On 05/30/2011 06:37 PM, Jim Wilkins wrote:
On May 30, 9:01 pm, (dan) wrote:
Tim Wescott wrote in
...
Don't forget about the heat. That kills the efficiency of most air
powered cars. But as short term storage in re-gen braking, it may be
workable. But I'll wait and see.
Dan H.

The energy recovered by regenerative braking helps you get back up to
speed after the light turns green, nothing more.

Apparently that energy can be a pretty substantial fraction of the
energy used in city driving. So your 'nothing more' is warranted, but
the energy saving isn't to be sneezed at.

And no -- I can't quote proportions to you. Wish I could. It's
probably on the web someplace. In fact, there's probably several
different contradictory sets on the web*.

One thing about using compressed air for regenerative braking -- if you
use the compressed air while it's still hot you'll recover more energy
than you do from cold compressed air like you'd get in a shop. All it'd
take would be a bit of thermal insulation on the tank, or perhaps not
even that.

* If nothing else, it depends on the driver. I have a friend who
accelerates like a drag racer out of stop lights, then curses and stomps
on the brakes at the next red. This in downtown Portland Oregon, where
they time all the lights and if you go a steady speed a bit under the
limit then you hit all the lights green. _She's_ gonna benefit from
regenerative braking a whole bunch more than my wife or I, who like the
challenge of seeing how many greens we can hit when we know the lights
are timed.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html