Utility schedules turbine, generator upgrades

NorthWestern Energy officials said the utility will begin upgrading 109-year-old turbines and generators in the Madison Powerhouse downstream of Ennis Lake this fall.

The original powerhouse building will remain in place and be largely unaltered while four new turbine-generator units are installed within it. The project requires no alterations to the dam or flow conveyance structures.

The modifications will translate to the peak capacity of the powerhouse increasing from eight megawatts to 12 megawatts. The new turbines will efficiently harness 95 percent of the power available from the water at the same flows used under the existing license, resulting in almost 15,000 additional megawatt-hours for an average water year.

The scope of work involves the four generating units being updated to a modern design, moving from two turbines per unit to just one and in addition to increasing energy capacity and efficiency compared to the present generators, the new units will also be more fish friendly.

The powerhouse will be shut down during construction, officials said, and water usually conveyed through the powerhouse will be passed through the bypass channel. During some of the construction project, flows in the bypass channel between Madison Dam and Powerhouse will be significantly, but flows downstream of the plant will be unaffected during the project.