Pem Electrolysis System

● It doesn't necessitate the use of electrolytes. This means that purified water can be employed, marking a significant benefit.

PEM electrolysis can operate over a range of current densities. Typically, the current density in PEM electrolysis systems can vary from as low as 0.2 A/cm² to as high as 2 A/cm² or more, depending on the specific design and operating conditions of the PEM electrolyzer. The capacity (current density) significantly influences the size of the electrolyzer and therefore PEM electrolysis generally offers a more compact footprint compared to pressurized alkaline water electrolysis, making it advantageous for applications where space efficiency is a key consideration.

● Another big benefit is also PEM's ability to swiftly adapt to variable power levels within seconds.
Maintaining an overpotential voltage degradation rate below 100 mV/year is a common target for PEM electrolysis systems. However, it's essential to recognize that the actual degradation rate can vary depending on operational factors and maintenance practices. The construction and quality of the electrolyzer, which are determined by the original manufacturer, play a crucial role in influencing degradation rates. Therefore, it's advisable to consult with your electrolyzer manufacturer for specific information on expected degradation rates and recommended maintenance procedures.

● PEM is a solid polymer electrolyte membrane. The two sides of the membrane can withstand a large pressure difference, and only have a unidirectional conduction effect on hydrogen ions. It can directly separate the reactant hydrogen and oxygen to avoid cross-gassing, and has good safety. , The product gas has high purity. For alkaline electrolysis, a liquid electrolytic cell is used, and the porous asbestos cloth becomes a diaphragm by impregnation. Therefore, a strict pressure difference control system must be installed to ensure that no air leakage occurs in the anode and cathode reaction chambers and avoid safety accidents.

● The PEM electrolyte membrane can be less than 200μm, the electrode spacing is small, it can reduce the working voltage and energy consumption, and make the structure of the electrolytic cell more compact.

● Water is both a reactant and a cooling medium, eliminating the need for a cooling system and reducing the volume and weight of the device. Because the PEM electrolytic cell uses pure water as the electrolyte, the corrosion of the electrolyte to the tank body is avoided, the reaction product does not contain alkali mist, and the gas purity is higher.

Alkaline electrolyzers may seem like the most affordable option - after all, alkaline has been around for decades longer than PEM. However, progressions in PEM technology have changed its cost.

An analysis of both types of electrolyzers shows that the stack cost of an alkaline electrolyzer is lower than PEM. But when it comes to the complexity and cost of balance of plant (BOP) as the system size increases, PEM is lower, according to the Fraunhofer Institute for Solar Energy Systems ISE. In fact, the total cost of ownership of a PEM electrolyzer is lower than alkaline with forecasters estimating that PEM service costs are one-third of alkaline.

When scaling an electrolyzer, PEM has significant cost advantages in balance of plant economics. On a per-kilowatt basis, the capital expenditure associated with an alkaline electrolyzer increases significantly as the system scales. With PEM, there are options for streamlining BOP to minimize upfront cost in larger systems above 10 megawatts.

When considering output pressure, standard alkaline electrolyzers deliver output at a low pressure of 1 to 10 bar, which is a nearly ambient pressure. For most applications, hydrogen must be further compressed for transport, storage, or consumption. On the flip side, PEM electrolyzers have an output of 40 bar - that's 4 to 40 times of a typical alkaline system.

Pressure is generated by the electrochemical process in the stack, meaning PEM avoids first stage compression to bring it up to 40 bar, and bypasses the energy costs associated with compressor operation.

Alkaline's caustic electrolyte solution can also ratchet up its hefty price tag. For example, a 10 to 20-year-project means a long term need to replace parts such as pumps and valves, or the removal of potassium hydroxide from the hydrogen or oxygen streams. The 3.5 ton per megawatt requirement for highly-corrosive potassium hydroxide in alkaline systems typically incur significant space requirements – often two to three times the space of PEM system for a similar output. Any losses in space can lead to losses in revenue.