Keep snow off solar panels!

System
System Posts: 2,511 admin
in General Solar Power Topics #1
I am researching starting a new company selling solar panels in Utah, and very quickly realized that there is nothing developed to keep snow off of the panels in winter. I have since started development of a simple device to do just that, but wanted to get some feedback before starting production. How big a problem is keeping snow off of the panels?
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #2
    Re: Keep snow off solar panels!

    tell us more about your device? there may be something in the works for snow melting but we will see. i am curius about your device does it melt it or sweep it or what?
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #3
    Re: Keep snow off solar panels!

    In our last house I never had an issue. I wasn't thinking about wind where we are now. I mounted the panels on a south facing roof, but the house continues further south of the garage. So to the west of our panels I have the east facing house roof, the panels sort of start in that valley and continue further east. The problem is the snow blows from the Northwest and drops in the southeast corner of that part of the roof, right where I have the panels.

    After our first big snow storm (11 inches with a lot of wind) the panels in the corner were buried by more than 3 feet of snow. I had to put a harness on and go shovel out the panels, quite a pain. The garage roof 10 feet to the east was windswept and clear. I do have mounts all the way across but started in the valley, right where all the snow stuck.

    Our panels are tilted enough so snow can slide off, but not if there is no place for the snow to slide to. I would think in most cases design and location would rule out snow coverage, but sometimes it can’t be avoided.

    Oh now I keep our pool brush right there and can pull the snow away from the bottom side of the panels so they can self clear, needless to say next summer the panels are moving 10 feet east.
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • System2
    System2 Posts: 6,290 admin
    #4
    Re: Keep snow off solar panels!

    Melts. From what I understand once light begins to hit the panel they heat up and pretty much takes over from there. My device just starts the process. It works like a defroster for your car winow
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  • Solar Guppy
    Solar Guppy Solar Expert Posts: 1,989 ✭✭✭
    #5
    Re: Keep snow off solar panels!

    Latitudes that have snow require the panels be at a steep pitch for proper operation ( Sun angle is very low in the horizon and require 45 to 60 degree pitch on the panels ). Panels self-shed the snow
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  • halfcrazy
    halfcrazy Solar Expert Posts: 720 ✭✭✭
    #6
    Re: Keep snow off solar panels!

    well i am fairly north here in maine and my panels do not self shed i wish they did. but the snow melt idea is being thrown around and seems like a good one. on my array as soon as it gets started it will slide rite off.
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  • System2
    System2 Posts: 6,290 admin
    #7
    Re: Keep snow off solar panels!

    will covering the panels with another thin layer of plexiglas reduce light absorption?
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #8
    Re: Keep snow off solar panels!

    A little sweep as needed, and within an hour or so in sun they melt off. The worst is warm snow (not an oxymoron!) on cold panels, that freezes to a thick crust at the bottom of the snow. That takes a bit to melt off, but normal snow melts pretty quickly.

    A simple idea is some frost-tex type heat tape around the edges of each panels. Controlled by a switch rather than a t-stat, they draw under 3 watts/foot, only when they are on. You could also carefully run a string of frost-tex across a panel, making sure you don't shade individual cells. The tiny amount of heat would allow the panels to melt off even faster if getting on a roof to sweep them is out of the question.

    Tony

    PS. My panels are near the ridge. The problem is that the panels may slide, but the roof below the doesn't, so that even when I sweep them, I have to shovel out below them a couple of times a winter to clear the build up of snow below the bottom edges of the panels.
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #9
    Re: Keep snow off solar panels!

    Yes... But you can confirm that for yourself...

    Take any silicon solar cell/panel and connect it to a amp meter. The output current of a shorted silicon solar cell is pretty much proportional to the amount of light energy it receives.

    The ratio of the two readings (behind plastic, no plastic; both in the same sun) will give you the answer.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #10
    Re: Keep snow off solar panels!
    alex@aspenlog wrote: »
    will covering the panels with another thin layer of plexiglas reduce light absorption?

    The short answer is yes to some extent, but the question is, why would you want to do this? Plexiglas, and most plastics will yellow in the sun over time, and will reduce transmittance significantly over time.

    I can't think of why adding a layer of plexiglass would aid in melting the panels.

