Madison Powerhouse upgrade
The 109-year-old turbines are due for an upgrade
The NorthWestern Energy Madison Powerhouse downstream from Ennis Lake will begin construction to upgrade its turbines and generators in October 2019. The project is predicted to take a year and a half to complete.
While construction is underway the powerhouse will shut down and the water that usually goes through the powerhouse will pass through the bypass reach between the Madison Dam and Powerhouse. Water flows in this channel will increase significantly at times but flows downstream of the powerhouse will be unaffected during the construction.
“Overall downstream, the flows will not be affected,” NorthWestern Energy Senior Hydro Operation and Maintenance Engineer B.J. Cope said. “We’ll be operating within our license and 100% normal in the reach flow of the plant.”
The bypass reach can reduce to nearly a trickle because of the amount of water going through the flowlines, which direct it to the powerhouse. Those flowlines will be empty, so the 1.4-mile- channel in between the dam and the powerhouse will be higher than usual at times. NorthWestern Energy will still control the water flows through the Madison Dam.
The 109-year-old turbines and generators currently at the powerhouse have passed their useful life. Maintenance has grown increasingly expensive due to the dated parts. The four new units, which run off of a single turbine each instead of two, will be more productive and efficient in harvesting energy.
Peak capacity of the powerhouse will increase from eight megawatts to 12 megawatts using the same amount of water running through the plant.
“With our existing plant capacity at 1200 cfs about 75% of the time we’re at full load of that plant,” Cope said.
The new turbines will harness 95% of the power available from the water at the same flows used under NWE’s existing license, which will result in almost 15,000 additional megawatt-hours for an average water year, according to NWE.
“Because we have four units and they’re each 400 cfs, we now essentially have about the same utilization with only three units,” Cope said.
The fourth unit increases the power production about 21% on an average year because of the new capability of a backup unit when another unit is being repaired or undergoing annual maintenance.
In a public hearing on Sept. 10 about the powerhouse upgrade, Cope compared the cost for supply and energy generation with the different types of generations that are available to NWE.
“The cost to do this project and the cost of energy to get out of this project over the life cycle of this plant was very competitive with any new option for additional generation that we could do based on technology available,” Cope said. “From the cost of doing it and the cost to customers, it’s a very favorable project.”
Austrian company, Voith, was awarded the bid for the project and will factory test the large equipment before shipping.
Demolition of the powerhouse will begin in October. NWE expects short term impacts on access on the narrow dirt road leading to the powerhouse, especially on the front and back end of the project. Lots of trucks will be transporting equipment to and from the powerhouse. NWE is making previsions to limit the number of trips and will implement traffic control.