Author Topic: How do you deal with freezing rain and solar panels?  (Read 6835 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.
 

Offline 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 »
 

Offline 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.
 

Offline 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/
 

Offline 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)
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #25 on: January 04, 2019, 01:26:54 pm »
yo there is the concern here that you can blow your roof up if there is a spark while you pour gallons of highly flammable solvent on the roof. this is a bad idea.



it also might end up as a pool of ethanol in front of your house on top of a ice sheet and remain flammable.

an idea for a snow sensor might be two photodiodes on a sloped trough that looks for a optical break, tested to resist heavy rainfall, with a mesh on top to keep out leaves. 
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #26 on: January 04, 2019, 01:30:06 pm »
ethylene glycol is plenty toxic but the thing is it has a low vapor pressure so your not likely to get a dose from inhalation as you would from methanol. it also probably does not absorb well through the skin like very small methanol molecules.

iirc it turns into oxalic acid inside of your body.
https://en.wikipedia.org/wiki/Ethylene_glycol_poisoning

i hate the look of sloped solar panels too, i think it looks terribly unsightly and industrial for a home.
« Last Edit: January 04, 2019, 01:41:08 pm by coppercone2 »
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #27 on: January 04, 2019, 01:55:20 pm »
Yeah don't really want to start using chemicals as it will go on the roof shingles (might react weirdly?) and then on the lawn.  That stuff is basically poison.  Going to kill birds etc.

One thing I've been thinking of, would only really work in an off grid setup where there's not tons of litigation about wood burning, but I could glue pex lines under the panels like a floor heating system, then encapsulate it with rigid foam to insulate it in, and then connect it up to a wood fired boiler system.  Would use glycol as the liquid in a closed loop.   It would not require a huge battery pack like an electric heater or backfeeding would, and still be carbon neutral.   I imagine if I ran the boiler for like an hour or two it might be enough.  Would be a manual process though.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #28 on: January 04, 2019, 01:59:23 pm »
if you insulate the panels then they will run less efficiently when they are hot. i think you actually want to put heat sinks on them ideally to keep the silicon cooler as it works.

maybe if you run cooling through it during the summer, but that is a pump and alot of hydraulics to worry about, and you need some kind of chiller or heat exchanger. all insulation penalizes your heat exchanger because less is radiated.

https://www.civicsolar.com/support/installer/articles/how-does-heat-affect-solar-panel-efficiencies

the equation between visual look, ease of use, safety and efficiency is giving me a headache.

i would want it flat, fluidically temperature regulated, drained and low voltage.

don't forget all the work the pump has to do, in regards to tubing thickness for such an installation. it might be a hidden design nightmare.

and non closed cooling systems i.e. if you decide to mist it in the summer, may come with big concerns in terms of microbiological activity due to the humidity. talk about roof fungus.
« Last Edit: January 04, 2019, 02:11:37 pm by coppercone2 »
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #29 on: January 04, 2019, 02:13:01 pm »
interesting discussion
https://www.solarpaneltalk.com/forum/solar/solar-energy-facts/18035-water-cooled-solar-panels-for-significant-output-boost

and if you never worked with heat exchangers before, their a complete psychotic bitch in terms of corrosion. believers in plating beware. you want it big and smooth and unfortunatly laminar for corrosions sake. think impedance matching so you don't have abrasive particles that bombard flat surfaces used for fluid direction changes.

and keep in mind of visosity of antifreeze agents etc. and poor thermal performance of room temperature freons. and how they leak all over the place where water would be fine.
« Last Edit: January 04, 2019, 02:17:19 pm by coppercone2 »
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #30 on: January 04, 2019, 05:24:20 pm »
Heat would be the least of my worries here, and for a few months of the year when it is really hot, the days are super long (like 4am sun rise and 10pm sun set) so I would have more than enough energy to run a chiller if I had to.   Which would be an interesting thing, as there might be a specific point where running a chiller gets more power than if you didn't run it, but have to find that sweet spot.

Another option might be to air heat them.  Just have  air blast under the panels from the bottom and as the heat rises along the panels it would heat them.  Not exactly that efficient though but in an off grid setting if I'm already using a wood stove to heat the house anyway, I could just pipe some heat to the solar installation or something and just have a damper that opens and pumps air then the return would come back and hit up the wood stove to be reheated again.

For my shed I think any solution might simply not be worth it so think I'll just leave them as is.  Went out again to see if I can skim some snow off but the broom just glides right on top, it's too icy and crusty.  I might eventually get it if I keep going every day though.  I am getting a voltage reading so they are producing a tad, but under 0.1 amps.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #31 on: January 04, 2019, 05:55:28 pm »
Yea there is the issue of ethanol being pretty damn flammable.

If you really want you can always go up there with a heat gun and a scraper to clean the ice off manually, depends on how many panels you actually have, pretty doable for 3 to 5 panels. for 50 panels not so much.

And yes solar panels do loose efficiency when running too hot in the summer, but cooling them is not so easy so its a question if its actually worth it. You have to remember that a pump circulating liquid around the loop does need a fair bit of power to run.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #32 on: January 04, 2019, 06:01:42 pm »
how are you gonna cool your water   ?

keep in mind aerosols and legioneers disease.

and i think they are sealed with some kind of gasket, so be careful not to heat them too quickly or that might effect their moisture seal.
« Last Edit: January 04, 2019, 06:05:46 pm by coppercone2 »
 

Offline CatalinaWOW

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Re: How do you deal with freezing rain and solar panels?
« Reply #33 on: January 04, 2019, 06:18:37 pm »
How about a really old school solution that was used in my youth to stretch the growing season in the garden.

Freezing rain, freezing fog and other similar weather conditions seldom happen without warning.  When the weather report calls for it, put a tarp over the panels.  It can be relatively easily removed when conditions improve. 

This solution works really well for small, ground mounted arrays.  Gets less appealing as array size grows and for arrays mounted high in the air.

If you are so inclined there are a number of ways to automate this process.  Not cheap, but straightforward.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #34 on: January 04, 2019, 06:44:47 pm »
With climate change I find we get way more unpredictable weather here.  Like this freezing rain I  never saw coming.  It was -30's but for maybe an hour it went up to positives enough for it to rain, then back to -30's. 

But yeah maybe I could have an automated system that covers them at night, since night makes up a good chunk of a 24h period here anyway, so statisticly, it should have a good chance at keeping them clear. 

More I think about it, for the shed I won't worry about any solution as they all seem quite complex, not worth it for 400w.   But if I do the house I will want to keep solutions in mind.  Especially because it will be too high to reach manually so even for just regular snow removal it will need to be automated. 
« Last Edit: January 04, 2019, 06:46:25 pm by Red Squirrel »
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #35 on: January 04, 2019, 07:13:19 pm »
It was -30's but for maybe an hour it went up to positives enough for it to rain, then back to -30's.
Is that Celsius degrees or Freedom degrees?
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #36 on: January 04, 2019, 08:37:23 pm »
It was -30's but for maybe an hour it went up to positives enough for it to rain, then back to -30's.
Is that Celsius degrees or Freedom degrees?

Celcius
 
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Offline ahbushnell

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Re: How do you deal with freezing rain and solar panels?
« Reply #37 on: January 05, 2019, 01:20:23 am »
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)
Ethylene Glycol can kill dogs.

https://healthypets.mercola.com/sites/healthypets/archive/2014/11/23/antifreeze-poisoning.aspx
 
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Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #38 on: January 05, 2019, 10:00:53 am »
Well its very toxic to humans too but we tend to be smart enough to not drink antifreeze since its only really toxic when you eat it.

Tho that has not stopped some rather shady people adding it to wine because it made it taste better. Not sure how many people died from it before they found out whats in the wine, but id imagine it was quite a bit more than zero.
 

Online Ian.M

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Re: How do you deal with freezing rain and solar panels?
« Reply #39 on: January 05, 2019, 10:47:40 am »
Oh for <expletive>'s sake, if you care in the slightest about the environment, small kids, your neighbour's pets, etc, get RV (Propylene glycol) antifreeze, if there's going to be any significant amount intentionally lost to the environment.  Its far far less toxic, and wont turn your yard into a superfund site.
 
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Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #40 on: January 05, 2019, 01:48:10 pm »
Oh for <expletive>'s sake, if you care in the slightest about the environment, small kids, your neighbour's pets, etc, get RV (Propylene glycol) antifreeze, if there's going to be any significant amount intentionally lost to the environment.  Its far far less toxic, and wont turn your yard into a superfund site.

Ah i had no idea that stuff is actually safe enough to eat. So why is it not so widely used as the popular ethylene glycol? Does it not work as well? Or is it simply more expensive.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #41 on: January 05, 2019, 04:13:55 pm »
you can get propelyne glycol cooling fluid mixtures. not sure why its not used in cars, most likely cost. its also possible it might be some what more prone to sustaining some kind of growth.
 

Offline edpalmer42

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Re: How do you deal with freezing rain and solar panels?
« Reply #42 on: January 05, 2019, 05:37:44 pm »
Why not use the ice melting cable that you put on the eaves to melt ice dams?  It would cover a small percentage of the panel, but if ice is a big problem, you would come out ahead.  You might have to space the cable more closely than usual since you're trying to clear the entire panel rather than just opening up channels for the water to run off.  Experimentation would be required.

https://www.canadiantire.ca/en/pdp/roof-de-icing-cable-0522580p.html

Ed
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #43 on: January 06, 2019, 12:50:03 am »
Yeah was thinking about that.  Issue is the amount of heat required would use more power than I would generate for days.    But I guess it's better than not generating at all for more than half the season. Just need a much bigger battery bank.  80ah won't cut it. Worse case scenario I use grid power, in an off grid setting with more land then I would have room for a better system like wood fired boiler etc.  That  and a better tilt angle.  Probably do two vertical arrays, east and west, and then south that is at around 45 degrees.  I need to optimize the system for winter as that is the majority of the season so even if tilt is not optimal in summer the days are longer I'd still get lot of power.

