r/Renewable • u/Illustrious-Brief718 • 7d ago
River Current Energy
I’m researching renewable energy technologies for a large navigable freshwater river and would appreciate some engineering input. The river reach I’m looking at has an average discharge of ~8,076 m³/s, an estimated river-current power resource of ~290 MW, and an average annual energy resource of about 2,540 GWh/year before recovery factors. The flow is relatively consistent, and I’m trying to determine what type of in-stream energy technology would be the best fit. I’m considering horizontal- or vertical-axis hydrokinetic turbines, ducted turbines, oscillating hydrofoils, biomimetic membranes, or other emerging technologies.
For a river with this level of flow, along with commercial navigation, debris, sediment, and environmental considerations, what technology would you recommend and why?
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u/Responsible-Mall-991 7d ago
Are you talking about run-of-river hydroelectricty?
And what are you trying to power? A house? A mill? Charge batteries?
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u/Illustrious-Brief718 6d ago
Run-of-river hydroelectricity usually uses a low dam, weir, or diversion. I'm referring to the kinetic energy of moving water without requiring a dam. I would like to use the device to power remote river monitoring, sensing, and navigation equipment.
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u/NearABE 7d ago
Is it OK to back up the river 3.5 meters?
How do we know about the sediment conditions without knowing the river? That varies by quite a bit. In general though the river slow upstream from where you are taking energy. After reaching equilibrium the total flow is the same. Larger volume at slower velocity. Likely for sediment to fill in the volume. Eventually could return to the speed it had before you constricted it.
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u/Illustrious-Brief718 6d ago
From the data I found for the Ohio River near this area, suspended-sediment concentrations were generally around 5–979 mg/L, depending on the flow conditions. At the Metropolis station, the reported range was about 11–628 mg/L, with an annual suspended-sediment yield of about 400 tons/mi². The Ohio River also has a maintained navigation depth of around 9 feet (2.7 m) in the navigation channel. I would not be able to back up the river 3.5 meters.
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u/NearABE 6d ago
At Pittsburg it is 220m, 739 ft. Hit the Mississippi at 88m, 290 ft. So there is 132 meters to work with. A lot of it is already lock-dam so those drops are not available. Or, rather, they should just use hydro.
The flow of river energy production just needs to be spread out over a longer stretch.
The sediment situation calls for pumped hydro IMO. Dredging combined with farm irrigation. Start with a bunch of solar and wind so that we have surpluses.
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u/Kaurifish 7d ago
How’s the forecast for water flow? So many rivers are drying up.
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u/Illustrious-Brief718 6d ago
The current flow conditions look pretty good. The river is flowing at around 7,360 m³/s, which is fairly close to the 8,076 m³/s average flow for the reach. It does not look like there is a major low-flow or drying-up issue right now.
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u/Sparky_Shark109 7d ago
There is a lot of work going on right now regarding hydro kinetic energy generation using submerged turbines! I believe that horizontal flow turbines are often more efficient than vertical axis turbines individually, but vertical axis turbines are easier to pack together for 2+ turbine arrays, potentially making them more viable in constrained situations; however, they are less well understood as horizontal turbines have the benefit of large scale use in the wind industry to inform their use. Another benefit for vertical access turbines is that they are able to convert energy from flow regardless of direction, which would negate the need for a yaw control system like an optimized horizontal-axis turbine would need (though I suppose the river flow is pretty unidirectional).
TL;DR: Vertical axis turbines are promising but less well understood than horizontal ones. It is worth looking at both, but I personally see a lot of potential with vertical axis turbines!
Here is a group that puts out a lot of research in the topic! https://pmec.us/research/current-turbine-performance-in-confined-flows/
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u/Low-Elevator2850 6d ago
The formula of use is P=Qxgxh, and if P in kW Q is in qm. 8076 qm/s and 290 MW will give head off 3,7 m.
Normally Kaplan turbines are used, but center flow rotor engine was patented in 2019, and can be a better alternative.
To get the desired head a dam have to be used.
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u/sol_beach 7d ago
is a DAM required for the implementation of this renewable energy technology?