Will it ever be possible to haul 50+ tons with fuel cell-powered trucks? – Dr. Julio C. Garcia-Navarro.
There was a recent unveiling by Toyota and Kenworth in the Port of Los Angeles, where they announced that 5 trucks will be in operation in the Port of Los Angeles. Each truck has 560 HP and can travel 480 km with a single loading of hydrogen. According to my calculations, this would mean that the trucks have an onboard H2 storage around the 20 kg.
On further news, Nikola made a claim (in 2019) that the range of their trucks is around 1200 km @ 24 km/kg-H2 (see here for the power density of hydrogen in trucks); the trucks also feature a 250 kWh battery that would give them a range of 200 km more. This means that their onboard H2 storage is around 40 kg. It appears that truck manufacturers will fine-tune their onboard storage likely between 20 and 40 kg.
I do not think that a truck would need the level of autonomy proposed by Nikola, considering that refueling at its slowest would be done at 1-2 kg/min (What does a hydrogen refueling station look like?), so a 20 kg H2 only needs 10-20 minutes to refuel, which is fine if there is a dedicated hydrogen refueling station that tanks up the trucks while not in operation. Future developments would make it possible to refuel H2 at a rate of 10 kg/min (although we are still some way from it happening), allowing for refueling a 20 kg truck in 2 minutes. All it takes is having enough commercial, publicly accessible HRSs to decrease the level of autonomy needed by fuel cell trucks (which has an impact on their price).
These announcements from Toyota-Kenworth and Nikola left me wondering: which parties are developing fuel cell trucks? What are the challenges to overcome? And will it really be possible to haul 50+ tons with a fuel cell-powered device?
Which parties are developing a fuel cell-powered truck?
We now know that Nikola and Toyota-Kenworth are two of the parties; who are the rest? I have been spending some time compiling the table below, reading MoU (Memorandums of Understanding) announcements, via my network, and while attending webinars:
FC supplier | Truck manufacturer | Comments |
Ballard | Mahle(?) | Not sure if only HDVs |
Cummins | Scania | |
Daimler | Volvo | Joint venture called Cell Centric |
GM | Navistar (International) | |
Honda | Isuzu | Not sure if still goes on |
Horizon fuel cells | Hyzon | |
Horizon fuel cells | JMC (Ford) | JMC is joint venture of Ford |
Hyundai | ||
Man | Part of Volkswagen group | |
Nuvera | Hyster-Yale | Only MDVs |
Toyota | Kenworth |
Like Formula 1 constructors, there are two types of developers of hydrogen fuel cell-powered trucks:
- Partnerships between fuel cell developers and truck manufacturers (for example Cummins-Scania and Horizon Fuel Cells-Hyzon). These are the Haas-Ferrari and Red Bull Racing-Honda teams of the hydrogen world.
- Companies that do the whole development of fuel cell systems for trucks and the trucks themselves (like Man and Hyundai). These are like the Mercedes and Ferrari of the hydrogen world.
The list is not infallible nor complete, so if you happen to have more information, I would appreciate it if you sent me an email or added it to the comments below.
What needs to be done before hydrogen-powered fuel cell trucks enter the market?
This one is a tricky one to answer. Fuel cell systems are not exactly being retailed in a mass-market way unlike internal combustion engines (ICEs), which means that there is less learning by doing in real-world scenarios. That being said, there has been a steady rate of development of fuel cells and fuel cell systems, even so that there is a standard testing cycle developed by the US Department of Energy (DOE) for fuel cell systems that is used as the benchmark procedure to characterize fuel cell stacks and systems in the US. Much has been done to develop fuel cell systems so by now there is no doubt that fuel cells are in a highly developed state.
The main issue with fuel cell stacks is performance degradation. To understand performance degradation, I first need to introduce the concept of polarization curves. The figure below showcases a typical polarization curve (the voltage-current characteristics of a fuel cell):
A proton exchange membrane fuel cell (PEMFC) can be understood as a voltage-controlled current source, similar to other electronic and electrochemical devices such as solar cells and lithium batteries. When a voltage set-point is given to the PEMFC, the current that can be drawn will be determined by factors such as the operating conditions (temperature, pressure of the gases, humidity, etc.). The goal in operating PEMFCs is to maximize the power that is drawn from them. The state-of-the-art PEMFCs have a power density of between 0.7 and 1.1 W/cm2 of active area in a single cell; however, this power density is achieved only at the beginning of life (BOL). After a certain number of operating hours (8.000), the power density can decrease by as much as 20%, which means that a fuel cell stack that was rated at 100 kW when new, will only be producing 80 kW at its end of life (EOL) conditions i.e., after 8.000 hours of operation.
