Unlike Texas wind turbines that slowed or shut down during the recent winter storm, Iowa’s kept turning.
The main differences?
Texas was hit with ice, whereas Iowa has had extreme cold and snow. And because Iowa’s turbines are installed with heating elements to keep fuel and electrical controls warm, they can operate in temperatures of up to 20 below zero.
“We can get a foot of snow and the turbines continue to run right through that,” said Tony Vaughn, senior operations manager for Alliant Energy, which has about 650 turbines in Iowa. “But you get that mist and sleet, ice can build up. That’ll slow down the RPMs of the blade and it will reduce the output to a point where it will eventually come offline and not produce anything until ice starts to shed off the blades.”
That’s what happened in Texas this week as temperatures in the 20s and 30s caused sleet to freeze on the carbon fiber blades of wind turbines, reducing output and contributing to widespread power outages across the state.
Although Texas has been increasing its use of wind turbines, most of the state’s power comes from natural gas, coal and nuclear energy, the Associated Press reported.
About 25 percent of Texas’ electricity comes from wind energy. In contrast, Iowa is No. 1 in the nation for its share of electricity coming from wind at about 40 percent.
Because subzero temperatures are normal in Iowa winters, companies that develop wind farms here buy turbines equipped with a cold-weather package that include heaters near the gear box, generators and other components in the cell, which is the big box behind the turbine blades and attached to the tower.
“When we design a wind farm and order the equipment, we want to make sure it’s producing energy year-round no matter the weather conditions,” said Geoff Greenwood, a spokeswoman for MidAmerican Energy, which has more than 3,300 wind turbines in Iowa.
Even at the coldest point of this recent cold snap, temperatures in Iowa never got to 22 degrees below zero, which is where turbines start shutting down to protect themselves from damage.
“Our wind turbines have been running even in this extreme cold,” Greenwood said. And since November through April is peak season for harvesting wind energy in Iowa, companies like MidAmerican and Alliant want to minimize time when the wind is blowing but turbine blades aren’t running.
Ice is another matter.
Because there are few effective ways to keep ice from forming on turbine blades, wind farm operators have to decide whether to power down in anticipation of an ice storm. Doing so reduces ice accumulation on the blades and can shorten the thaw afterward, Vaughn said.
“The downside, you may have to turn them off for a whole 24-hour period and maybe the temperatures never fall low enough and you’ve lost out on 24 hours of time to produce power,” he said.
Although some comparisons are made between de-icing airplane wings and wind turbine blades, the systems are quite different, said Hui Hu, an aerospace engineering professor at Iowa State University.
Aircraft fly through clouds of very small droplets of water, while turbines spin close to the ground where droplets are larger, Hu said. Aircraft wings are metal, which conducts heat better than the polymers of turbine blades.
“Many heating mechanisms that work perfectly for aircraft may not be the best solutions” for wind turbines, Hu said.
More promising is a combination of low heat in certain parts of the turbine blade combined with a coating on the blade that would discourage ice adhesion and strength, according to new research from Hu and his research team.
The Iowa Economic Development Authority in 2019 awarded Hu’s team a $300,000 research grant to further develop these ideas.
It’s part of a long-term state investment in the wind industry, said Brian Selinger, team leader of the Iowa Energy Office within the authority.
“Wind energy has been extremely good to Iowa and to Iowa’s economy,” he said. Iowa’s wind industry employs nearly 10,000 people and has created billions of dollars in capital investments, he said.
“We have vast amounts of wind rippling across our fields,” Selinger said. “To be able to harness that for economic benefits, it checks all the boxes for economic development.”
|Wind Watch relies entirely
on User Funding