Wiki - All about hydrogen

Updated on 19 June 2024

Electrolysis technologies

Electrolyzers are devices that utilize electricity to split water or other electrolytes into hydrogen and oxygen. The associated process is called electrolysis. Various electrolyzer technologies exist, each with its own advantages, disadvantages, and characteristics.

Certain commonly used electrolyzer technologies are summarized here to provide an overview:

  • Alkaline Electrolyzers: This type of electrolyzer uses a liquid alkaline electrolyte for the electrolysis process, typically a solution of potassium hydroxide (KOH). The systems operate at relatively high temperatures and usually produce hydrogen at medium pressures of 10-30 bar(g). They have been used for several decades. Alkaline electrolyzers are known for their efficiency, durability, and relatively low cost. They are commonly used in large-scale industrial applications and for hydrogen production, but new versions can also be used in connection with renewable energy sources. Certain variants produce hydrogen just above ambient pressure.
  • Proton Exchange Membrane Electrolyzer (PEM): PEM electrolyzers use a solid polymer electrolyte membrane, such as Nafion, which selectively allows the transport of protons (H+). PEM electrolyzers operate at lower temperatures and higher pressures of 30-40 bar(g) compared to alkaline electrolyzers. They offer rapid response times, high efficiency, and flexibility for dynamic operation. PEM electrolyzers are suitable for various applications, including renewable energy storage, hydrogen fueling stations, and small-scale distributed systems.
  • Solid Oxide Electrolyzer Cell: This type of electrolyzer operates at high temperatures of typically above 600°C and use a solid ceramic electrolyte, such as yttria-stabilized zirconia (YSZ). The technology has the advantage of being reversible, meaning that an electrolyzer machine is at the same time also a fuel cell that can produce electricity from hydrogen. These electrolyzers are primarily used in large-scale applications in which high-temperature heat sources, such as excess waste heat or renewable energy, are available. One company that is known for this technology and has erected relatively large electrolyzers based on the technology is Bloom Energy.
  • Anion Exchange Membrane (AEM) Electrolyzers: AEM electrolyzers utilize an anion exchange membrane as the electrolyte. AEM electrolyzers are an emerging technology in the field of hydrogen production and are gaining attention for their potential advantages over other electrolyzer technologies, in particular that they do not require rare metals such as other technologies. One solution is commercially available today. An example of an AEM application in a GRZ project is the EWB project.
  • Photoelectrochemical Electrolyzer: This technology uses combine light-absorbing semiconductors and electrochemical processes to drive the water splitting reaction. The electrolyzers use solar energy to generate the electricity needed for electrolysis, eliminating the need for an external power source. Today, the technology is still in an early stage of development, but holds promise for sustainable and direct solar-driven hydrogen production.

The image below shows a PEM electrolyzer used for the production of hydrogen for a FLEXI HyCo storage compression device.

FLEXI HyCo storage compression device with a PEM electrolysis system.
A hydrogen compressor manufactured by GRZ and a PEM electrolyzer that produces approximately 36 norm liters per hour, i.e, ca. 3.2 gH2/h.

Each electrolyzer technology has its own set of advantages, including efficiency, operating conditions, scalability, and cost. The choice of electrolyzer technology depends on factors such as the application, scale of production, available infrastructure, and specific requirements of the system.

GRZ has integrated different manufacturers from lab to MW-scale and can help you realize your project successfully.

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