Par Mariana Jimenez
- KTH-Institute of Technology
Le rôle clé de l'hydrogène dans le mix européen
Par Mariana Jimenez
- KTH-Institute of Technology
vendredi 28 février 2014
Le vecteur énergétique de l'hydrogène peut aider l'Europe à atteindre ses objectifs. A condition d'assurer un fort soutien à la R&D.(article en anglais)
The European Union has very ambitious plans to achieve a secure, competitive and decarbonized energy system in the years to come. For 2020, the European Commission has set three main goals known as the "20-20-20" targets. They include: a 20% reduction in EU greenhouse gas emissions from 1990 levels; rising to 20% the share of EU energy consumption produced from renewable resources; and a 20% improvement in the EU's energy efficiency . "Power-to-gas" is a new technology that transforms several sources into one common energy carrier: hydrogen. Can this molecule be the key to achieve the significant inclusion of more renewable sources into the future European energy mix?
Trouble in paradise
A low-carbon energy system with renewable sources in the center of the energy mix sounds like the perfect scenario. However, as it usually happens, several challenges must be overcome to make the dream come true. The intermittent nature of some renewable sources, like wind and solar, is considered one of the principal issues.
Intermittency can cause unwanted variations on supply that may lead to a lack of electricity or, on the other hand, to more production than the grid can support, therefore forcing the operator to switch off the equipment. In energy systems with small share of renewable sources this problem is easily controlled by the grid manager; but in the wanted future system, where renewables are main contributors, additional technologies to assure a constant and reliable supply of energy become critical.
Considering this, it is expected that energy storage technologies will play a key role in enabling the EU to develop a low-carbon electricity system. Energy storage can supply more flexibility and balancing to the grid, providing a back-up to intermittent renewable energy. Additionally, it can ease the market introduction of renewables, accelerate the decarbonization of the electricity grid, improve the security and efficiency of electricity transmission and distribution, and stabilize market prices for electricity while ensuring a higher security of energy supply. 
A promising technology
Nowadays, a smart proposal to store and transport energy is getting popular. This new pathway, known as "Power-to-gas", produces hydrogen using energy from several sources, renewables or not. The hydrogen acts like an energy carrier that can be stored, used directly for different purposes or be transported to another place for producing heat or power. Additionally, it can be combined with carbon dioxide to be transformed into methane. This synthetic gas can be used in regular engines with no modifications and it can be emissions-neutral if the CO2 needed for the methanation process is taken from the atmosphere, therefore recapturing the CO2 emitted on the combustion process. Moreover, hydrogen can be employed in fuel-cells where it has the additional advantage of producing power with only water as sub-product, meaning zero carbon emissions.
Figure 1. Green Hydrogen and Power-to-gas value chain. 
There's no such thing as a free lunch
The introduction of hydrogen as an additional energy carrier offers a lot of advantages for building the desired future energy system but, to take benefit of them, a lot of work needs to be done. As it usually occurs with new technologies, for "Power-to-gas" to become a competitive option, the market penetration and the public acceptance must increase. From the technical point of view, important breakthroughs have to be done on production, storage, distribution and safe handling of hydrogen to make it fully reliable and economically competitive; all together with improvement of related technologies, such as fuel-cells.
For example, electrolysis, the current method to obtain hydrogen from renewable energies, losses 10% to 30% of the input energy along the process , consequently increasing the price of the hydrogen produced. If the renewable technology itself has low energy conversion efficiencies, as occurs with photovoltaic, the hydrogen price can get considerable higher than the one obtained from non-renewable sources.
Figure 2. Prices of hydrogen (dollar per kilogram) obtained from different energy sources (left); using different processes (right). 
The distribution infrastructure is also challenging; it implies not only great demand on R&D to develop cheaper materials resistant to hydrogen embrittlement, but also cooperation between companies and local governments for constructing smart networks between regions.
Quality is always better than quantity
Clearly, investment in R&D is a key strategy and, as shown in the last report from the Joint Research Center , the European Union is aware of that. Compared to Japan or USA, Europe has invested less financial resources on developing hydrogen technologies, but earlier adoption of policies that encourage the use of renewable sources and cooperation between the European Union members can get results in shorter time if the financing is used wisely. Projects that demonstrate and stimulate early hydrogen markets must have higher priority, particularly if they include private companies, government and general public to have a bigger impact. A good example is the "Utsira Wind Power and Hydrogen Plant" project  which involved cooperation between private companies and educational activities to raise public awareness.
Introducing hydrogen as a complementary energy carrier will definitely help Europe to accomplish the "20-20-20" targets as it provides the advantage of store and produce clean energy while solving the problem of intermittency from renewable sources. However, for this to happen, is necessary to presently provide the conditions to make this option economically competitive for the future; this includes, especially, strong support on R&D and smart project development. The challenge is surely big but the potential benefits justify the efforts.
1. The 2020 Climate and Energy Package. European Commission web page. Visited 02/02/2014: http://ec.europa.eu/clima/policies/package/
2. The future role and challenges of Energy Storage. European Commission (2013), p. 1.
3. Green Hydrogen and Power-to-Gas Technology: Mass Energy Storage for the Future Energy Market. Germany Trade and Invest (2012).
4. Hydrogen: a future energy carrier? .Bennaceur K, Clark B, Orr F, Ramakrishnan T, Roulet C, Stout E. OilField Review (2005), p. 38.
5. Data taken from: An economic survey of hydrogen production from conventional and alternative energy sources. Bartels J, Olson N and Pate M. International Journal of Hydrogen Energy 35 (2010), pp. 8371-8384.
6. Science for Energy, Joint Research Center: The European Commission in-house science service (2013), p. 25.
7. Utsira Wind Power and Hydrogen Plant. IPHE Renewable Hydrogen Report (2011).
* An economic survey of hydrogen production from conventional and alternative energy sources. Bartels J, Olson N and Pate M. International Journal of Hydrogen Energy 35 (2010), pp. 8371-8384.
* Energy roadmap 2050, European Commission (2011). Visited 09/01/2014: http://ec.europa.eu/energy/publications/doc/2012_energy_roadmap_2050_en.pdf
* Green Hydrogen and Power-to-Gas Technology: Mass Energy Storage for the Future Energy Market, Germany Trade and Invest (2012). Visited 09/01/2014: http://www.gtai.de/GTAI/Content/EN/Invest/_SharedDocs/Downloads/GTAI/Fact-sheets/Energy-environmental/fact-sheet-green-hydrogen-mass-energy-storage-for-future.pdf
* Hydrogen: a future energy carrier?, Bennaceur K, Clark B, Orr F, Ramakrishnan T, Roulet C, Stout E. OilField Review (2005). Visited 09/01/2014: http://www.slb.com/~/media/Files/resources/oilfield_review/ors05/spr05/03_hydrogen_a_future_energy.pdf
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* The future role and challenges of Energy Storage, European Commission (2013). Visited 09/01/2014: http://ec.europa.eu/energy/infrastructure/doc/energy-storage/2013/energy_storage.pdf
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* The 2020 Climate and Energy Package. European Commission web page. Visited 02/02/2014: http://ec.europa.eu/clima/policies/package/
* Utsira Wind Power and Hydrogen Plant. IPHE Renewable Hydrogen Report (2011). Visited 02/02/2014: http://www.iphe.net/docs/Renew_H2_Ustira.pdf