Difference Between PEM & ALK Hydrogen Generating Tehcnology
Currently, there are alkaline hydrogen production technologies（ALK hydrogen generator） and pure water (PEM) hydrogen production technologies(PEM hydrogen generator) that have a relatively high degree of commercialization and a wide range of applications. The traditional alkaline hydrogen generator is essentially different from PEM hydrogen generator, mainly in terms of diaphragm, electrode, structure, electrolysis environment, electrical conduction, dynamic response, etc.
In terms of membrane technology, traditional alkaline hydrogen generator uses non-molecular-level microporous membranes, while PEM hydrogen production technology uses proton exchange membranes. From safety perspective, PEM hydrogen generator is relatively better, and it is easier to obtain gas with higher purity.
In terms of electrodes, PEM hydrogen production equipment is expensive because it uses more precious metals; alkaline hydrogen production equipment generally rarely uses precious metals, but if you want to obtain higher electric density or better overpotential, you may add precious metals .
In terms of electrode structure, PEM hydrogen production technology uses a zero-spacing structure, which is equivalent to reducing contact resistance; alkaline hydrogen production has a spacing structure, and there may still be some resistance between them, so the current density difference between the two sides is relatively large, and the conversion rate also has a certain difference. PEM hydrogen production system can obtain higher current density, among which the current density of commercial equipment can reach 1.5-2A/cm2; while the current density of alkaline hydrogen production technology is generally about 0.3-0.5A/cm2, then the entire equipment is in weight There will be a big difference in size and capacity.
In terms of electrolysis environment, alkaline electrolysis hydrogen generator produce hydrogen in 25%-30% lye environment. PEM electrolysis hydrogen production adopts a zero-spacing structure, so it does not require electrolyte and can be carried out in pure water. Therefore, in terms of environmental friendliness, hydrogen production by PEM electrolysis is superior to hydrogen production by alkaline electrolysis.
In terms of electrical conduction, the hydrogen production by alkaline electrolysis is mainly completed by the movement of positive and negative ions; while the hydrogen production by PEM electrolysis is basically completed by the active groups of hydrogen ions, which can basically ensure that hydrogen and oxygen are not easily interpenetrated in the environment of pure water electrolysis hydrogen production. Therefore, the purity of the hydrogen obtained by PEM electrolysis for hydrogen production is relatively high.
Hydrogen is transforming from a chemical raw material to a secondary energy source, and the degree of integration with renewable energy will be higher and higher. This is also a future development direction. After the combination of hydrogen and renewable energy, the common volatility and wide power adjustment of renewable energy have certain requirements on hydrogen production equipment, such as dynamic response rate.
At present, hydrogen production from large-scale renewable energy mostly uses alkaline electrolyzed water hydrogen production technology, and some demonstration projects use PEM electrolyzed water hydrogen production technology. This is mainly because there is a considerable gap in the cost of the two; at the same time, based on For hydrogen production from renewable energy, electricity costs account for a considerable proportion of the overall operating costs.
Therefore, in terms of calculations, alkaline hydrogen production equipment has relatively good economic indicators due to its low cost and high cost performance.
In summary, the alkaline hydrogen production technology has a higher cost performance, and the capacity of the monomer equipment is larger, which can currently reach more than 1,000 cubic meters. Large-scale hydrogen production generally uses alkaline hydrogen production technology.
PEM hydrogen production technology has better volatility adaptability, relatively higher degree of integration/coupling with renewable energy, better environmental friendliness, but higher requirements on boundary conditions, so the cost needs to be greatly reduced , thus PEM hydrogen production equipment can adapt to the future development prospects.