Hydrogen holds a large place in the collective account of the energy transition, probably rightly so. Pour que ce choix ait un sens, il est indispensable que l’hydrogène soit réellement décarboné, c’est-à-dire qu’il ne soit plus produit à partir de méthane fossile (à moins de capter et stocker le CO2émis dans le cas du vaporeformage mais le CCS n’est pas encore totalement une réalité industrielle).
Hydrogen production without greenhouse gas emissions is mainly done by water electrolysis performed with electricity also produced without greenhouse gas emissions (ENR and nuclear).The temptation to use the temporary and fortuitous excesses of intermittent renewable energies (wind and photovoltaic) leads to an underloading of electrolysers and therefore to a increase in costs...Even by anticipating the reduction in the costs of electrolysers, industrialists who wish to produce "green" hydrogen at a competitive price seek to operate their electrolysis as long as possible, that is to say with a high charging rate.
Le rapport «Rôle de l’hydrogène dans une économie décarbonée» de l’Académie des technologies(1)indique, qu’à l’optimum, le coût de l’hydrogène «décarboné» est ainsi dû pour 25% à l’amortissement de l’électrolyseur et pour 75% au coût de l’électricité.Consequently, it is necessary to produce hydrogen massively where the decarbonized electricity is abundant and inexpensive.
Where to find electricity produced without emissions of greenhouse gases, abundant and inexpensive?
The most often cited energy resource is solar energy: the cost of solar panels has dropped a lot, and large solar parks exist (Atacama desert, Saharan area).The load factors of these installations can reach values of more than 30%, however the maintenance charges are far from negligible (sand wind).The thermodynamic solar power plants producing electricity do not seem competitive despite their higher load coefficient.
Wind turbines is a resource that is interesting in certain particularly favorable sites, that is to say where the speed of the wind is high and regular.The increase in the dimension of wind turbines, significant progress in the design of blades, rotating machines and electronics have increased the load coefficients.In Morocco, the load factor reaches 45% in the trade winds in the south (Tarfaya) and northern (Gibraltar), that is to say as much as the offshore wind of the Shetlands and at a lower cost.In China, in Mongolia, there are sites where the wind blows 5,000 to 6,000 hours per year (more than 60% load rate).The cost of MWH production can be around 15 to 20 €.
There are possibilities in Europe, mainly in areas rich in offshore wind that ensures a load rate of almost 50%, possibly in combination with nuclear electricity to ensure a satisfactory load rate, or in the south of the'Europe in particular in Spain with photovoltaic solar energy (associated with pumping turbration stations or thermodynamics with heat storage at 400 ° C or with wind production of the Gibraltar Strait in order to reach rates ofhigh load).In all these cases, the cost of the MWH is much higher than 15 to 20 €/MWh mentioned above.
A major project in the Congo allowed by hydroelectricity
Among renewable energies, we often forget the great hydroelectricity.However there are rivers in the world whose flow is very regular.This is the case of the Congo River, the watershed of which is immense, in two hemispheres and subject to various climates which distribute the rains on the watershed and the flows of the tributaries, by an abundance of abundance. La République du Congo a accepté la proposition d’un grand groupe minier australien, Fortescue Futures Industries(2), d’installer sur le fleuve Congo un ensemble de centrales hydroélectriques, une usine de production d’hydrogène et une usine de fabrication et de liquéfaction d’ammoniac (NH3) pour en permettre le transport.It is indeed the liquefied ammonia which can solve the problem of planetary transport of hydrogen.
The project plans to install an electrical power of 40 GW, that is to say 1.7 times the installed power of the famous three gorges barrage in China on the Yang Tse Kiang.The total investment envisaged is 85 billion dollars, of which about half to produce hydroelectricity and the other half for the production of "green" hydrogen, its transformation in ammonia and the construction of the loading port.
The updated cost of electricity would be around 11 €/MWh, with a load coefficient of almost 100% modular ...
