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Flywheel Hybrids

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File:Example of cylindrical flywheel rotor assembly.png

A new hybrid vehicle technology based on flywheel storage of energy as opposed to battery storage. Several companies including Drive-train Innovations, SKF, Bosch, CCM and Punch Power Train are sponsoring the development of the power-train technology as a joint venture with Eindhoven University. The system has been implemented in an operational hybrid vehicle since last September, but the electronic control system that regulates when the system uses flywheel energy versus engine power is still being developed.

A flywheel stores energy by increasing the rotation of rotor suspended in a vacuum chamber to reduce friction. As energy is drawn from the system, the rotational speed of the rotor decreases and the speed increases when energy is added to the system. The system is based on a clutch that rotates through the vacuum chamber. Flywheel technology is more efficient than battery energy storage.

Source: IEEE and Wikipedia/wiki/Flywheel_energy_storage

The Prof: see “New Twists in Turning Hot Air Into Horsepower,” Lindsay Brooke, NYTimes, May 9, 2014. Formula One racing has used this system (KERS or Kinetic Energy Recovery System) but is dropping it in favor of a turbo system that uses excess energy (rather than a wastegate valve) to drive a generator, while the generator in turn can drive the turbo to offset lag. This delivers better performance than KERS.


  1. Flywheels are limited in their storage capacity – capturing energy to brake going into a stoplight, accelerating away afterwards. That’s not to be sneezed at, since keeping a vehicle moving requires little energy compared to adding speed. So what will matter is how much mass a flywheel requires, how robust it is with inexpensive materials (early systems tended to fly apart) and of course the cost of linking it with some sort of clutch and gearing. Bigger systems add mass and act as gyroscopes. Finally, a rival technology is a belt-alternator/starter system, which is already on the road. The initial systems were for just turning over the engine from a full stop, but now they can add energy up to speeds of 30 mph and now maybe more – and you need an alternator anyway, though more robust belts/pulleys, power controls and a beefier battery add cost and weight.

    May 16, 2014
  2. […] F1 certainly has a great deal of technology to offer the passenger car market, including its KERS technology. The future is certainly bright for racing’s connection to the consumer car […]

    August 28, 2014

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