Hydrogen drones – renewable powered UAVs
It is currently impractical to power unmanned aerial vehicles (UAVs) with battery technology alone, as the battery required to improve flight times would be so large and heavy that it would severely limit cargo capacity and range.
A promising alternative power source is hydrogen. Compared to a lithium ion battery, a hydrogen fuel cell has a much higher energy density and a better lifetime durability. Additional benefits of hydrogen drones include quick refuel times and carbon neutrality.
Technological challenges and solutions
Over recent years, the use of hydrogen within the aviation sector has grown rapidly with continuous improvements by companies like Doosan, Intelligent Energy, Plug Power, and Hypower Lab. While technological advances include increases in things like drone carrying capacity and flight time, there are still several challenges to overcome.
Hydrogen storage and transportation
Hydrogen fuel is becoming more widespread globally, necessitating effective storage and transportation methods. Most fuel cell drones store hydrogen in its pure form, conveniently eliminating the need for a conversion step. There are, however, a few challenges that accompany the storage of pure hydrogen: it is prone to leaking; it needs to be stored at high pressures and/or low temperatures; and it is volatile.
While these problems are faced by the entire hydrogen economy, they become particularly difficult when trying to attach hydrogen storage to an aerial vehicle with movement, altitude, temperature, and weather to contend with. Fortunately there are also many solutions under development as hydrogen storage and transport are crucial to all sectors of the hydrogen economy.
The record for the longest flight duration of a purely hydrogen powered RC drone is just over 12 hours, quite an impressive feat as the previous record for a battery-powered rotorcraft was only about two hours.
Several agencies are seeking ways to improve the travel range of hydrogen powered UAVs. One example is the U.S. Naval Research Laboratory, which produced a UAV capable of staying in the air for over 24 hours by using a combination of hydrogen and solar technologies.
There are also application-specific challenges that hydrogen drones must overcome if they are to become more widespread. For example, in applications requiring the navigation of built-up areas or travel between ships at sea, a drone must be capable of vertical take-off. Traditional quadcopter drones are suitable for such applications, however these have limited speeds and do not travel longer distances efficiently.
To achieve longer range flight, a more classic airplane-style design is needed – although this then limits the ability for the vehicle to take off! Researchers at TU Delft in the Netherlands have been working on a UAV design that combines these two concepts. Their drone is designed to cover large distances and to take off and land vertically, making it ideal for travelling long distances between ships.
The drone uses a hydrogen-battery hybrid system and 12 motors spread across a dual wing design to achieve flight times of 3.5 hours. The drone was also specifically designed to deal with the turbulent conditions of the open sea for transport between ships, with the bonus of being carbon neutral.
Other uses for hydrogen drones
Increased flight time make the drones increasingly useful for gathering aerial data across large areas in agriculture, forestry, powerline inspection, and search and rescue applications. As UAV capabilities and efficiencies increase, their carrying capacities also increase, making them ideal for conducting fast, unmanned deliveries of medical supplies and humanitarian aid. Such drones will be particularly valuable in applications in remote and hard to reach locations.
Like the rest of the hydrogen economy, hydrogen drones remain an emerging and continually evolving technology. The advantages of such technologies and the speed at which they are developing means they will no doubt become more commonplace in many industries over the coming years to gather information, better connect regions, and help achieve carbon neutrality.