Author Topic: How do you deal with freezing rain and solar panels?  (Read 7073 times)

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Offline Red Squirrel

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How do you deal with freezing rain and solar panels?
« on: December 31, 2018, 11:15:45 pm »
I have a small solar setup on my shed, at this point I have nothing important running off it but it's kind of a pilot project for if I decide to do the house.

Problem is freezing rain.  We got some about a week ago, and now the panels are out of commission for what is probably going to be the rest of winter unless we get a heat wave, which happens sometimes due to global warming.  The broom simply can't break through and it's just a thick crusty layer of snow/ice.  Can't do anything to get the ice off without using force that would damage the panels.

How do large scale solar installs deal with freezing rain?  Do they just use deicer like on planes?  Would not really be a fan of using chemicals like that though.  Heating it is also not an option as it would require WAY too much energy, more than what it will produce.

I'll probably bring the battery inside and charge it and set it aside for now, but ideally I want to come up with something for next winter.
 

Online nctnico

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Re: How do you deal with freezing rain and solar panels?
« Reply #1 on: December 31, 2018, 11:23:31 pm »
De-icing liquid is your best bet. But how much power do you get in the winter anyway with the sun being at a bad angle anyway?
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Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #2 on: December 31, 2018, 11:28:34 pm »
Not a lot because the days are so short and there's no sun (just ambient light from clouds), but if I was to go off grid I'd just oversize the system like 10x what I need.  I would have more land for it.
 

Offline Gyro

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Re: How do you deal with freezing rain and solar panels?
« Reply #3 on: December 31, 2018, 11:59:34 pm »
Rainex type car windscreen type treatment? It may not be a complete fix but it makes the glass a lot more slippery.
« Last Edit: January 04, 2019, 06:24:06 pm by Gyro »
Chris

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Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #4 on: January 01, 2019, 08:26:20 am »
Hmm yeah maybe that could help.   Obviously too late now but something to try next year.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #5 on: January 01, 2019, 08:33:41 am »
back feed stored energy into the panels to melt it?
 

Offline fourtytwo42

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Re: How do you deal with freezing rain and solar panels?
« Reply #6 on: January 01, 2019, 09:06:08 am »
You don't say what angle to the horizontal your panels are but I guess it's not very much allowing the snow to settle, mine are 52 degrees and that helps but of course we don't quite get the weather you get in northern Canada!
I saw a picture of a ground mount array maybe somewhere in this thread also in Canada and I would estimate from the pics his panels were at least 60 degrees in heavy snow and no accumulation on the panels so that may be your answer :)

I remember now it was electrodacuas thread about pv cheaper than natural gas, he actually says its 60 degrees in the text, here is the pic
« Last Edit: January 01, 2019, 09:23:34 am by fourtytwo42 »
 

Online Kleinstein

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Re: How do you deal with freezing rain and solar panels?
« Reply #7 on: January 01, 2019, 12:55:11 pm »
Unless the layer of ice and snow is rather think and white there would be still quite some light going through when the sum comes out. So chances are the ice could melt, come loose and slide down even when the temperatures outside are well below freezing.

I have thermal solar collectors at about 45 degree angle. Snow cover usually does not not stay there very long: it does not take much sun to let it slide down and once the upper 10% are free the rest goes down quite fast.

The usual grid tied solar installations likely just ignore ice cover - it is a rare event and the lost power in winter is not worth that much.
For an off grid installation countermeasures are likely a good idea. It could help having some of the collectors at an steeper angle - up to a south facing vertical wall. If heating is used, it should be likely high power for a short time, so that the energy is mainly used to melt a thin layer and not much heat is lost to the environment.

For extreme conditions a backup ebergy source is likely the better choice.
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #8 on: January 01, 2019, 05:51:30 pm »
it is a rare event and the lost power in winter is not worth that much
That is very location dependent and during winter you need more power for lighting and heating.
 

Online Kleinstein

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Re: How do you deal with freezing rain and solar panels?
« Reply #9 on: January 01, 2019, 11:13:44 pm »
At least in Germany but likely also in many other countries the money payed for PV energy sold to the grid is the same in summer and winter. So the owners of the PV installations usually don't care about the real value, that may be higher in winter. This may be something to change in the future. AFIAK it slowly starts that way  in going towards a bonus paid on top of the market price instead of a fixed rate at all times.

The expected lost possible revenues are in most areas too small to go for some special methods to get rid of snow or ice. This is also reflected in the angle the PV modules are mounted: the preferred angle is rather flat (e.g. 20-30 deg.), while for solar-thermal use one prefers a much steeper angle (e.g. 45-60 deg) to get more power in the winter and fall and less in summer.