    Tony
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #11
    Re: Keep snow off solar panels!
    Solar Guppy wrote: »
    Latitudes that have snow require the panels be at a steep pitch for proper operation ( Sun angle is very low in the horizon and require 45 to 60 degree pitch on the panels ). Panels self-shed the snow

    Not always the case however.

    Look at the latitudes of the mountains of California, Arizona, New Mexico etc. Can have considerable snow with (fairly) low latitudes. (~35N) Fixed array might be 20-50 degrees. 50 degrees won't always shed snow, even 90 degrees won't always shed snow. My panels that are hinge mounted on the wall hold snow at 90 degrees when conditions are just right.

    Tony
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  • Mangas
    Mangas Solar Expert Posts: 547 ✭✭✭✭
    #12
    Re: Keep snow off solar panels!

    We get snow (2 or 3 times a year) in SE Arizona even at higher desert altitudes

    For us, depends on the overcast and temperature conditions.

    Our array is permanently inclined and we usually sweep the snow off with a broom but if it's frigid and overcast the panels still retain quite a bit of surface ice. I never do much else for fear of damaging the panels.

    I wait for the black panels to absorb the sun which cleans them off say mid morning most of the time.
    Ranch Off Grid System & Custom Home: 2 x pair stacked Schneider XW 5548+ Plus inverters (4), 2 x Schneider MPPT 80-600 Charge Controllers, 2 Xanbus AGS Generator Start and Air Extraction System Controllers, 64 Trojan L16 REB 6v 375 AH Flooded Cel Batteries w/Water Miser Caps, 44 x 185 Sharp Solar Panels, Cummins Onan RS20 KW Propane Water Cooled Genset, ICF Custom House Construction, all appliances, Central A/C, 2 x High Efficiency Variable Speed three ton Central A/C 220v compressors, 2 x Propane furnaces, 2 x Variable Speed Air Handlers, 2 x HD WiFi HVAC Zoned System Controllers
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  • n3qik
    n3qik Solar Expert Posts: 741 ✭✭
    #13
    Re: Keep snow off solar panels!

    I have gone out 2 times with a rubber hammer to knock 2-4" of ice off the panels. Any type of brushing would have failed on my setup. Any heater setup, would/could use more power then the panels would make that day/days. Hammer,broom,scrapper and sun for me.

    Note, I have the glassless Unisolar panels, so NO ONE should try the hammer trick on theirs. The neighbors think I am nuts for doing the above action.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #14
    Re: Keep snow off solar panels!

    i've resigned that at some times they will not be cleared. low temps coupled with lots of cloudiness after a snowfall does it every time for me. i too have the us64s and those little bubble like humps in the coating catches some of that precipitation at angles we'd normally have them at. unless it is to be nearly vertical (and maybe even then) it will continue to catch it and build. back feeding a small current through the pvs (if you haven't any blocking diodes inline) can heat the pvs just enough to get things started. the snow and ice tend to insulate the pv itself from the warming sun, but when attacked from the pv itself it could cause it to slide off. ice making machines have used this principle and i know because i used to fix them in my younger days. they did get much hotter faster of course. mind you, i have never tried to do that and it would take more power and/or time for the unisolar pvs than a standard pv with a flat glass surface. this method would have its limits without a doubt and one either has to physically keep it cleaned off or live with it. i can't reach mine in the winter as one wrong move and i could fall 15ft or more. before my disability, i chanced it occasionally.
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  • Robin Gudgel
    Robin Gudgel Registered Users, Solar Expert Posts: 58 ✭✭
    #15
    Re: Keep snow off solar panels!

    I'm not suppose to talk about this yet, but suffice it to say there is a solution coming soon.
    Robin Gudgel
    MidNite Solar
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #16
    Re: Keep snow off solar panels!

    that would be good for us for i'm sick of winter already, as i'm sure many others are over it too. for january, pittsburgh has had snow 24 of 30 days so far and we are above normal in snowfall for this month and season. we are currently about 8 inches above normal with 30.1in, but about 115 miles to my north in erie, pa (about 112 miles ene of cleveland, ohio) they have received 122.6in and this is 63.2in above normal. it's even snowing at the time of this posting.
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  • Brock
    Brock Solar Expert Posts: 639 ✭✭✭✭
    #17
    Re: Keep snow off solar panels!

