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
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.
The new PbC® batteries were tested on the Norfolk Southern Hybrid Locomotive Simulator, and the results look promising. According to the report:
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.