Active for a sustainable future: challenges in the production of green hydrogen from wind and solar energy

Authors: Telsche Nielsen, Viktor Deleski

At Fraunhofer IWES, we are actively committed to renewable energies. Day in, day out, we support and further the development of technologies in the fields of wind energy and hydrogen. As an institute for applied research, sharing our knowledge and experience is also something very important to us: strong alliances secure rapid knowledge transfer from research and development, with universities and industry benefiting equally.

Current predictions indicate that it will still be some years before hydrogen technologies achieve greater relevance in the production and utilization of energy. [1] In order to expedite this process, it is important to train specialists and managers in the field of hydrogen technologies. The production and utilization of green hydrogen requires specific technical knowledge and expertise. This gap can be closed via tailored professional training measures for specialists and managers.

It is no secret that hydrogen is a firm favorite to replace crude oil and natural gas as the energy carrier and material of the future. But how can it be sustainably produced in large quantities in the future? We invited our colleague Telsche Nielsen, Head of Knowledge Transfer & University Cooperations, to explore this issue in more detail with us.

Electrolysis is a process in which electricity is employed to split water into its chemical components, hydrogen (H) and oxygen (O). The reaction produces gaseous hydrogen (H2) and gaseous oxygen (O2). Hydrogen is therefore an energy carrier and not an energy source, as the electrical energy of the electricity is converted into chemical energy during electrolysis. A significant contribution to combating climate change is only possible here with green electricity sourced from wind and solar energy or other low-CO2 forms of energy production.

Telsche, where do we stand currently on the topic of hydrogen production with wind energy? Has progress been made compared with 2022?

At present, almost 0% of electricity is still being used to produce green hydrogen, but we are no longer right at the very beginning, as many players have now made a start. The green hydrogen currently being produced in real labs and test facilities is still only marginally available commercially. However, the European Renewable Energy Directive (RED III) was signed on October 18, 2023. It regulates the definition of acceleration areas and standardizes the permitting processes. It is considered a milestone for the energy transition. [2] As a result, it will be possible to implement hydrogen projects successfully in less time in the future.

How high could the share of green hydrogen in the energy supply be in the future?

In its scenarios covering the next three decades, the Fraunhofer Institute for Solar Energy Systems ISE predicts that it could still be some years before hydrogen technologies achieve greater relevance for the supply and utilization of energy. [3] We need to lay the foundations for this today. After all, there are many applications in which we will require hydrogen as an alternative energy carrier to oil and gas in the future. In this regard, it is advantageous that hydrogen can be stored for long periods without loss and transported over great distances. At present, there is still far too little green electricity available for electrolysis for large quantities to be produced at low cost. However, the energy transition can also only be successful if hydrogen becomes affordable too. Ultimately, CO2 emissions need to be reduced greatly and legally regulated in parallel. The best way for this to be a success is if we start establishing interdisciplinary solutions in various ways now.

What positive progress has been observed?

Some electrolyzer manufacturers have been in series production since 2023 and, thanks to full order books, are now selling their systems all over the world. The existing electrolysis plants are generally still running in research or pilot operation, but the foundations are being laid here for the sustainable energy supply of the future.

For example, a pilot H2 plant was installed in Lingen, Lower Saxony, in the fall of 2023. As soon as the commissioning process is complete, a PEM electrolyzer with a capacity of 4 MW and a pressurized alkaline electrolyzer with a capacity of 10 MW will begin producing green hydrogen. The electricity for the electrolysis is supplied by offshore wind turbines located in the North Sea. The hydrogen will be fed into a local hydrogen network and used as fuel for gas turbines in power plants. [4]

In Bad Lauchstädt, Saxony-Anhalt, an energy park is currently under construction which is scheduled to be commissioned in 2025 by a natural gas business group active across Europe and a listed energy trading company. Here, a wind farm with a capacity of 50 MW is set to supply a 30 MW pressurized alkaline electrolyzer. The special local situation permits storage of the produced hydrogen in salt caverns as well as transport via the H2-ready natural gas network to a refinery in Leuna. [5]