For an off grid installation the power in winter is much more valuable. So that is a different story.
So far north PV for heating is likely not a really viable solution. One would at least need a backup in case there is snow or fog.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #10 on: January 02, 2019, 12:51:46 am »
back feed stored energy into the panels to melt it?

I was thinking this but the amount of heat required would probably be much higher than what I can reasonably produce and store, unless I can get my hands on a couple Tesla battery packs lol.   Though it does seem like it might be the easiest option.  I do get a tiny amount of power even through the snow/ice.  Do modern panels allow backfeeding though?  I thought they had a blocking diode.

Suppose I could also add more panels on the wall so they are vertical.  It would at very least trickle charge the battery at the end of the day.  The panels face west so it's not super ideal.  My yard is too small so don't have much to work with in terms of space and shadows.
 
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #11 on: January 02, 2019, 12:57:59 am »
You don't say what angle to the horizontal your panels are but I guess it's not very much allowing the snow to settle, mine are 52 degrees and that helps but of course we don't quite get the weather you get in northern Canada!
I saw a picture of a ground mount array maybe somewhere in this thread also in Canada and I would estimate from the pics his panels were at least 60 degrees in heavy snow and no accumulation on the panels so that may be your answer :)

I remember now it was electrodacuas thread about pv cheaper than natural gas, he actually says its 60 degrees in the text, here is the pic

Yeah that's an awesome setup.  Wish I had room to do that on.  It's my dream to one day to buy off grid land though.
 

Offline edpalmer42

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Re: How do you deal with freezing rain and solar panels?
« Reply #12 on: January 02, 2019, 01:37:10 am »
Check out http://electrodacus.com .  He lives off-grid somewhere near Regina.  He's also a member here so you could PM him.

Ed
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #13 on: January 02, 2019, 04:38:15 am »
Yeah I've seen his stuff, pretty impressive, would love to have room to build out a bigger system.  His are tilted better so I imagine it's less of an issue.  I guess maybe that's what I need to look into myself, to see if I can redesign my mounting setup so they are tilted better.   Just need to figure out the unistrut hardware to do that with.  Has to be very strong as we get very strong wind gusts here sometimes and having them tilted with make them more vulnerable.

This is the setup now, before the snow came:


 
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #14 on: January 02, 2019, 05:55:43 am »
Ice will sublimate and clear off, if you can wait. I'm not sure what your temperatures are.
I believe any de-icing fluid salts CaCl2, NaCl etc. is corrosive to aluminum so I can't see using that.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #15 on: January 02, 2019, 06:52:00 am »
unless its built into the panel you can bypass it.

The danger is a big sheet of ice melting on the bottom and slipping off the solar panel. And water refreezing on your roof.

It would need to be designed well with a heated gutter IMO. All these solutions are labor intensive, complicated or ecologically unfriendly or lead to big productivity losses.

I like the idea of the tracking solar panels, they could be better designed to stand up right if required to clean themselves. 
« Last Edit: January 02, 2019, 06:56:54 am by coppercone2 »
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #16 on: January 04, 2019, 12:05:40 am »
Pretty sure most panels have it built in now days, but guess I'll have to check.  What would be best way, ohm meter at night and see if the reading is the same both ways?  If there's no blocking diode what is the best way to back feed and how much voltage?  Do I just put the same voltage as it's nominal voltage? Same polarity or reverse?  This would be tricky though as I would need a set of fairly heavy duty relays to handle this (disconnect from charge controller and connect to power source), and those might be hard to find.

Think I'll give up for the year though and bring the battery inside.  It's slowly draining from just sitting there. The charge controller probably uses a bit of power on idle.  At least one thing I learned from this is if I was to do an off grid setup I definitely need to account for freezing rain.  Mechanical snow removal is just not enough. 

As a side note I'm apparently too heavy for snow shoes.  Figured I'd save myself the trouble of having to shovel a path to the shed every day and bought snow shoes, but I just sink straight to the bottom.   Too much poutine.  :-DD
 

Offline thibustor

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Re: How do you deal with freezing rain and solar panels?
« Reply #17 on: January 04, 2019, 10:37:47 am »
De-icing liquid is your best bet. But how much power do you get in the winter anyway with the sun being at a bad angle anyway?

Ground deicing of aircraft is commonly performed in both commercial and general aviation. .... Deicing fluids work best when they are diluted with water.

