Hydrogen will gradually find its place in the energy mix. This is the wager that our governments in Europe are making with billions of euros of investment. For the moment, it rather sounds like a wishful thinking: one day hydrogen will be a "clean, safe and affordable" energy carrier. It has yet to find the least costly production and distribution method, and in what kind of use it can profitably replace other forms of energy.
Billions on the table
The star of the summer of 2020 on the energy scene is unquestionably hydrogen. In June, Germany announced that out of the 130 billion euros of its post-Covid stimulus package, 9 billion euros would be dedicated to investments in hydrogen technologies, with the aim of becoming the world leader in this sector. The 2018 French plan and its 100 million euros per year pales in comparison. Many voices have been raised calling on the French government to follow Germany's example, or even for the two countries to form an alliance in this sector.
In July, it was time for the European Commission to make its strategy known. Consistently with its policy to prioritize carbon-free energy sources, the Commission plans to improve the share of hydrogen produced from renewable sources. Starting with 1GW of electrolysers already installed in the European Union, but mainly powered by carbon sources (coal or natural gas), the aim is to increase the fleet to at least 6 Gigawatts of electrolysers using renewable energies by 2024 to produce 1 million tons of "renewable hydrogen", then between 2024 and 2030, produce 10 million tons thanks to the installation of 40 Gigawatts of capacity. To support its plan, which will require hundreds of billions of euros in funding, the Commission is launching the European Alliance for Clean Hydrogen, which should bring together private and public, national and local players to coordinate investment in this new sector: what timetable, what technology, what size for electrolysers?
On September 3, 2020, hydrogen enters the recovery plan presented by the French Prime Minister, which provides for an envelope of two billion euros for investments over the next two years, 7 billion by 2030. In addition to this supply policy, demand is supported by guaranteed repurchase prices similar to those enjoyed by electrons from wind and solar energy, a mechanism that has proven to be costly but effective both for developing a wind turbine and photovoltaic panel production park and for reducing the cost of these energy sources.
These programs have several objectives: (i) decarbonize production for industries that cannot do without hydrogen (oil refining, fertilizer production), (ii) extend the uses to transportation, building construction, electricity production and, in steel mills, as a complement or replacement for natural gas, and (iii) develop world leadership in hydrogen-related technologies. But won't all these billions fall into a new Danaïdes' barrel?
A bit of technique
Hydrogen is the first element at the top left on Mendeleev's table, you can't miss it. It is the most important element in the universe, in mass and number of atoms. On Earth, it is mostly present in the state of water, steam or ice after combination with oxygen, hence the name " maker of water " given by Lavoisier. To recover it, the most immediate solution should therefore be the separation of oxygen and hydrogen gas by electrolysis of water. But, for the moment, more than 90% of industrial hydrogen is produced by chemical extraction of fossil hydrocarbons, thus emitting greenhouse gases. As far as electrolysis is concerned, its environmental cleanliness depends on the energy used. Fossil fuels are therefore to be proscribed. Once produced, hydrogen can be transported in gaseous (compressed) or liquid form (at -252°C) and be transformed into electricity or methane for a wide range of uses. However, it has the disadvantage of corroding alloys, which can lead to catastrophic failures and therefore represents a brake on its production, transport, storage and use.
To make a long story short, hydrogen does not (almost) exist in its natural state, so it requires energy to produce it, it is very bulky in its gaseous state and has very little energy power, so it has to be compressed or even liquefied, then distributed and retransformed into usable energy. With the technologies available today, the efficiency of double conversion from electricity to hydrogen and back to electricity is very low: it takes almost 5kWh injected to recover 1.
On the cost side
For the moment renewable hydrogen (2.5-5.5 €/kg) is not competitive with hydrogen produced using fossil resources (about 1.5 €/kg, excluding the cost of CO2). Even if we add carbon capture and sequestration, the latter comes to about 2 €/kg. The bet for the development of a clean hydrogen industry is based on the drop in the cost of electrolysers. They have already fallen by 60% over the last ten years, and the European Commission expects them to be halved by 2030 thanks to economies of scale.
The advantage of hydrogen over electricity is that it can be put into tanks or even injected into networks. So, we can move it over time (storage) for difficult times, transport it to places where there is a shortage of energy, and use it to run the engines of all vehicles. Let's look at these different uses.
Storage: To make the dual conversion of electricity/hydrogen profitable, large price differences are needed, enough to ensure that the difference between high price sales and low-price purchases covers installation and maintenance costs. On a daily cycle, it can be profitable to meet the start and end of day peaks if they are high. But where hydrogen can make a difference with batteries is for longer-term, weekly, monthly or seasonal storage. It is part of the solutions to get rid of fossil fuels in a 100% renewable electricity mix.
Energy transport: The most heavily ventilated or sunny places are not necessarily the most populated. Hydrogen and hydrogen-based fuels would make it possible to transport renewable energy over thousands of kilometers between production locations (with low demand, therefore low prices) and consumption locations (with low production, therefore high prices), for example in Australia, Latin America, or between North Africa and Europe. But here again, the cost of the infrastructure to be installed and maintained, transmission losses and double conversion losses are still higher than those of high-voltage line construction.
Fuel: The hydrogen engine is either an internal combustion engine using hydrogen as fuel or an electric motor connected to a fuel cell. In both cases, by combining hydrogen with oxygen from the air, energy and water are produced. The cleanliness of this conversion makes it the ideal solution for urban transportation, assuming the hydrogen was produced from clean sources. Compared to "all-battery" electric vehicles, the big advantage of those equipped with a hydrogen engine is the speed of recharging, assuming there is a dense network of stations. The disadvantage, which is not negligible, is the volume and weight of the tank, which is much greater than that of gasoline and diesel fuel tanks.
Electrolysers are one thing, their feeding by green electricity is another. The plans mentioned seem to overlook the investments in wind turbines and photovoltaic panels needed to separate hydrogen and oxygen, in storage and distribution means, and then in conversion equipment at stationary or mobile consumption points. In France, the supply of energy to electrolysers by nuclear power plants is a solution which, although certainly not 'green', is decarbonated. But in the long term, the multiplication of low power decentralized renewable production units will create tensions for the occupation of space, both on land and offshore.
After supporting renewable energies and electric cars, Germany and France are betting on hydrogen to reconcile economic decarbonization and technical progress. This is a costly and risky gamble. One of the gains would be technological leadership on an essential resource in the energy mix, provided that guaranteed purchase prices do not encourage the development of a low-cost sector outside Europe, as was the case for photovoltaic panels in China. But the climate emergency also requires emerging countries to rapidly move away from fossil fuels, and therefore a wide dissemination of decarbonated technologies.
 Agence internationale de l'énergie, ‘’The Future of Hydrogen. Seizing today’s opportunities”, June 2019.
 See J.O.M. Bockris: « The hydrogen economy: Its history», International Journal of Hydrogen Energy (2013), 38, p. 2579-2588.