Thread: Rail Wind Turbine: can it be done?

This is a question I wanted to ask someone who knows a little about engineering. I recently saw this Veritasium video on the “blackbird” a device which uses the power of the wind to go faster than the wind. Sailboats commonly do it. It’s counterintuitive, but the way it works is there is some kinetic energy present in an area of surface between the air and sea, as they move at different speeds. The boat uses this to accelerate, which allows it to harvest more kinetic energy as it crosses more area, up to a limit. The blackbird moves directly into or away from the wind, and can in principle just keep accelerating, provided there is a constant wind.

I was able do concoct a thought experiment, a bike in a dugout path under a train, with a planetary gear connected toa wheels going up and down to harness the difference in speeds between the ground and train, to turn the pedal crank, and then use a standard rear shifter to make the bike go faster than the train. It sounds weird, but the physics aren’t different then if the slow train hit the short arm of a lever, propelling a mouse on the long arm up to high speeds. When a sailboat cuts at a high speed in diagonal to the wind, it slows all the wind in the area it cut through, to similarly achieve speeds greater than the wind because it’s mass is less than the wind it slowed.

So the question is, why isn’t this used in wind turbine design? A fixed wind turbine gets it’s energy from the energy between the wind and ground at one point, but why can’t they be like sailboats, where they cut at high speeds across a large area, harnessing all the kinetic energy between the wind and ground across a large area, (I guess on a rail or something) but not using much more material? Your thoughts?

A little more information, the Veritasium video showing the blackbird working can be found by searching youtube for "risking my life to settle a physics debate". I guess the unlimited acceleration was pretty creepy.

The basic question I'm asking is, given there is kinetic energy available to harvest in the difference of velocities between ground and air, can a wind turbine use some of that energy to move itself, like the blackbird shown or a sailboat, in order to harvest more kinetic wind energy than if it was stationary, thus generating more power with the same material? Or what expertise would someone need to answer? Thanks for any input.

Originally Posted by LambdaWe

A little more information, the Veritasium video showing the blackbird working can be found by searching youtube for "risking my life to settle a physics debate". I guess the unlimited acceleration was pretty creepy.

The basic question I'm asking is, given there is kinetic energy available to harvest in the difference of velocities between ground and air, can a wind turbine use some of that energy to move itself, like the blackbird shown or a sailboat, in order to harvest more kinetic wind energy than if it was stationary, thus generating more power with the same material? Or what expertise would someone need to answer? Thanks for any input.

Where would the extra energy come from? You have a certain wattage of energy available from the wind, per unit area exposed to it. To extract more energy, the machine would have to intercept wind from a greater area, surely? How would that occur?

Originally Posted by exchemist

Where would the extra energy come from? You have a certain wattage of energy available from the wind, per unit area exposed to it. To extract more energy, the machine would have to intercept wind from a greater area, surely? How would that occur?

By traversing more unit areas than it otherwise would, it can collect more energy, because each area has its own energy. One proof of concept comes from sailing: if two sailboats set out from point A to reach point B downwind, the one that sails strait there with the wind to its back may get there after the one that tacks diagonally out and diagonally back. This is because the diagonally sailing one interacts with more wind and goes much faster. The other is the blackbird, but my understanding is it moves into the wind, so it ultimately only harvests energy that would come to a windmill ultimately, just at a greedier rate.

What I know is 1) that this works is counterintuitive, many smart people said the blackbird was impossible. 2) The fundamentals are there in terms of energy, if a device can be devised to capture it. The example with the sailboat gives me hope it can be done. The challenge is to optimally harness energy coming from the x axis, while traversing the y axis. The sailboat may represent the best possibility, in which case the small improvement for energy input is not worth the cost, but it may be it can be much better, I just don’t know.

Actually, let me amend part of what I just said. Maybe the blackbird design itself could work with a slow wind, it just “mows the lawn”, collecting all the wind in the column that would come to a stationary windmill in ten minutes in the course of two minutes, then moving over to the next column. I believe it said it can move into or away from the wind.