Retrofitted Hybrid Diesel Engine - hydrogen

A New Retrofitted Hybrid Diesel Engine Runs On 90% Hydrogen

A direct injection dual-fuel system developed at the University of New South Wales (UNSW) in Sydney, Australia allows diesel engines to be converted to run on 90 percent hydrogen. By retrofitting the polluting diesel engines with the hybrid alternative drive, it is possible to operate heavy vehicles and machinery on green hydrogen, a clean energy source generated from renewable power, and reduce their carbon emissions by over 85 percent to 90 g/kWh.

According to Shawn Kook, a professor at the UNSW School of Mechanical and Manufacturing Engineering, the hybrid engine could be quickly retrofitted to existing heavy-duty equipment and help bring down their carbon footprint. This is particularly relevant in Australia, where diesel-powered vehicles are a mainstay of the mining industry that accounts for over 10 percent of GDP. 

“We have shown that we can take those existing diesel engines and convert them into cleaner engines that burn hydrogen fuel,” Kook said. “Being able to retrofit diesel engines that are already out there is much quicker than waiting for the development of completely new fuel cell systems that might not be commercially available at a larger scale for at least a decade. With the problem of carbon emissions and climate change, we need some more immediate solutions to deal with the issue of these many diesel engines currently in use.”

In the hybrid solution presented by the Australian researchers, diesel is still used in the engine, but hydrogen fuel is additionally injected directly into the cylinder at just the right moment to resolve harmful nitrogen oxide emissions that have been a major hurdle for commercialization of hydrogen engines. 

Kook explained the advantage of tweaking the combustion process: “If you just put hydrogen into the engine and let it all mix together you will get a lot of nitrogen oxide (NOx) emissions, which is a significant cause of air pollution and acid rain. But […] if you make it stratified – that is, in some areas there is more hydrogen and in others there is less hydrogen – then we can reduce the NOx emissions below that of a purely diesel engine.”

The new system, which also improves efficiency by more than 26 percent compared to conventional diesel engines, could be commercialized within 12 to 24 months, according to the UNSW team. Once it is on the market, equipment could be retrofitted with the hybrid solution within months. At that point, the challenge would be to provide an appropriate infrastructure for hydrogen supply and storage. 

“At mining sites, where hydrogen is piped in, we can convert the existing diesel engines that are used to generate power,” Kook said. “In terms of applications where the hydrogen fuel would need to be stored and moved around, for example in a truck engine that currently runs purely on diesel, then we would also need to implement a hydrogen storage system to be integrated into our injection system.”

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Chris Findlay

I'm a journalist, editor, and translator based in Zurich, Switzerland. I write about technology and future timelines at, where I also help expand the community as Expert Relationship Manager.

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