Author Topic: Solar Panel De-Icer  (Read 13464 times)

0 Members and 1 Guest are viewing this topic.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Solar Panel De-Icer
« on: December 31, 2015, 02:14:40 PM »
Has anyone ever designed a system to spray de-icer (beet juice maybe) on inaccessible roof mounted solar panels?

My panels have been covered with snow for over a week. Usually it slides off after a day or two. My roof is 10 in 12 pitch metal.

I was thinking I could build something with a small diaphram pump inside the house with a hose going to the roof ridge and distributed by small diameter tubing with spray holes drilled in it.   I've been burning 3/4 gallon gasoline a day when the panels are covered in snow.

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #1 on: December 31, 2015, 04:45:31 PM »
You could run copper wire in a matrix above the glass and let the sun do the melting.  A continuous string crossing back and forth could be heated with a single well positioned heat element.

Johann

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: Solar Panel De-Icer
« Reply #2 on: January 07, 2016, 08:23:01 PM »
Use water to spray/wash snow off the panels.Even cold water from the well should melt the snow unless it is really cold out and you fan the spray water to much.
You can also buy low voltage 12 or 24 volt heat tape and use it under the panels, but a generator may be needed to charge the battery. Or if you have an generator running already why not use a 120 volt heat tape under the panels that is cheaper.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #3 on: January 07, 2016, 08:31:09 PM »
Use water to spray/wash snow off the panels.Even cold water from the well should melt the snow unless it is really cold out and you fan the spray water to much.
You can also buy low voltage 12 or 24 volt heat tape and use it under the panels, but a generator may be needed to charge the battery. Or if you have an generator running already why not use a 120 volt heat tape under the panels that is cheaper.
Good ideas. I could plumb hot water to it and just be careful to design it to drain dry after use so water doesn't freeze in the system.
Good idea about the 120 VAC heat tape, have to start the generator anyway if there's snow on the panels. I guess I could attach it to the backside of the panels with silicone.

Johann

  • Newbie
  • *
  • Posts: 46
  • Country: us
Re: Solar Panel De-Icer
« Reply #4 on: January 07, 2016, 08:51:15 PM »
Use water to spray/wash snow off the panels.Even cold water from the well should melt the snow unless it is really cold out and you fan the spray water to much.
You can also buy low voltage 12 or 24 volt heat tape and use it under the panels, but a generator may be needed to charge the battery. Or if you have an generator running already why not use a 120 volt heat tape under the panels that is cheaper.
Good ideas. I could plumb hot water to it and just be careful to design it to drain dry after use so water doesn't freeze in the system.
Good idea about the 120 VAC heat tape, have to start the generator anyway if there's snow on the panels. I guess I could attach it to the backside of the panels with silicone.
I would stay away from hot water, hot water on top of cold panels could crack the cold panels. Cold city water or well water should  be warm enough to melt snow and ice unless you live in extreme cold weather.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #5 on: January 07, 2016, 08:57:39 PM »
Good point.  I'm thinking the 120 VAC heat tape would be the easiest.  It would only have to cover the lower third of the panel. Once the snow/ice there slides, the rest will follow. The hard part is to get it moving over the edge of the aluminum frame.

lifer

  • Guest
Re: Solar Panel De-Icer
« Reply #6 on: January 08, 2016, 11:58:13 AM »
Same problem here.

I was thinking of placing heat tape/wire (beneath the panels) along the whole panel frame perimeter. This way, the whole ice/snow block will be displaced at once.

If you only put heat tape on the lower third, the rest of ice/snow block covering the panel might not be displaced (it could be frozen thus sticking on the aluminium frame along the top/edges).

I'm looking for some low power heat tape/wire so I could use the last battery juice to remove the ice/snow (my gen does not start automatically; moreover, it happened not to be at home when the panels was covered with ice/snow).

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #7 on: January 08, 2016, 12:15:26 PM »
Same problem here.

I was thinking of placing heat tape/wire (beneath the panels) along the whole panel frame perimeter. This way, the whole ice/snow block will be displaced at once.

If you only put heat tape on the lower third, the rest of ice/snow block covering the panel might not be displaced (it could be frozen thus sticking on the aluminium frame along the top/edges).
Around here it doesn't get cold enough for snow to hang on the upper end of the panels for long, but my roof pitch is 10 in 12 so gravity probably has a lot to do with it. Usually the first 2 or 3 inches of the upper end of the panels get exposed and the sunlight warms the panel a couple degrees.
Quote

I'm looking for some low power heat tape/wire so I could use the last battery juice to remove the ice/snow (my gen does not start automatically; moreover, it happened not to be at home when the panels was covered with ice/snow).
I figure when the panels are covered with snow, my batteries are at their weakest state. Since I would only energize the heat tape a few times a year, I don't mind starting the generator.

lifer

  • Guest
Re: Solar Panel De-Icer
« Reply #8 on: January 08, 2016, 01:35:58 PM »
A recent forecast here was a snow/rain/freeze mixture thus my panels were covered with an icy snow blanket. The rain did "soldered" the snow block to the aluminium edges hence that's why I was concerned about heating the entire perimeter.

