Range extenders could bridge gaps in charging networks

Range-extender technologies that would enable operators of long-haul electric trucks to bridge any gaps in charging networks with carbon-neutral fuels are being developed in the UK and USA.

Sheffield-based Libertine is working on novel compact ‘free piston’ engines that can generate current directly, without any rotary motion.
Libertine’s free piston engine has no crankshaft, but features two opposed magnetised pistons in a single cylinder with a central combustion chamber. The cylinder has external windings of copper wire, and the reciprocation of each piston passing through the windings generates current. Piston movement at the end of stroke is controlled by an air cushion, and the compression ratio can be adjusted to accommodate various fuels including biofuels.

The slim shape of the engine lends itself to scalability and incorporation into vehicle battery packs.

Libertine has attracted £2.6 million in funding from the UK’s Innovate UK’s Sustainable Innovation Fund Competition to develop the engine as a range extender for trucks.

The project will integrate Libertine’s technology with Mahle Powertrain’s pre-chamber ignition system, thereby forming a multi-cylinder opposed free piston engine, optimised and calibrated to start and run cleanly on renewable alcohol fuels. It will also integrate various enhancements for thermal management, durability and electrical power conversion efficiency, allowing performance to be validated against OEM-specified requirements.

Sam Cockerill, Libertine’s CEO, said: “As a director of a major haulier, I have first-hand knowledge of the hurdles the industry faces in reducing emissions. The impact of a pure electric powertrain on payload, productivity and upfront costs, combined with limited charging infrastructure and restricted new vehicle choice, are real challenges.

“The combination of a smaller battery and an efficient onboard generator using 100 per cent renewable fuels has the potential to solve these pain points and drive significant uptake of net zero trucks before the end of the decade.”

Meanwhile in the USA, start-up Hyliion has developed an electric truck powertrain that is supported by a natural-gas powered generator making a series hybrid: the Hypertruck ERX. It is capable of travelling 25 miles on batteries alone (enabling it to enter zero-emissions zones), and up to 1,000 miles on gas power without refuelling.

The US firm has also developed pure electric truck drivelines that can handle journeys of up to 250 miles, and the gas hybrid ERX is intended for longer hauls. Unlike Tesla, which is developing a complete truck, Hyliion is offering its technologies, which use Dana motors and running gear, as bolt-in alternatives to conventional drivelines in trucks produced by mainstream manufacturers. It boasts that using bio-methane, widely available in North America (and the UK), as a road fuel makes the truck not just carbon-neutral, but carbon-negative, and this may aid European manufacturers in reaching VECTO targets.

Hyliion’s ERX design is suited to the North American market, where the Class 8 maximum weight bracket is dominated by bonneted trucks with long chassis, and buyers can exercise considerable control over driveline choice by, for instance, specifying a Cummins engine and Eaton transmission in place of the OEM components. It might pose more of a challenge in Europe with its forward-control cabs, short chassis, and vertically-integrated drivelines.