Coal, Gas, Hydroelectric

Squeezing More Power from Hydropower Plants

Issue 3 and Volume 117.

The reconstruction of the Badger Hydro Project is a massive project that required two coffer dams, the removal of more than 5,000 fish, draining the man-made canal and the removal of several tons of bedrock from the 130-year-old canal. Photo courtesy of The Boldt Company.
The reconstruction of the Badger Hydro Project is a massive project that required two coffer dams, the removal of more than 5,000 fish, draining the man-made canal and the removal of several tons of bedrock from the 130-year-old canal. Photo courtesy of The Boldt Company.

By Russell Ray, Managing Editor, and Justin Martino, Associate Editor

At some point, that car you’re driving will need a little restoration work.

After some machining work and a few replacement parts, it will run a little smoother, get better gas mileage and go from a rumble to a purr. With the right retooling and equipment, you’ll get a lot more miles and production out of it.

With greater significance, the same is true for hydropower plants.

Many of the hydropower plants in North America are more than 50 years old and are in need of rehabilitation. They represent a phenomenal opportunity to increase the production of renewable energy amid deep concern about climate change.

Consider this: A simple rehabilitation can increase a hydropower plant’s power output by as much as a third. Adding modern hydraulics, new runners, new wicket gates and modifying the draft tube can add a significant amount of clean power to the grid.

There are about 2,400 hydropower plants in the U.S. Upgrading those plants with modern technologies could add a significant amount of hydropower capacity to the nation’s power portfolio without building a single dam.

What follows are descriptions of three hydropower rehabilitation projects in the U.S. – Cheoah, Webbers Falls and Badger.

Cheoah

On-line Date: 1919
Value of Work: $110 million
Expected Completion Date: Spring 2013

 

The Cheoah Hydropower Project in North Carolina was completed in 1919 on the Little Tennessee River. It is being rehabilitated at a cost of $110 million. The project's owner, Alcoa Power Generating Inc., is replacing four 90-year-old Francis turbines with new high-efficiency turbine-generators and transformers from Voith Hydro and ABB.
The Cheoah Hydropower Project in North Carolina was completed in 1919 on the Little Tennessee River. It is being rehabilitated at a cost of $110 million. The project’s owner, Alcoa Power Generating Inc., is replacing four 90-year-old Francis turbines with new high-efficiency turbine-generators and transformers from Voith Hydro and ABB.

Cheoah Dam is the site of one of the most famous chase scenes in movie history.

The dam was featured in the 1993 movie The Fugitive as Tommy Lee Jones chased Harrison Ford to the end of a series of tunnels within Cheoah Dam. That’s where Ford pledged his innocence one last time. “I didn’t kill my wife,” Ford said. Then Jones delivers his legendary line. “I don’t care.” Ford jumps from the 225-foot dam into the waters far below.

The famous North Carolina hydropower project was completed in 1919 on the Little Tennessee River. In addition to Cheoah’s memorable place in movie history, it is an important source of clean energy and is being rehabilitated at a cost of $110 million.

The project’s owner, Alcoa Power Generating Inc., is replacing four 90-year-old Francis turbines with new high-efficiency turbine-generators and transformers from Voith Hydro and ABB. The improvements, which are expected to be fully completed later this year, will extend the life of the facility by 40 to 50 years, Alcoa officials said.

What’s more, the rehab project has already yielded results that have far exceeded expectations. A 28 percent increase in capacity was one of the objectives for the project.

“We are pleased to be able to announce that Cheoah Dam has actually demonstrated a 50-percent increase – from 88 MW to 132 MW,” said Mark Gross, Alcoa’s Hydro Operations Manager.

In addition to the capacity improvements, the modernization efforts have eliminated the use of circuit breaker oil and minimized the need for transformer oil. The result is a net decrease in total oil volume in high voltage equipment of almost 40,000 gallons. Also, by using air-cooled transformers, cooling water requirements have dropped by 122,000 gallons per day, Alcoa said.

The Department of Energy awarded Alcoa nearly $13 million for the improvements through stimulus money provided by the 2009 American Recovery and Reinvestment Act. When the grant was announced in 2009, Energy Secretary Steven Chu said: “One of the best opportunities we have to increase our supply of clean energy is by bringing our hydropower systems into the 21st century. With this investment, we can create jobs, help our environment and give more renewable power to our economy without building a single new dam.”

The first phase of the modernization project was completed last year and involved the upgrade of two of the four Francis turbines and generators. In addition, Alcoa has replaced the governors, step-up transformers and switchgear. Units 3 and 4 are expected to come online by spring 2013, Alcoa said.

Webbers Falls

On-line Date: 1973
Value of Work: $72.7 million
Expected Completion Date: June 2017

 

Three slant-axis turbines are being rehabilitated at the Webbers Falls Hydropower Project in Oklahoma. The three turbines, with a rating of 20 MW, are being rewound and upgraded to provide 25 MW of power at all times. Photo courtesy of U.S. Army Corps of Engineers.
Three slant-axis turbines are being rehabilitated at the Webbers Falls Hydropower Project in Oklahoma. The three turbines, with a rating of 20 MW, are being rewound and upgraded to provide 25 MW of power at all times. Photo courtesy of U.S. Army Corps of Engineers.

When the U.S. Army Corp of Engineers began the process of rehabilitating the three slant-axis turbines at Webbers Falls hydroelectric power plant, they realized there wasn’t any precedent on the best way to proceed with the project.

