• Jun 2nd 2011 at 9:50AM
  • 25
Volvo KERS system – Click above to watch video after the jump

Volvo has received a grant of 6.57 million Swedish kronor ($1.05 million U.S. at today's exchange rate) from Swedish Energy Agency to jointly develop and test a flywheel kinetic energy recovery system (KERS) with SKF, a Swedish bearing company founded in 1907.

The system, called Flywheel KERS, is fitted to a vehicle's rear axle. During deceleration, braking energy causes the flywheel to spin at speeds of up to 60,000 revolutions per minute. When the vehicle accelerates, the flywheel's rotational energy is transferred to the vehicle's rear wheels via a specially designed, Torotrak continuously variable transmission.

According to Derek Crabb, vice president of Volvo's powertrain engineering division, Flywheel KERS has the potential to reduce fuel consumption by up to 20 percent while boosting a four-cylinder engine's performance to a level that matches a typical six-cylinder mill. Tests in a Volvo vehicle will begin in the second half of 2011. Hit the jump to catch a brief video of Volvo's Flywheel KERS system.

[Source: Volvo]

Show full PR text
Volvo Car Corporation tests flywheel technology
- cuts fuel consumption with up to 20 percent


A light, cheap and very eco-efficient solution that makes a four-cylinder engine feel like a six at the same time as fuel consumption drops with up to 20 percent. This autumn, Volvo Car Corporation will be one of the world's first car makers to test the potential of flywheel technology on public roads. The company has received a grant of 6.57 million Swedish kronor from the Swedish Energy Agency for developing next-generation technology for kinetic recovery of braking energy in a joint project together with Volvo Powertrain and SKF.

"Our aim is to develop a complete system for kinetic energy recovery. Tests in a Volvo car will get under way in the second half of 2011. This technology has the potential for reducing fuel consumption by up to 20 percent. What is more, it gives the driver an extra horsepower boost, giving a four-cylinder engine acceleration like a six-cylinder unit," relates Derek Crabb, Vice President VCC Powertrain Engineering.

60,000 revs per minute
The new 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 the braking begins. The energy in the flywheel can be used to accelerate the vehicle when it is time to move off once again, or to power the vehicle once it reaches cruising speed.

"The flywheel's stored energy is sufficient to power the car for short periods. However, this has a major impact on fuel consumption. Our calculations indicate that the combustion engine will be able to be turned off 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 as well as 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 boost of 80 horsepower, and thanks to the swift torque build-up this translates into rapid acceleration, cutting 0 to 100 km/h figures significantly.

Carbon fibre for a lightweight and compact solution
Flywheel propulsion assistance was tested in a Volvo 240 already 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 alternative.

The flywheel that Volvo Car Corporation will use in its test car is made of carbon fibre. It weighs about six kilograms and has a diameter of 20 centimetres. The carbon fibre wheel spins in a vacuum to minimise frictional losses.

"We are not the first manufacturer to test flywheel technology. But nobody else has applied it to the rear axle of a car fitted with a combustion engine driving the front wheels. If the tests and technical development go as planned, we expect cars with flywheel technology to reach the showrooms within a few years," says Derek Crabb. He concludes: "The flywheel technology is relatively cheap. It can be used in a much larger volume of our cars than top-of-the-line technology such as the plug-in hybrid. This means that it has potential to play a major role in our CO2-cutting DRIVe Towards Zero strategy."


I'm reporting this comment as:

Reported comments and users are reviewed by Autoblog staff 24 hours a day, seven days a week to determine whether they violate Community Guideline. Accounts are penalized for Community Guidelines violations and serious or repeated violations can lead to account termination.