One last, exciting foundation stone currently being laid is the “Electrolysis corridor in east Germany”. This is a subproject in the “Doing Hydrogen” program, which is backed by a large consortium of companies. The plan is to produce green hydrogen on an industrial scale along a planned hydrogen pipeline with a total capacity of at least 210 MW crossing Mecklenburg-Western Pomerania, Brandenburg, Berlin, Saxony-Anhalt, and Saxony. [6] According to the H2-Compass, the current status of announced electrolysis capacities until 2030 amount to “a cumulative electrolysis capacity of 4.3 GW (referring to electrical power consumption), which corresponds to just under 50% of the target agreed upon in the coalition agreement (10 GW). If undated projects are included in the analysis, the announced electrolysis capacity increases to 7.6 GW.” [7]

What other approaches exist for harvesting green hydrogen?

Another highly promising approach for the sustainable use of electrolyzers is the possibility for combining them with sewage treatment plants. The German Environment Agency (UBA) identifies sewage treatment plants as the largest energy consumers in urban communities, accounting for approximately a fifth of the total energy requirement. [8] The city of Hannover hopes to achieve more efficient operation of its sewage treatment plant via an innovative joint project. The aim is to save energy by coupling sectors, thereby utilizing local infrastructure more efficiently. The first planned step is the expansion of renewable energies in order to produce the green electricity required. This will then be employed in an electrolysis plant to produce hydrogen along with (waste) heat and oxygen as by-products. The heat is to be fed into the local district heating network, whereas the hydrogen will serve as fuel for the buses of the local transport system in the city and the oxygen can fulfill two functions at once: the obvious one is to utilize the oxygen for the biological wastewater treatment stage. In the current state of the art, the microorganisms required for the process are supplied with air (with an oxygen content of just 21%). However, if pure oxygen were used instead, the microbes would be able to work more efficiently, and less energy would be required to run the pumps used to aerate the tanks. That translates to green energy savings.

The second function of the oxygen is gaining in relevance in light of a new EU directive, according to which all cities and municipalities with more than 100,000 inhabitants will be required to introduce a fourth purification stage in wastewater treatment, known as ozonation, starting in 2035. This new, additional wastewater treatment stage removes pharmaceuticals and pesticides from the wastewater efficiently. [9]

In addition to the national projects, there are also many projects in sparsely populated regions with excellent wind and solar resources for the production and export of hydrogen or corresponding energy carriers. However, it remains the case that the production of green hydrogen in large quantities is still directly dependent on the expansion of wind and solar energy.

© Jens Lehmkühler

What technical equipment is required to produce green hydrogen and what size must the plant be?

The process requires:

  • a water purification plant;
  • an electrolyzer;
  • a hydrogen post-processing plant;
  • a pipe system;
  • a hydrogen storage system;
  • power electronics;
  • control technology;
  • auxiliary equipment such as pumps and compressors;
  • and, above all, green electricity.

The size of the electrolyzer determines the size of the other components. The systems can be modular in design and thus be adapted as needed to the regional and supra-regional requirements. Large plants have electrolyzers with capacities of 1 MW to 10 MW; even larger systems are already under development.

How significantly is the stagnating expansion of wind energy affecting hydrogen production?

Very, as the high electricity prices at present (barely) allow hydrogen production. We certainly need higher wind and solar energy capacities to cover the increasing electricity demand (e.g., for the electrification of the transport sector), plus green electricity available for the production of green hydrogen as an energy store for the areas that cannot be operated with green electricity.

How costly is the production of green hydrogen from wind energy compared with conventional methods?

The production of hydrogen via an electrolyzer with wind energy or another renewable technology is primarily more sustainable than the conventional approach involving steam reforming of natural gas. Steam reformers are also generally large, centralized systems – a significant difference to the modular electrolyzers, which can be installed anywhere. The decisive disadvantage of steam reforming of natural gas is that it produces large quantities of climate-damaging CO2. Although it is possible to separate the CO2 in the waste gas, this requires additional energy, and the separation is incomplete. In addition, climate-damaging methane escapes into the atmosphere during the extraction, transport, and storage of the natural gas required for the process. Furthermore, the natural gas largely needs to be imported – which is a hurdle to a politically independent energy supply system.

