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Mess with your minds: A wind powered craft going faster than a tail wind speed.

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fourfathom:

--- Quote from: electrodacus on December 11, 2021, 10:07:37 pm ---[...] small capacity energy storage and stick slip hysteresis with charge discharge cycles of many times per second. [...]
--- End quote ---

This is all so wrong...   No wonder you can't figure it out.

electrodacus:

--- Quote from: Kleinstein on December 11, 2021, 10:18:19 pm ---
I don't agree with the red part: the net power is not acting against the vehicle - power has no geometric direction. A positive net power means there is power to spare, e.g. to turn on some lights or overcome friction. So not all power needs to be send to the motor in the steady state for the 3 cases shown. If all the power is send to the motor it would accelerate the vehicle and thus no longer the steady state.

The orange part is some-how self-contradicting, or I don't understand what it should mean: if all the power is send to the motor, Pout=P_motor= Pin and thus no net power.

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Power can be negative. Think a battery being charged vs discharged. How you will differentiate between the two ? as they sure do not mean the same thing.

What will you do with the excess of generated power ? heat air ?
Yes a net positive power means in this case power available at that fixed moment in time to accelerate the vehicle from left to right (I will say that is forward) so vehicle kinetic energy will increase relative to the road/ground.
A negative power means that will decelerate the vehicle so vehicle kinetic energy relative to road/ground will decrease.

Pout is the power provided by the wind (wind treadmill in this example) FM * (w-v)  plus what you supply the motor with so Pin

electrodacus:

--- Quote from: fourfathom on December 11, 2021, 10:24:49 pm ---
--- Quote from: electrodacus on December 11, 2021, 10:07:37 pm ---[...] small capacity energy storage and stick slip hysteresis with charge discharge cycles of many times per second. [...]
--- End quote ---

This is all so wrong...   No wonder you can't figure it out.

--- End quote ---

See this video I made in slow motion (you can watch at 0.25x) and explain what you see https://odysee.com/@dacustemp:8/wheel-cart-energy-storage-slow:8

IanB:

--- Quote from: electrodacus on December 11, 2021, 10:00:43 pm ---To make it easier to replay I will post again the photo with the 3 cases

--- End quote ---

Case A: The vehicle can move to the right with zero power from the generator and zero power at the motor.

Case B: The vehicle can move to the right with any power greater than zero at the motor. Less than 1 W would be enough.

Case C: The vehicle can move to the right with a power greater than about 4 W at the motor. Since this is less than 10 W, the generator can supply it.

In each case, the pictures clearly show the cart being able to move to the right.

Kleinstein:

--- Quote from: electrodacus on December 11, 2021, 10:26:41 pm ---Pout is the power provided by the wind (wind treadmill in this example) FM * (w-v)  plus what you supply the motor with so Pin

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Ok if P_out is supposed to be the power taken from the wind, than the formula on the left are correct, just a rather strange name for the power taken from the wind. This would however also include the motor running as a generator. Anyway the case of going slower than the wind should not be at question.

However  with P_out for the power from the wind the the formula in the middle don't make much sense. P_net would be than the power direktly transfered to the vehincle (without the power from the motor). In the ideal case with 100% efficiency and no friction loss all the power taken from the wind would also end up in the vehicle, as there is no other energy sink in the steady state.

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