Removing snow from panels

[Stinsy]

I thought about trace heating but would warming the frames be sufficient ? you wouldn't want wires across the face of the panels as this would affect their performance.

For people with hard to reach panels maybe consider small pebble sized balls of damp table salt, - damp enough to mould and hold its shape while you
lob it up on to the snow covered panels - there it will react with the snow and melt a patch which should expose enough panel in the sunlight to get the panels generating and to self clean. If you dont want to lob little balls of salt try a salt water solution in a washing up bottle - you only get one good squeeze though so aim well.

The salt "pebbles" should be less than the standard hail stone striking force so should not pose a risk to the cover glass, I would hope that theres enough water in the snow melt to wash the salt away without causing damage to the panels - I live in sight of the sea and my panels get salt haze sometimes and seem ok.

Moxi

I was thinking you'd run a line of trace along each rail. The one I looked at was 12W per m so if you imagine a 1700x1100mm secured by 2x rails then you'd get 26.4W per panel. The aluminum rails and frame should do a lot of work for you and I'm thinking you'd just need to melt the teeniest layer under the snow to allow it to slide off.

[Stig]

I have pigeons roosting under my panels as trace heating!

[Moxi]

I thought about trace heating but would warming the frames be sufficient ? you wouldn't want wires across the face of the panels as this would affect their performance.

For people with hard to reach panels maybe consider small pebble sized balls of damp table salt, - damp enough to mould and hold its shape while you
lob it up on to the snow covered panels - there it will react with the snow and melt a patch which should expose enough panel in the sunlight to get the panels generating and to self clean. If you dont want to lob little balls of salt try a salt water solution in a washing up bottle - you only get one good squeeze though so aim well.

The salt "pebbles" should be less than the standard hail stone striking force so should not pose a risk to the cover glass, I would hope that theres enough water in the snow melt to wash the salt away without causing damage to the panels - I live in sight of the sea and my panels get salt haze sometimes and seem ok.

Moxi

I was thinking you'd run a line of trace along each rail. The one I looked at was 12W per m so if you imagine a 1700x1100mm secured by 2x rails then you'd get 26.4W per panel. The aluminum rails and frame should do a lot of work for you and I'm thinking you'd just need to melt the teeniest layer under the snow to allow it to slide off.

The aluminium would give good thermal conductivity but in freezing conditions is 26Watts going to convect to the underside of the panel how much heat energy would arrive by conduction ? Its possible but on pipe work which i am more familiar with its usually trace heating wire under insulation and conduction as the main transfer medium. The other question is then is it worth the effort for the few days a year we have such wintery weather ? then the other other question is what do the Canadians and North Americans do with their panels as they arguably get much more snow than we do ????

Moxi

[Andy]

I thought about trace heating but would warming the frames be sufficient ? you wouldn't want wires across the face of the panels as this would affect their performance.

For people with hard to reach panels maybe consider small pebble sized balls of damp table salt, - damp enough to mould and hold its shape while you
lob it up on to the snow covered panels - there it will react with the snow and melt a patch which should expose enough panel in the sunlight to get the panels generating and to self clean. If you dont want to lob little balls of salt try a salt water solution in a washing up bottle - you only get one good squeeze though so aim well.

The salt "pebbles" should be less than the standard hail stone striking force so should not pose a risk to the cover glass, I would hope that theres enough water in the snow melt to wash the salt away without causing damage to the panels - I live in sight of the sea and my panels get salt haze sometimes and seem ok.

Moxi

I was thinking you'd run a line of trace along each rail. The one I looked at was 12W per m so if you imagine a 1700x1100mm secured by 2x rails then you'd get 26.4W per panel. The aluminum rails and frame should do a lot of work for you and I'm thinking you'd just need to melt the teeniest layer under the snow to allow it to slide off.

The aluminium would give good thermal conductivity but in freezing conditions is 26Watts going to convect to the underside of the panel how much heat energy would arrive by conduction ? Its possible but on pipe work which i am more familiar with its usually trace heating wire under insulation and conduction as the main transfer medium. The other question is then is it worth the effort for the few days a year we have such wintery weather ? then the other other question is what do the Canadians and North Americans do with their panels as they arguably get much more snow than we do ????

Moxi

I have to clear my snow more from the sheer quantity that builds up. Especially when we have a bit of drizzle back into freezing again. The weight fair builds up. I keep wondering what the best method to clear it would be. If I can melt a bit to get black glass showing then that should be enough. I'll have a go next year maybe and rig up some trace on a small section as a test.

I've wondered if sending reverse current into the pv panels would cause them to heat up. Of course it won't work with the diodes. But if they weren't there ?

[Stig]

I've wondered if sending reverse current into the pv panels would cause them to heat up. Of course it won't work with the diodes. But if they weren't there ?

Aren't they bypass diodes in parallel with the PV? You won't get reverse current down them but I thought the PV itself was a diode so maybe you can't get reverse current down them either?

[Andy]

They have a blocking and bypass.

[ivan]

PV panels have bypass diodes (2, 3 or sometimes 4), but the 'blocking diode' is either in the charge controller (12v systems) or not required in the case of grid-tie systems.

Yes, blocking diodes, as far as I can see, should stop reverse power through a totally blocked panel, but as the strings of cells controlled by the diodes are normally vertically arranged (in the case of 'portrait' installation), if you uncover some cells on a string, then I think as they generate power they will feed power through the other cells in that string.....though I could be wrong.

I've always wanted to try compressed air - a length of tube, air inlet at one end, blocked off at the other, with pin holes in a line down the length of the tube.

[spread-tee]

I fill up my garden sprayer gizmo, the ones we all used to fill our solar thermal systems with, with hottish water and give them a shower, I made a long lance for it ages ago to water hanging plants which reaches the panels on the shed woodstore roof, and if I hang out the window I can get some of the panels on the lofty roof. Works a treat, good for the van windscreens too.

desp

[Marcus]

My semiconductor physics is a little rusty, but iirc the cells in a pv panel are diodes and 'forward biased' - i.e. voc for each cell is about 0.55v and Voc is the limit of the output voltage because the 'diode' starts to conduct and effectively shorts itself preventing Voc going higher. So, if you were to try to raise the voltage of the panel above Voc with an external supply they would start to conduct at about 0.55v per cell and dissipating heat at about 0.55W per cell per amp.

If my memory is right.

[ivan]

On that basis, you'd want slightly over half of the cells freed of snow and enough voltage for the inverter to start trying to draw current in order for the panels to self-heat electrically (in addition to the heating from solar gains conducting from the exposed section)