A hydrogen fuel cell produces electricity from hydrogen and oxygen from the air, with water and heat as the only by-products. On a drone it replaces or supplements the battery, keeping the simplicity of electric propulsion while storing much more energy per kilogram, which multiplies endurance.
How a fuel cell system is built
Fuel cell stack: almost always PEM (proton exchange membrane) for aircraft, for its low operating temperature and quick start.
Balance of plant: air supply, cooling, humidity control and power electronics.
Hydrogen storage: usually compressed gas in composite cylinders; liquid hydrogen and chemical storage are used in some designs.
Hybrid battery: a small battery covers power peaks during take-off and climb while the stack supplies cruise power.
Key specifications
Continuous electrical power of the system, and the peak the hybrid battery adds.
System mass with and without the hydrogen tank.
Hydrogen consumption at rated power, which sets endurance with a given tank.
Cooling: air-cooled stacks are simpler for small drones; liquid cooling is used at higher power.
Operating range: ambient temperature and altitude.
Refuelling logistics: cylinder swap or refilling, and the availability of hydrogen at the operating site.
When fuel cells make sense
Fuel cells pay off on missions longer than a battery can sustain, such as pipeline and power-line inspection, mapping of large areas or persistent surveillance, where noise and emissions also matter. The cost and logistics of hydrogen are the main barriers.
How much longer can a fuel cell drone fly than a battery drone?
It depends on the mission and the tank, but hydrogen systems commonly give several times the endurance of a battery-only drone of the same take-off mass, because hydrogen stores much more energy per kilogram.
Why do fuel cell drones still carry a battery?
The fuel cell responds relatively slowly to sudden power demands and is sized for cruise. A small battery covers take-off, climb and manoeuvres, and keeps the drone powered if the stack stops.
How is hydrogen stored on a drone?
Most systems use compressed hydrogen in lightweight composite cylinders. Liquid hydrogen offers more energy per kilogram but needs cryogenic tanks, and is used mainly on larger aircraft.
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