With regulations limiting CO2 emissions ramping up globally, the quest for sustainable transportation has led us to hydrogen as an alternative fuel.
Hydrogen (H) has emerged as a promising option thanks to its ability to burn without any greenhouse gas emissions. This combustible element is colorless, tasteless, odorless, and has relatively high energy density, which means hydrogen contains a lot of energy per unit of volume, making it an excellent fuel source for vehicles.
This lightest element has been receiving considerable interest from the transportation sector for powering electric vehicles via fuel cells. However, hydrogen internal combustion engines (HICEs) are now being explored to achieve zero emissions. But what is it all about?
What is Hydrogen Combustion?
Hydrogen is a chemical element, and combustion is a chemical process that releases energy from a fuel and air mixture. The combustion of hydrogen, whether in liquid or gaseous form, generates force.
Due to its wide flammability range, hydrogen is well-suited for combustion. It provides excellent fuel economy and possesses a high auto-ignition temperature, enabling higher compression ratios that reduce energy loss during combustion. Additionally, a lower final combustion temperature minimizes the number of pollutants emitted via the exhaust.
How Does This Clean-Burning Engine Actually Work in a Vehicle?
Hydrogen, unlike liquid gasoline, is a gas that necessitates a special fuel delivery system. For this purpose, high-pressure storage tanks hold the hydrogen gas, ensuring sufficient fuel storage to meet the demand of a journey.
A control valve, meanwhile, regulates the flow of gas into the engine”s intake manifold, ensuring an optimal air-fuel mixture for efficient combustion. During the intake process, the fuel is mixed with air and introduced into the cylinder.
To achieve clean and efficient combustion, a proper air-fuel mixture is needed. Hydrogen combustion engines employ sophisticated fuel injection systems to minimize harmful emissions and optimize power output.
The piston compresses the appropriate mixture of fuel and air, and high-energy spark plugs then ignite it, resulting in combustion. As hydrogen burns rapidly and releases significant heat, the combustion gases expand quickly.
These expanding gases push the piston, whose motion is converted into rotation power through the crankshaft. This force then propels the wheels, moving the vehicle forward.
This process illustrates the cleaner and more powerful driving experience that hydrogen combustion engines can provide, promising a more sustainable transportation future. However, the rapid speed and high temperatures in hydrogen internal combustion engines (HICEs) are achieved through hydrogen-friendly materials, advanced engine design, and innovative fuel injection technology.
How is it Different From Hydrogen Fuel Cells?
Hydrogen is used in the transportation sector in two distinct ways: through fuel cells and combustion engines. Although both processes use zero-carbon fuel hydrogen, they harness it in different ways to power vehicles.
As mentioned above, hydrogen combustion engines produce power by burning hydrogen, much like traditional engines. Here, hydrogen is mixed with air to create a controlled explosion, generating mechanical energy to propel the vehicle.
Fuel cells and hydrogen vehicles, meanwhile, convert hydrogen into electricity through a chemical process. In this process, an electrochemical device converts hydrogen and oxygen into electricity, heat, and water vapor. More specifically, it generates electricity by splitting hydrogen into a proton and an electron. This electricity then powers an electric motor that drives the vehicle.
Fuel cell vehicles (FCEVs) are more efficient at lower loads, while hydrogen combustion engines perform better under heavier loads. This makes HICEs a better choice for heavy trucks that haul large loads most of the time. In contrast, cars, buses, and tow trucks may benefit more from fuel cells, as they usually operate under much lower loads.
However, given that both utilize hydrogen, they produce similar emissions. Fuel cell vehicles generate no emissions, while hydrogen combustion engines emit near zero trace amounts of CO2, although they can produce NOx or nitrogen oxides. Additionally, hydrogen engines can operate with lower-quality hydrogen, which allows for specific use cases.
Hydrogen internal combustion engines have been in use for decades and do not require a change in infrastructure. So, for vehicle manufacturers, switching to a hydrogen engine is less challenging due to the use of existing technology. Fuel cells, on the other hand, are lighter, quieter, and noted for their high efficiency. They convert up to 60% of the energy stored in hydrogen into electrical power.
