New York City’s Department of Sanitation has been testing an engine stop-start system with impressive fuel savings.
DSNY has been testing hybrid-drive powertrains in its trash-collection trucks. But the anticipated fuel savings have not materialized as they have in other locales. Savings are only 10-15% with hydraulic hybrids, probably because speed between the many stops is not great enough to build kinetic energy that can be recaptured during braking.
But with the extensive amount of time the fleet’s trucks spend idling at stop lights and in traffic backups, a new stop-start technology is showing a 30-40% improvement in fuel efficiency, says Rocco DiRicco, DSNY’s deputy commissioner, support services. “It’s simple, with almost no weight. We think it’s close to being the silver bullet for our front-line trucks.” One is now being tested and DiRicco anticipates buying more.
The impressive fuel savings accrue from the system’s cutting of engine hours by 40 to 50%. The system’s maker, Effenco, in Montreal, Quebec, calls it Active Stop-Start, and says it can be retrofitted to existing trucks or installed on new ones. It’s explained on its website:
“Because of the high stopping frequency of vocational trucks, the system is equipped with a powerful electric hybrid starter linked to the engine through a constant mesh PTO connection. The system uses this starter to restart the engine and does not add any load or wear to the existing electric starter and batteries. On releasing the brakes, the PTO-mounted electric hybrid starter takes less than half a second to take the engine from a stop to idle speed making the vehicle as responsive as it would have been if the engine had been running.”
A power pack consisting of three 48-volt ultracapacitor modules from Maxwell Technologies supplies the juice to spin the starter. The motor can also act as a generator, but that’s not yet being employed on the DSNY truck, a Mack TerraPro LE with a Heil body, says Benoit Lacroix, Effenco’s co-founder and vice president of sales and marketing. Neither is an available electric-driven pump that can keep hydraulic circuits pressurized to operate the packer function on the body.
“The truck’s driver brought up a huge safety feature for the crew,” Lacroix says. “They’re more aware of what’s happening around the truck” while they’re working and the engine’s off. “The noise abatement is pleasant for the driver and safer for everybody around it.”
A system’s cost now is in the low $30,000 range, he says, “but for reducing emissions, we’re one of the most efficient solutions.” That cost will come down in time as production builds, especially with volume orders. Right now Effenco is supplying systems for trash trucks and terminal tractors, where return on investment will be closer to a year.
“We have a project on cement mixers, dump trucks, bucket trucks and delivery trucks, for introduction in 2017,” he says. “Everything that is not long-haul in Class 8, this is our market.”