Wind Turbines on Cars: Benefits & Challenges

[microsoftMan]

Hello.

Let me make something clear right away, I don't think perpetual motion is possible. However, whenever I look into wind-turbines/cars I find forums bashing some young person for asking why we don't strap a windmill to the top of our cars. Obviously that wouldn't be an efficient way of powering the car because it would create drag.

My question is this:

Why could a turbine-type device not be implemented somewhere on the car where extra drag is needed? I have two examples of needed drag in mind:

A. Spoilers. Some cars already have spoilers in place to help push the car down against the pavement. Some cars even have the spoilers underneath the cars. It seems we could develop a spoiler-sized device that spins as wind/air rushes past and also provides enough drag to accomplish the task of a typical car spoiler.

B. Braking. We waste so much energy braking. As I understand it some hybrid cars capture the energy in the form of heat but this doesn't seem very effective. Not to mention the wear and tear on the brake pads/rotors. If a turbine would significantly increase drag on a car it seems it would be perfect for slowing the car down. Perhaps a turbine could be retractable and only engage when slowing to a stop.

Alternatively a passageway for air travel could be opened during these stopping periods and the traveling air could be routed through a wind turbine-type device.

Well what do you think? Has anybody actually experimented with this? I know wind-powered vehicles exist and have reached astonishing speeds. It seems that some of that technology should have worked its way into the automotive world. I also wonder about using the kinetic energy of the spinning axis' to turn a generator during braking. Is it simply the wait of additional tech will often outweigh any benefit that is seen from it? I'm sure concerns over complexity come into play as well.

 

[Unrest]

A. Spoilers. Some cars already have spoilers in place to help push the car down against the

Most of the spoilers aren't there for traction (unless it's F1). Not sure if they actually take energy out of the vehicle's motion either. I think they're there to reduce drag.

B. Braking. We waste so much energy braking. As I understand it some hybrid cars capture the energy in the form of heat but this doesn't seem very effective. Not to mention the

Hybrids like Prius do it electrically with generators, not thermally, so pretty efficient and no brake pad wear. Will certainly be more efficient than any wind turbine (Fritz' law?) It's enough to slow the car so no need for anything else.

Well what do you think? Has anybody actually experimented with this? I know wind-powered vehicles exist and have reached astonishing speeds. It seems that some of that

Commercial aircraft actually have these (ram air turbine) to provide emergency power in case the generators fail.

A whole different issue, however is taking energy from the natural wind, not the vehicle's motion. Like how those kite buggy things work.

 

[boneh3ad]

Commercial aircraft actually have these (ram air turbine) to provide emergency power in case the generators fail.

I think you misunderstand the purpose of the APU. It isn't to provide power should the "generators" fail. In flight, the generators are the engines. If they fail, you have much bigger problems on your hands than no power to read your book or keep the cabin warm.

The APU is used when the plane is on the ground at the gate and doesn't have its engines on to generate power.

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As for the original question in the thread, it wouldn't be efficient. If you actually sat down and did the math, I highly suspect that you would find that what you use in extra fuel to power the car through the drag would more than exceed the benefit of generating power through a wind turbine.

 

[microsoftMan]

I think you misunderstand the purpose of the APU. It isn't to provide power should the "generators" fail. In flight, the generators are the engines. If they fail, you have much bigger problems on your hands than no power to read your book or keep the cabin warm.

The APU is used when the plane is on the ground at the gate and doesn't have its engines on to generate power.

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As for the original question in the thread, it wouldn't be efficient. If you actually sat down and did the math, I highly suspect that you would find that what you use in extra fuel to power the car through the drag would more than exceed the benefit of generating power through a wind turbine.

I don't think he misunderstood. In crop dusters for example the pump for the plane's auxiliary systems is driven entirely by the ram air jet.

The reason they do that is because it would add too much complication and risk of failure to tie the auxilary systems into the main engine.

You say it is inefficient and act like you did the math but I wouldn't say I'm entirely convinced it would be useless just because you say so.

I will look into the hybrid brakes some more. Thanks for the feedback.

