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Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
Naej:
--- Quote from: electrodacus on July 07, 2022, 10:06:05 pm ---The paper seems to concentrate on direct upwind witch uses different type of energy storage and can be debunked even easier.
--- End quote ---
Perhaps you should apply the wind turbine power equation now that it is a… wind turbine?
electrodacus:
--- Quote from: Naej on July 07, 2022, 11:35:33 pm ---
--- Quote from: electrodacus on July 07, 2022, 10:06:05 pm ---The paper seems to concentrate on direct upwind witch uses different type of energy storage and can be debunked even easier.
--- End quote ---
Perhaps you should apply the wind turbine power equation now that it is a… wind turbine?
--- End quote ---
Yes it is a wind turbine and yes that equation will apply for a theoretical ideal wind turbine and by ideal I mean 100% efficient not even Betz limit is applied.
But just to keep the vehicle in place you need all that generated power applied to the wheels.
So if wind turbine generates 1000W you need to apply all that to the wheels in order for the vehicle to remain stationary (assuming wheels have enough grip to handle that).
You can think at wind balls hitting the vehicle body (includes the propeller/turbine blades) and so for a 1m2 area 6m/s wind you have the equivalent of 6 x 1.2kg balls hitting the vehicle every second and balls speed is 6m/s and are spaced 1m apart.
Now when the ball hits the vehicle it will transfer his kinetic energy to vehicle.
So for this case direct upwind say vehicle is 100kg and it is stationary then when one ball hits the ball transfers the kinetic energy to vehicle and that is 0.5 * 1.2kg * 62 = 21.6Ws
So now vehicle speed after the first ball hit will be sqrt(21.6Ws/(0.5*100kg)) = 0.657m/s in the same direction that ball was moving.
Now to get back to initial position and zero speed you will need to take all this 21.6Ws you got in ideal case form wind and apply to the wheels.
So ideal case you can stay in the same place and can not move upwind without storing the energy.
Same ball hitting the vehicle is valid for direct downwind version so when vehicle speed matches ball speed no ball can hit the vehicle and when vehicle is above ball speed the vehicle hits the ball instead of the other way around.
The reality is that each 1.2kg ball is made of a huge number of air molecules Nitrogen and Oxygen mostly but the physics is exactly the same
Naej:
--- Quote from: electrodacus on July 08, 2022, 12:01:45 am ---Yes it is a wind turbine and yes that equation will apply for a theoretical ideal wind turbine and by ideal I mean 100% efficient not even Betz limit is applied.
But just to keep the vehicle in place you need all that generated power applied to the wheels.
So if wind turbine generates 1000W you need to apply all that to the wheels in order for the vehicle to remain stationary (assuming wheels have enough grip to handle that).
--- End quote ---
Damn 1 horse power in a car? It does not sound impossible to me.
And why would you want the car to remain stationary?
You seem to believe that energy in air flowing through a turbine/propeller = mechanical energy given to the car.
This is COMPLETELY WRONG, for example a wind turbine stays stationary.
The force applied on the turbine by the air can be computed (cf. my posts above) and then you multiply by the speed of the car/turbine to get the mechanical power.
If you put a propeller on a 1000W engine, it does NOT mean you'll get 1000W of mechanical power out of it. If, for example, you put the brakes on your aircraft it won't move and the kinetic energy is equal to 0, and you get 0W.
electrodacus:
--- Quote from: Naej on July 08, 2022, 12:28:48 am ---Damn 1 horse power in a car? It does not sound impossible to me.
And why would you want the car to remain stationary?
You seem to believe that energy in air flowing through a turbine/propeller = mechanical energy given to the car.
This is COMPLETELY WRONG, for example a wind turbine stays stationary.
The force applied on the turbine by the air can be computed (cf. my posts above) and then you multiply by the speed of the car/turbine to get the mechanical power.
If you put a propeller on a 1000W engine, it does NOT mean you'll get 1000W of mechanical power out of it. If, for example, you put the brakes on your aircraft it won't move and the kinetic energy is equal to 0, and you get 0W.
--- End quote ---
You want the car to move against wind direction and the best it can do without energy storage is to stay in place/stationary.
A 40% efficient wind turbine will act as a sail with area equal with 40% of the swept area of the rotor.
So say swept area of the turbine is 10m2 it will act as a 4m2 sail as wind speed after the turbine will be lower.
So if you install such a wind turbine on your direct upwind vehicle and wind speed is say again a fairly strong 10m/s then your turbine will output
0.5 * 1.2 * 10 * 103 * 0.4 = 2400W
But that will also result in a force pushing the vehicle in the wind direction (you want to drive against the wind direction as it is an upwind vehicle) and just to cancel that you need to use all those 2400W you produced.
In order to advance even at infinitesimally small speed against wind direction you need more than 2400W.
Think about how much power will a vehicle with 10m2 projected frontal area and a 0.4 coefficient of drag will need to travel at 10m/s
Equation for that will be
0.5 * 1.2 * 10 * 103 * 0.4 = 2400W
If this seems familiar it is because is the exact same.
It is irrelevant if a vehicle drives at 20m/s with no wind or travels at 5m/s with a 15m/s headwind it will need the same power to deal with air friction.
Naej:
--- Quote from: electrodacus on July 08, 2022, 12:46:09 am ---But that will also result in a force pushing the vehicle in the wind direction (you want to drive against the wind direction as it is an upwind vehicle) and just to cancel that you need to use all those 2400W you produced.
In order to advance even at infinitesimally small speed against wind direction you need more than 2400W.
--- End quote ---
It appears you don't understand the difference between force and power. Check these out in high school physics books.
For example, the concrete at the bottom of a wind turbine produces 0 W (as most concrete) and can "cancel" the 3MW produced.
--- Quote from: electrodacus on July 08, 2022, 12:46:09 am ---Think about how much power will a vehicle with 10m2 projected frontal area and a 0.4 coefficient of drag will need to travel at 10m/s
Equation for that will be
0.5 * 1.2 * 10 * 103 * 0.4 = 2400W
If this seems familiar it is because is the exact same.
It is irrelevant if a vehicle drives at 20m/s with no wind or travels at 5m/s with a 15m/s headwind it will need the same power to deal with air friction.
--- End quote ---
Lol and what if the "coefficient of drag" is 0.1 ?
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