Hydrogen: The path towards decarbonisation

Decarbonisation is one of the main market objectives for countries all over the world to face by 2050 so that we can achieve a more sustainable planet and efficient energy. In this way, it can claim to give a solution to problems created by the use of fossil fuels such as the gas emissions that contaminate the atmosphere with SOx, NOx, and CO₂ as well as others, and problems with supply and prices.

The energy situation today has put the necessary manifesto in place to search for alternatives to gas and oil that guarantee greater independence. The full energy transition to hydrogen will be an important pillar for facing the power of decarbonising all areas of the economy so that the roadmap for hydrogen is established.

In this they can identify the necessary priorities and resources, the main challenges in the development of renewable hydrogen and the possible ways for overcoming them will allow the deployment of this type of energy in Spain. This document is aligned with the Annual Strategy of Sustainable Growth of 2021 published by the European Commission and will be allowed to take a position in our country regarding the technology for decarbonising different sectors of the economy.

What is hydrogen?

Hydrogen is the most abundant and simple element to exist in the universe. It has the potential of providing energy to any type of transport, as well as buildings and big factories. Hydrogen is not one of the primary energies but is an energy carrier. It must be produced from a primary energy resource (preferably renewable) and serve to transport and store energy. In the case that it uses electricity coming from renewable sources, we have green hydrogen.

According to data from the International Agency of Energy (IAE), currently, in the world, we are consuming around 70 million tonnes of hydrogen. It is used mainly as a reactive for various processes in the chemistry sector, such as the production of ammonia and hydrocracking and (desulfuration) of fuels. These uses represent 80% of the global demand.

Once produced, the chemical energy of hydrogen can change into different forms of energy through different routes, giving place to the concept of routes of valuation Power-to-X. Hydrogen can change into electricity (power-to-power), transform into methane and/or can inject a natural gas (power-to-gas) serving as a primary substance for the chemical industry (power-to-industry), changing into fuel, for example, methanol (power-to-fuels)- or for mobility (power-to-mobility). Through these different focuses, hydrogen can integrate renewable energies on a large scale and generate energy, acting as a shock absorber for the increase in flexibility of the system and helping to decarbonise all the primary sectors of the economy.

For 2050, the EU has estimated that hydrogen entails a 14% energy mix, once again reaching sufficient maturity and deploying on a large scale, super passing the challenges of technology concerning its cost, production or limited distribution through the existing gas network.

What advantages does hydrogen have?

The use of hydrogen as the way for energy transition offers many advantages because hydrogen is different to other fossil fuels:

• It doesn’t produce CO₂ emissions
• It possesses a high density of energy per unit of mass
• It requires a low activation energy
• Is extremely volatile
• Is not toxic
• Possesses a high inferior limit of inflammability and detonation and a high temperature of spontaneous combustion
• Is very secure in open spaces

Types of hydrogen production:

Today exists three main sources of obtaining hydrogen:

1. Non-renewable fossil resources– this includes natural gas, oil, and carbon including uranium.
2. Renewable resources– including solar energy, wind, hydraulic, geothermal energy and biomass.
3. Nuclear energy– depending on the type of resource and the process that is used to obtain it, hydrogen can be classified in different colours.

Based on fossil resources

95% of hydrogen obtained is through other combustibles, where the biggest resource is natural gas. This form of obtaining hydrogen generates significant quantities of CO₂, although there are methods of recapturing the CO₂.

The chemical processes for obtaining hydrogen based on natural gas or carbon are:

1. Reforming the vapour: grey hydrogen
2. Partial oxidation: grey hydrogen
3. Reforming auto thermal: grey hydrogen
4. Vaporisation: blue hydrogen
5. Pyrolysis: turquoise hydrogen
6. Reforming the vapour/ vaporisation by capturing CO₂: blue hydrogen

Renewable resources 

Only so much as 4% of hydrogen is obtained based on renewable resources although currently, they are testing an impulse without precedents that can establish the basis for having a reality of its enormous potential such as clean energy. These processes for obtaining renewable hydrogen are the following:

1. Electrolysis: with the electricity of the yellow hydrogen network, renewable (wind, solar, hydraulic, biomass) green hydrogen.
2. Reforming the vapour: renewable (wind, solar, hydraulic, biomass) green energy.
3. The vaporisation of biomass: renewable (wind, solar, hydraulic, biomass) green hydrogen.

Nuclear energy

The production of hydrogen by the means of nuclear energy offers the opportunity to drastically recapture carbon emissions, but at the same time boost the profitability of the nuclear-electronic sector. The power of nuclear reactors can combine with a plant of hydrogen production to obtain a more efficient mode of energy and hydrogen in a co-generation system. The hydrogen by the means of nuclear energy can be obtained by the means of:

1. Electrolysis: purple hydrogen
2. Thermochemical cycles: purple hydrogen

Hydrogen storage

The effective storage of hydrogen is necessary for the development of an economy based on hydrogen. This is one of the main challenges because hydrogen is difficult to store. Like gas, it has a 7% density in the air and as a liquid, it is -253ºC and a 7% density in the water. So, depending on the final use of hydrogen, the systems of storage and the conditions must vary.

On one hand, they use stable storage systems, which they can employ in the generation of electric and thermal energy in the residential sector, decentralised generation of electricity, industrial uses, etc. In these uses, the systems of hydrogen storage have fewer limitations concerning the surface occupation, weight and volume, necessary for peripheral systems, etc.

On the other hand, for automotive uses, it presents large restrictions regarding the weight and volume, existing minimal limits of quality of hydrogen are increasing that it must be managed for the vehicles to achieve autonomy with the equivalent conventional vehicles that have been established by the Department of Energy of the EU.

Furthermore, exists other barriers to the operation conditions and hydrogen supply kinetics, that have conditioned their use combined with combustible batteries in cars, buses, lorries etc. It is because of this that is necessary to develop the technology that overcomes these barriers, for example improving isolation, weight lightening etc.

It should be noted that the characteristics of hydrogen make security a main conditioning factor when it comes to choosing a system of storing hydrogen. In this sense, exists different possibilities that fulfil in a large or small way, the requirements to be able to work in different situations. These systems of storage can be:

• Gas pressure
• Liquid (cryogenic storage)
• Metal hydrides
• Porous polymers such as active carbon, graphite, zeolites, MOF, COF, etc.
• In the form of chemical compounds (NH3, toluene, etc)
• In glass microspheres

Of all of these options, currently, only the first three present sufficient reliability of being presented in the market and being applied with certainty. Therefore, there is ample land for an open investigation.

Projects at AIMPLAS

At AIMPLAS we want to answer the challenges that entail the generation and use of hydrogen as a renewable fuel, and it is why we are working on different projects to look after the needs of the industrial sector and increase the possibility of applying innovative results obtained by companies.

The objectives pursued by the different projects are based on:

• Evaluation of alternative energy vectors to those of fossil origin from waste.
• Selective hydrogen production through catalyst-assisted thermochemical treatment processes.
• Design and modification of polymerics and nanoporous materials for the diverse effective storage of energy vectors improving weight and permeability.
• Study of the viability of the developments carried out for the generation of hydrogen by the means of valorising the complex plastic waste.

Author

Natalia Pons

Source

Aimplas blog, press release, 2023-03-01.

Supplier

AIMPLAS (Asociación de Investigación de Materiales Plásticos y Conexas)
Asociación española del hidrógeno - AeH2
European Commission
International Energy Agency (IEA)

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