    • 1 Second Ago
  • 25 Comments
      Doug
      • 4 Years Ago
      I'm curious what the mass and rotational moment of inertia of that flywheel are.
      Andrew Richard Rose
      • 4 Years Ago
      Looks terribly complicated and possibly dangerous , the thought of a great hunk of steel coming loose at 60000 revs does not bear thinking about ! Still anything to avoid going down the electric route !
        • 4 Years Ago
        @Andrew Richard Rose
        Contrary to a lot of belief on this site, electric is not the only way to go. These engineers know far more about how to make cars than we do. Perhaps instead of playing armchair quarterback we should either vote with our dollars, kronor, euros, etc., or maybe we should let the engineers design things since they know how. And by all means, if any of us can do it better, then put up or shut up.
          sirvixisvexed
          • 4 Years Ago
          The truth! It burns! It burns!
          sirvixisvexed
          • 4 Years Ago
          If it's something new like this, people will be very interested in the strength and longevity tests, and won't be convinced to buy one until they see them, sort of like how the in depth volt engineering videos turned around skeptics and 'what if's'. A flywheel spinning in a vacuum at 60,000 rpm sounds no more dangerous than introducing gasoline and fire to make a flywheel turn. If it's efficient, and what people want, and proven, and not super costly, people will use it. I don't think we enough enough yet to say whats wrong with it.
          sirvixisvexed
          • 4 Years Ago
          Wow, haha, meant to say, I don't think we have enough information yet to say what's wrong with it.
        • 4 Years Ago
        @Andrew Richard Rose
        The Volvo flywheel will be made from carbon fiber instead of steel for maximum efficiency. The flywheel measures a diameter of 20cm and weighs 13 pounds. It also spins in a vacuum to minimize losses. http://www.dailytech.com/Volvo+to+Test+KERS+Flywheel+Tech+with+Grant+from+Swedish+Government/article21776.htm
        Chris M
        • 4 Years Ago
        @Andrew Richard Rose
        This flywheel isn't steel, it's made of carbon fiber, which is much stronger, and failure results in a lot of fluffy fibers rather than jagged hunks of flying steel. Spinning in a vacuum reduces aerodynamic friction, but adds friction and wear from the vacuum seal necessary in this mechanical version. Some have proposed using a motor/generator enclosed with the flywheel which eliminates the vacuum seal friction - and greatly reduces the frictional loss inherent in that Torotrak variable speed transmission. Not entirely convinced it's any better than a battery electric KERS. We'll see for sure after testing is completed.
        Snoopy
        • 4 Years Ago
        @Andrew Richard Rose
        Well, then you should be glad Volvo's developing this one. A company so set on safety wouldn't let something that could come loose that easily out of their plant doors.
        Dan Frederiksen
        • 4 Years Ago
        @Andrew Richard Rose
        word
      tantareanujellob
      • 4 Years Ago
      More government waste. Volvo would never its own money in this garbage.
      Dan Frederiksen
      • 4 Years Ago
      try batteries Volvo. pathetic
        dellrio
        • 4 Years Ago
        @Dan Frederiksen
        How are batteries, motors and computer controllers more efficient than direct purposing of kinetic energy? You can regain much more direct kinetic energy in a flywheel than you can by running a motor backwards to charge a battery (about 30% effiecent) then storing the energy and using a motor (about 90% efficient) to power the axel back up. No toxic materials, no rare earth magnet motors. KERS is very economical, and likely cheaper to implement once scaled up. Dan - you have a 1 track mind - electric cars alone WILL NOT save the planet.
          Dave D
          • 4 Years Ago
          @dellrio
          dellrio, Where are you getting your "facts" LOL An electric motor runs the same efficiency both ways....they are simply changing the polarity so energy is flowing the other way.
          Chris M
          • 4 Years Ago
          @dellrio
          Martin Eberhardt has stated a 85% efficiency of energy storage for charger and batteries. Figuring 90% for generator, 85% for battery storage, and 90% for electric motor, overall regen efficiency would be about 69%. Don't know the efficiency of the Torotrak variable speed transmission, but since it's a friction drive system, frictional losses are probably substantial, particularly at high speeds. While this mechanical system might be less expensive than the electric equivalent (questionable, considering the mechanical complexity and demanding engineering of the flywheel), it would certainly experience more wear and require more maintenance over it's lifespan. Battery electric KERS has other advantages - the energy density of batteries is higher than for flywheels which means less weight and/or greater energy storage, it allows much greater flexibility in component placement, and the standby losses are far less for batteries than for flywheels.
          tantareanujellob
          • 4 Years Ago
          @dellrio
          "How are batteries, motors and computer controllers more efficient than direct purposing of kinetic energy?" Solid state vs a mechanical system. Look it up some time.
          sandos
          • 4 Years Ago
          @dellrio
          30% efficiency? I would like to see a citation for that, sounds extremely low!
        skierpage
        • 4 Years Ago
        @Dan Frederiksen
        Volvo is trying batteries. The press release reveals the motivation: "The flywheel technology is relatively cheap. It can be used in a much larger volume of our cars than top-of-the-line technology such as the plug-in hybrid." So this is unproven complex high-tech stuff Volvo hopes to introduce at the *low end*!? I think the companies that implement the whole electric spectrum, micro hybrid (stop-start) -> mild hybrid -> full hybrid -> plug-in hybrid, for *all* their cars will benefit from volume cost reductions, and all the alternative engineering approaches will struggle.
      • 3 Years Ago
      This is a great news. Adapting mechanical KERS in automobile industry will bring about big impact. It is cheaper and even more effective than HEVs. First may not be perfect, but there is a saying that "a good start is the halfway to success". If anyone is interested in reading more about its potentials in automotive applications, take a look at my paper that I wrote for one of my course material. Link: http://wooseung.wordpress.com/2012/07/15/kinetic-energy-recovery-system-kers/
        • 2 Years Ago
        I'm doing a case study for an academic work. will you could provide the paper (http://wooseung.wordpress.com/2012/07/15/kinetic-energy-recovery-system-kers/) for my email? i canot download it!! canhas_bawl@hotmail.com Thank you
      Dave D
      • 4 Years Ago
      We had a lively debate over on GCC about whether flywheels or batteries/supercaps were better. Seems like Volvo should spend their own money on this one until they can prove it's a better system than others and not sure why taxpayers should be helping Volvo on this one (even over there).
        • 4 Years Ago
        @Dave D
        Nows this I agree with. But it shouldn't matter what propulsion system. Tax payers shouldn't be on the hook for it.
      S C
      • 4 Years Ago
      Similar in concept to hydraulic launch assist....store energy from braking to use in acceleration.
      • 4 Years Ago
      That only catches the energy from rear wheels.
      Matt
      • 4 Years Ago
      Any body got the UPC code for that KERS system? I forgot my PIN number.
    • Load More Comments