Like electricity, hydrogen is primarily an energy vector produced from another resource. For economic reasons, 95% of it currently comes from natural gas. Some natural sources of hydrogen have nevertheless been observed.
With the increase in the proportion of electricity produced from low-carbon energies - particularly renewable - researchers are currently studying the option of producing hydrogen via the electrolysis of water, for use as part of the energy transition. Mainly used until now in the chemicals and refining sectors, hydrogen may find other applications, such as for electricity storage or as a fuel in the transport sector.
- Hydrogen sources
- Hydrogen production methods
- The current use of hydrogen
- Hydrogen in the energy transition
The main sources exploited for di-hydrogen H2 production are water and hydrocarbons (coal, oil and gas).
A single water molecule is made up of 1 atom of oxygen and 2 atoms of hydrogen, as reflected in the formula H2O.
Hydrogen is also found in hydrocarbons, which are produced by a combination of carbon and hydrogen atoms. Such is the case, for example, with methane, or natural gas (CH4), one of the simplest combinations for hydrocarbons.
The di-hydrogen molecule is made up of two hydrogen atoms and is particularly energy-rich: the combustion of 1 kg of hydrogen releases roughly three times more energy than 1 kg of gasoline does, only producing water in the process. Conversely, on an equal mass basis, hydrogen occupies a bigger volume than any other gas. Thus, in order to produce as much energy as 1 liter of gasoline, it takes 4.6 liters of compressed hydrogen at 700 bars (700 times atmospheric pressure).
Hydrogen is extremely light, a characteristic that is a drawback for its storage and transport. Generally speaking, bottles or pipelines are used to transport it in compressed form. The liquid form (at a temperature of - 253°C) is far more expensive.
Hydrogen also exists in the natural state. The first natural sources of hydrogen were discovered on the seabed in the 1970s, with further land-based discoveries made more recently. But there is still a long way to go before the viable use of hydrogen in this state can be envisaged. Further progress is required in terms of knowledge concerning the origins of the formation of this hydrogen, along with research on profitable production techniques.
Located deep underwater and a long way from coasts, extracting hydrogen from beneath the ocean bed is uneconomical. More recently, land-based hydrogen seeps, which are easier to access, have been identified in two types of geological environments:
- Terrestrial mountain ranges containing peridotites, where specific tectonics expose the rocks to alteration by meteoric water;
- Intracontinental regions (intraplate regions), and, in particular, in the oldest parts (Precambrian cratons) located at their center.
Peridotite : rrock derived from the Earth's mantle, consisting mostly of olivine (up to 90%) and pyroxenes (ferromagnesian minerals). These minerals contain reduced iron, which oxidizes upon contact with water to produce hydrogen. Peridotites are exposed in some places on the surface of the deep sea floor. Surface outcrops have also been found in particular tectonic environments.
Intraplate region: area located in the interior of a tectonic plate as opposed to an area at a plate boundary. Here, interactions with the Earth's depths are more limited than those at the plates' boundaries. These areas contain the oldest parts of the continents, cratons.
Production involves extracting di-hydrogen H2 from the primary resource.
Different production methods exist:
- Steam natural gas reforming is the most widely employed technique. It consists in causing methane to react with water to obtain a mixture of hydrogen and CO2. The CO2 emitted by this process may potentially be captured and stored to produce low-carbon hydrogen. Instead of natural gas, the use of biomethane (methane produced via biomass fermentation) is another solution for producing low-carbon hydrogen.
- Gasification involves using combustion to produce a mixture of CO and H2 from coal (a solution that emits high levels of CO2) or biomass.
- Hydrogen can also be produced from water and electricity via the electrolysis of water. The electrolyzer separates water into hydrogen and oxygen. At present, the method is not widely employed since it costs significantly more (2 to 3 times more expensive than natural gas reforming). It is reserved for specific uses that require a high degree of purity, such as electronics.
«Today, 95% of hydrogen is produced from hydrocarbons (oil, natural gas and coal), the most profitable solution. However, this process emits CO2, a greenhouse gas. Industrial players are increasingly examining the possibility of producing hydrogen via electrolysis using low-carbon energies. But the obstacle remains the associated production costs, which are considerably higher than those of reforming.»
Guy Maisonnier, economic engineer, IFPEN
There are currently two principal uses of hydrogen:
- It is a base material for the production of ammonia (fertilizer) and methanol.
- It is also used for the refining of oil products, fuels and biofuels.
In 2018, global hydrogen consumption was estimated to be around 74 million tonnes (Mt).
In 2017, in France, hydrogen consumption amounted to 1 Mt.
