• Gbg/100203 / Agenda Derek Crabb Foto: Roger Lundsten BLR-Fotograferna AB Kroksl�tts fabriker 17 431 37 M�lndal
  • Tomas Hanneb�ck Volvo Cars
  • Andreas Hinz Volvo Cars
Volvo has been experimenting with flywheel propulsion systems since the eighties, but only recently has technology caught up with the possibility of real-world applications. In 2011, the Swedish carmaker was granted 6.57 million Swedish kronor (about $1M US) by the Swedish Energy Agency to work on a kinetic energy recovery system with Swedish bearing company SKF. Before it began trials, Volvo expected the fuel savings to be as high as 20 percent. After trials conducted last year on public roads the results were even better, Volvo finding that a KERS-equipped four-cylinder turbo performs like a six-cylinder turbo but gets up to 25-percent better fuel economy. It calls KERS "a light, cheap and very eco-efficient solution."

The test vehicle was an S60, its ICE driving the front wheels while the KERS – weighing six kilograms, measuring about 20 centimeters across and using a carbon fiber flywheel – was attached to the rear axle. Under braking, the four-cylinder engine is shut off and the KERS gathers rotational energy, spinning at up to 60,000 revolutions per minute. The stored energy is then used to get the car going again or to assist at cruising speeds. It's the same kind of vacuum-sealed flywheel design used by Audi in its R18 etron quattro, but with the opposite arrangement – in the Audi the diesel V6 drives the rear wheels, the KERS drives the front wheels.

Like the units in Formula One, it provides an additional 80 horsepower. When working with the four-cylinder ICE, the S60 with KERS can do the 0-62 mph dash in 5.5 seconds, a full 1.1 seconds faster than the S60 with the 3.0-liter T6 engine and all-wheel drive.

As we expect with hybrids, the greatest fuel savings came in urban environments with a lot of braking, Volvo suggesting that the combustion engine could be shut down "about half the time" on the New European Driving Cycle. A press release below has more details, along with a video Volvo released in 2011 to show how its system works.



Show full PR text
Volvo Cars tests of flywheel technology confirm fuel savings of up to 25 per cent

Volvo Car Group has completed extensive testing of kinetic flywheel technology on public roads - and the results confirm that this is a light, cheap and very eco-efficient solution.

Apr 25, 2013 -- "The testing of this complete experimental system for kinetic energy recovery was carried out during 2012. The results show that this technology combined with a four-cylinder turbo engine has the potential to reduce fuel consumption by up to 25 percent compared with a six-cylinder turbo engine at a comparable performance level," says Derek Crabb, Vice President Powertrain Engineering at Volvo Car Group, "Giving the driver an extra 80 horsepower, it makes car with a four-cylinder engine accelerate like one with a six-cylinder unit."

The experimental system, known as Flywheel KERS (Kinetic Energy Recovery System), is fitted to the rear axle. During retardation, the braking energy causes the flywheel to spin at up to 60,000 revs per minute. When the car starts moving off again, the flywheel's rotation is transferred to the rear wheels via a specially designed transmission.

The combustion engine that drives the front wheels is switched off as soon as braking begins. The energy in the flywheel can then be used to accelerate the vehicle when it is time to move off again or to power the vehicle once it reaches cruising speed.

Most efficient in city traffic
"The flywheel's stored energy is sufficient to power the car for short periods. This has a major impact on fuel consumption. Our calculations indicate that it will be possible to turn off the combustion engine about half the time when driving according to the official New European Driving Cycle," explains Derek Crabb.

Since the flywheel is activated by braking, and the duration of the energy storage - that is to say the length of time the flywheel spins - is limited, the technology is at its most effective during driving featuring repeated stops and starts. In other words, the fuel savings will be greatest when driving in busy urban traffic and during active driving.

If the energy in the flywheel is combined with the combustion engine's full capacity, it will give the car an extra 80 horsepower and, thanks to the swift torque build-up, this translates into rapid acceleration, cutting 0 to 100 km/h figures by seconds. The experimental car, a Volvo S60, accelerates from 0 to 100 km/h in 5.5 seconds.

Carbon fibre for a lightweight and compact solution
Flywheel propulsion assistance was tested in a Volvo 260 back in the 1980s, and flywheels made of steel have been evaluated by various manufacturers in recent times. However, since a unit made of steel is large and heavy and has rather limited rotational capacity, this is not a viable option.

The flywheel that Volvo Cars used in the experimental system is made of carbon fibre. It weighs about six kilograms and has a diameter of 20 centimetres. The carbon fiber wheel spins in a vacuum to minimise frictional losses.

"We are the first manufacturer that has applied flywheel technology to the rear axle of a car fitted with a combustion engine driving the front wheels. The next step after completing these successful tests is to evaluate how the technology can be implemented in our upcoming car models," concludes Derek Crabb.


