While hundreds of towering wind turbines now dot hillsides across Central Washington, engineers have yet to solve the vexing problem of matching production to demand.
With hydropower – long the Northwest’s biggest source of electricity – most water is stored behind dams and released when needed to meet power demand. There’s no such option with turbines, which spin when the wind blows and stand idle in calm weather, indifferent to demand.
Further complicating the picture is that both water and wind reach their peaks in the spring, when demand for power is low.
But now a rock formation thousands of feet below the Yakima River Canyon could hold a key to solving the problem.
Research from the Bonneville Power Administration and the Pacific Northwest National Laboratory shows excess electricity from wind turbines could be used to compress air. In turn, the compressed air would be stored deep in a formation of porous rock below a layer of impermeable basalt that would act like a reservoir. When wanted, the air would be released to spin turbines to make electricity.
The air compression technology can re-create up to 80 percent of energy put in, according to the research, and it can quickly shift from energy storage to electrical generation to meet the needs of the grid.
If built – and there are plenty of ifs – it would be only the third such plant in the world. One is in Germany; the other has been operating in Alabama since 1991. It stores excess energy produced at a natural gas power plant at night for use later during peak demand, with enough capacity for 110,000 homes.
The Alabama plant uses underground salt cavern formations to hold the air, but the BPA and PNNL researchers wanted to see if the technology could work with the geology of Eastern Washington. They started their research looking for suitable sites and settled on two: the Yakima Minerals property about 10 miles north of Selah, and a site along the Columbia River just north of Boardman, Ore.
According to Pete McGrail, a PNNL researcher and the lead author of the study, the Yakima Canyon site is ideal because of the rock formation’s sheer size.
“The structure is so big that we ran the model for injecting air for a whole year and we didn’t even fill up 20 percent,” McGrail said.
There’s another advantage to the Yakima site. Before compressed air can be used to spin turbines, it must be heated up, typically with natural gas. But the Yakima site could draw on 365-degree geothermal water located about 14,000 feet underground.
The downside, BPA’s Steve Knudsen said, is that the up-front cost of construction is more expensive than the natural gas option. The report estimates that building the facility would cost about $225 million. Most of the project’s expense would be the geothermal power plant, not the storage system itself, Knudsen added.
Once up and running, a plant like this would probably employ 15 to 30 people, Knudsen said.
Now that the study shows that the technology could work, BPA is planning a more in-depth cost and benefit analysis, which would be needed to determine if the project is viable. If so, several years of engineering and permitting work would be required before the project could move forward.
If Washington’s renewable energy portfolio continues to grow, investment in this type of technology would become more valuable, Knudsen explained.
The only other large-scale energy storage option is pumping water up into reservoirs to use later for hydroelectric power. The advantages of storing air instead of water is that it’s cheaper, has a much smaller environmental footprint and should be much faster to permit, Knudsen said. Per megawatt-hour of energy storage, the compressed air option could cost less than 10 percent of what pumping water into a reservoir would cost.
McGrail said he’s cautiously optimistic that the technology will eventually be put to use in the region.
“This is an option that looks economically attractive and can be done in a relatively short period of time to address the problem Bonneville is facing in managing the electric grid,” McGrail said.
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