Comment: The case for hydrogen ICEs strengthens

Growing concern about energy security in Europe and an impending EV battery crisis caused by global shortages of vital minerals and high demand for lithium, is further highlighting the need for alternative powertrain technologies. As a result, some innovators are exploring ways to use hydrogen to power internal combustion (ICE) engine vehicles. So, could ‘Hydrogen ICEs’ be the answer?

Driven by net-zero emissions targets, many automotive OEMs are already heavily invested in developing battery electric vehicle (BEV) models to meet growing consumer demand for low-emission vehicles, while maintaining an interest in hydrogen fuel cell (HFC) technologies for use in the longer term. However, makers of trucks and other heavy vehicles are expected to be more reliant on HFC technologies in the longer term, due to the energy density advantages of HFCs relative to batteries. As more time is needed to develop HFC technologies to the point where they are sufficiently robust and cost-competitive, a growing number of OEMs in this space are exploring interim solutions that could allow them to ‘green’ existing powertrains. For example, this could involve options for converting diesel-powered ICE vehicles for hydrogen use, either as a retrofit or on new vehicles.

Due to their relatively low-cost point, emerging hydrogen ICE technologies could prove viable for transport businesses looking to reduce the carbon footprint of fleets used for heavy load applications, particularly for longer journeys. Many have invested in diesel-powered HGVs and buses, which typically have a lifespan of about 10 years, and replacing them with equivalent HFCEVs or BEVs is simply too costly at this point in time. Several start-ups in the UK and elsewhere are offering conversions of diesel engines to dual fuel or pure hydrogen propulsion as a more cost-effective solution.

From an OEM perspective, the main benefits of hydrogen ICEs are the lower technical and supply hurdles that apply when adapting existing diesel-powered ICE technologies for hydrogen use. This is because hydrogen ICEs largely make use of established technologies and supply chains. Unlike BEVs high-capacity batteries are not required, which reduces the overall cost of the solution while mitigating the risk of supply chain disruption. Hydrogen ICEs are also zero emissions, or near zero emissions, at the point of use.

While they could extend the life of ICE technology, hydrogen ICEs are unlikely to find use in the longer term outside of niche applications. This is because their overall energy efficiency is relatively low compared to other technologies. This is due to factors such as the amount of energy required for the electrolytic conversion of water to hydrogen gas, as well as the energy used for storage and transport, and the thermal losses of the combustion process itself. While it depends on driving patterns and loads, HFCEVs and BEVs provide a more energy-efficient solution for low and normal loads, and during stop-start cycles due to the relative efficiency of battery-powered energy conversion and the possibility of regenerative braking.

Importantly, the use of hydrogen ICE technologies could help the industry to mitigate development and supply-chain risks on route to a greener motoring future. The use of established supply chains, for example, could protect manufacturers from the ‘supply squeeze’ that is expected to impact lithium and cobalt supplies that can only be sourced from a small number of entities in specific regions of the world. The fact that emerging hydrogen ICE technologies are nearing market readiness also means that they could help to accelerate investment in hydrogen infrastructure; de-risking the development and roll-out of HFCEVs in the future.

Among the key examples of emerging technologies, in the US, a Ford patent application (US2022/243673) has recently been published for a dual hydrogen tank arrangement for use in hydrogen ICE vehicles. The first tank contains hydrogen, and the second tank contains a mixture of hydrogen from the first tank and water. Water produced during combustion is fed back into the second tank, which compensates for the loss of pressure that takes place when the hydrogen is used. The water in the second tank can also be injected into the engine when needed to cool the combustion chamber and reduce engine knock.

European commercial vehicle manufacturer, MAN Truck & Bus, has recently had a patent application published (EP3997316) for an innovative hydrogen supply system. Designed for use in a hydrogen ICE vehicle, the system uses heat from both the engine coolant and the exhaust gases to raise the temperature of the hydrogen in two stages to 300^oC+ prior to injecting it into the combustion chamber. The aim is to increase the overall efficiency of the engine by reducing the amount of energy required to release hydrogen from a liquid organic hydrogen carrier or LOHC.

For a variety of reasons, the time is right for hydrogen ICE technologies to come to the fore. With governments and consumers increasingly concerned about energy security and the race to lower emissions, and OEMs concerned about potential EV supply chain disruption, an alternative powertrain technology that is green and available imminently seems particularly attractive. While they are unlikely to be around for the long term, hydrogen ICEs could also help to bridge the gap and accelerate the development pathway to HFCEVs.

Ben Palmer, a partner and patent attorney at Withers & Rogers.