Studies on this site began in the 1960s but find a new industrial meaning today in this strong project.The preliminary studies of this hydroelectric development are entrusted to two French engineering companies in Grand Renom (Tractebel Coyne and Bellier and Artelia) in this area.They are confidential.The updated cost of electricity would be around € 11/MWh, with a load coefficient of almost 100% modular according to the industrial needs of the production system.
Une des tâches les plus difficiles est de «couper» le fleuve Congo dont le débit varie de 30000 m3/s à plus de 50000 m3/s (rappelons que le débit moyen du Rhône est de 1 820 m3/s et celui de la Seine de 500 m3/s).The other challenge is to make these works quickly.The objective is to have carried out and put into service a capacity of 500 MW after only 4 years, thanks to a dam and a hydroelectric factory which practically no environmental impact (because this first factory does not generate creationa restraint lake).During this first phase, the construction of the entire industrial chain will be carried out (including electrolysers for the production of green hydrogen, the production of green ammonia and its liquefaction, transport facilities and port facilities).In parallel, the construction of the hydroelectric factories of the "Grand Inga" will be able to begin while the social and environmental impacts of the restraint will be deepened and the necessary compensatory measures will have been determined.
The dam and hydroelectric factories are approximately 150 kilometers from the coast and the planned port area.The electricity produced by several hydroelectric factories located near the dam will be transported by very high voltage lines to the electrolysis which will produce green hydrogen and which will be placed a few tens of kilometers from the hydroelectric factories.Green hydrogen will be transported by gas pipeline in high pressure gasel form, up to the ammonia manufacturing and liquefaction plant.Liquid ammonia will be loaded in a port to be built on specialized ships and already largely functional for any destination on the planet.
Quelle utilisation du NH3ainsi produit?
Maritime transport of hydrogen is in practice very difficult, in any form whatsoever: gaseous, it must be compressed in steel tanks or you must spend a lot of energy to liquefy it at - 250 ° C and thekeep in this liquid state for several days.
The transformation of hydrogen into ammonia seems a promising route with two remarkable outlets:
Currently, ammonia is produced from fossil methane (to make hydrogen) and air nitrogen.Its manufacturing therefore emits greenhouse gases.The production of ammonia from hydrogen decarbon therefore makes it possible to decarbonize the ammonia industry. Néanmoins, il convient aussi de produire par ailleurs de l’azote par distillation fractionnée de l’air avec une énergie décarbonée et de fabriquer le NH3avec un bilan en énergie et un bilan économique acceptables(4).
The ammonia is easily liquefiable and transportable in liquid form (at a temperature of - 33.4 ° C under atmospheric pressure).However, it is a molecule that is not easy to use industrially because of its toxic and corrosive characteristics.The choice of the use of ammonia must still be the subject of technical studies.
The project developed by strong finds its meaning in this global approach to decarbonation of energy by relying on the most effective green energy there is: hydroelectricity.There are other hydroelectric sites in the world which offer massive green hydrogen production possibilities at very competitive prices.
The history of aluminum educates us: aluminum is also made by electrolysis (alumina). Depuis longtemps, les aluminiers ont utilisé abondamment l’hydroélectricité pour disposer d’électricité à très bas coût avec un taux de charge très élevé pour faire fonctionner les électrolyseurs en permanence(5).
This possibility of transport allows the production of green hydrogen at a minimum cost, then to make it a vector of green energy in the form of liquid ammonia.It is possible to use ammonia directly or to iron ammonia to hydrogen by cracking of ammonia with a significant thermal supply which can be improved by improvement of catalysts. Ainsi, l’hydrogène vert et l’ammoniac vert peuvent devenir des vecteurs d’énergie soumis aux lois du marché(6), disponibles en tout point de la planète comme le pétrole et le gaz.This possibility of global market would be good news to ensure the energy sovereignty of each country by allowing it energy imports on a fairly large market to avoid as much as possible the excess of power of certain producers.
