China has created an ultra-light drone that will fly as long as the sun shines

A group of Chinese scientists have solved the problem of “endless” power supply for ultra-light drones. They abandoned traditional electric motors, which are too heavy for subminiature devices. The proposed electrostatic motor has shown impressive efficiency and the ability to operate as long as sunlight falls on the drone. The power comes from solar panels, and then Coulomb forces come into play.

The CoulombFly drone is caged to prevent it from flying far. Image source: Nature

The researchers created a prototype of a flying device weighing 4 g with a propeller with a diameter of 10 cm. The experience gained was then embodied in a prototype with a height of 8 mm and a mass of 9 mg. The drones immediately began to rise into the air as soon as the rays of the Sun hit them, so they hovered in cages so that they would not scatter around the room or fly out the window.

Scientists have not yet set themselves the task of achieving controlled flight. There is still a lot of work to be done to optimize the platform, but prospects have nevertheless been outlined. The lightest aerial drones can stay aloft for hours on solar power alone. And they will be able to soar into the air with the beginning of each new day.

The drone’s engine is powered by thin-film solar cells based on gallium arsenide. Their efficiency, combined with low weight, is one of the highest in the world today. To operate the electrostatic motor using the effects of Coulomb charge attraction and repulsion, the input voltage had to be increased from 4.5 V to 9 kV. The inverter has become one of the heaviest parts of the drone. It is located on a platform at the very bottom of the drone and also works as a counterweight. The efficiency of the inverter was only 24% with its weight of 1.13 g. This is very wasteful for a device weighing 4 g, but there was nowhere to go.

The entire system requires just over half a watt of energy to stay aloft. With a total mass of 4 g, an efficiency of 7.6 g/W is obtained. But most of this power is lost during voltage conversion. If we focus only on the motor, it only requires 0.14 W, which means its energy efficiency exceeds 30 g/W.

The entire drone is actually an electrostatic engine with a body kit made of a solar battery and a high-voltage converter. The engine stator is made up of 64 carbon plates covered with foil. The plate charges alternate to create repulsive and attractive forces. The rotor is also a ring of charged plates placed as close as possible to the ring of stator plates. A 10 cm propeller is attached to the rotor. As the rotor rotates, charge flows through the contacts from the stator plates to the opposite rotor plates and creates repulsive forces after it is balanced. The rotation speed of the blades of the 9-MG drone reaches an impressive 15 thousand rpm.

The team of scientists still has a huge potential to optimize all components of the “endlessly” flying platform. They proved the concept works, and then it’s a matter of technology.