When one is trying to recover the energy of a moving vehicle or
object slowing down one has a problem.  The energy is proportional
to the square of the axle RPM so at first there is a lot of energy recovery and
braking effect. As the vehicle slows down the braking  energy rapidly falls off.
If a generator is directly connected to the wheel the braking effect of the
generator and energy recovery will fall off directly proportional to the RPM.
This is not what is required to stop as quick as possible. The conventional
brakes must be applied I suspect unless some way is found to rapidly increase
the load on the generator such as changing gear ratios and/or by electronic
means.  The same thing can be said about spinning up a flywheel to store the
braking energy. This device, invented in the early seventeen hundreds, might be
used to speed up the flywheel or generator as the vehicle comes to a stop
then is reset to wait for the next stop.

http://www.sailtexas.com/long.html
http://www.antique-pocket-watch.com/sinclair-harding.html

It will be very interesting next year when KERS is implemented in Formula 1
to see how the various teams achieve storing braking energy in a flywheel.

Paul Lamar


Paul,

If the drive train is influenced by the motor cum generator, the duty
cycle can be increased as the car slows down.  Accelerometers are solid
state and cheap to provide the necessary signal to maintain the desire
rate.  The control circuit fits on a quarter. Same challenge encountered
in slowing a low mass wind turbine rotor that has been hit with a micro
gust.  I do agree that flywheels are a more logical way to store energy
however. More efficient than say, electro chemical batteries. They can
be  electro-magnetically or mechanically coupled through the use of
ferro fluids that change viscosity depending on the small amount of
current applied to them. Back in the late 1970s flywheel energy storage
systems were all the rage and then suddenly the technology dropped from
sight.  Perhaps the researchers got side tracked by the PacMan computer
game craze:) Since then stable homogenous ferro magnetic fluids and air
bearings have been perfected along with certain ceramics that will turn
to (super heated?) dust if the outer Kevlar protective casing is
breached.

The amount of energy a flywheel can store is both amazing and
frightening.  This percieved danger may be the reason the technology was
not accepted readily.  Witness the damage a truck wheel and tire can
cause when it comes off and hits a house.  I wonder if the gyroscopic
effects influence the handling of the vehicle?


Doug in Japan