Green Hydrogen Production  

Discover our electrolyzer and large-scale hydrogen solutions for sustainable energy systems

Benefits of green hydrogen

Green hydrogen (H2) is a versatile energy carrier that can be applied to decarbonize a wide range of sectors. It can be used directly or in the form of its derivatives like e-methanol, e-ammonia, or e-fuels to replace fossil fuels, coal or gas.

Only around 40% of global carbon dioxide (CO2) emissions originate from power generation which can be decarbonized via electrification. The other 60% of CO2 emissions originate from industry, mobility, buildings and others. These can be decarbonized via sector coupling, using green hydrogen and its derivatives to make renewable energy available to those sectors. This is why the production of sustainable hydrogen is such a crucial issue.

EFCF 2023: Low-Temperature Fuel Cells, Electrolysers & H2 Processing Forum 

Siemens Energy participated in this year's European Fuel Cell Forum (EFCF), which took place in Lucerne, Switzerland, in early July 2023. Carlo Locci presented his poster A1519: "Scaling up electrolysis production: challenges and perspectives". If you want to learn more about it, please follow the link to the recorded presentation.

Our electrolyzer portfolio: The optimum solution for large-scale sustainable hydrogen production

Generating green hydrogen efficiently from water and renewable energy requires high-end technology and innovative solutions — like the Silyzer product family from Siemens Energy. Using Proton Exchange Membrane (PEM) electrolysis, the Silyzer is ideally suited for harnessing volatile energy generated from wind and solar. Combining high efficiency and high power density, our PEM electrolyzers ensure gas products of superior quality. It is easy to operate and requires low maintenance. Using a modular design strategy that splits the electrolysis system into skids, we are able to optimize costs, reduce installation costs, and make the electrolysis system transportable.

Scaling up the capacity of green hydrogen production

Carbon emission targets in the European Union and other industrialized countries will require massive scaling-up and acceleration of renewable hydrogen production and imports – already 20 million tons will be needed in Europe by 2030 to fast forward the energy transition and decarbonization.

That’s why we have joined forces with Air Liquide to create a joint venture dedicated to the series production of industrial-scale renewable hydrogen electrolyzers. In 2023, production of electrolysis stacks will begin at our multi-gigawatt electrolyzer facility in Berlin and ramp up to an annual production capacity of three gigawatts by 2025.

The factory will supply stacks to Siemens Energy and Air Liquide for our broad range of customers and serve the rapidly growing market. 

Your service partner for green hydrogen production and beyond

Siemens Energy can offer comprehensive services for your electrolyzer plant and energy assets along the entire hydrogen value chain. Our service agreements range from basic maintenance to premium service with state-of-the-art data analysis and can be customized to your needs.

Our combined package of maintenance, support and digital services can ensure reliable and economical operation. You can reduce your risks with our performance guarantees or enjoy total peace of mind with our Operations and Maintenance service program. Together, we will push your clean hydrogen production to the next level.


Our System in the field

How does PEM Water Electrolysis work?

To limit climate change caused by the global increase in CO2 emissions, we need solutions for generating carbon-neutral and sustainable fuels. The generation of green hydrogen is achieved by electrolysis using renewable energy rather than producing it from natural gas, which results in large amounts of CO2 emissions.


For our hydrogen electrolyzer system, we focus on PEM technology taking its name from the proton exchange membrane. The membrane’s special property is that it is permeable to protons but not to gases such as hydrogen or oxygen. As a result, in an electrolytic process the membrane takes on, among other things, the function of a separator that prevents the product gases from mixing. 

Your partner for sustainable hydrogen production

With our extensive knowledge of industrial, mobility, and energy sectors, we’re able to provide dependable solutions for our customers in every aspect of green hydrogen production.

You will benefit from Siemens Energy’s decades of experience, global footprint, infrastructure, strong partnerships and manpower available, covering the full energy value chain from renewable power via transmission to hydrogen and Power-to-X production. Moreover, we can help you certify the source of green energy with Clean Energy Certificates.  


Are you ready for the green hydrogen economy? We are and we look forward to being your partner for sustainable hydrogen generation. 

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FAQ – The most common questions on hydrogen

Hydrogen (chemical symbol H) is a gas. As a molecule (H2), it occurs only in small amounts in nature and it is mainly chemically bound, such as H2O.

Hydrogen is the most abundant element in the universe. 90 percent of all atoms are hydrogen atoms. They add up to three quarters of the total mass in the universe.

Hydrogen converts into a liquid at minus 253 ºC.

Hydrogen has the highest energy density of all conventional fuels by mass: almost three times as high as that of gasoline or diesel. That is one of the reasons why hydrogen is used as fuel for space travel.


H2 Higher  Heating  Value: 39.4 kWh/kg; H2 Lower Heating  Value: 33.3 kWh/kg

By combusting hydrogen, it delivers heat. Used in fuel cells, hydrogen is converted electrochemically  to electrical energy.

Hydrogen has been produced and used for more than 200 years. Experience shows that hydrogen can be stored, distributed and converted safely. As early as 1808, the first large-scale use of hydrogen was established for the street lighting system in London.