I managed to chip away at it from the ladder with a snow shovel while being careful not to damage them.  This is not just snow it's crusty/icy snow so it does not come off very easily.  It's hard to tell from the pic as it just looks like normal snow.




 
Managed to get some cells exposed at least.

What I'm thinking is either trying those heat cables on top of the panels as suggested, or come up with some custom heat pads of sort using nichrome wire driven to a certain temperature (would put temp probe in it) and stick them under the panels.    I wonder if I could get away with just heating the bottom part of the panel at a high enough temp like 30C and that might naturally gravitate towards the top through the cell material.  Guess I'll have to experiment.

I'd have to upgrade my inverter and battery bank though to run stuff like this.  At least if I get something like this to work I know it will be semi viable if I do the house as I would have a much larger battery bank and inverter.  Though looking at what I'm dealing with now I'm a little worried ice damming may be an issue, so don't even know if I want to do the house anymore.  Better off waiting till I can get a bigger property then do a proper ground mount system.
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #44 on: January 06, 2019, 01:14:50 am »
I did some googling to see if someone had a solution here where we also have a lot of snow. Most people recommend you don't remove snow in the winter since walking around on an icy roof is not exactly safe and the power from the solar panels are so low that it is not worth the risk anyway. If you live in southern Canada that is further south than Sweden so you might have more daylight during winter. The recommended way to minimise the problem is to mount them at a steeper angle, while there is snow on the ground it can even be beneficial to keep them vertically since the snow will then reflect light onto the panels.
« Last Edit: January 06, 2019, 01:18:46 am by apis »
 

Offline edpalmer42

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Re: How do you deal with freezing rain and solar panels?
« Reply #45 on: January 06, 2019, 01:23:22 am »
Just remember that you don't have to run the heating cable at full power - use a light dimmer to control the power.  Also, it might help if you turn the cable on when the storm starts to prevent the kind of buildup that you're dealing with now.

Are you in an area where you deal with the 'Lake Effect'?  For those who don't know, near the Great Lakes the wind picks up huge amounts of water off the lakes and then dumps it as snow or freezing rain.  One storm can easily drop a meter of snow or a centimeter or two of solid ice on things like streets, power lines, or solar panels.  Kind of means that the entire area is 'off grid' for days after a bad storm!  :(

Ed
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #46 on: January 06, 2019, 01:29:40 am »
Yeah I had googled this too I'm surprised there really isin't any real solutions.  Business idea perhaps if I come up with something...  At very least I do want to come up with something for normal snow.  Thinking some kind of brush that rides on a rail and it just sweeps the whole array. It would be manually operated remotely by looking at the array through a web cam.  Though it could be automated, just best to watch it do it's thing in case it gets caught up or something.  Once I finally build out my shop and add hvac, I'll be able to actually have a place to organize and setup all my tools etc and experiment with projects like this.

I'm thinking a better tilt is the best way though.  Could pretty much do a west/east vertical mount, and a south 45 degree mount.  The south one would just be a write off in winter, in summer it would add extra power to run A/C.  Though could possibly use power from the west/east one to try to melt snow off the south one. 

 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #47 on: January 06, 2019, 01:31:42 am »
Just remember that you don't have to run the heating cable at full power - use a light dimmer to control the power.  Also, it might help if you turn the cable on when the storm starts to prevent the kind of buildup that you're dealing with now.

Are you in an area where you deal with the 'Lake Effect'?  For those who don't know, near the Great Lakes the wind picks up huge amounts of water off the lakes and then dumps it as snow or freezing rain.  One storm can easily drop a meter of snow or a centimeter or two of solid ice on things like streets, power lines, or solar panels.  Kind of means that the entire area is 'off grid' for days after a bad storm!  :(

Ed

No lake effect as I'm further north from the great lakes, but we USED to get tons of snow here, now we get a few feet at most, but our weather is so sporadic.  More freezing rain and other crap like that.  The normal snow is not too much of an issue I just use a long broom, like this:



(first few seconds of the video shows it quickly in action)
 

Offline duak

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Re: How do you deal with freezing rain and solar panels?
« Reply #48 on: January 06, 2019, 02:38:00 am »
I'm in Vancouver, and a couple of years ago we got a bunch of snow then rain that soon became heavy ice.  I usually sweep the snow off a fiberglass canopy over the deck but I was under the weather so I didn't.  The canopy has an access hatch but because of the ice I couldn't open it.  I rigged up a shower head on the end of a pipe and set it to spray hot water to at least free the access hatch.  It worked but it was slow.  The forecast was for sun but not all that much warmth so I spread some black poly film on the ice.  It actually worked quite well as the white snow and ice are much more reflective than the black poly.

Best o' luck
 

Offline richard.cs

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Re: How do you deal with freezing rain and solar panels?
« Reply #49 on: January 06, 2019, 11:59:23 am »
In the UK I'm pretty sure all screenwash is ethanol with non-methanol denaturing. I think methanol is legally out because it's toxic by inhalation and generally we don't like throwing ethelyne glycol everywhere. Propylene glycol could be used in screenwash but I don't think it's common.

In terms of deicing, I would probably be inclined to try heating the panels directly with a current source. If the cells are just in series then putting their rated current in should be completely fine. In fact putting 10x their rated current in is unlikely to damage the *cells* because the heat generated will be similar to the sun shing on them (assuming 10% efficiency or so). That's not really reccomend however because the interconnects between cells and the metalisation on the cell surfaces will not be designed for it.

In an ideal world I'd try it on a non iced panel in the summer and keep an eye on it with a thermal camera to determine what current is safe, then use that current the following winter. As that's not possible then sticking to ratings is better.

With parallel strings of cells the temperature coefficient means they won't share well. If you put the rated current for a single string in to the whole array it will be safe however, but most likely only a single string will deice. I initially thought that sun shining on that one string with the inverter off would shunt current into the others, but I don't think it will actually as it is the lowest voltage string (and lower still as it will be hotter from the sun) so that current will just circulate locally.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #50 on: January 06, 2019, 12:16:10 pm »
keep in mind the moisture seal. if you pump lots of amp into a frozen panel it will expand fast and possibly break a moisture seal. ramp it..
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #51 on: January 06, 2019, 12:16:18 pm »
To lower the peak power consumption you could only turn on the heaters on one panel at a time. You only need to briefly get the panel above freezing to get the ice directly touching the panel to melt. So focusing all the available power to heat up one panel quickly is likely more energy efficient than using that same amount of power spread out to heat all of the panels slowly. The panels will be loosing heat to radiation and convection all trough the heating process, so the faster you heat it the less heat escapes into the environment rather than being used to change the ice back to water.

I would imagine you would need at least 1kW of heating power per panel to defrost it in a matter of minutes. Taking the worst case of 10 minutes to defrost you are looking at 0.17 kW/h of energy to defrost one panel. So its not that terrible.

Tho im not sure if you could heat the panel up with 1kW by reverse feeding power into it so you likely need to cover the back of the panel in self adhesive heating pads. But from the energy standpoint it probably makes sense to use energy to defrost them, its more of a question if the cost of the heating elements and extra wiring is worth the extra energy production (Especially since solar panels don't produce a whole lot at winter in these areas)

EDIT: By the way the defrosting here is only considering melting the ice directly touching the panel so that the rest can get unstuck and slide off by gravity. If the panels are not at enugh of an angle or the edges stick down too much you might still need to go up and nudge it to get it off. Melting all the ice and snow into water would require a lot more energy.
« Last Edit: January 06, 2019, 12:21:31 pm by Berni »
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #52 on: January 06, 2019, 04:39:38 pm »
If the panel is about 0.5 m2, a 1 mm ice sheet would be about 0.0005 m3 which is ~0.46 kg of ice.
Latent heat of fusion for water is 334 kJ/kg, so it would require about 153 kJ to melt it.
The heat capacity for ice is about 2.05 kJ/(kg*K) so you need about 940 J per degree C.
So if it's -10 degree when you start you need about 163 kJ to melt it. At 1 kW that takes 163 seconds or a little less than 3 minutes assuming perfect heat transfer. In reality you'll loose a lot of heat to the rest of the system, so you can probably expect 10 min or more at 1 kW per panel.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #53 on: January 06, 2019, 05:21:30 pm »
I think solar panel modules for large roof installations are usually about 1 to 2 m2 in area.

And yes it heavily depends on how much heat is lost to the environment. If you are loosing so much heat that you don't even reach 0°C then even leaving it running for a whole day wouldn't defrost it, hence by having a lot of power is important.

For example one way heat loss could occur is black body radiation. Glass and ice have a emisivity constant reasonably close to a black body(>0.9) and in such a case rising it 10°C above ambient on a 1 m2 panel would radiate off about 350W of heat. However the solar panel also has 2 sides do it so the bottom will also radiate just as much adding another 350W. But it gets even worse. Solar panels generally are pointed towards the sky and the atmosphere lets a lot of the infrared radiation pass out into space where it never returns. This makes the sky appear colder than the air temperature because its taking in more infrared radiation than it is radiating back. For this reason your car windshield can sometimes freeze even if the air temperature never goes below 3°C. The temperature varies a lot with atmospheric conditions but its usually about 10 to 30°C lower than ambient air. This could increase the heat power radiated off the front to rise above 500W bringing the total to 850W just due to radiation. However the smart thing is to do this on a sunny day where the sun provides you with an extra 200 to 400W of heating power for free. Covering the back of the panel with a low emisivity material such as polished aluminum could drop radiated loss on the back to as low as 11W. So depending on your setup and conditions the radiated heat loss alone is between about <50W (insulated back on a sunny day with favorable atmospheric conditions) to 850W (no insulation, at night)

The other major form of heat loss is trough convection. This could again vary a lot, i would imagine on a windy day you need >1kW just to overcome this heat loss.

