Has this hybrid tech been explored? (my idea)

[Sodemo]

One thing I thought of with all this hybrid tech was has anyone developed a wind / fan hybrid.

In my mind when a car is moving along its generating a lot of potential wind energy, so why not use that by having a wind turbine attached to the car which can spin and then generate power for the battery (which can then be in turn used for the "power").

I am not speaking about attaching windmills to the outside of the car or anything quite so bonkers, but having fans say behind the "bumper" which when wind is generated they start to spin. I was thinking of a air scoop at the front of the car which then narrows thus speeding up the airflow which would then direct itself onto a fan, or series of fans. I'd imagine a 50-70mph gust would generate a reasonable amount of power...?

It may have already been explored and then discounted or there are potential issues which would prevent it front working, but its not something ive yet seen.

[Akrapovic]

I originally read this and completely missed the "behind the bumper" comment, and jumped straight to the idea of free energy. External wind turbine generators would cause too much drag, and you wouldn't put enough energy into the battery to recover what you lost from the drag.

However, I don't know how that would apply to inboard ones. The area in front of the radiator, for example, is already draggy, so do you lose less putting them there? Is it the same loses as externally placed WTGs?

For perspective, a standard onshore wind turbine can generate 2-4MW (depending on the model, obviously). I built a simulation of wind turbine control room a few years ago and there's a formula for calculating the power output of a turbine. (here). Using a rotor diameter of 20cm (reasonable for a car?), wind speed of 50mph and a coefficiency of 0.4, I get an approximate power output of 129 watts.

But I've no idea how useful that would be in a car. Over a 100 mile drive would it generate enough to add additional miles? That's beyond my knowledge limit, so hopefully someone smarter can take this and convert it to car.

[crmalcolm]

My limited experience in this area would suggest that it would be a negative energy addition to the car.

There are a number of factors at play here - and a lot of variables - but I'll try and simplify as much as possible.

Assume that the wind direction is static, with a constant velocity, which would mean that a car (in theory) would spend as much time with a head wind as a tail wind.

In a static wind turbine, the wind passing over the blades is used to turn a generator - transferring energy from kinetic, to mechanical, to electrical. The amount of energy required to turn the blades is greater than the amount of mechanical energy at the turbine, which is also greater than the amount of electrical energy recovered. This is due to the fact that all conversions of energy are subject to some loss.

Transferring the turbine to a car, as is being suggested, means that the turbine is being moved against the air, as opposed to the air passing over the turbine. In this case there is a certain amount of mechanical energy required to driver the blades forward. The amount of energy 'generated' by the kinetic>mechanical>electrical process would be less than the amount of energy used by the electrical>mechanical process to drive the car forward.

In short, the extra drag outweighs the energy recovered.

The only potential application of this would be if the turbine was able to be deployed or withdrawn as necessary. E.g. when in a head wind the turbine may contribute additional energy to the car's systems, but in all other circumstances would be drawing energy from the car.




If you want to get a practical demonstration, it can be achieved with a pinwheel spinner like the one below.
Turn the 'blades' into the wind, and try moving it through the air at speed to turn the pinwheel. You can quickly feel that as the speed increases, the amount of drag generated is fairly substantial, before a turbine has even been added.

[ApexTurtle]

What if you eliminate the electrical conversion, eg a flywheel?

[Sodemo]

Ah ok, I guess there are reasons why this hasn’t been done and thought of by bigger minds than myself.

[Akrapovic]

Originally Posted by ApexTurtle

What if you eliminate the electrical conversion, eg a flywheel?

You lose it in mechanical resistance instead. A lot of the loss in the kinetic > electricity process is mechanical, as you're spinning bits of metal and magenets to generate the electricity.

[ApexTurtle]

Originally Posted by Akrapovic

You lose it in mechanical resistance instead.

Well you already lose that anyway right? I'm saying convert from kinetic to mechanical and then back to kinetic again when accelerating.

[Akrapovic]

Originally Posted by ApexTurtle

Well you already lose that anyway right? I'm saying convert from kinetic to mechanical and then back to kinetic again when accelerating.

The flywheel has continual lose of kinetic energy as the flywheel continues to spin and spin and spin. Imagine spinning a bike wheel - it eventually slows down. The flywheel is obviously less resistance, but it will lose it. It may not be too bad because a car will be speeding up and slowing down a lot, but it's not as efficient as storing energy for long periods of time like a battery.

It still has the added drag from the turbine blades though. It won't overcome that. If it did it'd be a free energy machine, as you'd be generating more energy than you're losing from the drag. If that was the case then the best vehicle in the world would be a giant turbine, as it'd go forever

[Tel 911S]

Originally Posted by Akrapovic

I originally read this and completely missed the "behind the bumper" comment, and jumped straight to the idea of free energy. External wind turbine generators would cause too much drag, and you wouldn't put enough energy into the battery to recover what you lost from the drag.

However, I don't know how that would apply to inboard ones. The area in front of the radiator, for example, is already draggy, so do you lose less putting them there? Is it the same loses as externally placed WTGs?

For perspective, a standard onshore wind turbine can generate 2-4MW (depending on the model, obviously). I built a simulation of wind turbine control room a few years ago and there's a formula for calculating the power output of a turbine. (here). Using a rotor diameter of 20cm (reasonable for a car?), wind speed of 50mph and a coefficiency of 0.4, I get an approximate power output of 129 watts.

But I've no idea how useful that would be in a car. Over a 100 mile drive would it generate enough to add additional miles? That's beyond my knowledge limit, so hopefully someone smarter can take this and convert it to car.

Using your figures of 129 W output , over a 100 mile at 50 MPH that would generate approx 1/4 of a Kilo Watt Hour of energy . So enough to drive a light EV , [ going steady ] about 3/4 of a mile extra .
But using the principles of energy transference , would use more energy to do it , so might lose perhaps 1&1/2 miles from the original range .

But if you look at aerodynamics , where power has to increase at a square of any wind drag increase , then the decrease in mileage might be a lot more .

Which is why car manufacturers & race car designers spend a lot of time & money just to try to find a tiny improvement in aerodynamics