Find more info at - https://infotozo.com/
 

Online Kleinstein

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Re: How do you deal with freezing rain and solar panels?
« Reply #18 on: January 04, 2019, 11:59:15 am »
If there is not protection against back feeding  (likely a MOSFET+driver wired as a kind of ideal diode), one could apply a voltage for heating. It would be a little higher (e.g. 5-10%)  than the maximum voltage to get out. It would need external current control, much like driving an LED (it's much like a near 0% efficiency high power LED). It should be OK up to the current the panel can deliver, probably somewhat more - so the power is kind of limited.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #19 on: January 04, 2019, 12:21:00 pm »
what is the maximum current you can put through a solar panel for a particular wattage as not to create possible hot spots/

also some forums mention a sealing layer which could be tricky to maintain if its used as a heater. i guess control the ramp rate well.

http://www.keisolar.com/automatic-solar-panel-snow-removal/

https://groups.google.com/forum/#!topic/alt.solar.photovoltaic/NJPtTYRKUKY

i imagined a sloped heated gutter, with a thin concave mesh around it, so that when you heat the panels the number one thing you want is for the snow to slide off on a thin layer of water, but so that the water layer is captured by the gutter but the snow does not have a edge to get stuck on as it slides off. this way you could prevent puddles of ice forming on your roof if you need to melt the whole thing. it seems really dependent on the setup though.
« Last Edit: January 04, 2019, 12:36:26 pm by coppercone2 »
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #20 on: January 04, 2019, 12:27:56 pm »
I have found that solar panels can defrost themselves if its not too far below freezing but you get a nice clear sunny day.

There black color does make them soak up the light and get quite a bit warmer than ambient .Some of it gets turned to electricity of course but solar panels still have pretty low efficiency so most of that energy goes to heating the panel. So the sun will warm them up more than sending the rated power back trough them would.

Tho perhaps turning off the inverter and not drawing current from them could help them get even hotter since then you are not taking the electrical energy out if them and likely sending all of that to heat too.
 

Online Ian.M

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Re: How do you deal with freezing rain and solar panels?
« Reply #21 on: January 04, 2019, 12:46:43 pm »
It may be worth giving the ice/snow on them a good sprinkling of soot or finely powdered charcoal to increase the heating from any sunlight they get.  You will however then need to clean them once the ice has cleared.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #22 on: January 04, 2019, 01:02:51 pm »
Id just simply pour antifreeze or winter car window washer liquid(Ehtylene Glycol) over them as suggested above. The stuff is not terribly expensive if bought in a large container at the supermarket and works really well for getting ice to melt.

Tho the effect is not exactly instant, so you may have to pour it in small quantities every few minutes to get all of the ice off.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #23 on: January 04, 2019, 01:07:30 pm »
arent you guys worried about this stuff getting into the dirt around your property, especially if you are doing off grid living and probably have a garden near by.. or kids

i would not want antifreeze in my tomatoes, it just seems like a bad idea. ethylene gylcol is also pretty toxic i think, and you can possibly effect animals and useful farm insects like bees.

is it even legal to pour this stuff on a solar panel. rain-x is nice for a windshield but i dunno if spilling gallons of it on your roof is a good idea.  :-//

plus, applying this stuff is kinda dangerous, if you want to get a ladder while there is snow outside or whatever. so is cleaning it in the winter because its a weird center of mass on a long pole and you can easily slip outside of your house. these seem contrary to safe living off the grid where you are likely far away from a hospital. not sure what  twenty years of using weird pole brooms does to your back as well. might be hard to figure out how to do it ergonomically.

an interesting machine related to back health and cleaning


i wonder what kind of sensor could be used to detect snow. maybe a automotive reflection sensor combined with a mass sensor that basically detects glass obstruction and snow mass.. but i dunno how to isolate that from the wind.
« Last Edit: January 04, 2019, 01:18:45 pm by coppercone2 »
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #24 on: January 04, 2019, 01:20:30 pm »
Well i just squirted a bunch of it all over my windshield and shed it all over the road behind me on my way to work since there was melting snow on the highway and that made the windshield get dirty as heck every few minutes.

According to Wikipedia its illegal to use Methanol in windshield washer fluid in the EU. Probably due to how toxic it is. So the popular alternative has become Ethylene Glycol or Ethanol. Im guessing then Glycol is not as toxic then.

So i suppose if you want to be safe you could dump some 90% Ethanol over the panels. This is essentially concentrated Vodka so if its safe to drink them i'm sure its also safe to pour on the ground. Tho don't actually drink >90% Ethanol as drinking this concentrated alcohol is not safe and the this sort of industrial alcohol has other crap in it that is not safe to drink (Like methanol) or they mix in a chemical that tastes incredibly badly to discourage people from drinking it (Tax for drinkable alcohol is much higher, so they rather have you buy that instead)
 


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