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Breakdowns, shutdowns and cost overruns plague Xcel’s Comanche 3 coal-fired power plant, investigation finds

Electricity from the state-of-the-art coal-fired power plant near Pueblo costs 45% more than forecast, Colorado Public Utilities Commission reports. Xcel says Comanche will be used as a backup to renewable generation after 2030.

Xcel Energy's $1.3-billion 750-megawatt Comanche 3 coal-fired unit, shown here in a Jan. 26, 2020, photo, went into operation in 2010. It's the state's largest coal-burning power plant. (Mike Sweeney, Special to The Colorado Sun)
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Comanche 3, Xcel Energy’s state-of-the-art coal-fired power plant, has been plagued by operational, equipment and financial problems leading to more than 700 days of unplanned shutdowns since the plant went online in 2010, according to a report by the Colorado Public Utilities Commission.

The report by the PUC staff found that the cost of electricity from the plant — $66.25 for each megawatt-hour (MWh) – was 45% more than forecast and the annual operating costs were 44% higher than projected at $34.8 million a year.

The PUC undertook the assessment after two mechanical failures led to the unit being closed for all of 2020 and parts of 2021 – a total of 373 days.

“What we are doing is a bit of public and private review of the utility’s performance,” former PUC Chairman Jeffrey Ackermann said in approving the study in October.

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“We are closely reviewing the Colorado Public Utilities Commission’s report on Comanche Unit 3 in Pueblo. Meanwhile, we are committed to the continued safe and reliable operation of the plant through its proposed early retirement in 2040,” Xcel said in a statement.

The utility — Colorado’s largest electricity provider with 1.5 million customers — said it continues to look for new ways to learn and improve the way it runs its generation fleet.

The first incident started on Jan. 13, 2020 when a loud noise and vibrations began to come from a low-pressure turbine. The plant was down until June 2 for repairs, costing $4.2 million, and inspections.

When the unit was started up again there was a failure in a six-way valve that led to a loss of lubricating oil used to keep elements of the turbine from overheating. It is considered a “system critical to the operation and well-being of the turbine,” the report said.

The report said that the design of the valve, maintenance and inadequate communication between the control room and operations staff all played a role in the failure.

“The company acknowledged that the six-way transfer valve was never dismantled and inspected since the plant went commercial in 2010,” the report said, nor can it get a replacement valve since it is obsolete.

“The company knows it cannot get replacement parts,” the report said. “The company has no policy with regard to the use of obsolete equipment in the power plant.”

The cost of the June incident was $20.4 million and Xcel had to buy $14.4 million in replacement power, though subtracting the amount it would have cost to run Comanche 3 it brought the cost of the power purchases down to $9.5 million.

“During September and December of 2020, having Comanche 3 offline actually saved customers money,” the PUC report said, raising the prospect of using the unit for “month- or season-specific operations.”

Xcel said in the statement that after 2030 it is proposing to run Comanche 3 at a significantly reduced capacity as a backup to renewable energy generation that is not enough to meet demand and noted that the plant performed well during the recent arctic cold snap.

The 2020 failures at the $1.3 billion plant, one of the last coal-fired power plants built in the West, were only the latest and most dramatic in a long litany of problems since the unit went into service May 14, 2010 – about six months behind schedule.

Comanche 3 boasts advanced supercritical pulverized coal technology and top-of-the line pollution controls.

Nevertheless, the PUC report outlines several dozen unplanned outages over the life of the plant adding up to more than 335 days of unplanned shutdowns between 2012 and 2019.

In part because of the generating problems, the cost of Comanche 3 electricity has been relatively expensive. It costs Comanche 3 $66.25 to generate each MWh. The average cost of wind projects bid in Xcel’s 2017 solicitation was $19.30 a MWh.

“Even on a good day, Comanche 3 is more expensive than renewable energy,” Anna McDevitt, senior campaign representative for the Sierra Club’s Beyond Coal campaign, said in a statement. “I hope this is the last time that Xcel Energy wastes millions of customer dollars to fix outdated coal-energy technology.”

Xcel said that it will close Comanche 3 in 2040 – about 30 years earlier than initially planned – as part of its Clean Energy Plan, which is aimed at producing zero-carbon electricity by 2050.

Because of its early retirement, Xcel will likely seek to have customers pay off the unamortized portion of the plant

Xcel’s investment in the plant, which is shared with Intermountain Rural Electric Association and Holy Cross Energy, was $885 million in 2010. This amount is paid off over time through rates paid by customers. The report said that assuming historic trends, there will still be $460 million left in base rates in 2030, and $320 million in 2040 to be recovered.

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