Losing 20% of its rated power is a massive blow to any application: if you are not able to provide the rated power demand after such a relatively short time (1 year of continuous operation for trucks and probably 3 years of partial operation for cars), then PEMFCs do not stand a chance against ICEs that could run up to 1 million km. There are two strategies that can be used to compensate for the loss of power in PEMFCs:
- Replace the PEMFC stack after its power rating drops below a threshold
- Oversizing the PEMFC stack (higher rated power at BOL conditions) so the power drops to its “nominal” (i.e., the promised value on the spec sheet) value at EOL.
So far, since most of the PEMFC systems used in mobility have been installed in cars, which have a lower usage frequency than trucks, fuel cell car manufacturers (Toyota, Honda and more recently Hyundai) have decided to go for the replacement strategy. For trucks, the story is different: they have a higher utilization rate and cannot afford to be sent to the garage every year to get a new powertrain. In this case, the PEMFC manufacturers are choosing to oversize their PEMFC stacks.
Furthermore, the target for durability in PEMFCs for trucks is more ambitious than for cars. The Million Mile Fuel Cell Truck consortium is aiming at developing a stack that retains a power density of 0.7 W/cm2 at 0.7 V operating voltage per cell after 25.000 hours. To achieve this, the initial idea is to make a 67% oversizing of the PEMFC stacks i.e., the PEMFC stack would contain the same number of cells but with a higher surface covered by the catalyst. Below you can find a waterfall chart with the cost development of PEMFC systems for trucks (HDVs) as well as the targets by the US DOE:
There are challenges around developing and introducing fuel cell hydrogen-powered trucks to the market, such as performance degradation and increase in the operating temperatures. Despite the challenges, the development of fuel cell trucks seems to be full steam ahead.
Dr. Julio C. Garcia-Navarro.
One of the expected developments in the operating conditions of PEMFC stacks for HDVs is the operating temperature. Typical PEMFCs operate around 80oC because it gives a good compromise between high reaction rates in the fuel cell (so higher power rating) and slow degradation of the components (slow dissolution of the catalyst, slow leeching of fluoride ions from the proton exchange membrane, etc.). So far, this operating temperature has worked wonders in small systems and stationary applications where the cooling load (i.e., the amount of heat that needs to be cooled, roughly 40% of the rated power in a PEMFC) is low enough and the footprint of the PEMFC system is not a limitation. In trucks, however, the situation changes: the truck manufacturers will be aiming at using high-power PEMFC stacks (at least 150-200 kWe) and, since it is a mobile application, the footprint of the system becomes a limiting factor.
Moreover, some of the truck manufacturers are trying to push the operating temperature of PEMFC stacks beyond 90oC where they can comfortably fit a conventional radiator to provide the heat exchange area needed to cool down the stack using the same (or a similar) system as the one used in diesel powertrains. The challenge for PEMFC stacks is that operating at 90+oC could be very detrimental for some of the components in a fuel cell. For example, the polymeric components like the PEM and the gaskets can deform when exposed to high temperatures so continuous operation at 90+oC would definitely harm them. Increasing the operating temperature could bring a challenge to the durability of other parts of the fuel cell as well: inhomogeneous temperature distribution leading to condensation of water in the cell, higher dissolution rate of the catalyst, higher probability of occurrence of free radicals that attack the PEM, to name a few.
Is it really going to be possible to haul 50+ tons with a fuel cell-powered truck?
Despite the challenges that need to be overcome, I remain positive that we will be seeing fuel cell hydrogen-powered trucks on the road. Why? Because Hyundai trucks have already driven one million kilometers in Switzerland. There is a will from the truck manufacturers (look how large Table 1 is), from the transporters, from the governments, and from the scientific community. And you know what they say: where there is a will, there is a way.
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About the author
Dr. Julio C. Garcia-Navarro is a Hydrogen Project Coordinator at New Energy Coalition. He has worked in the hydrogen industry for nearly a decade, on topics such as hydrogen electrolysis, compression, and transportation. Besides hydrogen, he is passionate about Renewable Energy Systems and the Internet of Things.
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