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Prototype Volvo Flywheel Tech Uses Car's Wasted Brake Energy
cartechboy (2660665) writes "Sometimes we get carried away with sexy moonshot car tech--whereas most everyday gains are about reducing inefficiencies, piece by piece. Volvo's flywheel energy-recovery prototype is a great example of the latter--not to mention similar to one used in Formula 1 racing. The system recaptures energy that would be wasted in braking, like a hybrid does, to reduce fuel consumption by up to 25 percent. When you hit the brakes, kinetic energy that's usually wasted as heat is transferred to a "Kinetic Energy Recovery System" mounted to the undriven axle. It spools up a carbon flywheel that turns at 60,000 rpm to store the energy. When the driver hits the gas, some of the stored energy is transferred back to power the wheels through a specially designed transmission, either boosting total power to the wheels or substituting for engine torque to cut fuel consumption."
This seems great for high or nearly-sustained speed driving, but what I really want is an electric only option from 0-15 mph, a "parking garage" or "traffic jam" mode that I can put my car into.
I want to delete my account but Slashdot doesn't allow it.
Now all you need are hundreds of little magnets around the outside of the flywheel, and a bunch of little switched coils surrounding the case. Then you can control the thing with a computer and you have a hybrid that doesn't have to worry about high end gear rations vs. low end.
" “some form of KERS” would be inevitable on production cars after 2020."
I'm hoping that by then, electric cars (with regenerative braking) are starting to become the norm.
Really, 2020? With the pace technology develops, this might as well be Star Trek.
Since you are spinning up a high-speed gyroscope, if you are braking through a turn I wonder if it effects handling in any significant way.
I love this idea (and why has it taken so long to come to consumer cars), but please don't screw up the basic UI of a car the way some hybrids do! The brake pedal is for braking, dammit; simply lifting off the gas pedal should result in nearly coasting, unless I've deliberately put the car into a low gear for engine braking.
The hybrid I test drove (and I understand this is normal) would do regenerative braking up to the limits of that system on a simple lift-throttle, where the brake pedal was just the brakes. Talk about leaking the implementation details through to the UI! Don't do that!
For all I complain about UI designers, engineer-designed UIs are worse still.
Socialism: a lie told by totalitarians and believed by fools.
The big factor is mass. To store energy you need to spin up and down the mass. However to drive in general you want to carry less mass on the vehicle.
Factor #1: A more massive flywheel can store more energy at slower spin rates.
Factor #2: A more massive flywheel is going to be more of a load in general driving.
The optimium point of flywheel mass is going to depend on driving conditions. Really you should have at least 2 interchangeable fly wheels that you physically replace in the vehicle. One flywheel for city driving one for highway driving.
Factor #3: A spinning flywheel is one hell of an energy store. Having a stopped vehichle with a fully spun up flywheel hit could release the spinning flywheel to the detriment of pedestrians in the neighborhood.
Factor #4: Starting from a stop and attempting to corner, left or right, having a spinning flywheel is going to do gyroscopic things to the vehicle.
There are all sorts of tradeoffs and safety considerations here.
It briefly stores energy from braking and uses it to accelerate a moment later. If you don't hit the brakes, it does nothing. If you hit the brakes and stay at a low speed for five minutes, it does nothing.
When it works is when you stop (which stores energy), then go (which uses the stored energy). In other words "stop and go" traffic is EXACTLY what this is designed for.
It would seem to me that at 60,000 RPM, the rotational momentum is so much higher than the linear momentum that 1) and 2) aren't really a problem.
3 and 4, on the other hand, could be a problem.
So what happens when the flywheel shatters at high speed?
-Hentai [in vita non pacem est]
. . .for this to be in a production car. Back then, I read an article in Discover (?) Magazine about Mercedes working on this technology. Then nothing until today. Sounds great, to me.
Also a really interesting tech I read about at that time was smaller motors at the wheels. No need for transmissions and shafts and gears.
Pie in the sky tech I heard about then, too, was instead of brush and coil motors, having charged plate motors.
Still nothing on those last two.
Williams F1 has been working on this technology for quite awhile now. It's definitely fascinating. This video shows the technology applications.
