Bosch’s Electric Trailer Axle Saves Fuel, Cuts Diesel Emissions

September 20, 2018 by Alan Adler, @AlanAdler

Trailers equipped with electrified components can have positive implications for the bottom line.

Adding an electric axle on a semi-trailer not only saves fuel, but it uses recovered energy from braking to boost the truck’s uphill driving performance. It also can help keep refrigerated cargo cool.

That’s why Robert Bosch LLC is looking where others aren’t: behind the truck. As others, including Bosch itself, focus on alternative energy systems to replace diesel engines in tractors, the technology supplier wants to make the trailer do more.

Bosch showed a mockup of the trailer e-axle Wednesday at the IAA Commercial Vehicles show in Hanover, Germany.

Though the technology is two or three years away, “all of the components are ready right now,” said Jason Roycht, Bosch’s head of commercial and off-road vehicles in North America. “We’re looking at new applications of our standard motors, our standard inverters, our standard controllers with the logic.”

The Bosch system uses electric motors developed for passenger cars because the e-axle is only needed for certain tasks a few times an hour.

Timing will depend on trailer buyers, Roycht said. “What we’ll see is a transition period where for certain users, it’s going to make sense. For certain ones it’s probably never going to make sense.”

The Bosch system can be retrofitted on the center axle of an individual trailer. Trailers outnumber tractors by nearly three to one. New tractor-trailer combination designs could incorporate the e-axle.

Bosch did not provide cost estimates but said owners would recoup costs after two years. A major pricing factor will be the amount of energy in the battery.

Trailers typically stay in service longer than the trucks that haul them. They are swapped onto different tractors, dropped in freight yards for extended periods and often poorly maintained as they age.

But for the first time they will have to comply with greenhouse gas regulations. Trailer makers are installing onboard fuel-saving tire inflation and aerodynamic add-ons to save fuel, which will also reduce nitrous oxide, or NOx, emissions.

The California Air Resources Board worked with the Environmental Protection Agency and the National Highway Traffic Safety Administration to create rules requiring cleaner trailer emissions. The Phase 2 GHG regulations are currently tied up in federal court awaiting revisions, but California plans to enforce the rules on trailers built after Jan. 1, 2020.

Bosch’s e-axle system could generate as much as 4 percent savings over diesel alone from the electrical assistance in starting, accelerating and on ascents, according to the company.

On the road, the trailer would tell the tractor how much recaptured energy was available for use from storage in a high-voltage battery. The motors in the electrified axle start only if they can recover energy, such as during downhill driving.

The trailer e-axle is most sensible for trucks with auxiliary power units such as refrigerated trailers. If the cooling unit operates using the power captured by the battery, Bosch calculates that it can save nearly 2,400 gallons of diesel a year. Such savings also would help cut NOx emissions.

Separately, refrigerated trailer maker Carrier Transicold said it was embedding its patented E-Drive technology into power modules that energize refrigeration units with no engines.

The Bosch e-axle system also could incorporate some autonomous technology to assist the movement of trailers. They could back themselves into a dock for loading and then rejoin a trailer without human involvement.

The autonomous feature of the trailer e-axle fits within Bosch’s vision of how long-haul might look in the future. During a technology program at its Flat Rock, Mich., proving grounds in May, Roycht described how highway corridors with driverless convoys could operate.

Groups of three to five trucks would travel 200 miles between way points. They would load or unload and return on the same route or go on to the next stop. The lead truck might have a safety engineer on board.

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