Invisible but vital, oxygen flows through water like a lifeline, sustaining aquatic life from the tiniest plankton to the largest fish and maintaining the delicate balance of ecosystems. However, this critical resource is not guaranteed. Oxygen levels in water can decline because of such factors as warming temperatures, increased salinity, stagnation, excess minerals like iron, and agricultural or industrial exploitation.
What if there was a way that would not only leverage the presence of hydropower dams to revive that oxygen but also improve a dam’s operational capability? Engineers at GE Vernova took a fresh look at this problem and arrived at an advanced solution: an aerating turbine, crafted with “inter-blade profiles” — openings that boost air injection along their surface — that more effectively transfer oxygen into the water flowing downstream. In the same way air flows through the blades of a jet engine, water courses through this new “runner” (the rotating hydraulic component of the turbine) and generates much smaller air bubbles than previous solutions.
Many dams must demonstrate that they can maintain strict levels of dissolved oxygen in the water as part of their ongoing licensure. This new runner design will help keep oxygen content above required levels. “Different biological processes eat up the oxygen that’s naturally in the water,” says Toussaint. “So aquatic life requires roughly between 5 and 10 milligrams per liter (mg/l) of dissolved oxygen to thrive. Below five, it puts a stress on fish and plants, and levels closer to zero can threaten their survival.”
Better still, this aeration process can enable more flexible power production, allowing dams to operate at very low flow rates. “It’s very complementary, in terms of assets owner’s needs,” says Kristopher Toussaint, hydraulic expert at GE Vernova.
The newly designed runner can help hydropower plants to continuously run at much lower output. The aerating runners are more robust while also smoothing water flow, thus expanding power output range.
“Usually, this type of turbine will operate between about 50% and 100% load,” Toussaint says. “That’s the conventional or standard range. But more and more assets owners are asking to operate the units over a wider range, and to have more flexibility to compensate for other variable sources of energy on the grid.” Indeed, with its new output range, a dam will have the ability to operate more like a battery. Flow rates can be turned up when area demand rises and turned down again, way down in fact, say at midday, when solar generation is plentiful. The new aeration equipment is designed to make this fine-tuning possible. This is not unlike a pumped hydro storage facility that uses stored water and gravity as a kind of battery that can be drawn on when needed, addressing the variability problem by being one big form of energy storage.
GE Vernova’s solution is an improvement over more basic methods, which can see dams perform a raw spill of water to try to force oxygen levels higher. Such a crude method to bring oxygen back above the minimum 5 mg/l level, is also quite unhelpful to energy production, says Toussaint. The new equipment from GE Vernova has also now been patented. “I think the real strength of our technology is the physical implementation of an additional profile inside the turbine, which allows us to generate suction, to draw in more air than what other manufacturers can achieve, and at the same time provide additional structural rigidity.”
Hydropower generates a precious 15% of the world’s electricity, making it a crucial source of low-carbon energy. This new aeration equipment, along with other general repairs needed to update legacy structures, are designed to nicely extend the life of these aging dams. “These refurbishments are expected to help these units remain viable for another 50 years.”
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