Green hydrogen, produced by the electrolysis of water from renewable electricity, is considered to be a key energy vector for the energy transition. Electrolysers are the subject of increasing attention and major investments. In 2023, the global capacity of electrolysers installed was around 300 MW, with rapid growth expected. According to the IEA, it should reach 170 to 365 GW by 2030 to meet climate goals[1]. However, the large-scale deployment of electrolysers faces several major challenges, in particular the cost of producing green hydrogen (currently estimated between 3 and 8 €/kg, against 1 to 2 €/kg for gray hydrogen from natural gas)[2].
Table 1: comparison of the cost of producing electricity by 2030 from different energy sources (sources: [8], [9], [10], [11])
Four electrolyser technologies are currently on the market[3], alkaline and PEM technologies represent more than 85%:
1. The alkaline electrolyzer is the most attractive in terms of costs thanks to low-cost components. It is the most mature technology (TRL 9), although it has difficulties with intermittent renewable energies. Its industrialization is advanced.
2. The PEM electrolyzer (with a proton exchange membrane) is the 2nd most advanced technology (TRL 7-9), it recorded the strongest growth between 2015 and 2020. More compact and responsive, it nevertheless has an uncertain lifespan and requires the use of rare metals.
3. The SOEC electrolyzer (with solid oxides) uses nickel electrodes at low cost, is reversible (fuel cell and electrolyzer) and makes it possible to produce synthesis gas thanks to the co-electrolysis of CO2 and H2O. This fairly advanced technology (TRL 5-9) is the subject of projects under development in the Netherlands and Denmark.
4. The AEM electrolyzer (with an ion exchange membrane) should combine the advantages of alkaline and PEM technologies, technological maturity (TRL 4-6) requires progress in terms of lifespan and scalability.
At the technological level, R&D efforts focus primarily on improving conversion efficiency, with promising advances in the development of new electrode materials, catalysts and membranes[4] in order to reduce costs and improve current density, compactness and durability.
Another major challenge: electrolysers must be able to adapt to the intermittency inherent in wind and solar sources[5]. This is why numerous pilot projects are exploring the synergies between different technologies. Another challenge, perhaps the most complex, lies in the constraints associated with the storage and transport of hydrogen.
Despite these obstacles, the outlook is encouraging. Ongoing innovations - more efficient materials, increasing the lifespan of systems, better integration with intermittent sources - suggest viable solutions. However, the most promising technologies (SOEC and AEM) will probably not be mature enough by 2030 to meet the growing needs of the market. It is imperative to accelerate R&D efforts on these technologies.
The EU, Russia and Algeria[6] have announced ambitious goals and massive investments in the hydrogen sector. Europe aims for a capacity of 40 GW of electrolysers by 2030[6] : these commitments stimulate innovation and accelerate the reduction of costs. In this context, the race for innovation and market shares has generated tensions between Europe and China. The EU, concerned about Chinese dominance (40% of the world's electrolyser production capacity)[1], sets a ceiling of 25% of Chinese electrolysers [7] for the production of green hydrogen, which it subsidizes. Even though they represent 32% of the world market, European electrolyzer producers, including ThyssenKrupp and Siemens, are calling for support for Made in Europe[11].
Finally, the cost of electrolysers is in itself a challenge despite a significant decrease in recent years thanks to economies of scale and technological advances. In 2024, it varies between 500 and 1000 €/kW depending on the technology and the production scale, for an efficiency of 60 to 80% (PEM models)[8] being slightly more effective than alkaline ones) and a lifespan of 40,000 to 60,000 hours for most technologies, or 5 to 7 years in continuous operation.
In conclusion, significant investments are needed to improve electrolyser technologies, which constitute the most promising solution for hydrogen production which - unlike the steam reforming and pyrolysis process of methane - makes it possible to overcome dependence on natural gas.
Table 2: comparison of CO2 emissions from hydrogen production technologies and processes (source: [13])
As shown in Table 2, there is also a great interest in taking advantage of renewable energy systems such as photovoltaics to power electrolysers.
Despite current challenges, technological advances and supporting policies point to rapid deployment in the coming years. The success of this transition will depend on the ability to reduce costs, improve performance and develop the necessary infrastructure.
Image Credit: Process Sensing Technologies