Flexible Solar Panels - Heat.

[graham460]

Hello Fellow Sailors.. I have my boat in Sardinia. Marina kept disconnecting the shore power anyway i have 5 dead batteries..

So I decided to install Solar system..

I made a couple of Bases out of wood and plywood. to have 2 x 100watt panels and 2nd Area 2 x 70w Panels FLEXIBLE..

Someone has just come up to me and Said " They Panels may Overheat and Cause fire" They need ventilation underneath. I believe the Flexible panles I will be getting sent from the Uk have aluminim backing.
Any thought and Advice would be appreciated.. I ahve virtyally finished the two wooden frames.. I just needed to Make they More appealing with hardwod covering.. I will attach Photos.. Plywood painted Cream then a clear polyurethane varnish . regards Graham

 

[thinwater]

The overheating is invariably caused by cell damamge caused by repeated flexing over bimini frames. They can flex for installation, but not repeatedly.

Just secure the panels to the deck with screws or Sika 291. They will flex to the curve and be just fine. Ditch the wood frames, you don't need them.

 

[ghostlymoron2]

When I installed my first solar panel, (17' boat, 10w semi flex panel), I used threaded studs and supported them 50mm above the deck to provide ventilation.
Subsequent installations were bolted direct to the deck using semi flex panels. No ventilation was provided and the panels didn't overheat. BUT this was in Wales not Sardinia.

 

[ghostlymoron2]

The overheating is invariably caused by cell damamge caused by repeated flexing over bimini frames. They can flex for installation, but not repeatedly.

Just secure the panels to the deck with screws or Sika 291. They will flex to the curve and be just fine. Ditch the wood frames, you don't need them.

Good installation you probably get some shading but not much. I had one installation very similar to this.

 

[graham460]

When I installed my first solar panel, (17' boat, 10w semi flex panel), I used threaded studs and supported them 50mm above the deck to provide ventilation.
Subsequent installations were bolted direct to the deck using semi flex panels. No ventilation was provided and the panels didn't overheat. BUT this was in Wales not Sardinia.

Hi Thin Water and Ghostly

Thanks for the advice.. I do not have space at the Aft Are thats why i built fie trame it is Quite flat. - Yes I could of Just glued them down in the Bow area But It was easy enough for me to make a frame.. So they should not FLEX.. My concern is with the HOT sun in Sardinia. I see what you are both saying I Have ordered the panels from UK But thay have not been posted yet.. JUST WONDERING IF I SHOULD SWAP TO STANDARD SOLID SOLAR PANELS in ametal frame Mounted on the Plywood that may give a slight air gap. Prefer not too, as I would like to Walk (Gently) on this area.
The AFt area may get some ventilation - BOW are Virtually none apart from the slight gap at either end - SEE FRONT Photo.

 

[Stemar]

Even a small area of shade on a panel will reduce output to a fraction of what it should be. My tip if you want solar panels under the boom is to get a pair. That way, when one is shaded by the boom, the other is still in full sunlight.

 

[Fr J Hackett]

The biggest problem with the heat is that it will reduce the efficiency of the panels the cooler you can keep them the better their efficiency, an air gap would help a little I very much doubt they will overheat and cause a fire.

 

[Metalicmike]

Solar panels are more efficient oriented vertically as they collect both direct and reflected light, they also run cooler, making them more efficient.

 

[William_H]

Solar panels are more efficient oriented vertically as they collect both direct and reflected light, they also run cooler, making them more efficient.

I doubt that very much. Use an amp meter on the panel and shift the orientation. Definitely more current aimed straight at the sun. Yes in some circumstances like high latitude you may find the best answer is vertical facing south. For over time best delivery but even then would need research to decide best orientation over 12 months.
No I have never heard of panels catching fire. (nothing flamable) (in a community of around 300,000 domestic installations averaging 6kw) (and fierce summer heat)
Yes efficiency is reduced a little with higher temperature. My household PV panels are mounted 10cms above the roof with open gap. But on a boat no probably too difficult to get cooling gap. ol'will

 

[thinwater]

Good installation you probably get some shading but not much. I had one installation very similar to this.

On my cruising boat I worried about shading. Like the OP, these were installed just to charge the batteries at the dock. This boat is only day sailed. The battery is always up for the tiller pilot.
* No wiring-related neighbor boat problems. I've been burned before.
* Dock wiring can fail with winter ice storms. Also summer thunderstorms. No worries.
* I don't plug in anymore. One less thing to fool with.

It's enough to recharge a low battery in a few days. All I need. On my cruising boat I had 8 times more solar.

When actually cruising, it is common practice to swing the boom clear of panels while at anchor. Easy. You can even lash it to the shrouds.

 

[rich]

I used strong sticky back Velcro for my flexible panel,no problem in the last 2 years.
I haven’t tried to take it off yet.

 

[graham460]

Even a small area of shade on a panel will reduce output to a fraction of what it should be. My tip if you want solar panels under the boom is to get a pair. That way, when one is shaded by the boom, the other is still in full sunlight.

