Altran eMOC, Electric Modular Car

[Andres125sx]

Basically you are proposing a perpetual motion machine

No I´m not. First this is not my project, but from Altran. Second it´s not a perpetual motion machine, it is a car.

Maybe you think regenerative brakes are a proposal for a perpetual motion machine too

As explained three times with this one, the questions raises because of the high power used on a car and usually wasted unefficiently, wich maybe could be recovered partially as regenerative brakes do. Considering the high power demands of a car to accelerate and brake constantly on a city, and the low drag of a small turbine, my question wich remains unaswered even when I´m between prominent figures, is if a car power demand to accelerate is determined mainly due to its weight (drag is not relevant), what could make this idea doable. For constant speed things are different, but this is a city car


I don´t think the question is so stupid to only deserve mocking replies....

I'm amazed somebody on a supposedly technical forum doesn't understand enough physics to know why

Maybe try graduating high school physics before continuing the discussion then?

And I´m construction engineer, btw, maybe you guys are so obsesed with the perpetual motion machine you can´t think a bit further

[Greg Locock]

I'm not focussed on the PM issue, i also pointed out the ludicrousness of the main concept.

[sgth0mas]

Ill agree that the windturbines will never produce more than they consume in increased drag.

Windmills of that size would increase both the frontal area and the coefficient of drag. While they may seem somewhat compact, they probably add at least 15-20% if not more to the frontal area. They will further increase the coefficient of drag by making the shape less efficient and creating turbulent air which increases the pressure drop from front to back. Your net drag increase will probably be at least 25-50%.

My guess is that those wind turbines are for use when parked.

That car also hasnt been truly engineered yet, its just some crude renders. Maybe its to peak interest or to seek investors, or just a study to help keep the companies name out there.

You wont see anyone calculate it because there are too many variables to even know how efficiently the windtrubine will behave, much less compare to the increased energy consumption from drag.

Im a mechanical engineer btw if it makes you feel better. Ive seen plenty of product renders and can spot whats an actual designed product or just a high level concept.

[sgth0mas]

Regenerative brakes should not be compared to this concept as the energy balance is different. There is a very small weight penalty from regenerative braking, not a massive drag penalty. Braking will always occur, and that energy can either be lost to a lot of heat or harvested by a generator.

[flynfrog]

You wont see anyone calculate it because there are too many variables to even know how efficiently the windtrubine will behave, much less compare to the increased energy consumption from drag.

The math is pretty easy. At best a modern wind turbine is 18% efficient so for every 18 watts you produce you will burn 82 watts to get them.

[sgth0mas]

You wont see anyone calculate it because there are too many variables to even know how efficiently the windtrubine will behave, much less compare to the increased energy consumption from drag.

The math is pretty easy. At best a modern wind turbine is 18% efficient so for every 18 watts you produce you will burn 82 watts to get them.

its not that easy, turbines are more efficient (edit: some turbines, not all and surely not one on top of a car) than that and it depends on much too many other factors to calculate a true based drag trade off. We all know its a net loss, but to show him mathematically will involve too many other specs.

[sgth0mas]

To elaborate, the trade off equation would not be linear or first order. It will be highly dependent on speed, environment, the aerodynamic properties of the car, wind turbine design and a few other factors.

[flynfrog]

You wont see anyone calculate it because there are too many variables to even know how efficiently the windtrubine will behave, much less compare to the increased energy consumption from drag.

The math is pretty easy. At best a modern wind turbine is 18% efficient so for every 18 watts you produce you will burn 82 watts to get them.

its not that easy, turbines are more efficient (edit: some turbines, not all and surely not one on top of a car) than that and it depends on much too many other factors to calculate a true based drag trade off. We all know its a net loss, but to show him mathematically will involve too many other specs.

very true but it doesn't take a complicated analysis to show that a net loss is going to occur as soon as you start to move the turbine.

[dmjunqueira]

Sorry for going off-topic...This is just a comedy video about how some companies create this incredible ideas...Please be aware: Don't watch if you don't want to waste time.

This wind turbine idea just reminds me of this video:

[sgth0mas]

...

The math is pretty easy. At best a modern wind turbine is 18% efficient so for every 18 watts you produce you will burn 82 watts to get them.

its not that easy, turbines are more efficient (edit: some turbines, not all and surely not one on top of a car) than that and it depends on much too many other factors to calculate a true based drag trade off. We all know its a net loss, but to show him mathematically will involve too many other specs.

very true but it doesn't take a complicated analysis to show that a net loss is going to occur as soon as you start to move the turbine.

I agree and underatand the concepts you mentioned. I think most of us do actually but some havent been familiarized with the law of conservation of energy. I think the problem is that andres truly doesnt know and needs to see the math to understand the energy balance. While you already proved how much energy it will take based on efficiency, the second half of that is proving that increasing the drag by so much requires the car to expend this much more energy To balance out.

[Andres125sx]

Thanks sgth0mas

What I don´t know is how does affect drag to power consumption. I was wondering if at slow speed it may not affect too much, if the energy needed to move the weight of a car may do drag negligible. At high speed obviously drag becomes a critical factor, but I was not sure about what happens at slow speeds

So basically the concept would only be worth when parked, or maybe with crosswinds, thanks for a constructive reply =D>

[Andres125sx]

Sorry for going off-topic...This is just a comedy video about how some companies create this incredible ideas...Please be aware: Don't watch if you don't want to waste time.

This wind turbine idea just reminds me of this video:
https://www.youtube.com/watch?v=BKorP55Aqvg

That´s fun, remind me some meetings I´ve had when I was project manager

[autogyro]

We looked at the trailer battery pack for extended range a few years ago.
It was regulations for hire vehicles that prevented development.

The small wind turbines would not generate sufficient power to be worthwhile from crosswinds and would be to cumbersome and dangerous to use when parked, unless to augment solar panels on something like a camper van.

Regen braking is better but again only works in an electric/hybrid vehicle efficiently for short stop start driving.
If an electric/hybrid vehicle is used mainly on long main roads it is more efficient to coast for deceleration which results in a longer range.

Interestingly the use of turbines/compressors in aircraft engines for the capture of electrical energy would be useful on decent.
Aircraft do not have mechanical braking of course and are highly efficient aerodynamically.
However this depends on the development of hybrid/all electric aircraft propulsion systems.
With current engines it would be too bulky/heavy and dangerous because it compromises the engines combustion process.

[J.A.W.]

Yeah, A-G, Nazi aircraft used such devices, i.e. - to power the 'Jericho Trumpet' siren - on diving Stukas..

[Andres125sx]

So now expressing opinions and asking questions deserve downvotes... Incorrect should be applied when someone do an incorrect assertion, not when someone say openly he does not have the necessary knowledge about the subject and is just asking for technical answers

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

Specially when there are two pages after that reply (it is my second post in this thread) explaining the reasons I was wrong. That´s a discussion after all, on a discussion forum...