Thoughts on a New Hydrokinetic Turbine I Devised

I was thinking yesterday about a new floating, flow of the river hydrokinetic turbine blade design. The problem with them is, while the forward part of the rotation is under power by the flow of the river, the back half must rise through the turbulence making it inefficient and prone to Frazil ice contamination.

But

What if the blades were inflatable?

On the forward rotation they would be powered by the River, but at the six o clock spot in counter rotation, they would inflate with sir causing buoyancy and thereby rising giving power to that part of the rotation. At 12 o’clock counterrotation, they deflate so that they can be driven under the water. This would make the hydrokinetic turbin far more efficient.

Ghoughts?

Steve Zoma wrote:I was thinking yesterday about a new floating, flow of the river hydrokinetic turbine blade design. The problem with them is, while the forward part of the rotation is under power by the flow of the river, the back half must rise through the turbulence making it inefficient and prone to Frazil ice contamination.

But

What if the blades were inflatable?

On the forward rotation they would be powered by the River, but at the six o clock spot in counter rotation, they would inflate with sir causing buoyancy and thereby rising giving power to that part of the rotation. At 12 o’clock counterrotation, they deflate so that they can be driven under the water. This would make the hydrokinetic turbin far more efficient.

Ghoughts?

My first thoughts would be any gain in efficiency would be offset by the energy required to inflate and deflate and the extra drag created by the floats.

A couple of engineering conundrums are how much inflation would be required to provide a useful amount of bouyancy, and how rapidly would the blades have to inflate/deflate (maybe explosively at some RPM level)?

David Baillie wrote:My first thoughts would be any gain in efficiency would be offset by the energy required to inflate and deflate and the extra drag created by the floats.

I thought of that too, but wondered if a 25 percent gain or better, would be able to off set that? I know in our realm of Kaplan turbines we offset a lot of parasitic loads. Of course we measure our output and have a power factor of .997. When I worked in steam generation we had a power factor of .750. We produced more megawatts but not more efficiently per megawatt produced.

But you make a very valid point.

Dc Stewart wrote:A couple of engineering conundrums are how much inflation would be required to provide a useful amount of bouyancy, and how rapidly would the blades have to inflate/deflate (maybe explosively at some RPM level)?

I am not sure the rpm,s of hydrokinetic turbines. Coupled to the grid they could only spin at the same rate as the grid frequency and not over speed of course, but what that would be, I am not sure. We have Kaplans and we spin at 116 rpm before it goes to the speed increasers boosting it to 600 rpm so that are 8 megawatt Jennie’s are smaller in size.

Deflating would not be an issue as river water pressure would expel the air out of the bladderEd blades, but inflating them would be interesting. I wonder what the rate of inflation and deflation for airplanes is? I know it is fast to prevent ice bridging on deicing bladders but not sure of the cycle times.

Air is not incredibly efficient so guessing you will lose more than you gain plus get a maintenance headache.

C. Letellier wrote:Air is not incredibly efficient so guessing you will lose more than you gain plus get a maintenance headache.

Maybe...

I was thinking about this problem today and was wondering if there was a way to cross link the hydrofoils via air? By that I mean, as the air was extracted at the 12 o clock position for the forward rotation into the river, it would be sent to its opposing blade for its start back up the other side where floatation was required at the six o clock position. In this way air would just be readily exchanged from one blade to another constantly through its rotation.