Hydrogen Internal Combustion Engines 2025-2045

For over a century, internal combustion engines have reigned supreme in the automotive sector. Cars, buses, trucks, excavators, ships, and airplanes have all relied on complex machinery to harness the explosive force of combustion, translating it into motion through a sophisticated interplay of components including pistons, carburetors, camshafts, flywheels, differentials, and wheels. While internal combustion engines (ICEs) have long been the cornerstone of the automotive industry, mounting concerns about their carbon emissions have fueled a push for alternative “emissions-free” solutions.

 

The battery electric vehicle (BEV) presents a radical shake-up of the industry with its simple yet powerful setup that harnesses electricity from a battery to propel a motor, resulting in superior drivetrain efficiencies and zero tailpipe emissions. The phenomenal growth of BEV sales, especially in the passenger car market, has been aided by governments across the world calling time on ICEs and setting deadlines for the end of their production. However, the BEV is still hampered by issues of limited range, underdeveloped infrastructure, and expensive batteries. These are improving but still present a barrier to adoption, particularly in the most demanding automotive sectors (such as construction and long-haul trucking).

 

Amid growing concerns, the quest for alternative solutions persists, with some industry players optimistic about the potential to sustain the combustion engine. Hydrogen internal combustion engines (H2ICE) operate on gaseous, carbon-free hydrogen instead of traditional fuels, offering nearly zero tailpipe emissions while leveraging existing engine architecture with some essential modifications. Despite its historical roots in the 1800s, interest in hydrogen engines had previously been on the fringe, with sporadic experimental prototypes. The renewed curiosity in this technology begs the question of whether the transport decarbonization efforts will lead to a breakthrough for H2ICE.

 

The IDTechEx report offers a thorough technical examination of hydrogen engine combustion processes, exploring how hydrogen’s chemical properties influence injection strategies and engine operation modes, with a focus on the challenge of minimizing nitrogen oxide (NOx) production to maintain zero-emissions integrity. The report provides a comprehensive assessment of the mechanisms and causes of NOx formation in H2ICE, along with treatment options for the exhaust gas. The air-fuel ratio significantly influences thermal NOx production, driving the rise of lean burn trends in H2ICEs. Current exhaust gas after treatment systems (EATS) for modern diesel vehicles are becoming increasingly intricate and advanced to meet stringent NOx emissions standards. IDTechEx has evaluated various EATS options for H2ICE vehicles, including three-way catalytic converters, lean NOx traps, and selective catalytic reduction (SCR) with urea dosing. Real-world case studies offer insight into how effectively these technologies can limit NOx in H2ICE.

 

While the engine itself may bear a resemblance to a traditional diesel or petrol ICE with some modifications, big differences arise when it comes to storing hydrogen for H2ICE vehicles. Hydrogen is the lightest element in the periodic table, and as such an enormous amount of energy can be contained per kg of weight. However, it is the volumetric energy density that poses a major challenge. At ambient pressure and temperature, diesel contains over 3000 times the energy as an equivalent volume of gaseous hydrogen.

 

 

An H2ICE is also less efficient than an FCEV, so requires more hydrogen per km traveled than a fuel cell vehicle. To achieve a meaningful range for H2ICE vehicles, hydrogen needs to be stored in a more energetically dense format, typically through compression in 350-bar or 700-bar tanks. Additionally, the use of liquid-cooled or cryo-cooled hydrogen is being explored, as it contains more energy per unit volume, although it brings its own significant challenges, such as hydrogen boil-off. Even with liquid hydrogen, the volumetric energy requirements for the fuel alone are greater in liters/km traveled than for H2ICE than a BEV when not considering the tank and cooling equipment required, according to IDTechEx analysis.

 

In view of these challenges, IDTechEx thoroughly evaluates the potential and likelihood of success for H2ICE across various sectors, encompassing passenger cars, aviation, non-road mobile machinery, and goods transportation, each of which poses unique obstacles for decarbonization. The report seeks to provide an insightful analysis of hydrogen ICE, addressing emissions, technical and economic hurdles (including green hydrogen production and distribution costs), and comparisons with established drivetrains such as BEV and FCEV. Additionally, it includes market forecasts for sectors poised for H2ICE vehicle growth and offers commentary on the limited future of hydrogen in other sectors.