Increasingly stricter emission rules are making it tough for automakers to continue offering cars powered by internal-combustion engines, with some countries such as the United Kingdom even making moves to ban the engines altogether.
Interestingly, hydrogen, of all things, could prove to be the savior of the internal-combustion engine.
A number of automakers have proposed transforming hydrogen generated from renewable sources into carbon-neutral synthetic fuel. Porsche and its partners have even built a pilot plant capable of producing synthetic fuel at industrial scale.
Toyota is now testing another, much older solution involving hydrogen: burning the stuff directly in an internal-combustion engine.
The automaker last week unveiled a race car whose inline-3 engine is designed to run on pure hydrogen. The race car is still being tested but will enter a round of the 2021 Super Taikyu Series race series in Japan this May.
As mentioned, this solution isn't new. BMW has presented a 7-Series prototype whose V-12 engine could run on hydrogen. That was back in 2006. The main modifications required involve the fuel storage and fuel injectors.
When burning hydrogen, there are zero CO2 emissions. However, the technology is not without its drawbacks. Burning hydrogen in an internal-combustion engine produces harmful nitrogen oxides. However, there are ways to minimize this, like using urea-based selective catalytic reduction like in modern diesel engines.
The bigger issue, as we've previously explored, is the poor efficiency. Energy is already wasted in generating the hydrogen from renewables, and by the time the hydrogen is burned in an engine and the power transferred to a transmission and ultimately the wheels, only about 25% of the energy value of the hydrogen is actually transferred.
That's why fuel-cell-electric cars like the Toyota Mirai make more sense when using hydrogen as a fuel. Here the hydrogen is combined with oxygen from the air to create electricity which then powers an electric motor that can directly power the wheels. Here the efficiency is closer to 50%. And there are also no harmful emissions. Just water.
Another drawback of hydrogen? There's no infrastructure in place to cleanly source the stuff and supply it to customers. That's why battery-electric cars, which can use the existing electrical grid, will likely be the main source of personal transport in the future, though hydrogen may still have a place in long-haul transport.