Operators of drones are increasingly demanding drones with enhanced range and flight endurance capabilities, in order to fly further and for longer durations. However, nowadays small commercially available drones are usually able to achieve a flight time of 25 minutes or less, depending on the number of rotors and/or load, with their battery power pack. It is a fact that conventional LiPo batteries with a short life and long charging time requirements have been limiting the flight duration of drones and hence have somehow slowed down the development of the Drone Industry. It is worth noting that every industry currently using drones could benefit from having a drone that can stay in flight longer. The drones are currently widely used in a variety of industries including the military, security (providing persistent intelligence and situational awareness for protection of airports, borders, ports and valuable assets), the oil and gas industry, building inspections, agriculture, rescue missions, and emergency service. In order to overcome the problem of short flight duration (when it runs on batteries) a number of manufacturers in the U.S., Europe, Russia and China have started to use fuel cells in their drone systems.
The main advantage of fuel cells over lithium batteries (such as Lithium Ion and Lithium Polymer [LiPo]) is the fact that they can keep a drone in the air a lot longer than lithium batteries. Fuel cells are three times more energy-dense than a conventional drone battery. Internal combustion engines provide much higher energy densities than batteries, but suffer from a much higher initial cost, as well as requiring extensive regular maintenance and overhaul. They are also noisy. Fuel cells are more efficient than internal combustion engines, and unlike batteries, do not need recharging and will continue to operate as long as they are provided with fuel. Improvements to lithium batteries, which are possible with new materials, will make this type of batteries more efficient, however, if we consider the achieved increase in the energy density of today’s LiPo to the equivalent product during last decade we would see just a steady improvement of about 7% a year, which is definitely not a revolution, but a slow evolution. Moreover, the Lithium-ion (Li-Ion) batteries are highly flammable, so a crash landing could trigger an explosion and contrary to internal combustion engines fuel cells do not have moving parts, which dramatically decrease noise and maintenance costs as well as unit replacement. So, fuel cells still stand as an attractive alternative to LiPo or other power options, like internal combustion engines for drones and UAVs. However, drones fitted with a hydrogen fuel cell still have an auxiliary lithium battery which starts the fuel cell and provides a backup source of power for the drone.
Every fuel cell requires two components; the main body of the power-generating unit and the fuel tank to be filled by hydrogen or any other gas or liquid. As the most abundant chemical substance on Earth, hydrogen has been used for fuel in fuel cells onboard drones since mid 2010s. Thanks to their greater energy density than LiPo batteries hydrogen fuel cells are a better fit for long-endurance flights than batteries. Hydrogen drones have a higher endurance which is much longer than drones powered by LiPo batteries.
How do hydrogen fuel cells work?
According to open sources hydrogen generates three times as much power per kilogram compared to fossil fuels - approximately 39.0 Kilowatt hours (kWh) per kilogram compared with roughly 13 kWh per kg for kerosene or petrol or just 0.2 kWh for conventional lithium ion batteries.
To turn hydrogen (H2) into fuel, it must be separated from other elements, pressurized, and stored in a stable environment (either in the pressure cylinder, in an aluminum hydrogen reactor or in a solid, lightweight hydrogen storage material, which is capable of releasing large quantities of hydrogen when gently heated, without proper storage it could explode). To make this concrete, a hydrogen fuel cell converts hydrogen fuel into electricity by combining hydrogen (H2) with oxygen (O) within the fuel cell. The only exhaust emission of this reaction is water vapor (H2O).
Though hydrogen gas is widely available from industrial gas suppliers and hydrogen fuel cells are three times more energy-dense (which means the same weight can generate more power) than a conventional LiPo drone battery, using hydrogen for fuel also has some drawbacks. Such as; since hydrogen gas wants to move around this makes it so explosive and hydrogen fuel cells generate a high amount of heat, which is high enough to melt the plastic components used in commercial drones. The cost of producing hydrogen gas still stands as a major obstacle to affordable hydrogen technologies. Several technology companies around the globe (such as Intelligent Energy, Ballard Power Systems, Cella Energy, Arcola Energy, BMPower, Doosan Mobility Innovations, Scottish Association for Marine Science (SAMS), Horizon Energy Systems (HES), and H2Go Power) have been working to develop affordable and cost-effective hydrogen technologies for drones and UAV applications since the last decade.
