GE’s ecomagination.com publication reports that GE engineers have begun testing a transit bus equipped with a new hybrid energy system integrating GE’s Durathon sodium-halide battery (earlier post), a lithium-ion battery and a hydrogen fuel cell.
With this system, we are bringing together a battery that supplies power, a battery that provides a lower amount of energy longer and a fuel cell that creates the base load of electricity to operate the bus. It’s all centered on the system that manages power, energy and the fuel cell all in an intelligent way.—Tim Richter, Systems Engineer in the Electric Propulsion Systems Lab at GE Global Research
Current fuel-cell-powered buses must include batteries to provide power for acceleration. Up to today, though, hybrid systems have not run as efficiently as they can because they use lithium-based batteries, which often produce more energy than needed and drain quickly. This limits a bus’s range to around 50 miles and increases costs by requiring larger, more expensive fuel cells.
GE has been exploring ways to synergize the benefits of its sodium-halide Durathon technology, which can store a large quantity of energy but isn’t optimized for power, with power-optimized lithium batteries and hydrogen fuel cells.
Richter says the new management system, GE’s Ecomagination-qualified Multi-Energy High Voltage Energy Management Architecture, has been created to manage the bus’s power sources and provide the energy it needs when it needs it.
The energy management technology is a combination of hardware and software all in one box. DC converters boost low-voltage electricity to power the bus’s motor while the software controls the converters to get the best out of the different sources of energy.
Richter suggests that this design approach will allow engineers to scale back the size of costly hydrogen fuel cells, potentially lowering a bus’s initial cost by 50%. Better power management also means long-term savings in operating the vehicle.