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Tiny Bubbles, Big Impact: How A Hydro Power Plant Could Help Save A North Carolina Lake

Bruce Watson
July 11, 2017
From its banks, North Carolina’s Tuckertown Lake appears to be the perfect suburban oasis. Just a short drive from Charlotte, it’s listed as one of the top fishing spots in the state. But below the surface, it’s another story. Decades of farm and construction runoff have nourished huge clumps of oxygen-depleting black algae, locally known as “snot grass,” that threaten the lake’s population of bass and other fish.
A local company created the lake a hundred years ago when it placed a series of dams with generators along the Yadkin River to produce electricity and power the local economy. Now one of the dams could be part of the solution to the oxygen deficit in the water.

Last year, when Cube Hydro Partners bought the hydroelectric plants and proceeded to replace three turbines, CEO Kristina Johnson turned to GE. She knew that GE had spent years developing an efficient oxygenating turbine.

In the same way rivers and streams mix the oxygen needed for a healthy ecosystem into the water through waterfalls, rapids and other fast-moving areas, GE’s aerating turbines pull in air through naturally occurring low-pressure points, then mix it with the water on the front side of the turbine blades.

By comparison, most oxygenating turbines mix the air on the back side of the blade, which produces a smaller number of larger bubbles. “The small air bubbles injected by this aeration system have a better surface area to volume ratio,” says David Scott, a hydraulic engineer at GE Renewable Energy. “The bubbles — and the oxygen in them — spread out more evenly over a given unit of water and are better able to flow past obstacles. The result is more oxygen for fish and other aquatic life downstream.”

 width= Top: The dams that form Tuckertown Lake along North Carolina’s Yadkin River have generated electricity for a century. Now the hydropower plants’ owner plans to use one of them, equipped with GE’s aerating turbines, to rebalance the lake’s oxygen levels. Above: The turbines pull in air and then mix it with the water on the front side of the turbine blades. Images credit: GE Renewable Energy

When Johnson met with GE last year to discuss replacing the turbines, they realized the time was right to use the new tech. In June, GE and Cube Hydro signed an agreement to provide three new GE aerating turbines to the High Rock plant sitting above Tuckertown Lake. The new turbines, the first of which will be delivered in fall 2018, will generate electricity but also add 5 milligrams of oxygen to every liter of water that pours through them, providing continuous fresh air — and life — to the lake.

Cube Hydro owns and operates 19 hydro plants in the U.S., and GE hopes that the upgrade will show how GE’s aerating technology can benefit hydro plants around the country.

The Cube Hydro management team — including Johnson, who served on GE’s Ecoimagination board — also sees the potential of digitizing the predominantly analog hydropower industry. And GE’s digital hydro plant technology could help Cube Hydro find additional savings on operations and maintenance at the plant. Coupled with higher output, the new technology could pave the way for more renewable energy for Cube Hydro — and a fresh start for lakes along the Yadkin River.