So yeah 1kW per panel seams like it is the absolute minimum needed to defrost a panel in favorable conditions.

EDIT: Actually i got my numbers wrong for the solar irradiation. A sunny day can bring you about 600 to 1300 W/m2 of power.
« Last Edit: January 06, 2019, 06:08:56 pm by Berni »
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #54 on: January 06, 2019, 05:51:40 pm »
Yes. If you are lucky and there's a bit of "snow insulation" on top and around the panels that can probably help a lot. Worst case would be a thick layer of ice during a clear, cold and windy night.

I wonder if you couldn't put a sheet of transparent plastic on top of the panels. Then you remove the plastic and shake off the ice. Might require a bit of work to create a setup that is convenient. You would loose a little bit of efficiency of the panels but probably not too much and you only need it while there is risk of ice (not sure how much light a plastic sheet would block). Building plastic is pretty cheap.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #55 on: January 06, 2019, 06:23:22 pm »
Actually i did a bit of a miscalculation. Turns out you can get over 1kW just from a sunny day alone.

So if you are going to get a clear sunny day with no wind and -10°C ambient perhaps the only thing you have to do is get all the snow off it so that the panel can absorb most of the energy rather that just reflecting the light back into space.

We are going into the 2nd winter with our 38 panel array and so far we never had problems with ice and show. Yes the array produces very little power when snow covers it but we tend to soon enugh get a nice sunny day that warms things up enough for the snow so start sliding. Once one part starts to slide it tends to trigger all the rest on the same array with it making for a loud booming avalanche of snow suddenly coming down from the roof and revealing perfectly clean panels that once again start making proper power. The area in front of that array is not a place where people hang out, or anything of value is stored so we don't care about the sudden snow mountain appearing there, we have not installed any snow braces on purpose so that the snow would slide.

But if we get freezing temperatures flowed by rain im sure we could get into a similar problematic situation.
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #56 on: January 06, 2019, 06:34:28 pm »
On a clear day you get about 1 kW/m2 perpendicular to the sun, so a panel would always get less than that from the sun, but a few hours of that might be enough if it isn't too cold and windy. The problem is that a layer of snow on top of ice would reflect away most of that solar energy (otherwise the panels would continue producing electricity as well).
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #57 on: January 06, 2019, 07:48:11 pm »
Yeah I always figured the rule of thumb was around 1 kw of energy per square meter of sun light.  Of course that changes based on various conditions etc.  But if THAT does not melt snow (which it does not, hence why snow stays on the ground) then it means I need more than that to melt snow on the panels.  Though think I will indeed experiment with heating 1 panel at a time using a couple kw of ramped up heat.  Since I only need to melt under the ice and not the entire ice maybe it is indeed doable.  Something I can experiment with next year.      If this works and my only limit is battery capacity then suppose it's not a big deal to get like 4 or 8 golf cart batteries in there.   Can never oversize a battery bank, in fact for solar it's probably better, since if I'm always riding on 90%+ capacity it means they will last longer.

We have actual sun today - like actual direct sun light, which is very rare.   I went out a while ago to clear off the snow from overnight (still crusty snow left over, just skimmed the top soft snow) and I'm actually getting around 5 watts which is not bad considering they are pretty much all covered. It's at least enough to put a bit of charge in the battery.  With this sun light, maybe it will indeed cause the panels to heat up and then start melting the ice.   

But yeah think for a small array of this size where I don't have much property to do anything special like a ground mount setup that is tilted better, my best bet is to probably just experiment with ways to heat them.  Whether I do backfeeding, or put some nichrome wire on the back.   What is the best way to insulate nichrome wire, is there any kind of sleeve that is meant for that?  I'm thinking next summer I will look into putting nichrome wire on the back of the panels and then I can switch them individually.  I still need to design and build the control system anyway, like I want a voltage monitoring system and energy tracking system and what not, just have not gotten around to doing it. I can do the heating with that system too.  Basically just have a bunch of relays controlled by arduino.  Will do outside lights and stuff too.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #58 on: January 06, 2019, 08:44:04 pm »
Well more of the problem is that snow is really good at reflecting light. It can reflect 80 to 90% of light so that brings your 1000W/m2 down to only 100W/m2, the rest is just sent back into space. Perhaps once the snow is cleared away the crusty ice under it would not be as reflective so more of the light would end up absorbed to help heat the panel.

Snow is also very insulating so when it does get hot enough to melt only the very surface of the snow melts, the inside is protected by the insulating properties and the heavily heat consuming melting process keeps the outside edge from ever rising above 0°C. But if you want to melt snow on a cloudy day by heating the panel this could be a great advantage because the snow is insulating the panel from the cold sky and protecting it from wind. Helping you get that very bottom layer of ice to melt so the rest slides off the roof. But still i think you will need 1kW to do the job efectively and efficiently.

I would not recommend back feeding this much power into a panel as its way above the rated current. Nichrome wire is an option, you don't really need to insulate it, just make a pattern that never crosses the wires and use some sort of selfadhesive film material to stick it down to the back side of the glass solar panel. Ideally you want to snake the wire back and forth many times as one length of wire to spread the heat and minimize the number of wire joins required. It might actually become so long that it makes more sense to use copper or aluminum wire, since nichrome might need to be unpracticaly thick to have low enugh resistance to draw 1kW. You will also want to use a fairly high voltage to run it since 1kW at 12V needs 83A and that needs rather beefy cables.

One alternative are also silicone heating pads:
https://www.alibaba.com/product-detail/electric-water-boiler-heating-element-silicone_60471551007.html?spm=a2700.galleryofferlist.normalList.210.46e46a55Ofpbic
They aperantly make even massive ones that are 1x3m in size and rated at 13kW
So perhaps you can find ones that are about the right dimensions for your panels and stick them to the back. Or perhaps use one of them them as a temporary heating blanket that you manually go place on a panel and turn it on for a while to melt it before taking it off again or moving it to the next panel.

 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #59 on: January 06, 2019, 08:50:40 pm »
The problem with the sunlight and snow is that snow can reflect as much as 90% of the energy. And the 1kW is for a surface perpendicular to the sun. Where I live the maximum sun-ground angle was 12 degree today. I think that means the ground gets sinus(12)*1kW/m2 =  200 W/m2, and if 90% of that is reflected it leaves 20 W/m2. Not nearly enough to melt the snow.

If you have a heater in direct contact with the panels you transfer the heat through conduction, not radiation, so most of the heat will go into the solar panel and the ice and snow on top of it (if the conditions are right as Berni pointed out). It still takes a lot of energy to do that though.

If you want to try heating them maybe something like floor heating wire would work:
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=Underfloor+Heater+Cable&_sacat=0
« Last Edit: January 06, 2019, 08:52:13 pm by apis »
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #60 on: January 06, 2019, 09:26:41 pm »
Yeah true I guess with the reflective properties the snow is not actually absorbing 1kw so that's why it does not melt.  Actually that would make for a neat experiment, if you simply spray paint snow black it would probably melt. Not that I want to go spray painting the snow on my panels but it would maybe work! lol

But yeah maybe playing with infloor heating wire, or nichrome wire is best bet can then tape it behind.  Just need a tape that won't unstick with the heat/cold cycles. 

Something to try next summer. 
 

Offline bicycleguy

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Re: How do you deal with freezing rain and solar panels?
« Reply #61 on: January 06, 2019, 11:46:36 pm »
Although I now live in sunny southern California I did my time growing up in Wisconsin.  We used to make huge snow and ice forts.  Surprisingly the easiest way to burrow holes for vents or spying was with a garden hose and whatever the tap water temp was at the time.  Solid ice won't cut, but for regular snow plain water can do wonders.  It takes a lot of heat loss to freeze water.  The solar panel glass can't absorb much and the snow has no mass.  For a one time job, I think it's doable.

Of course you can screw-up, but the way your pictures looked, and if say >20F I think you'll be surprised.  The closer you can get the better.  Keep an eye on where that cold water is going.  Any puddling on the roof is a show stopper.  Start at the gutter and keep a flow and work your way up a panel.

Try it on your car first to get a feel for how it works and whether it's too cold out.  Make sure you have somewhere for the water to go or you'll regret it.  We used to pull a hose out of the basement laundry room.  Of course don't use an outside faucet without a way to drain it!
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #62 on: January 07, 2019, 06:43:02 pm »
Would go well if I want to have a hockey game on my solar array.  :P The water comes out the faucet at around 0-1C so I would need to heat it up first.  Though I guess that would work.  Think I'm going to lean towards the heat tape though, might just throw it on top and plug it in to the house for a day, at least just to get it going.  For future I'll want to come up with something more self sustainable like the nichrome wire under the panels. 
 

Offline bicycleguy

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Re: How do you deal with freezing rain and solar panels?
« Reply #63 on: January 07, 2019, 07:19:07 pm »
Obviously you didn't try it.  Take a pail of that cold water and poor a steady stream onto the snow in the yard and see how far it goes down.  I'll be surprised if you can't see grass.  If it was that quick to freeze you wouldn't need a Zamboni.
« Last Edit: January 07, 2019, 07:23:53 pm by bicycleguy »
 

Offline edpalmer42

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Re: How do you deal with freezing rain and solar panels?
« Reply #64 on: January 07, 2019, 07:48:51 pm »
Three more random ideas....  Implementation details are to be determined.  ;)

Ice melting pellets that you normally put on the sidewalk?  I don't know how expensive or toxic they are, but they seem to be used a lot.

A black 'window shade' that you pull down over the panel.  When not in use it would be rolled up like a normal window shade or run around to the back of the panel to keep it from getting covered with snow.

