tisdag 5 mars 2019

Hydrogen train hype

Hydrogen powered trains are in the news at the moment. They are being promoted as a means of making railways less dependent on carbon as a fuel. The idea is that the unwanted electricity from wind generation can be electrolysed and used as fuel in fuel cells. The system is being trialled in Germany on a new train, the i-Lint, and in the UK on a converted class 321 multiple unit train dating from the late 1980s.

There are at least four snags.
  • The hydrogen has to be compressed and stored in heavy tanks.
  • Overall energy efficiency is about 27%.
  • Fuel cells have a limited life.
  • Cost.
I have attempted to obtain figures for the power output of these devices but a search reveals nothing on the subject, not even on the website of the manufacturer, Alstom. My guess is that it is around 1000 hp, about the same as diesels such as British Railway class 20, or a class 4 steam locomotive such as the 80xxx class 2‑6‑4 tank class. The latter, burning light oil and with draughting modifications to suit, turn in a thermal efficiency of around 12%. Because steam locomotives have a small number of large parts, they are relatively inexpensive to manufacture using modern CADCAM and 3D printing techniques; given a sensible production run, the cost of a locomotive in the equivalent power category should be of the order of £1 million. Given that the capital cost of rolling stock accounts for about a quarter of the cost of running a railway, when will someone drop their prejudices and have a proper look at this supposedly outdated technology?

As for the unwanted hydrogen, there is a simple solution - feed it into the gas grid. This would have to be in defined areas as combustion requires different air:gas volume ratios than are used for natural gas. The hydrogen can then be used for on-site electricity generation in combined heat and power systems, which results in minimal waste of energy.



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