Kawasaki hydrogen motorcycle prototype
By Ben Purvis
Back in 2022, Kawasaki showed design drawings for a proposed hydrogen-powered sports tourer as well as a prototype hydrogen combustion engine based on its 998 cc supercharged 'H2' four-cylinder. But even so, it was a surprise to see a real prototype of the bike take to the stage during the company's Group Vision 2030 Progress Report Meeting.
The debate over hydrogen's future as a fuel - whether for fuel cells that use it to generate electricity or in more conventional combustion engines - is a hotly debated topic at the moment. Some car makers, most notably Toyota, is throwing its weight behind hydrogen, and Kawasaki, while at the forefront of Japanese companies when it comes to electric and hybrid motorcycles, is also a vocal proponent of hydrogen.
Hydrogen is the most abundant element in the universe, it's highly flammable and when burnt it combines with oxygen to form water. But there are issues. Most of Earth's hydrogen is already tied up in water and extracting it is an energy-intensive process, requiring a lot of electricity. Once extracted, hydrogen's tiny molecules and lack of density make it hard to store and transport. Kawasaki's involvement with hydrogen goes well beyond the motorcycle arm of the business, though, with the company also involved in refining low-quality 'brown' coal into hydrogen, and in 2020, Kawasaki's shipbuilding division launched the Suiso Frontier - the world's first liquified hydrogen carrier ship, able to carry hydrogen in a cryogenically cooled state at -253 degrees C, making it 800 times as dense as in its normal gaseous state.
Kawasaki's prototype hydrogen bike uses a specially developed version of the supercharged four from the H2 range, modified to add direct fuel injection so the hydrogen can be added to the combustion chamber after the intake valves have closed. That is essential, as is supercharging, to create an engine with power on a par with conventional petrol engines. The other big problem with hydrogen is clear to see from Kawasaki's prototype - it's the volume of space that the gas takes up. While it's more energy-dense than petrol in terms of weight, hydrogen is far less energy-dense in terms of volume, so even when it's compressed to around 700 bar (10,000 psi) you need a large tank to get much range. Those panniers on Kawasaki's prototype aren't for luggage: they're packed with swappable hydrogen canisters. Swappable canisters are one option when it comes to refuelling because, of course, hydrogen can't just be poured into a tank - it needs high pressures and low temperatures, so swapping pre-filled canisters is a safer alternative to refuelling a built-in tank.
The hydrogen prototype is still clearly a long way from being a production machine - there isn't the infrastructure to support such a bike even if it was available for sale - but in the context of the recent EU 2035 law changes, it's a technology demonstrator that shows how motorcycles might evolve in the future. Especially if hydrogen gets a foothold in the car market and batteries can't be made compact and light enough to create a high-powered, long-range motorcycle that can replace today's petrol machines.
