An old failure, new success of a Renewable Energy Source: The gravity.
Detailed info is in short youtube vid.s (30 sec each, and similar all)
here:
mgulk..
Future Energy : The Gravity, For Free...
http://www.youtube.com/watch?v=SOTlogoPYZs
Energy from gravity: an affordable self popelled wheel chair...
www.youtube.com/watch?v=GlR2VEMXMkA
Energy from gravity (pure mechanical) ...
www.youtube.com/watch?v=Tf7urAWuiu8
The video provides no useful information to understand how such a
device works.
We know a wheel chair will roll down hill. That's gravity working. To
go anywhere else you have to add energy. I can conceive of a device
that would allow a person to use their arms to lift a weight and build
up energy in some storage device. If they could do that, they could
push the wheel instead. That would be free. We know that batteries are
great for storing energy for wheelchairs and the user doesn't have to
be able to do anything except push a toggle on the arm. I don't think
there will be much savings by expecting disabled people to generate
their own power.