The general infatuation with hydrogen is the subject of justified criticism that often remains confused by mixing everything up. Michel de Rougemont try to get some clarity.
The question of why
As long as other energy solutions are available, there is no reason to promote this chemical reagent to the rank of mass energy vector.
It is only through the ex nihilo creation of a need for energy transition (“climate policies”, urgent on top of that) combined with electrical ramblings (“fear of nuclear power”) that its interest has surfaced.
Stuttering of the new power sources
Today’s new energy sources are neither renewable (because they have to be rebuilt every 25 years) nor controllable because they are largely intermittent.
This has nothing to do with hydrogen except, possibly, with its production schedule if it were to depend on such primary sources.
Hydrogen is very singular, at the top left of the table of elements, a powerful reducer, above all an industrial chemical reagent.
For its part, CO2 is fully burnt, thoroughly oxidised, with a very negative enthalpy of formation (-393.5 kJ/mole); the same applies to H2O (-285.8 kJ/mole in the liquid state).
Energy experts should stop forgetting this! For ceasing to forget is more important than remembering, it requires another effort, that of open-mindedness.
85% of the world’s energy supply is of a chemical nature, through an oxidation reaction called combustion, the products of which are, in the end, water and carbon dioxide.
The liquid form of carbonous fuels has the advantage of a high energy density which makes it possible to embark them in motor vehicles: cars, trucks, diesel locomotives, planes, ships. According to BP, transport consumed 20.7% of the world’s energy in 2018.
The problem of autonomous mobility is posed by any “energy transition” that aims to eliminate the availability of these oil-based liquids.
Electricity, which cannot be stored, is not in itself the solution to this problem. Another on-board storage method is then needed, for example a reducing metal such as lithium to be recharged in batteries, flywheels to be revived at the end of an itinerary, or air to be compressed without overheating. All this is linked to high energy losses, which are hardly mentioned when the desire for the alternative gets out of proportion.
Solutions to an upside-down problem
Political marketing has discovered hydrogen and doesn’t really know how to position it.
It is necessary to distinguish between its use as an energy carrier or as a synthetic chemical reagent:
- The first must be stored and distributed, which poses quite a few logistical and safety problems before burning it in thermal engines or in expensive fuel cells that power electric motors.
It seems particularly foolish (and therefore “ecological”) to produce hydrogen and then simply burn it.
- The latter can be used to synthesise liquid fuels. One of the proposed reactions is that of reducing CO2 into methane and other hydrocarbons or organic compounds. This requires concentrated CO2, which is not the case with air, where it is diluted to 410 ppm.
Carbonous or non-carbonous production
Whatever its intended use, the first step is to obtain hydrogen, which, contrary to what many officially befuddled people say, has no colour according to its origin.
The first two processes are current and industrial, the others are possible although not realised on a significant enough scale to start thinking about them for industrial application.
- Partial combustion of methane (natural gas) in the presence of water, also called reforming or steam reforming (this is the most important current mode).
By-product of this process: the famous CO2!
- Water electrolysis, slightly salty to conduct electricity but not too salty, and the variant where hydrogen is a by-product of the manufacture of chlorine and caustic soda by brine electrolysis. The stability of the electrodes and membranes remains a challenge.
Energy yields are at best around 80%.
As much oxygen is produced as hydrogen.
- Methane pyrolysis at very high temperature, giving hydrogen and carbon black, a use for which needs to be found in corresponding stoichiometric quantities.
- Thermochemical decomposition of water, supposedly promising from a thermodynamic point of view but with large question marks regarding the construction materials and the service life of the installations at the temperatures considered (1500 – 2000 °C).
- Other ways of decomposing water by salts of cerium, copper, etc., that are regenerated at very high temperature. An area still reserved for the Professors Cuthbert Calculus of this world.
If the hydrogen production must be linked to the vagaries of intermittent electrical production, then the manufacturing process will have to be adapted to it, which is not automatically done by saying it, and a high instantaneous production capacity will be required that is capable of absorbing the peaks of electrical power generation.
Inefficiency: thermodynamic fatality
In any case, the use of hydrogen, whether as a vector or as a reagent, is bound to the thermodynamic fatality that tells that neither the enthalpies of formation of the compounds involved (CO2, H2O, H2, O2, CH4, etc.) nor the heating and cooling cycles play yo-yo without significant energy losses.
In other words: to obtain one unit of useful energy at the wheels of a vehicle it will be necessary to extract much more, perhaps two or three times, from the politically correct primary sources of solar irradiation, wind, rain making streams and rivers, geothermal energy, biomass and fissile materials (not so PC for many fearful people). So, work more to get less.
Whatever the succession of processes, the whole must be safe, a problem that should not be overestimated on the pretext of the inherent dangers of this gas, especially if its use remains at an industrial level as is the case today.
Being able to detonate in a wide concentration range in the air, its distribution to the general public may be dangerous, although the risks associated with high pressures and possible leaks can be made manageable.
“Technically possible” does not mean efficient, or desirable.
Current technology already makes it possible to carry out all these processes, albeit in a very inefficient way, using processes for which it is not known whether the equipment can last for weeks or decades and units that would have to be oversized. Talking about the price of the installations or the production costs is superfluous; they are far too high in any case.
Efficient processes have yet to be developed and the viability of the facilities to be designed has yet to be ensured. The time has not yet come for investments other than R&D in this area.
Excessive dimensions for fearful ecologists
No one can tell whether a “hydrogen industry” can one day provide the solution needed to transform the world’s propulsion systems.
As it is said that Stalin was saying: “quantity has a quality in itself”.
The orders of magnitude involved are difficult to grasp, which highlights an issue with the quality of our intellect, especially that of an ecologist for whom only the well-chosen anecdote counts.
Let’s take a single current figure as an example:
Producing electricity to provide the transport sector with as much energy as it does today but in the form of hydrogen, i.e. 119 EJ (exajoules, 1018 Joules), would require the construction of 3240 modern nuclear power plants of 1600 MW each, or 6.2 million 3 MW wind turbines, or 283,000 km2 of photovoltaic panels in well-placed locations (not in Switzerland, which is only 41,285 km2 ). And more will be needed in the future, as growth will demand it.
If only to produce hydrogen, the world’s nuclear park would have to be 6 times larger than it is today, or 12 times as many wind turbines as there are currently in the world, or 24 times as many solar panels.
In the latter two cases, the electrolysers would have to be oversized by a factor of 4 to 6 to be able to absorb power peaks at midday of a sunny day or when the wind is blowing strongly, even if it means not operating at night and during days of wind calm.
Thus, most of the fixed assets will remain unemployed, as will the operating staff.
The economy, stupid
At last, in spite of the ideological posture of the dominant thinking described in point No. 1, any implementation of a technology associated with hydrogen must be done in an economic way, i.e. more attractive than the other solutions, which are now carbon-based. And, this cannot be stressed enough, without the terms of economic comparison being biased by state intervention, taxation and other dirigisme, which depend only on the versatility or pusillanimity of the ephemeral political classes.
In the current state of the art, the inefficiencies inherent in all the possible stages cast doubt on the competitiveness of these technologies, even decades down the road, although it may evolve faster. It is therefore necessary to stop writing reports full of incomprehensible acronyms and useless calculations, to stop making announcing effects on the subject, and to work according to point 10 above, which will take its time.
The future has beautiful prospects, and vice versa.
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