Air Supply Module ASM

The air supply module provides air for the fuel cell system, mainly for the cathode reaction. For air-cooled stacks with combined reaction and cooling air, the ASM is simply the fans. For air-cooled stacks with separate reaction and cooling air, the ASM consists of the fans for the reaction air and an air blower or an air compressor for the cooling air. For liquid-cooled stacks, the ASM provides the reaction air using an air blower or an air compressor. Since the ASM for liquid-cooled stacks is more complex than for air-cooled stacks, the following discussion will be about the ASM for liquid-cooled stacks. 

Schematic of air supply module. (MFT = mesh filter, FT = filter, FM = flow meter, PS = pressure sensor, HF = humidifier, TS = temperature sensor.) 

The ASM may also provide air for other purposes in accordance with the fuel cell system design. For example, it will provide the combustion air for the reformer whose temperature is typically a few hundred degrees Celsius (natural gas reformer around 900°C and methanol reformer around 250°C). The ASM may also supply air for the preferential reactor to lower the CO 

The air pressure boost ability of an air blower or an air compressor is related to the air flow rate the higher the air flow rate, the smaller the pressure boost achievable from the same blower or at the same input power. When a stack operates at the highest designed power output, the air flow rate will reach the maximum. The pressure boosted by the blower or compressor must be higher than the stack pressure drop at this air flow rate otherwise, the blower or compressor is inadequate. The user should carefully study the pressure versus flow rate characteristics offered by the manufacturer of the blowers or compressors before a selection is made. A blower or a compressor offering higher pressure boost and higher flow rate will consume more power. 

It is suggested that a user not operate a blower or a compressor near its upper limit in order to prevent it from being burned. Long-time use near the upper limit should definitely be avoided. Many blowers and compressors have temperature- or current-protection mechanisms. When the temperature or the current exceeds the preset limit, the blower or compressor will automatically shut down. 

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