Green hydrogen

Of all fuels, hydrogen has the highest energy content1, is relatively easy to produce and easy to transport. In the context of the energy transition, hydrogen is therefore a beacon of hope for mobile and energy-intensive applications. Its use in industry, transport, heating and electricity supply should preferably take place where it is superior to green electricity or even represents the only option.2 Only "green" hydrogen, produced exclusively by means of renewable energies, is climate-neutral.



Relevance of the field of application

In terms of industrial applications, the chemical industry in Germany is leading the way in hydrogen use, with a current demand of 1.1 million t (37 TWh). According to estimates, this demand will increase to 7 million t (227 TWh) by 2050, particularly for the CO2-based synthetic production of naphtha, which is used as an intermediate product in a wide range of production processes.2 Among the frontrunners of future hydrogen demand in industry are also the steel industry, which wants to substitute fossil gases in the blast furnace line with hydrogen3 (2 million t or 70 TWh in 2050)2 and the cement industry, which wants to convert captured CO2 into chemical feedstocks or synthetic fuels.2

In the mobility sector, hydrogen will play a role above all in the area of heavy goods transport by truck, ship and rail. A pioneering role for rail transport is played by the company Alstom, which was nominated for the German Sustainability Award Design 2022 for the presentation of the world's first fuel cell train "Coradia iLint".4 A hydrogen demand in the mobility sector of 0.8 million t (25 TWh) is already considered plausible for 2030, with an increase to 6.1 million t (203 TWh) by 2050.2 A significant increase in hydrogen demand is also expected in the heating and electricity supply sectors due to the substitution of fossil gases as well as an increasing hybridisation of regulating power plants.2

However, only green hydrogen contributes to the climate neutrality of the economy, as only its production relies exclusively on renewable energies. In contrast, the hydrogen used today is mainly produced from fossil fuels and the CO2 produced is released into the atmosphere ("grey" hydrogen) or permanently stored underground ("blue" hydrogen). "Turquoise" hydrogen relies on the thermal fission of methane with the capture of solid carbon - a process that could theoretically be climate-neutral, but in practice also leads to significant greenhouse gas emissions, mainly because of extraction and transport losses of methane, a potent greenhouse gas.5,6



1 Schnurnberger, Wener (2004): Wasserspaltung mit Strom und Wärme. In ForschungsVerbund Erneuerbare Energien (FVEE) (2004): Methoden der Wasserstofferzeugung. FVS Themen 2004. 
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2 Nationaler Wasserstoffrat (2020): Wasserstoff Aktionsplan Deutschland 2021 – 2025.
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3 Thyssen-Krupp (2020): Mit Wasserstoff zur klimaneutralen Stahlproduktion.
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4 Stiftung Deutscher Nachhaltigkeitspreis (2021): Deutscher Nachhaltigkeitspreis Design 2022. Die Finalisten. 
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5 Bundesministerium für Bildung und Forschung (BMBF) (2021): Nationale Wasserstoffstrategie. Wissenswertes zu Grünem Wasserstoff.
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6 Klimareporter (2021): Industrie drängt auf fragwürdiges Verfahren. "Türkiser" Wasserstoff mit kritischer Klima-Bilanz.
Link ↗ (accessed 02.10.2021)

Use of battery storage

The production of green hydrogen is based on electrolysis. It is the technically simplest production approach and at the same time has a relatively high energy efficiency.1 The electrolysis processes differ in the electrolytes used and the operating temperatures for the respective optimum efficiency: alkaline electrolysers operate with aqueous caustic potash solution at 80 °C, membrane electrolysers with a proton-conducting membrane at 80 °C and steam electrolysers with a ceramic membrane as oxygen ion conductor at 650-1000 °C.1 In general, the production of hydrogen is extremely energy-intensive. For example, the production of 1 g of hydrogen requires 145 kJ of energy. On the other hand, the high energy content of hydrogen is an advantage: the combustion of 1 kg of hydrogen releases the same amount of energy as the combustion of 2.75 kg of petrol.1

Green hydrogen has already been produced from surplus wind power for some time under the name "wind gas". In the future, however, hydrogen will be produced primarily by means of renewable energy plants that have been built specifically for this purpose. A particularly attractive feature of the direct coupling of electrolysers to generation plants is that even strong, short-term fluctuations, such as those caused by gusts of wind, can be used for hydrogen production by electrolysis without delay.1 It is true that the efficiency of electrolysers is generally highest in part-load operation. However, an undersupply of electricity in the lower partial load range is detrimental to product quality.1 The increase in energy efficiency in hydrogen production makes the use of battery storage systems advantageous: load peaks occurring in the generation plants can be smoothed out by intermediate storage, periods of undersupply of electrical power can be reduced compared with direct coupling to the generation plant, and the number of productive hours in the optimum operating range of the electrolysers can thus be increased overall. The coupling of generation plants, electrolysers and battery storage is currently also being discussed for the hybridisation of PV plants.7

The design of battery storage systems to increase the efficiency of hydrogen production depends on the plant specifics of the electrolysers used, the load profiles of power generation and the battery technology used.


7 Astakhov, O.; Agbo, S. N.; Welter, K.; Smirnov, V.; Rau, U.; Merdzhanova, T. (2021): Storage batteries in photovoltaic–electrochemical device for solar hydrogen production. In: Journal of Power Sources, Volume 509, 15 October 2021, 230367.
Link ↗ (accessed 02.10.2021)

Performance requirements

Enormous amounts of renewable energy are required for the large-scale production of green hydrogen. Therefore, the use of battery storage for hydrogen electrolysis is basically a high-load application in which the longevity of the battery plays a central role. In conjunction with the high energy content and the corresponding explosion risks when handling hydrogen, the safety of the battery technology is also crucial.

As the production of green hydrogen focuses on the sustainability of the future energy supply, the battery storage systems used should also meet high sustainability standards. An important, often overlooked point here is the size of the required energy storage unit: the combination of specific energy, longevity, fast-charging capability and deep-discharge resistance is decisive for the dimensioning - and thus also for the corresponding environmental impacts.


Market outlook

The market for green hydrogen is seen as an enormous growth market. Accordingly, there is great interest in participation on the part of German and European policymakers. Above all, the aim is to exploit the growth opportunities of this key technology and to position Germany and Europe as innovation drivers. This concerns plant construction as well as the downstream use of hydrogen. The considerations on production and distribution explicitly include third countries outside the EU, which are to be integrated into a supply strategy within the framework of cooperation strategies.5

With regard to the market size for battery storage to increase efficiency in the production of green hydrogen, there are currently no serious estimates. Assuming alone the forecast demand in Germany of 15.1 million t (500 TWh) presented above, an energy quantity of at least 608 TWh of electricity from renewable energies is required annually for hydrogen production.1,2 If electricity generation from renewable energy sources is uniform on a daily basis and buffer storage of 6 hours is used to compensate for daily fluctuations in electricity generation, the buffer storage requirement for batteries would already be 416 MWh. Converted to a production plant for 100,000 t of hydrogen per year, this would correspond to a battery storage facility with a size of 3 MWh, which seems plausible in view of current project plans.