Flat solar panels

[blackrose]

I've fitted my new panels to the roof temporarily. The aluminium brackets are just stuck down with PU sealant/adhesive at the moment but I'll drill & tap a couple of holes in each bracket once the set screws arrive. The intention was to have them flat with the potential to angle them if required at a later stage. But it gets very windy around here and I'd worry about angled panels being ripped off the roof.

 

One thing I didn't envisage are the lakes of rain water collecting on the panels contained by the frame around the panels. If I keep them flat would I just sweep the water off with a soft broom? What do others with flat panels do?

 

 

[nicknorman]

Does the water actually matter? Presumably it is transparent to the sunlight and cool panels are more efficient panels. No idea, genuine question.

[rusty69]

We have 4 flat panels. I don't wipe the water off. They have been like that for years. Though I only tend to take notice what they are doing from Mar to Nov. 

 

Having said that I don't actually know how flat they are, as the boat probably moves more than yours when we move inside it (narrowboat) , and it's also nose high so maybe the water doesn't settle as much

 

Edited October 20, 2022 by rusty69

[LadyG]

I don't worry about it, I just wash them every so often to remove dirt.

I do worry about them taking off in a gale, but they are still there, it would be quite a faff to tie them down. I would have angled panels at horizontal unless weather mild.

Edited October 20, 2022 by LadyG

[robtheplod]

Nice install, very neat and unobtrusive!

[GUMPY]

my boat sits slightly bow up, means the water drains to the back.

I have these  

https://www.ebay.co.uk/itm/255564338377?

fitted either side at the lowest point.

They work well and keep the panels water free so no dirt builds up where the puddles used to be.

 My panels are 40mm deep and I have some spare clips if you want to try them.

Don't ask how they work as I cant see it but they do drain the panels.

 

[Jen-in-Wellies]

2 minutes ago, robtheplod said:

Nice install, very neat and unobtrusive!

Seconded.

[Paul C]

On a widebeam you could have fitted 2 panels side by side and left a walkway down the middle?

[blackrose]

1 hour ago, nicknorman said:

Does the water actually matter? Presumably it is transparent to the sunlight and cool panels are more efficient panels. No idea, genuine question.

 

A friend of mine says:

 

Firstly, in the actual rain, you’re only going to be getting around 10% of your clear, sunny day power. So hardly worth worrying about. 

 

I carried out an experiment, on a hot, beautiful sunny day this summer, while I was clearing a layer of dust off my panels. 

I used my hose to create a layer of water on the panels. It didn’t affect the power reading at all. 

 

There  must be some reflection at the interface between the air and water, but I suspect the water reduces, or negates, the normal reflection on a dry day at the air-glass interface. So, it balances out. 

Bottom line: there was no degradation owing to the water.

 

49 minutes ago, Loddon said:

my boat sits slightly bow up, means the water drains to the back.

I have these  

https://www.ebay.co.uk/itm/255564338377?

fitted either side at the lowest point.

They work well and keep the panels water free so no dirt builds up where the puddles used to be.

 My panels are 40mm deep and I have some spare clips if you want to try them.

Don't ask how they work as I cant see it but they do drain the panels.

 

 

Thanks Julian. I might take you up on that, or I'll just buy some if my panels are a different depth.

 

Edit: just measured the depth and they're 35mm so I've ordered 10 of those clips and I'll see how it goes. 

Edited October 20, 2022 by blackrose

[blackrose]

6 minutes ago, Paul C said:

On a widebeam you could have fitted 2 panels side by side and left a walkway down the middle?

 

Yes we discussed that on a different thread. The conclusion was that one panel facing away from the sun would knock both panels out if connected in series and if connected in parallel you'd still only get one panel producing anything. It was pretty unanimous that both panels down the middle was a better option.

[rusty69]

You will probably find the built up of dust more a problem with flat mounting them. There was quite a bit of fine sahara dust on ours this year. I guess tilted panels don't suffer as much as the water will clean and run off. 

 

I guess peoplein houses dont clean their panels. 

[Rob-M]

The only thing I sweep of our panels is the snow and leaves if we have moored under trees.  I don't worry about rain water on them.

[blackrose]

30 minutes ago, robtheplod said:

Nice install, very neat and unobtrusive!

 

Thanks. The narrow width of the panels fits in well with width of the sliding hatch. I actually had to cut off 6" of the hatch runners that weren't doing anything so I could fit the panels in lengthways. I could have taken that mushroom vent off but even though the hole would be covered by the panel I thought it would be too close to the edge of the panel and bound to let water in if I was up there with a hose or bucket of water. I've taken a mushroom vent off under the sternmost panel but the hole is under the middle of the panel and I've put a bead of sealant around the hole to prevent any water getting in. There's still airflow between the hole and the underside of the panel.

 

10 minutes ago, Rob-M said:

The only thing I sweep of our panels is the snow and leaves if we have moored under trees.  I don't worry about rain water on them.

 

Ok thanks.

Edited October 20, 2022 by blackrose

[Paul C]

6 minutes ago, blackrose said:

 

Yes we discussed that on a different thread. The conclusion was that one panel facing away from the sun would knock both panels out if connected in series and if connected in parallel you'd still only get one panel producing anything. It was pretty unanimous that both panels down the middle was a better option.

 

I didn't write, but meant with them both tilted too. Tho I guess if you have excess space, and never walk the roof...

[matty40s]

46 minutes ago, Rob-M said:

The only thing I sweep of our panels is the snow and leaves if we have moored under trees.  I don't worry about rain water on them.

Some kind neighbour gave us some sound advice about solar and snow....

 

[cuthound]

13 hours ago, robtheplod said:

Nice install, very neat and unobtrusive!

 

13 hours ago, Jen-in-Wellies said:

Seconded.

 

Thirded.

[Alan de Enfield]

13 minutes ago, EmmaEryy said:

To save money on power, my family and I installed solar panels on our roof this summer,

 

[Francis Herne]

I have a squeegee as used by window-cleaners - rubber strip on one side, cloth on the other, spray bottle built in which helps to lift dry stuff like dust or bird shit.

 

Water on my panel makes about a 10% difference with the sun low in the sky. At higher angles there's no difference; if the weather's hot it might even help by cooling the panels.