    Ya as much as I am complaining about snow on the panels we almost broke a record in December, 48 inches in one month. So I suppose it is to be expected, if we continue this trend we will pass the yearly snowfall record by the end of the season, which was 96 inches. Too much snow...
    3kw solar PV, 4 LiFePO4 100a, xw 6048, Honda eu2000i, iota DLS-54-13, Tesla 3, Leaf, Volt, 4 ton horizontal geothermal, grid tied - Green Bay, WI
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #18
    Re: Keep snow off solar panels!

    so far we've gotten 20.2in this month and the local tv weather people are slipping in their predictions. they listed for today as 'D to 1in' and as of 1:39 this afternoon there was 3.5in at my place. the official measurement was 2in, but i got double that. the local stations also said that we were done with the snowfall for the rest of the day and yet the nws gave out an advisory at that same time due to heavy snow bands forming in allegheny county (includes pittsburgh) and stretching eastward. i'm tired of cleaning off my steps and walkway of this stuff and i've about run out of ice melt. i wouldn't mind if i got 10in of snow and it quit for a day or 2, but this stuff is nearly continuous and like a cold version of chinese water torture.:cry:
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #19
    Re: Keep snow off solar panels!

    You people are light weights! LOL! From my days in the BC Kootanays and Cascades,, 60cm overnight was common,,, certainly a couple of meters (6') a month is still common.

    In NW Ontario, 4-8' over the winter is still the norm.

    Tony
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  • poleikleng
    poleikleng Solar Expert Posts: 29 ✭
    #20
    Re: Keep snow off solar panels!

    I use a roof rake, aluminum pole with plastic scoop so it will not damage the solar panels.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #21
    Re: Keep snow off solar panels!

    tony,
    maybe in a comparative way we are lightweights and i'd be a heavyweight to somebody else in some other place i'm sure. i have seen snow come down in feet here just to be clear, but the amount isn't my beef as it it going too consistent making it a bigger chore than 1 big cleanup. follow me? btw, erie pa is up to 129.5 inches and yes they have more to gripe about than me. i can count my blessings here as it could be worse, but if here starts to look like that i'll move.:D

    poleikleng,
    whatever works for you is good. some have used brooms too, like myself, if they can reach. mine are located above my porch roof mounted against my home's brick wall and nothing reaches around that roof to access them from the ground. that porch roof is 6' x 23' if i remember correctly and is perfectly walkable in the good months. add snow and ice to that mix and i won't chance that fall anymore. if you were to fall in the frontal area, your hitting the ground doesn't end the ordeal as my property is slanted and you'd continue down about another 10ft to my retaining wall where you'd fall another 5ft to my sidewalk.:cry: many instalations are not very accessable and even getting dust and dirt off of them in the good months can be tough at times for some people, which is another problem area.
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  • poleikleng
    poleikleng Solar Expert Posts: 29 ✭
    #22
    Re: Keep snow off solar panels!
    niel wrote: »
    tony,
    maybe in a comparative way we are lightweights and i'd be a heavyweight to somebody else in some other place i'm sure. i have seen snow come down in feet here just to be clear, but the amount isn't my beef as it it going too consistent making it a bigger chore than 1 big cleanup. follow me? btw, erie pa is up to 129.5 inches and yes they have more to gripe about than me. i can count my blessings here as it could be worse, but if here starts to look like that i'll move.:D

    poleikleng,
    whatever works for you is good. some have used brooms too, like myself, if they can reach. mine are located above my porch roof mounted against my home's brick wall and nothing reaches around that roof to access them from the ground. that porch roof is 6' x 23' if i remember correctly and is perfectly walkable in the good months. add snow and ice to that mix and i won't chance that fall anymore. if you were to fall in the frontal area, your hitting the ground doesn't end the ordeal as my property is slanted and you'd continue down about another 10ft to my retaining wall where you'd fall another 5ft to my sidewalk.:cry: many instalations are not very accessable and even getting dust and dirt off of them in the good months can be tough at times for some people, which is another problem area.