If my batteries go weak, I automatically shutdown the inverter before going in a low SOC state thus there will always be some spare juice to heat that heating tape. Anyway, I have a back up wind turbine thus it would be handy in such a situation.

Like I've just said, my gen has no automatic start function thus it's pretty useless when I'm away from home. For when I'm home, I could manually remove the snow though. ;)

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #9 on: January 09, 2016, 11:18:36 AM »
Copper wire defroster could be heated passively, too.  It's an incredible thermal conductor and requires minimal thickness to conduct heat from one end to the other.  You're early sunlight can begin the thaw before your panels reach minimal voltage to kick in the inverter.  The key is to create something that is minimal thickness to collect warmth from sunlight.  Those replacement glass tubes for dhw look pretty easy to obtain.  Mount it above the array and fan a series of wires across the panels from the hot end to your perimeter.  It should heat up enough on early sun to melt snow.  Keep an air gap of at least an inch to prevent it from radiating heat to the panels themselves.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #10 on: January 09, 2016, 11:39:13 AM »
Copper wire defroster could be heated passively, too.  It's an incredible thermal conductor and requires minimal thickness to conduct heat from one end to the other.  You're early sunlight can begin the thaw before your panels reach minimal voltage to kick in the inverter.  The key is to create something that is minimal thickness to collect warmth from sunlight.  Those replacement glass tubes for dhw look pretty easy to obtain.  Mount it above the array and fan a series of wires across the panels from the hot end to your perimeter.  It should heat up enough on early sun to melt snow.  Keep an air gap of at least an inch to prevent it from radiating heat to the panels themselves.
You're over my head. If there is snow on the panels, they derive no power from early sunlight. What power source energizes the copper wire? If the panels are covered with snow and the copper wire is on top of the panel, the copper wires are going to be covered up too, right?

Mary B

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 3169
Re: Solar Panel De-Icer
« Reply #11 on: January 09, 2016, 07:03:05 PM »
Maybe a black painted tank that absorbs sunlight that feeds to lines on the back of the panels. In summer cover it. Use a convection design so it needs no power...

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Solar Panel De-Icer
« Reply #12 on: January 09, 2016, 08:40:16 PM »
If you internet search for an answer, no one seems to have one. Think about it. Roofs are covered in snow even if the attic has heat. What matters if the static load from all that frozen water.

Roofs have a pitch designed to prevent excess snow and ice buildup. If your panels have enough pitch they should shed snow on their own.

The frame of the panel including the bottom edge, sticks up a bit and that prevents the snow and ice from sliding off. So do the bolts that hold the frames, if they stick up above the plane of the solar panels.

A large accumulation of snow sliding off at once can be deadly. There are devices designed to prevent the snow from coming off a roof or panels in one big chunk. http://www.fromridgetoeave.com/tag/snow-guards-for-solar-panels/

Just like with shedding snow from a roof, the angle seems to be the key. http://solarchargeddriving.com/2012/12/09/study-angle-key-to-solar-panel-snow-problems/

Panels installed for maximum sun in the summer may not shed snow in the winter. Panels mounted on a shallow angle to meet wind loading limits may also not shed snow in the winter.

David HK

  • Hero Member
  • *****
  • Posts: 509
  • Country: hk
Re: Solar Panel De-Icer
« Reply #13 on: January 09, 2016, 08:43:01 PM »
A lot of motor vehicles have defroster panels in the rear view windows. Would they be of any use?

Dave

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #14 on: January 09, 2016, 11:20:21 PM »
Dhw = domestic hot water

There are vacuum sealed tubes that use ammonia vapors to passively heat from the insulated end to the cool external end, typically a round bar that mounts into a heat exchanger.  Solder a piece of flat stock off perpendicular from the cool end and branch wires over your panels every 3/4 inch to and inch apart.  Keep a one inch air gap off the solar panels so the heat in the wires only radiates to the air (and ice) around them and not to the solar panels.  These Dhw tubes are amazing and can reach well above the boiling point in overcast weather.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #15 on: January 09, 2016, 11:28:07 PM »
If your panels have enough pitch they should shed snow on their own.
My roof is 10 in 12 which is very steep. It does shed snow when the temperature reaches 30 degrees or so. But sometimes the temperature hangs below that for days.
A lot of motor vehicles have defroster panels in the rear view windows. Would they be of any use?