Harrison's Postulate - "For every action there is an equal and opposite criticism"
It occurs to that this is basically a larger copy of the "friction motor" that was used in toy cars. The ones you'd spin up by rolling them on the floor , then you let go and they speed away. If you ever played with those, you know that the spinning flywheel has WAY more than enough rotational energy than required to accelerate its own mass. Those aren't going nearly 60,000 RPM either. (I think, I've never measured their flywheel speed.)
If you are a careful driver and plan ahead to avoid quick braking, and also accelerate at a very modest rate your benefits would be small with this kind of system. It helps compensate for aggressive driving but it seems like it won't benefit drivers that already are trying to get good gas mileage.
That seems to make sense and seems like an interesting idea. Can you express it using a car analogy?
He's getting rather old, but he's a good mouse.
If you are a careful driver and plan ahead to avoid quick braking, and also accelerate at a very modest rate your benefits would be small with this kind of system. It helps compensate for aggressive driving but it seems like it won't benefit drivers that already are trying to get good gas mileage.
Very true of highway driving, less so for stop and go city traffic.
XML is a known as a key material required to create SMD: Software of Mass Destruction
This isn't a new idea. It's been tried several times since 1950 for city buses, which are constantly stopping and starting. In 2009, one was developed for use in London. In the 2009 model, the linkage to the flywheel is mechanical, through a continously variable transmission, not electrical. Although this has been in test for several years now, it's only one bus.
That's the same technology Volvo is using. Putting this in a car seems marginal. It makes more sense for buses and delivery vans.
I hate getting caught behind one of those "How slowly can I accelerate and still call it acceleration" types. Invariable on my commutes, it's those dickheads that do not understand that the lights are timed for NORMALS and cause a huge traffic jam behind them from stopping at every damn light. Yeah, you save a LOT of gas stopping at every light on the road instead of getting up to speed in a reasonable distance and getting the green. I have one road on my commute that has 15 consecutive lights. Pass the eco-nazis and I never have to stop. Get caught behind them and my commute time doubles.
This sucks, every so often I come to Slashdot, and the interface has changed from black text on white, to gray text on gray. It just sucks. Fix this crap please.
Not at all - if you hit the brakes at all you're throwing away kinetic energy as heat, no matter how aggressively or gently you do so. This system allows you to capture some of that energy instead and use it to accelerate again later. Unless you are in the habit of coasting to a stop without using the brakes or engine-braking at all this will reduce the associated energy waste.
--- Most topics have many sides worth arguing, allow me to take one opposite you.
They call it regen. It uses components the car already has, adds no weight and no cost.
this concept has been used for awhile in UPS (battery backup) systems with a giant heavy flywheel on a generator-type spindle, which is kept spinning by electric motor power until the power goes off and then the rotating energy is put out into a generator to output AC power to critical electronics
This air-hybrid system uses nitrogen, hydraulic fluid, a hydraulic motor, and a couple of high-pressure tanks. I imagine it shouldn't cost much more than this flywheel, and it should store energy much longer.
(T>t && O(n)--) == sqrt(666)
Seriously, rather than focusing on a much cheaper saner approach of a simple electric car, these car makers continue to make more and more complex systems, which will have maintenance issues down the road.
This is why tesla, and I think Nissan, will become major players in the car making business.
I prefer the "u" in honour as it seems to be missing these days.
Early tractors had the power take-off geared directly to the final drive. So if you were using a big rotating implement like a mower which was driven by the PTO you needed to be very careful when you got to the end of the field because the mower had so much energy you had no chance of stopping the tractor with the brakes.
To get over that they added a coupler that would let the machine freewheel. I've been on a tractor without that coupler and it's pretty scary. Not stop and go, just go and keep going.
According to the article, it holds the energy for ~20 minutes.
Sure, let me give it a try:
The heavier the car, the more energy there is to store when you stop.
So you add a device to store the energy for later.
BONUS: you just made the car heavier, which means you have even more energy to store.
So now you can restart from scratch easier using the stored energy, unless you didn't have energy stored and have to restart a heavier car.
But you can't have bad performance when starting, so you need a bigger engine.
BONUS: you just made the car heavier again
So you add a few more bars to protect you in case of a crash, what with all these heavy vehicles on the road, you know...