    Niel, my panels are ground mounted and the roof rake works well, we have had plenty of snow this year and I have been able to clean all the snow off with the roof rake. After removing the snow from the panels I have to follow up with the snow blower to throw the snow away from the panels to create some room for the next storm.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #23
    Re: Keep snow off solar panels!

    poleikeng,
    that was my point that you have access to your pvs. myself and many others cannot access their pvs to get them cleared of snow. ice i'd leave alone if possible for the solar radiation isn't blocked as much by it as it would be by snow. now excess weight from ice may necessitate that ice removal and would prove to be more difficult without harming the pvs or killing one's self.
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  • Horsefly76
    Horsefly76 Registered Users Posts: 9 ✭
    #24
    Re: Keep snow off solar panels!
    niel wrote: »
    poleikeng,
    that was my point that you have access to your pvs. myself and many others cannot access their pvs to get them cleared of snow. ice i'd leave alone if possible for the solar radiation isn't blocked as much by it as it would be by snow. now excess weight from ice may necessitate that ice removal and would prove to be more difficult without harming the pvs or killing one's self.

    How about a small spray nozzle at the top of each panel. A bit of deicing fluid would keep snow and ice from forming/sticking to the panels.

    The stuff we use in the aviation industry is bio-degradable.

    Or one could just spray manually before a storm.

    My $.02 worth.
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #25
    Re: Keep snow off solar panels!

    got a link to the stuff so we can look it over?
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #26
    Re: Keep snow off solar panels!

    I posted this link before about Aircraft anti-icing/deicing materials.

    Basically, the major options are Ethylene Glycol and Propylene Glycol. EG is very poisonous (i.e., the sweet tasting car anti-freeze), whereas PG is not considered hazardous.

    Just to see... Here is a link:
    TKS Aircraft Deicing Fluid, 2.5 Gallon Jug

    Take a look at the Material Data Safety Sheet (PDF download):
    Ethylene glycol 85%
    Isopropyl alcohol 5%

    WARNING!
    Keep away from heat, sparks and flame. Avoid prolonged or repeated contact with skin. Keep container closed. Use only with adequate ventilation. Avoid exposure during pregnancy. Wash thoroughly after handling.

    Routes of Entry
    Absorbed through skin. Dermal contact. Eye contact.
    Inhalation. Ingestion.

    Potential Acute Health Effects

    Eyes
    Slightly hazardous in case of eye contact (irritant).

    Skin
    Hazardous in case of skin contact (sensitizer).
    Slightly hazardous in case of skin contact (irritant, permeator). Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering.

    Inhalation
    Slightly hazardous in case of inhalation.

    Ingestion
    Very hazardous in case of ingestion.

    ...

    Section 11. Toxicological Information
    Toxicity to Animals
    Acute oral toxicity (LD50): 3600 mg/kg (Mouse).
    (Isopropyl alcohol).
    Acute dermal toxicity (LD50): 9530 mg/kg (Rabbit.).
    (Ethylene glycol).
    Chronic Effects on Humans
    CARCINOGENIC EFFECTS: Classified A4 (Not classifiable
    for human or animal.) by ACGIH (Ethylene glycol).
    Classified 3 (Not classifiable for human.) by IARC
    (Isopropyl alcohol).
    DEVELOPMENTAL TOXICITY: Classified Reproductive
    system/toxin/female, Reproductive system/toxin/male
    (PROVEN) (Ethylene glycol). Classified Reproductive
    system/toxin/female, Reproductive system/toxin/male
    (PROVEN) (Isopropyl alcohol).
    Other Toxic Effects on Humans
    Very hazardous in case of ingestion.
    Hazardous in case of skin contact (sensitizer).
    Slightly hazardous in case of skin contact (irritant,
    permeator), of inhalation.
    Special Remarks on Toxicity to Animals
    Toxic for humans or animal life. (Ethylene glycol)
    Special Remarks on Chronic Effects on Humans
    Detected in maternal milk in human. (Isopropyl alcohol)
    Special Remarks on Other Toxic Effects on Humans
    Exposure can cause nausea, headache and vomiting.
    (Ethylene glycol)
    If you don't need it--probably better to avoid spraying around your home--at least if you want kids.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    #27
    Re: Keep snow off solar panels!

    bill,
    i don't know if that's the same stuff horsefly 76 is referring to. he can confirm or deny that.
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  • System2
    System2 Posts: 6,290 admin
    #28
    Re: Keep snow off solar panels!