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    • 1 Second Ago
  • 75 Comments
      Gorgenapper
      • 2 Years Ago
      So it's basically like an accumulator...stores energy to be used later, recycling the energy.
      ChrisH
      • 2 Years Ago
      Buses should be able to benefit from this type of tech
      goodoldgorr
      • 2 Years Ago
      Perfect system for taxi that work mostly in town, less inpressive for highway driving though. If you do a lot of congested highway driving with frequent breaking and re-acceleration, then it save gas. If you stop at a red light and you have to wait 4 minutes, then does is still spin after 4 minutes to help re-acceleration. A battery system will hold the energy easilly for 4 minutes but a flywheel, i doubt.
        no1bondfan
        • 2 Years Ago
        @goodoldgorr
        The flywheel spins inside a vacuum, so it should lose very little energy even while spinning for a long time. The only loss inside a vacuum would be due to friction at the bearing. If they use magnetic bearings (which doesn't appear to be the case here), even that loss is removed.
      JakeY
      • 2 Years Ago
      I suspect the flywheel KERs has very good power density, but energy density is likely lower than batteries. The early F1 flywheel KERs had a system weight of 24kg (flywheel weight of 5kg). So I suspect the 6kg quoted here is the flywheel weight. Anyways the F1 KERs can provide 80hp (60kW) for 6.67 seconds, storing only 0.11kWh of energy. Some of the newer ones can store 0.25-0.5kWh, but that's still around the order of a lead acid battery for a micro-hybrid. So I suspect the efficiency gains will be closer to micro or mild hybrids than full hybrids. The main plus point is the performance gain.
      Wally SirFatty
      • 2 Years Ago
      UPS has been testing this in their trucks for a few years now....
      Kuro Houou
      • 2 Years Ago
      Wow, very impressive. Can't wait to see this in some kind of production form... will probably be another 5-8 years though :(
      Dave
      • 2 Years Ago
      Some big claims: http://www.youtube.com/watch?v=4PcIt0FPvWQ
      k_m94
      • 2 Years Ago
      Sounds cool. Worth noting that only the flywheel has a CVT, because it has no connection with the engine the engine's transmission could be manual, auto, whatever. Wonder how this would work if it powered the same set of wheels as the engine? Would there be a way to incorporate it with the main transmission?
      Hazdaz
      • 2 Years Ago
      Cool idea, and interesting application, but here's the thing. Its a dead-end solution. ICEs will have to get more and more complex to improve their efficiency, and its going to get to the point where automakers will finally figure out that its not worth it because in the end EVs will take over and actually SIMPLIFY the car, while all these other techs make it more complex. There was that story the other day about Tesla's CEO (Musk) saying that batteries could be seeing 500 mile ranges in 5-10 years. If we see even HALF that range, with prices more inline with what consumers pay now, then you can use KERS, Diesel, hybrids, HCCI, camless or any other crazy ass internal combustion engine technology, but its not going to keep the ICE alive for long. Yeah, its great seeing companies try new things, but at some point, its still improving on the typewriter in the computer era... ICE is on its way out.
        VL00
        • 2 Years Ago
        @Hazdaz
        Depending on the input/output efficiency, this could actually be more efficient than charging a battery under braking, so it could work just as well in EV's
        Cayman
        • 2 Years Ago
        @Hazdaz
        Sure, eventually internal combustion will likely go away in cars (or at least become rare); but it's not anytime soon. Eventually electric cars will be dead as well, that doesn't mean we should stop research on them.
        NissanGTR
        • 2 Years Ago
        @Hazdaz
        The ICE doesnt need to be more complex. Aero and weight are whats holding the engine back. The only car on the market that actually competes with the ICE costs over $100k. Electric cars are not going to hurt the superior engine anytime soon.
          VL00
          • 2 Years Ago
          @NissanGTR
          "Superior engine"? You mean that one that turned 75% of all the money you ever spent on gas into heat without moving the car 1 inch?
          Vlad
          • 2 Years Ago
          @NissanGTR
          ...just like smelly, noisy, unreliable, prone to fires ICE is not going to hurt horse sales anytime soon. Oh, wait...
          m_2012
          • 2 Years Ago
          @NissanGTR
          As long as engine waste 75% of energy input as nothing more than heat, even the most aero and light car will be horrible at being efficiency.
        k_m94
        • 2 Years Ago
        @Hazdaz
        Pedal power is simpler than electrical. Doesnt mean it's better.
        matal341
        • 2 Years Ago
        @Hazdaz
        I remember 2 years ago gas was estimated to rise to above $8 a gallon by 2025 and the EV market was expected to take up a high percentage of the market, some estimates put it at 25% EV, 55% hybrid. Well the oil scare has simmered down and so have projections, EVs are now expected to take up a measly 10% of future market share, so I am not sure how you have come to the conclusion that the ICE is dead. Never forget that as long as petrol is a relatively cheap fuel source (even the angelic EV's are powered by electricity generated by coal and gasoline powerplants), we will continue to squeeze the ICE. EV's are powered by costly batteries made of precious metals that will need replacement at least every decade, and the 'fun' factor has not been made affordable in EV's yet either.
        Alex740
        • 2 Years Ago
        @Hazdaz
