How Trailers Are Harnessing 'Free' Energy

Most discussion of truck electrification has centered around powering the actual truck or tractor unit. Trailer electrification has mostly involved refrigeration units. But some companies believe the trailer itself can play a role in sustainable transport beyond aerodynamic add-ons:

Capturing Wasted Kinetic Energy for Reefer Trailers

Ecolution KWH is an e-mobility and power company that has received a U.S. patent for reusing wasted kinetic energy in refrigerated trailers. When combined with an electric or hydrogen-fueled truck, the company says, the Ecolution trailer accomplishes a total elimination of carbon emissions. 

Ecolution's “green perfect cycle” Module Active Response System, or Mars, replaces the diesel tank and transportation refrigeration unit genset typically used in reefer trailers with swappable batteries. As a result, it can reduce the average weight of a refrigerated trailer by 1,200 pounds, according to the company, increasing the hauling capacity of the trailer and delivering greater battery life for the electric truck. 

The key innovation, according to the company, is the use of alternators connected to disc brakes in the trailer, sending power through a converter to a battery storage unit for on-demand energy, all within the reefer trailer.

The company now has four patents pending in Germany, Japan, China, and South Korea. The invention, under research and development for five years, now goes into a prototype in the U.S., Europe, Latin America, and Asia.

"The beauty of the discovery is in its simplicity,” said Johanne Medina Then, Chief Executive Officer of Ecolution. “And because the battery unit is located in the trailer, second-life Tesla and other electric vehicle batteries can be recycled, helping to eliminate yet another environmental problem.”

Chief Technology Officer Johnny Then Gautier adds, "The use case for Ecolution is even starker at the point of delivery, where there is a shortage of cold storage space in grocery stores. Reefers are often placed for hours or days in the parking lot, burning diesel to power their generators while they wait. That creates a serious noise, health and environmental problem.”

Entire Tractor-Trailer as Electric Plug-In Hybrid

Trailer Dynamics, a German company, is working with Chinese battery maker Contemporary Amperex Technology Co. Limited (CATL) to develop the Newton eTrailer, which will launch in 2023 in Europe.

The Newton e-Trailer is an electric drive train that replaces one of the trailer's conventional non-powered axles with an electric axle. In combination with the diesel vehicle, the entire tractor-trailer system is converted into an electric plug-in hybrid.

In combination with adaptive aerodynamics developed by Trailer Dynamics and the intelligent control strategy for the electric auxiliary drive, significant CO2 emission reductions will be achieved and diesel savings in average of 40% are possible, according to the company.

The Newton eTrailer is designed to respond to the driving behavior of its coupled tractor using integrated electric drive trains and provides support for it through an integrated electric transmission system, managing the electrical energy resources intelligently along the entire route. Both sides creatively apply the batteries to semi-trailers, while improving efficiency and also lowering operating expenses.

CATL is developing a 300 kWh lithium iron phosphate (LFP) battery with cell to pack (CTP) technology and cooling liquid for the Newton eTrailer.

EHub for Trailers

Last year at the North American Commercial Vehicle Show, ConMet showed off its new PreSet Plus Electric Hub (eHub), a motor/generator packaged to mount at the wheel-end within the existing space between the axle spindle and the brake shoes. ConMet said it planned to initially launch a trailer system, where it can supply power for auxiliary electrical systems on the trailer, as well as replace the diesel engine for trailer reefer systems.

Depending on the driving cycles, on regional or urban delivery routes, the eHub, batteries, and controllers could supply enough power to run the refrigeration unit throughout the day, cycling on and off, and generating its own power directly from the rotation of the wheels.

In scenarios where the battery is kept fully charged, eHub energy can be used to power auxiliary electrical systems on the trailer, too, allowing for basically silent operation while at a delivery site. That opens up opportunities for delivery times that might be frowned upon due to noise restrictions.

The eHub integrated controls also allow for regenerative braking mode or propulsion assist mode, enabling the utilization of all the power captured throughout the day to optimize fuel savings – knowing that at the end of the day it can be plugged in again for overnight charging using shore power.

Harnessing the Sun

Scania is researching development of a solar-cell-clad trailer to power a plug-in hybrid truck. Initial tests indicate possible fuel savings of 5-10% in Sweden and twice that amount in sun-rich southern Spain.

“Solar cells have previously been employed on boats and caravans but then only to power auxiliaries such as refrigerators and cookers and not the actual powertrain,” says Eric Falkgrim, Technology Leader in Vehicle Design at Scania R&D.

The truck will be operated in daily transport assignments by the Swedish haulier Ernst Express, which also collaborated with Scania in trials of the world’s first electric road with overhead catenary lines. Ernst Express will operate an 18-meter-long solar-cell-clad trailer with a total area along the sides and roof of 140 square meters. In total, the solar panels are expected in Sweden to annually generate 14,000 kWh.

The research project will also examine whether the trailer can feed electricity into the grid when the batteries are fully charged and the truck is parked, for example, over weekends.

In a preliminary study, operations in mid-Sweden were simulated reaching a potential fuel saving of 5-10%. In Sweden, there is enough sunlight from spring to autumn to generate energy and although the sun is weak except during summer, there are more hours of sunlight. During the rest of the year, there's not enough sun in Sweden. Southern Spain has 80 more hours of sunlight.

Hyliion Powered Trailer Axle

Interestingly, U.S. truck electrification company Hyliion got its start developing a trailer product before it turned to the tractor. The Hyliion Intelligent Electric Axle captured energy during braking and as a tractor-trailer runs downhill, and reapplied energy through a drive axle to help the truck launch and accelerate from a standstill and run uphill.

The Intelligent Electric Axle was a powered axle designed to replace a “passive” axle on a standard trailer tandem, and promised big fuel savings – 10 to 20% from hybrid-powered operation alone.

Hyliion pivoted to a tractor-based hybrid electrified product, this summer launched a fully electrified drivetrain, and just recently went public. But who knows, maybe we'll see them go back to their roots at some point and add the electrified trailer back into the mix.