camelot-forum.co.uk

I've posted on this subject years ago, but recent snow has reminded me about this issue!

The problem with snow is that being white, it doesn't absorb much solar energy, so despite the gloriously sunny days that usually follow a fall of snow, you get zero kWh out of your PV until it eventually starts to melt - which can take several days even if there is no more snowfall.

Angle seems to help - if air temperatures go above freezing, the snow will slowly melt and if the panels are steep, the snow will slide off the panels, at least to some extent. But low-angle or flat panels don't benefit from this.

What I've found is that if you can clear some snow from the panel, the dark coloured PV cells start absorbing heat, and this quickly melts any residual snow. Even if you just clear half of the panel, this heat will start to melt the snow on the uncleared section, and I think if the voltage is high enough to start some power flow, the resistance of the PV cells still covered in snow will turn them into heaters, accelerating the melting of the snow above them.

I usually clear my panels with a window rubber blade - freshly fallen snow clears very easily, but if it has thawed slightly and refrozen (ie sat there for 24hours or more), it tends to stick quite tenaciously to the panel.

I have wondered whether a rod full of small holes blowing compressed air might clear panels effecctively. Or even, possibly, sprinkling the snow with some dark powder to make it absorb heat.

In the pictures below:


Snow from yesterday has slid down the panel and frozen on the lower half, then fresh snow covered the whole panel this morning - I've crudely scraped the easy snow off the top half of the panel


within about 15minutes, the snow on the lower half had unstuck itself, and easily slid off with a bit of help, any residual snow quickly melts, so you don't have to be too thorough. You can see the difference between the ones I haven't touched - still completely covered in snow.




repeating the process for the last 5panels.

I've read of people spreading coal dust over the snow on their front path to encourage melting. Bright sunshine here and a grand total of 40W coming in...

Mixed weather here, some awful gloom and snow flurries then around 45 minutes of bright crisp sunshine, dropped to gloom again now and the main array has managed a 1.1kWh yield.

Ground mount panels all brushed off first thing so they are clear yielding another 1.4kWh from them to add to the take today, battery soc 86% .

Moxi

I use the window cleaning brush on a pole approach, but it's made much easier by the fact I can climb up onto the garage roof.

The usual Window pole i clean the sand off after summer rain would be the way to go for me, and well worth the effort.
Am lucky mind, hardly ever get snow or even ice here, bonus also being in a bungalow makes access/life far easier.

Sure i recall some country or other, maybe Russia/Canada? experimented with coal dust spreading on clouds in the past to encourage the sun to break them up more effectively.

There's no way I can do anything about mine, apart from get a fire hose! It did partially clear itself in today's sun though - and I got 400W for a few hours with a grand total of 1.1 kWh!

Trace heating

AGT wrote: ↑Wed Nov 20, 2024 6:47 pmTrace heating

Yeah!

I wonder how much of this stuff you'd need to remove snow?

https://www.tlc-direct.co.uk/Main_Index ... index.html

We are into day 3 since it snowed and the panels are still covered. We've had clear skies and bright sunshine too. So I'm sure the few hundred watts for half an hour or so would've been energy well-spent!

Some sort of water cooling / heating system on the back of the panels would work well.
Harvest the heat and cool panels in the summer, flip it in the winter.
Of course, a lot more to go wrong and maintain.

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