Special Focus: Fuel Cell Applications

A. SCHEY, Allison Transmission, Indianapolis, Indiana

With impending net-zero legislation and bans on diesel fuel, commercial vehicle fleets globally are exploring alternative fuel solutions. Hydrogen (H₂) power is an option (in addition to other clean energy sources) for commercial vehicle applications, and a growing number of examples are illustrating how it is being successfully adopted, both as a fuel for engine combustion and in H₂ fuel cell electric applications. 

Many conventional powertrains and electric propulsion solutions offered by vehicle manufacturers can accommodate any fuel type, meaning the decision on fuel is largely one for the fleet itself, subject to factors such as cost, availability, and fueling and/or charging infrastructure. In the H₂ combustion context, like the advantages recognized by fleets specifying compressed natural gas (CNG) and liquefied natural gas (LNG) engines for decades, fully automatic transmissions integrate well due to their ability to match torque converter options across a wide range of engine power and torque characteristics. 

H₂ fuel cells are now playing their part as a fuel source for electric axle propulsion systems in commercial vehicles. Examples of electric axles are being seen—for medium- and heavy-duty trucks and buses—agnostic to the electric energy source that are compatible with both full battery electric vehicles and fuel cell electric vehicles (FCEVs).  

Emissions-free energy is not the only advantage of H₂. In addition to environmental benefits, it can also offer a longer range between refueling than a battery electric vehicle on a single charge. This can help mitigate range anxiety, reduce vehicle downtime and widen the scope of vehicle applications.  

Of course, it is true that the H₂ fueling infrastructure must be substantially expanded to encourage wider-scale adoption of H₂ vehicles, just as the availability of charging points must be improved for battery electric vehicles. However, many demonstrator programs are already showcasing H₂’s feasibility as an alternative power source for commercial vehicles, as well as its suitability for a surprisingly wide range of vehicle vocations. 

Well-suited to long-range applications and frequent stop-starts. “A significant milestone in the history of commercial vehicles and the development of H₂ society,” is how Cheol Lee, Head of the Commercial Vehicle Division at Hyundai Motor, introduced the Hyundai XCIENT Fuel Cell, the world’s first mass-produced, heavy-duty truck powered by H₂ (FIG. 1). Launched in 2020, this rigid truck has a chassis cab, 4 x 2 or 6 x 2 drive systems, and a gross vehicle weight of 36 t. Power comes from a 180-kW H₂ fuel cell system with dual 90-kW fuel cell stacks, complemented by the author’s company’s proprietary heavy-duty fully automatic transmission^a. Seven large H₂ tanks offer a combined storage capacity of approximately 31 kg of fuel, or enough to drive ~250 mi before refueling (which takes 8 min–20 min, depending on ambient temperature).

As a follow-up to the XCIENT, Hyundai is developing a tractor unit with a driving range of 620 mi on a single charge. The company observes that fuel cell technology is particularly well-suited to trucks serving commercial shipping and logistics due to the long ranges and short refueling times.  

Fuel cells are also suitable for trucks with duty cycles that entail frequent stop-starts. Good examples of this are participants in the European Union’s (EU’s) HECTOR project, which is “designed to enable the smooth introduction of zero-emissions technology in conventional fuel vehicle fleets.” This project has deployed seven fuel cell waste collection trucks across seven pilot sites in northwest Europe: one each in Belgium, France and Scotland, and two each in the Netherlands and Germany. Some of these vehicles operate in city centers or rural areas; some are container trucks or front arm-loading trucks; and some are collecting municipal waste on a fixed schedule or collecting industrial waste on a flexible schedule. All are being tested in normal operating conditions.  

The Scottish participant in this project is the Aberdeen City Council, whose Hydrogen Aberdeen initiative aims to bring about a H₂ economy in the city’s region—there is form here: this Council first introduced 10 single-deck H₂ buses in 2012, the UK’s first H₂-powered sweeper vehicle in 2018, then 15 double-decker H₂ buses in 2020. The Aberdeen Council’s first refuse collection vehicle (shown in FIG. 2) with a H₂ fuel cell powertrain is based on a Mercedes-Benz Econic H₂ chassis with 15-kg tank capacity. This vehicle couples a 250-kW Hyzon electric motor to the author’s company’s medium-duty vehicle fully automatic transmission^b in conjunction with a 345-kW H₂ fuel cell powertrain and 140-kwH batteries—good for a range of 155 mi, a greater distance than equivalent electric vehicles, despite frequent stop-starts.

Another local authority in Scotland, the Fife Council, is running Allison-equipped refuse collection vehicles that run on dual-fuel: H₂ is injected in the engine’s air inlet and then mixed with diesel and used directly in combustion. The retrofitted H₂ kit includes an engine management system that optimizes the H₂-diesel mix to maximize emissions reduction with a balance of performance and range.   

Power source for an electric axle. Fleets of medium- and heavy-duty commercial vehicles interested in H₂ fuel cell electric propulsion have an option available in electric axle (e-axle) systems. For example, the author’s company’s single- or dual-motor e-axles are designed to fit between the wheels of heavy-duty trucks and buses, replacing the vehicle’s traditional powertrain system. This convenient bolt-in solution is compatible with the existing vehicle frame, suspension and wheel ends, and well-suited to most original equipment manufacturer (OEM) vehicle assembly processes. Because there is no need for a centrally-located power source, gearbox or driveshaft, this system weighs relatively little and requires very little space. One of the first production vehicles to adopt this space-saving solution, a fire-fighting truck with a 16-t chassis and crew cab can carry more fire-fighting equipment, water or foam.   

German vehicle manufacturer QUANTRON made its world premiere at the IAA International Motor Show in Frankfurt in September 2022 with an electric axle that is integrated in a fuel cell electric vehicle. This heavy-duty truck, based on the MAN TG3 platform and capable for tractor and chassis derivatives, has 54 kg of on-board H₂ storage with fuel cells delivering 240 kW of clean power into a 118-kWh battery pack. At the heart of the truck, the author company’s electric power axle^c combines in one compact unit a two-speed transmission and two integrated electric motors, which deliver a total of 454 kW of continuous power and up to 652 kW of peak power. This combination of technologies gives a range of up to 700 km (435 mi).H₂T

NOTES 

^a Allison Transmission’s 4500R fully automatic transmission  

^b Allison Transmission’s 3000 series  

^c Allison Transmission’s eGen Power 130D e-Axle 

ABOUT THE AUTHOR

ALEX SCHEY is an engineer by training and entrepreneur by practice, having co-founded London-based Vantage Power, a technology company acquired in 2019 by Allison Transmission. At Allison, Schey is Managing Director, Electrification Commercialization and Strategy, where he oversees business development and commercial strategies for Allison’s electrified products globally. He is passionate about promoting entrepreneurship and STEM to the next generation and has given more than 60 presentations at schools and universities in addition to two TEDx talks. Schey was voted one of London’s 25 Under 25 in 2013 by The Evening Standard, and one of Europe’s 30 Under 30 by Forbes in 2016.