Only two hydroelectric plants in the world use slant-axis turbines of the size used at Webbers Falls. Ozark Powerhouse, which is also in the middle of rehabilitation project, uses five of the turbines.

“There was no book on how to rehab slant-axis turbines,” Webbers Falls power plant specialist Howard Davidson said. “We took the attitude of a big R and D project.”

Because it was the first time turbines of this type had ever been rehabilitated, Davidson said the contract was written in order to give Andritz Hydro, the contracting company, more room in order to determine the best way to proceed with the project. The rehabilitation time will be shorter with each turbine that is rehabilitated.

The three turbines, rated at 20 MW with a 23 MW overload capacity, are being rewound and upgraded to provide a constant 25 MW of power. In addition, the rehabilitated turbines will be easier to maintain and will break less because of design deficiencies.

The slant-axis turbines, which were built around 40 years ago, were based on a design that was popular in Europe. Davidson said those slant-axis turbines were much smaller, usually 2 or 3 MW, and would run constantly with no maintenance. Replicating the turbines on a larger scale “didn’t translate well,” he said.

“It was a design failure, is what it was,” he said.

To make the units larger, a speed increaser had to be added to the turbine, unlike the direct drive system used in smaller slant-axis turbine. The increaser raises the speed from 50 rpm to 514 rpm, Davidson said.

Many of the problems were caused by the lack of technology available when the turbines were originally built. Because of some of the deficiencies caused by the technology available at the time, there have been problems with the current turbines, including the mainshafts breaking. As part of the rehabilitation, the mainshafts are being replaced with larger designs that do not weigh more than the original mainshafts. In addition, components are being made of stainless steel to resist corrosion from the Arkansas River.

“The biggest advantage, and this is the biggest hope on the new design, is to correct the problems the ’60s and ’70s,” Davidson said. “It just wasn’t put together with the technology and know-how we have today. That’s what we’re doing here. We’re taking modern technology that didn’t even exist back in the ’60s and fixing the problem.”

The rehabilitation was first discussed more than 10 years ago, Davidson said, but took some time to start because the work had to be 100 percent customer funded before the rehabilitation could begin. The power plant came within 30 days of the contract for rehabilitation lapsing when the Southwestern Power Administration funded the project through customer funding subagreements. The total cost of the project at the time was estimated to be around $72 million.

Although the first turbine to be rehabilitated has been completed, the unit is currently unwatered after going through testing but will resume operation after some minor modifications are made. Davidson said there is nothing wrong with the unit.

“Once that list is done, we’re going to water that thing up and get it online and make money off it,” he said.

Davidson said work on the other turbines should go more quickly as the teams learn more about the process of rehabilitating the slant-axis turbines, and estimated the entire rehabilitation would be finished by 2017 at the latest. The finished product will be a clean source of renewable energy that will help provide power without the emissions of other types of power generation, which is one advantage of rehabilitating hydroelectric plants.

“We didn’t have to reinvent the wheel,” Davidson said. “We had a structure here with an existing unit. You hate to let anything like this go because, let’s face it, they’re not building hydroelectric facilities anymore.”

Badger hydro

On-line Date: 1908
Value of Work: $38 million
Expected Completion Date: Late 2013

 

The $38 million reconstruction of the Badger Hydro Project is expected to be completed late this year. The first sections of two draft tubes are shown here, placed after bedrock excavation at the site of a new powerhouse. Photo courtesy of The Boldt Company.
The $38 million reconstruction of the Badger Hydro Project is expected to be completed late this year. The first sections of two draft tubes are shown here, placed after bedrock excavation at the site of a new powerhouse. Photo courtesy of The Boldt Company.

The Badger Hydro Project on Wisconsin’s Fox River has been generating power for nearby residents for more than 100 years. The two powerhouses that were built in the early 1900s are being replaced by a new powerhouse with 21st-century technology.

The new powerhouse will have a capacity of 7 MW, up 40 percent compared with the two old powerhouses. The output is small, but the reconstruction of Badger Hydro is a massive project that required two coffer dams, the removal of more than 5,000 fish, draining the man-made canal and the removal of several tons of bedrock from the 130-year-old canal. The new horizontal “S” type turbines were supplied by Voith Hydro.

The widening and regrading of the 2,100-foot-long canal will increase water flow and power output.

The $38 million reconstruction project, overseen by The Boldt Company, is expected to be completed late this year.

The Badger facility is owned and operated by Kaukauna Utilities, a utility serving 14,000 customers.

“We knew we had to replace the canal,” said Mike Pedersen, manager of Generation and Operations for Kaukauna Utilities. “It was starting to deteriorate. We were starting to get some leaks.”

Replacing the plants was deemed the best option for customers because the savings will far outweigh the $38 million cost, the utility said. The hydropower plants have saved customers $60 million over the last decade compared with the cost of power generated by a plant fueled with gas or coal.

Repairing the plant would have extended the life of the facility by just 20 years. Rebuilding it means the facility will be able to provide low-cost, renewable power to customers for another 100 years. Retiring the powerhouses and buying replacement power would have cost customers significantly more in the long run, the utility said.

“We evaluated eight options and the best long-term cost option was to build the new powerhouse and remove the four units,” Pedersen said. “This was the most economical way to go.”

Of the $38 million cost, about $10.5 million was spent on widening and upgrading the canal.

The improvements to the canal were mandated by the Federal Energy Regulatory Commission.

More Power Engineering Issue Articles
Power Engineerng Issue Archives
View Power Generation Articles on PennEnergy.com