KEMA 3D flywheel - exploded view
Exploded view of 3D counter-rotating KEMA flywheel system. By adopting a gyroscopic-like architecture, the author believes his flywheel can overcome the limitation of conventional, two dimensional designs.

3D Flywheel Hybrids

A proposal for a three dimensional, counter-rotating, kinetic electro-mechanical accumulator

By Mario Gottfried

One of the drawbacks preventing electric cars from being more attractive is the perception -- and the reality -- of time required to recharge the battery pack once the electric charge is depleted. This can take up to 8 hours depending on the depth of discharge and voltage available. If it were not for this irksome feature, EV’s would be more closely matched to compete with the performance of fuel engines in most tasks.

A new flywheel battery technology we are developing here in Mexico may solve this problem. We presented our 3D CR KEMA" (3 Dimensional Counter rotating, Kinetic Electro-Mechanical Accumulator) at the Electric Energy Storage Applications and Technologies ( EESAT) ) in San Francisco this past October. Ours was one of nine papers out of the 50 presented that focused on flywheel technology for energy storage. Other presenters looked at a broad cross-section of systems from lead acid batteries to large compressed air storage.

Hybrid-electric drive schemes have successfully shortened the charge-up period using engines, turbines, fuel cells, hydraulics, pneumatics and yes, flywheels. In Europe, the only hybrid electric bus made in series operates with a hefty portable flywheel for notable fuel savings. But still, fuel is used.

EV’s are necessary for the transportation of people and cargo, not only for health reasons, but basic good engineering efficiency. Fueled vehicles operate at around 15% net efficiency from the well head. Most HEV’s increase efficiency to under 25% when the utility generating station burns crude oil or gas. EV’s can operate around 35% efficient with hydrogen fuel cells, but they are expensive. When electricity is fuel sourced with nuclear, hydro or wind; the net efficiency climbs to under 50%.

So a competitive parameter of one (1) hour charge-up, to be sufficient for an in-town, in-traffic range of around 40 miles per vehicle/metric ton, with a +10 year life and installed at a reasonable price; the market place would be more agreeable to acceptable EV’s as their main form of transportation. Preferably, the vehicle would still have an engine for highways and as a back-up.

Our presentation at EESAT showed how a fast charge is possible with sets of smaller flywheels. The 3D CR KEMA system makes use of a set of 6 flywheels with electric motors that counter-rotate on three axis; using long life pin and jewel bearings, a spherical vacuum chamber, mass production type parts including in-series manufactured flywheels. We believe this approach promises to offer reliability, high energy density at a reasonable price.

Modern double cone portable flywheels are encouraging, as lighter flywheels are able to turn-up and absorb a heavy charge much quicker. This feature is also true with lighter stationary flywheels, which are able to absorb a full rated charge from the utility, then, when the vehicle is connected, feed a heavy charge into the flywheels in the EV. The overload in charging the vehicle from the grid is feasible at industrial installations; but domestic charging must be solved by adding longer loading time stationary flywheels.

The vehicle we are proposing is a normal standard front wheel drive car or van, where an electric rear wheel differential and flywheel assembly is fitted in half the trunk for operation as an EV wheel drive. The car remains as a normal gasoline engine drive vehicle. It is estimated, the owner will be able to pay back the EV conversion in about three years in fuel savings .

A nice innovation advantage of working with flywheels is the regenerative charge obtained while braking, over 50% recovery of the energy in the momentum of the vehicle. The net back up to original speed adds around 25%. So about a fifth more range is added in traffic conditions.

A major drawback of flywheel batteries is bursting, which can happen if the vehicle is involved in an abrupt accident. Fortunately, accidents can be avoided with proximity detectors on automatic brakes. Should a burst be inevitable, the burst can be directed into air bags away from the passengers.

"Portable" flywheels are not new, in fact, all engines use one, and they have been essential since the steam era. Even portable electric flywheels were used in the 20’s. What’s new is a safe design for speed electric flywheels in a gyro and precession-free frame, mounted on a differential wheel drive assembly to drive a +one ton car, for 40 miles, for many, many cycles for more than 10 years.

Editor's Note:
EV World welcomes other research papers and technology proposals similar to Mr. Gottfried's. If you have a paper you wish to publish to the academic/engineering community, we encourage you to submit it to EV World, the Internet's most widely read publication on 'green' sustainable transportation technology.

Times Article Viewed: 10269
Published: 22-Nov-2003


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