Despite these drawbacks, there are also some big benefits to use hydrogen fuel cells to power a drone:
• Extended mission time and distance (usually about 3x that of LiPo batteries for the same weight)
• Hydrogen is directly proportionate to the requirements of flight time. In other words, more fuel, more weight, hence more time in the air
• Compared to batteries and internal combustion engines hydrogen fuel cells provide quiet, reliable and low-maintenance operation
• More efficient operation at higher altitudes than internal combustion engines and LiPo batteries
• Lithium batteries efficiency decreases colder environments. The flight endurance reduced in an estimate from 20% to 40% of the standard time after the temperature reaches zero degrees or lower respectively. Fuel cell, however, is not affected by low temperatures. It even functions seamlessly at -20°C
• Cleaner fuel source than LiPo and other alternatives
• Time to re-charge is dramatically reduced—usually takes about five minutes (Once the hydrogen gas on board the drone is exhausted, the pressure cylinder can be re-filled in as little as two minutes, or replaced with an another, full cylinder)
• Opens up BVLOS (beyond-visual-line-of-sight) possibilities for unmanned aircraft
Hydrogen powered drones on the market
Hydrogen Powered Drones (HDPs) are drones that use hydrogen as a power source. Representing a major breakthrough in the drone market and creating a new era for drones and UAVs the hydrogen fuel cell is a new technology that many drone companies are adopting. The world’s first hydrogen-fueled aircraft (Raptor E1 drone) took to the skies in January 2015 and the first commercial and ready-for-market HPD in the world (HyDrone 1550, designed and manufactured by Chinese-based MicroMultiCopter [MMC] Aero Technology) was released in 2016. Since then, more hydrogen-fueled drones and hydrogen fuel cells made for drones have been released, with newer models achieving greater and greater enhancements.
On January 19, 2015, the Scottish Association for Marine Science (SAMS) completed its first test flight with the Raptor E1 drone (of Raptor UAS company) by using Cella Energy’s hydrogen-based power system (gas generator). The test flight lasted for 10 minutes and the Raptor E1 drone flew at an altitude of 80 meters – although it could have gone for two hours with the fuel it had on board. Designed and built by Cella Energy, the hydrogen gas generator uses solid, lightweight hydrogen storage material, which is capable of releasing large quantities of hydrogen when heated and when combined with a fuel cell (supplied and integrated by Arcola Energy) creates electrical power. According to SAMS the complete system, comprising Cella Energy’s gas generator and lightweight hydrogen storage material along with Arcola Energy’s fuel cell, is considerably lighter than the lithium ion battery it replaced. The system uses around 100 solid pellets packed into a cartridge. The 1-centimeter-square pellets are made from a chemical compound that produces a steady stream of hydrogen as they are gently heated. This gas is then converted into electricity in a fuel cell that runs the drone’s rotor. Since the lightweight hydrogen storage material (solid pellets packed into a cartridge) is a solid and is not under compression this technology addresses several security issues related with the transportation of compressed hydrogen gas onboard a drone in the pressure cylinder.
Designed and manufactured by Chinese-based MicroMultiCopter (MMC) Aero Technology the HyDrone 1550 is known to be the first hydrogen-powered drone, a hexacopter, in the world. The HyDrone 1550 with a hydrogen fuel cell has been tested at altitudes of over 14,000 feet. In 2017, the HyDrone 1550 was used to rescue 3 people during a mission on Changbai Mountain near China’s northeastern border, an area where the extreme altitude and the low average temperature of over –10ºC, which would have impossible with a LiPo-powered drone. With the total weight of 16.5kg and standard take-off weight of 18.5kg the HyDrone 1550 has dimensions of 1550 (L) x 1342 (W) x 610 (H) mm. Here are some specs and details for the HyDrone 1550:
• 150 minutes endurance (without payload) with hydrogen fuel cell
• 10 km flight radius with 2 km (2.4GHz) / 10 km (900MHz) communication & control frequency range
• >90 km flight distance
• 9 litters hydrogen storage volume
• Maximum service ceiling of 4.500m above sea level
• Lightweight carbon fiber body
• Rain- and dust-proof
• Compatible with several camera types
• Comes with route planning for autonomous flight and GCS-controlled flight
In May 2015, Singaporean company Horizon Unmanned Systems (HUS) unveiled the HYCOPTER multirotor drone, that runs on a lightweight hydrogen fuel cell able to deliver up to 4 hours of flight time unloaded, and 2.5 hours when it’s carrying 2.2 pounds of cargo. HYCOPTER’s special fuel cell was designed by sister company Horizon Energy Systems (HES). The HYCOPTER HPD is currently in service with the Dubai Police Force and was showcased by Dubai Police Force Officers at the Intersec 2019 security trade show held in January 2019 in Dubai. According to Dubai Police the hydrogen-powered drone is the first of its kind and can fly for more than 3 hours continuously.
