Heat tape on the back of the panel to melt snow?
Hi everyone, I hope you guys don't mind me registering to ask some questions...
To give you a little background - I'm off the grid in north-central CO full time. I have a 2800 rated watt PV array running through a trace and a couple of outbacks, charging a 16 battery bank made up of Rolls 530 amp hour lead acid batteries. As you'd probably guess, the system runs great.
Only issue we have is in December when the temp drops to about -20 overnight and hovers around -5 during the day. When it's that cold, even 2" of snow on the solar panels isn't going anywhere, even in bright sunshine at 9600'.
Since I have a bit of a panel access issue, I've been kicking around various ideas about how to deal with the snow besides climbing up and brooming it off. One thing that came to mind was that since the panels are so thin in most places, I might be able to run heat tape along the back of the panels with the idea that I could even run the tape off my generator. I'm concerned that this approach will either generate too much heat and damage the panels, or not enough heat and will have no effect on the snow load.
Anyone here play around with this idea at all?
Generally, the panels will heat up even with snow, and self-shed in a day. But maybe it's too cold. How hot does the tape get ? I wonder if putting it on the alum frame would be enough, I'd be very careful about applying heat to the backside sealing layer..
What about windshield de-icer ? Or a good coat of wax before snow season ? This is the first I've heard of panels not clearing. Maybe a sheet of styrofoam cut to fit backside to retain heat, and allow to thaw. Remove before warm weather.
Hi Mike, thanks for the reply. Lots of days, the sun does melt the snow off, but even in many of those instances it would be very helpful to be able to do it on command. Frequently, snow comes over a 3 or 4 day period and we'll be doing a regular generator cycle to keep the batteries at a good voltage. When the sun comes out, losing several hours of it to snow melt just means I've got another day of generator. Not to mention that that generator doesn't really get the batteries all the way full. You can really tell after a good storm when we'll make ~23 kw in the next two good sun days. A normal daily recharge is about 6kw.
Originally Posted by Mike90250
I thought about doing the frame as well but was concerned it wouldn't have enough effect - it's an easy way to do it, but I've never heard a success story. The problem I see with the styrofoam is that it insulates against heat as well as cold. When the sun comes out, the glare up on the snow covered roof is ridiculous and when there's no wind, the temp rises very quickly. And unfortunately, since we live near the tree line, there's always a decent amount of dust and pollen blowing around and anything you spray on the panel collects the dirt like a sunuvubich.
I think I'm just going to pass on trying to modify the panels... I just added some stairs and am building a walkway above the panels. I already have a rig to tie into and will just continue going up there and clearing the panels off with a broom. If anyone else has any thoughts, it'd be great to read them. Thanks guys!
9600 feet. Wow. Electrical resistance heating is so ineffiecent I'd seek another solution. I'd suggest using the winter solar horizon to your advange and build a cantalivered roof to cover them. Cantaliver it so you won't lose any summer watts after you remove the actual roofing material.
One member, Mountain, placed his panels vertical under an overhang to get around this problem.
He lives at a ski resort some place way up North.
Loses production in the summer but not too much in the winter he said.
ever thought of mounting the panels on a rack that could be ajusted in two different angles. One low one to get the maximum output in the summer and a steeper one to ommit the snow problem in winter and get a higher output for the lower sun in winter.
The fellow I mentioned, Mountain, also said he placed his panels under the eve of the house - protecting it from snow buildup. He was at one of the ski areas in Western Canada.
Thanks for the replies!
I haven't looked into an eve or replacing the racks, only because of the difficulty of the project. The panels are on the drop side of a modified a-frame, about 45' off the ground. At some point in the future, I'll need to replace the roof on the house, and I'll be looking at those options at that time. I'm hoping to get them off the roof all together, but we're on a north facing ridge... Being up on the roof gives us excellent sun. Far better actually than most of our neighbors on the south facing slope. Even in december/january, we're making power by 9am and then do so until sun set. But 10' off the ground, the sun coverage is lousy in most places, except for one spot that's about 600' from the house. So, it's a bit of a wash in the end. I haven't gotten the walkway built yet, but we're having a nice indian summer here and it could still happen. This time last year, we had 3' of snow in two days...
Melting Snow off solar panels
I saw on you tub a guy selling Midnite controllers and he talked about with his controller you could thru the internet tell your panels to melt the snow...
Just a note .. interesting.. maybe the Midnite people know how too....
Something about working in reverse..?
Hi Ernie - No doubt it can be done but just not efficiently.