Electrolyser technologies

FinH2 project focuses especially on the value chains for hydrogen produced by water electrolysers, powered by renewable electricity. One goal of the project is to find the most appealing options from the Finnish perspective. By knowing more about electrolyser technologies, Finnish companies can find opportunities to offer their products and services along the value chains in the future.

Two types of electrolysers, alkaline electrolyser (AEL) and polymer electrolyte membrane (PEM) electrolyser, are already commercially available technologies, while anion exchange membrane (AEM) and solid oxide electrolyser cell (SOEC) are technologies under development. Though alkaline and PEM electrolysers are commercially viable, there is still room for improvements. FinH2 project aims at improving the performance of the technologies as well as optimising them for sector-coupling. SOEC technology is developed in multiple other national and EU projects by FinH2 participants.

Green Hydrogen Cost Reduction
The basic principle of three different types of water electrolyser technologies. Source: IRENA (2020), Green Hydrogen Cost Reduction: Scaling up Electrolysers to Meet the 1.5⁰C Climate Goal, International Renewable Energy Agency, Abu Dhabi.

Alkaline electrolysis

Alkaline electrolysis is a well-known and mature technology for green hydrogen production. It requires less scarce raw materials with a relatively simple construction. Cost reductions and technology development can be achieved by e.g., increasing the operating temperature of the electrolyser to 130-150 ºC.

Alkaline imageAlkaline electrolysis stack (most common) materials

  • Diaphragm: ZIRFON
  • Electrolyte: potassium hydroxide (KOH)
  • Electrode catalysts: nickel mesh
  • Bipolar plates: nickel-coated stainless steel

Alkaline electrolyser system components

  • Stack
  • O2-liquid separator
  • H2-liquid separator
  • Electrolyte pumps + heat exchangers
  • H2 purification system
  • Water treatment system
  • Power electronics + automation system

PEM electrolysis

PEM electrolysis has become commercial in the recent years, with the benefit of producing high purity hydrogen with rapid power ramp rates and wide power range. Furthermore, it has a compact design. The challenges of the technology are currently the higher cost compared to alkaline electrolysis and the need for noble metal catalysts. FinH2 project increases know-how and experience on PEM electrolyser technology by designing, building, and demonstrating a PEM electrolyser system optimised for sector coupling. Furthermore, an iridium-free catalyst will be developed to overcome the barrier of shortage of suitable catalyst materials.

PEM imagePEM electrolysis stack (most common) materials

  • Proton exchange membrane: Nafion®
  • Electrode catalysts:
    • Anode catalyst: iridium oxide (IrO2)
    • Cathode catalyst: platinum (Pt)
  • PTL, porous transportation layers:
    • Anode: titanium (Ti)
    • Cathode: carbon paper (C), titanium (Ti)
  • Bipolar plates:
    • Anode: titanium (+ platinum coating)
    • Cathode: titanium (+ gold coating)

PEM electrolyser system components

  • Stack
  • Anode side: water purification unit, water circulation pump, ion exchange filters, heat exchanger, O2/H2O separation unit
  • Cathode side: H2/H2O separation unit, O2 removal unit from product hydrogen, drying unit
  • Power electronics (grid electricity à DC)
  • Automation system

SOEC electrolysis

SOEC electrolysis has potential to have the highest electrical efficiency compared to other electrolyser technologies. However, the technology needs to be developed further, especially regarding lifetime and costs, to reach commercialisation.

SOEC imageSOEC electrolysis stack (most common) materials

  • Electrolyte: YSZ
  • Fuel electrode: Ni + YSZ
  • Air/O2 electrode: LSC, LSM, LSCF
  • Interconnect plate: Crofer and other high-temperature ferritic stainless steels with protective coating
  • Seals: glass, glass-ceramic, mica

SOEC electrolyser system components

  • Stack
  • Steam generator
  • Air blower
  • Fuel recycling pump
  • Heat exchangers + condensers
  • Supporting structures + piping (gas and stack max. temperature 700-800 °C)
  • High temperature insulation materials
  • Power electronics + automation system

Electrolyser BoP (Balance of Plant) in general:

  • Power electronics (power source, converter AC-DC, rectifier) + automation system
  • Water purification (ion-exchange, reverse osmosis, water-gas separator)
  • Cooling system
  • Pipes and mechanical structures
  • Gas analysis equipment (gas chromatography, GC) is needed to monitor the quality and safety of the product gas. Oxygen removal unit and hydrogen dryer might be needed, depending on the application, and required hydrogen purity.
  • Compressor (often needed to reach desired pressure)
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