The average European heavy-duty truck burns from 31 to 38 L of diesel fuel per 100 km of travel (6 to 8 mpg), according to European Commission estimates and truck magazine tests. That might sound like low fuel economy until one considers that a big-rig truck can weigh 40 ton (36 t) or more.

Accelerating such large masses to highways speeds and dragging them up hills account for a big chunk of the trucks’ overall fuel use. Road haulage by the millions of heavy trucks that ply European roads and highways accounts for more than a fifth of the European Union’s total output of carbon dioxide and diesel particulate emissions.

The great weight of fully laden big trucks, of course, provides an opportunity to recapture some of the energy that’s typically lost during deceleration, downhill travel, stop-and-go traffic, and other load transients using regenerative braking systems, which boost fuel economy and cut tailpipe emissions.

Adgero, a start-up firm that’s based in Strasbourg, France, is developing a parallel hybrid storage-boost system—essentially a kinetic energy recovery system (KERS) and an electric drive unit—that can be mounted under semi-trailers. The Adgero Hybrid System, it is claimed, is the first KERS for heavy-duty trucks.

Depending on the terrain and traffic conditions, the retrofit can save from 15% to 25% in fuel and associated emissions, said founder and CEO Mack Murray. The Adgero Hybrid System comprises an 800-V ultracapacitor bank supplied by Estonia’s Skeleton Technologies, an electric drive axle from a major European manufacturer for acceleration assistance, and the Adgero Monitor, a wireless intelligent management system that tracks driver input up front to control the regenerative braking and acceleration boost at the rear.

The patent-pending design can pay for itself in three or four years through reduced consumption alone, Murray maintained, and where expected tax climate subsidies become available the payback could be even quicker. The company has recently entered negotiations with a major European semi-trailer manufacturer to potentially integrate the new Adgero design into its production lines.

Electric-hybrid retrofit

“We want to retrofit semi-trailer fleets of lessors and leasing customers, particularly those that are used in road/rail intermodal systems in which the trailer travels alone as they do in Lohr, CargoBeamer, or MegaSwing systems,” he said. Any truck trailer made in the last 15 years is compatible. “There’s not much space on a trailer so we shoehorned” the compact energy storage and control add-ons into the I-beam chassis understructure.

“A perfect road/rail transport corridor for us,” Murray explained, “would be the shipping route by which Norwegian fish is trucked to rail depots where it is sent in detached semi-trailers down to Spain and other Mediterranean countries where they are trucked to warehouses that empty them of fish and fill them with fruit to be shipped back up to Norway.”

But even though the majority of European heavy-duty truck trips are less than 200 km (125 mi), the hybrid drive can save fuel. Great Britain, the Netherlands, and Germany are the company’s initial target markets, he noted, though France is more problematic.

The Adgero team thinks electrified trailers makes more sense than electric-hybrid tractors, an alternative way to recapture diesel fuel energy, one that is used, for example, by the Freightliner’s recent 12-mpg SuperTruck concept, which links tractor to powered trailer “with a 600-V line and so can operate like a Toyota Prius. It’s not the best solution,” he said. Conventional hybrid systems would require the hauling companies at both ends of the rail links to purchase new trucks. “We can do the same without the need for new trucks.”

The new strap-on drive unit, which contains a 200-kW motor capable of spinning up to 2900 rpm and providing a maximum torque of 750 N·m (550 lb·ft) at zero rpm, is certified for road use and has been engineered to exceed the typical 10-year lifetime of an average trailer. Depending on the suspension, he said, the electric-powered drive axle typically replaces the central undriven axle in a standard three-axle setup on the trailer rig (such as a LeciTrailer curtainsider), which is always in contact with the road surface.

The retrofit system is guaranteed to be fully compatible with existing infrastructure. And if an Adgero-enabled trailer is picked up by a truck with no monitor, the hybrid system simply stays in standby mode and acts like any other trailer.

Murray formed Adgero a couple of years ago together with fellow entrepreneurs co-founder and Chief Technology Officer Ginès Linares, Soun Schuller, the software development leader, and Frédéric Soulier, the chief data officer.

Ultracapacitor storage

“By partnering with Skeleton Technologies, we put the world’s most advanced ultracapacitors at the heart of our system,” Murray said. “This will give us an edge in an industry where energy density is a key metric.” He said that Skeleton uses a patented graphene material that offers better conductivity and higher surface area, and so can deliver twice the energy density and five times the power density of competitors’ products.

“To enable this solution for Adgero,” said Skeleton CTO Volker Dudek, “we developed intelligent power modules with a proprietary management system that allows for smart monitoring and control of the energy/power profile according to customer requirements.”

During the last year, Skeleton specialists worked with the Adgero team to adapt an 800-V ultracapacitor power module that is used in the motorsport industry to meet the needs of road freight vehicles. The module, which comprises five 160-V units that are composed of cylindrical cells, monitors each individual cell to actively balance itself.

In recent months the Adgero Hybrid System has been put through rigorous vibration, shock, and immersion testing procedures, Murray said. In 2016, plans are that the French logistics company Altrans will conduct road tests.

Adgero and Skeleton Technologies aim to ramp up production, with the objective of manufacturing 8000 to 10,000 units annually by 2020. Pre-series models (in 2016 to 2017) are to cost around €45,000 ($50,600), whereas series production models (in 2018) will be priced at €25,000 ($28,000). Although the Adgero team is concentrating on the European truck market, Murray said that the concept could probably work in North America and Asia as well.

Murray noted that the addition of Adgero’s open electrical bus and ultracapacitor bank to a trailer provides the retrofitted trucks with an uninterruptible power supply for services such as 4G, onboard telematics, vehicle-status reporting, and user configurable subsystems as well as network data services such as autonomous trailer tracking, monitoring and control, autonomous payload monitoring, and intermodal-compatible fleet-management route optimization.