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Adrian Lloyd; Gwen Boswell

The UK Government’s most recent hydrogen strategy (2021) outlines a key ambition: to increase low carbon hydrogen production capacity to 5GW by 2030 [1]. The UK plans to meet this ambition with a rapid ramp up of production and use of hydrogen over the coming decade. The UK transport sector contributes the most to domestic GHG emissions, and so a focus on zero-emission transport technologies using hydrogen is expected to grow.

There are four true zero carbon tailpipe emissions technologies used to power vehicles: battery electric vehicles (BEVs), hydrogen fuel-cell electric vehicles (FCEVs), hydrogen internal combustion engines (H2-ICEs) and green ammonia internal combustion engines[2]. For many years, H2-ICEs were disregarded due to the high costs of hydrogen. However, as government heads turn to hydrogen, H2-ICEs are being reconsidered as a zero-carbon solution, with automotive OEM’s, component suppliers and start-ups reconsidering it as a viable powertrain component.

The first internal combustion engine didn’t burn polluting evils like gasoline or diesel. In fact, when Francois Isaac de Rivaz designed the first combustion engine in 1806, it ran on a hydrogen-oxygen mixture. Of course, at the time ‘net-zero’ was far from popular discourse, and so gasoline and diesel were the favourable competitors. Today, as government heads turn to hydrogen, automotive OEM’s, component suppliers and start-ups are going back to the roots of this technology and are reconsidering hydrogen as a viable powertrain component.

H2-ICEs work in the same manner as traditional internal combustion engines, except hydrogen replaces fossil fuels. The process involves burning hydrogen in a modified spark-ignition engine to release energy, which works as follows[3]:

A company reconsidering these H2-ICE technologies is construction equipment giant JCB. In May 2021, JCB announced a hydrogen-fuelled piston engine capable of powering heavy machinery and vehicles without emitting CO2[4]. Using the early ideas of Rivaz, JCB have reclaimed a zero tailpipe-emission technology that delivers green transport at about a tenth of the cost of other zero tailpipe-emission drivetrain solutions.

While JCB’s innovation success is to be celebrated, hydrogen spark ignitions engines are not without their issues. One is a phenomenon called pre-ignition, where the fuel/air mix ignites before the piston has reached the top of the compression cycle and the spark plug fires. Another is the generation of Nitrous Oxides (NOx) when the fuel/air mix is set to achieve optimum power. Reducing these risks means adopting a lean fuel/air mix, which reduces the engine power output engine. Therefore, a larger engine (and further modifications such as the use of turbo-chargers) are needed to get the same power as an equivalent internal combustion engine. While this can drive up costs, the weight penalty of this is likely to be significantly less than the weight penalty of a battery powered vehicle and lower than the cost of fuel cells.

With hydrogen expected to play a key role in decarbonising transport, advancements in these zero-emission alternatives are expected. At Meld, we find these developments of great interest as they show an emerging demand for hydrogen production which could be localised, especially around specific use categories such as construction and agriculture. Moving forward, Meld understands that while fuel cells and turbines will be important components of future technologies, direct use of hydrogen in combustion engines could play a key role in the UK’s ongoing search for more affordable, zero-carbon technologies.