The Sherco coal plant near Becker, Minnesota. (Photo via Minnesota Pollution Control Agency)
The Sherco coal plant near Becker, Minnesota. (Photo via Minnesota Pollution Control Agency)
The Sherco coal plant near Becker, Minnesota. (Photo via Minnesota Pollution Control Agency)

©2013 E&E Publishing, LLC
Republished with permission

By Daniel Cusick

One of the Midwest’s largest coal-fired electric generation units is set to restart this week after a nearly two-year shutdown that required the unit to be rebuilt from the ground up.

Xcel Energy Inc.’s Sherburne County Unit 3 generator, a 900-megawatt behemoth that provides baseload power to the Minneapolis-St. Paul region and points beyond, is expected to begin sending power to the grid after several days of testing, according to officials with the Minneapolis-based utility, which has a 59 percent ownership stake in the coal unit.

The “Sherco” Unit 3 was severely damaged in November 2011 during the testing of safety equipment intended to automatically slow the steam turbine if it began spinning too fast. The test, which briefly pushed the turbine’s rotors to more than 3,600 rounds per minute, led to a catastrophic failure marked by severe vibration and turbine blades coming loose from their mounts, sending metal shards through the 80-ton rotor, destroying it. The crisis worsened when hot oil and other flammable liquids caught fire, filling portions of the plant with smoke.

Almost two years and more than $200 million later, Xcel is ready to return the unit to service. A series of test starts was to begin yesterday, to be followed by full power by the end of the week. Once at full power, Sherburne’s Unit 3, combined with two 750-megawatt coal burners, known as Units 1 and 2, should be able to produce 2,400 megawatts of electricity, according to Xcel.

The refired Unit 3 generator will also help burnish Sherco’s reputation as Minnesota’s largest point-source emitter of carbon dioxide, the primary greenhouse gas that scientists have linked to global climate change.

Environmental groups have made Sherco a centerpiece of ongoing efforts to reduce utility-sector carbon emissions in Minnesota. Last year, a coalition of nonprofit groups sued U.S. EPA in hopes of getting tougher emissions standards placed on Sherco’s Units 1 and 2, which were constructed in the 1970s.

Unit 3 has received less attention from environmentalists, in part because it was idled for two years, and also because the unit is already equipped with advanced pollution controls for sulfur dioxide (SO2), nitrogen oxides (NOx), particulate matter and mercury. Unit 3, like the two older units, also burns lower-sulfur Western coal that helps to reduce some of its air quality impacts.

Earlier this year, Xcel filed a “life cycle management study” with Minnesota regulators examining alternatives to continuing to operate Sherco Units 1 and 2. The study included risk-benefit analyses for converting the units to natural gas at a cost of $1.7 billion or retiring them altogether. Ultimately, Xcel decided that neither alternative option made economic sense in the near term and decided it would continue to operate Sherco’s two older units under current scenarios.

Awaiting regulatory developments

“The company believes the most prudent course of action at this time is to continue to operate Sherco 1 and 2 as we await greater clarity and certainty around the development of environmental regulation and the resulting timing and costs,” Xcel said in its report.

But Michelle Hesterberg, a federal field organizer with the nonprofit group Environment Minnesota, said Xcel’s commitment to burn coal at Sherco reflects a bottom-line reluctance to adapt to a new energy economy powered by natural gas, renewable resources like wind and solar power, energy efficiency and demand-side reduction efforts that curtail electricity use.

Environmental groups also say that utilities like Xcel should begin taking steps to wean themselves from coal before U.S. EPA begins drafting what many believe will be new rules governing CO2 emissions from existing power plants like Sherco. Such rules are expected by next June, following the agency’s recent rollout of a rule limiting CO2 from new power plants.

“Xcel Energy’s plan does not keep our state moving forward, and it’s not smart policy,” Hesterberg said. Continuing to operate all three of Sherco’s coal units without addressing the plant’s CO2 emissions “does not bode well for a long-term vision of getting us off of carbon-intense fuels,” she added.

Frank Prager, Xcel Energy’s vice president for environmental and public policy, said in an emailed statement that the company is being proactive about reducing its carbon footprint, noting that annual CO2 emissions have dropped 18 percent from 2005 levels. And the utility remains committed to meeting a 31 percent reduction target by 2020, he said.

With respect to pending carbon regulations for existing power plants, Prager said, “we expect EPA to allow the states significant flexibility to meet reduction goals through a variety of clean energy actions, such as renewables, efficiency programs and coal plant upgrade initiatives. This flexibility will allow Xcel Energy to continue to reduce emissions and implement clean energy while keeping a significant role for coal in a balanced, diverse energy portfolio.”

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