 

[Unrest]

I think you misunderstand the purpose of the APU. It isn't to

Not the APU. I'm referring to a wind turbine that's for emergency power.

did the math, I highly suspect that you would find that what you use in extra fuel to power the car through the drag would more than exceed the benefit of generating power through a wind turbine.

Certainly. The OP mentioned that and is looking for ways around it.

 

[boneh3ad]

Not the APU. I'm referring to a wind turbine that's for emergency power.

It seems that you are correct. My apologies.

However, the distinction between this and what the OP is proposing is that the ram air EPU is not used to make the overall vehicle more efficient.

Certainly. The OP mentioned that and is looking for ways around it.

You say it is inefficient and act like you did the math but I wouldn't say I'm entirely convinced it would be useless just because you say so.

I certainly didn't do the math. That would take a lot of computer time on CFD codes and the like and most likely months to do that math. However, look at it this way:

In order for a wind turbine to generate enough power to make up for the drag created by it and produce a little extra power for net benefit, that would mean that in theory, you could just cover your plane in wind turbines, get up to speed using a jet engine and then shut your engines off and let those wind turbines power your plane. Clearly this isn't possible unless you are flying a glider and don't have a need to fly level.

It is simply thermodynamics. You can't get out of the system more than you put in, and you can't pull energy out of nowhere.

 

[xxChrisxx]

Not this again, there have been millions of threads on this exact subject. Please feel free to search for them. As you say they create drag, so you can't use them when the engine is working or your just fighting yourself. Because you aren't having wind flowing past the turbine, you are pushing the turbine through static air.

Spoilers are basically inverted wings, they are there to create downforce (not drag) or to be performance neutral but for cosmetic reasons. Wings don't function if they are spinning. Drag is the last thing you want on a car. This is why designers for race teams spend so long optimizing wings for lift to drag ratio.

Regenerative braking doesn't actually use the brakes, the electric motors act like generators. So what you get is the equivalent of engine braking. Basically:

It seems that some of that technology should have worked its way into the automotive world. I also wonder about using the kinetic energy of the spinning axis' to turn a generator during braking.

this.Wind powered turbines would work on cars if you could control when the air flowed to them (with a ducting system) only when the engine was on overrun. However gains are so small because you can only package a tiny turbine in something the size of a car vs the increase in complexity that it really isn't worth bothering with. That's the reason why it's not been done commercially.

More gains can be made from making a less draggy car or using a turbo and downsizing the engine, which is why you are starting to see so many cars with with the Kamm tail design and lots of cars with turbos.

 

[microsoftMan]

Not this again, there have been millions of threads on this exact subject. Please feel free to search for them. As you say they create drag, so you can't use them when the engine is working or your just fighting yourself. Because you aren't having wind flowing past the turbine, you are pushing the turbine through static air.

Spoilers are basically inverted wings, they are there to create downforce (not drag) or to be performance neutral but for cosmetic reasons. Wings don't function if they are spinning. Drag is the last thing you want on a car. This is why designers for race teams spend so long optimizing wings for lift to drag ratio.

Regenerative braking doesn't actually use the brakes, the electric motors act like generators. So what you get is the equivalent of engine braking. Basically:

this.


Wind powered turbines would work on cars if you could control when the air flowed to them (with a ducting system) only when the engine was on overrun. However gains are so small because you can only package a tiny turbine in something the size of a car vs the increase in complexity that it really isn't worth bothering with. That's the reason why it's not been done commercially.

More gains can be made from making a less draggy car or using a turbo and downsizing the engine, which is why you are starting to see so many cars with with the Kamm tail design and lots of cars with turbos.

I don't know you, but I hate your attitude.

Have an open mind when reading someone's questions. I mean why not? What if I was just a kid? For all you know your close-mindedness would turn me away from science and invention. Furthermore I know that there have been a cornucopia of other threads on this subject just on this site - searching for 'wind turbine on car' brought me to a thread started by a much younger individual who was just curious if it might work (and of course you bashed him from all angles and I don't think he even bothered responding, let alone learning anything or becoming more interested in physics).

