Some old dams are being given a new power: generating clean electricity

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As countries race to get their power grids off fossil fuels to fight climate change, there's a big push in the U.S. to upgrade dams built for purposes such as water management or navigation with a feature they never had before — hydroelectric turbines. 

And the strategy is being used in parts of Canada, too.

The U.S. Energy Information Administration says only three per cent of 90,000 U.S. dams currently generate electricity. A 2012 report from the U.S. Department of Energy found that those dams have 12,000 megawatts (MW) of potential hydroelectric generation capacity. (According to the National Hydropower Association, 1 MW can power 750 to 1,000 homes. That means 12,000 MW should be able to power more than nine million homes.)

As of May 2019, there were projects planned to convert 32 unpowered dams to add 330 MW to the grid over the next several years.

One that was recently completed was the Red Rock Hydroelectric Project, a 60-year-old flood control dam on the Des Moines River in Iowa that was retrofitted in 2014 to generate 36.4 MW at normal reservoir levels, and up to 55 MW at high reservoir levels and flows. It started feeding power to the grid this spring, and is expected to generate enough annually to supply power to 18,000 homes.

It's an approach that advocates say can convert more of the grid from fossil fuels to clean energy, often with a lower cost and environmental impact than building new dams.

Hydroelectric facilities can also be used for energy storage, complementing intermittent clean energy sources such as wind and solar for a more reliable, resilient grid.

The Nature Conservancy and the World Wildlife Fund are two environmental groups that oppose new hydro dams because they can block fish migration, harm water quality, damage surrounding ecosystems and release methane and CO2. But they say adding turbines to non-powered dams can be part of a shift toward low-impact hydro projects that can support expansion of solar and wind power.

Paul Norris, president of the Ontario Waterpower Association, said there's typically widespread community support for such projects in his province. "Any time that you can better use existing assets, I think that's a good thing."

New turbine technology means water doesn't need to fall from as great a height to generate power, providing opportunities at sites that weren't commercially viable in the past, Norris said.

In Ontario, about 1,000 unpowered dams are owned by various levels of government. "With the appropriate policy framework, many of these assets have the potential to be retrofitted for small hydro," Norris wrote in a letter to Ontario's Independent Electricity System Operator this year as part of a discussion on small-scale local energy generation resources.

He told CBC that several such projects are already in operation, such as a 950 kW retrofit of the McLeod Dam at the Moira River in Belleville, Ont., in 2008.