Pure solar drone flies for over five hours straight
South African Luke Maximo Bell has improved his solar drone and set the unofficial record for duration flights of electric multirotor drones.
Luke Maximo Bell's solar drone in hover mode.
(Image: Luke Maximo Bell / Screenshot)
South African engineer Luke Maximo Bell has redesigned his four-engine solar quadcopter, which can fly without a buffer battery, and subjected it to an endurance test. On a sunny, windless day, the drone flew continuously for more than five hours on pure solar energy in hover mode. The drone could have stayed in the air longer but had to land after exactly 5 hours, 2 minutes, and 21 seconds due to problematic wind conditions.
For the redesign of the first solar drone, Bell analyzed the quadcopter's weaknesses. One difficulty arose primarily from the fragile solar cells, which were applied to a lattice structure of thin carbon rods. In the new design, the hobbyist reinforced the lattice and also ensured that the thin Maxeon Sunpower C60 silicon solar panels, each 5 W, were attached in such a way that they could no longer break so easily. An array of 8x4 panels is now used. In full sunlight, the solar cells deliver a total of about 100 W at around 18 V, with peaks of up to 110 W. The solar panels are mounted above the drone to capture the sun optimally.
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Bell also reduced the length of the booms to which the four motors are attached. In the first version of the solar drone, the booms were longer and the drone was larger. This resulted in an undesirable rotation of the aircraft, which had to be constantly compensated for, costing power. The second version of the solar drone exhibits this tendency to rotate less due to the reduction in size and therefore requires less power for corrections. It also reduces the weight by about 70 g, which further reduces power consumption.
Bell took over the T-Motor Antigravity MN4005 300 KV motors, four NS-18x6 carbon rotors, and the control electronics and Electronic Speed Controller (ESC) from the previous version.
Flight tests and troubleshooting
However, an initial test flight of the solar drone on a day with low wind and strong solar radiation failed. The drone had to be landed after just over 2 minutes due to instability. The cause proved to be that the solar cells could not provide a continuously sufficient power supply. Bell decided to install a small 720 mAh buffer battery, which is charged by the solar cells and can step in during short-term power fluctuations. Bell also stabilized the wobbly solar cell structure by reinforcing it and recessed the cells. The engineer also reduced the number of panels to 28, which, according to previous simulations, promised no major impact on flight capability.
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The second test flight, also in a location with low wind and high solar radiation, initially failed due to a loose motor. After the repair, the solar drone flew stably enough in hover mode until the GPS failed due to lack of power during a brief period of cloud cover. Bell then took manual control to continuously compensate for wind influence, which proved mentally strenuous. However, the GPS reconnected, and the drone was able to hold its position independently again. After 3 hours, 31 minutes, and 6 seconds, the drone broke the existing unofficial record for continuous flights for an electric multirotor drone (with battery). After a total of 5 hours, 2 minutes, and 21 seconds, Bell had to land the drone as a precaution due to worsening wind conditions and reduced solar radiation.
(olb)
