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What is the influence of the altitude on the efficency of a fuel cell?
Posted by Patrick Beaumier on January 20, 2023 at 18:04What is the influence of the altitude on the efficency of a fuel cell.
I am looking for engineering performance curves power vs altitude (range 05000m)
Nominal FC power 100kw at sea level.
Stanislaw Kowalik replied 1 year, 2 months ago 4 Members · 5 Replies 
5 Replies

As the partial pressure of oxygen decreases with increasing altitude, the performance of a fuel cell will decrease. To counteract this, must compress the air from the low ambient pressure to the proper operating pressure of the fuel cell. The penalty is that parasitic load for compression will increase so net power will still be lower than at sea level. Most automotive applications are designed for up to 4000 meters, but for aircraft applications (11,000+ m) other designs are required. For space applications, pure oxygen is used instead of air and stored cryogenically so the system is independent of ambient conditions.

The influence is significant. Additionally to the impact on the stack as Roger correctly described, the cooling system decreases in efficiency, also for the electronics. Out of practical experience I can say that we reduced the max power output of a 100kW stationary system to 80kW at 1.700m above sea level. Our calculations resulted at 87kW, but we wanted to guarantee a stable operation, which we did for several years.

Previous replies clearly show efficiency of the air supply system is of high importance. This can be improved by using purposedesigned centrifugal electric compressor, however that’s still expensive option.
Systems working with high stack inlet pressure (like 2.5 bar) can benefit from electric turbocharger, power draw from the compressor can be reduced by 2030%. Exact number depends primarily on pressure drop across the stack.
Couple of years back I developed fuel cell air supply system for highaltitude (>18km) drone. Principles are the same, although implementation was more complex. High altitude require much higher pressure ratio (in our case it was over 30), system has to work from zero to max altitude, interstage cooling for needed, power consumption was significant (of course), electronics has to prepared to work at altitude, etc. Although, at the heart of the system was technology derived from automotive.
If you are looking for more details, drop me a message, please.

Stanislaw Kowalik @DIYEngineering – a pressure ratio of 30! Wow! Yes, for 18 km you need to go from basically no partial pressure to full cathode pressure. I have dealt with pressure ratios of ~9 (also with automotive components), but 30 is quite challenging! Sounds like it was a very interesting project.

It was. Pity main investor walked away after completing demonstrator phase.
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