Long-haul heavy-duty vehicles, including trucks and coaches, contribute to a substantial portion of the modern-day European carbon footprint and pose a major challenge in emissions reduction due to their energy-intensive usage. Depending on the hydrogen fuel source, the use of fuel cell electric vehicles (FCEV) for long-haul applications has shown significant potential in reducing road freight CO${}_2$ emissions until the possible maturity of future long-distance battery-electric mobility. Fuel cell heavy-duty (HD) propulsion presents some specific characteristics, advantages and operating constraints, along with the notable possibility of gains in powertrain efficiency and usability through improved system design and intelligent onboard energy and thermal management. This paper provides an overview of the FCEV powertrain topology suited for long-haul HD applications, their operating limitations, cooling requirements, waste heat recovery techniques, state-of-the-art in powertrain control, energy and thermal management strategies and over-the-air route data based predictive powertrain management including V2X connectivity. A case study simulation analysis of an HD 40-tonne FCEV truck is also presented, focusing on the comparison of powertrain losses and energy expenditures in different subsystems while running on VECTO Regional delivery and Longhaul cycles. The importance of hydrogen fuel production pathways, onboard storage approaches, refuelling and safety standards, and fleet management is also discussed. Through a comprehensive review of the H${}_2$ fuel cell powertrain technology, intelligent energy management, thermal management requirements and strategies, and challenges in hydrogen production, storage and refuelling, this article aims at helping stakeholders in the promotion and integration of H${}_2$ FCEV technology towards road freight decarbonisation.

This article aims to calculate, analyse and compare the optimal powertrain sizing solutions for a long-haul plug-in series hybrid coach running on diesel and hydrotreated vegetable oil (HVO) using a co-design optimisation approach for: (1) lowering lifetime carbon footprint; (2) minimising the total cost of ownership (TCO); (3) finding the right sizing compromise between environmental impact and economic feasibility for the two fuel cases. The current vehicle use case derived from the EU H2020 LONGRUN project features electrical auxiliary loads and a 100 km zero urban emission range requiring a considerable battery size, which makes its low carbon footprint and cost-effective sizing a crucial challenge. Changing the objective between environmental impact and overall cost minimisation or switching the energy source from diesel to renewable HVO could also significantly affect the optimal powertrain dimensions. The approach uses particle swarm optimisation in the outer sizing loop while energy management is implemented using an adaptive equivalent consumption minimisation strategy (A-ECMS). Usage of HVO fuel over diesel offered an approximately 62% reduction in lifetime carbon footprint for around a 12.5% increase in overall costs across all sizing solutions. For such an unconventional powertrain topology, the fuel economy-focused solution neither achieved the lowest carbon footprint nor overall costs. In comparison, $C{O}_2-$cost balanced sizing resulted in reductions close to the single objective-focused solutions (5.7% against 5.9% for the $C{O}_2$ solution, 7.7% against 7.9% for the TCO solution on HVO) with lowered compromise on other side targets ($C{O}_2$ reduction of 5.7% against 4.9% found in the TCO-focused solution, TCO lowering of 7.7% against 4.4% found in the $C{O}_2$-focused solution).

Simulation with a basic representation of longitudinal vehicle dynamics is known to be sufficient for initial powertrain development activities related to efficiency and emissions such as concept application, optimal sizing, analysing the effects of physical and functional changes and also for defining basic control laws. However, when it comes to comprehensive analysis for efficiency improvement, minimizing instantaneous emission peaks or studying the impact of the new concepts on road safety, drivability and performance, the significance of detailed vehicle dynamics cannot be ignored. The work presented in this article defines a longitudinal vehicle dynamic modelling approach considering important characteristics such as the influence of normal load transfer on the varying grip of the front and rear wheels, the effect of wheel slip, and a complete representation of resistances encountered against vehicle motion with the objective of taking the analysis even closer to the actual driving conditions. The behaviour of this combined simulation platform under normal and extreme driving conditions seems to precisely follow the real scenario. This approach is a first step towards future analysis, optimization and controls development for improving transient powertrain aspects such as maximizing regenerative braking under heavy deceleration or optimizing road charging in P4 parallel hybrid architecture by managing wheel slip losses.