If you decided to put hoses on the back of the panel for heating and cooling, you might be able to do the cooling for free.  Put a check valve on both ends of the panel so that fluid can only go one way.  When the fluid heats up, it pushes out in the only direction it can go.  But since it's in a sealed system, that pushes cool fluid in from the other end.  You've got pumping action without a pump.  Automotive block heaters that are installed in the heater hose use this idea.  Now add something like a car radiator to cool the fluid just with passive air flow and you're done.  I don't know how much heat you could remove with a system like this, but it wouldn't be too hard to set up if you've already got the hose in place.

Ed
 
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Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #65 on: January 07, 2019, 08:02:48 pm »
careful with solutions so you don't get debris or animals making flammable structures in heating systems.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #66 on: January 09, 2019, 07:56:50 pm »
Oh yeah would not really have any temps that are hot enough to ignite stuff.  Maybe like 40C at most at the actual heat wire.

We just keep getting dumped with snow now so pretty much given up for the year.  I still go out in snow shoes to take it off as the weight might crack the panels but no way I'm getting down to the glass this winter.
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #67 on: January 09, 2019, 09:46:03 pm »
Locally I see many household solar arrays covered in snow. For some it rolls off and others people brush it off. It depends on the angle. I actually use 90 degrees for small (a couple hundred watts) and it works fine, if the tree line is not too high. Applying car wax on the panels helps the snow/ice slide off, like ski wax.
There are blocking diodes in all larger panels so injecting current would not heat up the cells I reckon.
 

Offline coppercone2

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Re: How do you deal with freezing rain and solar panels?
« Reply #68 on: January 09, 2019, 09:50:32 pm »
are they like integrated into the panel or maybe you can put a relay across it?
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #69 on: January 10, 2019, 01:51:54 am »
Pretty sure they are integrated, probably in that black box where the wires go in, though it might be possible to open it and just bypass the diode?  But don't think I'll go that route though, I'll have better heat control if I just use a separate source of heat, and bonus is the panels will begin to produce right away as I won't be messing with their connectivity to the charge controller.  I can set the logic of the melt system to move to the next panel as soon as it sees a spike in power production as it means everything slide off.   Though I might not bother going that fancy, just stick a web cam so I can watch it and switch manually.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #70 on: January 10, 2019, 06:39:20 am »
I don't think you need to disconnect the bypass diode.

The diode basically prevents the voltage across the terminals from going negative (Or at least under -0.7V) when the panel is in the dark but others are not. To push power into the panel you want to provide a voltage into it that is higher than the voltage it would produce from light. This turns the solar cell elements into a forward biased diode. This region of operation is probably a lot like a LED where the current has to be regulated. Except i don't think a solar panel can produce any light (Maybe it produces IR light?), just heat like a normal diode.

But in any case i don't think its a good idea to back feed the required 1kW into a solar panel that is rated for 200W, the interconnects might not be up to the job or the parallel cells perhaps don't current share very well. Perhaps hotspots can occur inside one of the cells? In any case i would first test this on a smaller panel and a thermal camera to see how well the heat spreads on a back driven panel.

Sticking heating elements to the back is likely easier anyway.
 

Offline duak

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Re: How do you deal with freezing rain and solar panels?
« Reply #71 on: January 13, 2019, 06:17:33 pm »
Photovoltaic cells are forward biased when operating.  That's why each cell only contributes 0.6 V or so.  If the cells had a greater barrier potential, say like GaAsP at about 1.5 V, you'd need fewer cells.  The bypass diode would have to be bypassed itself to get anything other than photocurrent to flow.  Shortling out the panel shouldn't cause any damage and will cause any photocurrent to be converted to heat right at the panel.

Last year I had some ice frozen on the back steps.  They are oiled cedar and I didn't want to scrape them too hard so I used an old electric iron set to low heat to melt thru the ice.  Worked great - Not energy wise, but this was a safety issue.

Auto windshield de-icers contain alcohols of various types but they can and do cause aluminum to corrode.  Be careful if using any salts, especially alkaline, as it will attack anodized aluminum.

Cheers,


 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #72 on: January 17, 2019, 10:31:42 pm »
We have some sun in the forecast in the next few days so I'm going to try to get up earlier in the morning to go skim the overnight snow off.  With full direct sun all day, and -30's they might actually produce enough power to heat up on their own and melt the ice.  I'll see what happens.  The battery is reading -15 just now and it's at 12.7v so it's actually still holding a charge.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #73 on: January 18, 2019, 05:59:58 am »
Its -30°C there? Well the sun is going to have its work cut out for it then.

On and at -15°C careful that you don't drain your battery too much since lead acid cells freeze a lot easier when discharged and must not be charged back up until they are thawed out again.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #74 on: January 18, 2019, 01:42:07 pm »
Yeah been keeping an eye on battery and it seems to keep itself charged even through the snow/ice, surprisingly.  I get about 5-10  watts on a good day. 
 
Eventually I want to setup a microcontroller and raspberry pi to monitor everything and run fibre to it so I can monitor remotely.
 

Offline Seekonk

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Re: How do you deal with freezing rain and solar panels?
« Reply #75 on: January 21, 2019, 03:24:22 pm »
Sometimes I wonder if the monitoring systems don't draw more than what is generated.  We just had an ice storm and the weather was still in the teens.  Surprised at how much was being generated and the ice melted in about 2 hours.  If sun can't melt the ice there isn't much to be gained.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #76 on: January 21, 2019, 11:53:29 pm »
Lol yeah if I go ahead with the Arduino and RPI I do wonder too if it would end up using more power than it produces just for the sake of monitoring itself.  The nice part though would be adding the logic to turn the inverter on/off automaticly.  Right now it's just off period. 

Either way if I do plan to run any load on this I will need to do the ice melt system and add more batteries (to power the ice melt system). 

We've had a couple days of solid sun now but because of the snow/ice crust it's simply not producing enough to generate any significant heat at the cells on it's own.  It's been around -30 or so which does not help but that's the only time we get sun.  Once it gets warmer than say, -20 then it's overcast and probably snowing.

The days are starting to get longer too, there was sun till around 5:30 today. 

I think moral of the story is really the easiest way to go for an off grid setup would probably be to have vertical solar panels.  I think what I would do is setup 3 arrays, east/west ones that are vertical, and then a south one that is not.  Up until the point we get the first freezing rain of the year all 3 would produce.  After that only the two vertical ones would produce.  I would want to size everything so the 2 arrays can run everything needed.  In the summer months I would have tons of excess power which means I could just run A/C all day.   Could do a convoluted setup with liquid glycol heated by a wood boiler but probably more complicated than simply having a vertical array.

Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning.  By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #77 on: January 22, 2019, 06:27:33 am »
Yeah a RPi will eat way too much power for monitoring. But a properly designed microcontroller solution can use a few miliwatts of power(Or even 10s of microwatts average). The power hungry part is any sort of long range radio link.

I guess where you live its simply too cold for the sun to do anything to the ice. It tends to get down to -15°C here on a normal winter and i find even that pretty damn cold, everything is frozen solid.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #78 on: January 22, 2019, 02:59:58 pm »
Yeah the RPI would be so I can get network connectivity to the arduino, ex: web page showing info etc.  Probably setup a web cam so I can look at the panels remotely too.  Not sure if arduino is fast enough to do ethernet directly.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #79 on: January 22, 2019, 05:04:27 pm »
If nothing else there are the old SPI to Ethernet chips that let any MCU talk to the world. As for direct Ethernet i been using a STM32F MCU with built in Ethernet RMII interface and could get simultaneous saturated 100Mbit in and 100Mbit back out traffic without the MCU working up a sweat.

But Ethernet by itself is not very power efficient as any piece of networking equipment (Even just a switch) to provide a working LAN will use about as much power as a RPi.
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #80 on: January 22, 2019, 06:30:07 pm »
Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning.  By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
If you have a ground mount system couldn't you mount it so you can adjust the angle. It could be between only two states even; vertical for winter and some lower angle for summer? You would only have to adjust the angle twice per year.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #81 on: January 23, 2019, 12:39:31 am »
Would probably also want to automate the snow removal but really if I was to do a ground mount system it would not be a huge deal to do it manually every morning.  By the time I actually want to live in an off grid situation it will probably mean I don't have to work, so not like I'd be rushing to get somewhere.
If you have a ground mount system couldn't you mount it so you can adjust the angle. It could be between only two states even; vertical for winter and some lower angle for summer? You would only have to adjust the angle twice per year.

Yeah definitely an option too.  A full tracking system would be pretty neat too.  Probably start with a static system as I'd only be using the property in summer at first, then can grow from there and keep adding modules and getting more complex with moving parts etc.   The strong winds we sometimes get here add some complexity as any mechanical parts need to be strong enough to handle it.   

I kinda have something figured out in my head too, east/west vertical arrays that are mounted right on the wall of a building, this building would house all the power stuff and have overhangs that protect the panels from freezing rain (unless it's driving... but at least it would only get one side).  Then an inclined south one against the south wall of said building.  Everything all tied in together built for strength. 

Actually that's another thing too on an off grid property I'd have room for a wind turbine, so probably build one of those too for excess power in winter. 
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #82 on: January 23, 2019, 06:23:10 am »
Yeah being at such a high latitude in Canada probably makes near vertical arrays a good idea.

Over here its actually more efficient to have a panel laying completely horizontal when compared to completely vertical. Especially since the sun in summer is high in the sky and that's when you produce the most (Tho its only a good point if you give power back to the grid as you will likely be overproducing in summer)
 

Offline cologneled

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Re: How do you deal with freezing rain and solar panels?
« Reply #83 on: January 23, 2019, 10:50:30 am »
it was electrodacuas thread about pv cheaper than natural gas, he actually says its 60 degrees in the text, here is the pic,
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #84 on: January 23, 2019, 10:02:10 pm »
Vertical is not so bad in the north during winter when there is snow because the snow cover reflects a fair amount of sunlight into the solar panels. Without the snow its better to have it at some angle, the optimum angle depends on latitude.
 

