The green hydrogen value chain commonly starts with water electrolysis: A process where water molecules are being split into hydrogen and oxygen. This process is fuelled by renewable energy sourced from e.g. solar, wind or hydro power.
How does the electrolysis of water work?
The electrolysis of water is achieved by applying an electrical voltage to electrodes immersed in water, which splits the water molecules (H2O) into hydrogen (H2) and oxygen (O2). There are different types of electrolysers that each use different electrolytes:
- Alkaline electrolysers utilise a potassium hydroxide solution as the electrolyte
- Proton exchange membrane (PEM) electrolysers use pure water
- “Solid Oxide Electrolyser Cell” (SOEC) electrolysers split steam into hydrogen and oxygen at temperatures reaching up to 850 °C
Around 50-55 kWh of electricity is required to produce 1 kg of hydrogen, although the exact energy required can vary depending on the efficiency of the electrolyser. This energy demand can be covered using renewable energy sources such as solar, wind or hydro power in order to produce green hydrogen. In addition, around 9 litres of water are needed to produce 1 kg of hydrogen. This is not only an energy-related but also a water-related investment, which has to be considered especially in regions with water shortages.
Why produce hydrogen via electrolysis?
This process can be powered by renewable energy, thus producing green hydrogen. Green hydrogen is climate-neutral and contributes to reducing CO2 emissions. Additionally, hydrogen can act as an energy storage and be used in various sectors such as industry, mobility and energy supply. By combining different technologies and energy sources, synergies can be utilised to increase the efficiency of hydrogen production.
How high is the efficiency of hydrogen production using electrolysis?
The efficiency of hydrogen production using electrolysis is currently around 60-70 %, depending on the type of electrolyser. This means that 60-80 % of the electrical energy used is converted into chemical energy of the hydrogen. Technological improvements can further increase this efficiency in the future.
Each electrolyser concept for the electrolysis of water poses its unique set of challenges in terms of process pressure, temperature and media. Our broad range of pressure, temperature, flow and level measurement solutions addresses these challenges, thus ensuring efficient and safe operation of the electrolysers for the electrolysis of water. High-temperature electrolysers such as SOEC offer particular advantages due to their higher efficiency, but they require special materials for electrodes and electrolytes to withstand the high temperatures.
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