A PEM fuel cell works with a thin polymer membrane, the proton exchange membrane, that lets hydrogen ions pass from one side to the other. On the way, the cell makes electricity, some heat and water. There is no combustion.
From one cell to a stack
One cell gives less than one volt under load. Many thin cells are stacked in series to reach a useful voltage and power. That pile of cells is the stack.
Air-cooled or liquid-cooled
In an open-cathode, air-cooled stack, a fan brings the air the cells need and carries the heat away, so there is no liquid cooling loop. This keeps the stack simple and light, which suits a few hundred watts to a few kilowatts. Large stacks for cars, buses and trains use liquid cooling.
Key figures of our stacks
Our air-cooled PEM stacks start in under a minute and run at 50 to 60 % efficiency.
See our air-cooled PEM fuel cell stacks and ask for a datasheet.
Figures from the Unconventional Energy product pages. Updated 2 November 2026.