Altran eMOC, Electric Modular Car

[Andres125sx]

Interesting concept, a city car with add-on modules to improve range, luggage and/or passengers capacity, energy recovery and more

http://www.altran.com/hub-press/press-r ... uture.html




This made me think about the wind turbines, this is something I´ve been thinking about many times.... is a wind turbine worth? or the added drag is not worth the energy generated?

[tomislavp4]

The energy generated but the turbines will be less then the energy needed to overcome their drag. Although you can make the foldable so they can be used for charging while parked. I don't think this will take off, too complicated structurally. It will have bunch of problems and will end up costing quite more then it should.

[Andres125sx]

The energy generated by the turbines will be less then the energy needed to overcome their drag.

Are you sure about this? Agree with the rest of your post, but not sure about this

I think it must be a factor of speed, under 100km/h drag is not a big issue, and this car is limited to 80km/h, so I´m not that sure. For higher speeds I´m almost sure that will be true, but at lower speeds...

What energy is needed to overcome that increased drag at 60km/h? Without any knonledge at the respect, I´d say very little, but a wind turbine, even this small, spinning with a wind of 60km/h can generate some energy.... question is if more or less than the needed to overcome that drag

As I say I don´t have technical knownledge at the respect, but intuitively I´d say at low speeds it may be worth

[flynfrog]

The energy generated by the turbines will be less then the energy needed to overcome their drag.

Are you sure about this? Agree with the rest of your post, but not sure about this

I think it must be a factor of speed, under 100km/h drag is not a big issue, and this car is limited to 80km/h, so I´m not that sure. For higher speeds I´m almost sure that will be true, but at lower speeds...

What energy is needed to overcome that increased drag at 60km/h? Without any knonledge at the respect, I´d say very little, but a wind turbine, even this small, spinning with a wind of 60km/h can generate some energy.... question is if more or less than the needed to overcome that drag

As I say I don´t have technical knownledge at the respect, but intuitively I´d say at low speeds it may be worth

why not just added a 5th wheel on the ground hooked to a generator less areo drag

[xxChrisxx]

The energy generated by the turbines will be less then the energy needed to overcome their drag.

Are you sure about this? Agree with the rest of your post, but not sure about this

I think it must be a factor of speed, under 100km/h drag is not a big issue, and this car is limited to 80km/h, so I´m not that sure. For higher speeds I´m almost sure that will be true, but at lower speeds...

Wind turbines work because they are static, and the wind passes over them. The energy is provided by the wind. When you are 'creating' the wind by pushing the turbine through the air. You are providing the power to do this.

And as we all know from the laws of thermodynamics, you can't get out more than you put in. So an exposed turbine will always be less efficient than not having it at all. The laws of physics apply at all speeds.

[andylaurence]

Whilst it's true that wind generated by traveling forwards is never going to help, there is still wind. A sailing boat can travel upwind, albeit not directly. It could well be that a wind generator on the car would be advantageous in crosswinds.

[Andres125sx]

Wind turbines work because they are static, and the wind passes over them. The energy is provided by the wind. When you are 'creating' the wind by pushing the turbine through the air. You are providing the power to do this.

And as we all know from the laws of thermodynamics, you can't get out more than you put in. So an exposed turbine will always be less efficient than not having it at all. The laws of physics apply at all speeds.

You´re assuming you´re moving the car to create wind and use that wind to generate energy, and that´s wrong. The car is moving anycase, and it weights around a ton, that´s what is determining the power requirements, not the wind turbine The added drag of a small wind turbine will change the power needs almost nothing

I guess most of you have seen graphs about drag and petrol consumption, and it´s from 100-110km/h when drag becomes a crucial factor and consumption start increasing exponentially. Below that speed drag is important but not so determining. Since a car has a lot of drag by itself, does a small wind turbine really change the power requirements of the car at those speeds where drag is not that crucial?

Does anyone of you have any real analysis apart from funny pictures? If you think engineers who designed this are complete idiots ok, but I tend to think engineers are usually more reasonable than forum members, even when many of us are engineers too, so to put those engineers down please provide something more reasonable, if you can

[Cold Fussion]

Instead asking for analysis of why it wouldn't work, why don't you provide some analysis as to why it would work.

[flynfrog]

maybe try a physics class? I think the pictures sums up quite well why it wont work.

