Libertine FPE, the creator of Smart Engine control technology for free piston engine (FPE) generators, has secured £2.6 million (US$3.6 million) in Innovate UK funding to advance development of its range-extender concept for heavy-duty applications. Libertine says that free-piston range-extender engines can offer the efficiency of fuel cells, the durability of conventional engines and achieve carbon reductions using renewable fuels.

Libertine’s free-piston engines contain pairs of pistons which are free to slide within a linear combustion cylinder. The introduction of a fuel mixture and a carefully timed spark drives the pistons down the cylinder where they rebound off air springs, enabling the cycle to repeat. Magnets in the pistons energize coils around the cylinder, generating electricity with an efficiency far above that of conventional engines and generators.

Cutaway illustration showing a twin free piston engine, with the copper coils and the two magnetic pistons free to slide in the cylinder bore, and the induction and exhaust ports in the center.

While the FPE concept is not new, Libertine’s control and manufacturing know-how has unlocked its potential as a vehicle range-extender. Libertine says that its intelliGEN control technology solves the free-piston motion challenge, optimizing combustion conditions from the first ignition cycle. This technology enables improved cold start performance using wet or ‘hydrous’ bioethanol fuel, a blend of 90% bioethanol and 10% water (E90W10).

In earlier tests, Libertine’s intelliGEN opposed free-piston platform was modified for use with wet bioethanol, using a direct injection uniflow scavenged two-stroke architecture.

Libertine’s intelliGEN control systems solve the challenge of free piston position control, enabling accurate combustion and a variable compression ratio, essential for reliable cold start and running.

The 2021 project will integrate Libertine’s technology with MAHLE Powertrain’s pre-chamber ignition system to form a multi-cylinder opposed Free-Piston Engine, optimized and calibrated to start and run cleanly on renewable alcohol fuels. The project will also integrate multiple enhancements for thermal management, durability and electrical power conversion efficiency, enabling performance validation against OEM-specified requirements.

Innovate UK’s Sustainable Innovation Fund is supporting the project to develop and demonstrate a performance validation prototype, building on successful proof of concept testing completed in 2020.

Sam Cockerill, Libertine’s CEO, states that the move to decarbonize heavy-duty transport must be driven by demand and affordability: truck operators will not invest in zero-emission technologies if there is no effective way to run, refuel and recharge them.

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 up-front 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% renewable fuels has the potential to solve these pain points and drive significant uptake of net zero trucks before the end of the decade.

—Sam Cockerill

Discussions with prospective OEM customers identified the need for a performance validation prototype as a key development milestone.

This validation phase is ideally matched to MAHLE Powertrain’s design and development capabilities. In a world-first we will be integrating our passive prechamber combustion hardware and control systems with Libertine’s free piston platform, and then validating the performance of this novel architecture under load conditions and duty cycles representative of real-world operation.

—Adrian Cooper, MAHLE Powertrain’s head of new technology

The project is the second phase of development to be funded through Innovate UK’s Sustainable Innovation Fund Competition.