Comments in an earlier thread concerning solar panel operating temperature and the effect it has panel output and particularly on MPPT controller output, led to searching the web for information on actual panel operating temperatures. It’s agreed that panel performance at STC (25C panel temp) does not generally reflect most people’s operating situation. Panels also have a NOCT (Normal Operating Cell Temperature) specification that is closer to what might be seen in real operation, but NOCT is also obtained under tight parameters; irradiance on cell surface = 800 W/m2, air temperature = 20°C, wind velocity = 1 m/s, mounting = open back side.If you have taken measurements on your panel temperature would you kindly post the results including as much information about the situation as possible i.e. date, time, latitude, ambient temp, panel tilted, flat or aimed directly at sun, sky conditions, wind etc. Alternatively, use the calculator below to estimate your temps. Post more than one temp for the extremes you see if you like.While I did not find much on actual operating temperatures, I did find a site that has a wealth of information on solar cells. Everything and more than you ever wanted to know. There are many interactive and animated illustrations.The page on Normal Cell Operating Temperature has a calculator that lets you input your conditions and estimate an operating temp. Using the conditions I usually see returns a temp of less than 55C.Here's a page for Panel Tilt.Here's one for Calculation of Solar Insolation.Thanks for posting your results.

This should be very interesting to follow.

Real life gets in the way. That calculator says we got 816 irr today instead of 1000. I took Isc at noon, panel aimed clear blue, got 8.06a out of rated 8.34 at 1000.800 rating is 6.5a so doing some math, it turns out that 816 should be Isc of 6.9, not the 8.06 I got. Of course Isc goes up with panel temp, not down like Voc does. Not that much though.I did not get the temps to answer the OP question, sorry. I did feel the panel quite warm, well above ambient about 12C. Voc was 34.7 instead of rated 36.8 at 25C which goes with warmer panel

BFL13 wrote:I did not get the temps to answer the OP question, sorry. I did feel the panel quite warm, well above ambient about 12C. Voc was 34.7 instead of rated 36.8 at 25C which goes with warmer panelGuessing your panel NOCT of 45C the calculator gives a panel temp of 37.6C. How do you measure the irradiance?

12thgenusa wrote:BFL13 wrote:I did not get the temps to answer the OP question, sorry. I did feel the panel quite warm, well above ambient about 12C. Voc was 34.7 instead of rated 36.8 at 25C which goes with warmer panelGuessing your panel NOCT of 45C the calculator gives a panel temp of 37.6C. How do you measure the irradiance?I did not measure it, I used your calculator with latitude and date.I used to ASSume I had 1000 if I got full rated Isc, panel disconnected. Now I am not so sure about that, but it still has to be close, since the coefficient isn't much compared with voltage's coefficient.Is panel cell temp same under as on top? I could put a thermometer underneath on the back (raised panel no trapped heat) whereas on top the thermometer would be in the sun, so not sure what it would be showing.

Whatever normal is that is where mine are at. Warmer on hot days, cooler on cold days.I don't see this as a controllable item.

What is your solar panel operating temperature?

25 Replies

harold1946
Explorer
Oct 25, 2013
12thgenusa wrote:
I don't suggest that one would or should fiddle with their panels though out the day, though some do. However, knowing your panel's operating temperature might lead you to explore panel tilt, not only for the direct power gains, but also as a way to mitigate panel temp rise and lower panel losses.

Using the previously posted tenperature of 45C or 113F, how would you propose that one lower the temperature to produce an appreciable gain.
12thgenusa
Explorer
Oct 24, 2013
I don't suggest that one would or should fiddle with their panels though out the day, though some do. However, knowing your panel's operating temperature might lead you to explore panel tilt, not only for the direct power gains, but also as a way to mitigate panel temp rise and lower panel losses.
harold1946
Explorer
Oct 24, 2013
Almot wrote:
What BFL said. Temperature effect is useful to estimate the expected output. Different panels have a different power loss coefficient, see the 3rd table . Those numbers 0.3-0.5 are % of power loss per 1C degree.

At 45C it's not terribly bad, around 12% loss for the most temperature-sensitive panel.

It does not look too bad when considering a single panel,but look at multiple panels, which is the case in most applications. 4-100 watt panels each loosing 12% of their output at 45C equals a total loss of 48 watts.

That would also have to assume that the panels stayed at 45C durring the entire available charging time, which would only happen in a controlled environment
My point is that unless one wants to spend time taking temperatures, adjusting panel angles, doing calculations, and making constant adjustments all day every day, the manufacturers specifications are sufficient for the expected output.
Almot
Explorer III
Oct 24, 2013
What BFL said. Temperature effect is useful to estimate the expected output. Different panels have a different power loss coefficient, see the 3rd table . Those numbers 0.3-0.5 are % of power loss per 1C degree.

At 45C it's not terribly bad, around 12% loss for the most temperature-sensitive panel.
BFL13
Explorer II
Oct 24, 2013
You can't do anything about the temperature, but you can fix your wiring and connections. I would like a way to know, when I am getting fewer amps than I would like, whether it is just the temp doing that to me or if I should be checking for bad connections.

That is important with portable set-ups where you do a lot of connection and wiring changes, but may not be a concern with a permanent installation.

So what are the specified expected amps with 24v panels and MPPT? I was asking about that in another thread.

With 12v and PWM it is panel Isc, but it doesn't work that way with 24v and MPPT. Using the OP data here it seems you could get an idea what to expect for your latitude, time of year(date), and temp
harold1946
Explorer
Oct 24, 2013
BFL13 wrote:
You could use temp data with your own panel's coefficients for a better idea of your "expected amps." Compare with actual amps to see if your system is working right.

Since the coeficiency of a solar panel is controlled by the manufacturer and is not adjustable by the end user.
All the testing in the world is not going to change anything. Temperatures change constantly and power output from solar panels does also.
If I am curious about what the output from my solar array is at any given time I simply look at the monitor.
My "expected amps" are exactly what the manufacturer states under ideal conditions, which seldom happens, and cannot be controlled in a real world environment.
BFL13
Explorer II
Oct 24, 2013
You could use temp data with your own panel's coefficients for a better idea of your "expected amps." Compare with actual amps to see if your system is working right.
harold1946
Explorer
Oct 24, 2013
Since the temperature of panels varies greatly in any 24 hour period, what useful information is to be gleaned?
I fail to understand how gathering temperatures of controllers, solar panels, or solar insolation would be of any practical use.
12thgenusa
Explorer
Oct 24, 2013
Panel temp is not a controllable item. However, panel temperature does affect panel performance and especially MPPT controller performance.

Playing with the calculator or the equation it’s based on gives a panel temp rise of 31C for a typical panel with NOCT of 45C and irradiance of 1000 W/m2. For an irradiance of 800 W/m2, the temp rise is only 25C.

I’m just looking for real measurements if anyone has them and cares to share.
ken_white
Explorer
Oct 24, 2013
smkettner wrote:
Whatever normal is that is where mine are at. Warmer on hot days, cooler on cold days.
I don't see this as a controllable item.

X2...

Forum Discussion

What is your solar panel operating temperature?

25 Replies

About Technical Issues

Related Content

Generator operation

Another solar question.

Water heater temperature

Solar Controllers PWM MPPT Temperature Performance

Freezing Temperatures