By way of comparison, global energy consumption in 2017 was around 13,800 million tonnes of oil equivalent (Mtoe) (all energy is stated in terms of the energy capacity of a tonne of oil); hydrogen therefore represents 0.4% of this quantity in terms of mass, but 1.2% in terms of energy (1 tonne of Hydrogen equates to 2.86 toe in heat equivalent).
This hydrogen is transported via a relatively extensive network of pipelines; a total of more than 4,500 km in the world, including 1,600 km in Europe and 2,500 km in the USA.
Hydrogen and the challenges of the energy transition
Hydrogen may provide the solution to two major challenges in the energy transition
- The need to reduce the carbon footprint of the transport sector. Electric vehicles equipped with a fuel cell (FC) convert hydrogen into electricity and steam, an environmentally-friendly solution if the hydrogen is produced from low-carbon sources. Hydrogen has advantages over batteries, in terms of both range (500 to 700 km) and recharging times (< 5 min).
- The possibility of storing hydrogen, in order to overcome the problem of the intermittent nature of some renewable energies.
- Hydrogen is produced via the electrolysis of water using surplus electricity production, primarily wind and photovoltaic,
- The hydrogen produced can be stored and then converted back into electricity,
- Current storage options are primarily hinged around salt caverns. Storage is primarily being considered in salt caverns.
These two challenges are inextricably linked with:
- The possibility of producing low-carbon hydrogen or green hydrogen:
- Hydrogen production does not emit CO2 when electrolysis is used, if the electricity itself is low-carbon, i.e., produced from renewable or nuclear energies.
- When produced via natural gas reforming, the resulting CO2 emitted must be captured and stored underground over the long term to obtain low-carbon hydrogen.
- The increase in the production of low-carbon electricity, particularly from renewable energies to address the needs of electrolysis-based hydrogen production.
The production of green hydrogen is not yet a reality. A transformation of energy systems as well as the technical / economic context will be required to bring it about.
The use of low-carbon hydrogen
Generally speaking, 4 options for the use of low-carbon hydrogen can be identified:
- Power to Industry : direct sale to green hydrogen-consuming industries (refining, chemicals) in order to reduce the carbon footprint of their industrial processes.
- Power to Gas : use in the gas sector in two forms:
- via direct injection into gas networks for combustion,
- via the production of synthetic methane (using the methanation principle: conversion of carbon monoxide (CO) or carbon dioxide (CO2) in the presence of hydrogen), which can then be converted in heat, electricity or fuel.
- Power to Power : electricity production using fuel cells.
- Power to mobility – efuel : conversion of hydrogen into another fuel via the Fischer Tropsch process. The principle here is to produce another molecule from H2 and CO2 in order to obtain a fuel that can be used in existing engines.
Conditions required for the roll-out of low-carbon hydrogen
The large-scale roll-out of hydrogen is unlikely before 2030. The challenges are multiple:
- The cost of producing hydrogen via electrolysis is currently 2 to 3 times higher than the cost associated with natural gas reforming. A significant reduction in costs throughout the chain, be it in terms of electrolyzers or fuel cell vehicles, is therefore required.
- In parallel, a relatively high cost of CO2 would make it possible to reduce the cost difference with natural gas reforming. However, the increase in carbon tax should be progressive and go hand-in-hand with public policies to support the least well-off populations.
- Access to competitive, low-cost electricity is necessary to reduce the cost of production via electrolysis. This condition requires further reductions in the cost of solar or wind power.
- In some instances, the different conversions imply efficiency cascades generating energy losses, thereby increasing production costs.
- Some conversion processes (methanation, Fischer Tropsch) require access to CO2, which incurs an additional cost and entails the need to develop CO2 capture technologies.
- Hydrogen systems require the roll-out of a new framework in the electric sector incorporating renewable energies, associated networks and adapted management modes (smart grid).
- The roll-out of transport and distribution infrastructures requires considerable investments and a relatively long implementation period.
A national plan for hydrogen in France
The French law relating to the energy transition for green growth set an objective of 32% renewable energies in final energy consumption and 40% renewable energies in electricity production by 2030. The law also stipulates a 30% reduction in fossil energy consumption by 2030 and that the gas sector should be decarbonized by 10% by the same year. Hydrogen represents a lever of interest in order to achieve these objectives.
On 1 June 2018, the French government thus launched a Hydrogen plan aimed at supporting its deployment within the context of the energy transition. The objective as set out in the plan is that 10% of hydrogen production should be from renewable sources by 2023. The “Long-term energy research program” (PPE) draft legislation published in January 2019 also sets this objective. In 2019, €100 million will be dedicated to the development of production and transport technologies across the country.