The Hurdles of Hydrogen Engines: Why They Fall Short of Expectations

Hydrogen engines are often viewed as a promising alternative to traditional internal combustion engines, promising a cleaner driving experience with minimal pollution. However, the truth is more complex. In this article, we explore the challenges facing hydrogen engines and why they may not live up to the hype.

How Does a Hydrogen Engine Work?

At first glance, the operation of a hydrogen engine seems simple, mirroring that of a gasoline or diesel engine. Hydrogen and air are injected into a cylinder, ignited with a spark, and the resulting combustion produces expanding water vapor that pushes the piston down and turns the crank. The exhaust is then released. This process sounds promising: the fun of piston-powered motoring with none of the pollution.

Thermal and Environmental Challenges

Unfortunately, this is where the story takes a turn for the worse. Hydrogen burns at higher temperatures compared to gasoline or diesel. This higher temperature is a significant issue because it leads to increased nitrogen oxide pollution, a byproduct that forms at high temperatures and pressures. The increased heat also poses another problem: cooling the engine becomes more difficult, and it places more strain on engine components such as pistons, rings, and valves.

Despite these challenges, engineers have certainly tried to mitigate these issues. For instance, Toyota, facing pressure to avoid developing electric vehicles, has attempted to develop hydrogen engines. However, such solutions come at a cost, often involving complex and costly exhaust gas recirculation systems that can only partially address the problem.

Storage and Distribution of Hydrogen

The storage and distribution of hydrogen present another major hurdle. Hydrogen can be stored in three main ways: giant gas bags, compressed cylinders, or liquid cryogenic hydrogen. Each method has its own set of problems. Cryogenic hydrogen, at -253°C, is extremely difficult to handle and is prone to vaporization over time. Gas bags are also not ideal, being huge and potentially dangerous in case of a leak or fire. Compressed cylinders are the most practical solution used in current hydrogen vehicles, but they are still a significant challenge. These cylinders are cylindrical to withstand high pressure and are not easily packaged in vehicles, leading to space issues.

Even hydrogen combustion engines are not as efficient as they could be. Hydrogen combustion is about 20% efficient, meaning that a large space is required for the hydrogen storage tanks. In contrast, fuel-cell hydrogen cars, which do not burn hydrogen, achieve around 50% efficiency and require much less storage space. This leaves the hydrogen combustion engine struggling to meet the demands for a reasonable range of 300 miles, especially for powerful engines.

Comparing Hydrogen to Electric Vehicles

The inefficiencies of hydrogen engines become even more apparent when compared to electric vehicles (EVs). EVs are not only four times more efficient, but they also offer a better package in terms of space. While hydrogen tanks take up less space than batteries in an EV, the overall efficiency and handling of batteries make EVs superior. Moreover, the environmental impact of producing and using hydrogen is higher compared to EVs. Producing and compressing hydrogen is inefficient and therefore expensive, and green electricity is required to reduce CO2 emissions.

Furthermore, there are competing technologies like battery electric vehicles (BEVs) that can leverage green electricity with greater efficiency. Whereas hydrogen combustion vehicles waste 80% of the energy, BEVs waste only 20%. This stark inefficiency raises the question of whether hydrogen technology is a viable solution in the long term. Instead, the focus should be on direct utilization of green electricity or the efficient charging of batteries.

Conclusion

Hydrogen engines, while an intriguing concept, face numerous challenges that make them less attractive than they might appear initially. Long-term, electric vehicles appear to be the more sustainable and efficient solution for clean transportation. As the technology for producing and storing hydrogen improves, we must view it as a potential enhancement rather than a replacement for more established and efficient solutions like EVs.