        I would like to see a cleaner propulsion system as well but the ICE is far from dead and the EV has many very large hurdles before it becomes mainstream. I wouldn't be surprised if Tesla achieves that goal but even so our electrical infrastructure can't handle a nation of electric cars, charging time needs to be reduced to that of a fill up for wide consumer acceptance, we need charging places for those in urban areas without dedicated parking spots, and it's going to be a long time before any of this trickles down to the lower incomes of this country let alone poorer nations. Until all these and many other issues are solved the ICE is going to be around and we need creative short term solutions to make it more efficient and a mechanical one is even better for a trickle down effect to improving gas mileage in parts of the world that are a long way away from EVs. So no, the ICE will be around for a long time, possibly another century in wide use around the world so its more like the PC, not a typewriter
      SloopJohnB
      • 2 Years Ago
      Volvo is missing the boat in North America. Horsepower is the luxury issue, FWD is just not it. What I want is the performance of a V8 turbo, not a pusillanimous V6 turbo with what, 250hp? Yes, there are 350hp V6 turbos...but for the most part they are noisy and have a lot of vibration. Even the vaunted V6 Audi supercharged motor is harsh compared to their older 4.2 V8. And Audi has yet to master smooth start-stop technology (hint...call Toyota licensing). Volvo for the most part could be concentrating on RWD with KERS associated with front wheels. That would be F1 technology....
        Hello, Brian
        • 2 Years Ago
        @SloopJohnB
        Volvo is a small Swedish company that sells cars all over the world. They do not do special development for the NA market. I agree that horsepower is a luxury issue, but horsepower and luxury are not one in the same, or Dodge Challenger would be a luxury car, while an Audi A6 or BMW 5 Series 2.0 would not be. if you want the performance of a V8 Turbo, buy one...and pay the associated luxury price for it. Volvo does not currently aspire to make such a vehicle. They are just looking for ways to improve upon technology. If you think that the current Audi V6 turbos are noisy and have a lot of vibration, I have to say that you are exceptionally sensitive to vibration or you haven\'t actually driven one. While the old 3.2 had some vibration at tip-in, the 3.0 does not. Does it sound as sweet at the 4.2 at full bore? No. But nor is it louder.
        jessesrq
        • 2 Years Ago
        @SloopJohnB
        Environmental stewardship is just as important a luxury issue as absolutely power.
        no1bondfan
        • 2 Years Ago
        @SloopJohnB
        Pusillanimous means cowardly. Is that what you mean? I think you meant parsimonious, which means cheap. Not that it matters - your comment is getting down voted into oblivion pretty quickly anyway.
        • 2 Years Ago
        @SloopJohnB
        [blocked]
          Joeviocoe
          • 2 Years Ago
          So it is "Progressives" that cause high gasoline prices now? Not "Regressives" whose only solution has been "Drill baby Drill" to get a few more percent out of the domestic supply? Gasoline price is going up.... regardless of your political views. It is a scarce, non-renewable resource that is located mostly in foreign territory and subject to all manner of environmental and political crisis.
      • 2 Years Ago
      [blocked]
        k_m94
        • 2 Years Ago
        I think you lost your brain cells. Both of them.
        Alex740
        • 2 Years Ago
        It amazes me that someone can write so well yet be so limited in their ability to understand that the long road to reduced gasoline dependency is going to be full of a diverse selection of solutions to fit different needs. If you really think poor bean counting is the major factor holding Tesla's EVs back then you are completely out of touch with the majority of car shoppers. And FYI, Volvo is also selling the first diesel electric plug in hybrid hybrid car in the world and an all electric C30, luckily they understand the need to diversify better than you.
      EVSUPERHERO
      • 2 Years Ago
      Any thing to keep those, O2 sensors, exhaust pipes, catalytic converters, fuel air and oil filters, oil changes, belts, tensioners, 10 speed transmissions, turbos and now kers systems selling, anything to keep the inefficient, stinky, ICE and it's parts and maintenance revenue coming in. Perhaps they should add a washing machine in the engine compartment to make the wasteful ICE more appealing.
        Alex740
        • 2 Years Ago
        @EVSUPERHERO
        Things don't change overnight, eventually the scales will tip in favor of EVs or something else but the fact still remains, EVs aren't practical or even an option for a lot of us and this kind of ingenuity is what the rest of need until a better solution comes along.
        EZEE
        • 2 Years Ago
        @EVSUPERHERO
        Honda added a vacuum cleaner tot their van...
        goodoldgorr
        • 2 Years Ago
        @EVSUPERHERO
        What they don\'t do is to recover the waiste heat from the exhaust gasses. They can surrely divide a system where they heat a pressure boiler thru a heat exchanger with the heat from the exhaust gasses then spin a vapor generator and turn that to electricity. If a ice engine is 23% efficient, then there is 72% to recover. The trade off is added cost, added weight, added complication, less space, more mecanisms, difficulty to balance the entire system, so on. A tractor-trailer truck with a system like that might go from 7 mpg tp 14 mpg approx maybe more as there is a lot of heat waisted. that doesn\'t impede the turbo in the exhaust flow.
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