A palm-sized Chinese drone weighing less than a sheet of paper has attracted widespread media attention because its innovative engine allows it to continue flying as long as sunlight hits it.
The solar machine was designed by researchers from Beihang University in Beijing, who are known for their expertise in aerospace research. It is only one-tenth the size of the previous record holder as the smallest solar-powered aircraft and one-600th its weight.
Micro-aerial vehicles have a variety of applications, from environmental monitoring to search and rescue, making them versatile tools. They can perform specialized tasks such as taking pictures, detecting objects, and transporting objects in confined spaces. However, the limited flight time is a significant obstacle to their usefulness.
Traditional micro-aerial vehicles use electromagnetic motors to drive their rotors. However, small motors overheat at high rpm, causing a sharp drop in energy conversion efficiency. Natural sunlight can be a potential alternative as a power source, but the smaller the drone, the smaller the area it needs to collect sunlight, said lead researcher Qi Mingjing.
In their study published Thursday in the journal Nature, the research team reported that traditional flying machines weighing less than 10 grams can only stay in the air for 10 minutes.
To overcome efficiency issues, Qi and his colleagues developed an electrostatic motor that uses the Coulomb force, the force between electrically charged particles at rest, to generate continuous rotational motion. The drone’s name, CoulombFly, comes from its unique engine.
A demonstration video presented by the researchers shows that the motor works by creating a ring of electrical charges that generate a twisting force to spin one blade like those on a helicopter.
The advantage of such a motor is that it can effectively reduce heat, said co-author Peng Jinzhe.
“This is because static electricity works at high voltage and low current,” Peng said. “The lower the current, the less heat it generates.”
The energy conversion efficiency of flying machines weighing less than 5 grams and powered by such static electricity could exceed ten times the efficiency of traditional electromagnetic motors with less than a tenth of the energy consumption required for the same lift, according to the study.
Prior to the breakthrough, Harvard University researchers published a paper in Nature in 2019 introducing the Robobee aircraft they had developed, which was once considered the highest level of micro-aerial vehicles. For sustained flight, however, it relied on an artificial light source equivalent to three times the intensity of natural sunlight.
CoulombFly can achieve continuous flight based on natural light alone, which represents a significant leap forward, Beihang researchers said.
After further development, the new drone engine technology is expected to be used in emergency rescue operations, narrow space detection and other similar scenarios, said Professor Yan Xiaojun, one of the study’s lead researchers.