BONUS: you just made the car heavier yet again, man do you have a lot of energy stored in that bigger flywheel that you put in to better recover the bigger energy of the heavier car!
You're definitely saving a lot of gas, in stop-and-go traffic, compared to the other huge cars!
On the other hand, an econobox will get you from the same point A to the same point B for 3l per 100km (or over 60mpg) and cost a quarter of the price.
Of course, we can trust the average Joe to properly maintain a piece of hardware designed to rotate at 60000 RPM, right?
I'm looking forward to cars just blowing up when they come to a stop because unmaintained flywheels explode and shrapnel likes gas tanks, according to hollywood.
People who don't leave adequate braking distance and accelerate as hard as possible are the reason most of the traffic jams on my morning route occur. A single light touch on the brakes gets magnified into a ripple of progressively more urgent braking until you have traffic that grinds to a stop - no obstruction required. A few large gaps help to absorb this kind of thing and would keep the traffic flowing, but the few people who seem to think that tailgating people at beyond the speed limit until they give way and let the guy overtake you - so he can do the same thing to the next guy in the fast lane going the same speed - is acceptable make everyone else so paranoid that they are missing out on a particular piece of road that hardly anyone is willing to leave any space.
If everyone drove with a little more room, then the traffic wouldn't jam up so much, and paradoxically, people would get to their destination faster. The tailgaters are just spoiling their own driving party.
That one uses electric motors. The Volvo one doesn't.
So what happens if you come to a stop and then want to turn right? You have a flywheel spinning real good and you're trying to change its axis. Either it's going to twist and bust its bearings and do considerable mayhem, or your car is going to go around the turn on two wheels. Fun times!
Going from memory from many years back, there was a few very interesting points when I was reading about flywheel research for hybrid F1 racers
1) Something like 90%+ efficient at converting physical energy into rotational and back out
2) Decided to use carbon fiber because instead of turning into shrapnel, it disintegrates when it smashes into its cage
3) Added less weight than an extra person
4) Was able to supply 80hp for 10 seconds at max
5) Was able to quickly and efficiently capture energy, so you could slam on the breaks and get your 80hp for 10 seconds very easily
6) Increased fuel efficiency for F1 racers by 10%-20% because of lots of hard breaking followed by hard acceleration.
I'm sure other safety issues will bring down the effectiveness of these devices for regular car users, but there is a lot of margin to make it an overall win.
Accelerating at a modest rate is not particularly an advantage in a petrol car. Petrol cars are only decently efficient under full load, so you want to accelerate quite swiftly, using as high a gear as possible. If you are driving an automatic, it will spoil that idea by "helpfully" shifting down when it detects that you are pushing the accelerator, so that only works in a manual.
Finally! A year of moderation! Ready for 2019?
3l/100km is a myth. See The most fuel efficient vehicles.
The only ones that come close are 2 tiny diesel cars. Both have been out of production for almost a decade.
Finally! A year of moderation! Ready for 2019?
Actually, yes, I think we can, strangely.
Imagine you're coasting your way to the top of a hill and stopping at the top of it, with the brakes doing very little of the work in stopping you. By cresting to the top of the hill, we've effectively converted the kinetic energy you had into potential energy that can later be reclaimed when you go down the hill, and we've lost very little of that energy to heat from the brakes. That is, we can reclaim that stored energy to get a good chunk of the way back up to speed for a fraction of the fuel cost that it would have taken had that energy been lost.
In much the same way, a flywheel is capable of converting forward momentum into a form that can then be used later. You can think of it as an invisible incline under the car every time you hit the brakes, helping to bring you to a stop while storing that energy for later, and an invisible declination under the car every time you follow the braking with the accelerator, helping you get back up to speed without having to consume as much fuel.
(I'm now eagerly awaiting corrections, since I'm sure I misused terms and explained things poorly)
My 2005 Prius already have this technology as does many other hybrid vehicle.
They are not a myth.
Perhaps you should read and try to understand what you link.
Quote: Please note that only representative entries are considered
Most cars that use 3l or less fuel are sold in very low numbers, that is all.
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
I my point invalid if I write 4l (essentially 60mpg) or 5l (~50mpg)?
