Forward-looking: Battery-powered drones that are popular with consumers can typically fly for around 30 minutes before requiring a recharge. Solar power could extend this duration significantly as long as sunlight is available, and researchers are also finding ways to make such devices extremely small and light.
Researchers from the University of Beijing have unveiled an ultra-small prototype drone that can run on solar power indefinitely. Although far from a complete device, the micro-drone could represent a breakthrough in efficiency and longevity.
The above video shows the drone, which is small enough to fit in the palm of a researcher's hand, hovering in place nonstop for over an hour. The video ends before the device ceases functioning, but the published study suggests it can maintain flight for as long as it receives sunlight.
For comparison, similarly sized UAVs like the DelFly Micro must recharge after about three minutes of flight. Larger drones like the top-selling DJI Mini 3 advertise a maximum flight time of around half an hour.
Solar-powered drones aren't new, but the researchers claim to have built the smallest and lightest one by far. It is only a few centimeters long and weighs just under five grams.
Other microdrones struggle with solar energy because solar panels collect less energy as their size decreases. Other experiments have achieved limited success with wirelessly beamed energy, amounting to artificial sunlight. The Beijing researchers claim to have built the first ultra-small drone capable of sustained flight from natural sunlight, as shown in the video demonstration.
The device's main advantage is its electrostatic propulsion, which uses less energy than the electromagnetic motors drones usually employ. Combined with a power converter on the bottom, an apparatus of electrode blades in the center, and a helicopter-like rotor on top, the drone runs on just over half a watt.
However, room for improvement remains. The prototype lacks the control mechanisms necessary for directed flight, as the demo shows it lifting off the ground and hovering within a vertical cage. Although a fully functioning drone would likely weigh more, it would still have a huge endurance advantage over other micro-drones.
The researchers admit that they could also make efficiency and output improvements. Moreover, integrating batteries for night operation might allow the drone to operate around the clock.
