Overheating panels

[MaximusAnonus]

This is more "solar panel" talk but since it's intrinsically linked to residential solar (since this is a non issue on free standing panels IMHO).

There is A LOT of discussion going off in EU solar groups which focus mainly on roof mounted systems about "panels overheating". Especially now when in-roof systems and solar panel tiles are becoming more and more common.
What I would like to know: Is there a way to calculate the heating of panels during let's say a peak summer day (100°F in shade) vs a peak winder day (-5°F in shade)? Will it really kill the panels when they aren't mounted 5-7" above the roof? I mean the higher they get from the roof the sturdier the mounting hardware has to be and it doesn't solve for days when there si no wind to cool under the panels. Plus my DAHs are rated to 85°C. I don't believe even black metal roofs get that hot during summer around here since I can work on them without burning myself (which I would at 85°C).
Is this whole "overheating panels" thing some stupid minmaxing thing?

 

[ncsolarelectric]

It is true that panels perform better when colder. The temperature coefficient is given on the spec sheet for the panel and it's negative. Power goes up as the temperature goes down, and vice versa. A typical 400W panel has a -0.33%/deg-C power coefficient.

 

[MaximusAnonus]

Yeah but that's just derating isn't it? More heat, less power, less heat more power. But this won't destroy the panel or lower it's lifespan in any meaningful way won't it?

 

[ncsolarelectric]

Yeah but that's just derating isn't it? More heat, less power, less heat more power. But this won't destroy the panel or lower it's lifespan in any meaningful way won't it?

No, not at all. What weather panels are wind, dust, and dirt that coats the surfaces.

 

[MaximusAnonus]

That's what I thought. Once this roof mounted system is up and running I'll check the temps. I've already ordered an infrared cam to compare to my ground mounts. I bet there will be little difference.

 

[x98myers7]

Panels absolutely need plenty of air-space around them to keep them cool. I notice a significant loss in peak power when it's hot, sunny and minimal breeze. I'm typcially only ~70% efficient, whereas when cooler/breezy I'll regularly be at 95%+ efficient.

 

[MaximusAnonus]

One thing is loss of power (derating) other is heat damaging panels or even killing them in a few years.

 

[400bird]

Considering panels survive decades without abnormal decay the hot desert sun, I think you in the UK will be fine. Panels are designed to survive the heat.
Sure they aren't as efficient in the heat, but it's not going to damage them.

 

[burgerking]

If space stations are not worried at these levels, I should not worry if my panels go half as hot at 60⁰C
Of course our panels are half as good than those sent up in space, but still should be good enough for earthlings.

 

[sunshine_eggo]

View attachment 117573
If space stations are not worried at these levels, I should not worry if my panels go half as hot at 60⁰C
Of course our panels are half as good than those sent up in space, but still should be good enough for earthlings.

Probably not a valid comparison. Spacecraft solar panels are typically gallium arsenide based, dramatically higher performing, and more expensive than Silicon panels, and that paper wasn't about panel degradation due to heat but how their wild temperature swings affect the temperature of the spacecraft itself.

I will take the position that identical panels in a high heat environment will degrade faster than in a low temperature environment. This is based on my neighbor's 25 year old array. This 1500W array degraded to less than 500W in 25 years in the AZ high desert (10-100°F annual variation). The panels were installed with a negligible air gap between the panels and the roof. Only the ends had a gap. Here's a pic of the dismantling:





Had the installation allowed for a gap at top and bottom, natural convection would have been enhanced, but as it was designed, the racking actually helped to retain heat in the absence of a cross wind. The prevailing winds put the pump house in the lee of the main dwelling, so negligible benefit from the side gaps.

A zoom-in on the cells:




Note the discoloration. Dark brown in the center that fades to the typical purple-ish color towards the edges of the cell. This is damage due to excessive heat.

FWIW, new 6X 330W panels installed with a 5" air gap using a commercial racking system.



Ensuring proper heat dissipation will improve life, but I still expect that two identical installations in notably different climates will see the installation in the hotter climate degrade faster than the cooler climate.

 

[Northernchateau]

Panels absolutely need plenty of air-space around them to keep them cool. I notice a significant loss in peak power when it's hot, sunny and minimal breeze. I'm typcially only ~70% efficient, whereas when cooler/breezy I'll regularly be at 95%+ efficient.

I agree. I am presently trying to run a test on output based on angle but so far temperature seems to play a bigger part.
40 deg F and breezy days have far better output them 70 deg F and calm days. I am going to be very interested to see what the output is like when we get to the 0 deg F days.

 

[MaximusAnonus]

this is more of an anecdote but a long time ago I've seen some photos of a closed loop system that splashed water on panels on hot summer days
it consisted of a perforated tube (very similar to the one I use to water my gardens) and a small pump and a water tank
supposedly it not only kept the panels cool but clean too
a true miracle product lmao