"Hydrogen Internal Combustion Engine Vehicles: Advantages, Challenges, and Future Potential"

 A hydrogen internal combustion engine vehicle (HICEV) is a type of hydrogen vehicle that uses an internal combustion engine (ICE) to generate power. Unlike hydrogen fuel cell vehicles that use electrochemical reactions to produce electricity, HICEVs modify traditional gasoline-powered internal combustion engines to run on hydrogen fuel. These vehicles have several advantages, such as the absence of carbon emissions, as hydrogen combustion does not produce carbon dioxide (CO2). However, hydrogen combustion engines are not considered zero-emission vehicles because they can produce oxides of nitrogen (NOx), similar to other high-temperature combustion fuels like gasoline or diesel.

Hydrogen internal combustion engines have a long history, with early designs dating back to the 1800s. Over the years, various manufacturers and research institutions have developed hydrogen-powered engines, including Mazda with their hydrogen rotary engines and BMW with their Hydrogen 7 luxury car. HICEVs have also been used in applications such as forklift trucks and have gained interest for heavy-duty commercial vehicles as a bridging technology to meet future climate goals.

The efficiency of a hydrogen combustion engine can be similar to that of a traditional combustion engine, with slightly higher efficiencies achievable through optimization. However, efficiency decreases for smaller engines. Hydrogen combustion engines do produce oxides of nitrogen (NOx), but they have little to no carbon monoxide (CO), carbon dioxide (CO2), sulfur dioxide (SO2), hydrocarbon (HC), or particulate matter (PM) emissions. The emissions levels are significantly lower than those of gasoline or diesel engines.

Adapting existing engines to run on hydrogen requires modifications such as hardened valves and valve seats, stronger connecting rods, modified fuel injectors, and higher voltage ignition systems. The cost of modifying an engine for hydrogen use is estimated to be about 1.5 times the cost of a gasoline engine.

Overall, hydrogen internal combustion engines offer a potential solution for reducing carbon emissions in transportation and can be considered as part of hybrid powertrains to provide short-term zero-emission capabilities. However, advancements in hydrogen fuel cell technology and the growth of hydrogen infrastructure may lead to a shift towards fuel cell vehicles as a more viable long-term solution.

Hydrogen internal combustion engine vehicles have a long history dating back to the early days of internal combustion engine development. François Isaac de Rivaz designed the first internal combustion engine in 1806, which ran on a mixture of hydrogen and oxygen. Since then, several advancements and modifications have been made to internal combustion engines to enable them to run on hydrogen.

One advantage of hydrogen internal combustion engines is that they can use existing engine technology with relatively low retooling costs. This makes them a viable option for applications where fuel cells may not be practical or economically feasible, such as in cold-weather environments.

In recent years, there has been growing interest in hydrogen internal combustion engine development, particularly for heavy-duty commercial vehicles. These vehicles are seen as a bridging technology to meet future climate goals and provide a more familiar and compatible solution within the existing automotive industry.

One notable example of a hydrogen internal combustion engine vehicle is the BMW Hydrogen 7, which was tested between 2005 and 2007. It achieved impressive speeds and demonstrated the potential of hydrogen as a fuel for high-performance vehicles.

Efficiency is an important aspect of hydrogen combustion engines. While the thermal efficiency of an ideal Otto Cycle can be improved by increasing the compression ratio, practical engines achieve about half to three-quarters of the ideal efficiency. However, with optimization, hydrogen combustion engines can achieve comparable efficiency levels to hydrogen fuel cells, particularly for heavy-duty applications.

In terms of emissions, hydrogen combustion engines produce water vapor as the only byproduct, making them free of carbon dioxide (CO2) emissions. However, they can produce oxides of nitrogen (NOx), similar to other high-temperature combustion fuels. Nevertheless, the emissions of carbon monoxide (CO), hydrocarbons (HC), sulfur dioxide (SO2), and particulate matter (PM) are significantly lower compared to gasoline or diesel engines.

Adapting existing engines for hydrogen combustion requires certain modifications, including hardened valves and valve seats, stronger connecting rods, fuel injectors designed for gaseous fuel, and higher temperature engine oil. These modifications increase the cost of the engine but enable it to run efficiently on hydrogen.

Research and development on hydrogen internal combustion engines are ongoing, with collaborations between automotive manufacturers, universities, and research organizations. These efforts aim to further improve the performance, efficiency, and emissions of hydrogen combustion engines and explore their potential as part of hybrid powertrains.

Overall, hydrogen internal combustion engine vehicles offer an alternative to hydrogen fuel cell vehicles and have the advantage of utilizing existing engine technology. While they are not zero-emission vehicles, they can provide a practical solution for specific applications and contribute to reducing greenhouse gas emissions in the transportation sector.