New system can reuse waste energy from idling trucks, buses

Scientists have found a way to capture waste energy from idling buses or refrigerated food delivery trucks, an advance that could reduce emissions and save fuel worth millions of dollars every year.
Researchers at the University of Waterloo in the US showed that the waste energy can be used to operate secondary systems, such as air conditioning or refrigeration units, when the vehicles are stopped and idling.
"An idling vehicle essentially operates at five per cent efficiency, meaning the vast majority of the fuel a bus or delivery truck uses when it is stopped is being wasted," said Amir Khajepour, a professor at Waterloo.

"By harnessing the energy a vehicle wastes as it is slowing down and redirecting it to a secondary battery system, these vehicles can be turned off without shutting off systems such as refrigeration and air conditioning units," Khajepour said.
As part of the study published in the journal Energy, researchers examined the various driving, braking and idling patterns of service vehicles.
Using computer models and engines hooked up to secondary battery systems in their lab, they then simulated the routes service vehicles followed to determine how best to collect and use waste energy.

The research focused on service vehicles, because unlike passenger vehicles, they have significant auxiliary power needs for systems like refrigeration, which account for a significant portion of the vehicles' total fuel consumption, researchers said.

"Given that most companies or governments cannot afford to transition their entire fleets over to cleaner vehicles all at once, this system could represent a cost-effective way to make current vehicles more fuel efficient in the short term," said Khajepour.
The money saved from fuel savings has the potential to pay for the new secondary power system in one-to-two years, he said.