I point at the moon-sized battlestations driving by, don't stare at my finger
This flywheel is spinning at 60,000 RPM.
Energy = mass * velocity^2 if I remember correctly, so this flywheel has a like million times as much energy and therefore potential danger.
Engineers please feel free to correct me, or actually do the math.
I know spritmonitor.de very well. They are one of very few sources of real fuel consumption data. Not silly test data that no one can achieve in practice.
Feel free to provide examples of in-production econoboxes with a 3l/100km fuel consumption under real-life driving conditions.
Finally! A year of moderation! Ready for 2019?
My car is not a 3l car, but in city use, in summer, my Peugeot 307 uses below 3l. In the city, gear 5, rolling with 50km/h.
There are true 3l cars from Fiat and the Lupo from VW, should be easy to google for.
However the market share is irrelevant, hence they are not 'significant' and hence not listed on spritmonitor.de
Cost free eBook I read (by iBook/Kobo/Amazon/ObookO/Gutenberg etc.): "The Green Odyssey" by Philip Jose Farmer.
5l is doable in a petrol hybrid, and you can get quite close with certain non-hybrid petrol econoboxes.
Finally! A year of moderation! Ready for 2019?
All Tesla proves is that it's easier and quite possibly cheaper to send payloads into space and back than it is to make a reliable, affordable electric car. Recall that Tesla and SpaceX were founded by the same guy.
Flywheels are old, old technology. They're very well understood and very reliable. Practically all of the gyroscopic problems can be resolved just by dividing the system into two wheels rotating in opposite directions - the forces cancel out. Mass producing sophisticated, relatively massive, vacuum-packed flywheels doesn't require the kind of industrial and technological leaps that most people assume. Many appliance manufacturers already have the necessary facilities and experience. Intriguingly, so do hard drive makers. Making things spin extremely fast in environmentally sealed compartments while aided by self-balancing technology is kind of what their engineers do.
Flywheels also charge and discharge far faster than batteries (their specific power can be absolutely gigantic) and flywheels made from modern composites have energy densities that compare favorably to batteries. These materials also tend to turn into powder when the wheels shatter. The worst case failure mode for one of these things breaking is nothing an inch or two of kevlar can't reliably stop, so flywheel explosions should only be a concern in designs lacking some pretty basic safety features.
Batteries are attractive for a lot of reasons but as far as I'm concerned, battery chemistry is a dead horse. I've been following this subject for a very long time - it's not getting better anytime soon and given the research climate there's no reason to even assume that most of these 'breakthroughs' that get trotted out every month or so are even real. (A decade of watching and waiting has shown me that almost none of them make it to market.) The specific power and charge rate problems aren't going away. I think Volvo is ahead of the curve on this one.
0-60 in 6 seconds.
http://www.youtube.com/watch?v=fo3hhvHJlKU
http://www.youtube.com/watch?v=RyS1LnDodu8
Using them to smash packages more efficiently?
I doubt weight is an issue for this flywheel. When you have a carbon fiber flywheel, you're trading 60k RPM over mass @ low rpm.
I just want to know what kind of bearings this thing uses, and it expected MTBF rate is.
Life is not for the lazy.
My co-worker is convinced you can use this method to make cars run forever. *facepalm
Yep it won't help all 3 of those people in the world.
It will help everyone else.
I'm no expert, but I think two flywheels would reduce the problems and three could almost eliminate it. I believe flywheels have effects along two different axes.
Now you can brake like a bus!
"Nine times out of ten, starting a fire is not the best way to solve the problem." - my wife
This sort of system would be good for driving in secondary streets (stop signs instead of lights) and where right turns on red lights are allowed where drivers often do not need to stop any longer than necessary to verify it is safe to cross. With the flywheel, you can do both quick stops and quick starts without worrying so much about fuel efficiency. On main streets where lights are timed for a specific speed, accelerating too slowly may cause you to either be too late for the next green light or cause many drivers behind you to miss it, which is sometimes considered dangerously low speed.
In an automatic transmission, a slow acceleration has higher losses in the torque converter until it spins fast enough to lock and slow braking wears brakes down more quickly.
"On the other hand, an econobox will get you from the same point A to the same point B for 3l per 100km (or over 60mpg) and cost a quarter of the price."