Because they operate at a lower temperature than combustion engines, fuel cells also have a lower risk of fire or explosion. However, as they are a relatively new technology, fuel cells are a more expensive option than hydrogen combustion engines.
This doesn’t mean they are competing with each other, but rather, HICEs and FCEVs complement one another. After all, both involve the same hydrogen production, storage, transportation, and distribution infrastructure and are part of reducing transportation emissions towards zero.
Weighing the Pros & Cons of Hydrogen Combustion
So, the use of hydrogen clearly has significant advantages, but what about hydrogen combustion in particular? Well, as we stated above, the main benefit is the environmental impact of HICEs.
These engines are known for having a clean byproduct, primarily water vapor, offering a significant advantage over traditional gasoline engines. Besides contributing to lower greenhouse gas emissions, hydrogen combustion engines have much higher thermal efficiency at about 45% than diesel engines, which have under 40%, and petrol engines, which have below 30%.
Another big benefit of HICEs is that they can be built using existing internal combustion engine technology, so there is no need for additional infrastructure or retraining the workforce. Moreover, the element itself can be produced from various sources such as biomass, water electrolysis, and natural gas, hence capable of meeting the rising demands for clean energy.
The case for hydrogen as a fuel is certainly strong, but that doesn’t mean there aren’t any issues involved. In fact, hydrogen combustion engines face several challenges that need to be addressed.
For starters, we need large storage space for hydrogen tanks, which adds a substantial amount of weight to the vehicle. This, of course, increases the risk of wear and tear, hence reducing the life of the vehicle. The fuel also burns pretty easily, which means there are dangers to engine parts. Harnessing hydrogen is not easy either. It is a time-consuming and energy-intensive process.
Meanwhile, its energy density is less, meaning the power generated is relatively less than that of conventional combustion engines. Compared to other fuels like petrol, which need a compression ratio of 8:1, hydrogen combustion engines need 40:1, which presents another issue. Not to mention, mass-producing these engines is an expensive task.
While hydrogen is chosen for its lower emissions, the combustion engine still creates a carbon footprint as it involves some NOx emissions, negating the very purpose of these engines. As such, managing the heat and any remaining emissions through after-treatment systems is important.
Click here to learn the safety concerns around hydrogen vehicles.
Is Hydrogen Combustion Engines the Future?
Hydrogen combustion engines (HICEs) have been around for decades. The world’s first experimental commercial aircraft to operate on liquid hydrogen, Tupolev Tu-155, took to the skies in 1988. This shows that HICEs are not as new as many might think.
Despite not gaining widespread adoption over the years, HICEs have recently attracted renewed interest from big automobile brands, including Toyota, Bosch, Honda, Cummins, Daimler, Suzuki, and Volvo. Even the aviation sector has been exploring hydrogen combustion. Airbus, for instance, has been collaborating with partners across industries for its ZEROe concept aircraft, which is designed to run on hydrogen combustion.
There’s a rising interest in using hydrogen combustion engines in the transportation sector, but for now, they are facing intense competition from electric vehicles (Vs).
While HICEs produce near-zero emissions, EVs depend on electricity for power and, as such, boast zero tailpipe emissions. EVs also have higher energy efficiency compared to HICEs, which lose some energy during the combustion process.
Although EVs require a new infrastructure, the number of charging stations is rapidly rising. Stations to refuel hydrogen, on the other hand, are rather scarce, though refueling a hydrogen car is quicker than charging an electric car.
Companies like BYD, Tesla, Rivian, General Motors, Volvo, and many others have been making massive strides in the field of EVs. The electric vehicle (EV) market was valued at approximately $384 billion in 2022, while the global market for hydrogen internal combustion engines (HICEs) is projected to reach $35 billion by 2030.
Car manufacturers are now experimenting with hydrogen combustion technology, but the progress is relatively slow compared to advancements in EV technology. The industry needs to overcome many production hurdles, such as cost, which means EVs will continue to dominate the transportation sector for the time being. However, HICEs can become an important part of the transportation fuel mix in the near future.
Hydrogen simply can’t be ignored as a fuel, and HICEs have a crucial role to play in the future of sustainable transportation. However, to make that possible, government support and technological advancement are needed.
Click here to learn why hydrogen may still be the fuel for the future.
