msb@lsuc.UUCP (Mark Brader) (04/03/85)
I'm reposting this article because a bug truncated its beginning at some local sites, so it may be incomplete on much of the network. (I triggered the bug by posting it with "References:" in the header, instead of "References: " or omitting the references line. See net.news.b -- in a few days, I hope.) I posted it to net.consumers and net.physics because these groups seem to have the readers most likely to be interested. There are several methods extant for improving a vehicle's energy efficiency by storing the kinetic energy lost when braking, somehow, and retrieving it when the vehicle starts up again. The most successful to date seems to be for the vehicle to carry a flywheel. A new and promising idea is now being installed on its first test vehicle. The energy is stored as the potential energy of a compressed volume of gas -- a gaseous spring, if you like. The physical arrangement has a cylinder with one end closed and a flexible barrier across the middle, thus enclosing the gas permanently. The other half is filled with hydraulic fluid. The transformation between kinetic energy of the vehicle and potential energy of the gas is thus achieved by a reversible hydraulic pump. This scheme, called a gas-liquid accumulator, was invented by Bill Heggie and developed by a team under Tony Davies, both of (Canada's) National Research Council. One of the things that should enhance its practicality is that the accumulator will be computer-controlled. Since city buses do more stopping and starting than almost anything else, they would benefit most from this. (They'd save on brake lining replacements as well as fuel.) So the test vehicle is a bus. The NRC has bought it from the city of Mississauga (near Toronto), and if preliminary tests at the NRC labs in Ottawa go well, it will be running in ordinary service back in Mississauga early this fall. My reference for all this is Jack Miller's column in yesterday's Toronto Star. Mark Brader
brooks@lll-crg.ARPA (Eugene D. Brooks III) (04/05/85)
Electric forklifts, used inside buildings, have used an energy conservation scheme for some time. The technique is electric braking. When the brake pedal is pressed the drive motor is run in generator mode charging the battery. The rate of charge is proportional to the pedal stroke. Once the pedal is pressed far enough the mechanical brakes are finally engaged.