Doesn't exist
"Of course, we can trust the average Joe to properly maintain a piece of hardware designed to rotate at 60000 RPM, right?
I'm looking forward to cars just blowing up when they come to a stop because unmaintained flywheels explode and shrapnel likes gas tanks, according to hollywood."
Turbochargers don't explode all the time, and they spin at even faster speeds (around 5 times)
I've got better things to do tonight than die.
> Doesn't exist
Moon... finger... see other reply
or go get a motorcycle
>Turbochargers don't explode all the time, and they spin at even faster speeds (around 5 times)
Educate me. Are turbochargers designed to provide "80HP for 10s" (through a mechanical linkage), as another poster put it?
Those stupid engineers, don't they just know that electric cars are like, the future.
Isn't carbon-fiber dust incredibly bad for your lungs?
They have this on the ISS too . and on satellites. it helps them point the suff in the right direction. ... would you
i'm wondering if this thing has spun up to max and then you turn a sharp 180 degrees
go around on two wheels?
If you are a careful driver and plan ahead to avoid quick braking, and also accelerate at a very modest rate your benefits would be small with this kind of system. It helps compensate for aggressive driving but it seems like it won't benefit drivers that already are trying to get good gas mileage.
Citation needed. Accelerating at a very slow rate would be worse for fuel economy in most cases. Two cars drive a 10 mile stretch. The first accelerates to 50mph in 100 yards and stays there... the second uses the entire 10 miles to get up to 50mph. Which do you think will be more fuel efficient?
I'd appreciate any evidence that hard acceleration is necessarily worse for fuel economy. There must be a sweet spot, rev too high and you lose fuel efficiency of the engine, accelerate too slow and you take too long to get to optimal speed. I'd personally guess accelerating hard in higher gears (ie. low rpm) until you get to 50mph or so would be the most efficient, but I am only guessing.
It also sounds great for windy roads where you'd have to brake for corners often.
Oh, you mean like a flywheel?
Someone flopped a steamer in the gene pool.
If new highways were designed so the cross streets were above them (overpasses) rather than the highway going over the cross streets, cars would decelerate as they climbed the hill towards the intersection. Then they would save gas from the intersection going downhill towards the merge with the highway traffic. Less wear on the brakes and the engine along with a fuel savings. In some cases anyway. It's not going to be a huge savings, but every little bit would help.
Kinda, though I prefer my invisible hills analogy better. ;)
I think you maybe wrong about that - my understanding is the flywheel can remain spinning (energized) for a significant time period after the car is shut off.
Aren't there already trucks that do this with air compressors? Strange it's completely unmentioned.
As Volvo has laid out the implementation the KERS powering the rear axle allows effective AWD without the need for a "propeller shaft" to send power to the rear of the vehicle. AWD additional complexity happens no matter whether a car is electric or petroleum power. What about maintaining a set temperature range for a battery pack and shielding large battery packs that may stretch a significant length of the car from debris/crashes?. All the wiring needed to connect the cells that make up the battery pack? Charging infrastructure that has to deployed ? That IS complexity compared to Volvo's KERS system augmenting an internal combustion engine.
On main streets where lights are timed for a specific speed, accelerating too slowly may cause you to either be too late for the next green light or cause many drivers behind you to miss it, which is sometimes considered dangerously low speed.
Am I the only one who frequently notices inconsiderate assholes (probably compensating for something small of theirs) who seem to deliberately and unnecessarily hesitate at intersections, with the express goal of making anyone behind them miss the light? I mean when you can see a mile or two down the road and the intersection is obviously clear, this really makes no sense and cannot be excused by a notion of caution.
It is a miracle that curiosity survives formal education. - Einstein
Thanks. I think you're missing a critical factor, though.
Consider two bicycle wheels, both turning at 1 RPM. Both weigh 100 lbs.
One wheel is 1 foot in diameter, so its rim is going 1 foot per second. 1fps^2 * mass = energy.
The other wheel is 10 feet in diameter, so its rim is going 10 fps. 10 fps^2 * mass = energy.
Probably the diameter of one flywheel will be no more than twice the size of the other. When squared, that results in FOUR times as much energy just by increasing the circumfrance, right? Then 100X as much by the increase in speed. So 400 times as much energy if they are the same weight.