Offline Doctorandus_P

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Re: How do you deal with freezing rain and solar panels?
« Reply #85 on: February 03, 2019, 02:40:13 pm »
If the panel is about 0.5 m2, a 1 mm ice sheet would be about 0.0005 m3 which is ~0.46 kg of ice.
Latent heat of fusion for water is 334 kJ/kg, so it would require about 153 kJ to melt it.
The heat capacity for ice is about 2.05 kJ/(kg*K) so you need about 940 J per degree C.
So if it's -10 degree when you start you need about 163 kJ to melt it. At 1 kW that takes 163 seconds or a little less than 3 minutes assuming perfect heat transfer. In reality you'll loose a lot of heat to the rest of the system, so you can probably expect 10 min or more at 1 kW per panel.

You wont have to melt it all.
Just a thin layer of water between the solar panel and the rest of the ice is enough, especially if combined with some mechanical force maybe a broom or compressed air into the boundary layer.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #86 on: February 04, 2019, 02:17:54 am »
Yeah I imagine if I could get a thin layer of water to form then the rest could slide off, either with help or on it's own.  Though still going to take a decent amount of energy to do that, as that thin layer is going to be cooled off by the ice on top so need enough heat for the water to stay as water and not just cycle back into ice.    I kind of gave up for now though, went up there a couple times trying to scrape some of it off, but it's a really hard crusty/icy snow, it's not even a solid sheet of ice it's just all messed up. 

Sometimes we get some warm days in March and April, so I think I'll just wait till then and then try to chip away at it again on a warm day.   I may experiment with the nichrome wire idea though.  I should probably try to get on that soon using a piece of cardboard or thin plywood as a test medium as a proof of concept.  Then I can pour water on it and throw snow on it and cycle that a few times and try to form a crust like on the panels, then see if I can melt it from below while measuring the amount of energy I'm using.  That would determine the size of battery I would need if I want to do this without using grid power.

Probably end up just giving up on the idea though, basically I have to ask myself how much effort and money I want to put into a shed's power system.   Though if I did get this going where I can run stuff off it year round it would act as good backup power.  With a bigger inverter I could even run my furnace for a bit, if we get a big blackout.  Or at very least charge up flash light batteries, phone etc, and keep the wifi going.
« Last Edit: February 04, 2019, 02:22:34 am by Red Squirrel »
 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #87 on: February 04, 2019, 07:31:40 pm »
If the panel is about 0.5 m2, a 1 mm ice sheet would be about 0.0005 m3 which is ~0.46 kg of ice.
Latent heat of fusion for water is 334 kJ/kg, so it would require about 153 kJ to melt it.
The heat capacity for ice is about 2.05 kJ/(kg*K) so you need about 940 J per degree C.
So if it's -10 degree when you start you need about 163 kJ to melt it. At 1 kW that takes 163 seconds or a little less than 3 minutes assuming perfect heat transfer. In reality you'll loose a lot of heat to the rest of the system, so you can probably expect 10 min or more at 1 kW per panel.
You wont have to melt it all.
Just a thin layer of water between the solar panel and the rest of the ice is enough, especially if combined with some mechanical force maybe a broom or compressed air into the boundary layer.
That is why I made the calculation for only a thin (1mm thick) sheet of ice. Water has a huge latent heat of fusion as well as a large heat capacity so it takes a lot of energy to melt.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #88 on: February 21, 2019, 02:41:29 am »
Been trying to stay on top of clearing the snow as best as I can, the layer of crusty snow remains but they still produce enough to trickle charge the battery.  Beats trying to carry the battery to the house while on snow shoes.

Today was a very warm day, and some of it has actually started to melt.  I have maybe about 30% panel exposure on all 4 modules now. 

Went on the house roof to shovel some snow off, and came to the conclusion that solar on my house is just not realistic though.  Just too much snow to deal with.  Going to wait till I eventually buy an off grid property, then I can do a proper ground mount system that is vertical or at least tilted very steep.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #89 on: February 21, 2019, 06:08:23 am »
Yeah your location is probably not the best for solar in general since when the panels do work they don't get a lot of sunlight per day.

Got nicely warmed up here in the past weeks, been outside in a T shirt.
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #90 on: February 22, 2019, 05:35:43 pm »
How about trying a hammer and taping in the ice to break it? 
I would not try the chemical as they will cause corrosion especially to connection joints for the wires. 
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #91 on: February 23, 2019, 03:12:34 am »
Kinda sketchy going up there or trying to use a ladder at this point.  Would not want to use any kind of brute force though to risk damaging the panels.

This is how they looked like last time I went there.  We got another 20-30cm of snow since though with another 40cm or so on the way and have not had a chance to go back out there.



If curious this is what the side of the house looks like after I shovelled part of the roof:



They are announcing freezing rain now so back to square one after that.  |O

But yeah if I want to live off grid I'll want to have them on a ground mount system and have them tilted mostly vertical.   Though with a big enough property I'd also have room for a wind turbine and I'd probably want a backup generator to top up batteries.
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #92 on: February 23, 2019, 06:35:06 am »
Where's your house?  All I see is snow.  Where I live we just visit the snow, we don't live in it.
I do see your issue.  And I suppose you have a layer of ice on the panels.

For someone who does not live in the snow, can I ask some dumb questions?
You shoveled the snow off the panels, correct?  And there's a layer of ice covering the panels?

If you did nothing, when would things thaw?
Does the black color of the panels cause the snow/ice on the panels to melt faster than the rest of the roof?

It would take a heck of a lot of energy to melt the snow with a resistive heating element.

Do you think applying RainX before the next freezing rain storm would repel the water so it would not "stick" to the panels? 

 

Offline ahbushnell

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Re: How do you deal with freezing rain and solar panels?
« Reply #93 on: February 23, 2019, 03:15:24 pm »
Kinda sketchy going up there or trying to use a ladder at this point.  Would not want to use any kind of brute force though to risk damaging the panels.

This is how they looked like last time I went there.  We got another 20-30cm of snow since though with another 40cm or so on the way and have not had a chance to go back out there.



If curious this is what the side of the house looks like after I shovelled part of the roof:



They are announcing freezing rain now so back to square one after that.  |O

But yeah if I want to live off grid I'll want to have them on a ground mount system and have them tilted mostly vertical.   Though with a big enough property I'd also have room for a wind turbine and I'd probably want a backup generator to top up batteries.
Be sure to look into the noise level of wind turbines. 
 

Offline CatalinaWOW

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Re: How do you deal with freezing rain and solar panels?
« Reply #94 on: February 24, 2019, 04:18:58 am »
Freezing rain will cause lots of problems with wind turbines also.  The biggest one is that except in that unicorn incident where the rain freezes identically on all blades of the prop/turbine the balance will be shot and there is real danger of the machine tearing itself apart if it isn't shut down.

Your climate makes it very tough.  Fortunately there is a lot of the world that doesn't have to deal with that.  Even cold places.  Where I grew up averaged five feet of snow a year, but only had freezing rain once a decade or so.  A little broom work would deal with the problems.  Where I am now gets regular freezing rain, but also regular warm ups so there are only a couple of days a year where ice accumulates.  Maybe the simple solution is a move to someplace easier.  I know that you don't have to leave Canada to improve on what you describe.
 

Offline Berni

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Re: How do you deal with freezing rain and solar panels?
« Reply #95 on: February 24, 2019, 09:25:04 am »
Freezing rain can cause quite a havoc here in central Europe too.

A few years ago there was a case of freezing temperatures flowed by a big rain storm. This caused a good 1cm of ice to build up on anything, cars, signs, trees, overhead cables etc. Usually its just a annoyance ot having to scrape and defrost your car for a good half hour before you can drive to work. But this much ice becomes so heavy that trees start falling one after the other, offten falling across roads and cutting off the more remote areas from the world when it all happens at once. Some trees fall onto overhead electrical lines, in some cases enough ice builds up on the wires themselves to make them snap or break the insulators, this even brought down one or two big 400kV lines with quite a spectacle associated with it. Some places ware left without power for days or even weeks, whole country was in chaos outside of any major cities.

Luckily my area was not hit too bad, we lost power for half a day a few times and you had to watch out when driving on roads that go trough forests, but that's about it. We kept the house warm with a fireplace in the living room, but we still had water and cellphone reception all the time. Its a very rare thing, people don't even recall this ever happening here before.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #96 on: February 24, 2019, 10:06:32 am »
Where's your house?  All I see is snow.  Where I live we just visit the snow, we don't live in it.
I do see your issue.  And I suppose you have a layer of ice on the panels.

For someone who does not live in the snow, can I ask some dumb questions?
You shoveled the snow off the panels, correct?  And there's a layer of ice covering the panels?

If you did nothing, when would things thaw?
Does the black color of the panels cause the snow/ice on the panels to melt faster than the rest of the roof?

It would take a heck of a lot of energy to melt the snow with a resistive heating element.

Do you think applying RainX before the next freezing rain storm would repel the water so it would not "stick" to the panels?

I have a broom with a long pole so I take the snow off every couple days, basically whenever I get around to it.  I bought snow shoes so I just snow shoe to the back yard, saves me from having to shovel a path.  At the start of the season I was shovelling a path then gave up on that idea.  We don't get freezing rain here that often, they get it more down south in like Toronto area, but when we get it, that ice is there for the season.  Worse is when it's a mixture of rain and snow, it creates a sort of crust.  Happens to the car too.  Pretty much have to let it run for an hour or so to get rid of that, as nothing else will get it off.

