Fuel Cells for Drones & UAV

Find suppliers and manufacturers of Fuel Cell Systems and Hydrogen Fuel Cell Technology for Drones, UAV, UAS and unmanned vehicles
Overview Fuel Cells for Drones & UAV
By Technology Editor Last updated: December 30th, 2021

Fuel Cell Systems for Autonomous Vehicles

What are Fuel Cells?

Intelligent Energy Fuel Cell

Intelligent Energy Fuel Cell

Drone fuel cells are electrochemical devices that convert chemical energy from fuels and oxidisers, without combustion, into useful electrical energy that can be used to power devices and vehicles. The cell itself does not require charging, but does require a steady flow of fuel and oxidiser.

Hydrogen is the most common fuel, with oxygen from the air being the most common oxidiser.

Multiple fuel cell technologies exist, including proton-exchange membrane (PEM), solid acid, and solid oxide. PEM is the most widely-used electrochemical cell used  in drones as it has the highest power density. PEM cells also run at lower temperatures, making their construction and engineering less complex and costly, and giving them a lower thermal signature.

PEM Hydrogen Fuel Cells for Drones

PEM fuel cells are based around a positive terminal and a negative terminal separated by a solid polymer membrane.

The hydrogen fuel is fed to the negative terminal, where the hydrogen atoms are stripped of their electrons to become protons. The protons permeate through the membrane to the positive terminal. The electrons travel to the positive terminal via an external route, and this flow of current provides the useful electrical output of the cell.

Oxygen from the air is fed to the positive terminal and combines with the protons and electrons from the hydrogen to form water. Because water is the only by-product of the process, they are highly favourable from an environmental and emissions standpoint.

PEM Hydrogen Fuel CellsNorthwest UAV’s PEM Hydrogen Fuel Cells

Hydrogen Vs Batteries & Combustion Engines

Hydrogen powered drones have a number of advantages over those powered by batteries and internal combustion engines. Drone fuel cells have a high energy density, meaning that they provide a greater energy output to mass ratio, which is particularly important for aviation and unmanned aerial vehicles. Hydrogen PEM fuel cells have provided up to three times the endurance at equivalent aircraft/payload weights compared to drone battery systems.

In addition to having a relatively low energy density, batteries take a long time to recharge, with a charge cycle often being many times the typical half-hour flight endurance that they provide. Hydrogen cylinders can be swapped out within minutes, allowing for greater operational efficiency.

Fuel cell technology is quiet compared to internal combustion engines, the noise and vibration from which can affect the operation of UAV sensors and payloads. Internal combustion engines also require more maintenance and typically have a much lower MTBF (Mean Time Between Failures) than alternative fuels, requiring more spare parts and more manpower.

800W Drone Fuel Cell Power Module

Intelligent Energy 800W Drone Fuel Cell Power Module

Hydrogen powered drones are more efficient at higher altitudes than many with internal combustion engines, which suffer more from derating due to the lower air density. Small internal combustion engines function at peak fuel efficiency only within a narrow band of conditions, and are also noisy and polluting with a high thermal signature.

Hydrogen Powered Drones

Hydrogen cells can be stacked in a modular fashion depending on the output voltage required. A complete hydrogen drone fuel cell power system will additionally incorporate control systems for fuel and air, as well as hydrogen regulators and liquid or air cooling systems.

Although they feature a high energy density, hydrogen cells exhibit a relatively low power density, which translates to a low thrust to weight ratio for drones and other aircraft. This means that current electrochemical cells are not applicable to the largest UAVs, which require very high peak output power and thus are better served by traditional combustion engine technology.

sUAS are also currently unable to take advantage of fuel cell technology due to the weight required and the lack of usable space on the aircraft. These drones, which tend to be used for shorter missions, are better served by battery technology.

Small-to-medium sized UAVs are thus the main current target market for PEM hydrogen fuel cell systems. Hybridized systems can also be fitted, these pair hydrogen cells with a small battery that provides extra power during high-demand phases of flight such as take-off, rapid climbing and high wind resistance, thus offsetting the aforementioned low power density disadvantage. The hybrid battery can be recharged during periods of low demand.

Designed for reliable operation even in extreme environments, drone fuel cell systems can enhance mission endurance and range, potentially enabling increased efficiency for BVLOS (beyond visual line of sight), ISR (intelligence, surveillance and reconnaissance) and long-range mapping and surveying UAS missions.

Hydrogen drone fuel cell systems have successfully been flown aboard a variety of fixed-wing and multirotor platforms, including leading-edge unmanned aerial systems by Insitu, Aerovironment and Lockheed-Martin.

UAV Hydrogen Fuel Cell Module by Intelligent Energy

Fuel Cell Systems: Frequently Asked Questions

Hydrogen fuel cells are electrochemical devices that use hydrogen as fuel, with an oxidiser, to convert chemical energy into useful electrical energy.

Hydrogen cells are made up of a positive and a negative terminal, with an electrolyte separating them. An oxidation reaction turns the hydrogen into positively charged ions and negatively charged electrons, creating an electric current.

A proton exchange membrane (PEM) fuel cell uses a proton-conducting polymer membrane to separate the two sides of the cell.

Hydrogen is fed to the negative terminal, and splits into protons and electrons. The flow of electrons creates useful electric current. At the positive terminal the protons and electrons from the hydrogen combine with oxygen to form water, the only by-product of the cell.

Hydrogen fuel cells have a higher energy density than batteries, meaning that they can provide more energy per unit weight carried, leading to greater flight endurance.