A regular comment we see on electric aircraft is to “just add solar panels to the wings.” [James] from Project Air has been working on just such a solar plane, and as he shows in the video after the break, it is not a trivial challenge.
A solar RC plane has several difficult engineering challenges masquerading as one. First, you need a solid, efficient airframe with enough surface area for solar panels. Then, you need a reliable, lightweight, and efficient solar charging system and, finally, a well-tuned autopilot to compensate for a human pilot’s limited endurance and attention span.
In part one of this project, a fault in the electrical system caused a catastrophe so James started by benching all the electricals. He discovered the MPPT controller had a battery cutoff feature that he was unaware of, which likely caused the crash. His solution was to connect the solar panels to the input of a 16.7 V voltage regulator—just under the fully charged voltage of a 4S LiPo battery— and wire the ESC, control electronics, and battery in parallel to the output. This should keep the battery charged as long as the motor doesn’t consume too much power.
After rebuilding the airframe and flight testing without the solar system, [James] found the foam wing spars were not up to the task, so he added aluminum L-sections for stiffness. The solar panels and charging system were next, followed by more bench tests. On the test flight, it turned out the aircraft was now underpowered and struggled to gain altitude thanks to the added weight of the solar system. With sluggish control responses,[James] eventually lost sight of it behind some trees, which led to a flat spin and unplanned landing.
Fortunately, the aircraft didn’t sustain any damage, but [James] plans to redesign it anyway to reduce the weight and make it work with the existing power system.
We’ve seen several solar planes from [rctestflight] and meticulously engineered versions from [Bearospace Industrues]. If long flight times is primarily what you are after, you can always ditch the panels and use a big battery for 10+ hour flights.
Reminds me of the “before I sputter out” song. ;-)
(Novocaine for the Soul)
I work with electric buses and have frequently been asked why they don’t have solar panels on their roof.
In an unrealistic best-case scenario, solar panels can account for about 1% of the bus’ power budget, while 0,1% is more realistic.
Plus you’re adding weight to an object which then costs more energy to move, you can’t angle the panels optimally, the panels will be exposed to vibration so may fail earlier, they may need a tougher surface than normal (think solar roadways) etc. Stationary installations tend to be better but then your vehicle may be away from the panels during peak production so you’d have to add some battery storage next to the panels.
None of this should detract from solar planes as a fun design challenge, they’re really cool and could be useful for monitoring drones!
People have a mostly-magical conception of the abilities of photovoltaics, it seems. I remember that whole solar freakin’ roadway redditard explosion several years ago, what a silly thing
However, by the same token a BYD bus is ~18ton. 1% of that is 180kg. 180kg definitely allows flexible solar on the roof.
There is nothing wrong with adding 1% to the weight and getting 1% more range.
The power is actually a little bit more valuable on the bus than connected to the grid. If the power is economic on a building, it might be economic on a bus. Just because it’s only 1% doesn’t mean you shouldn’t take that 1%
That said, there are quite a lot of issues in fitting panels to vehicles. Panels on houses is a solved problem, solar on vehicle roofs is yet to be solved.
Panels on houses are solved, battery storage on ground is (kind of) solved, overhead wires is long solved … what’s the problem?
Good job!
If He didn’t see it how does he know it was in a flat spin? If its spinning, its stalled and rudder should be enough to straighten it back out. Worse case a bit of down also.
Solar power has been done, it is just much bigger than a big zagi
Weather and hours of available daylight make power management a difficult problem. This company has managed multi-day flights: https://skydweller.aero/
Ransomware
“just add solar panels to the wings.”
nah
“just add modular nuclear reactors to the wings”
;)
And you can save weight, by getting rid of the landing gear! Because you wouldn’t want to be anywhere near it when it lands anyway.