"The way we look at it is that we avoided the build-out of a new coal-based generation unit," says Minnesota Power's Pat Mullen. "We're able to build more wind in a very high value resource area and transmit it to where we need a resource like that. We don't have that sort of wind capacity in the region in which we live."
The 500 kV line begins at the Milton R Young Generating Station in Center, North Dakota, a coal plant, and ends at Minnesota Power's Hermantown substation near Duluth. Much of the power now carried by the line is then routed back towards North Dakota on traditional alternating current (AC) lines. The DC line, which has no off-take points, is currently owned by Square Butte Electric Cooperative and will be sold to Minnesota Power early next year for $80 million. "The DC line is a very efficient point-to-point delivery system," Mullen says. "But there's a lot of expensive equipment on both ends of the line to convert to and from AC."
Using the coal line
Electricity from the Young station is equally shared between Minnesota Power and Square Butte's affiliate, Minnkota Power Cooperative. Minnesota Power will gradually reduce its generation rights from the Young plant in favour of wind between 2013 and 2025. At the same time, Minnkota will take its coal generated energy off the line in stages and put it on an AC system, which will allow Minnesota Power to begin adding its new wind power to the DC line. The two companies maintain a partnership going back to 1977 and settled on the plan in an effort to avoid building a new coal plant.
"We had been in an exploratory phase some time ago," Mullen says. "The biggest point is the strategic nature of this thing and how it has played out for both companies. We each had different needs and Minnkota already has some wind in their mix."
The 400-600 MW of new wind power is in the early planning stages with no turbines yet secured, Mullen says. But Minnesota Power has some experience developing, owning and operating wind plant. The company's 25 MW Taconite Ridge project, overlooking the mining town of Virginia, Minnesota, dedicated ten Clipper 2.5 MW turbines last month.
Minnesota Power also buys wind power from two 50 MW North Dakota projects owned by FPL Energy, Oliver I and II. It expects to sign on for an additional 32.5 MW when the Bear Creek project in west-central Minnesota brings its 2.5 MW Nordex turbines online later this year. While Minnesota Power currently gets nearly 11% of its electricity from renewable sources, the state's renewable energy mandate law requires 25% by 2025.
"Renewable energy overall is something we've been working on," Mullen says. "And we have some of the largest hydro stations in Minnesota. But, clearly, wind will be the leading component of our renewables portfolio."
Minnesota Power, a subsidiary of Duluth-based Allette, supplies electricity to 141,000 retail customers, along with some of the largest industrial customers in the US. Minnkota, based in Grand Forks, North Dakota, supplies wholesale electricity to 11 cooperatives in eastern North Dakota and north-western Minnesota. Square Butte Electric owns the Young station and is operated by the same cooperatives that control Minnkota.