Corn Belt Power Cooperative’s Wisdom Unit 2 has operated more through September of this year than it has during any single year since 2014. Wisdom Unit 1 is not far behind, logging more operating hours through September 2018 than it has in any single year since the unit switched from burning coal to natural gas in 2014, and tallying almost as many unit starts as the highest annual total.
According to Jacob Olberding, vice president, power supply, the frequent unit starts and increased number of operating hours are due to reduced wind capacity resulting in higher market prices and the need for increased reliability in the area.
Through September, Wisdom Unit 2 has been called on to start 56 times, surpassing the 53 starts for all of 2016 and jumping far ahead of nine total starts in 2014, 23 starts in 2015 and 47 starts in 2017.
Also through September, Wisdom Unit 1 operated for 282 hours, much higher than the 139 hours it ran the entire year before and almost 400 percent higher than the 73 hours the unit operated in 2014.
“We tie the increased operation of both units to the reduction in wind capacity through this summer. That lower wind total impacts market pricing and makes the Wisdom units more economical to run,” Olberding explains. Basin Electric Power Cooperative communicates with Wisdom personnel when financial indicators result in the Wisdom plants being bid into the market the day ahead of operation.
In addition to economics increasing the operating time of the units, reliability needs can also determine when the plants are called to run. The Southwest Power Pool determines when the territory may need additional generation, due to other units being offline or reduced wind energy. These reliability unit commitment (RUC) calls to operate come to Wisdom via communication from Basin Electric.
Patrick Connor, plant manager, explains that the additional operating hours have a positive effect on Wisdom employees. “Operating helps keep employees practiced in running and maintaining the unit while it’s online. It gives us the opportunity to find problems that you’d have difficulty finding if you don’t get to run,” he says.
Although sometimes increasing the number of starts can wear on a plant, the Wisdom crew has not seen a significant increase in maintenance issues. Frequent starts often affect the boiler, with thermal expansion and contractions causing damage.
“Our crew watches the temperatures when they bring the turbine online so there is enough time to ramp up slowly and limit the amount of heat into the turbine,” Olberding explains.
Because Unit 1 takes about 12 hours to bring online and Unit 2 requires only about an hour, Unit 2 is called on to operate more frequently. Unit 1 has a minimum run time of approximately 12 hours to limit thermal issues when online, which can result in higher total hours of operation for that unit compared to Unit 2.
The trend of increased operation may continue if wind capacity also continues to be reduced; however, natural gas supply is more often curtailed during colder months due to people using gas to heat their homes. That curtailment would limit the availability of Wisdom Station to run on gas.
“We’re all chasing the wind,” Olberding says, “which will continue to drive the market up or down, depending on whether the wind is blowing.”