New Life For “Green Weenie” Electric Locomotive
Railway
giant Norfolk Southern launched its ambitious all-electric NS 999 locomotive
project in 2007, and since then it has been chugging steadily, if slowly,
along. The pace has been picking up of late, though. At a recent trade
conference, the company and its partner, Axion Power, documented improvements
in the locomotive’s battery management system that leapfrogs the technology
into the next generation.
Our
sister site, Gas2.org, first began covering the NS 999 prototype when it
rolled onto the tracks in 2009. Dubbed the “green weenie” by rail
fans, the all-electric locomotive
sported 1,080 12-volt lead-acid batteries. If that rings a bell, look
under the hood of your car and you’ll see pretty much the same kind of battery.
Well,
that was then, this is now.
Next-Generation Batteries For An Electric Locomotive
 |
NS
999 electric locomotive courtesy of Hampton Roads Partnership
|
There
have been some promising tweaks to lead-acid batteries,
but the difference occurred earlier this year, when NS 999 switched over to a
new lead-carbon battery developed by Axion Power.
The
positive electrode follows standard procedure for a conventional lead-acid
battery, being composed of lead dioxide. The negative electrode, however, subs
in a supercapacitor made of activated carbon for the sponge lead found in a
conventional battery, hence the moniker PbC® battery.
Axion
explains how the high surface area of its specially formulated activated carbon
gets the job done:
In conventional lead acid batteries the concentration of acid changes from being very concentrated in the charged state to somewhat dilute in the discharged state as the acid is converted to water. In contrast, the PbC® battery stores H+ in the negative electrode in the fully charges state which move to the positive electrode during discharge where they are neutralized to form water. The result is reduced acid concentration swings from the charged to discharged state which reduces grid corrosion on the positive electrode and leads to longer life of the positive electrode.
At
the 7th Annual ASME (American Society of Mechanical Engineers) Rail
Transportation Conference in Pennsylvania earlier this month, Axion and Norfolk
Southern provided an update on NS 999, comparing
the new battery system to the earlier valve-regulated lead-acid battery system.
The
report didn’t pull any punches, critiquing the previous iteration of NS 999 for
its unwieldy battery management and battery packaging systems, which piled on
maintenance costs.
PbC® batteries have a unique charging curve, known as “concave down, increasing,” which allows the batteries to self-equalize in strings. This characteristic of PbC® batteries provides for simpler battery management and reduced maintenance charging, while increasing the usable energy available to the string.
We Built This Zero Emission Locomotive!
Before
Axion came on board, in its initial stages NS 999 was developed in partnership
with Penn State University with an assist from Department of Energy funding
(Norfolk Southern has also received $105 million in Recovery Act
funding to improve the critical Crescent Corridor freight network, btw).
The
Department of Energy also awarded Axion $150,000 last
year, to help the company kickstart a commercialization plan for the PbC®
battery.
