Niskayuna, New York – GE Global Research has successfully demonstrated a zero-tailpipe-emissions transit bus that pairs an energy-dense sodium battery with a high-power lithium battery. The breakthrough could help accelerate the electrification of bus fleets, delivery trucks and other larger, heavy-duty vehicle fleets by combining the best qualities of each battery for cost efficiency.
The research is being done as part of a US$13 million research project GE is engaged in with the Federal Transit Administration and Northeast Advanced Vehicle Consortium, funded under the National Fuel Cell Bus Program.
“Public transit and delivery service providers recognize the importance and benefits of transitioning to an electric fleet, but are looking for cost-effective solutions to make that possible,” said Lembit Salasoo, senior electrical engineer and principal investigator on the project. “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.”
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 (160 kilometres) per day. Enabling more of these buses to transit to an all-electric platform would dramatically reduce fuel consumption and CO2 emissions.
Lithium batteries provide a lot of power for acceleration but are not optimized to store energy for driving range, while sodium batteries store large amounts of energy but are less optimized for power. In the hybrid transit bus demonstration, the lithium battery is focused on the high-power acceleration and braking, while the sodium battery provides an even electric power flow to extend the bus range.
The system can also reduce the battery cost by up to 20 per cent, compared to a single battery system for buses or delivery trucks that require significant power and energy storage capacity. The key cost advantage of a dual system is that it provides flexibility to integrate less-expensive battery chemistry without having to increase the size of the battery to address the vehicle’s power and energy storage needs. A single battery system would require a larger and more expensive battery to achieve the same result.