Combustion Engines Might Not Be Dead After All
Combustion Engines Might Not Be Dead After All
AVL's 410 hp 2-litre hydrogen engine could be a game changer.
Like it or not, the combustion engine is a part of our culture. From the emotional V12s of the ’60s sports cars to the screaming V10s of early naughties F1 and even the thrum of a utilitarian diesel truck. These vehicles not only have a historical importance, but their feel, sound and sensations have been a core part of our daily lives for over a century. What’s more, their feel and sound are so reminiscent of a living creature, with its breathing, gasping, roaring, and slight unpredictability, that we easily become deeply emotionally connected to these lumps of animated metal. So, even though EVs are now better in almost every measurable way, from efficiency, comfort, pollution, longevity, cost and even power, the EV revolution will strip us of a cultural emblem. But, thanks to AVL’s incredible hydrogen engines, our combustion engines might actually have a place in our environmentally harmonious future.
Hydrogen engines have been around for a long time as a carbon-neutral alternative to gasoline. You see, when hydrogen combusts, it only produces heat, energy and water. That’s it! This means that, in theory, you can run a typical 4-stroke gasoline engine on hydrogen and have no impact on Mother Earth.
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However, hydrogen ICE (internal combustion engine) technology has some serious drawbacks. While hydrogen has a far higher potential energy per gram than gasoline, it is far less dense and combusts far more easily. This means that the engine can struggle to get enough hydrogen, limiting total power and efficiency. Its ease of ignition also makes the engines susceptible to pre-ignition, also known as knocking, which again limits power and efficiency.
This can be clearly seen with BMW’s concept Hydrogen 7 series. Its engine was the same as the 760i but had been modified to run on either gasoline or liquid-compressed hydrogen. When using either fuel, the 6-litre V12 engine produces only 260 hp, 40% less than the engine made before being modified. This made it rather lethargic, and could only do 0–62 mph in 9.5 seconds, or 43% slower than the standard 7 series it was based on. Being such a vast engine, it was hardly efficient, and using gasoline averaged 16.9 mpg. When running on hydrogen, it was far worse and consumed 100 L/100 km, or the equivalent of 4.7 mpg! As the hydrogen tank only held 8 kg of fuel, this insanely terrible efficiency meant it could only do 125 miles on hydrogen.
Needless to say, BMW didn’t take this concept any further, and the only prototype they built is now safely stored away in BMW’s Museum.
But, a company called AVL has used a surprisingly eco-friendly technology to solve these problems and has made a kick-arse hydrogen racing engine with it!
This engine is called the AVL H2 ICE Race, and it is small at only 2-litre and 4 cylinders, but it is turbocharged and water injected. Water injection is a rather old technology which injects cold distilled water into the air-fuel mixture. This cools the mixture and specific parts of the engine and, in doing so, tackles premature ignition. This allows engines to run at far higher compression ratios (how much the engine compresses the air-fuel mixture before ignition) and, in turn, enables it to make more power and be far more efficient.
This engine was recently bench-tested and produced a whopping 410 hp at 6,500 rpm and 500 Nm of torque at 3000–4000 rpm. This puts it on par with other high-performance engines, such as the one found in the Mercedes-AMG A45. This 2-litre gasoline engine has one of the highest specific outputs (power per litre of displacement) on the market and is the most powerful 4-cylinder consumer engine ever. It produces 416 hp at 6,750 rpm and 500 Nm at 5,000 rpm.
This breakthrough means that lightweight, high-power performance vehicles can now operate carbon neutrally without losing any of the culture or emotion. What’s more, as hydrogen fuel is lighter than gasoline, using AVL’s technology could make these cars lighter and, therefore, faster!
Sadly, we don’t yet know the efficiency of this engine. However, that shouldn’t be surprising as it was designed and tuned as a racing engine, and its application isn’t concerned about fuel efficiency. But, AVL does have a different hydrogen combustion engine that is designed for efficiency.
AVL’s H2-HDPI (High-Pressure Direct Injection) engine doesn’t have water injection but uses other proprietary technology from AVL. Simulations have shown that this engine can achieve 47% thermal efficiency. For some context, most gasoline cars only have a thermal efficiency of 30%. Not only does this make the H2-HDPI more efficient than gasoline cars, but it also makes it as efficient as hydrogen fuel cells while being cheaper and easier to produce than hydrogen fuel cells! According to a report by Westport Fuel Systems and AVL, this “makes H2-HPDI the most capital efficient means to use hydrogen and lower CO2 emissions near-term and that it has the potential to remain competitive with fully scaled FCEV (Fuel Cell Electric Vehicles) in the future.”
Okay, so AVL seems to have solved the riddle of carbon-free transport. They have made hydrogen engines as powerful and as efficient as our current dino-juice engines, which emit no harmful gases into the atmosphere. To top it off, these engines are even cheaper than hydrogen fuel cell technology! Should we abandon EVs and just adopt this instead?
Well, no. There are still a few problems.
The main one is overall efficiency. If you want to run a hydrogen engine, you need hydrogen. Most hydrogen comes from natural gas, and isolating it produces a lot of carbon dioxide, so we obviously can’t use it. Alternatively, “green hydrogen” comes from water electrolysis, which produces oxygen and hydrogen with renewable electricity without emitting carbon. However, this process is only 80% efficient, and the hydrogen engine itself is only 47% efficient. This means that for every kWh of renewable energy used to create green hydrogen for hydrogen combustion engines, only 38% of that energy actually goes into useful work. That doesn’t even account for the energy lost to transporting hydrogen from the electrolysis plant, and into the car. Alternatively, energy grids only incur at most 8% losses, EV charging is nearly 100% efficient, and EV drive trains are at least 70% efficient. This means that for every kWh of renewable energy used to charge an EV, 64% goes into useful work.
This means EVs are overall 68% more efficient than hydrogen combustion engines (and hydrogen fuel cells). This is why hydrogen technology, as it currently stands, can only be used for niche purposes. We can’t afford to use such an inefficient technology as a widespread transport solution, as it would make the mountain to net-zero higher than it needs to be.
There are other problems with hydrogen. There is no infrastructure to refuel these machines, and creating this infrastructure will cost billions and billions and take years! What’s more, these combustion engines actually do produce dangerous gases, like nitrous oxides and water vapour. Nitrous oxides damage our respiratory system and deplete the ozone layer. Water vapour only stays in the atmosphere for a short time, but it is a potent greenhouse gas, and vast amounts of it can dramatically change the local weather. As such, using this technology en masse in a condensed location, like a city, is really not a good idea. Hydrogen itself is also a very, very potent greenhouse gas, so if there are any leaks in the green hydrogen infrastructure, it could be exceptionally damaging.
So, does that mean AVL’s technology is useless? Not at all; it just isn’t applicable for everyday vehicles. This technology could be revolutionary for motorsport, heavy industry, aviation, maritime or maybe even motorbikes. The vehicles in these industries need to be light, cheap, powerful, efficient, capable of operating for long stints (i.e. carry more energy capacity than batteries currently allow) and don’t require a widespread infrastructure to work (possibly not motorbikes though…). So, while you might own an AVL-powered daily driver any time soon, this really could help us achieve net-zero. As a bonus, those screaming, emotional combustion engines that make motorsport so impactful can potentially stay a part of our culture, thanks to AVL.
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Sources: AVL, AVL, Green Car Congress, Digital Initiative, Level-Infrastructure, Renewable Energy World, EIA, Power Plug, Engineering Explained, EDF, Queensland Government