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Thread: Solar panel deicer

  1. #1

    Default Solar panel deicer

    On a lone mountain top in the middle of nowhere there is a tower that happily relays microwave radio signals to bring the joys/horrors of the internet to those who would have to do without.

    This tower runs with solar power.

    Issue: Snow and ice obscure the panels and the battery bank dies. It's not good for the batteries, or rural facebook addicts who tie up my friend's phone lines.

    Solution: Build a robot! er... an automated panel deicing/cleaning solution.

    I've used a lot of micros including the apparently infamous xcore. A chip that I have a number of and have never really used beyond playing with them is the Propeller. I wanted something that was easy to modify for him if he cared to tweak it so the Propeller it is.

    I have to... well spin up on SPIN but I'm a CE. that doesn't bother me.

    The question I would like to ask is more of a solicitation of ideas on how to deice the solar panels without using too much power. This is in the middle of nowhere and with the kind of snows they get near there you're not getting to the tower without climbing gear and a dog sled or a snowmobile of which he owns neither. I considered some kind of plexiglass cover on top that opens or shakes to knock stuff off but that involves too many moving parts. The idea that seems to have the most merit at the moment is a pump and nozzle system to spray an environmentally friendly deicing solution on the panels when certain conditions are met such as a bright sunny day but the panel output is low. There is a small wind turbine but even that freezes up at times.

    I've been reading over posts and there are some sharp people here. I'm hoping someone can help me figure out some alternative methods of clearing off the panels.

    So the conditions are:
    1. Power restricted so no dumping a lot of amps through heaters unless it can be done efficiently
    2. Assume things like freezing rain and five feet or more of snow.
    3. Simple and robust.
    So any ideas?

  2. #2

    Default Re: Solar panel deicer

    I have run into similar problems with my own panels.... The solution I use is (when the panels are covered in snow) ... temporarily short the terminals from the solar panel. The self heating across the internal resistance of the panels should heat up the panels enough that they will be the first to have "melt off". Even under overcast days, they will generate about 10% to 15% of their rated output.
    Beau Schwabe | Parallax Semiconductor
    IC Layout Engineer
    Parallax Inc. * 599 Menlo Drive * Rocklin California 95765
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    Asked about the ramifications of his discoveries, Hertz replied, "Nothing, I guess." Hertz also stated, "I do not think that the wireless waves I have discovered will have any practical application."
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  3. #3

    Default Re: Solar panel deicer

    A two foot vertical section of collector will never have snow on it.. This can provide the heat to de snow the panels above. It can be a part of the system or separate. No moving parts are needed. It can even be remote if necessary so the sun hits but the snow does not pile up in front of it.
    Harprit.

  4. #4

    Default Re: Solar panel deicer

    May have to try that, thanks.

    Oh and never say never about snow on vertical surfaces. I've seen times when it looks like everything has been powder coated.

    I've seen scenes very similar to this up there.
    Click image for larger version

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  5. #5

    Default Re: Solar panel deicer

    For these sever remote solar applications I usually recommend using 3 times, or more, as many PV panels as one would expect. Mount them vertically with them aimed South East, South, and South West. Space these panels several panel widths apart and as high above the ground as possible to let the wind and snow blow through. No, this is not aimed optimally for power but more for battery charging reliability.

    In addition mount an extra panel oriented for the warm season.

    Use a good quality MPPT charger on each panel. Redundancy is a good thing. Talk to MorningStar, and others, for severe environment chargers.

    Mounted vertically they shouldn't retain much snow. Ice is a different problem but that doesn't effect power output as much.

    We have used the thermal solar heater panels suggested by Harprit. This works well but you still need triple redundant panels.

    Don't forget about the lightning protection.

    Duane

  6. #6

    Default Re: Solar panel deicer

    I'd suggest doing the same thing race-car cameras do about bugs. I.e. cover the panel with something that can be moved/removed as it gets dirty. Say a thick polyethelene film traded between rolls on top and bottom of the panel. The simple act of rolling up the PE film should eject most ice and snow.

    Lawson
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  7. #7

    Default Re: Solar panel deicer

    I'm just thinking out loud here: in the same way a road sign can resonate in the wind and twist when the wind is at just the right speed.... might there be a way to "tune" the (somewhat springy) supports of the panels so they will be more likely to wiggle when the weight of the panels+snow exceeds a certain level? Use the wind itself as a driving force or perhaps a small imbalanced motor that can set the panels into resonant vibration, perhaps with a twist? shake off the snow? ...It's just a thought.

  8. #8

    Default Re: Solar panel deicer

    Personally I don't believe in any kinds of moving parts in conditions you describe. You don't say anything on how long the extreamely conditions usually last or how big your battery bank is, compared to the amount of current the repeater use. I guess the ice and snow also will be a problem with the antennas.
    Vertically mounted solarpanels will not compleately solve the problem but I guess it will help a lot. Even a high altitude summer sun will still charge the batteries enough. What about adding more batteries to the bank? Find a better wind charger, perhaps?