But after demeaning my question, at least you basically said that it would be possible through ducting to allow some of the air through a turbine during braking and 'overrun' (not sure what you mean by overrun). Which is what I had asked. And then you confirmed my suspicion that it would probably add too much complication to the internals. That is an excellent point about the turbos that are popping up all around the car market. I suppose ten years ago though, turbos were too complicated to be added to cars. Perhaps in another ten years when gas prices are exponentially higher my idea will have more merit.


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On the other hand I can see how my spoiler idea has little merit. It is true most spoilers do resemble a wing of sorts and are going to be much more aerodynamic than I was thinking they were in my imagination.

 

[RandomGuy88]

I would suspect that even if you were able to duct the air to the turbines only when you were breaking you would still not actually gain anything. Adding the turbine will increase the weight of your vehicle requiring more energy for a given speed. So during the entire time you are driving you are using more energy than you would if there was no turbine inside the car. Then you would have to make up all of that energy when you break.

 

[xxChrisxx]

I would suspect that even if you were able to duct the air to the turbines only when you were breaking you would still not actually gain anything. Adding the turbine will increase the weight of your vehicle requiring more energy for a given speed. So during the entire time you are driving you are using more energy than you would if there was no turbine inside the car. Then you would have to make up all of that energy when you break.

Turbines don't really weigh anything substantial, especially of the size we are talking about, were talking a few kg. Even 10kg is only about 1% increase on the weight of a small car. The amount of general crap in peoples boot outweighs that. More weight also only affects acceleration and load needed to go up hill.

However, you are right that it's almost performance neutral, any gains are so small (if any as you say) that it's really not worth bothering with. Which is why people havent.Also one thing people need to remember when coming up with a 'radical idea' for the IC engine. It's all been thought of and done before, surprisingly early infact. The reason why most things we think of as 'new' and 'revolutionary' are becuase materials technology has not allowed old ideas to be realized.

 

[boneh3ad]

More weight also only affects acceleration and load needed to go up hill.

In a frictionless world, yes. However, more weight means more tire friction means more horsepower to maintain a constant speed. You know what they say... friction's a *****.

 

[xxChrisxx]

In a frictionless world, yes. However, more weight means more tire friction means more horsepower to maintain a constant speed. You know what they say... friction's a *****.

Typical Rolling resistance coefficient of a tyre rubber to concrete is about 0.01, its less on tarmac. The retarding force at anything above about 30-40mph is about equal parts drag and RR. At 60mph or so you can pretty much ignore RR.

Also we are only talking about a minor % increase in mass. too little to really make a fuss about.

I should have made that clarification that it was an assumption earlier.

 

[boneh3ad]

Right, so doing the math says that the additional weight will cost you probably on the order of a few mL of gas over a 100 km journey due to rolling friction.

However, the drag on a turbine is enormous. I have seen quoted values of Cd for wind turbines well in excess of 1, which is enormous. That puts the added fuel consumption on the order of at least a quarter liter driving at 50 mph for 100 km, and that is assuming Cd is 1 and the frontal area of the turbine is only .25 sq m.

It is definitely a significant penalty to gas mileage.

 

[xxChrisxx]

But after demeaning my question, at least you basically said that it would be possible through ducting to allow some of the air through a turbine during braking and 'overrun' (not sure what you mean by overrun).

Overrun is when the engine is turning with the throttle is closed and the engine is acting as a brake. In modern cars the injectors are cut off so that no fuel is used. An example would be going down a hill in a low gear. The engine doesn't need to provide power to turn the wheels. Instead the wheels actually turn the engine.

The ducting would have a closable flap. So that when the engine is powering the car forward the flap would close and the air wouldn't flow near the turbine, so you don't get the drag penalty. But when you enter overrun, the flap would open and allow air to flow down the duct and spin the turbine when the drag penalty doesn't matter.

As you said about using the KE of the axle spinning to power a generator. This is essentially how regenerative braking and F1 KERS works.

 

[minger]

First of all, yes we've had a few "Turbines on cars" threads. More importantly though, this is probably the first that actual has a little reason behind it; I personally find it refreshing.

The question is whether or not you could use a turbine to extract energy during braking. The answer is yes, there should really be no argument about it. Of course, you would need some method to avoid loading the turbine during normal vehicle operation, but the fact remains that yes you can use it to slow down.

