In Granite Falls, plans to harness 'quiet renewable'by Mark Steil, Minnesota Public Radio
Granite Falls, Minn. — In the southwest Minnesota town of Granite Falls, plans are underway to use an old power source, water, to solve the problem of the ever-increasing demands for electricity.
One of the most difficult and expensive problems electric utilities face is the lack of a way to store large amounts of power. An efficient electricity storage system would reduce the need for new generating plants.
On the hottest day of the summer, with thousands of air conditioners operating, the power grid needs every pulse of electricity it can find to meet demand.
To keep everyone cool, the grid harnesses electricity from a wide variety of sources, including coal, nuclear and natural gas plants. It also taps renewable sources like wind, solar and one of the oldest power sources known, water.
"Hydroelectric is the quiet renewable," says Doug Spaulding. "It doesn't get a lot of press or anything, but it has a lot of potential."
Spaulding is President of Twin Cities based Nelson Energy. His company has several water projects in the works. One of them, in southwest Minnesota is a large-scale power storage facility that relies on water.
"The Granite Falls project is in the development stage," says Spaulding. "It is a thousand megawatts pumped storage project."
A typical pumped storage system has two reservoirs, at greatly different elevations. When electricity is in high demand, water is released from the upper basin to the lower reservoir, spinning turbines and generating electricity as it runs.
Later, when demand has receded, electric pumps send the water from the lower basin back to the upper reservoir.
The economics work, because the plant can sell electricity generated at peak times for more than it costs to pump the water back up during off-peak hours.
The first U.S. pumped storage systems were built around 1930. The most recent went on-line in Georgia about 15 years ago. Spaulding says it's time to revisit the technology.
"Pumped storage is the only technology available to store large quantities of electrical energy," says Spaulding.
The system doesn't literally store an electric charge like a battery. It uses a combination of water and gravity to capture energy that can be used to generate electricity.
Spaulding says the upper reservoir at Granite Falls would be on farmland. The lower unit would be bored into bedrock a couple of thousand feet down. He says the concept is especially useful now because of the large amounts of wind energy being produced.
Unlike other forms of electricity, there's very little human control over when wind turbines produce electricity; it happens when the wind blows.
As a practical matter, that often means the highest output is when the electricity is needed the least. Spaulding says the Granite Falls system could capture that wind energy and release it during peak demand periods.
"The energy that comes to pump the water up the hill, or so to speak, would come from off-peak resources such as wind," says Spaulding.
Spaulding says it will take at least four years to get the necessary permits for the project and that the soonest the project could be on-line would be 2018.
Environmental groups are studying the project, but so far no one has formally objected to the concept. One concern is whether drawing water from the Minnesota River to fill the project's reservoirs will damage the river.
The Granite Falls idea is one of several energy storage proposals in the works. Xcel Energy is using a large battery to store wind energy in southwest Minnesota. And in central Iowa, a group of utility companies plan to build what's called a compressed air energy storage system.
Central Minnesota Municipal Power Agency is one of the companies involved in the Iowa project. The company's deputy CEO Steve Thompson says the project plans to use wind energy to pump compressed air into deep underground caverns.
"The basic concept of compressed air energy storage is that you compress air off-peak and use to generate power on-peak," says Thompson.
When it's released the compressed air flows through turbines to generate electricity. Like the water storage project near Granite Falls, the Iowa facility is years away from operation. In the meantime, with more wind turbines constructed every year, the need for a workable way to store electricity will continue to grow.
- Morning Edition, 05/18/2010, 7:40 a.m.