I have an unusual application that I wanting some advice on to see if a drone may be feasible. We have a remote business here that relies on internet through an antenna powered by two small 60W solar panels. It works well, but we are having issues with snow accumulating on the tops of the panels and sitting for days during the winter which is draining the batteries excessively to the point where the link fails. The batteries can survive a day or two without sun, but this snow can sit for well over a week before being melted which is too much for the batteries to handle.
The antenna is about 1/2 mile away up on a ridge about 300-400 feet higher than the buildings here. There is no vehicle access up there and its difficult if not dangerous to head up there with any chance of ice since there are precarious ledges and sheer drop offs in a number of spots. I am wondering if using a drone with a small camping type infrared propane heater would be feasible to clear the snow off the panels.
I know IR heaters are often used to melt snow, but I am not so sure how easy this would be for a drone. It would have to hold position well within a 2 cubic foot box. Its all line of sight from our property and every property I have to cross is leased or owned by me.
I have some past experience with gas RC helicopters in college and could fly them well, but that was a long time ago. Otherwise, I have little experience with drones, though I find them fascinating.
I guess the 2 questions are first if you all think this is feasible and / or recommended. Secondly if feasible, we would have a budget of about $1200 or so. Is this remotely possible for that kind of money? I might be able to justify more just for the fact that this sounds like a cool way to clear off solar panels, but when it comes down to it, anything much more expensive and we could probably upgrade the batteries for a couple thousand and fix this problem another way.
A picture of the antenna is attached.
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Biggest problem with heater, is accidentally cracking cold glass on panel.
After drone cracks panel, either with heat or prop contact, and trip up mountain is required in winter, Noah will wish he made trip in nicer weather. Anything with a drone is not going to work reliably, and the risk/reward ratio is not good.
#1 Optimize panels for winter, increase tilt at least 15 deg, 40 degrees tilt for your latitude is optimum only at solar equinoxes, at winter solstice, sun is lower. Aim panels southwest instead of south, solar noon at solstice is ideal.
You will get more output from panels in other seasons, in spite of winter optimization, because days are longer and solar radiation increases. steeper angle helps also with snow removal. Because of snow I would mount panels near vertical, and increase size to overcome loss of efficiency.
#2 Increase panel size, larger panels are more economical, I paid $200 3 years ago for a 235w panel for my boat.
Mounting costs do go up for larger panels.
#3 In Colorado, you will be lucky to hit 90w peak from two 60w panels, and only in early summer. On my house roof on a sunny Dec 26 I got 440Wh and a peak power of 103W out of my best 260W panel (20 panels total). That panel is practically horizontal, the others are 15 deg to SW. and produce less by missing morning sun.
windshield wiper with a decent servo should be more than enough
JoeBob, rotor wash would probably work well most of the time. I agree that unless there is ice or crusty snow, just the air moving from the rotors would probably clear most all the snow. The heat source was just if there was ice or the snow was crusty enough to not move with the rotor air. Good suggestion and point.
Thanks all for your suggestions. I probably didn't do a good enough job explaining this ridge and setup. Some of these recent suggestions imply we can just hike up there and flip off a cover or something. Here is a picture of the ridge. Its solid rock almost all the way up and line of sight distance antenna to antenna is 0.6 miles. Actual hiking distance is about 2 miles round trip. It takes at minimum 30 minutes to hike up and back in summer and good weather and that is if you really book it.
Just getting that antenna link setup was quite a feat. All the parts had to be hand carried up there, be completely modular for assembly, and be absolutely bulletproof in reliability and able to withstand the harshest elements and extreme wind at times.
No solution that involves climbing the ridge in snow is feasible. Its dangerous and only one me and one of our eight employees is willing to climb it at any time anyways. The rest find the climbing too strenuous.
Anyways, the extra solar panel and battery suggestion for lasting through a storm and/ or heating would probably work. Again, its just a matter of cost. Like I said, setting anything up there is difficult. Another 120W of panels and batteries would cost thousands to actually install. It requires 30 hours of hiking back and forth as well as bringing battery operated tools to drill into the rocks and install anchors. Then you need lightning protection by grounding the structure about 200 feet below the rock face into dirt, etc, etc.
I don't see any sort of remote operated cover or slide over the panels working well for ice reasons. Anyone that has left a car outside in cold weather probably agrees. Windshield wipers use very strong high power motors, yet even a small amount of ice on them will lock them solid when you start your car and turn them on. It takes 5 minutes of rigorous scraping to get them free. Its warm during the day and then snows later. The snow starts out as water film on the panels and then when it freezes turns to rock hard ice that can stay there for days on end if it remains cold.
An automated flip cover could probably work, but you would have to be absolutely perfect in your timing of covering the panels as soon as it started to snow. That means I have to have someone here basically 24/7 watching to flip the covers in bad weather. If ice accumulates on the panels and then you flip the covers, you did no good. If someone knows of an automatic sensor that is perfect in detecting water falling from the sky, it could maybe work.
Changing the panel angle would be a great idea, but unfortunately, I can't do that because it changes the power input to the panel based on the sun's position. They are set to provide maximum output in all seasons. In the winter you actually want them flatter at about a 5 degree angle I believe based our altitude. If I had them perfectly vertical, I may get a very slight amount of sun, but not enough power to do anything with.
Ridge Profile.jpg
Why not just use the rotor wash to blow the snow off before it develops a crust? I've used my MR to blow leaves off of steeply inclined roofs.
Using Pixhawk, you could program an auto mission to fly up, move around the panels blowing off the powder, and fly back down for a new battery for the next panel mission.
Another option, depending on the metal composition of the panels, would be to bomb salt from your MR onto the snow for melting.
Use a window shade like device mounted on lower edge of array with a small motor to extend/retract.
You should be able to extend shade under accumulated snow, when shade retracts (slowly) snow will slide off.
Also, for cold weather use, insulate bottom of panels with foam panels. Self heating of panels while generating will help to melt/sublimate any residual snow/ice.
How about a flip top lid? Close it during dark or when it is snowing. Flip it open to eject the snow and bring in the sunlight.
You could insulate the lid so with a little power you keep the panel dry. If you insulate the lid then you can make it a mirror and reflect some extra sunlight onto the panel.
The only down side is that lid is going to make a nice wind sail. The first windy day might remove the lid or the whole installation. You might find a rolling, sliding or folding lid that works best for all conditions. For thick ice you might need a flexible lid that you intentionally flex to crack the ice off it.
Having said that, the first windy day and you loose your $1000 drone rather than a $10 plywood cover.
If you really just want an excuse for a flame throwing drone then please don't let me get in your way.
A variation on that would be to have the panels in a clamshell arrangement that you can unfurl during daylight. I suppose the risk here though is that over night the panels could freeze together.
The other thing I thought of was putting the whole panel assembly inside a polycarbonate (or similar) dome, waste heat that reflects off the panels during the day will heat the dome and thus help to alleviate the freezing issue. Additionally the curvature of the dome may help to prevent snow sticking and aid in it blowing away.
Finally I'm unclear on the cost of the panels but would adding 2 more panels to provide a further (theoretical 120 watts) not be sufficient to charge an additional battery to keep a small heat source running? It could be set to kick in when the light level dropped below a certain threshold and/or on a timer
Mount the panels at a steeper angle, then the snow won't settle on them?
Cool, thanks for the info Graham. I was hoping I could bypass the switch with a relay or something, but we can get to that later. Do you have any suggestions as far as a specific drone to go for and what hardware? Again, I have been out of the copter field for a long time so I know very little about what is out there. Thanks again for all your time here.
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