KALISPELL - As the breeze picked up on May 12, the region's wind turbines began spinning faster, generating far more power than expected.
The grid was going into overload, and hydroelectric dam operators scrambled to dial back their flows, making way for the wind-driven electricity.
But they could only pull back so far and so fast without jeopardizing the grid's stability. Normally, when the winds came on so hard and so unexpectedly, there was only one option - unplug the wind farm.
But on May 12, for the first time, something else happened. The wind-power producers started making short-term sales, spreading their extra juice out to customers far and wide, capturing every megawatt the big blow could provide.
It signaled a major shift in the way power is delivered in the Pacific Northwest, and served as proof of the faster and more flexible system that is evolving to accommodate today's renewable energy sources.
"We're getting better all the time, so we can handle more renewables," said Michael Milstein, spokesman at Bonneville Power Administration. "The system is changing in some pretty fundamental ways."
Bonneville is the quasi-governmental outfit that markets power generated at the region's many hydroelectric dams, and provides much of the electricity used in Montana. It also buys power for redistribution from other sources, including wind farms.
Traditionally, Milstein said, "the Bonneville grid was very stable," with only a few coal and gas and nuclear generators to keep track of. "It was very consistent," he said. "All we really had to keep track of was demand."
And demand - like that traditional supply - was pretty predictable, with people waking up at the same time, turning on lights, leaving for work, lighting the house back up for evening.
"But when wind entered, and became a bigger part of the system, it created all these fluctuations," Milstein said. Sometimes it blew hard, sometimes not at all, and sometimes it changed quickly and unexpectedly. With 27 wind projects online, the ups and downs were wrecking havoc with the old system.
Bonneville's power managers responded by ramping hydro up and down to meet wind's supply changes, but often they were forced to ask wind producers to unplug when the gusts really blew.
Where once they assessed supply day to day, now they reviewed supply hour to hour. "And now," Milstein said, "we're watching it much more on a minute-by-minute basis."
The need to react quickly in the short term drove a new BPA policy, initiated in December, that allows power sales every half-hour - and that's the policy that kept the wind turbines spinning on May 12.
Now, he said, if a wind farm makes a power sale and then the wind increases unexpectedly, the producer can make another sale every 30 minutes, pushing more power to distant markets. Monitoring all these sales means more work, and more staff to oversee the supply and demand balance, but "it seems like it's really working. It's been worth it, because it means we can react faster and with more flexibility to the realities of these renewable sources."
In addition, Milstein said, the quicker sales help take pressure off BPA's hydro system, which no longer has to be the only part of the system that flexes in the changing winds.
"It really is a whole new business," he said, "as we work out how to integrate the renewables."
And it's bound to change even more, as demand - the other side of the equation - also continues to evolve. Already, some homes are equipped with special electric meters that tell consumers when the grid is busiest, and the power most expensive. Such systems allow people to save money by choosing to do laundry or run dishwashers when power is cheapest.
That, of course, creates the same sort of variability in a previously predictable system as does wind on the supply side, forcing the entire grid to become more reactive. Each step, Milstein said, brings supply and demand closer and closer to a real-time flexibility.
By selling an unexpected 330 megawatts of wind power on the short-term market, rather than unplugging the turbines on May 12, the wind farms made extra revenue and the hydro plants didn't have to strain the grid. At one point, in April, these new short-term sales put 4,424 megawatt half-hours on the system, the equivalent of about four nuclear power plants.
The May 12 event, Milstein said, was the first time the new program actually prevented wind turbine shutdowns, but it surely won't be the last.
"The grid is changing," he said. "The entire energy delivery system is changing, right before our eyes."
Missoulian reporter Michael Jamison can be reached at (406) 862-8324 or email@example.com.