If I did nothing at all, like never cleared the snow period I pretty much have to wait till April-May before I'd see the panels again.  If I was to use resistive heat it would mostly be just to help get rid of the crusty layer, as yeah there is no way I could melt a full blown snow fall.   Though on warmer days, I have found that the panels can help melt the snow a tad.  We don't really get much warm days though.   I'm thinking if I automated the removal or at very least had something I can trigger manually by looking at a web cam, I would maybe have slightly better luck too, as I'd be able to stay on top of it more.  Depending on my work shifts I'm not always going back there. 

I'm reluctant to apply any kind of chemicals as others mentioned some may react weirdly with the aluminium, or maybe even the adhesives used.   

Never considered how wind turbines would be affected by freezing rain too but yeah I guess it makes sense.  Would mess up all the mechanical parts.   Though if I was building a wind turbine I could try to take that into account as well with my design.  Though really if I get a big enough property I can just do the original idea of having more solar panels and having them vertical.  Where I am now I just don't have enough room without shadows to do much, the shed ones are the best I can really do.  Even those arn't optimal as they face west.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #97 on: February 24, 2019, 11:04:34 am »






I always thought hell had more fire and a redish colour to it, but there you go. It's white and cold beyond belief and no doubt has endless problems with just everyday living. Must be where the REALLY bad people are sent!
I'm going to be a good boy so I don't have to go near any place like that hell on earth!!  ;D

I'll bet people that live in that white hell go out and burn old tyres at night to try and Hurry GloBull warming along as fast as they can to save them from that torture.


 :-DD
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #98 on: February 24, 2019, 11:49:25 am »
Haha the nice thing is there's less people here so it's less crowded and real estate is not through the roof. (though snow might go through the roof lol).  Also beats the +30C's that some places get. You can dress for cold but can't do much for extreme heat. 

This is a tad on the extreme side as we have not had this much snow in at least 10 years though.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #99 on: February 24, 2019, 12:20:08 pm »
Haha the nice thing is there's less people here so it's less crowded and real estate is not through the roof. (though snow might go through the roof lol).  Also beats the +30C's that some places get. You can dress for cold but can't do much for extreme heat. 

Well you got me on all those points... except 1.
The plus 30's we had here just a few weeks ago were actually 47's.  That's C not F.  :-[  Now that is hell. 
Untill this last week, hasn't been under 30 here, even the few days it did rain, for 3 months.
Predicted 26 Tomorrow then back to 33 min for the next 6 days.
Wish to heck we could get some decent rain though. Haven't had anything bar dew ( which was weird this time of year) since early November.

Quote
This is a tad on the extreme side as we have not had this much snow in at least 10 years though.

Thats Globull warming at work!!   ::)
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #100 on: February 24, 2019, 09:35:42 pm »
I thought a solution would be to put air nozzles and use compressed air to blast off the snow.
So some extra plumbing, not unlike water irrigation systems, pipes running across between the panels with nozzles there.
Could make one whole pipe move up and down and do a "sweep" over the array.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #101 on: February 24, 2019, 10:54:36 pm »

I was thinking windscreen Wipers. They wouldn't have to swish back and forth, one  cycle ought to do it if it were done regularly.
The progression of that thought was to sweep the entire array in one go.  Some long travel linear actuators which can be had all over fleabay  at the end of a bar running across all the panels that made a sweep of the whole lot at once and then parked off the end so as not to shadow.  Brushes or something like wiper blades could be fitted to the bar to  remove the snow.

Air Jets or water nozzles could also be fitted alternately.
I don't know what sort of sensor could be used to detect snow but maybe when it was snowing a manual switch could be activated to do a pass every however long.
 

Offline CatalinaWOW

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Re: How do you deal with freezing rain and solar panels?
« Reply #102 on: February 24, 2019, 11:11:39 pm »
Simple wipers are unlikely to work.   Those who drive in snow country know the drill.  Under many conditions the snow quickly piles up at the ends of wiper travel and either fouls the wiper or just falls back over it.  Maybe if you can arrange for the edges of the panels to hang over the edge of the roof and if it doesn't snow quite as much as Red Squirrel is dealing with.
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #103 on: February 25, 2019, 01:11:45 am »
Sounds like the easiest fix would be to move somewhere where it is warmer.

Here's a list of suggestions - I don't live in snow country and I will have to say none of them sound like they would work at all or even very well.
https://solarchargeddriving.com/2012/01/04/a-dozen-tips-for-getting-snow-off-solar-panels/

Forgive me but compressed air is silly.  You'll be spending more money to compress the air than you would get back from the solar panels.
Not sure how one would rig up a huge wiper on each panel.  Seems to me the freezing rain would get in the gears and ness the system up.

The heat strip would work, but then it takes a lot or energy to heat up and melt that ice.  Highly unlikely it would be worth it.

Probably not practicable, but I will share.  Get a load of manure and place a coil of plastic hose in it.  Manure can get up to 55 - 60 C.  Run the hose up to the panels to melt the ice.  You could use a fan and blow hot air through the pipe or use a pump and salt water.

I know farmers do something similar in cold climates to pre-warm water.
 


 
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #104 on: February 25, 2019, 10:18:00 am »
Compressed air has crossed my mind too as it would be easy enough to implement with a simple pipe and a bunch of nozzles with their own valves that open one at a time in sequence, but yeah don't think it would work that well.  Could use a car tire compressor to fill the tank, as it won't be as hard on the system as an AC compressor which has a high startup current.   The tank would always be kept up to pressure that way the initial burst of air would not use up battery power.  Could probably use an old propane tank or something.

I'm thinking a brush system of sorts that plows the snow down would be the most effective at least for the snow.    It would then be housed in a compartment on top when not in use so the mechanism is not in the elements.  Won't work for the freezing rain, but  if I can at least remove the snow constantly instead of waiting till I can get around to doing it, it would maybe have a slightly better chance of melting the ice over the months from being exposed.   That, combined with the heater elements might work too.

Once I finish/heat my garage I'll finally have a place to tinker, so I can probably try to come up with something and then install it at some point.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #105 on: February 25, 2019, 11:31:42 am »

Seems to me you'd need some pretty powerful heat strips to over come the cold energy those panels are having applied to them.

Also seems far from straightforward to come up with a practical soloution for this.
I agree with an earlier comment, Just move somewhere warmer where you don't have this problem!
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #106 on: February 25, 2019, 04:41:00 pm »
How would compressseed air remove the ice?   For get the cost of the compressor and the cost to run the compressor for a moment, b/ut wont the air when it comes out of the nozzles make everything even colder making it even more difficult to remove the snow and ice?
 

Offline f4eru

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Re: How do you deal with freezing rain and solar panels?
« Reply #107 on: February 25, 2019, 05:58:17 pm »
One very simple solution if you are in that niche offgrid case where you can't wait :
use tap water from the garden hose from the ground to unfreeze your panels.
Of course it will first freeze on contact, but after a minute or so, there's no energy left to freeze, and everything melts away.

5 minutes of time needed and some 0.2 euro of water, done. No special equipment or installationn or energy needed.
« Last Edit: February 25, 2019, 06:00:40 pm by f4eru »
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #108 on: February 25, 2019, 06:05:28 pm »
One very simple solution if you are in that niche offgrid case where you can't wait :
use tap water from the garden hose from the ground to unfreeze your panels.
Of course it will first freeze on contact, but after a minute or so, there's no energy left to freeze, and everything melts away.

5 minutes of time needed and some 0.2 euro of water, done. No special equipment or installationn or energy needed.

Won't that just coat the solar panels with another layer of ice?  I know I have tried that when I visit the snow on the windshield of my car.  All that happens is it partially melts the ice, and then that liquid water freezes and makes things worse.

 
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #109 on: February 25, 2019, 07:53:37 pm »
After more research and a desire to not move somewhere warmer, most people are using a "roof rake" or "snow rake" as it's called.
Automated systems have rollers and a track to move (sideways) across the array, with a soft motorized brush to flap snow/sand around. But not in a direction to clear the buildup...

You could use canopy or awning hardware and make a huge brush move across, from top to bottom. But once you have ice on the panels, I think you are pooched.

I've been applying car wax to solar panels for winter, water beads off and snow doesn't stick. Another option would be to apply rain repellent, it does the same thing. Motorcycle/ race drivers use it on their helmet visor, cuz no wipers. The stuff really works in making the water beads small, something about nucleation sites and surface tension.
« Last Edit: February 25, 2019, 08:01:41 pm by floobydust »
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #110 on: February 25, 2019, 07:57:41 pm »
After more research and a desire to not move somewhere warmer, most people are using a "roof rake" or "snow rake" as it's called.
Automated systems have rollers and a track to move (sideways) across the array, with a soft motorized brush to flap snow/sand around. But not in a direction to clear the buildup...

You could use canopy or awning hardware and make a huge brush move across, from top to bottom. But once you have ice on the panels, I think you are pooched.

I've been applying car wax to solar panels for winter, water beads off and snow doesn't stick. Another option would be to apply rain repellent, it does the same thing. Motorcycle/ race drivers use it on their helmet visor, cuz no wipers. The stuff really works in making the water beads small, something about nucleation sites and surface tension.


I suggested RainX earlier.  Sounds like you have tried this and it works fairly well?  I use it on my car windscreens every winter.  Works incredibly well.  I know our shower dowers our coated in with it also.  The water and soap scum roll right off. 
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #111 on: February 25, 2019, 08:20:19 pm »
Yes, the stuff works really well for solar panels - if they are polished glass.
I have panels with a rough wrinkle surface finish on the glass and it seems to limit the hydrophobic action. Snow kinda sticks to them.
Any ice buildup is thin if the panel angle is steep and the droplets can run off, so it sublimates quickly. But it rarely rains here during winters.
There has been no degradation for the coatings in sun, they do rub off if you scrub the panels and it's usually smog and silt only to clear off.