Could you run high-pressure water through your brake rotors which heat up low pressure water in a heat exchanger which in turn creates steam, powers a steam turbine which spins a generator? Probably at 0.1% efficiency, but hell it could be done.

Many luxury, high-performance cars already have ducts which cool the brakes. I am 95% sure the CTS-V does. Perhaps one could rig a mechanical flapper valve from the brake pedal to the ducting to send the air to the turbine during stopping.

As for weight, I used to be in the small gas-turbine biz, and some of them can be incredibly small and light. Seeing as how you only need the turbine and some generator, you could easily fit one on each side using the same amount of weight that the AMA says I am overweight by.

I don't think the OP was ever considering having the turbine in operating during acceleration/maintaing speed/coasting, so let's not bang on him so much. Is all of this plausible or practical? Probably not. But, neither is a lot of stuff we do.

 

[xxChrisxx]

First of all, yes we've had a few "Turbines on cars" threads. More importantly though, this is probably the first that actual has a little reason behind it; I personally find it refreshing.

Yeah, on a second reading of the OP there is more thought behind this thread. I just read 'Let me make something clear right away, I don't think perpetual motion is possible.' and thought here we go again!

microsoftMan normally whenever a post starts off with that phrase it is 99% likely the thread is about perpetual motion.

It lead me to be a bit more curt than I otherwise would have been, so I apologise about that.

 

[Unrest]

All this talk about added weight is irellevant -

If you already have regenerative braking (like hybrids do) then any extra regenerative braking (ie wind turbine) can add nothing, just robbing Peter to pay Paul.

If you don't have regenerative braking (like conventional cars) then what can you do with that electrical power? You can't run the engine because it's not electric. So again it can't server any purpose. If you did somehow find a use for that electric power, you'd get it more efficiently from regenerative braking.

 

[microsoftMan]

Right, so doing the math says that the additional weight will cost you probably on the order of a few mL of gas over a 100 km journey due to rolling friction.

However, the drag on a turbine is enormous. I have seen quoted values of Cd for wind turbines well in excess of 1, which is enormous. That puts the added fuel consumption on the order of at least a quarter liter driving at 50 mph for 100 km, and that is assuming Cd is 1 and the frontal area of the turbine is only .25 sq m.

It is definitely a significant penalty to gas mileage.

Right . . . I don't think you even read my original post. I was not asking about using it during acceleration/coasting but only when braking. So the added drag is the idea not an undesired consequence.

I was thinking that if utilized on an Electric Vehicle, the ducted turbine could open when parked as well to help contribute to the charge of the battery.

Thanks to some of you who aren't just completely bashing this thread.

By the way, I agree that it is an added complication to the internal operations of the automotive but I think that turbos, electronic controls, computer-controlled everything, and many other enhancements that have been made to cars are similarly over-complicated but benefit the driver/machine in a multitude of ways including gas mileage and the gas is obviously increasing in price continuously.

 

[Unrest]

benefit the driver/machine in a multitude of ways including gas mileage and the gas is obviously increasing in price continuously.

Hehe actually I heard that modern cars have worse gas milage than a few decades ago. The reason is all that multitude of complicaitons, squeezing every last drop of efficiency out of it is totally wiped out by cars just being bigger than before.

I think petrol prices don't matter that much to most car buyers, at least in America where it's not taxed much. If you've got a job you can pretty much afford to drive as much as you like. That despite prices going up continuously since forever.

 

[microsoftMan]

Hehe actually I heard that modern cars have worse gas milage than a few decades ago. The reason is all that multitude of complicaitons, squeezing every last drop of efficiency out of it is totally wiped out by cars just being bigger than before.

I think petrol prices don't matter that much to most car buyers, at least in America where it's not taxed much. If you've got a job you can pretty much afford to drive as much as you like. That despite prices going up continuously since forever.

Well not all of the 'complications' result in added fuel consumption. To name a few: fuel injection (more complete atomization of fuel results in higher efficiency and better distribution), direct port injection (quite complicated, fairly newly realized, great for efficiency), turbos (not just for speed, great for gas consumption and though failure-prone we see them popping up all over the market), aerodynamics, and emissions systems (better for environment but also results in a more efficient use of gasoline).

