I was thinking about ways in which wind turbines could be coupled with other forms of generating energy and came across a rather ugly and unaesthetic thought -attaching a (miniaturized) vertical axis wind turbine to a car, not unlike the antennas that could be detachable and stuck into the air which was a standard accessory until about 10 or so years ago(?).
The key reason why I think it would work is because as a car with such a wind turbine attached moves against the air as it travels forward, i.e. at a speed of 40 mph, that would be equivalent (in terms of the potential power extractable from the wind, all other factors unchanged) to a (stationary) wind turbine with a 40 mph wind blowing toward it, which is a very high wind speed; high wind speeds are a significant factor in the viability of wind power since the potential power extractable from wind is a cubic function of the wind speed, provided that the wind’s direction is held constant. (But the fact that cars generally move significantly faster than the ambient wind speed at ground level means that the direction of the car would be the predominant factor in the overall wind direction “vector”(??))
Could such a car+wind turbine combination be used to generate electrical energy, as a normal wind turbine does, which could then of course recharge a battery which would then act as an electric motor, driving the wheels of the car as an electric car/hybrid car does?
If such a concept is physically viable, and economically feasible either in the near or distant future, would you (and your opinion of consumer tastes in general) consider the energy efficiency benefits to outweigh the ugliness of such a design?
wind powered car that goes faster then the wind powering it. It seems to break some fundamental physics laws, but apparently not…since it does actually work.
But to the OP, you can’t get more energy back that way, similar to the claims that you can get significantly more gas mileage by using electrolysis to generate hydrogen to power your car (hint - the electricity ultimately comes from fuel burned in the engine, maybe 10% efficient overall (engine + alternator + electrolysis), same for using a wind turbine).
While the following is impractical due to the costs and extra weight, I thought the OP might like to know that if the turbine only acted when braking, you would be able to recover some of the energy that is normally lost every time we touch the brake pedal.
Since the power to turn the turbine is a result of engine powr, why not just tap off the alternator?
Understand the conservation of energy law, the laws of thermodynamics. the energy to turn the turbine is power from the engine. Mount a vertical turbine (or a big flat sheet of plywood) on the top of the car, and teh engine has to work extra harder to drive the same speed with added drag. It uses more fuel, a lot more that the amount of energy recouped by the action of the turbine.
And to add to cooky173’s note - you could have a wind turbine that charged a battery in the car when the car was parked. The car can run on the battery (like a hybrid or electric car) and the wind turbine has to be very light and very foldable - i.e. it needs to be like the telescoping antenna (engineering nightmare) so that it creates no drag during normal use.
Noooo!! That’s not my point! I was suggesting the following:
-assume that the wind speed is negligible (relative to the ground, of course)
-now, assume that the car is moving at 40 mph in a straight line (relative to the ground again).
v(x, y) being defined as velocity of x in reference frame y, y being a one-dimensional reference frame for simplicity
-also, ||v|(x, y)|| being defined as speed of x in reference frame y (speed of x “relative to y” ), where || || denotes absolute value.
By simple rules of conversion of velocities across reference frames (“Galilean transformations” is the technical term I believe),
Note: ||v(air, ground)|| is simply wind speed (as is reported by meteorologists as well as what is meant in ‘everyday usage’)
Since the wind turbine is attached to the car, “it” moves as the same speed as the car does, with respect to (any) reference frame, but pertinently with respect to the air. So the following “equation” holds:
(Eq 2) ||v(car, air)|| = ||v(turbine, air)||.
Combining (Eq 1) and (Eq 2) trivially yields:
(Eq 3) ||v(turbine, air)|| = 40 mph
For any object x moving at a velocity v in a one dimensional reference frame, with a fixed ‘positive’ and ‘negative’ directionality, we have that
(Eq 4) v(x, y) = - v(y, x). and trivially, from this, we have:
(Eq 5) ||v(x, y)|| = ||v(y, x)||
For example, when x is a person running the 100 m race and y is the straight portion of the track, v(person, track) is clearly equal to the opposite of v(track, person)…we usually don’t think of v(track, person) since this treats the person as the ‘stationary frame’ and the track moving with respect to it.
Letting x in (Eq 5) stand for turbine, and y for air, we have
(Eq 6) ||v(turbine, air)|| = ||v(air, turbine)|| , and equations (Eq 3) and (Eq 6) combined trivially yield:
(Eq 7) ||v(air, turbine)|| = 40 mph.
