The threat posed by climate change and the striving for security of energy supply are issues high on the
political agenda these days. Governments are putting strategic plans in motion to decrease primary
energy use, take carbon out of fuels and facilitate modal shifts.
Taking a prominent place in these strategic plans is hydrogen as a future energy carrier. A number of
manufacturers are now leasing demonstration vehicles to consumers using hydrogen-fueled internal
combustion engines (H2ICEs) as well as fuel cell vehicles. Developing countries in particular are pushing
for H2ICEs (powering two- and three-wheelers as well as passenger cars and buses) to decrease local
pollution at an affordable cost.
This article offers a comprehensive overview of H2ICEs. Topics that are discussed include fundamentals
of the combustion of hydrogen, details on the different mixture formation strategies and their emissions
characteristics, measures to convert existing vehicles, dedicated hydrogen engine features, a state of the
art on increasing power output and efficiency while controlling emissions and modeling.