Comment on transport energy (hydrogen/ammonia)

I think one criticism of the Achieving Net Zero Report that can validly be made is that it assumes that road transport will be electric. The energy density of batteries is too poor for long haul road haulage, and it is most likely that some form of fuel cell or hybrid power solution will emerge. This certainly seems to be the direction of travel, especially on the Continent. However, the storage and safety risks associated with hydrogen probably mean that ammonia (NH3) will be used as a proxy for hydrogen.

At a large scale (e.g. deep sea ships) ammonia  can be burned directly in slightly modified marine diesel engines, though care needs to be taken to minimize NOX pollution. It has a lower energy density than diesel, so ships converted to burn ammonia will have to accept a shorter range, or increase the space and weight devoted to bunker storage,

At a smaller scale, ammonia can be used in place of hydrogen to power fuel cells.

The snag is that current processes for making hydrogen and ammonia use oil, or  more commonly, Natural Gas as feedstock. The most positive approach to this problem that I have seen has been undertaken by Ricardo Energy  (based in Shoreham). They have done a number of studies on behalf of  emerging coastal countries that have access to abundant solar or wind power so that green hydrogen (from which ammonia can be made) can be generated by electrolysis using net carbon solar/wind power, and offered to passing ships, or transported to key ports.

As an aside, about 15 years ago, the emphasis was on reducing pollution from ships. Some were designed to run on LNG, e.g. the cruise ship Iona and a near sister ship. Of course LNG will reduce the carbon footprint compared with diesel, but  it can never approach zero carbon. At the time of writing the fuel bill for the Iona must make someone’s eyes water!

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