Re: harvesting waste power in carparks


bill wrote:
Fran wrote:
I was up at my local shopping centre the other day, and the place was
packed. I'm not sure how many cars were in this large 5+ level-carpark,

but if there were fewer than 5000 cars in there at the time, with 300
driving about looking for spots or trying to leave, I'd be surprised.

On each level in this carpark, and on the ramps between levels there
are speed humps -- lots of them -- the aim of which is to keep speeds
down to about 15kph (roughly 9 mph US). At the time, the volume of
traffic was doing this comfortably enough, but of course, during
shoulder periods speeds can increase. In the course of finding a spot
and then subsequently leaving, I crossed 45.

It occurred to me that these humps probably do quite a bit of
cumulative damage to the front ends of vehicles -- the humps themselves

are often scarred and gouged from people who for some reason or another

were travelling too fast when they reached them but even those who do
the right thing are undoubtedly putting more stress on their ball
joints, axles, shock absorbers etc. Of course, you also end up using
energy fairly inefficiently, braking far too much, having the engine
turning over at a higher averagae rate than you would if there were no
speed hump.

But what if these humps were replaced with something like a see-saw
with a slightly convex underside, about 3.6m/12 feet in length, placed
over some medium capable of being compressed -- say a gel, or even
water? Then, the momentum or "work" taken from the vehicle could be
converted by hydraulic action into the expansion of a series of pistons

connected to a crank and thereafter a turbine to generate electricity.

The owner of the vehicle would lose as much momentum (and perhaps more)

going into the see saw device but because the initial impact (all else
being equal) would be smaller, and because the device would dissipate
some of the force of the impact to the medium, the damage to the front
end
would be lowered and vehicles could afford to enter at slightly higher
speed
reducing the braking required and thus avoiding cumulative recurrent
costs and even fuel cost.

If the system could work this way, then everyone would be ahead -- the
carpark gets useful energy to sell/use, and vehicle owners get
comparatively lower costs. The busier the carpark, the more energy
you'd harvest, and since this is peak time, the match is a good one. It

even occurred to me that some time well into the future, when EVs were
the rule, one could plu in one's vehicle and trickly charge a battery
from power generated by these speed pumps, in effect, recovering some
of the energy that they've put in.

Is this a viable idea? Assuming vehicles are on average about a ton,
and are entering these devices, on average, at about 15kph, how much
electricity could reasonably be harvested?

fill the speed bump with water, make it out of a material that
remembers it's shape so that when there is no car on it it exerts a
suction on the water behind it, install 2 check valves and you've got a
diaphragm pump. use it to move water to a water tower on the roof.

And attach some sort of small scale equivalent of a hydro plant you
mean? Wouldn't that be less efficient at harvesting power (though
perhaps better at *storing* it) than simply applying the force more or
less directly to a turbine or flywheel driven by the pressure of the
attached medium being compressed? After all, you waste some energy
overcoming gravity don't you? And then there's the cost of the attached
system -- which, unless it's less than the cost of whatever the
aggregate of those at the see saws could be, would also be a net cost.

Fran

.

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