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Wednesday, June 6, 2018

More on Managing Wind

Feb 14, 2018

Dear Ed

Thank you for your valuable input and for watching my video clip.

You were right to suggest I test the venturi effects on turbine speeds, so today I completed a set of sixteen tests which seems to conclusively prove that a venturi increases wind turbine speeds, this effect is more dramatic when low wind speeds are tested.

My results are contained within this video which I just uploaded.

It was interesting as they showed that a smaller venturi exit hole size is more effective with lower wind speeds, increases in hole size favour higher wind speeds.

As with usual research and development, the more I learn the more I realise that there is much more I don't know.

Tuning the weight of the turbine and the diameter and the width of the blades is going to be important to achieve good efficiency. I think that a flywheel affect found by using a heavy turbine would dampen the wild fluctuations of wind speed but may cause it not to start at all in a very gentle breeze.

Also if the diameter is small it will spin faster but will product less torque than a larger diameter turbine. So there are trade offs which I observe to be highly correlated with those found if tuning a two stroke engine.

I had a vague idea to buy a petrol generator and work out its require running speed, then remove the petrol engine from it and connect the generator part to the turbine via a v-belt drive geared to suit which would then charge a Tesla type battery or provide direct power during winds.

As before, any comments you have would be welcomed


Thank you for sharing your process and for documenting your fluid-dynamic experiments.

You might consider measuring the overall efficiency of your funnel-concentrator system by computing the ratio of the power from the funnel to the power from the blower.

You can estimate stream power as the product of mass flux and velocity.

Since the two exhaust streams flow, by momentum, through ambient air, they have roughly equivalent densities.

Thus, you can simplify the efficiency metric to the ratio of (Velocity^2 * Area) for the two streams:

Efficiency = (Vf^2 * Af) / (Vb^2 * Ab)

I guesstimate the funnel tip diameter at 2" and the blower exhaust diameter at 12".

I gather from your measurements, you get a velocity increase of about 2x.

Thus, the overall efficiency of your funnel-capture system comes out to about:
Efficiency = (2 * 2 * 2 * 2) / (12 * 12) = .11.

Thus you lose about 89% of your power by passing the air through your funnel-concentrator system.

In practice, the power loss occurs mostly as leakage between the blower exhaust and the funnel wide-end entry point, as pressure builds up in the funnel and repels air from the blower.

You can remedy this by sealing the path between the blower and the funnel - with more duct tape, of course.

Note: this may occasion an increase in the pressure in the funnel, risking funnel blowout and perhaps damage to your blower that aims to move air, not to compress it.

You can also increase energy conversion efficiency by losing the funnel altogether and putting a windmill directly in front of the blower exhaust.

So that brings us full circle to the original windmill as the best solution - and helps explain how come funnel-concentrator schemes fail to deliver.

You might consider taking your feelings about <getting something for nothing> to Tribe as an entry point.

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