A PEM fuel cell stack is the part of a fuel cell that makes the electricity: a pile of thin cells that turn hydrogen and air into electricity, heat and water. Unconventional Energy designs and makes light, air-cooled PEM fuel cell stacks from 500 W to 4.8 kW. They need only a hydrogen feed and a fan, and we build them into drones, robots, light vehicles and backup power.
Three short steps, about one minute. We reply the same working day.
Updated 22 October 2026
Under load, one fuel cell gives less than one volt, so many thin cells are stacked in series to reach a useful voltage and power. That pile of cells is the stack. A complete fuel cell system adds what the stack needs to run: the hydrogen supply, the air supply, the control electronics and often a battery for load peaks. We make both.
A thin polymer membrane lets hydrogen ions pass from one side to the other. The result is electricity, some heat and water. There is no combustion.
Our stacks are open-cathode and air-cooled. A fan brings the air the cells need and carries the heat away, so there is no liquid cooling loop.
The stack is the part you build into your own product, when you have the engineers to design the system around it.
A complete system is a power unit you connect to your load. We supply systems from 1 kW upwards for drones and backup power.
Air cooling keeps the stack simple and light, which suits the power class from a few hundred watts to a few kilowatts. Large stacks for cars, buses and trains use liquid cooling instead.
We make stacks for two kinds of buyers: OEM stacks for integrators who build their own systems, and aero stacks for drone platforms. Each model has its own datasheet with voltage, current, weight and size.
| Item | Our stacks |
|---|---|
| Type | Open-cathode, air-cooled PEM fuel cell stack |
| Power per stack | 500 W to 4.8 kW |
| Start-up | Under a minute |
| Efficiency | 50 to 60 % |
| Operating temperature | Low operating temperature |
| What it needs to run | A hydrogen feed and a fan |
| Product lines | OEM stacks for integrators. Aero stacks for UAV platforms |
| Cell generation | Gen 5 in production. Gen 7 to 8 in development |
| Complete systems | From 1 kW upwards, modular. Hybrid with batteries or supercapacitors |
| Cold weather | Full performance down to −20 °C at system level. Values per product from our engineers |
| Made in | Designed and made in the EU. Over 96 % EU content, no critical components from outside the EU |
| Voltage, current, weight, size | On the datasheet of each model. Ask for a datasheet |
Figures from the Unconventional Energy product range, October 2026. A stack's real output depends on the system around it, so our engineers confirm the figures for your use.
A stack alone does not run. It needs hydrogen at the right pressure, air from the fan, electronics that match its voltage to your load, and often a battery for peaks. You can design this yourself, or we can do it with you.
For integrators who build their own power systems.
For buyers who want a power unit they can connect to their load.
We fit the fuel cell into your product and help carry it through the approvals it needs.
We supply stacks and systems to equipment makers and do not compete with them with drones or vehicles of our own.
Our stacks come from the work of Pragma Industries, the French fuel cell pioneer founded in 2004 in the French Basque Country. Pragma developed and produced cell generations 1 to 6. In 2026 its technology, patents and team became part of the Forking Future consortium. Cell chemistry and stack design continue in Bayonne, France, as Unconventional Energy SAS. About Unconventional Energy.
It is a pile of thin fuel cells connected in series. Each cell has a proton exchange membrane (PEM) that turns hydrogen and oxygen from the air into electricity, heat and water. Stacking the cells adds up their voltage, so the stack can power real equipment.
Unconventional Energy is one of them. We design and make air-cooled PEM fuel cell stacks from 500 W to 4.8 kW, with stack design and production in France. Our work builds on Pragma Industries, the French fuel cell pioneer founded in 2004.
The stack makes the electricity. The system adds what the stack needs to run: the hydrogen supply, the fan, the control electronics and often a battery. Buy a stack if you design the system yourself. Buy a system if you want a power unit that is ready to connect.
An air-cooled, open-cathode stack uses a fan for both the air supply and the cooling. That makes it simpler and lighter, which suits drones, robots and small power units. Liquid cooling is used in large stacks of tens of kilowatts, such as those in cars and buses.
Our stacks start in under a minute.
Yes. Each model has a datasheet with voltage, current, weight and size. Tell us your power need and your application in the form below, and we send the right one.
About 98 % of the system mass is reusable. Our fuel cells also use about 1/1000 of the critical raw materials of a lithium battery. For the end-of-life handling of a specific product, ask our engineers.
Building a product around a fuel cell? Tell us the power, the application and the volumes. We send the datasheet that fits, and our engineers help you choose between a stack and a complete system.
Prefer email? info [at] unco.tech