Are there such things as heaters for solar panels?

[miner_tom]

Hi to the forum.

I am a EE and just started doing some research in developing a small solar panel/battery system for a panel that will be in an area where there will be some snow and ice. I must admit that doing any kind of a search on solar panels brings up thousands upon thousands of irrelevant ads that are not pertinent to my search. Hence, my post.

I know how math works and I realize that at the end of the day, so to speak, there must be enough charge in the batteries (at present, a selection of 12 volt storage cells) after the heating action, in whatever form that takes, to take care of the needs of the system, outside of itself. Also, there should be a small heating element put inside an enclosed case where the batteries are kept in order to prevent them from freezing.

I have thought of enclosing the solar panel, which will be vertically oriented, in a plastic case and that may work but still, there needs to be some heating in the case to occasionally melt snow and ice that stick to the case.

What is the proper "search" term for small heating elements that would be appropriate? Should I consider heaters, heat exchangers, heat pumps, etc?

Thank You
Tom

[PNPmacnab]

Use the solar panel itself. That is directly applying heat where you need it. Backfeed voltage and it just looks like a string of diodes. Voltage will have to be higher than Voc to conduct and keep it less than short circuit current rating. It takes a LOT of energy to do this. I'd strongly consider only applying current to the lower section of panel with horizontal orientation. Melt just enough to get some black and let the sun do the rest.

[miner_tom]

Thank you for your response. I will investigate this method.

Tom

[bcroe]

I set up this 250W panel one cold winter day, and gradually back fed it 750W.
After 20 minutes it had zero effect on the snow.

The current MO is get some dark parts of panels cleared and exposed, and let the sun
do the rest. good luck, Bruce Roe

PVmelt.jpg

[J.P.M.]

Hi to the forum.

I am a EE and just started doing some research in developing a small solar panel/battery system for a panel that will be in an area where there will be some snow and ice. I must admit that doing any kind of a search on solar panels brings up thousands upon thousands of irrelevant ads that are not pertinent to my search. Hence, my post.

I know how math works and I realize that at the end of the day, so to speak, there must be enough charge in the batteries (at present, a selection of 12 volt storage cells) after the heating action, in whatever form that takes, to take care of the needs of the system, outside of itself. Also, there should be a small heating element put inside an enclosed case where the batteries are kept in order to prevent them from freezing.

I have thought of enclosing the solar panel, which will be vertically oriented, in a plastic case and that may work but still, there needs to be some heating in the case to occasionally melt snow and ice that stick to the case.

What is the proper "search" term for small heating elements that would be appropriate? Should I consider heaters, heat exchangers, heat pumps, etc?

Thank You
Tom

Unless you plan to take the panel out of any plastic enclosure each morning and then put it back in the enclosure each night, that doesn't sound like a workable idea.
- How much snow and how much ice ?
- How cold will an uncovered panel get ?
- It may take more energy to keep the panel working than it will gain by using power to stay ice/snow free. That comes down to a problem in heat transfer and weather.

If you do heat the panel, which may be a better thought experiment than a project, I'd think it better to either heat the top portion (preferable) or the whole thing. Depending on amb. conditions and the heat input to the panel, heating part of the panel if the ambient conditions are very cold/windy/severe will (hopefully) start the melt and the melt might refreeze on the way down causing an ice dam. Heating element(s) at the top and a thermostat at the bottom might be an idea.

Overall, and similar to the idea of cooling panels with water to improve system efficiency, the idea of heating panels for snow/ice melt removal purposes is more complicated than it may at first appear, with a lot of the devil actually in the economics.

For ice removal, I'd agree with PNPmacnab - it can take a lot of energy to maintain a solar panel above 0 C.

[littleharbor2]

When Midnite Solar first developed the Classic charge controllers they were supposedly going to have a feature that would backfeed the panels causing them to warm and hence melt off ice or snow. This could even be done from long distance when configured with Wi-Fi. When I bought my first Midnite controller I thought that was such a cool feature even I would never need it. It seems this plan never came to fruition.

[bcroe]

When Midnite Solar first developed the Classic charge controllers they were supposedly going to have a feature that would backfeed the panels causing them to warm and hence melt off ice or snow. This could even be done from long distance when configured with Wi-Fi. When I bought my first Midnite controller I thought that was such a cool feature even I would never need it. It seems this plan never came to fruition.

Yes they probably ran my experiment and realized it was hopeless. At
20% efficiency my 250W panel is used to dealing with 1250W from the
sun. When I hit 750W with no results, I gave up. Imagine trying to melt
off over 100 panels, where does that energy come from?

Later the panel went into service here, no damage from the experiment.
Bruce Roe

[littleharbor2]

[QUOTE=bcroe;n434892]

Imagine trying to melt
off over 100 panels, where does that energy come from?

/QUOTE]




I would imagine from the batteries, I would think that warming from below the snow would be more effective than from over the snow covered surface. but then again it never actually became a feature so they must have found one or more issues.
I think I will run it by the Midnite guys over on their forum.

[littleharbor2]

boB over at Midnite Solar has answered this if anybody would like to read this.
What ever happened to.. (midniteftp.com)

[J.P.M.]

boB over at Midnite Solar has answered this if anybody would like to read this.

I sure would but there's no link.

[littleharbor2]

I sure would but there's no link.

What ever happened to.. (midniteftp.com)

[bcroe]

So at 7 deg F below freezing, with a lab supply for 2 X the panel output
rating, it melts in 3 hours. Have seen more than 50 deg F below freezing
here. Bruce Roe

[peakbagger]

I have talked to folks who have done so and observed how well snow reflect sun on vertical panels even under substantial overhangs. On a sunny day with low sun angle and vertical panels snow just does not build up on panels.

[littleharbor2]

So at 7 deg F below freezing, with a lab supply for 2 X the panel output
rating, it melts in 3 hours. Have seen more than 50 deg F below freezing
here. Bruce Roe

And for these type of scenarios the Super Duper Reverse Current Flow feature never was implemented.

[miner_tom]

I set up this 250W panel one cold winter day, and gradually back fed it 750W.
After 20 minutes it had zero effect on the snow.

The current MO is get some dark parts of panels cleared and exposed, and let the sun
do the rest. good luck, Bruce Roe

PVmelt.jpg

Bruce, thank you for your reply. Being a EE I have to ask questions that might seem obvious to long time users of Solar Panels but I have not used them before.

For example, when you say "back feeding" power, I am going to assume (possibly incorrectly) that you are turning off the feed FROM the panel and feeding a voltage ACROSS the panel, thereby forward biasing what are essentially PIN diodes. Is that correct? If that is so, is the voltage that is being back fed a higher voltage than the voltage that is generated by the panel? If that is so then it has to be generated somehow by an inverter/converter setup, which seems pretty power hungry or by some other method.

Can you enlighten me as to the technical procedure involved in the "back feeding' as you put it.

Regards and Thanks
Tom