I think the complications you're thinking of are more along the lines of safety/convenience. Sure power steering, airbags, computers, and a few others I can think of present no gain in net efficiency unless you think of staying alive as a contributing factor to your personal efficiency. My 89 accord weighs far less than my 02 accord, and has a smaller engine with a carburetor. Yet the 02 still gets comprable gas mileage.

 

[Unrest]

Well not all of the 'complications' result in added fuel consumption. To name a few: fuel injection (more complete atomization of fuel results in higher
..
My 89 accord weighs far less than my 02 accord, and has a smaller engine with a carburetor. Yet the 02 still gets comprable gas mileage.

I think you misunderstood me. But you see the point. from 89 to 02 it hasn't improved in any noticeable way, despite the change from carbs to fuel injection and all the rest. Those improvements are counteracted by it being heavier, which I suppose may be a combination of safety and fashion.

Regarding using a wind turbine while you're parked. If you had a hybrid and you were so concerned about petrol use, you'd have got a plug-in hybrid and be charging off the grid. If you didn't like paying for the grid power, you'd have a wind turbine on your house, because you wouldn't want to pay for grid power in your house either. Then you can still plug your car into your house to charge.

Also, a wind turbine small enough to fit in a car, and in a city street, is going to generate diddly squat electricity while you're at work, compared to what you used just doing a parallel park.

 

[xxChrisxx]

Get rid of the engine.
Propel the car like Fred Flintstone.
Enjoy savings in the cost of petrol.

 

[Caladorcp]

Now don't jump me when I say this because I am not a science student and haven't taken a lot of physics or anything. But what about adding a wind turbine somewhere on an electric car. The wind turbine would act as supplement to keep your car going further on a charge.

I had the idea for a car with a wind turbine in it and decided to search it on the internet to see if anyone else was looking into it. I felt unique for a moment lol.

 

[Unrest]

Now don't jump me when I say this because I am not a science student and haven't taken a lot of physics or anything. But what about adding a wind turbine somewhere on an electric car. The wind turbine would act as supplement to keep your car going further on a charge.

You could if you were out in the desert in a post-apocalyptic world. But in real life it would be next to useless. If you want an extra 10 meters of driving, just plug into somebody's house for a minute. To get a feel for how piddly the power from a wind turbine is, imagine driving a similar turbine as a propeller - how well woud it propel the car?

Of course you have to stop the car to deploy the turbine. If you use it while driving it'll simply comsume power as has already been discussed.

 

[Caladorcp]

A simple, no I don't think that would work with a small explanation why would have been sufficient lol. I don't know much about wind power so for now I'll have to take your word for it. I just figured I'd see what others thought.

 

[Averagesupernova]

Caladorcp, all you have to do is realize that the wind rushing by the propellor is 'powered' by the forward motion of the car. The drag caused by the prop will cause more fuel to be consumed. I cannot think of any other subject that is this specific that has been proposed by the uninformed (no offense intended, no one is born loaded with knowledge) than this subject.

 

[Caladorcp]

Actually it occurred to me that I didn't explain what I meant properly. I meant to ask about a small turbine behind the grill of the car and if that would work as a supplement to the battery to get further on a charge. The wind turbine would move as air passed through grill of the car while moving down the road, but after looking up some stats on small wind turbines and on electric cars (and after doing a couple of calculations) I found it wouldn't work. It was a good thought though.

 

[Caladorcp]

Averagesupernova, as I said in my previous post I found it wouldn't work. I'm aware it would cause drag to put a wind turbine in, but I was not aware of the amounts of energy a wind turbine would create, therefore I didn't know if the amount of energy produced would overcome the amount of energy spent. I'm new at this lol. I just started taking an Energy Environment and Climate class at my local community college and was simply lacking information. Oh well, guess my wind car won't be happening lol.

 

[russ_watters]

Now don't jump me when I say this because I am not a science student and haven't taken a lot of physics or anything. But what about adding a wind turbine somewhere on an electric car. The wind turbine would act as supplement to keep your car going further on a charge.

