Freevalve: A Comparative GWP Life Cycle Assessment of E-fuel Fully Variable Valvetrain-equipped Hybrid Electric Vehicles and Battery Electric Vehicles

Abdelrahman W.M. Elmagdoub, Joris Simaitis, Mattias Halmearo, Urban Carlson, James W. G. Turner, Chris Brace, Sam Akehurst, Nic Zhang

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


Throughout its history, the internal combustion engine has been continuously scrutinized to achieve strict legislative emission targets. With the dawn of renewable fuels fast approaching, most Internal Combustion Engine (ICE) equipped hybrid electric vehicles (HEVs) face difficulty in adjusting their precise control strategies to new fuels. This is partly due to constrained limitations associated with camshaft-induced design-point air induction limitations. Freevalve is a fully variable valvetrain technology enabling independent control of valve lifts, durations, and timings. Additionally, the added degrees-of-freedom enable the capability to shut-off individual engine valves, optimizing combustion performance and stability through specific speed ranges. By design, it minimizes the existing breathing-related constraints that are currently hindering the extraction of the higher efficiency potential of ICEs. To explore the potential environmental benefits from improved fuel consumption and emissions, this study conducts a comparative global warming potential life cycle assessment on a HEV-configured Freevalve ICE vehicle against battery electric vehicles (BEVs) and camshaft-induced HEVs. Throughout this work, particular consideration is given to the lifecycle impact of Freevalve technology to reason its performance and efficiency gains in new generation powertrains. This is accomplished through a separate LCA study based on system bill of materials and estimated production energy usage. Additionally, the work evaluates current global average energy mixes and futuristic energy scenarios based on European projections to assess the impact of renewable energy and alternative methods of direct air capture (DAC) e-fuel production on total global warming potential (GWP) lifecycle impact. Under the fully renewable energy and fuel production scenarios, for a lifetime of 150,000 km, results suggested that e-fuel Freevalve HEVs have a net cycle GWP impact 55% lower than BEVs. Similar conclusions are observed for the global average grid case where a 50% reduction is observed in favour of the e-fuel Freevalve HEV compared to the BEV. This led to suggest that Freevalve-equipped engines coupled with next generation renewable fuels and dedicated hybrid concepts have significant potential in addressing environmental concerns and achieving global net zero CO2 emission targets.
Original languageEnglish (US)
Title of host publicationSAE Technical Paper Series
PublisherSAE International
StatePublished - Apr 11 2023

ASJC Scopus subject areas

  • Safety, Risk, Reliability and Quality
  • Pollution
  • Automotive Engineering
  • Industrial and Manufacturing Engineering


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