Dave
I think the automotive window de-icers are made as part of the glass. 

Another concern is that if I attach heat tape to the panels it will void the warranty.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Solar Panel De-Icer
« Reply #16 on: January 10, 2016, 01:07:56 AM »
The only thing I have never heard of being used is compressed air. Lines mounted on the roof and a compressor connection inside could allow you to get an avalanche started. Even using a long wand outside with a blow gun mounted on the end would be safer than climbing up on the roof.

lifer

  • Guest
Re: Solar Panel De-Icer
« Reply #17 on: January 10, 2016, 05:11:50 AM »
Wow, compressed air will be really cool (never thought of)!

I already have some portable (12V) tire compressors. If I'll add an expansion vessel for pressurized air storage could it be enough to spray the snow?

Regarding the heating wires, the most low power ones I found was 20W/meter. As I need around 5m per panel (2x1.6 + 2x0.9) that's 100W heating power per panel. That's a fair amount of power?

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #18 on: January 10, 2016, 07:05:43 AM »
You only need to hit 1°C to thaw.  Are you trying to bring them to indoor temperatures?

Nickel chromium wire, used in diy foam cutters is an inexpensive heating element.  If 12V at under two amps can cut Styrofoam, I imagine you could do pretty well with far lesser amperage to melt snow.

DamonHD

  • Administrator
  • Super Hero Member Plus
  • *****
  • Posts: 4125
  • Country: gb
    • Earth Notes
Re: Solar Panel De-Icer
« Reply #19 on: January 10, 2016, 07:28:47 AM »
Well, except that ice/water has an enormous specific and latent heat capacity...

Rgds

Damon
Podcast: https://www.earth.org.uk/SECTION_podcast.html

@DamonHD@mastodon.social

lifer

  • Guest
Re: Solar Panel De-Icer
« Reply #20 on: January 10, 2016, 08:49:20 AM »
You only need to hit 1°C to thaw.  Are you trying to bring them to indoor temperatures?

The outdoor temperature around here could easily reach -15°C or under. I was trying once to keep my dog(!) drinking water above 5°C using a 20W diy immersion heater and it barely kept the water (5 liter) above freezing point. 

That is, I'm not trying to reach indoor temperatures but I was concerning about heat lost due to low outside temperature.

Anyway, you could use a small amount of power for a longer period (at the risk of lost it all due to low outdoor temperature) or an increased amount of power for a shorter period (quick shot).

Nickel chromium wire, used in diy foam cutters is an inexpensive heating element.  If 12V at under two amps can cut Styrofoam, I imagine you could do pretty well with far lesser amperage to melt snow.

I guess @DamonHD is right: you only got a longitudinal (and circular) cave around that nickel chromium wire. You need to stick it to a copper foil or something to enlarge the heated area.

OperaHouse

  • Hero Member
  • *****
  • Posts: 1308
  • Country: us
Re: Solar Panel De-Icer
« Reply #21 on: January 10, 2016, 11:02:19 AM »
Haven't read all the replies in detail.   It would seem that only a minimal amount of heating needs to be applied near bottom of panel to clear some surface.  Then solar radiation will do the rest.  If that won't do it then there isn't enough sun anyway to care about.  Why bottom?  Heating an upper portion will create ice dam that will be harder to get rid of. Melted water will flow easier over cleared section and will exit without refreezing.

dnix71

  • SuperHero Member
  • ******
  • Posts: 2513
Re: Solar Panel De-Icer
« Reply #22 on: January 10, 2016, 11:24:37 AM »
Using compressed air with a wand would probably take at least a small tanked compressor. With the air control by the operator, stuck a wand made of stainless steel brake/fuel line under the snow and force it to break away.

If you can safely stand on the crown of the roof you will be using gravity all the way to your advantage.

lifer

  • Guest
Re: Solar Panel De-Icer
« Reply #23 on: January 10, 2016, 02:07:07 PM »
It's very handy to use a wand but I need an automated process (for when I'm away from home).

I thought once about pulling over some kind of "curtains" when it begin to snow and remove them after. It just needs two small DC motors (one on each side) to manipulate the curtain but you have to store it somehow (think about a convertible car ;) ).

Mary B

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 3169
Re: Solar Panel De-Icer
« Reply #24 on: January 10, 2016, 07:22:37 PM »
Air lines ran along the tops of the panels with 2 small pinpoint nozzles per panel. Run it down to your compressor and just hit the on valve...

MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #25 on: January 10, 2016, 11:43:51 PM »
Entirely too complicated.  I would avoid mechanical and pneumatic solutions when simple solutions are available.  Explore the vacuum tube Dhw solution before dismissing it.  They collect a surprising amount of sunlight even when light conditions are less than ideal.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #26 on: January 11, 2016, 12:21:10 AM »
I like the idea of using compressed air, there would be no concern with draining the piping afterwards as you would with water. but my concern would be where to put the nozzles. If they were on the bottom I would be fighting gravity, if they were on the top they might just blow off the top half of the panel and leave the bottom still covered.

A broom or rake would have to be about 30' long. That would be hard to control,especially with my bursitis.   There is no way I would get up on that steep roof in the winter, I built a scaffold when I put those panels up there.  Anything that puts much of a load on the batteries when there is snow on the roof is out. 
Squirting de-icer would not take much power. My air compressor is gasoline powered so blowing air would not run down batteries.

DanG

  • Hero Member
  • *****
  • Posts: 1122
  • Country: us
  • 35 miles east of Lake Okeechobee
Re: Solar Panel De-Icer
« Reply #27 on: January 11, 2016, 08:24:38 AM »
This Fall I watched a guy push autumn leaves from a row of houses to the street with a larger drone...  even cleared stairwells and leaf dunes near foundations...

Barring that, here in Minnesota we've been using a 20V lithium powered leaf blower for clearing nuisance snows from walks, stairs and driveways for a couple of seasons - one clipped onto to a tramway and pulled through a track loop and back down might be worth the hassle.


MattM

  • Hero Member
  • *****
  • Posts: 1167
  • Country: us
Re: Solar Panel De-Icer
« Reply #28 on: January 11, 2016, 07:33:29 PM »
I would be worried about ice.  Once you blow the snow off it still needs the ice cleared.  You really don't need much heat in the grand scheme if you use a method that operates over time.  Snow and ice are wonderful wind blocks, so as long as you're undermining the build up it will flow off as it loosens up the bottom that anchors it.

I grew up around metalwork.  My solutions tend to be for long periods of time with minimal human input.  The one drawback would be blowing needles and leaves.

Mary B

  • Administrator
  • SuperHero Member
  • *****
  • Posts: 3169
Re: Solar Panel De-Icer
« Reply #29 on: January 11, 2016, 08:41:06 PM »
I find the ice clears itself within a day even at -10. The panels get pretty warm in the sun.

armadillo

  • Jr. Member
  • **
  • Posts: 69
Re: Solar Panel De-Icer
« Reply #30 on: January 11, 2016, 11:24:53 PM »
I have never had an ice layer, only ice at the edges holding the snow in place.  Sometimes in the morning there is a layer of frost, but that melts as soon as the sun hits it. Sun shines right through ice and the panels get warm. Snow is the problem.

XeonPony

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 888
  • Country: ca
  • Sanity is over rated!
Re: Solar Panel De-Icer
« Reply #31 on: January 18, 2016, 10:06:42 AM »
I'd use some 2 inch pvc with an outlet under each bank, build a custom made high wattage heater with NiChrom and a  computer fan, gentle hot air bath will be enough to loosen it all up, if it needs more up the air flow and or wattage.

Or a glycol recirculating loop with a solar heater with a back up electrical unit.

With out knowing the configuration on the roof hard to suggest the best idea.

At -30c so long as I can get over 40% of the panel cleared it will clean its self once the sun hits.

As for the defoger style grids you can buy self adhesive kits: http://www.frostfighter.com/clear-view-defrosters-about.htm

There is a large array of options but what works for you will depend on a few factors, it all starts with the general lay out of the panels, lowest average temps and so on.

Snow is a good insulator, it allows us to build the heat up till we reach a point it all comes off, so self regulating heater wire wrapped around the frames will do quite well, 30w per foot would allow for a fairy fast defrost and pretty cool ambient temp, and since the frame will expand first then the heat will work its way through rest of the glass allowing for best expansion characteristics.

Edit: If you wanted to get retardedly fancy even a heat pump system or thermosyphone
« Last Edit: January 18, 2016, 10:15:42 AM by XeonPony »
Ignorance is not bliss, You may not know there is a semie behind you but you'll still be a hood ornimant!

Nothing fails like prayer, Two hands clasped in work will achieve more in a minute then a billion will in a melenia in prayer. In other words go out and do some real good by helping!

tanner0441

  • Hero Member
  • *****
  • Posts: 1099
  • Country: wales
Re: Solar Panel De-Icer
« Reply #32 on: January 18, 2016, 02:49:48 PM »
Hi

If you have to run the generator. Why not pipe the exhaust through a copper pipe along the bottom of the panels. clamped to the bottom rail of the panel it would warm the frame up. You only need to connect it when needed.

Brian.