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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.
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.
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.
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.
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.
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.
It is also more explosive.
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.
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.
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)
Compressing gas has a fairly lousy energy return. The air heats up when being compressed, and that heat is wasted unless you insulate the tank.
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.
Isn't carbon-fiber dust incredibly bad for your lungs?
Kinda, though I prefer my invisible hills analogy better. ;)
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.
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