Water electrolysis is the process in which water is split into hydrogen and oxygen gas through the application of an electric current. This process is a promising method for producing green hydrogen, a clean and renewable fuel that can be used in a variety of applications.
There are several different technologies that can be used for water electrolysis, each with its own set of pros and cons. We have listed 4 of them here.
PEM (Proton Exchange Membrane) electrolysis
PEM electrolysis is best suited for projects that require high-purity hydrogen and flexible operation. It is ideal for projects that rely on intermittent renewable energy sources like solar or wind, where hydrogen production must adjust quickly to changes in power availability. This makes PEM electrolysis a great choice for power-to-gas applications, grid balancing, and projects where hydrogen is stored during peak renewable generation periods and used later.
This technology is also preferred for applications where space is limited, such as in refueling stations or on-site hydrogen generation for industrial processes, because it offers compact system designs. Its ability to operate at higher current densities compared to alkaline electrolysis means it can produce hydrogen at a faster rate, making it suitable for projects that need to scale up production quickly.
PEM electrolysis is increasingly common today, particularly as the demand for green hydrogen grows in sectors like transportation, energy storage, and industrial applications. While it is not as widespread as alkaline electrolysis, its adoption is expanding due to its flexibility, high efficiency, and compatibility with renewable energy sources. The technology has gained traction in projects where the ability to respond quickly to fluctuating power inputs is crucial, and where high-purity hydrogen is needed for applications like fuel cells.
Alkaline electrolysis
Alkaline electrolysis is most suitable for large-scale hydrogen production projects where cost-effectiveness is a priority and where there is a consistent, stable power supply. It is ideal for projects that can operate continuously, such as industrial applications with steady energy sources like nuclear power plants or large-scale renewable installations with grid connections. Alkaline electrolysis is a mature, proven technology that has been in use for decades, making it a reliable choice for hydrogen production when high purity is not a critical requirement.
This technology is well-suited for applications where efficiency and durability are more important than rapid response times to fluctuating energy inputs. It performs best in scenarios where hydrogen production can run consistently without the need for frequent start-ups and shut-downs. As a result, it is commonly used in large-scale industrial projects, such as chemical plants and refineries, where it is integrated into processes requiring continuous hydrogen supply.
Alkaline electrolysis is widely used today and is one of the most common methods for producing green hydrogen globally. It remains a popular choice due to its relatively low cost, long-established technology, and high durability. Although it is not as efficient as newer technologies like PEM or SOEC under varying load conditions, its cost-effectiveness and robustness make it a go-to solution for large-scale hydrogen projects, especially in industries where stable energy input is guaranteed.
AEM (Anion Exchange Membrane) electrolysis
AEM uses an anion exchange membrane as the electrolyte. This technology is relatively new and is not yet widely used for hydrogen production. One of the main benefits of AEM is that it can operate at high efficiency and at a low cost. However, has yet to be scaled up to MW-scale projects.
AEM is best used in projects where cost efficiency and sustainability are priorities, but where extremely high hydrogen production rates or ultra-pure hydrogen aren’t essential. It is ideal for small to medium-scale hydrogen production, such as on-site generation for industrial processes, power-to-gas systems, or fuel supply for hydrogen stations. AEM technology is well-suited to projects that integrate with renewable energy sources like solar or wind, as it performs efficiently with variable power inputs.
This technology is also a practical choice for early-stage feasibility studies or pilot projects, where it allows developers to explore hydrogen production potential without the higher costs associated with other electrolyzer types. In these scenarios, AEM electrolysis provides a balanced solution between performance and cost, enabling efficient green hydrogen production with a focus on affordability.
AEM electrolysis is not yet widespread in commercial production. However, recent developments indicate a growing interest in scaling up AEM electrolysis. For instance, in March 2024, Power to Hydrogen partnered with global utility leaders to demonstrate the first industrial-scale AEM-based electrolysis stack for low-cost green hydrogen production. Additionally, the EU-funded CHANNEL project has been working on developing a novel, cost-efficient 2 kW electrolyser stack based on AEM technology to boost hydrogen generation by water electrolysis.
SOEC (Solid Oxide Electrolysis Cell) Electrolysis
The SOEC uses a solid oxide electrolyte as the electrolyte. This technology is still in the development phase and is not yet widely used for hydrogen production. One of the main benefits of SOEC is that it can operate at high efficiency and at high temperatures, which makes it well-suited for large-scale hydrogen production. SOEC systems work at high temperatures (around 700-900°C), making them highly efficient compared to other electrolysis technologies. This makes them particularly suited for industries that already generate significant amounts of waste heat, such as steel production, chemical manufacturing, or certain power plants.
It is deemed to be a promising candidate for hydrogen production where heat is abundant, such as large industrial sites and nuclear power plants. However, despite its high efficiency and potential, SOEC technology is still in the early stages of commercialization. It is less common in current production compared to established technologies like alkaline or PEM electrolysis. The main challenges holding back widespread adoption include the high costs of materials, system complexity, and durability issues related to the extreme operating temperatures.
As research advances and these technical hurdles are overcome, SOEC is expected to become more common, particularly in industries where integrating waste heat can offset some of the costs and improve overall efficiency. For now (2024), it remains largely in the pilot and demonstration phases, with limited commercial deployments focused on exploring its potential in specialized applications.
Which electrolysis technology to choose for your project
Each of the different technologies has its own set of pros and cons for green hydrogen production. PEM is efficient and safe, but it may be more expensive for large-scale projects. Alkaline is low-cost, but it is not yet as flexible as PEM. AEM has the potential to be low-cost and efficient, but is not yet widely used. SOEC has the potential to be efficient and well-suited for large-scale production, but it is still in the development phase.
We advise you to let the specifics of your project drive your choice of electrolysis solution. Always do a proper project assessment at project start to review your alternatives. Does this sound time costly and complicated? Don’t worry, we have developed a state-of-the-art software that lets you try and evaluate your options in seconds.
Our electrolyzer catalog lets you compare data on costs, hydrogen output, energy consumtion and more. If this is something that your team would benefit from, you are always welcome to book a consultation with us.