It looks like this or a fairly expensive mechanical system that is up against rain/snow, for tilting panels or moving a canopy cover or brush over the panels.
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #112 on: February 25, 2019, 09:09:52 pm »
Yes, the stuff works really well for solar panels - if they are polished glass.
I have panels with a rough wrinkle surface finish on the glass and it seems to limit the hydrophobic action. Snow kinda sticks to them.
Any ice buildup is thin if the panel angle is steep and the droplets can run off, so it sublimates quickly. But it rarely rains here during winters.
There has been no degradation for the coatings in sun, they do rub off if you scrub the panels and it's usually smog and silt only to clear off.

It looks like this or a fairly expensive mechanical system that is up against rain/snow, for tilting panels or moving a canopy cover or brush over the panels.

Thanks for sharing.

It's my understanding these chemicals at the microscopic level fill in the "pits" in the surface of the glass to make a smooth surface which makes it so water/snow has a much harder time "sticking" to it.  I know when I drive in the rain I don't use my windshield wipers as much.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #113 on: February 25, 2019, 11:47:20 pm »
One very simple solution if you are in that niche offgrid case where you can't wait :
use tap water from the garden hose from the ground to unfreeze your panels.
Of course it will first freeze on contact, but after a minute or so, there's no energy left to freeze, and everything melts away.

5 minutes of time needed and some 0.2 euro of water, done. No special equipment or installationn or energy needed.

Won't that just coat the solar panels with another layer of ice?  I know I have tried that when I visit the snow on the windshield of my car.  All that happens is it partially melts the ice, and then that liquid water freezes and makes things worse.

Yeah I would not want to do that it's just going to coat everything with dry ice.  It's essentially just creating my own freezing rain.  Would also need a way to get the water up there.  Don't want to turn on the hose at this time of year so I'd need to try to get a ladder up there and bring buckets.  Logisticly it's not really feasible. 

The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow. 
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #114 on: February 26, 2019, 10:43:51 am »
One very simple solution if you are in that niche offgrid case where you can't wait :
use tap water from the garden hose from the ground to unfreeze your panels.
Of course it will first freeze on contact, but after a minute or so, there's no energy left to freeze, and everything melts away.

5 minutes of time needed and some 0.2 euro of water, done. No special equipment or installationn or energy needed.

Won't that just coat the solar panels with another layer of ice?  I know I have tried that when I visit the snow on the windshield of my car.  All that happens is it partially melts the ice, and then that liquid water freezes and makes things worse.

Yeah I would not want to do that it's just going to coat everything with dry ice.  It's essentially just creating my own freezing rain.  Would also need a way to get the water up there.  Don't want to turn on the hose at this time of year so I'd need to try to get a ladder up there and bring buckets.  Logisticly it's not really feasible. 

The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow.

I would guess you are going to use some gears.  Won”t ice jam the gears?
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #115 on: February 26, 2019, 01:03:44 pm »
The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow.

Exactly what I suggested.

No need to specifically use gears.
The brush trolley could be attached to a cable and pulled along by that with a motor and Pulleys. Ice would easy be broken off by flexing of the cable and pressure.  Cheap winch in an endless cable loop would work fine.

Depending if you were going to go from top to bottom or left to right you could also use pneumatic Cylinders.  No need for a compressor, use LPG Gas. Would last an eternity and to preempt the inevitable, if you are going to talk about safety or explosions, you don't know what you are talking about so please don''t feel any need to remove all doubt of that. One could also use something like an old refrigerator compressor. may not be fast, not that you'd need it to be but the power draw would be low. Ro save power put a reversing valve in the system so the wiper is returned to 50% extension by the reversal of the pressure.

Electric Linear actuators are also an option and are usualy available is a sealed configuration so as to prevent ingress of dirt and water. If returned to the parked, start position, ice would not be a problem.  These things are available in hundreds of pounds force rating  so ice unless inches thick would not pose a problem.

What about a cover for the panels at night to stop buildup when not being used?
Cover is pulled  down/ unrolled like a pool blanket say and then rewound taking snow  and Ice with it which is dumped off the bending edge as the cover is rolled up. In bad weather thought the day when panels are doing nothing anyway, could be recovered till the sun comes out.

Maybe a system with rollers at each end could be used with clear plastic like restaurants use for outdoor areas which is thick and tough.  Just roll the plastic back and forth. Any snow or Ice will be moved off the panels and dumped off as the panel rolls.  Clear areas would be exposed like used on camera lenses on racecars and so on.  When the plastic is rolled back, the snow is taken with it and falls off the rolling edge and returns the clear first half of the roll again over the panels.

 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #116 on: February 26, 2019, 06:34:01 pm »
The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow.

Exactly what I suggested.

No need to specifically use gears.
The brush trolley could be attached to a cable and pulled along by that with a motor and Pulleys. Ice would easy be broken off by flexing of the cable and pressure.  Cheap winch in an endless cable loop would work fine.

Depending if you were going to go from top to bottom or left to right you could also use pneumatic Cylinders.  No need for a compressor, use LPG Gas. Would last an eternity and to preempt the inevitable, if you are going to talk about safety or explosions, you don't know what you are talking about so please don''t feel any need to remove all doubt of that. One could also use something like an old refrigerator compressor. may not be fast, not that you'd need it to be but the power draw would be low. Ro save power put a reversing valve in the system so the wiper is returned to 50% extension by the reversal of the pressure.

Electric Linear actuators are also an option and are usualy available is a sealed configuration so as to prevent ingress of dirt and water. If returned to the parked, start position, ice would not be a problem.  These things are available in hundreds of pounds force rating  so ice unless inches thick would not pose a problem.

What about a cover for the panels at night to stop buildup when not being used?
Cover is pulled  down/ unrolled like a pool blanket say and then rewound taking snow  and Ice with it which is dumped off the bending edge as the cover is rolled up. In bad weather thought the day when panels are doing nothing anyway, could be recovered till the sun comes out.

Maybe a system with rollers at each end could be used with clear plastic like restaurants use for outdoor areas which is thick and tough.  Just roll the plastic back and forth. Any snow or Ice will be moved off the panels and dumped off as the panel rolls.  Clear areas would be exposed like used on camera lenses on racecars and so on.  When the plastic is rolled back, the snow is taken with it and falls off the rolling edge and returns the clear first half of the roll again over the panels.

george80 your reply gave me an idea.  Tell me if you think this would work.  His issue is freezing rain and ice build up on the panels correct?  What if he were to string a series of cables loosely across the panels.  When the ice form pull the cables tight to break the ice.

 


 

Offline CatalinaWOW

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Re: How do you deal with freezing rain and solar panels?
« Reply #117 on: February 26, 2019, 06:39:44 pm »
The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow.

Exactly what I suggested.

No need to specifically use gears.
The brush trolley could be attached to a cable and pulled along by that with a motor and Pulleys. Ice would easy be broken off by flexing of the cable and pressure.  Cheap winch in an endless cable loop would work fine.

Depending if you were going to go from top to bottom or left to right you could also use pneumatic Cylinders.  No need for a compressor, use LPG Gas. Would last an eternity and to preempt the inevitable, if you are going to talk about safety or explosions, you don't know what you are talking about so please don''t feel any need to remove all doubt of that. One could also use something like an old refrigerator compressor. may not be fast, not that you'd need it to be but the power draw would be low. Ro save power put a reversing valve in the system so the wiper is returned to 50% extension by the reversal of the pressure.

Electric Linear actuators are also an option and are usualy available is a sealed configuration so as to prevent ingress of dirt and water. If returned to the parked, start position, ice would not be a problem.  These things are available in hundreds of pounds force rating  so ice unless inches thick would not pose a problem.

What about a cover for the panels at night to stop buildup when not being used?
Cover is pulled  down/ unrolled like a pool blanket say and then rewound taking snow  and Ice with it which is dumped off the bending edge as the cover is rolled up. In bad weather thought the day when panels are doing nothing anyway, could be recovered till the sun comes out.

Maybe a system with rollers at each end could be used with clear plastic like restaurants use for outdoor areas which is thick and tough.  Just roll the plastic back and forth. Any snow or Ice will be moved off the panels and dumped off as the panel rolls.  Clear areas would be exposed like used on camera lenses on racecars and so on.  When the plastic is rolled back, the snow is taken with it and falls off the rolling edge and returns the clear first half of the roll again over the panels.

While stipulating that safety may not be an issue I see two problems with LPG.  First, I don't see a practical way to recover the LPG so this is venting into the atmosphere.  For someone who is trying to be green and reduce greenhouse gas emission this may not be ideal.  Also at the temperatures that often exist when snow is an issue the working pressure of the LPG will be pretty low.  Depending on the purity of the propane it could approach zero.  In any case large area cylinders will be required.
 

Offline DougSpindler

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Re: How do you deal with freezing rain and solar panels?
« Reply #118 on: February 26, 2019, 06:51:34 pm »
The rolling track brush system sounds interesting, it's kinda what I have in mind for the snow.

Exactly what I suggested.

No need to specifically use gears.
The brush trolley could be attached to a cable and pulled along by that with a motor and Pulleys. Ice would easy be broken off by flexing of the cable and pressure.  Cheap winch in an endless cable loop would work fine.

Depending if you were going to go from top to bottom or left to right you could also use pneumatic Cylinders.  No need for a compressor, use LPG Gas. Would last an eternity and to preempt the inevitable, if you are going to talk about safety or explosions, you don't know what you are talking about so please don''t feel any need to remove all doubt of that. One could also use something like an old refrigerator compressor. may not be fast, not that you'd need it to be but the power draw would be low. Ro save power put a reversing valve in the system so the wiper is returned to 50% extension by the reversal of the pressure.

Electric Linear actuators are also an option and are usualy available is a sealed configuration so as to prevent ingress of dirt and water. If returned to the parked, start position, ice would not be a problem.  These things are available in hundreds of pounds force rating  so ice unless inches thick would not pose a problem.

