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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I would suggest a small heating element to melt the snow and keep it clear, or a fan that blow warm air over it. Obviously there are power issue with that, maybe it can be made to be remotely controlled.for example http://www.flexelec.com/products.html

You only need to keep it above freezing for it to slowly melt any snow. you could make it use power only in the early part of the day to improve snow melt at sunrise.

Another idea would be adding wiper blades from a car. And this give me an idea that you oculd use something liike this http://www.frostfighter.com/clear-view-defrosters-about.htm

The problem with snow blowing with a drone, it that the snow, if it's partially melted and re-frozen will be an unmovable block.

Hope that helps.

The issue with any permanent equipment on the ridge is that I have extremely little power available. All the hardware up there only draws 14 watts. Any sort of powered heater or heater/blower would take at least 500 watts at the very least and would fully drain the batteries in minutes. I am not allowed to place any propane up there since its exposed without adequate electrical grounding.

The panel are at a decent angle ~40 degrees. I would think if I can just melt the snow enough to expose the glass, water should drip off nicely. I agree that if I only partially melt the snow, I haven't done a bit of good. I thought about wipers which probably could use low power, but just like a car, they don't really work unless its dry snow and no ice.

I was thinking of trying a test with an infrared heater or small heated blower. Assuming I can get the panel cleared off completely in about 10 minutes, I suppose a drone could work, correct? Is a 10 minute run time and 5 pound payload within my budget for a GPS drone?

The problem as I see it would be to carry the power source for the 500W or whatever required to heat the panel for the time required to melt the snow. A drone has the capability to hover over the spot fairly accurately for 10 minutes or more, you could even use a small camera for more precise positioning over the panel/s, something like a Phantom 2 would work fine.

The heater and it's power source however will weight a fair bit, especially as to achieve 500W you'll need a fair amount of amps as it's not practical for the voltage to be as high as a domestic installation. To carry that you'd need a bigger flight battery, more efficient props and maybe bigger motors which weigh more and so you get diminishing returns.

Oh, well that is why I wanted to use propane as a heat source. You know those small 1 lb propane tanks that are used for camping? Well they make small infrared heaters that use those. They can run for about 3 hours and output around 5000 BTU / hr or about 1500W. I was thinking that should be more than sufficient to melt off snow on 8 square feet of solar panels rather quickly.  

Yes that would work much better with so much less weight to carry. Not sure how safe it is to have a 1lb propane tank up on the MR but probably not much more risky than using it in the garage. You'll have to figure out a safe, reliable mechanism to turn it on and then to ignite it once at the target and either let it run empty or just turn it off. Servo's would probably be the easiest. Propwash might give some headaches with the flame and/or ignition but sure that could be worked around. The idea is certainly feasible and should be fun too. A Pixhawk controlled MR with a few extra channels for controlling the heater would be a good platform. One could even plan the ignition and heat to activate automatically once on target...

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. 

You don't need 500W, just enough heat to keep the panel just above freezing. Any snow that lands will melt and run off. A potential strategy with power at a premium is you an run the heater only a hour before sunrise, and the sun/daylight will help get rid of the snow, but you have already started the warming process. 

Its a solution more focused on prevention, than cure. ie use 1W heater to keep the temp a 2-3C for example, is less power costly than raising it from -5C to 25C to quickly melt the snow/ice

PS: I realise this solution does not have the cool factor of a flame thrower mounted on a drone ;-)

Well, Bill, I am open to suggestions, but I just don't see a couple watts doing anything to prevent snow accumulating on the panels. There is 8 square feet of surface area here and its normal to have Colorado temperatures stay below 10 F for multiple days on end. The reason snow ends up staying around for days even in full sun is because its so flipping cold. I guess I just don't see a 5 watt conductive heater doing anything if 8 hours of full sunlight isn't capable of even beginning to melt the snow. 

Here is an example. McMaster has these Watlow heat sheets I have used before. They work great and provide great conduction to a surface. 

http://www.mcmaster.com/#35765k265/=ykxe8u

This is the smallest one made. It intakes 8 watts and is the lowest heat density they offer. The sheet is only 3 square inches in size. I really don't think 3 square inches would even begin to touch the snow on a 4 square foot panel. 

Is there a better option you know of? 

Well, yes, that is an appeal as well. Not going to lie.... I do like the idea of using a drone to do this, but seriously, if you think that there is a 5W heater that can keep a panel above 32F, I will look into it. That would be a ridiculously cheap and easy solution.  

Mount the panels at a steeper angle, then the snow won't settle on them?

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.

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