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On Thu, May 03, 2007 at 06:13:43PM +1200, Russell McMahon wrote:
> I'll avoid putting this in EE :-)
> 
> Taking power from cars while they are braking may make sense.
> But, anything that generates power from a car's slipstream on a level 
> motorway is liable to be a bad idea overall.
> 
> This man doesn't think so:
> 
> > http://www.metropolismag.com/cda/story.php?artid=2466

You know, I'm not so sure about that... Essentially the cars normally
would push a pile of air off to the side and above them and they drive.
This air would normally dissipate it's energy by friction from
chaotically mixing in the case of the barriers. What that invention
does, from the cars perspective, is create a barrier with perforations,
something closer to not having the barrier there at all.

So compared to having a plain concrete barrier, I can see it actually
saving energy, as well as doing something usefull with energy that would
be otherwise turned into waste heat.

That said, I'm sure compared to not having the barrier there at all
there might be a net loss, but this is where tricky areodynamics get
into play, what's intuitively a good idea might not be. Only way to know
for sure it to go out and simulate and measure the actual effect.

Besides, maintaining all those moving parts in the middle of a busy
highway can't be much fun...

- -- 
http://petertodd.ca
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