For portable electronics, one of the most significant design challenges for engineers is how to increase battery life. Generally, there are two approaches: either make low-power electronics or create batteries that can go long stretches in between charges.
New fuel cell-powered drone.
Drones are no exception to this design challenge. The average drone today gets about one hour of flight before it needs to be recharged. This could severely hinder a drone’s usefulness, especially when it is used for things like disaster relief.
Engineers in Korea have been working for years to solve this problem, and just this week they’ve announced some significant achievements.
Bringing Fuel Cells to Drones
Korean group Doosan Mobility Innovations (DMI) announced this week that they’ve been able to successfully extend the flight time of drones to over two hours.
The group achieved this thanks to a variety of design innovations, namely the incorporation of hydrogen fuel cells. Compared to Li-ion or LiPo batteries, hydrogen fuel cells offer many advantages, primarily their high energy to weight ratio.
The problem with incorporating hydrogen fuel cells into drones thus far has been their high cost and weight, according to researchers at the American University of Sharjah. Researchers like those at Pohang University of Science and Technology have been working on miniaturized fuel cells for drones for years now with the hopes of longer and more affordable flights.
LiPo vs. fuel cell endurance vs. power.
The engineers at DMI have solved this issue with what they’re calling the DP30, a 2.6 kW miniaturized fuel cell power pack. They’ve achieved miniaturization and weight reduction by utilizing very thin metals with a proprietary technology for the bipolar plates in the fuel cell.
Generally, bipolar plates isolate cells, uniformly distributing fuel and air and conducting current from cell to cell. This accounts for the largest portion of the cell’s weight. The pack also introduces DMI’s Membrane Electrode Assembly (MEA), which enables high energy output and durability for the pack.
The Electronics Behind the DMI Drone
Equally as important as the miniaturization of the fuel cell is the optimization of the electronics that augment the power pack. DMI’s design focus in this respect was the architecture of their power delivery network.
The DP30 incorporates two main powertrains that deliver power to the drone’s rotors and the stack controllers. These powertrains were designed to provide exactly 48 V, 12 A output to the rotor motors, while delivering 12 V, 8 A to the controller board and peripherals, such as fans.
Hydrogen fuel cell different operating phases.
For the rotor’s power delivery network, voltage is regulated by two buck-boost regulators set up in parallel to supply 12 A to the motors. The digital controller board uses a low power buck-boost regulator along with a 48 V–12 V zero-voltage switching (ZVS) buck regulator.
Utilizing high efficiency, buck/boost regulators was clearly another important design feature that allowed for successful fuel cell miniaturization.
Longer Flights For Humanitarian Relief
An hour of extra flight time can make a big difference when it comes to using drones for humanitarian missions. So far, DMI’s drones have delivered masks and emergency supplies to the U.S. Virgin Islands and medical AEDs to the top of Mt. Hallasan (6,388 ft), the tallest mountain in South Korea. When flying the same missions with conventional battery-powered drones, the missions required up to 6 battery changes.
The scope of this development goes far beyond just drones. Research out of the University of Calcutta suggests that hydrogen fuel cells could be useful for all portable electronics, like smartphones, radios, and portable cooling devices.
All images used courtesy of DMI.