Axion Power International (New Castle, PA), which develops batteries called PbC (lead-acid-carbon) for large transportation use, has teamed with Norfolk Southern, one of the largest railways in the U.S. The plan is to develop a battery management system and technologies to allow trains to use regenerative braking to recover and store power to be used to remove the diesel generator (or cabling/third-rail) from train electrification.
Most trains now, of course, are diesel-electric hybrids which are driven by electric motors whose power is derived from diesel-burning generators. This allows a relatively high level of efficiency, with trains capable of 480 ton-miles per gallon.
Axion hopes that by using their PbC batteries, which are capable of taking large amounts of electricity very quickly and storing it as well as retaining a long cycle life, they can fully electrify trains. An all-electric train is not new, of course, and there are many still in use, though not generally for freight. Most commuter trains (light rail, subways, etc.) are electric-only, but require a third rail or overhead wire to power them. Axion wants to replace the engines in current freight locomotives with batteries so no third rail or overhead cabling is required.
The PbC battery works in a way similar to a standard car or truck battery, though on a larger and more complex scale. It is asymetrically supercapacitive and includes carbon in the usual lead-acid mix. This allows the battery to absorb huge amounts of power in a very short amount of time – perfect for longer-term storage of power from short-term regenerative braking. So whenever the engine slows the train, power is regenerated and stored in the batteries.
Currently, most of the braking that trains do to slow or stop is done through resistance in the electric motors. Physical brakes are used only in emergencies or at the end to finally stop the train. Although the majority of the slowing and stopping takes place through the electric motors, for now that energy is not recaptured (regenerated) and is merely lost as heat. That’s what Axion wants to change.
“The key will be developing a battery management system that is robust, safe, dependable and easy to maintain,” says Axion Power Chairman and CEO ThomasGranville. “We are highly confident, based on our ongoing work, that this system can be successfully demonstrated in a fairly short time frame. We are, of course, pleased and delighted to be working with Norfolk Southern, an industry leader and a trail-blazer in hybrid locomotives.”