Dam Makeovers: Boosting Power and Fish Survival Through Cutting-Edge Turbines

Alcoa, for one, has benefited from this spotlight on renewable energy because one of its retrofit projects was ready to go when the federal government opened the funding spigot under the American Recovery and Reinvestment Act last year. Just last month, Alcoa resumed construction for the $120 million modernization work at its Cheoah Dam in North Carolina after securing $12.9 million in stimulus money from the U.S. Department of Energy (DOE).

“The project started in mid-2008, but the economic crisis hit us hard, and we had to put it on hold,” says Bill Bunker, vice president of hydropower at Alcoa Power Generating. “Thanks to the DOE money, we are back on.”

Alcoa isn’t the only beneficiary of the government largesse. Voith Hydro is one of the technology developers who will get a slice of the stimulus funding. Voith Hydro will not only be providing the turbine generators for Alcoa’s project, it also will supply equipment to PPL’s project to more double the capacity of its 108-megawatt Holtwood project in Pennsylvania.

The $434 million project will increase the plant’s capacity by 125 megawatts and improve fish passage along the Susquehanna River, said PPL, which postponed and then restarted the project to take advantage of the recovery act programs to awards tax credits, grants and loan guarantees for renewable energy projects. PPL has since ditched the plan to pursue a loan guarantee. 

The government’s intense interest in promoting renewable energy also creates new technology development initiatives. Back in March, the DOE, the U.S. Department of Interior and the Army Corps of Engineers signed a memorandum of understanding to collaborate on technologies that will increase hydroelectricity generation while minimizing environmental impact.

But the hydropower industry hasn’t received nearly as much funding as project developers and manufacturers of other types of renewable energy technologies, notably wind and solar. Industry groups such as the Electric Power Research Institute (EPRI) and the National Hydropower Association (NHA) have stepped up efforts to remind lawmakers that hydropower is a clean source of electricity worth more public investments.

Untapped potential for hydropower generation in the United States could lead to nearly 14,000 megawatts added to the electricity supply by 2025, says Doug Dixon, a technical executive with EPRI. The country currently has about 75,000 megawatts of capacity, he added. Both figures don’t account for pump storage.

NHA, on the other hand, points to Navigant Consulting’s report that projects an added capacity of 11,250 megawatts to 19,900 megawatts during the same period, depending on whether a national mandate for renewable energy consumption exists.

Dixon points out that the federal government has beefed up the annual budget for DOE’s water power program in recent years. The funding was zero from 2005-2007, he says. In fiscal 2008, $10 million materialized for the budget, which grew to $40 million in 2009 and $50 million in 2010.

“A lot of people thought you couldn't build new dams, so hydro was considered dead. Hydro was never dead,” Bunker says. “The fact is that hydro is renewable; it's green power going into the grid. Legislators are starting to realize that." 

Remaking Cheoah Dam

A renewed interest by the government to invest money in hydropower has inspired active pursuits by project developers and dam operators to survey the landscape for suitable locations and resources. Building new dams remains unattractive because it invites strong environmental opposition.

But adding new capacities to existing dams has become appealing, particularly in the Midwest, where dams that rose up initially for flood control, irrigation and recreation are attracting interest from communities looking for new job-creating opportunities and affordable clean power.

“One of the benefits we are getting is the increase in turbine efficiencies,” Bunker says. “We will use less water to generate more power. Today’s technologies allow us to glean more power out of existing dams.”

Alcoa is replacing four of the five Francis turbines and generators at Cheoah, which was built in 1919. Each of the four existing, 21-megawatt turbine generators will be uprooted to make way for four, 27-megawatt units from Voith, Bunker says. The project also includes building a new substation, with transformers from ABB.  

The DOE money is a matching fund for two of the units. Installing the two units, along with a substation, is scheduled for completion by the end of 2012, Bunker says. After that, Alcoa will replace the two other units. The fifth turbine generator, at 33-megawatt, will not be replaced as part of this project because it was a newer addition to the powerhouse.

Meanwhile, American Municipal Power (AMP) is carrying out a high-profiled project to build six powerhouses at dams along the Ohio River that previously had no electricity-generating operations. AMP has broken ground on the three projects, including one at the Smithland Locks and Dam. The Smithland project is set to cost more than $400 million to add 72 megawatts, and is scheduled to begin producing electricity in spring 2014.