There are no engineers involved with that car there are some industrial design students and a marketing guy. Maybe some guy to throw together some cad models to make pretty pictures with.


If you want wind turbines to work make them deployable after the car stops moving. At speed the majority of your drag is going to be aero and its exponential. Trying to get a tiny amount of side wind without causing more drag is next to impossible. You are going to add frontal area either way.

[Andres125sx]

Instead asking for analysis of why it wouldn't work, why don't you provide some analysis as to why it would work.

From the OP:

is a wind turbine worth? or the added drag is not worth the energy generated?

Maybe I was wrong expecting something more technical than a mocking picture from a technical forum....

[Andres125sx]

There are no engineers involved with that car there are some industrial design students and a marketing guy. Maybe some guy to throw together some cad models to make pretty pictures with.

So no engineers involved on a car development, bold statement if you ask me...

If someone is willing to reply in a more technical way, this is what cause me some doubt

You´re assuming you´re moving the car to create wind and use that wind to generate energy, and that´s wrong. The car is moving anycase, and it weights around a ton, that´s what is determining the power requirements, not the wind turbine. The added drag of a small wind turbine will change the power needs almost nothing

You´re not moving a wind turbine, you´re moving a car wich has lots of drag and inertia with or without a wind turbine, maybe the added drag of a wind turbine is negligible because you need a lot of power to move the car anycase

[flynfrog]

Andre I'm not sure how to reply. You don't understand even enough of the basics here.

Thermodynamics says we can't get out more than we put in. So lets create a car out of magic that has zero drag. So to propel it to 100km hr it takes 0 energy. Now lets say we have a wind turbine that in a 100km wind produces 100J of energy. This means that at 100% efficiency the wind turbine could propel itself down the road but only create enough power to propel it no extra. Since we know that a wind turbine is not 100% and is in reality around 18% efficient there is no way putting one on top of a car isn't adding a bunch of drag for no gain.

If this doesn't make sense take simpler example of an electric motor mechanically coupled to a generator. Then hook the wires from the generator back into motor. This in essence what you are proposing but with a terribly inefficient mechanical coupling system.

Does this help at all?

[Andres125sx]

Thermodynamics says we can't get out more than we put in. So lets create a car out of magic that has zero drag.

Wrong start

Cars have drag, that´s the main point. Since cars have drag and weight, you need some energy to move it, and it´s not negligible, you need a good amount to move a car. There my doubt, since you need a good amount of energy to move the car.... does the little drag of the wind turbine really change the power demand?

Considering it´s limited to 80km/h I guess drag will probably be the less important factor to move the car, it´s the weight what determines how much power you need to move it, so maybe (and that´s my question) even with the turbine it still is weight what determines how much power you need to move it and it does not change with or without turbine

Remember it´s a city car, it will not travel at constant speed for too long, it will be accelerating and braking constantly, so maybe that drag is negligible

Thanks for trying anycase

[Greg Locock]

Although the idea of a modular car seems appealing it invariably weighs more than the equivalent single purpose design, and one big question nobody ever really answers is what do you do with the spare modules in your garage- they are enormous, heavy, and fragile.

Solar cells on a normal size and weight car are a waste of time and money, put them on your garage roof and use them to charge the battery.

I'm amazed somebody on a supposedly technical forum doesn't understand enough physics to know why the turbine on the roof idea is bad, at least in still air. Basically you are proposing a perpetual motion machine. If the wind is blowing things are more complex.

[flynfrog]

Thermodynamics says we can't get out more than we put in. So lets create a car out of magic that has zero drag.

Wrong start

Cars have drag, that´s the main point. Since cars have drag and weight, you need some energy to move it, and it´s not negligible, you need a good amount to move a car. There my doubt, since you need a good amount of energy to move the car.... does the little drag of the wind turbine really change the power demand?

Considering it´s limited to 80km/h I guess drag will probably be the less important factor to move the car, it´s the weight what determines how much power you need to move it, so maybe (and that´s my question) even with the turbine it still is weight what determines how much power you need to move it and it does not change with or without turbine

Remember it´s a city car, it will not travel at constant speed for too long, it will be accelerating and braking constantly, so maybe that drag is negligible

Thanks for trying anycase

Maybe try graduating high school physics before continuing the discussion then? This is day one stuff mate. Even if the car zero drag the wind turbine will not provide more power than it takes to drive it along.