Hi Stemar.. Thanks YES I have ordered 2 pairs 1 pair for the Bow 2 x 100w and 1 pair for the Aft 2 x 70watt thanks

 

[graham460]

Thanks Hi Stemar.. Thanks YES I have ordered 2 pairs 1 pair for the Bow 2 x 100w and 1 pair for the Aft 2 x 70watt thanks It was just what this Other sailor said about the heat on the Plywood that Concerned me Do the Solar cables NEED to be in Conduit when running along the Side of the wood. - They are Tinned cables

 

[Metalicmike]

I doubt that very much. Use an amp meter on the panel and shift the orientation. Definitely more current aimed straight at the sun. Yes in some circumstances like high latitude you may find the best answer is vertical facing south. For over time best delivery but even then would need research to decide best orientation over 12 months.
No I have never heard of panels catching fire. (nothing flamable) (in a community of around 300,000 domestic installations averaging 6kw) (and fierce summer heat)
Yes efficiency is reduced a little with higher temperature. My household PV panels are mounted 10cms above the roof with open gap. But on a boat no probably too difficult to get cooling gap. ol'will

It depends on what is in front of the panels, there is plenty of information out there and it is changing all the time. I am still on the fence about the cost efficiency, (Head in a whirl). I have free shore power so at the moment its not an issue, first step is to increase the storage of that power.

 

[graham460]

I used strong sticky back Velcro for my flexible panel,no problem in the last 2 years.
I haven’t tried to take it off yet.

Thanks Rich But I doubt i could get STRONG Velcro out here I have been to 4plumbing shops and 6 Electrical shops just to find a 16mm Plastic ELBOW nearest was a 16mm Tee from the Chinese Shop It is a jike trying to find stuff

 

[B27]

The panels will lose a bit of efficiency on very sunny days.
That should not matter, because you should have enough panels to generate adequate power on a moderately sunny day.

They will not catch fire.
If you leave a piece of black plastic in the sun, does it catch fire? No!

 

[dunedin]

Are the panels just for keeping the batteries charged when away, or for liveaboard?
Look like massively overspecced if just for keeping batteries topped up - a pair of 50w semi flexible do this fine in Scotland.

 

[thinwater]

^^ As Dunedin says, if this is just to keep the batteries up, you don't need to worry about shade or efficiency. You just need a small trickle and a simple controller. A single 75 panel is plenty. If you are installing solar to cruise, then you need to start by writing down how much power you use. Then determine how much the panels can reasonably put back with the weather and clouds you have where you are and some occasional shading. Maybe 5-6 hours per day at 100% rated capacity. Not all days will be good solar days and the output will be less in the UK, for example.

Before I would build a wooden structure I would buy rigid panels with glass fronts. They will last longer and not have the heat problems. Semi-flexible is something of a fad and is NOT always the correct answer. Perhaps it is usually not the right answer, just easier.

 

[graham460]

Are the panels just for keeping the batteries charged when away, or for liveaboard?
Look like massively overspecced if just for keeping batteries topped up - a pair of 50w semi flexible do this fine in Scotland.

Hello Dunedin.. I was just going by what the Electrician informed me - Ho Was saying best if you could get 500w to Run / Top up batteries. Run your fridge when sailing - rin Navigation gear (Raymarine) Navigation lights Possible Autopilot. (Runs off Battery - Hydraulic) Etc etc.. I will hope to obyain 340 watts But this will drop down with poor efficiency. I have ordered Victron Charge controllers. I think they are 30amp each (I little over the top) Electrician thought I needed 40amp.. Anyway he is not coming around Probaly not interested any more.

 

[graham460]

^^ As Dunedin says, if this is just to keep the batteries up, you don't need to worry about shade or efficiency. You just need a small trickle and a simple controller. A single 75 panel is plenty. If you are installing solar to cruise, then you need to start by writing down how much power you use. Then determine how much the panels can reasonably put back with the weather and clouds you have where you are and some occasional shading. Maybe 5-6 hours per day at 100% rated capacity. Not all days will be good solar days and the output will be less in the UK, for example.

Before I would build a wooden structure I would buy rigid panels with glass fronts. They will last longer and not have the heat problems. Semi-flexible is something of a fad and is NOT always the correct answer. Perhaps it is usually not the right answer, just easier.

Hello Thin Water I was advised by the electrician I should get as much as possible if I am cruising.. Pity I never used the forum before I built the two Wooden frames.. HOWEVER I will take onboard about the Rigid panels = With Glass fronts.. But I spent weeks searching Italy about panels (But that was flexible the sizes wee not quite correct.. NOT too sure what you meanabout GLASS FRONT is that EXTRA Protection.. This is Sardinia Not UK or USA. Difficult enough to find a 16mm Plastic Elbow.. Plus last june I had to go to 5 shops and finally found Wire wool.. I've already paid for the flexible panels and Victron 2 Charge controllers




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