Professor Xinyan Wang, a member of the Centre for Advanced Powertrain and Fuels at Brunel University of London, and his colleagues have worked on roughly 20 hydrogen engine projects in the past five years. Those projects demonstrated a variety of enticing benefits, he told attendees at Engineering a Hydrogen Economy 2026, held at the Millennium Point conference centre in Birmingham from 29 to 30 April.
As with fuel cells, hydrogen combustion engines – modified internal combustion engines that use hydrogen instead of fossil fuels – produce zero carbon emissions. Brunel tests on converted petrol and diesel engines, including a project with Mahle Powertrain, also showed reduced nitrogen oxide (NOx) emissions, higher efficiency than petrol and thermal efficiencies of 59% (comparable with fuel cells), Wang said. He and his team are now working on a dedicated engine to push that efficiency even further.
Just a matter of time?
Those advantages sound too good to ignore – so why, when we look at cars on the road, are none of them powered by hydrogen combustion? “It’s a question we ask ourselves,” Wang told Professional Engineering after his presentation. “The fact is the government doesn’t recognise the hydrogen combustion engine as a zero-emission propulsion system… An engine or even a fuel cell is complicated; it’s not as simple as EVs. So I think it’s just a matter of time… [all] people and organisations working on hydrogen, we need to come together, ready to show a good business case.”
While hydrogen combustion vehicles are recognised as zero-CO2 under the Vehicle Emissions Trading Schemes, they are not classified as zero-emission due to the presence of non-CO2 tailpipe emissions, a spokesperson for the Department for Transport said. Efficiencies against the CO2 targets can nonetheless be converted towards zero-emission vehicle target compliance, so manufacturers would be incentivised to sell them in the UK should they become available. Brunel University has an ongoing series of engagements with government representatives to tackle their classification, Wang said.
Other issues include simply “getting the fuel into the tank”, one Hydrogen Economy attendee pointed out, due to the expense and the very high pressures required for the still relatively low-density fuel.
If the boosting system is not upgraded on converted engines, power can drop because hydrogen’s low density – and the need to run lean to control NOx – increases the engine’s airflow and boost requirements. An advanced boosting system can recover much of that lost power, while another option is to use a larger engine, reducing the need for more complex optimisation or additional components.
As with other hydrogen applications, any widespread use of the fuel will require a massive increase in production, storage and distribution.
Proof of concept
Solving those challenges means it will take some time for hydrogen combustion cars to appear on our roads. However, the technology is finding a home elsewhere.
Under pressure to decarbonise but often far from convenient grid connections, construction sites including the Lower Thames Crossing project are starting to use JCB diggers powered by the company’s own UK-developed hydrogen combustion engine.
That engine was even adapted for the Staffordshire firm’s Hydromax car, which this summer set a new world hydrogen land speed record of 406.32mph (653.91km/h) at the Bonneville Salt Flats in Utah.
Involving IMechE member Ben Hassett and IMechE fellow Matt Beasley in key roles, the project surpassed the hydrogen internal combustion benchmark of 185.5mph (298.5km/h) set by the BMW H2R in 2004, the 350.092mph (563.418km/h) world diesel land speed record set by JCB Dieselmax in 2006 and the 303mph (488km/h) hydrogen fuel cell mark set by the Venturi Buckeye Bullet 2 in 2009. This achievement made Hydromax the fastest hydrogen-powered vehicle of any kind in history.
Speaking earlier this year, powertrain engineering director Ryan Ballard told Professional Engineering the team was motivated to prove critics wrong. “When we started our production programme for the hydrogen engines, there were an awful lot of people very eager to tell us what a bad idea it was, and that the efficiency would be bad. We proved them wrong there,” he said. “People would talk about NOx emissions, and we dealt with that; we’ve dealt with that very effectively.”
Much of the Hydromax engines was carried over from the production engines, with shared elements including the block, head, crank, pistons and valve train. The fuel system was upgraded to bring in more fuel, as was the boosting system to increase the amount of available air. Hydromax, along with more deployments of the hydrogen-powered diggers, will attract more attention to the relatively novel powertrains.
Offering emissions advantages over petrol, quicker refuelling than EVs and a way to use renewable energy that might otherwise be wasted, it would be wrong to discount hydrogen combustion cars on the road just yet.
“Anything’s possible as an engineer,” Ballard said. “Your imagination is the limit.”
Want to learn more about hydrogen combustion engines? The Hydrogen Propulsion and ICE conference at IMechE’s upcoming Advancing Automotive Engineering event (4-5 November) will share developments and explore applications at the British Motor Museum in Warwick. Find out more.
Want the best engineering stories delivered straight to your inbox? The Professional Engineering newsletter gives you vital updates on the most cutting-edge engineering and exciting new job opportunities. To sign up, click here.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.