How efficient are electrolyzers at present and what is a realistic goal?

The efficiency of the different types of electrolyzers is up to 68%, with alkaline electrolyzers proving a little more efficient than PEM electrolyzers. If steam at high temperature is available, high-temperature electrolyzers are even more efficient. [10] There is still potential to improve the efficiency of the electrolyzers by a few percent at both technology and system level, and we are conducting corresponding research at our hydrogen test fields, our Hydrogen Labs, in Bremerhaven, Leuna, and Görlitz. [11] Further optimization at materials level is also ongoing and a focus of the work of our colleagues at Fraunhofer IMWS, for example.

How much electricity is required to produce 1 kg of hydrogen?

In theory, 42 kWh are required for the production of 1 kg of hydrogen. In practice, however, it is 55 kWh with a PEM electrolyzer due to the energy required for the continuous operation of the electrolyzer and all the secondary components.

How practical is a heat pump actually from an energy perspective?

When greenhouse emissions are considered, heat pumps are unbeatable in terms of energy efficiency. The energy efficiency of heat pumps depends on a wide range of variable factors affecting their performance and environmental compatibility. The source temperature and flow rate are two such factors. It is well known that a high source temperature is advantageous, but the efficiency drops immensely if the flow rate is low. The refrigerants and their GWP (global-warming potential, in case of leaks) values must also always be taken into account. These three factors are joined by a whole host of others. A suitable heat pump must be chosen here for each respective application. However, everything ultimately depends on the use of the right electricity. Green electricity transforms any heat pump, irrespective of how inefficient it is considered, into an energy supply system with significantly lower CO2 emissions. At this point, it is worth mentioning Fraunhofer ISE’s investigations, which have made a considerable contribution to the further development of heat pumps. [12]

How can we utilize the potential of hydrogen and expedite the energy transition?

Hydrogen is nothing new for certain sectors like the chemical industry. Generally speaking, its properties are well researched and its potential clear. However, its implementation, especially as an energy carrier, has been less than successful thus far and has not progressed quickly enough for the reasons outlined above. Now, however, the framework conditions and application scenarios have changed. What is still lacking, in addition to the technical advances in electrolyzers, is the development of a hydrogen economy with planners, engineers, technicians, and a wide range of other specialists involved in the whole value chain. This requires education, information, and above all, skills development. Specialists and managers need to acquire the skills to plan and implement hydrogen projects efficiently. Additional efforts are required to develop skills targetedly and establish the requisite qualification processes, both in the dual education system and, especially, in professional training.

Drawing on the latest scientific findings, we are collaborating with the Fraunhofer Academy to develop practice-related and tailored training programs for companies. The following links provide further information:


[1] Study: “Paths to a Climate-Neutral Energy System – The German Energy Transition in its Social Context”
[3] Study: “Paths to a Climate-Neutral Energy System – The German Energy Transition in its Social Context”, 11/2021 update, p. 25, 01/17/2024
[4] Lingen pilot H₂ electrolysis plant | RWE hydrogen project
[5] Start / Bad-Lauchstädt Energy Park (
[7] Production capacities | H2-Compass (
[8] Energieeffizienz kommunaler Kläranlagen (
[9] Hannover plant den Aufbau einer regionalen Wasserstoffherstellung, Wasserstoff: So werden aus Kläranlagen grünen Fabriken (
[10] Clean Hydrogen JU – SRIA Key Performance Indicators (KPIs) (
[11] IWES_Datenblatt_HLB_en.pdf
[12] Auch in Bestandsgebäuden funktionieren Wärmepumpen zuverlässig und sind klimafreundlich – Feldtest des Fraunhofer ISE abgeschlossen – Fraunhofer ISE

More information here:

Applied research at Fraunhofer IWES
ILES summer school 2021: From theory to practice – students get hands-on experience
Progress as a necessity

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