Recent Developments in the Field of HICEs
Over the past decade, decarbonization has become extremely important for countries and companies worldwide. The transportation sector is particularly critical, given that it produces 10% of the world’s greenhouse gas emissions.
According to the Paris (COP21) and Glasgow (COP26) agreements, transportation propulsion tech needs to rapidly reduce CO2. For that, we need an effective solution, but there isn’t one that can provide all the answers. A mix of different solutions can actually help mitigate the issues more effectively. This includes hydrogen combustion engines, which require minimum changes to the current vehicle architecture.
As a logical and highly efficient option, HICEs are seeing a lot of traction and advancement. Recently, researchers at the University of Alberta have come up with a new coating material that looks promising for hydrogen combustion engines. The new complex concentrated alloy, AlCrTiVNi5, has superior thermomechanical properties, including low expansion, high stability, fracture tolerance, and the ability to withstand high temperatures as well as high-pressure environments.
Comparing the new coating with existing commercially available alloys, researchers found AlCrTiVNi5 surviving “corrosive environments for up to 100 hours at 900 degrees Celsius” and “outperforms anything else on the market right now,” hence opening the door for advancing the hydrogen economy.
Earlier this month, Toyota also announced that in an effort to make hydrogen combustion viable, it has created an internal combustion engine that can run on synthetic fuel, biodiesel, gasoline, and hydrogen. To make this happen, engineers used a 1.6-liter engine from the GR Corolla race car, which helped the company overcome the challenge of balancing thermal efficiency. Its new engines are 10% to 20% smaller but are more powerful.
According to Toyota CEO Koji Sato, hydrogen is the future, and the company is:
“Developing this engine as part of its efforts to achieve carbon neutrality and promote the use of hydrogen as a clean and renewable energy source.”
This development surrounding hydrogen is happening all over the world. Late last year, India’s largest automobile company, Tata Motors, unveiled R&D facilities that involve an engine test cell for the development of HICEs as well as the infrastructure for storage and dispensing of hydrogen fuel.
This year, Tata collaborated with US giant Cummins for a manufacturing facility in India for HICEs for both medium and heavy commercial vehicles. This comes after the joint venture announced last year that it would spend $424 mln on the factory to produce 4,000 H2 engines a year and 10,000 battery systems.
Companies Developing Hydrogen Combustion Engines
Now, let’s take a look at a couple of big names in the sector:
#1. Honda
This car manufacturer has been actively engaged in hydrogen combustion engines via a collaborative project called HySE (Hydrogen Small Mobility & Engine Technology) with Toyota, Yamaha, Kawasaki, and Suzuki to explore the potential of HICEs. Initially skeptical about the technology’s feasibility, Honda developed the ‘HySE-X1′, which features a 1.6-liter four-cylinder hydrogen-powered engine.
Honda is a $56.188bln market cap company whose shares are currently trading at $31.93, up 3.25% YTD. The company’s revenue (TTM) has been $130bln, EPS (TTM) of 7.37, P/E (TTM) of 4.33, and a dividend yield of 4.19%.
#2. Toyota
This Japan-based auto manufacturer has been using hydrogen as a fuel for many decades now. Its hydrogen combustion vehicles include the GR Corolla H2 and the GR Yaris H2. Toyota also participated in the Super Taikyu endurance races to accelerate its vehicle development. Just this week, Toyota showed its new engines that can run on different fuels, including hydrogen.
Toyota is a $314bln market cap company whose shares are currently trading at $198.86, up 8.53% YTD. The company’s revenue (TTM) has been $287bln, EPS (TTM) of 24.18, P/E (TTM) of 8.22, and a dividend yield of 2.45%.
Conclusion
It is clear that hydrogen combustion engines offer great benefits in terms of reduced environmental impact, reliance on existing infrastructure, and high thermal efficiency. But of course, HICEs alone won’t be able to provide sustainable transportation. Rather, through a mix of solutions, we can achieve a safer environment. In that mix, though, HICEs can play a crucial role and help transition away from fossil fuels.
Now, after decades of unrealized potential, hydrogen-powered vehicles may finally be in the spotlight thanks to renewed interest, private investments, government support, and technological advancements.
Click here to learn what made hydrogen more attractive as an energy source recently.