The rise of the global demand for green hydrogen is mostly fueled by the industrial sector. Last year, this demand nearly crossed the 100 Mt line and could reach 585 Mt by 2050. Green hydrogen splits water molecules, separating hydrogen from oxygen, using electrolysers. Since its byproduct is just oxygen, green hydrogen production has become vital to sustain both the industrial growth and the global energy transition.
Recent developments in electrolysis technologies have improved the efficiency of this process, and the same result can be achieved through different technologies.
Learn more about the best and newest technologies here.
Main types of electrolysers for industrial hydrogen production
Alkaline Electrolysis (AEL)
This method uses an alkaline electrolyte liquid, typically with sodium hydroxide (NaOH) and potassium hydroxide (KOH) working as ion conductors. This solution also passes through a diaphragm separator and is recombined. Then, a current passes through the electrolytes, splitting oxygen from hydrogen.
AEL dominates the hydrogen production market, mostly because it is cost-efficient and can be easily scaled. Besides, this process has considerable tolerance to water impurities, so it’s easier to find water supplies. Compared to other options, alkaline electrolysers also have a longer lifespan.
However, AEL is considered less efficient than new methods, especially compared to PEM. Alkaline electrolysis is also slower in responding to fluctuations in the electrical load, which can be problematic when dealing with renewable sources like solar or wind power, for instance. Additionally, there’s the risk of gas crossover, which happens when oxygen and hydrogen mix in the diaphragm, impacting its safety.
This method suits large-scale hydrogen production for industries like energy, steel, and chemicals, requiring high-purity hydrogen.
Proton Exchange Membrane (PEM) Electrolysis
PEM electrolysers are based on solid polymer membrane to separate oxygen and hydrogen ions from oxidised water, directing them to the cathode. Then, electrons and protons are combined to form hydrogen gas. PEM is considered a highly efficient method, given its high-pressure hydrogen output, which also requires less storage space.
The compact design is also considered key advantage for industrial use. Moreover, this method can deliver 99.99% purity in its hydrogen output at 30-40 bar (targeting 180 for the future) Researchers have also been working on the scalability issue, one of the biggest challenges of PEM electrolysis.
However, there are other disadvantages. For instance, it requires precious metals like iridium and platinum, considerably raising initial costs, especially compared to AEL. Indeed, the high cost of such metals can also hinder scalability. Moreover, the solid polymer membrane may also require special technologies to prevent degradation and hydrogen-oxygen crossover, making this option even more expensive.
Still, it’s an excellent option when high-purity hydrogen output is required. It’s a very responsive system which allows for great flexibility in production. Given their compact design, PEM electrolysers can be easily transported and relocated when necessary.
Solid Oxide Electrolysis (SOEC)
In this process, both hydrogen and oxygen are produced using steam and electricity. A ceramic electrolyte conducts oxygen ions from the solid electrolyte to the anode, recombining later into oxygen gas. SOEC operates at high temperatures, typically between 700ºC and 1000ºC, to ensure efficiency and quite surprisingly, reduce energy costs. As it turns out, using steam in the process reduces the reversible potential, which is impossible at lower temperatures.
This method can be highly efficient when using heat from other processes that would otherwise be wasted. SOEC technology allows industries to harness power from existing heat sources and use it to increase green hydrogen output. Compared to other technologies, SOEC requires considerably less energy to operate, which makes it a cost-effective option.
Since high temperature is a basic requirement for SOEC, it may not be a suitable option for industries that don’t produce waste heat. While it reduces energy costs, the material costs of setting up a SOEC system can be quite high. The operation under high temperatures also leads to quicker wear and tear of parts, which often require special materials and manufacturing processes for greater durability. Still, maintenance may be costlier than other methods.
Anion Exchange Membrane (AEM) Electrolysis (Emerging Technology)
AEM electrolysis splits water molecules by conducting OH- (hydroxide ions) through a semi-permeable alkaline membrane. Despite using a membrane, the process is closer to AEL than PEM since it requires an alkaline environment. Moreover, the metal catalysts required for AEM are much more affordable than those used in AEL. This technology produces green hydrogen with reduced environmental impact. It’s also suitable for operating with differential pressures and high current densities.
AEM is a low-cost option for PEM electrolysers, as they don’t require rare metals to work. Still, this technology delivers high-purity hydrogen just like PEM, improving its cost-effectiveness.
AEM is a very promising technology, but it’s in the development stage. Membrane durability and stability are still problematic, potentially reducing efficiency. They rely on high-performance, PGM-free electrodes, which can also be expensive. The alkaline electrolyte is vulnerable to contamination and gas crossover, potentially compromising the entire production.
| Type | Pros | Cons |
|---|---|---|
| AEL | Longer lifespan; tolerates impurities | Slower responses to eventual fluctuations; risk of gas crossover |
| PEM | High-purity hydrogen production, compact design | Requires rare metals; limited scalability |
| SOEC | Can be integrated with industrial waste heat sources; high efficiency | Quicker material degradation; requires high temperatures for optimal performance |
| AEM | Promising technology, more affordable than PEM | Still being developed; durability and stability issues |
Key factors in choosing the right electrolysis technology
Electrolysers aren’t cheap and can enormously impact energy bills, operational costs, long-term performance, and carbon footprint. That’s why they must be chosen with care, according to the specific needs of each industry, considering factors like whether the facility is powered by renewable or grid electricity.
Notwithstanding the selected technology, FRIEM can deliver the most suitable Power Supply Unit, assuring long-term reliability and high performances.