“With the cost of the battery remaining a principal hurdle, a dual battery system could bring these costs down and help accelerate the electric revolution for bus and delivery truck fleets representing hundreds of thousands of vehicles.” –Lembit Salasoo, senior electrical engineer and principal investigator for GE Global Research’s hybrid bus project.
So late last week, GE rolled out what it dubs a potential “breakthrough” hybrid propulsion system that it thinks could help accelerate the electrification of bus fleets, delivery trucks and other larger, heavy-duty vehicle fleets.
The key to this new hybrid package is what GE calls a “dual battery system” that pairs a high-energy density sodium battery with a high-power lithium battery. GE at least thinks a dual system with high power and high energy storage capacity could achieve the optimal electric driving range and acceleration requirements at a more practical size scale and cost for larger vehicles.
“Public transit and delivery service providers … are looking for cost-effective solutions to make the transition to electric vehicles possible,” said Lembit Salasoo, senior electrical engineer and principal investigator for GE Global Research’s hybrid bus project.
[As you may have surmised, GE is trying this new technological wonder on transit buses first – and you can catch a quick glimpse of it in operation below.]
“With the cost of the battery remaining a principal hurdle, a dual battery system could bring these costs down and help accelerate the electric revolution for bus and delivery truck fleets representing hundreds of thousands of vehicles,” Salasoo said.
The research, by the way, is being conducted as part of a $13 million research project between GE, the Federal Transit Administration (FTA) and Northeast Advanced Vehicle Consortium, funded under the National Fuel Cell Bus Program.
GE is trying this out on buses for a good reason, too – they tend to have the lowest amount of daily travel for vehicles of this size. The company noted that many of the 843,000 buses registered in the U.S. (including most of the 63,000 transit buses and 480,000 school buses) travel less than 100 miles per day, so enabling more of these buses to transition to an all-electric, zero emissions platform would dramatically reduce CO2 emissions and petroleum fuel consumption., it noted.
Now, why use a “dual battery” system? GE explained that most types of batteries today come with a trade-off between power and energy storage. For example, lithium batteries, provide a lot of power for acceleration, but are not optimized to store energy for driving range, while sodium batteries are on the opposite side of the spectrum – they store large amounts of energy, but are less optimized for power.
Thus, GE’s dual battery combines the best attributes of both chemistries into a single system.
In its hybrid transit bus demonstration, GE said the lithium battery focused on the high power acceleration and braking, while the sodium battery provided an even electric power flow to extend the bus range – allowing each type of battery to do what it does best.
In addition to optimizing performance, a dual system can reduce the cost of a battery by up to 20% compared to a single battery system for vehicle applications like transit buses and delivery trucks that require significant power and energy storage capacity, Salasoo pointed out.
So a key cost advantage of a dual battery system (and fleet managers really focus on the cost metrics, too, as we all know SO very well) is that it provides flexibility to integrate less expensive battery chemistries without having to increase the size of the battery to address a vehicle’s power and energy storage needs. By contrast, a single battery system would require a more costly scale up in the size of the battery to achieve the same result, Salasoo noted.
So, is this a “silver bullet” for the complex energy and operational needs of heavy-duty commercial vehicles and buses? Not at the moment, I think, for issues concerning such a systems impact on vehicle weight, the price tag, and the expected return on investment (ROI) all need to be worked out, no doubt. But this could be a step in the right direction.