Princeton Public Utilities’ five diesel generators played a critical role in providing backup electrical power during last week’s record-setting cold.

The Southern Minnesota Municipal Power Agency contacted the local utility late Tuesday with a dispatch call, said general manager Connie Wangen.

“SMMPA asked for us to get our biggest generator, our Caterpillar diesel, online by 4:15 a.m. last Wednesday and our other units by 5:15 a.m. We ran about 30 hours, producing electricity to the grid,” Wangen said.

The 18-member municipal utilities’ local generation units played an important role in keeping the lights on during the recent cold weather brought on by the polar vortex.

With natural gas in short supply in certain areas of the state, diesel or dual-fuel units operated nearly nonstop beginning early Wednesday morning.

“These are smaller units that generally don’t run that often, but when they do, they play an important role in contributing to both local and regional electric reliability,” said David Geschwind, SMMPA executive director and CEO. “Our member utilities and employees are to be commended for being able to quickly respond to the need and working long hours to operate these units in adverse conditions.”

SMMPA responded to a request from the electric grid operator, the Midcontinent Independent System Operator, to generate electricity, since many power plants that use natural gas to produce electricity were unable to operate due to natural gas curtailments because of the high demand for natural gas for heating.

Collectively, SMMPA members ran 43 local generators on diesel fuel to help keep the electric grid operating reliably.

It’s more common for the generating units at SMMPA members’ power plants to be called upon on the hottest of days in the summer, but clearly they are as valuable in the coldest days of winter, Geschwind stated in a news release.

“In either condition, human health can be at risk, so the professionalism of those power plant operators in a time of need is very much appreciated,” he said.

Wangen said initially she didn’t know at the start of the dispatch period that Princeton Public Utilities would have to run its generators so long.

“At first, we were only scheduled to run five or six hours, which would have been until about 10 a.m. Wednesday morning, but then we received orders to run until 9 p.m. Then, around 5 p.m. to 6 p.m. we were asked to run all evening, and shut down at 9 a.m. the following morning [Thursday]. We were asked to staff our generating units until 9 p.m. Thursday night, but then we received a final order informing us we could shut down, Wangen said.

Princeton Public Utilities tries to have three workers on staff when all five of its diesel engines are running, Wangen said.

“They have to monitor the units and take readings,” she explained. “The generators have to be constantly watched. We did a rotation with the help of a couple of our line crew workers who are familiar with the plant. They came in the next morning to help relieve. We also have a couple of supervisors who helped in that type of role.”

When natural gas service is curtailed by larger utilities, that’s when municipal power plants show their real benefits, Wangen said

Princeton traditionally provides power during summer peak periods, but last Tuesday as the extremely cold weather started to roll in, the local utility started getting prepared.

“We had to call in for another load of diesel fuel. That came in Wednesday night,” she said. “We were producing 11 to 12 megawatts of electrical power, and we were running just about at full capacity. We had a fuel line that broke on one unit, but the guys got it back and running in a short time.”

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