By: David Warren, Director of Sustainable Transportation, New Flyer
With increased focus on sustainability to protect the environment and preserve resources, the demand for zero-emission, battery-electric buses (BEBs) is rapidly increasing across North America. While California leads North America in deployments funded in part through “Cap and Trade” initiatives (a market based environmental regulation), Canadian deployments are expanding from east to west with major trials starting in Toronto and Vancouver.
As with any transformative technology, it’s useful to understand the basics of “How it Works” to fully appreciate and utilize the potential of battery-electric propulsion.
The three main components of a battery are: an electrolyte, an anode, and a cathode. An electrolyte provides the flow of electrical charge between the cathode and anode. Batteries store energy (kWh), and when grouped together, become the vehicle’s Energy Storage System (ESS). Once a load, such as an electric motor, is connected to the battery terminals, a chemical reaction occurs to create a flow of electricity from the battery to the motor.
An important consideration for the energy storage system is the recharge capability of lithium-ion batteries. There are two forms of battery recharging:
- In-motion regenerative (“regen”) power when the vehicle decelerates, and
- Power transferred from an off-board charger such as a depot plug-in charger or on-route rapid charger.
Both types of recharging transfer electricity to battery cells, to create a reverse chemical reaction within the battery that restores energy.
The battery charge and discharge process is repeated thousands of times throughout the life of a BEB. The cycle consists of:
- Chemical energy stored in the lithium-ion battery cells,
- Energy released from the battery as electricity,
- Energy converted to kinetic energy through the motor to power the wheels for propulsion and power electric accessories,
- Recovering kinetic energy from the motor (turned generator) when decelerating,
- Causing a reverse chemical reaction to partially recharge the battery cells, and finally,
- Recharging the batteries using an off-board plug-in or overhead charger to create a reverse chemical reaction to restore the battery cell to full state-of-charge.
Through repetitive battery cycling, rechargeable batteries eventually experience capacity fade. Battery engineers must select the ideal chemistry and manufacturing processes to achieve long-lasting and reliable performance in the harshest environmental conditions. New Flyer chooses Nickel Manganese Cobalt (NMC), the chemistry of choice by leading vehicle manufacturers worldwide.
Battery technology improvements, as illustrated in Figure 1, continue to allow battery-electric buses to become more affordable with enhanced range. New Flyer has experienced an average 12% annual improvement in battery specific energy over the past 5 years, and future improvements are certain.
Figure 1 - Battery Technology Improvements
Simply stated, New Flyer believes it’s bright ahead for our zero-emission, battery-electric Xcelsior CHARGE™ buses. We’re proud of our ongoing technology investments and the innovation throughout our entire organization, completed by the success of our battery-electric deployments in Winnipeg; made possible through talented forward-thinking Canadian partners. New Flyer and Motor Coach Industries (MCI), both subsidiaries of NFI Group Inc., are devoted to transformative electric-mobility technology communities throughout North America can rely on. To learn more, visit www.newflyer.com.