【Haichuan Hydrogen Energy】Bids for electrolyzers reach new highs; is an explosion in the green hydrogen sector imminent?

There are mainly four technical approaches for producing hydrogen through water electrolysis: alkaline electrolysis (ALK), proton exchange membrane electrolysis (PEM), solid oxide electrolysis (SOEC), and anion exchange membrane electrolysis (AEM). Alkaline electrolysis (ALK) is an electrolytic process that takes place in an alkaline electrolyte solution (usually KOH). OH- ions move to the anode through the membrane, where they lose electrons to produce O2. At the cathode, water gains electrons, resulting in the production of H2 and OH-. Proton exchange membrane electrolysis (PEM) is a process of electrolyzing pure water; in this process, H2O molecules are oxidized at the anode to produce oxygen and H+ ions. The H+ ions migrate across the proton exchange membrane under the influence of an electric field to the cathode, where they undergo a reduction reaction to produce hydrogen gas. Solid oxide electrolysis (SOEC) is a process in which water vapor is ionized into hydrogen ions and oxygen ions at high temperatures, resulting in the generation of hydrogen and oxygen gases at the electrodes respectively; the reaction temperature is usually above 600°C, and it is suitable for photothermal power generation systems that produce high-temperature, high-pressure steam. Anion exchange membrane electrolysis (AEM) typically uses pure water or a low-concentration alkaline solution as the electrolyte. In this process, OH- ions pass through the exchange membrane to the anode where they produce water and oxygen, while water molecules at the cathode generate OH- ions and hydrogen gas.

Comparison of processes for producing hydrogen via water electrolysis: each has its advantages. Characteristics of alkaline electrolysis (ALK): Advantages: It is the most mature technology available at present, with low equipment costs. Limitations: It involves corrosive liquids； High operation and maintenance costs ； The theoretical efficiency is lower than that of PEM, SOEC, and other approaches ； Difficult to apply with intermittent power sources? Characteristics of proton exchange membrane electrolysis (PEM): Advantages: High adaptability to intermittent power sources, easy to integrate with renewable energy sources such as wind and solar power ； Low operation and maintenance costs? Limitation: high equipment costs ； A precious metal catalyst is required. Characteristics of solid oxide electrolysis (SOEC): Advantages: Theoretical high efficiency ； Non-precious metal catalysts can be used. Limitation: reactions require high temperatures, resulting in limited application scenarios ； It is in the laboratory research and development stage and has not yet been put into industrial use. Characteristics of anion exchange membrane electrolysis (AEM): Advantages: Combines the advantages of alkaline and PEM methods; low material cost ； The electrolyte is a dilute alkaline solution or water; it has low corrosivity and does not require precious metal catalysts. Limitation: It is difficult to produce anion exchange membranes on a large scale, and they are still in the research and development stage

There are various advantages to different processes for producing hydrogen through water electrolysis. Alkaline electrolysis (ALK) is currently the most maturely developed technique, with low equipment costs; however, its theoretical efficiency is lower than that of processes such as PEM and SOEC, and it is not suitable for use with intermittent power sources. Proton exchange membrane electrolysis (PEM) has high adaptability, is easy to integrate with renewable energy sources such as wind and solar power, and has low operation and maintenance costs, although the equipment cost is relatively high. Solid oxide electrolysis (SOEC) features high theoretical efficiency and can use non-precious metal catalysts; however, as it is still in the laboratory research phase, it has not been put into industrial use. Moreover, the reaction must take place at high temperatures, which limits its applicable scenarios. Anion exchange membrane electrolysis (AEM) combines the advantages of alkaline and PEM methods: it has low material costs, uses a dilute alkaline solution or water as the electrolyte, resulting in low corrosivity, and does not require precious metal catalysts. However, it is difficult to scale up for commercial use and is still in the research and development stage. Therefore, in practical applications, it is necessary to select an appropriate electrolytic water hydrogen production process route based on specific circumstances. .

The alkaline electrolysis route is mature; PEM has strong growth potential, while SOEC and AEM offer good prospects for future development. In terms of the installed capacity of electrolyzers, alkaline electrolysis is currently the dominant approach, while PEM is growing rapidly. Alkaline electrolysis is currently the most mature approach. Based on the status of existing hydrogen projects, the IEA estimates that the total installed capacity of alkaline electrolyzers worldwide in 2022 was at least 727 MW (the technology used in some projects was not disclosed), accounting for 52% of the total installed capacity. The share of PEM electrolyzers in installed capacity continues to rise; by 2022, the total installed capacity was at least 366 MW, representing a year-on-year increase of nearly 200% ； The cumulative installed capacity in 2023 is expected to approach that of alkaline electrolyzers, exceeding 1 GW. The PEM, SOEC, and AEM solutions possess excellent potential for cost reduction and efficiency improvement. Increasing the current density is a key factor in reducing the unit investment cost of electrolyzer equipment, but an increase in current density usually comes with an increase in electrolyzer voltage, which in turn leads to a decrease in electrolysis efficiency. As shown in the figure at the lower right, PEM and SOEC solutions can achieve higher current densities and lower voltages, offering great potential for cost reduction and improved efficiency; they have the potential to replace existing technologies once they become more mature. Furthermore, the theoretical efficiency of the AEM route, which is currently in the research and development stage, is similar to that of PEM; it does not require precious metal catalysts, resulting in low raw material costs. If industrialization is achieved, it holds great potential for cost reduction and widespread adoption.

Yes, in terms of the installed capacity of electrolyzers, the alkaline electrolysis route is currently the mainstream approach; it is highly mature and has a wide range of application areas. The PEM electrolysis route, on the other hand, shows strong growth potential; its share in installations is increasing continuously, and it is expected to reach or even exceed the installation scale of alkaline electrolysis in the future. Furthermore, although the SOEC and AEM solutions are still in a relatively early stage of development, they hold great potential for reducing costs and increasing efficiency; they are expected to become effective alternatives to alkaline and PEM electrolysis as these technologies mature in the future. Therefore, in the long term, each of these electrolysis approaches has its own advantages and potential, allowing for a choice based on specific application requirements. .