On April 10, 2016 MicroMultiCopters Aero Technology (MMC) hosted a launch event to debut their new a 2nd generation HPD HyDrone 1800. In February 2017 at the IDEX 2017 Exhibition together with CATIC, MMC unveiled the military version of the HyDrone 1800. As an upgrade for the HyDrone 1550, the HyDrone 1800 is designed for use in the toughest conditions, the drone is wind-resistant, rain-resistant, and cold-resistant. The HyDrone 1800 achieves the extended flight time while maintaining altitude limits of 4,500 meters and has a payload capacity of up to 5kg. The HyDrone 1800 can be used for intelligence gathering, border patrol, aerial fire support, laser designation, or battle management services to tactical military operators. MMC also offers packaged solutions in target acquisition and reconnaissance technology (ISTAR). The HyDrone 1800 can be refueled in less than 40 minutes and has a double back up flight control system. It has a flight duration of 2 hours to 273 minutes (4.5 hours) and the ability to fly for about 100km when combined with MMC tethered technology. MMC’s hydrogen fuel cell called the “H-1 Fuel Cell” beaks the limitations of the lithium battery as its flight endurance spans up to 4 hours. It is designed for a wide range of commercial drones (both for fixed-wing and multi-rotors UAV, such as DJI M600, MMC HyDrone 1550 and MMC A6 Plus, etc. The H1-Fuel Cell has a lifespan of up to 1,000 hours.
On April 16, 2019 MetaVista, a South Korean-based liquid hydrogen specialist, achieved a new Guinness World Record for the longest multi-rotor flight time with a multirotor drone fitted with a 6-litter liquid hydrogen cylinder and an 800W hydrogen-based Fuel Cell Module made by Intelligent Energy. That drone flew 12 hours, 7 minutes and 5 seconds. MetaVista had previously (in January 2019) completed a 10-hour and 50-minute multi-copter test flight using an Intelligent Energy’s 650W Fuel Cell Power Module (FCPM). During that flight MetaVista used 390 grams of liquid hydrogen in a specially designed 6L cylinder.
On September 17, 2019 MMC launched its new hydrone Griflion H, with a record-breaking 15-hour flight time (10 hours with a 3 kg payload) in Germany during the InterGEO 2019. The Griflion H is a hydrogen-powered vertical take-off and landing drone with an integrated design and MMC-developed hydrogen fuel battery with a maximum hydrogen storage capacity of 27 liters.
In November 2019 a hydrogen fuel cell-powered DS30 octocopter drone of Doosan Mobility Innovation managed a one-hour, 43-minute ocean crossing. During the flight, which was the result of a collaboration between Texas-based drone development company Guinn Partners, Georgia-based Skyfire Consulting, the US Department of Health, and drone manufacturer Doosan Mobility Innovation (DMI) the DS30 drone crossed 43 miles (69 km) of open ocean. Upon successfully reaching its destination, the copter reportedly still had almost 30 minutes of flight time left on its fuel cell. The DS30 can carry a maximum payload of 5 kg (11lbs)
TÜBİTAK MAM Energy Institute and Hydrogen Fuel Cell Modules
The Energy Institute has been working on Energy Storage and Fuel Cells for many years in our country and exhibited the UAV Fuel Cell System and Hydrogen-Fueled Multicopter working with boron and hydrogen sodium interaction at TEKNOFEST Istanbul 2019.
According to TÜBİTAK MAM officials, who we had the opportunity to meet with at the booth, the UAV with 30 minutes endurance and a conventional battery is able to fly for about 1 hour with the use of a Bor-H2 based Fuel Cell. Twice the battery weight is required for similar endurance, so when the Fuel Cell is used, it is sufficient only to increase the amount of fuel carried (with a larger fuel tank, the endurance can be up to 2 hours), with the addition of a lower weight (it was expressed that proportional increase of 50% or less would arise compared to a conventional battery) for longer endurance.
According to the information we have obtained, flight tests were performed in 2019 on a fixed wing unmanned aerial vehicle with a wingspan of 3m with the UAV Fuel Cell System, operating with the interaction of boron and hydrogen sodium with 200W output power. On the upper part of the Geomatics Group’s Hydrogen-Fueled Multicopter exhibited at the booth, there was a type-4 class hydrogen fuel tank of 1.3 kg (2 liters) and resistant to 300 bar pressure, and at the lower end, there was a TUBITAK Fuel Cell and a 2,650mAh LiPo battery (COTS/RaHAT material). The Fuel Cell is charged during the flight with hydrogen fuel, and the charging of the upper battery is achieved with the electrical energy produced by the Fuel Cell. When the hydrogen in the tank runs out, a safe landing is provided with a charged LiPo battery.
Here are some specs and details for the Geomatics Group Quadcopter with the TÜBİTAK MAM Fuel Cell Module:
• 150 minutes of endurance with a hydrogen fuel cell
• 5 km flight radius with 10 km data transfer rage capacity at 2.4 GHz and 5.8 GHz frequencies
• Maximum service ceiling of 2,500 m above sea level
• 300 m – 500 m average mission flight altitude
• 2 liters of hydrogen storage volume
• Rain and dust proof