What goes up must come down. Water, coming down, can generate electricity. That’s why there are several projects underway to pump water up so it can come back down again.
Such a system is called pumped storage. It lets a reservoir act like a giant battery and helps deal with the issue of excess energy produced by wind and solar energy systems.
In closed pumped storage, there are two reservoirs and water circulates between them. An open pumped storage system draws water from a free-flowing source such as a river or a lake. But either way, a pumped storage system involves pumping water up when there is excess energy, and letting it fall back down again, generating energy when it is needed.
Typically water goes up and down through a pipe or tunnel, with one unit that acts both as a pump to push the water up, and a generator that produces power when the water is coming down, said Frank Gariglio, engineering leader for Idaho Power. Such systems are typically 75% to 80% efficient, which isn’t terrible, he said.
About 40 pumped storage projects were built in the U.S. between the 1950s and the 1990s, typically partnered with nuclear power systems, said Matthew Shapiro, CEO for Boise-based Gridflex Energy, which operates seven pumped storage projects in California, Kentucky, Nevada, Utah, Washington and Wyoming.
The last major pumped storage project went online in 1993, and since then only one has been built.
Interest in pumped storage decreased when natural gas supplanted nuclear energy, Shapiro said, but there’s been a revival with the advent of renewable energy. While battery technology is improving and the cost is coming down, batteries last only five to 10 years, while a pumped storage plant can last from 80 to 100 years, he said.
Currently, Idaho doesn’t have any licensed or pending pumped storage projects, according to the Federal Energy Regulatory Commission (FERC), which governs their licensure. However, preliminary permits have been granted to two: One to Idaho Power at the Hells Canyon Complex, and one to Coleman Hydro for a project near Leadore, east of the Salmon-Challis National Forest.
So far, the capital cost of constructing such projects has kept them out of the Idaho Power portfolio, said Kresta Davis-Butts, senior manager of resource planning and operations hydrology. According to the company’s most recent portfolio update, released July 1, the cost is projected to be $1,900 per kilowatt-hour in 2023.
In addition to the Hells Creek Complex, the Anderson Ranch Reservoir area has also been looked at as a potential pumped storage site, including by Gridflex. The advantage of the Anderson Ranch area is its geography, Shapiro said.
“Here you have a large reservoir that is near some transmission,” he said. “If you have the right topography, it can be an appealing place to do pumped storage.”
The company had looked at a $200 million project that would have generated 80 megawatts (MW) of power, which is on the small side for such projects, Shapiro said. In comparison, the largest pumped storage site in Virginia generates 3,000 MW.
While the Anderson Ranch project didn’t pan out, Shapiro said he is still looking at Idaho pumped storage projects, though he didn’t want to provide specifics. His company started a partnership this year with the funding source rPlus Energies, a subsidiary of the Gardner Co.
Another company looking at Anderson Ranch is Cat Creek Energy, based in Gooding. In addition to 720 MW of power from pumped storage, the project also includes 40 MW of solar and 110 MW of wind power, said John Faulkner, president.
While FERC granted Cat Creek a successive preliminary permit on April 18, after its original November 2015 permit, the project has raised opposition from neighbors, primarily due to the environmental impacts of the wind storage component.