NorthWestern Energy’s energy portfolio that serves Montana customers includes 450 megawatts of wind energy, a piece of the diverse 67% carbon-free energy mix.
Wind is a good clean energy resource, the company said in a news release, but it is not a capacity resource available 24/7. Because it is a variable resource, it creates unique challenges to operating the energy grid reliably.
The windstorm that ripped across Montana on Jan. 13 is an example of that challenge. Gusts ranged from about 65 miles per hour to more than 90 miles per hour across the state.
Wind turbines shut down, an industry term called “high-speed wind cut-out,” when wind gusts have the potential to damage equipment. Although it varies by turbine, generally the cut-out speed is 55 miles per hour, according the U.S. Department of Energy.
In Montana, when wind was averaging about 33 miles per hour at 4 p.m., Tuesday, Jan. 12, NorthWestern Energy’s wind generation was producing about 430 megawatts, close to its maximum capability.
When wind speeds accelerated to 70 miles per hour and higher by mid-morning Jan. 13, in Montana, wind turbines’ automated “high-speed wind cut-out” technology had shut many of them down. Wind generation bounced every 15 minutes, from about 280 megawatts to less than 30 megawatts when the wind howled across the state.
“There is always the potential to be 450 megawatts long or 450 megawatts short when it comes to meeting our customers’ demand with the wind resources in our Montana portfolio,” NorthWestern Energy Vice President Supply/Montana Government Relations John Hines said. “The result is higher costs, lower reliability and grid instability for our customers.”
Wind is not a reliable energy source required to meet customer needs during times of critical energy demand, cold winter nights and hot summer days.
It creates another challenge.
NorthWestern Energy is the Balancing Authority for the Bulk Electric System and interconnected grid in Montana, responsible for balancing megawatts being put on the grid by generation sources with the megawatts being taken off the grid to serve customers. That balance is critical for the reliable operation of the grid.
Variable energy resources – wind and solar – mean there is a critical requirement for flexible capacity resources that are available on demand – such as hydro, storage, natural gas generation, etc. – to keep the grid balanced and operating reliably 24/7.
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