One squared is one. Ten squared is one hundred.
Same weight, same speed, but 100 times as much energy.
I was out for a walk this week, and watched a garbage truck make his rounds. If anything needs regenerative brakes, it's a garbage truck.
Great! As if one transmission was not enough. Now I will have to worry about the cost of repairing two. The last one that failed cost me over $3k. I think that's one of the great things about hybrids, no transmission.
yes, it's like kers used in f1.
seriously the whole article could have been replaced with "volvo has kers research". which isn't even news. all big european manufacturers have... from ferrari to bmw.
if they put kers on a sub 25 000 $ car then that would be actual news, but hey, it's volvo so good luck with that..
world was created 5 seconds before this post as it is.
1. We're talking about cars, not motorcycles
2. Turbos and blowers can provide a lot more than 80HP boost.
Albeit a battery seems more logical than a big flywheel (and more efficient). What would be even better would be a diesel generator (like in locomotives). Even better economy as the engine would run at optimal efficiency. I'm sick of having to choose between 2 or 3 engines when the same car in Europe has 3-4 gas engines and 3-4 Diesel engines to choose from. (not to mention the Fusion/Mondeo is available as a station wagon)
I've got better things to do tonight than die.
Volvo's flywheel energy-recovery prototype is a great example of the latter--not to mention similar to one used in Formula 1 racing.
I'm not sure any of the teams are using flywheels in their KERS systems. I think they're all using batteries. This year the formula has changed from naturally aspirated V8s with KERS to V6 turbo hybrid power units.
http://www.lmgtfy.com/?q=angul...
Wiki has polysyllabic words, though, which I suspect you may have trouble with, so let me explain it real simple for you:
Go out in the garage and turn your big sister's bike upside down, so the handlebars are on the ground.
Turn the pedal as fast as you can.
Put your hand on the tire.
You'll notice the tire is moving real fast.
You've just experienced the velocity of a spinning object.
Try the same experiment with daddy's bike.
You'll have to push the pedal much harder to get it going real fast because the wheel on daddy's bike is bigger and heavier.
It's hard to make a big, heavy thing go fast. You have to work harder to turn the pedal fast.
Scientists measure that hard work and say the big, heavy wheel has more "energy".
Now go play with your toys and let the grown-ups talk.
I'm really worried about your breaks braking. Are you sure you didn't mean brakes breaking?
I guess that depends on your brakes, lucky or otherwise.
Gosh, such pun.
I'll be here all weak.
"Cats like plain crisps"
volvos are so heavy and have such lousy gas mileage that 25% improvement still leaves them in the dust. after 4 volvos, i just couldn't justify the horrible efficiency (yes - standard transmission to capture every last bit) -now i drive a prius - let's see - 50,000 miles at 50mpg vs 20 mpg - that works out to 30,000 free volvo -equivalent miles. 25%? still pitiful.
Mostly wrong.
Full throttle is quite inefficient, it's overly rich on purpose to avoid excessive combustion temperature/pressure and damaging exhaust valves.
*near* full throttle in medium-high rev range is usually most efficient, usually at 80% throttle or so.
If you can get the specific fuel consumption surface/curve set for your engine it's trivial to answer, but nowadays manufacturers consider those to be seeekrit!. Fucks.
As for automatics... if you're triggering kick-down you're already well beyond the efficient range anyways. And yes, if your transmission doesn't have a eco mode you likely have to temporarily back off to allow it to upshift to stay within the "green" RPM range.
Citation given
That was actually a very good explanation. It's like summoning up a small hill to stop you and to give you a rolling start.
http://en.wikipedia.org/wiki/G...
Please register on spritmonitor.de. Your numbers will be very welcome there.
The Lupo has been out of production for a decade and only manages 3.5l/100km in practice.
Yes, if you go at a steady 50km/h any decent car can do 3l/100km or better. That is not a realistic test.
Finally! A year of moderation! Ready for 2019?
Taxis are the obvious first users of this system, would help to make the city less smelly
"The hands that help are better far than lips that pray." - Robert Ingersoll (1833-1899)
Is it worse for your lungs than flying sharpnel?
