Will This Energy Approach Work for Semi Truck Trailers?

ZF unveils a way to cut down CO2 emissions without huge and costly batteries in big rigs.

There are a handful of electric semi trucks on the market at the moment, with the dropping costs and slowly advancing battery tech finally permitting BEV trucks some long-haul distances, at least on paper.

But advances in electric semis aren't confined just to the tractors themselves. ZF's idea revolves around electrifying the trailers, and using them for propulsion.

The company's TrailTrax concept, revealed this week at the IAA Transportation in Hanover, is essentially a semi trailer with a 210-kW AxTrax 2 e-Axle, a brake energy recuperation system, and a battery.

And the powered trailer, which can recover and store energy from braking, isn't necessarily meant to be used with a battery-electric tractor. One of the main promises of this tech is the reduction of CO2 emissions by as much as 40% when coupled with an internal-combustion tractor, while also generating up to 16% in energy savings, making this a hybrid of sorts.

"TrailTrax technologies offer significant potential to reduce operational costs and CO2 emissions in road freight transportation," said Bernd Meurer, responsible for the TrailTrax program at ZF. "Energy losses, including brake friction, air drag, and rolling resistance, are major causes of fuel inefficiency, but with our TrailTrax concept, we can make a big difference."

The concept is similar in layout to that of "bendy buses," electric or not, which often feature the propulsion part in their tail sections.

ZF has been working with trailer manufacturer Kässbohrer on its TrailTrax concept, which is due to start testing in 2025 under a project supported by the European Union.

But as with BEV trucks, there are some notable drawbacks to this idea, we would argue. Such a system, just like in semis, would still be subject to the main hurdle facing battery-electric semis themselves: a lack of charging infrastructure.

Some progress has been made on EV stations for heavy-duty trucks in the past couple of years, as truck makers have fielded more BEV versions of their semis and have teamed up to create charging corridors that will feature megawatt-level charging.

But the charging corridors are hardly ready at the moment for a stream of trucks silently whooshing by.

Costs are another concern, as fleet operators aren't particularly enthused at the moment about BEV trucks themselves.

The business case for producing 40% less CO2 when coupled with an ICE tractor also seems on the fragile side barring serious regulatory mandates. There have to be incentives for trailer manufacturers to invest in this tech as well.

"Successfully managing this transformative technology will require the combined efforts of all industry players," Meurer summed up this engineering direction.

Will this powered trailer tech catch on in the coming years, or are electric semis bound to get here first in significant numbers? Let us know what you think in the comments below.

Jay Ramey grew up around very strange European cars, and instead of seeking out something reliable and comfortable for his own personal use he has been drawn to the more adventurous side of the dependability spectrum. Despite being followed around by French cars for the past decade, he has somehow been able to avoid Citroën ownership, judging them too commonplace, and is currently looking at cars from the former Czechoslovakia. Jay has been with Autoweek since 2013.

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