A diesel engine that has been modified to burn hydrogen fuel is undergoing tests in a truck carrying cargo to and from a major Japanese airport, and travelling around tourist hotspots such as Tokyo Disneyland.

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The internal combustion engine (ICE) on the small commercial truck has been modified by Japanese firm iLabo as part of an on-going trial of modified diesel-to-hydrogen engines, supported by the country’s government.

This latest three-month trial has increased the cargo load on the truck and introduced it to Tokyo roads, where it will be refuelled at some of the city’s 23 H2 filling stations — most of which dispense either grey hydrogen made with unabated fossil gas, or by-product H2 from the production of chlorine and caustic soda (chlor-alkali process).

“We have made modifications such as adding spark plugs, changing piston shapes, and replacing components of the fuel gauge,” iLabo chief executive Ohta Nobuhiro tells Hydrogen Insight.

The piston shape has been changed to suit the characteristics of hydrogen as it burns.

The three-month trial will see the small commercial truck travel the 50km route between Haneda airport and a hotel in Chiba, in order to evaluate engine performance.

“We chose the route between Haneda Airport and hotels around Tokyo Disneyland [which are on the route to Chiba] for testing because it encompasses main roads, local streets, and highways, covering all the types of roads used in commercial vehicle operations,” said Nobuhiro. “We believe this route was optimal for investigating fuel efficiency and performance.”

iLabo claims that the engine’s fuel efficiency almost the same as that of the diesel equivalent.

According to consultancy McKinsey, hydrogen ICE vehicles operate at around 50% tank-to-wheel efficiencies, higher than diesel (which has efficiencies of below 40%) at any load, and even out-performing hydrogen fuel cells once the powertrain is operating at more than 50% of maximum output.

Hydrogen ICE vehicles also have other advantages comparies to fuel cell-based powertrains, iLabo believes, as they are resistant to dust and salt.

However, at all powertrain outputs, hydrogen ICE engines fall behind battery-electric equivalents, which operate at tank-to-wheel efficiencies of over 90%, according to McKinsey’s analysis.

Nevertheless road freight operators, especially those operating heavy trucks, are reportedly keen to minimise the capex outlay of converting to battery-electric or fuel cells right away, and so are considering H2 ICE vehicles as a stop-gap solution.

Interest in the technology has prompted Cummins and Tata to pledge investments of $425m to build a new hydrogen engine factory in India.