Hydrogen (H2) can be produced in different ways. For the moment more than 95% of the hydrogen worldwide is produced from hydrocarbons while producing and emitting harmful CO2. A more modern and ecofriendly technology for CO2 neutral production of hydrogen can be offered by electrolysis of water.

Hydrogen can be produced from hydrocarbons by steam reforming of natural gas - often referred to as steam methane reforming (SMR), coal gasification and from an electrolysis process of water (H2O).

Hydrogen can be stored in tanks as a compressed gas or as a liquid. Hydrogen can also be stored in caverns or in the natural gas grid for different applications and if the grid fulfils all technological requirements.

The volumetric energy density of hydrogen at atmospheric pressure is approximately one third of traditional fuels. The volumetric energy density can be increased by compression or liquefaction of the hydrogen gas to store and transport a greater amount of hydrogen.

For hydrogen-powered vehicles, an industry standard of 300 to 700 bar has been established. Vehicles for the transport of compressed hydrogen, so called “tankers”, usually working with a maximum pressure of 200 bar.

Hydrogen can be transported as a compressed gas or a cryogenic liquid. Today, the two main methods for transporting hydrogen (primarily in a gaseous state) are via tanker e.g. tube trailer for road transportation and in gas pipelines (for short distance).

Hydrogen is a non-toxic clear gas. It is not poisonous, has no taste or odor. Using hydrogen as a fuel source with fuel cells does not create fumes, pollute the atmosphere with carbon dioxide or emit nitrogen oxides.

It is not inherently more dangerous than other fuel sources.  Hydrogen is flammable and must be handled with care, just like other flammable fuels. To ignite, the hydrogen must be combined with an additional oxidizing agent (air, pure oxygen, chlorine, etc.) in a specific  concentration and an ignition source (a spark). If, in a worst-case scenario, the hydrogen ignites, it burns upwards very quickly. It creates no dangerous heat radiation above the accident site, as petrol or kerosene do.

The facilities are designed to be permanently leak proof. Flange connections are designed especially for hydrogen and the number of detachable connections are minimized. Furthermore, in buildings a steady air exchange is ensured and the facilities are equipped with safety valves and pressure reliefs. Additionally explosion prevention zones are designated. In these zones, electrical and other equipment needs to be in accordance with 2014/34/EU (ATEX Directive).

No. Hydrogen can be safely handled and stored as well as transported. The industrial gas industry has done so for over a century.

In contrast to gasoline and natural gas, hydrogen gas has significant buoyancy in atmospheric conditions due to its low density, any leaking hydrogen gas ascends immediately and disperses, which reduces the risk of an ignition in open air.

Water gets split into its components hydrogen and oxygen by means of electrical current.

Electrolysis processes can be categorized as follows: alkaline electrolysis with liquid alkaline electrolytes, acidic electrolysis with a solid polymer electrolyte (as PEM) and high temperature electrolysis with a solid oxide as electrolyte.    


PEM electrolysis and alkaline electrolysis systems are available at an industrial scale. The solid oxide electrolysis technology is in an early development phase.

PEM is the abbreviation for proton exchange membrane. This membrane is a crucial part of the electrolytic cell in a PEM-electrolyzer. The membrane separates the anode, where the oxygen is collected, and the cathode, where the hydrogen gas is generated.

The type of the ions which closes the electric circuit


  • PEM: H+
  • Alkali: OH-
  • SOE: O2-
  • High gas purity >99,999%
  • High dynamics
  • High efficiency (>70%)
  • High power density
  • High life cycle
  • Clean (no chemicals, only water and electricity)

10 liter demineralized water is needed for 1kg of hydrogen.

On average 50kWh are necessary to produce 1kg of hydrogen, depending on the efficiency of the electrolyzer and operation mode.

The hydrogen market is divided in three sectors. Mobility, energy and industry with industry being by far the largest consumer today (~90%). In the future a redistribution towards the mobility and energy sector is expected .

Today, hydrogen is an important industrial gas, i.e. for the refining of fuels, for the production of fertilizer and methanol, for the hydrogenation of fats, for steel production, metal processing, as well as in the production of flat glass.

Less than 1kg of hydrogen is needed per 100km.

Passenger car or light duty vehicle fueling takes 3 to 5 minutes.

Hydrogen enables the long-term storage of large quantities of surplus renewable energy. It is allows new ways to use green electricity, i.e. by using hydrogen as substitute for natural gas by feeding it into existing pipelines, as fuel for fuel-cell vehicles or power plants, or as feedstock for the hydrogen processing industry. It opens the possibility to connect energy generation with the industry and mobility sectors, the so called “sector coupling”.

No. Hydrogen will become a substantial and permanent element of a sustainable energy industry.

In the future, hydrogen will be produced to a greater extent using electricity from renewable energy sources. Furthermore, biogas and various fuels like solid biomass will help to produce green hydrogen in the future.

‘Green’ hydrogen is sourced by 100% renewable energy. That means that the needed energy to produce hydrogen by electrolysis has emitted zero emissions. Hydrogen produced from fossil fuels releasing emissions such as CO2, may be referred to as ‘grey’ or ‘brown’ hydrogen. If the emitted carbon dioxide is captured, stored (carbon capture storage) and re-used, it is often called ‘blue’ hydrogen.


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