Is there hydrogen in space

Car fuels (5): H2 - hopelessly in the back

“Keep it simple” is a tried and tested principle for engineers and technicians. So if Power-to-X (PtX) - as we saw in the last chapter on car fuels (4) - is not a solution for a traffic turnaround for various reasons, why not try it with a fuel that every middle school pupil at the latest knows from the oxyhydrogen experiments in chemistry class: hydrogen (H2). Discovered in 1766 by the English naturalist Henry Cavendish, this lightest and most abundant of all elements in space does not occur in elemental form, but in compounds, the most common of which is water. Water can be split up using renewable electricity (electrolysis), among other things, to produce hydrogen, which, if necessary, can be burned with the oxygen in the air to form water. In principle, electrolysis is also a power-to-gas technology, but is usually not referred to as this because it is considerably older than the PtG term and because, unlike other PtG technologies, it does not involve any further chemical conversion of the Hydrogen sets.

That brings us to the advantages and disadvantages of hydrogen as a fuel:

Hydrogen benefits

  • 1. Hydrogen is not a greenhouse gas; if oxyhydrogen gas explosions do not occur when it is released, this is completely unproblematic, since the released gas disappears into space.
  • 2. Environmental problems with the "exhaust gases" are not to be feared either, since the H2 cars only emit water vapor.
  • 3. Hydrogen technology (electrolysis, storage) has been known and proven for a long time.
  • 4. In contrast to PtX technologies, no further chemical conversion is required to use hydrogen, which of course saves energy.
  • 5. Hydrogen can be used well in fuel cells (BSZ) - this is considerably more energy-efficient than conventional combustion engines; Even at BMW, hydrogen burners are now a thing of the past [1].
  • 6. Hydrogen can be filled quickly and easily into the special tanks of H2 cars at special filling stations; the full tank of e.g. a Hyundai Nexo is sufficient for around 540 km [2].
  • 7. With the Toyota Mirai and the SUV Hyundai Nexo, there are currently two tried and tested series-production cars on the market; an H2 SUV from Mercedes, and only for leasing, is to follow.
  • 8. It is economically advantageous that here - as with agrofuels and PtX - the conventional filling station network is retained; therefore, in addition to gas specialists such as Linde and electrolyser manufacturers such as Siemens, classic mineral oil companies [3] are particularly interested in this technology.
  • 9. It is also economically important that the competence for H2 fuel cell vehicles lies with the old auto “great powers” ​​Japan and Germany, which have passed their zenith: in Japan it is Toyota and Honda, whose Honda Clarity Fuel Cell has been on the market for years in the home country and the USA, but is not available in Germany. In Germany, BMW and Mercedes in particular have developed the relevant technologies in cooperation with the National Organization for Hydrogen and Fuel Cell Technology (NOW) and the National Innovation Program for Hydrogen and Fuel Cell Technology (NIP) [4].

With so many advantages, the H2 / BSZ technology should actually be a sure-fire success for the traffic turnaround. But for decades, the market breakthrough for this technology has always been imminent.

Hydrogen disadvantages
The lack of circulation of H2 / BSZ cars is not due to a lack of public funding, but to the considerable disadvantages of the hydrogen path:

  • 1. Complicated hydrogen: H2, the smallest and lightest of all elements, is a complicated gas. It diffuses through normal tank covers and embrittles metals. Therefore, special tanks are needed in which it is stored either in gaseous form under high pressure (today 700 bar) or in liquid form at extremely low temperatures (-253 ° C), the latter only being possible with a great deal of technical and energetic effort. Storage forms such as metal hydrides are only suitable for ships (submarines) because of their weight. LOHCs, liquid organic hydrogen carriers, are still being tested; Some of the carrier materials are themselves complicated and, because of their large volume, are only suitable for larger vehicles.
  • 2. What consequences a global hydrogen economy, in which larger amounts of H2 escape into space ("slip"), would have for the earth's water resources in the long term has not yet been investigated.
  • 3. High water consumption: In any case, large amounts of water are required to produce H2 when the global energy system or even just the transport system is converted. These are by no means freely available everywhere around the world, and will become even scarcer in view of the growing world population and increasing global warming.
  • 4. Low efficiency: the overall efficiency of the hydrogen path is just 26%! This well-to-wheel approach (e.g. from the shaft of a wind turbine to the rotating vehicle wheel) only applies to fuel cell vehicles; in H2 combustion engine vehicles it is halved again. That may still be a lot compared to the PtX paths and the conventional fossil path; This is little compared to an overall efficiency of around 70% for electric vehicles. The low level of efficiency would mean that a considerably larger number of renewable energy generation units (solar, wind, water) would have to be set up than is already foreseeable today for the goal of 100% renewable energies.
  • 5. Expensive renewable hydrogen: Today, 50 million tonnes of H2 are still being produced from natural gas at low cost with unsustainable "steam reforming", e.g. for use in the chemical and metal industries. Compared to cheap “fossil” hydrogen, renewable hydrogen is relatively expensive, although the price in Germany is still capped by the joint venture H2 Mobility [5] at € 9.50 per kilogram (sufficient for approx. 90 to 100 km). Even if it is possible in the future to significantly increase the efficiency of the corresponding steps in the H2 path, this will hardly lead to lower prices due to the replacement of large quantities of fossil hydrogen, which is necessary for climate policy. In addition, there is the demand competition from the heating sector.
  • 6. Expensive filling stations - thin network: The cost of setting up a hydrogen filling station is around 1 million euros. If the hydrogen is to be generated from water using electricity directly at the filling station, an electrolyser is necessary, and the costs can easily rise to well over 2 million euros. This is one of the reasons why there are only around 80 such filling stations in Germany.
  • 7. Expensive cars - few models available: It is not only the element hydrogen, which is difficult to handle, that makes H2 cars expensive, but also their additional electrical installation. Because H2 cars are e-cars that need a battery, albeit a small one compared to thoroughbred e-cars, to be able to recuperate. And so a Hyundai Nexo costs around € 69,000, a Toyota Mirai even around € 79,000. At such prices, the range of models is of course small and will remain so.

Hydrogen is an interesting storage medium if there is enough excess electricity and water. Otherwise, the conversion losses are a significant drag on this technology. Beyond the pure storage segment, the technology may occupy some niches in the transport segment - e.g. in rail transport, where the routes are the same every day and the hydrogen can be generated directly in the depot, or in the future long-distance heavy goods vehicle transport that will still be available in the future. But hydrogen is unsuitable for a traffic turnaround in the area: too complicated, too ineffective, too expensive. Although there are always attempts by interested industrial and business circles to implement this technology after all [6], there will be no all-encompassing turnaround in traffic towards hydrogen.

If you don't want to believe it, compare a Tesla Model 3 with a Toyota Mirai [7], and then explain why you should spend € 20,000 more on the H2 Toyota. And in terms of economic costs, electromobility has long been “ahead” [8].

Götz Warnke

[7], fuel-cell-car-toyota-mirai /

The complete series
Fossil Fuels for fossil Brains (1): The combustion engine in its age
Fossil Fuels for Fossil Brains (2): Society, Fashions and the SUV
Car fuels (3): Biofuels - gasoline is in bloom with bio
Auto fuels (4): Power-to-X– presenting problems
Car fuels (5): H2 - hopelessly in the back
Alternative fuels (6): Renewable energies need emobility
Auto fuels (7): The fairy tale of the enemies of e-mobility