(1.21 gigawatts) / (88 miles per hour) = 30 757 874 newtons
For those who don't like hill analogies,
The flywheel works in the same way as putting your car into a lower gear and breaking against the engine.
You can picture it as the flywheel being separated from the axle (via a clutch) and when you apply the brakes it connects the flywheel up. You now have the inertia of the flywheel being overcome by the turning of the axle transferring the energy to the flywheel.
When you have stopped (when the system senses that the axle is no longer giving the flywheel any energy, when the rotational momentum of the flywheel is greater than that of the axle), the circuit is broken again and the flywheel continues to spin while the car is stationary. When you want to go forward again, the spinning flywheel is connected to the stationary axle again and that energy is returned in addition to engine power.
The efficiency isn't ever going to be great, as you are always working towards an equilibrium. From standstill, the engine speeds up the car. During braking, the axle and flywheel reach a balance, (up to 1/2 the rotational momentum - whatever is taken via brake friction). When re-accelerating, up to 1/2 of the energy can be transferred back to the wheels + engine.
The flywheel will continue to spin, slowly losing energy until the next braking event at which point it will spin up again, at some point reaching an upper threshold. So the flywheel is great for racing where there are numerous stops and goes but won't be that good for your average home user. The question really is, over the life of the car, will the energy saved by braking and accelerating be worth carrying the additional weight on highway trips of consistent speed.
well its like this
imagine you're surfing the internet and you're reading pages on the web, what happens is that a connection is made and then broken for each link on the page you're reading. Just like your stop/start journey.
So what this is like is using a connection that stays open a little longer, to recapture more data from the connection when it "stops" so when you "start" off again to fetch the next link it is already stored.
Imagine that you want to see, say an image on the page, its already loaded as part of the previous connection, saving "fuel" (repeated network connects in this case) and generally being more efficient..
I live in a modest coastal city where the traffic is relatively sedate. My main problem avoiding unnecessary use of the break pedal is that so many traffic lights appear suddenly as you crest a hill or exit a sweeping turn giving you no immediate indication of phase, and then BAM! just before the point of no return it goes yellow.
I pretty much make all my velocity decisions in phase space: how close in position/velocity to I wish to be with the traffic around me at which points in the terrain? I've read that gasoline engines are at the top of their conversion efficiency mound when producing about 2/3rds of maximum rated power, so I'm not shy about briefly laying it on to make a quick adjustment in phase space, but always with the goal of making the least possible use of my brake pedal later on.
Also, we've pretty much capped our top speed at 90 km/l since we're driving a small truck. We had a lovely Toyota Truck from way back that traded some paint at xmas. The smallest replacement truck we could find at a fair price is the ubiquitous Ford Ranger, which is a complete joke as representing a "small" truck.
The chicken tax: Why it's hard to find a small pickup truck
Sad news, ideologues. The entire electable spectrum has left the chicken tax alone, from Nixon to Bush to Clinton to Carter.
Countdown traffic lights may cause accidents, study says
Guess what? The carbon emissions also have a definite consequence. If not climate, then conflict. What's really going on here is escaping the horror of first order terms; it's an actuarial NIMBY effect. One death is a statistic. A billion deaths are somebody else's problem, if the coefficient can be construed as the least bit vague.
The real problem with countdown lights is that they require driver judgement. What you really want are a kind of runway light which indicates whether, from where you are—maintaining your current speed—you're going to make it through or not. The number the driver needs is dependent on individual conditions.
One way to do this would be to pot amber indicators in the pavement calibrated to the speed limit (it really should be called the "speed notice" or the "speed weed"—expect to be noticed/plucked if you drive faster than this). If you're driving at the speed limit, and the nearest such indicator in your forward path is illuminated amber, then you will arrive at the intersection in the amber condition.
If you gun it from 150 meters out from some low initial speed, you'll probably notice that you're losing the race with the amber rabbit in time to rethink your testosterone surge. If not, count on losing the long war of technological measures designed to strip you of your driving privilege. Driving stupidity/dead pedestrians breeds cameras. What part of this simple equation can't these people figure out?
This helps to explain the mysterious Flynn effect, where IQ is purportedly rising in the general population, but it's hard to see in real life. Nobody takes an IQ test sitting behind a steering wheel after rushing out of
I did write "break pedal" while still sucking down first coffee. At least I didn't type "break petal". I've done that, too.