Two other projects underway are taking place at the Captain Anthony Meldahl Locks and Dam and the Cannelton Locks and Dam. Overall, AMP expects to build more than 350 megawatts of capacities through the six projects.

Dixon notes almost all proposed projects to add electricity production to previously non-power generating dams have come from private developers including, in the case of AMP, those that are taking place on federal dams. A 2007 survey by the Army Corps of Engineers showed that 1,230 megawatts can be added to federal dams without power production operations, and an additional 1,283 megawatts could come from modernizing old powerhouses at other federal dams.

“Because it was so conservative that they are re-doing that assessment,” Dixon says.

Fish-Friendly Technology

Not surprisingly, developing more efficient turbines and fish-friendly technology often goes hand-in-hand these days. Squeezing more power from a dam doesn’t only involve better turbine designs. Hydropower plant operators count water diverted from going to the turbines in order to help juvenile fish move downstream as a loss of power production, yet this is one of the primary methods for ensuring fish passage, particularly in the Pacific Northwest, says Thomas Carlson, a senior scientist with Battelle at the Pacific Northwest National Laboratory (Battelle operates the lab under a federal contract).

In fact, studies showed that this bypass spill in general gives the fish the highest survival rate but is also the most expensive method. The Bonneville Power Administration once estimated spills cost $1.2 billion in hydropower revenue between 1978 and 2001 among federal hydropower operations on the Columbia River.

“The serendipity here is there are designs that optimize power production and also provide benefits for the fish,” Carlson says.

Researchers and engineers rely on computer modeling and building physical models to assess which turbine designs can boost both power production and fish survival rates. They play with the shapes, rotational speed and numbers of the blades, as well as the gap between the blades, to minimize the number of fish strikes as they pass through the turbines.

Turbine efficiencies, which currently are in the mid-80 percent, can get up to the 90s, Carlson says. At the same time, it’s possible to reduce the fish mortality to 2-5 percent today, given combination of turbine technology and configuration of the dam, he adds.

Voith Hydro is currently working on two projects to design fish-friendly turbines. Headed by EPRI and funded by the DOE and industry, the first project involves developing mechanical and other equipment for a conceptual and radical turbine design from the Alden Research Laboratory, says Jason Foust, a hydraulic engineer at Voith Hydro.

Instead of the 13-17 blades that are common in Francis turbines, the Alden turbine uses three blades, Foust says. The Alden blades also are longer and taller to accommodate the necessary pressures, shear rates and pressure change rates to allow for safe fish passage, he adds.

The project is in the final engineering stages, and will soon demonstrate whether the turbine can deliver ample power while reducing harm to fish. Engineering and modeling work is set for completion in 2011.

Although the turbine can become a candidate for powerhouse retrofit projects, it’s “not the favorite because it’s not a drop-in unit but will result in a reconfiguration of the powerhouse,” Dixon notes. “That can be expensive.”

Voith Hydro also is under contract to deliver two turbines for the Ice Harbor Dam on the Snake River in Washington State. The U.S. Army Corps of Engineers announced an $11 million contract to the company in March. Improving fish survival rates is the primary goal of the project, which sets out to design a Kaplan turbine with a new propeller design. Engineers are looking at reducing the number of blades to a range of 4 to 7, Foust says.

A Matter Of Policy

Although the federal government has doled out billions of dollars for renewable energy research, manufacturing and generation, many advocates believe a feed-in tariff is one of the best ways to supercharge clean power developments.

In Ontario, for example, a feed-in tariff policy that sets premium prices for renewable electricity has created a flood of proposed projects in solar, hydro and other renewable energy projects, notes Kaz Borovszky, business development manager for power generation at ABB.

The Ontario government has approved 42 small hydropower projects, which are 10 megawatts or less, Borovszky says. The cap on the project size is meant to encourage more eco-friendly development. The small size makes it impractical to build large reservoirs and dams, which have a greater impact on the environment.

But he notes that the size of the project doesn’t always define whether it leaves a light environmental footprint.

“We are involved in a 300-megawatt project in Peru that is run of the river – you divert part of the river flow into a powerhouse so that you don’t need a dam,” Borovszky says. “Size doesn’t define what’s green.”