    We have a few similar repeater stations around here, solar panels is not an issue at all because of no effect of the sun from november to january. So its based on wind chargers only. We have faced a few wind charger breakdowns because of too hard conditions. We are now trying a wind wane that is specially made for rough environment and look forward to see how it will survive the coming winter.
    KjellO
    LA3USA

  9. #9

    Default Re: Solar panel deicer

    Painting everything black that is not critical would add some heat to help deicing. In Canada and Alaska, they often bury the batteries in the perma frost in order to remove them from the wind chill factor as the colder the battery gets, the worse it performs. Of course this means longer wires and maybe heavier. If you need really heavy copper, arc welding cables can do the job.

    Covering the solar panels with additional transparent material is likely to cause significant drops in efficiency

    About the only other thing I can think of is washing the panels in a warmed solution of ethylene glycol - that's how they de-ice airplane wings. But that is a rather messy alternative and putting in a winter's supply of the solution might be rather difficult. Warming it may just waste more electricity than it is worth.

  10. #10

    Default Re: Solar panel deicer

    Duane has the right idea. But, use heat trace with the more panels is the way to go and if you want you can rotate through these panels one at a time by using the panel voltage from the panel that is online to power heat trace to the panel that is not online.

    These panels need to be setup so their load is connected through a relay so it can be taken offline and wired in parallel to the other panels output so the relay station can say online 24/7.

    If, you don't want to the more panels. Then, I will use heat trace that is attached and laying in figure eight pattern on top of the panels.
    William Stefan
    The Basic Stamp Nut with some Spin

  11. #11

    Default Re: Solar panel deicer

    It's only about a three month period. I'm going to look at a combination of things and take a closer look at the wind turbine.

    Again, this isn't my tower so minimizing any alterations to the current setup is key.

  12. #12

    Default Re: Solar panel deicer

    - vertical mounting
    - windshield wipers
    - de-icing fluid
    - electrical heating
    - backup generator
    - propane gas warmer to melt snow and ice
    - roof used during winter when sun is low in the sky, and retracts during the rest of the year
    - bottom side of the roof could be shiny sheet metal and angled to reflect more sunlight on the panels
    - enclose the panels in a shed with the south side open

  13. #13

    Default Re: Solar panel deicer

    I like the retractable roof idea - it seems elegantly simple.

    I'm not up to speed on solar panels, so I was wondering, do they generate some % of their capability with reflected light versus direct light? If so, then in winter you could face the panels at a downward angle and they could use sunlight reflected off of snow cover and then point them toward the sun the rest of the time. At night, they could "go to sleep" pointing downward in case of overnight snows.

    The only problem is with any of the moving panel solutions, you are using a lot of energy to motivate the panels.
    MOV OUTA, PEACE

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  14. #14

    Default Re: Solar panel deicer

    Love that picture!
    Here are a couple of photos from the Sierra in California (from video, ucmerced.edu/CZO/research)

    Click image for larger version

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    These are small panels, but the equipment inside (snow depth and and weather logger) does not require much current. The battery can be sized for two weeks without solar power. It has was a problem at first due to lack of control of placement in a forested area.

    I agree about vertical or near vertical placement, if possible. Panels that have any kind of rim or bump (like the one in the photo) hold snow longer than a flat surface. There are small rimless panels build on a flat aluminum plate that are better in this respect.

    Has anyone suggested a year's supply of explosive charges on the back of the panel? Well, how about a large pager motor?

    About ethylene glycol... It has a sweet smell that can be very enticing to bears.

  15. #15

    Default Re: Solar panel deicer

    Just an idea to test - kind of novel de-icer based on vibrating a vertical solar panel structure / surface. Some kind of mechanical 'shaker' that creates an ultrasound (or any 'sound' ) vibration of the solar panel surface to achieve the same effect as an ultrasound cleaner does, e.g. shake an ice or snow from it. Can be just a motor with an off-center weight attached and mechanically joined to a solar panel mounting - the same principle as used in cell phone's or pager buzzers. Doesn't have to be a giant 'shaker' to dislodge a shovel of snow anyways :-)

  16. #16

    Default Re: Solar panel deicer

    I have a remote test site in Vermont, where there is an average of 60" of seasonal snow in our area. This past year I've installed solar panels and have wondered what was available for deicing. The Flexmat appeared to be the most practical way to deice, but the only distributor is in France and was very delayed in responding to any questions and answers about their product. So I have sought other means of deicing... I ended up installing Deicing cable (available at Home Depot) on the back side of my Trina 230w panels and it works great! To adhere the deicing cable to the panel, and to distribute the heat from the cable, I've attached the cable to the backside of the panel with 2" aluminum foil duct tape (3" tape would probably be better). The tape was very adhesive, even when I installed it at 25deg F (-3C). I have installed two passes of cable along the lengths of the panels and it works reasonably well. I'm sure that 3 or 4 passes of cable would would work better, but if the cable is energized just as the snow condition is starting (pre-warming the panels), it will effectively melt the snow better then trying to melt the snow when you have an accumulation.

    I have also connected my Deicing cable to an Aviosys 9258, which allows me to deice my panels from any computer or my cell phone. Of course I have CCTV to check on the snow on the panels too!

    The 100' of deicing cable from Home Depot cost about $100, and a roll of 2" foil tape was another $20. Of course the time (labor to install) is another thing!Click image for larger version

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