Please read the thread. It reduces the distance you could travel, it doesn't add to it because the energy generated by the turbine comes from the battery before being put back into the battery.

Actually it occurred to me that I didn't explain what I meant properly. I meant to ask about a small turbine behind the grill of the car and if that would work as a supplement to the battery to get further on a charge.

A turbine behind the grille would block air from cooling the engine. Cars have fans behind the grille!

 

[Caladorcp]

Please read the thread. It reduces the distance you could travel, it doesn't add to it because the energy generated by the turbine comes from the battery before being put back into the battery. A turbine behind the grille would block air from cooling the engine. Cars have fans behind the grille!

Ok, I get it I'm stupid, alright! Geez, as I said before, I figured out it wouldn't work anyway so quoting me and telling me it wouldn't is completely unnecessary. Wow, some people. I was just curious if it would work, and because I didn't know if it would, I figured I would consult someone else who probably knows more than I do. All I was looking for was a simple no that wouldn't work or yes it would. As I said before I am new at this, meaning I haven't looked much into it.

You guys don't have to act like I'm stupid. Not everyone is knowledgeable about this stuff and you have to start somewhere, obviously that place isn't here. Sorry for being curious.

 

[Caladorcp]

That whole "don't jump me when I say this" thing was because I know I don't know much about this subject, and I was looking for people to be understanding that I am not knowledgeable in this subject. Just saying, no need to point out my obvious lack of knowledge like I'm some idiot.

 

[russ_watters]

You guys don't have to act like I'm stupid.

We weren't trying to make you feel stupid, but we do get somewhat irritated when people post in threads without reading them! (especially relatively short ones!). This question also comes up a lot, so people get a little fatigued seeing it over and over.

 

[Caladorcp]

Well as you should be able to tell, this being my 7th post EVER, I was not aware of this question being asked over and over, I just joined the site. And no I didn't read EVERY post, but you don't have to be rude about it. You could just say something like "That was previously discussed, you may want to look back at the previous comments" or something of that nature. Then I probably would have just looked back, problem solved. Anyway, this isn't what this thread is about so I'll stop with the proper manners stuff lol.

 

[Unrest]

That whole "don't jump me when I say this" thing was because I know I don't know much about this subject, and I was looking for people to be understanding that I am not knowledgeable in this subject. Just saying, no need to point out my obvious lack of knowledge like I'm some idiot.

Sorry if I offended you too. I thought I was being reasonable :P

However the behind the grill idea might not be too terrible. There was a somewhat new style of superbike made once (Britten?) that reduced drag by eliminating the grill and putting the radiator somewhere more aerodynamic. That suggests the grill could be a source of power loss for cars too. Maybe if the radiator were spread along the sides of the car and the otherwise wasted losses from the grill were used to generate power you might come out ahead of a normal car.

However if you put the radiator somewhere else, you might as well close off the grill entirely and save even more power, so it's back to being less efficient with a wind turbine in there.

 

[Caladorcp]

Sorry if I offended you too. I thought I was being reasonable :P

However the behind the grill idea might not be too terrible. There was a somewhat new style of superbike made once (Britten?) that reduced drag by eliminating the grill and putting the radiator somewhere more aerodynamic. That suggests the grill could be a source of power loss for cars too. Maybe if the radiator were spread along the sides of the car and the otherwise wasted losses from the grill were used to generate power you might come out ahead of a normal car.

However if you put the radiator somewhere else, you might as well close off the grill entirely and save even more power, so it's back to being less efficient with a wind turbine in there.

Apology accepted, that's what I hate about posts, you can't read into someones words very well. After looking up some stats on some small turbines I thought probably any turbine small enough to fit behind the grill of a car wouldn't produce much power anyway. It's a cool thought though (putting a turbine in the grill),
some other adjustments of the car would be necessary to achieve it. (adjustments of which I'm not sure of, I'm not a mechanic lol). I might have to take a closer look at the inner workings of an electric car first before I call this idea "dead."

That's cool with the superbike. I'm actually want to buy a motorcycle myself :), but school comes first. Paying for a motorcycle isn't in the budget right now lol.