Why Do Air-Cooled Fuel Cells Have Shorter Lifespans Than Water-Cooled Ones?

In fuel cell technology, the choice of cooling system not only affects heat dissipation efficiency but also directly determines the core lifespan of the stack. Behind the two mainstream cooling approaches—air cooling and liquid cooling—lie “genetic-level” differences that impact stack durability.

In terms of cooling media, what are the differences between air-cooled and water-cooled fuel cells ?

Air-cooled systems rely on air as the cooling medium. Air has a low specific heat capacity, meaning it has a limited ability to carry heat. In actual operation, localized hot spots can easily form within the fuel cell stack. This uneven temperature distribution not only compromises performance but also accelerates material degradation—the chemical degradation rate of the proton exchange membrane and catalyst layers increases exponentially at high temperatures. Liquid-cooled systems utilize coolants with higher specific heat capacities (typically a mixture of deionized water and ethylene glycol).It's like building a highly efficient "heat highway" for the fuel cell stack, which can uniformly and quickly remove the heat of reaction, keeping the fuel cell stack operating in the optimal and most uniform temperature window, fundamentally slowing down the aging process of the materials.

In terms of control logic, what are the differences between air-cooled and liquid-cooled fuel cells ?

Air-cooled systems face a fundamental trade-off: the same airflow serves both gas delivery (oxygen for chemical reactions) and cooling. To dissipate heat, it may be necessary to increase the airflow, but this will blow away the moisture necessary for the membrane electrode, causing the membrane to dry out; to retain water, heat dissipation may be sacrificed, leading to overheating. This fragility of the hydrothermal balance keeps the fuel cell stack in a state of "stress" for a long time.   But the liquid cooling system achieves perfect functional decoupling: the airflow path is dedicated to air supply, and the coolant path is dedicated to temperature control. Both are independently optimized through the control system, ensuring the fuel cell stack always operates at its optimal temperature and humidity "sweet spot." This stable and controllable internal environment is the foundation for its long lifespan.

In terms of operating condition response, what are the differences between air-cooled and liquid-cooled fuel cells ?

Air-cooled stacks often exhibit “self-accelerating” power output characteristics: increased load → heightened heat generation → higher airflow required for cooling → membrane electrode assembly drying → increased internal resistance → more waste heat. This creates an unstable positive feedback loop. More critically, the resulting frequent, extreme wet-dry cycles subject the catalyst layer, gas diffusion layer, and membrane to immense mechanical stress, leading to physical damage like delamination and cracking. Liquid cooling systems achieve active, smooth power regulation through external pumps and closed-loop control. Coolant flow and temperature respond precisely and rapidly to load changes, minimizing fluctuations in the stack's internal state. Reduced thermal expansion/contraction and wet-dry cycling naturally enhance the durability of material structures.

In terms of living environment, what are the differences between air-cooled and liquid-cooled fuel cells ?

Air cooling means that the cathode (air electrode) of the fuel cell stack is directly exposed to the environment. Airborne contaminants such as dust, salt, and sulfides can easily penetrate and directly adhere to and poison the expensive platinum catalyst, clogging the pores of the gas diffusion layer. This catalyst layer contamination is one of the main causes of irreversible performance degradation. Liquid cooling systems, on the other hand, typically have their cathode air intake rigorously filtered, and the entire fuel cell stack is housed in a relatively enclosed casing, providing "cleanroom" level protection for the catalyst layer and significantly slowing down performance degradation caused by contamination.

In short, air-cooled fuel cells resemble gifted “sprinters” requiring harsh environments: simple in structure, quick to start, and low-cost. They suit lightweight, intermittent applications with relatively low lifespan demands, such as drones and low-speed vehicles. Liquid-cooled fuel cells, however, are the “endurance champions” built for marathons. Through more complex and sophisticated systems, they prioritize long-term stability. Their focus is on durability, making them a key choice for mainstream applications like passenger vehicles, commercial trucks, and stationary power generation.