[Lab] regenerative braking

Richard Guy Briggs rgb at tricolour.net
Wed Sep 14 10:46:39 EDT 2011

On Mon, Sep 12, 2011 at 05:06:23PM -0400, Darcy Whyte wrote:
> I'm figuring that it will only work in some strange circumstances for cars
> (like if you live on a mountain).
> http://incandescent.ca/a-case-for-regenerative-braking/
> What do you think?

It has some potential.  Solar cars in the North American rayces use
regenerative braking in their systems since there are enough starts,
stops, hills and speed limits that make it worthwhile.  The Australian
rayce doesn't need it since there is one traffic light in the 3000 km
course route between Darwin and Adelaide, in Alice Springs, and there
are very few hills of any note, so the regenerative braking parts are
extra weight and complexity that work against the efficiency of a solar

> The reason I dont' think it will work is that it's based on bad
> driving in the first place.

I do agree strongly with you here.

> For instance when I see a red light (or anticipate it), I get off the
> gas and start coasting. I arrive at the light just when it's green. So
> I never piled on the gas to get to the red light, then hit the break,
> then had to get back up to speed. If you're driving properly in the
> first place you're not going to waste enough energy to recover.

Danish transplant to Australia adventurer Hans Tholstrup did many tests
of this theory including circumnavigation of the continent of Australia
and managed to demonstrate that driver behaviour had a very significant
effect on energy economy and pollution.

> To make it work for me, I'd have to intentionally accelerate towards a
> red light so I could then use the brakes.

I mostly agree with you, but I do see some use.

I recall an article in IEEE Spectrum about 20 years ago about an
electro-mechanical battery consisting of a carbon-fibre flywheel running
on magnetic bearings in a vacuum at a speed of several hundred thousand
RPM.  There were two clamped together to avoid gyroscopic effects.  The
reason for the carbon fibre and high rotational speed is to get the
energy density up with total mass down.  I probably still have the
article here somewhere...

	slainte mhath, RGB

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