploring above- and below-ground CAES projects in New York, New Jersey and Texas.
Saving dirt-cheap power at night and getting premium daytime prices
Texas, the nation’s wind leader among states, is already running up against storage barriers: Sometimes, wind farms are producing so much excess energy that the price of their electricity falls into the negative column.
But with compressed-air energy storage, Izzo said, a wind developer could instead always sell electricity during the day, when prices are highest. That means a project may not need to lean as heavily on incentives like renewable energy credits (RECs) to be competitive in the market.
“A REC, while important and justified, is essentially a subsidy,” said Izzo. Although utilities producing wind energy won’t necessarily need storage technologies to meet many state renewable mandates, he said, they will need such technologies to do so economically.
Lordan, of the Electric Power Research Institute, said other CAES projects may be popping up soon.
One is in the planning stages in Ohio, and yesterday, a Colorado-based company announced it would be attempting to deploy air energy storage in its North Dakota salt mine, according to the Associated Press. North and South Dakota, like Texas, are states ripe for energy storage, with a lot of wind and not a lot of people.
But Izzo said the technology’s potenial isn’t limited to resource-rich states. That’s especially true because a storage facility doesn’t have to be located anywhere near a wind farm.
New Jersey, where Izzo’s company is developing solar and offshore wind projects, is a prime example of making do with what you’ve got. “If you look on the maps, it’s in the don’t-even-think-about-it category,” he said.