Some people experience a brief paralysis on waking. This is caused by different parts of the brain waking up in different order. The brain ordinarily wakes up the steering wheel before the gas pedal, but there are sometimes exceptions.
Mod parent up. Funniest response I've seen in quite a while.
Imagine the toque exerted with breaking before a turn, from the gyroscopic force.
An engine braking analogy for Slashdot, a predominantly American audience, which is statistically unlikely to know how to drive stick.
Chuuch. Preach. Tabernacle.
Have you ever been diagnosed with schizophrenia?
Cheap storage VM.
It doesn't wok that way. The lights are timed so that normal acceleration and speed would follow the green wave. By micro accelerating and maintiaining slower speeds departure time is irrelevant as you are guaranteed to catch every red light.
I like that you bring up the safety issue. Everywhere I see talk of flywheels for energy storage there are two problems that come up.
Frist is that to balance added weight and efficiency the materials in the flywheel are stressed to their capacity. This means that in the event of a fault or damage like a collision the flywheel will fail catestrophically. If you want to see some frightening video look up video of flywheels that fail. The only way to prevent it from basically turning into a shrapnel bomb is to armor the enclosure so much it added hundreds of pounds to the device.
The other issue is that flywheels are gyroscopes. When loaded and at speed they resist turning in the same way a gyro does. To get an idea how much they resists turning play with a dynaflex. It is about a pound and spins at 10k, but creates enough resistance to being turned that it is painful to turn. A gyro spinning at 60K and weighing 50 pounds could stop your car from cornering.
I'd be interested to see how they overcome these two issues.
What Volvo doesn't mention though is that if you extract that kind of energy from a single flywheel system the car will spin violently if the tires break traction. The only way to handle that much torque is to have a dual flywheel system using counter rotation to negate that rotational torque. Step on the gas a little too hard when on ice and you are out for quite a surprise.
I would hope, though, that being /. readers, in a topic about energy braking and flywheels, the average reader would be somewhat familiar with the concept of manual transmission.
I know high end flywheel energy storage systems use magnetic bearings in a vacuum to reduce drag, but in this instance, I am sure just regular old mechanical bearings would do fine, since the energy is not stored for a long period of time.
Much interchange.
My argument on the turbo point was that, while the turbo gives you more engine power, it doesn't output it itself. I honestly don't know what the actual energy usage of the engine component "turbo" is, but it's a fraction of the "80HP for 10s". And that energy is not delivered via mechanical linkage straight to solid wheels, it's compressing air.
Therefore saying that a turbo turns 5x faster is a false equivalency, because the amount of stress on the components, and therefore the required care and maintenance (the original point), is orders of magnitude different.
this nag is trotted out. is this why volvo does so well in formula 1?
If cars were on electronic adaptive cruise control and set to keep only a few feet between cars, and cars were organized into platoons based on the length of the typical green light, everything would move faster and smoother.
Traffic tangles are chaotic systems with properties like a gas. Fast movers just increase the temperatures all around. Platoons are like polymers and step down the chaos.
Agreed, but the flywheel is spun carbon fiber meaning it will disintegrate in small pieces so I wouldn't worry about shrapnel. But you're right in saying it adds additional maintenance and stress on other components.
Looking at some vehicles here in Montreal (vehicles that should have been retired & destroyed years ago), let's just say that mandatory mechanical inspections would be a good idea...
I've got better things to do tonight than die.
better than a grand piano, but that wasn't the question.
Have you ever been diagnosed with schizophrenia?
Noticing that many people are too self-centered to consider how their actions affect others around them in a shared system is hardly schizoid.
It is a miracle that curiosity survives formal education. - Einstein
+1 Funny
"If you hit the brakes and stay at a low speed for five minutes, it does nothing."
Which is exactly the problem that I outlined in my point, although you seem to have achieved a +5, Obvious mark for it.
I want to delete my account but Slashdot doesn't allow it.
Except you said the exact opposite. You said it would be GOOD for a steady, sustained speed. I pointed out the opposite - it doesn't do anything unless you slow down, then speed up soon after.