Eolos, a research wind turbine at the University of Minnesota’s UMore Park in Rosemount, provides power that the U sells to Xcel. (Dml - Star Tribune/The Minnesota Star Tribune)

Xcel Energy Inc., the nation's No. 1 wind-power utility, said Tuesday it set a record for wind generation in the Upper Midwest.

The utility said regional wind farms generated a record 1,713 megawatts from 7 to 8 p.m. on Feb. 17, representing nearly 33 percent of demand at the time. Xcel serves 1.7 million electric customers in five Midwestern states.

The output is just short of the Minneapolis-based utility's total wind-generation capacity in Minnesota. It follows the addition of 267 megawatts of wind-power capacity last year in the state.

Winds were exceptional on the day the record was set and also on the next day, boosting the output at the utility's owned and contracted wind farms, said Laura McCarten, a regional vice president for Xcel.

"This system was causing the wind to blow hard across the whole front," McCarten said. "We had pretty sustained wind starting at 4 p.m. that day.''

It was not the highest percentage of wind power that Xcel has ever hit. Xcel said that happened on Nov. 23, when wind supplied nearly 40 percent of its Midwest customers' needs — but at a time of lower overall demand. Wind has briefly supplied as much as 55 percent of power for Xcel's Colorado operations.

Grid rules favor wind

Under the rules of the electrical grid, when the breeze is blowing, wind turbines' output gets priority over other generators, as long as there is enough transmission capacity to carry it. That's because wind power carries no extra fuel costs like coal- or natural gas-fired plants.

As wind output increases, the utility reduces output of its giant Sherburne County coal-burning units and dials back or turns off units that burn natural gas, such as the Riverside and High Bridge stations in the Twin Cities.

"We have learned a lot about how to successfully produce and integrate wind energy onto our system in a cost-effective manner for our customers," Judy Poferl, CEO for Xcel's Minnesota regional division, said in a statement.

Chris Franks, a meteorologist at the National Weather Service in Chanhassen, said sustained wind speeds ranged from 17 miles per hour to 23 mph during the period of the record, and steady winds continued across most of the state on the next day.

"It was breezy the whole day," said Franks, who suspects the wind hit a "sweet spot" for power generation over a broad area.

Considering new mandate

Xcel produced nearly 12 percent of its Upper Midwest electricity from wind farms last year, the company said. Its Midwest territory includes parts of Minnesota, North Dakota, South Dakota, Wisconsin and Michigan. The company also has operations in Colorado, New Mexico and Texas.

Xcel said it is on track to generate 30 percent of its energy from renewable sources by 2020, with 25 percent from wind, under the state's renewable energy standards. Wind power advocates have proposed a measure in the state Legislature upping the wind mandate to 40 percent by 2030.

McCarten said the utility doesn't agree that a new mandate would be "a good policy for the state." Even so, the company is considering adding wind farms in the region. Last month, it asked wind developers to submit proposals for up to 200 megawatts of Midwest wind resources, hoping to benefit from the extended federal Wind Production Tax Credit.

Beth Soholt, director of Wind on the Wires, a St. Paul-based wind industry group that supports the 40 percent wind mandate, said Xcel's Feb. 17 wind experience illustrates how well the utility and grid operators can integrate intermittent renewable power with other generation sources.

"This is proof positive of that," she said. "It's about having a lot of flexibility in the system, lots of transmission to move things around."
David Shaffer • 612-673-7090 • @ShafferStrib