Lancaster, Tenn. – The U.S. Army Corps of Engineers Nashville District and Voith Hydro Inc. of North America completed refurbishment of the three turbine-generators at Center Hill Hydropower Plant, August 2021.
“We rewound the generator and refurbished the shaft, thrust bearing, and servomotors. We replaced the wicket gates and turbine runners with state-of-the-art technology,” said Loren Mc Donald, project manager for the Center Hill Powerplant rehabilitation project.
The project team included engineers, electricians, mechanics, machinists, safety, quality, and project management personnel from the Nashville District, the Hydroelectric Design Center, and Voith Hydro Inc..
Center Hill is the first turbine-generator rehabilitation project spanning 9 plants that house 28 generators along the Cumberland River Basin.
The hydroelectric units at Center Hill, like many of the aging infrastructures throughout the United States, had far exceeded their original design life. The generators had become unreliable and decreased in efficiency. New advancements in technology help proliferate the turbine’s efficiency beyond the original 1950s design.
The auto-venting turbines provide improvements to the water quality by increasing the dissolved oxygen content of the water during certain times of the year. The hydropower plant now has modernized units that raise the dissolved oxygen level in the water passing through the generators for water quality while also delivering more than thirty percent more power than the original generators.
The project funding contract was awarded to Voith Hydro in June 2014 for $47.25 million. It was funded utilizing revenues from the Cumberland River hydropower facilities through agreements with the power preference customers and the Southeastern Power Administration.
The rehabilitation was completed one generator at a time. After a year of offsite vendor engineering and manufacturing, fieldwork began in July 2015. The third and final generator was returned to service in March 2021.
“Voith Hydro is very proud of the work done at Center Hill. The project has been challenging from many aspects, and to provide a solution that significantly improves the dissolved oxygen levels below the dam was a tremendous technical accomplishment by all the team members involved,” said Eduardo Tosi, Voith Hydro Inc. project manager.
Voith Hydro Inc. has completed many projects with various USACE Districts across the country. The Center Hill Modernization project is the second major project with the Nashville District.
“The aeration technology Voith Hydro deployed at Center Hill is far more advanced than the first aerating runner Voith installed at the Tennessee Valley Authority’s Norris Dam nearly 30 years ago,” said Tosi.
“Most modernization projects experience changes during the execution of the work due to unexpected corrosion that is discovered once the machine is taken out of service for the first time after decades of operation,” said Tosi.
McDonald compared taking apart an old hydropower generator to disassembling an antique car: there’s never 100% certainty of what may be found.
Engineers discovered many unforeseen complications, like the replacement of two head covers, which resulted in delays, additional analysis, and significant rescheduling.
“Discovering these complications in the middle of construction ultimately delayed the completion of the project, yet site crews still accomplished more than 2,065 days onsite without any lost time or injury,” said McDonald.
“Strong partnerships between our design team, plant staff, and contractors was important for overcoming unexpected discoveries, and the team did an excellent job at communicating these changes and working diligently to keep the project moving forward,” said Tosi.
Lessons learned at Center Hill will be utilized at other USACE plant rehabilitation projects like Wolf Creek Dam. Those generators have the same design as Center Hill and will need similar head cover replacements.
Maintaining up-to-date restorations of these hydropower plants increases generator efficiency and benefits customers and the local community by helping to keep power rates low.
The U.S. Army Corps of Engineers Hydropower Program is the largest generator of hydropower in the U.S., generating 25% of our nation’s hydropower, with 75 power-producing dams which house 356 individual generators. The power plants produce more than 70 billion kilowatt hours per year of clean renewable energy, enough to power 10 cities the size of Seattle.
Hydropower provides cost-effective carbon-free energy to the community and helps keep power rates low.
USACE Hydropower is the 5th largest electric supplier in the U.S. and saves 50-million-metric-tons of carbon dioxide-equivalent emissions per year.
(The public can obtain news, updates and information from the U.S. Army Corps of Engineers Nashville District on the district’s website at www.lrn.usace.army.mil, on Facebook at http://www.facebook.com/nashvillecorps and on Twitter at http://www.twitter.com/nashvillecorps.)