Electric Sky wins DARPA grant to develop wireless charging system for drones
Startup Electric Sky announced that it has begun building its first Whisper Beam transmitter to provide precisely focused wireless power to unmanned aerial vehicles in flight, thanks to a $225,000 award from the U.S. Department of Defense's Defense Advanced Research Projects Agency.
Electric Sky will use a six-month Phase I award, provided under DARPA's Small Business Innovation Research program, to study ways to adapt its wireless architecture to control drone swarms.
The first stage of the project involves building and testing a demonstration laboratory bench system that will operate over short distances. These experiments are expected to provide data that can be used to upgrade the system, increasing power and distance.
Electric Sky has offices in the Seattle area and in Midland, Texas. Its CEO is Robert Millman, formerly general counsel of Jeff Bezos's space company Blue Origin. Former XCOR Aerospace CEO Jeff Greason is a co-founder of the company, as well as its chief technologist and the inventor of the Whisper Beam system.
The company's mission is to introduce innovative technologies in power generation and propulsion for aircraft and flying vehicles of all sizes.
Electric Sky is not the only company specializing in wireless power for drones. For example, PowerLight Technologies of Seattle is working on a laser system that could power unmanned aerial vehicles as well as 5G base stations. The principle is fairly simple: a powerful laser on the ground automatically tracks the drone with its beam, illuminating photovoltaic cells on its body.
Energy obtained from the battery goes to charging the drone's batteries and powering its electric motors. Such systems are expensive and not very efficient. The laser requires many times more energy input than can then be extracted from the photovoltaic cell. In addition, the operation of such a system depends on weather conditions.
There are also attempts to remotely supply drones with electricity using a directed microwave beam, part of which is captured on board the device and converted into current that powers the onboard battery system. This approach also has problems: a beam with higher energy density can damage the drone's onboard electronics, while a lower density will not provide the power needed for a meaningful battery recharge.
Laser and microwave beams are usually strong at first but become weaker as they travel. By contrast, Whisper Beam transmissions are weak at first but become stronger near the receiver.
“Whisper Beam technology is the electromagnetic equivalent of a "whispering gallery." In a "whispering gallery," one listener across the room can hear the speaker, but no one else can, even people standing directly between the speaker and the listener. The sound is too faint for them to hear it”
The whispering gallery effect is related to the propagation of an acoustic wave that is totally internally reflected many times, forming a so-called standing wave known as a whispering gallery mode. In radio engineering, a similar effect is used to create microwave and optical resonators.
Radio waves emitted by the Electric Sky transmitter self-focus on the receiver, allowing a drone to draw kilowatts of power in any weather.
“It is a myth that transmitting electricity over long distances is impossible. It has never been economical. This new method reduces the cost of the ground transmitter and the size of the vehicle's onboard receiver”
According to him, the beam system can be used with any type of electric aircraft.
“Any type of electric aircraft can draw energy during flight: an electric battery, a hydrogen fuel cell, or a hybrid. Whisper Beam technology is especially useful during the energy-intensive phases of takeoff and climb, allowing vehicle designers to meet other requirements such as extending range, improving flight safety, reducing peak battery loads and cutting ground servicing time”
For DARPA, Electric Sky will study the possibility of adapting the new wireless architecture to control UAV swarms. Working under DARPA's Small Business Innovation Research (SBIR) program, the startup will build and test a demonstration laboratory bench over short distances. These experiments will provide the data needed to move to higher power and longer distances, after which the transmitter will be adapted to track the drone across the sky.
Solving the problem of charging drones in flight would open up many opportunities for developing the concept of a heterogeneous swarm of small unmanned aircraft capable of performing both civilian and military tasks.