+++++++++++++++++++++++++++++++++++++++
Now considering the simple case where we have a 40 mph wind (in an arbitrary but fixed/steady direction, with a turbine that faces the wind in the most favorable direction, in terms of power output), hitting a turbine that is, as ‘normally,’ fixed to solid ground, we have that
(Eq 7) and (Eq 8) each are the final respective results for the speeds of the air with respect to wind turbines, the former being one in which there is zero wind speed with respect to the ground/Earth (a ‘perfectly’ calm day, i.e.), and the latter being one in which there is 40 mph wind speed with respect to the ground/Earth.
The identity of (Eq 7) and (Eq 8) shows that a wind turbine moving at 40 mph with zero ambient wind (‘air’) and wind (‘air’) moving at 40 mph with respect to a ‘normal’, fixed to the ground wind turbine both result in the same kinematic result, namely, that:
||v(air, turbine)|| = 40 mph
Is it necessary for a motor to drive a ‘normal’ wind turbine? No! The force of the wind itself, which is ‘free’, drives the turbine and thus generates electrical energy. Since this scenario is kinematically equivalent to the normal functioning of a wind turbine that’s fixed to the ground, the car’s engine (motor) itself isn’t driving the wind turbine - on the contrary, it is the air/wind hitting the attached turbine itself as the car moves through the air that drives the turbine and thus (??) generates electrical energy.
This generated electrical energy would, in a sense, come from the motor that drives the engine of the car, but the motor wouldn’t be directly driving the turbine blade. Instead, the motor/engine enables the car to move forward, causing the wind turbine attached to the car to also move forward ‘against the air’, which in turn drives the rotor (again, since a wind turbine moving INTO air is equivalent to air moving into [the blades] of a wind turbine in terms of kinematics).
Perhaps most importantly, even the added cost of friction due to the blades and increased weight could be “scalable” at higher speeds, since the friction force due to air at subsonic speeds is generally a quadratic function of speed…and since the power of a force on an entity moving at velocity v is the dot product of that force and that velocity v, P(overcome friction) = (kv^2) . (v) = kv^3, with really deformed objects as the car with wind turbine attached having larger k values but generally NOT a larger power of v. The power output of a wind turbine also being a cubic function of the velocity, so at best, such a contraption could cancel out much of the friction generated, the clear downside being that the turbine itself is responsible for much of that friction…(?? - whole paragraph)
I’ll write more/respond to all posts the best I can…sorry about the late response and poor grammar/styling, I need to go to sleep soon I think…
Dude. Driving the turbine through the air creates drag which requires engine power to overcome. That additional engine power would be more than what you gain from the turbine.
Yes, everything you have shown here is true, but trivial. Nobody would disagree that the 40 mph wind incident on the turbine is the same whether it is a result of air movement over ground or the turbine moving through still air.
The two turbines will spin in the same way and generate the same amount of electricity.
The difference is that the air movement over ground costs nothing, so that any energy produced by the turbine is a gain, whereas the movement of the turbine through the air requires more energy than the turbine can generate, giving a net energy loss.
How does that work? It looks like it’s the opposite of the OP’s example in that it is going down wind. My best guess is that there is more energy available from the wind hitting the surface of the blades then is necessary to propel the car at wind speed, and some of that is being used to turn the wheels. Combine that with the reduced drag from going downwind. Still seems counter intuitive though.
Not that they are not “sailing” by tacking into the wind.
Yes, it could. But unless you have another energy source to make up the net loss, it will eventually run down.
It could be described as a simple system, like this. Suppose you have a fan, bolted to a table, facing a wind generator, also bolted to the table. The fan is powered by a battery, and the wind generator charges the same battery.
Turn on the fan, the wind generator starts to spin and feed electricity back to the battery, which turns the fan, etc.
Since nothing is 100% efficient (those pesky No Free Lunch laws), the battery will never get charged with as much energy as you need to keep turning the fan. Eventually, like all perpetual motion devices, it will run down and stop.
Your scheme to mount something on a car is exactly this principle. Instead of the battery turning the fan, you are moving the turbine thru the air. Same outcome.
You’re probably thinking about a Ram Air Turbine (RAT). If this is deployed, no one cares about efficiency; they just want to land and be alive to tell the tale. The forward motion of the plane is what powers the unit, but it would be stupid to use it during normal flight for the same reasons as given in this thread (a net loss).
Something I have wondered about along the same lines is using the heat from the exhaust to wind up thermal springs like we use to use on the old chokes and then using the torque stored in the springs to help drive the car. Only problem I see with this is the exhaust would have to constantly switch it’s route to allow the springs to contract and cool. It would likely add too much weight to a car to pay for itself.
A stationary engine I would think that might be used to produce electricity could take advantage of a lot of the loses we see in car engine making them far more efficient. It could preheat water to drive a steam engine, eliminating a water pump and fan. It could also use the exhaust for preheating water.