    Couple of things. I just had panels installed (Long Island, NY). I put a bit of thought into this issue... OK, I put a lot of thought into this issue. I also, coincidentally, recently blogged about a related issue (see kkranz.wordpress.com - search for solar).

    This advice really only applies to people currently planning on a new installation. If you have a system installed, it is not too late to consider restringing your array. Moving the panels is probably a non-starter...

    1) I had my panels pushed as close to the front edge of the roof (away from the ridge line) as possible. This way when the snow starts to melt (and it will start to melt from the black panels up against a warm roof) the snow doesn't get hung up on the roofing shingles.

    This has worked out almost TOO good. I worked from home today. The snow (about a foot's worth) has completely come off of my panels. One little blotch on a single panel near the top. The problem is the snow comes off in HUGE avalanches. If anyone is standing in the garden they will absolutely be knocked out by the force. It sounds like a train when it slides off the roof (and hits the hits the bay window kick-outs). This part I did not think through. I have twin 4yr old boys. So this is an ongoing/growing concern.

    aside: this is our 3rd fairly large snowfall. After each, the snow has shed off the roof very very quickly. I'm kicking myself that I didn't setup a video camera. I will the next time.

    2) I had my panels strung such that (with the notable exception below) the top two rows are a single string. This way, as the snow slides down (but not totally off) this one full strings comes alive. And that worked today. After a HUGE slide, I went to the monitor page. I could see that one of my inverters was working at around 60% and the other was at zero. Just like I designed it - if I could reach my back, I'd pat it.

    3) The 3x3 grid on the right (see the photo on my blog) is a separate string. This string is subject to diffuse shading in the winter. Again, this way, if this group of panels are experiencing shading, the other 3 strings are free to generate at full output.. assuming no snow. Shading is more of a problem for me than snow. I am trying to figure out just how much $$$ I am losing from the shading. I really really don't want to cut down or top the trees. Trees are good too you know.

    So my strong recommendation is to take these issues into consideration when you plan your system. Think about the things that will diminish your output and take actions to mitigate them. The company that did my system did a very good job, but they did not think these issues through. If left to their own wits, they would have strung my panels up-and-down from left-to-right. This would have resulted in diminished output under anything but full/direct sunlight. My approach allows for graceful degradation under normal environmental conditions. Frankly, I'm a bit shocked that I don't see more vendors focusing more on graceful degradation - maybe I just didn't look hard enough. I take graceful degradation into account on large scale SW systems I design - so my brain is just wired that way.

    Good luck. I don't normally follow this website. If you need to reach me, post to my afore mentioned blog and list this site. I will travel back to respond.
    -ken

    PS: I forgot to mention, I also had the panels biased as far to the north on the roof as possible. Pushing them as far from the shading as possible. I tend to forget that part because the vendor didn't do such a good job. They could have been another 1.5' to the north. I didn't pick up on it till way after the rack was installed.
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  • icarus
    icarus Solar Expert Posts: 5,436 ✭✭✭✭
    #29
    Re: Keep snow off solar panels!

    Kranz,

    Interestingly enough, there is a current thread about building homemade mounts that addresses this very issue. Somewhere in that thread I posted some experience with roof slides,and why I thought it was a bad idea to mount panels near the bottom of the roof rather than near the top. (Of course I can't find it to link right now,,I'm sorta medicated from some dental work!)

    Tony
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  • BB.
    BB. Super Moderators, Administrators Posts: 33,613 admin
    #30
    Re: Keep snow off solar panels!

    Home made Roof Mount Help

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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  • solarvic
    solarvic Solar Expert Posts: 1,071 ✭✭✭✭
    #31
    Re: Keep snow off solar panels!

    My roof is insulated so well that I wouldn,t put solar on the roof. Afraid of roof cavein. All my panels are on top of pole racks. I got a squege on a 10 foot piece plastic cinduit for a handle. Works preety well. I was thinking of putting rainx on the panels and the snow should just rool off. I ask about this on alt energy forum and they told me not to put anything on my panels but didn,t give any reason not too. I don,t see what it could hurt. Does anyone here know of any reason why it would hurt anything to use rainx? I used it on my motorcycle windshield and it water ran off and it never hurt it. Also put it on satelite dish and the snow don,t stick. Solar vic
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