What about a cover for the panels at night to stop buildup when not being used?
Cover is pulled  down/ unrolled like a pool blanket say and then rewound taking snow  and Ice with it which is dumped off the bending edge as the cover is rolled up. In bad weather thought the day when panels are doing nothing anyway, could be recovered till the sun comes out.

Maybe a system with rollers at each end could be used with clear plastic like restaurants use for outdoor areas which is thick and tough.  Just roll the plastic back and forth. Any snow or Ice will be moved off the panels and dumped off as the panel rolls.  Clear areas would be exposed like used on camera lenses on racecars and so on.  When the plastic is rolled back, the snow is taken with it and falls off the rolling edge and returns the clear first half of the roll again over the panels.

While stipulating that safety may not be an issue I see two problems with LPG.  First, I don't see a practical way to recover the LPG so this is venting into the atmosphere.  For someone who is trying to be green and reduce greenhouse gas emission this may not be ideal.  Also at the temperatures that often exist when snow is an issue the working pressure of the LPG will be pretty low.  Depending on the purity of the propane it could approach zero.  In any case large area cylinders will be required.

Or add an ignitor and direct the flame towards the the ice.
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #119 on: February 26, 2019, 08:06:22 pm »
Using fossil fuel would kinda defeat the purpose. Could just use a gas generator to make power in first place and forget about the panels altogether.  :-DD

And yea any design with moving parts I'd have to consider how the mechanism works.  I'm thinking there would be a "box" on top of the panels where the brush is kept, and then it only comes out to clear the snow.  It could even be made to be heavy, and have wheels, so it just rides on top of the panels, it would be mostly free.  Less gears/belts etc, the less chance of something jamming up.  This won't deal with the actual freezing rain issue though, but make it easier to keep them clear in first place.   If it rains on bare panels, it's not as bad as if there's snow and it rains on top of that snow, which I think is what happened here. It then creates a crust.   If it rains on the bare panels then I would get a more transparent sheet of ice so less light would be blocked and they would just keep working as normal I would think.  So I'm starting to think, the key may be to simply find a more automated way to deal with the snow, and forget about the freezing rain. Though I could still do the nichrome wire idea in addition to the brushes too.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #120 on: February 26, 2019, 10:40:29 pm »
Using fossil fuel would kinda defeat the purpose. Could just use a gas generator to make power in first place and forget about the panels altogether.  :-DD

Well if you could make as much power with the tiny bit of gas the cylinders would use with a generator as what the clean panels would give you, you should share your method with the rest of the world and solve the energy Crisis and become a billionaire.  ::)
 
You could afford to move somewhere warm then where you didn't have the problem in the first place.   :palm:
 

Offline floobydust

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Re: How do you deal with freezing rain and solar panels?
« Reply #121 on: February 27, 2019, 11:49:29 pm »
It was -28ºC the other night and I imagine Aussies would love that right now  :)  Every year it kills off the snakes, mosquitos, cockroaches, spiders and every bug. That's why we don't move to warmer climates, everything is poisonous there.
The odd chinook with freezing rain happens once or twice a year.

Solar panels output higher voltage when cold, their power output goes up around +4 to +5% per 10ºC drop. It's quite a welcome boost in cold weather, to get almost 25% more out of your panels.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #122 on: February 28, 2019, 01:57:23 am »
It was -28ºC the other night and I imagine Aussies would love that right now  :)

Errr, NO!
Thank you very much for your kind and generous offer but you can keep your cold hell and we'll stick with our Hades thanks all the same!   ;D
I just came in for a bite of lunch after ploughing a bit of garden to put in the winter crops.  Soaking wet with perspiration as usual when I do anything out in the sun. Half way through my 3rd 500ml glass of water.  Another one and I should be right.

Quote
Every year it kills off the snakes, mosquitos, cockroaches, spiders and every bug. That's why we don't move to warmer climates, everything is poisonous there.

We had some -5's here last year and that Killed off half the plants in the garden, the lawn, some tress and a bunch of other vegetation.
I just finished building an oil burning yard heater for this winter. Going to put it at one end of the veg/ ornamental garden with a fan and blow the heat around to keep the damn frost away.

Unfortunately don't do much to rid us of snakes and the like, they just Hibernate till summer and then come out again.  We have 8 of the top 10 worlds deadliest here.  And I mean RIGHT here.  I was in one of the most Noted reptile parks lasy year and spoke to this going after his presentation who is supposed to be the leading authority on snakes in Oz. Was asking him some questions and he asked where we live. The place is a bit on the fringe of the city ( as in sydney 3500Km away from where we were) and as soon as I told him he lit up and said Oh yeah, I go there all the time! and started telling us about local landmarks.

I asked if he had family here, he said no, I go there to catch and study the Brown snakes and others. There are higher concentrations of deadly snakes where you are than anywhere else in the country, we always get as many specimens as we want from there, most of our exhibits came from your area!

He was excited, Me, not so much!  :scared:  had only been here about 6 Months then, not what I would rate as the most endearing feature of the area.  He told me about the black snake population expanding here. I said great in a sarcastic tone.  He said it is for you really. I said how you figure that? He said Black is number 8 on the poisonous list. They keep away the Brows that are THE most deadly in the world. Guess which one you are better off getting Bitten by?  I asked if it was my goldfish but while technically correct, not in the context of snakes.

Didn't see any snakes myself this summer but talking to the postman whom I get on well with, He reckoned Dogs were not his main worry and he had 3 near misses this season... so far.
We do get Mosquitos all year round here which is a pain but thankfully everything else goes away till spring or so.

Quote
Solar panels output higher voltage when cold, their power output goes up around +4 to +5% per 10ºC drop. It's quite a welcome boost in cold weather, to get almost 25% more out of your panels.

While that may be true, I think it's bit of a catch 22. When it's hot it's because the suns radiation is strongest. While the efficiency of the panels may drop, the brute force of the sun beating down on them always seems to give me very good output on hot days. The best days however are when there is a tiny biot of cloud which amplifies the radiation with what is called cloud edge effect. That can really send the things into overdrive.

I also think panel heat rating is bit of a joke. the ones I have all seem to be rated to 40oC before they drop off. You can't have them in the sun at all here before they are too damn hot to touch and I know for me that's well past 50oC .  In summer, I wouldn't even try and have no doubt they could hit 100. I was going to try and film cooking on them this summer but who wants to go out in the sun on a 40o day?

I was wondering how one would go building a giant parabola out of snow  so the panels could be stood up and work on the reflection of the sun. I have read a few accounts of people getting unreal outputs from their panels in teh snow being a combination of the cold and the reflected light.
If a mound of snow was pushed up in the right direction and angle, maybe it could be used to advantage to reflect more light onto the panels and keep them at an angle that kept the snow off the fronts anyway.  Certainly wouldn't be a lack of Building materials.

Snow on the back would be a good thing not that they would need any cooling.
 

Offline Silver_Pharaoh

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Re: How do you deal with freezing rain and solar panels?
« Reply #123 on: February 28, 2019, 02:04:28 am »
It's not a solar panel, but I always used a Super Soaker water gun filled with hot water to melt snow and ice of my satellite dish  :)

I know it's not the greatest idea but maybe a misting system with washer fluid or sugar water?

 

Offline apis

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Re: How do you deal with freezing rain and solar panels?
« Reply #124 on: February 28, 2019, 08:03:45 am »
Quote
This is a tad on the extreme side as we have not had this much snow in at least 10 years though.
Thats Globull warming at work!!   ::)
Given the rolling eyes smiley I assume you were making an ironic impression of a global warming denier.  :D

But just for the record: an increase in atmospheric temperature means the air can absorb more water vapour which in turn leads to a more intensive water cycle: i.e. more rain and snow (in some places, while it gets dryer in other places). So yes, that could quite possibly be global warming at work, but it's hard to tell from a single data point since there is so much variance, on average there is an increase in precipitation though.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #125 on: February 28, 2019, 09:03:07 am »
Given the rolling eyes smiley I assume you were making an ironic impression of a global warming denier.  :D

No, that's the look of an anti green cult Bullshit realist who can think for themselves and will not fall for the biggest scam ever played on the sheeple of the world by business and gubbermints whom are all using it as a gigantic cash cow.   :palm:

In any case, according to the gloom and doomists, we are already to late to do anything about it and not enough is or ever will be done, so may as well accept the inevitable or wait for the hoax to be exposed and be happy it was just a crock of unmitigated BS.   :phew:
 

Offline f4eru

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Re: How do you deal with freezing rain and solar panels?
« Reply #126 on: February 28, 2019, 12:43:46 pm »
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we are already to late to do anything about it and not enough is or ever will be done
What a load of smelly bullshit statements.
 

Offline george80

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Re: How do you deal with freezing rain and solar panels?
« Reply #127 on: February 28, 2019, 02:08:36 pm »
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we are already to late to do anything about it and not enough is or ever will be done
What a load of smelly bullshit statements.

I forgot, we can do something, end modern life as we know it. 
All become vegetarians, never heat or cool our homes, walk everywhere, cut off electricity all together ( you'll have to because making solar panels and wind turbines causes emissions!) and live like we are in the 18th century.

All to conform with some religious like belief created by those making a quid out of pushing the fantasy but actually doing nothing practical to stop what they supposedly see as the demon  and certainly nothing that doesn't come at a high cost and make a high profit or Revenue.

Does that clarify my omission better?   ;D
 

Offline Red Squirrel

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Re: How do you deal with freezing rain and solar panels?
« Reply #128 on: March 04, 2019, 09:28:48 pm »
I guess patience is virtue, they are slowly starting to come back now with slightly warmer days.  When they produce they do melt the ice a little bit at a time.



I can't get inside the shed anymore but it's probably safe to assume the battery is fully charged. 

To give an idea of how much snow we have so far...




 



 
 
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