Are black solar panels less efficient?

[DavidH]

So I'm in the market for 4 solar panels. I'm kinda limited by what is available here in PR but I came across 310W mono panels that are all black. I'm aware that panels are less efficient when warm and so wondered if the black color has been proven to affect the efficiency of these panels?
The other panels I'm eyeing are Q Cells 385 Watt Mono Duo Cell Solar Panels - these just look like the standard ones with a white background and aluminum frame. Which brings me round to the question if I painted the tops and exposed front of the aluminum frames with highly reflective white roof sealant would that increase efficiency by keeping everything cooler?

The other choices are HT-SAAE, Preimar, Canadian Solar (375W) and Longi Solar (360W). Any advice or things to look out for would be appreciated. I'm already wanting to check for salt mist resistance and a decent warranty.
Thanks

[Mike90250]

I suspect the amount of heat reflected from the small area of painted white frame, is not worth the bother, or voiding your warranty. In a salt mist area, warranty is important, along with using the factory supplied mounting holes and not drilling any new holes (modified the panel, warranty void)

[DavidH]

That's a good point Mike, I hadn't even thought about the sealant voiding the warranty. It definitely won't be worth it then.

One of the interesting things I found about the Q Cells 385 Watt Mono Duo Cell Solar Panels, is that although they state "Salt-mist corrosion test in accordance with IEC 61701, severity 6." when you look at the warranty they state the following:

The Limited Warranty shall not apply to any Q CELLS Modules affected by the following events or conditions:
4. damage caused by extreme environmental sources of impact, including, but not limited to ... (iii) saline air.

Which pretty much means the warranty doesn't cover any salt mist damage despite the passing of the test right?

Edit: I'm wondering whether the black frame is powder coated and whether that would naturally make it more resistant to salt air.

[foo1bar]

I'm aware that panels are less efficient when warm and so wondered if the black color has been proven to affect the efficiency of these panels?

Yes.
I think the manufacturer usually compensates for this with which cells they use, so that their 310W white-backsheet panels are producing the same power as their 310W black-backsheet ones.

Which brings me round to the question if I painted the tops and exposed front of the aluminum frames with highly reflective white roof sealant would that increase efficiency by keeping everything cooler?

I would not paint anything.

[J.P.M.]

So I'm in the market for 4 solar panels. I'm kinda limited by what is available here in PR but I came across 310W mono panels that are all black. I'm aware that panels are less efficient when warm and so wondered if the black color has been proven to affect the efficiency of these panels?
The other panels I'm eyeing are Q Cells 385 Watt Mono Duo Cell Solar Panels - these just look like the standard ones with a white background and aluminum frame. Which brings me round to the question if I painted the tops and exposed front of the aluminum frames with highly reflective white roof sealant would that increase efficiency by keeping everything cooler?

The other choices are HT-SAAE, Preimar, Canadian Solar (375W) and Longi Solar (360W). Any advice or things to look out for would be appreciated. I'm already wanting to check for salt mist resistance and a decent warranty.
Thanks

All other things being equal, the more solar energy a device or object absorbs by virtue of its "blackness", the warmer it will become. If that device or object is a PV panel, the warner it becomes, the less efficient it will be with respect to input/output.

There are many other considerations besides temp. in panel and also array design but in general, the darker the panel, the more heat needs to be considered in the panel and array design.

[ButchDeal]

All other things being equal, the more solar energy a device or object absorbs by virtue of its "blackness", the warmer it will become. If that device or object is a PV panel, the warner it becomes, the less efficient it will be with respect to input/output.

There are many other considerations besides temp. in panel and also array design but in general, the darker the panel, the more heat needs to be considered in the panel and array design.

On top of this PV manufacturers put their top tier (most efficient) cells in the Black on White modules. So each year the BoW are generally 5w more than the BoB modules at about the same price.

So take panasonic as an example the BoW currently widely available are 330watt and 325w but the BoB available are 325w and 320w. (latest hard to get are BoW 340w and 325w)
If you were to compare the PTC of the 325w BoB to 325w BoW
The 325W BOB PTC is 302.4W
The 325W BoW PTC is 306.8W

This may be a poor example using panasonic as their thermal coefficient is so low though...other modules with higher thermal coefficient would have larger difference.

https://na.panasonic.com/us/energy-solutions/solar/hitr-black-series/n325k-photovoltaic-module-hitr-black-40mm

https://na.panasonic.com/us/energy-solutions/solar/hit-panels/n325-photovoltaic-module-hitr-40mm

[J.P.M.]

On top of this PV manufacturers put their top tier (most efficient) cells in the Black on White modules. So each year the BoW are generally 5w more than the BoB modules at about the same price.

So take panasonic as an example the BoW currently widely available are 330watt and 325w but the BoB available are 325w and 320w. (latest hard to get are BoW 340w and 325w)
If you were to compare the PTC of the 325w BoB to 325w BoW
The 325W BOB PTC is 302.4W
The 325W BoW PTC is 306.8W

This may be a poor example using panasonic as their thermal coefficient is so low though...other modules with higher thermal coefficient would have larger difference.

https://na.panasonic.com/us/energy-solutions/solar/hitr-black-series/n325k-photovoltaic-module-hitr-black-40mm

https://na.panasonic.com/us/energy-s...dule-hitr-40mm

The practical result and outcome of a higher %age of solar absorbance (or lower %age of solar reflectance) by virtue of the panel having a higher %age of surface area of a dark(er) color.

[MPPT_Rob]

In my testing of a 100 watt Poly and 100 Watt Mono side by side it really depends on the air temperature - In the cool mornings the Poly had higher output power but as the air warmed and the sun heated the panels the Mono won out. Over the course of the day however the total energy metered was nearly identical.

Peak readings were 95 watts for the Mono and 86 Watts for the poly at mid day at about 80 degrees air temperature. However early and late the numbers looked like this:
Mono 34 watts and Poly 42 watts.

This testing was done with our Apollo model charge controllers and a precision energy meter. A/B swap was also performed to validate the difference was from the solar panel and not from the controller.

So I would say in a hot climate the Mono is a better choice but where the days get short in the cold winter the Poly is a better choice. Largely due to the temperature variance is less with the Mono panels than the poly panels.

Cheers,

Rob
< moderator deleted signature > Rob, please leave your self promotion at home

[ButchDeal]

In my testing of a 100 watt Poly and 100 Watt Mono side by side it really depends on the air temperature - In the cool mornings the Poly had higher output power but as the air warmed and the sun heated the panels the Mono won out. Over the course of the day however the total energy metered was nearly identical.

Peak readings were 95 watts for the Mono and 86 Watts for the poly at mid day at about 80 degrees air temperature. However early and late the numbers looked like this:
Mono 34 watts and Poly 42 watts.

This testing was done with our Apollo model charge controllers and a precision energy meter. A/B swap was also performed to validate the difference was from the solar panel and not from the controller.

So I would say in a hot climate the Mono is a better choice but where the days get short in the cold winter the Poly is a better choice. Largely due to the temperature variance is less with the Mono panels than the poly panels.

Cheers,

Rob

OP is not comparing mono to poly but is looking at mono BoB vs mono BoW...

[J.P.M.]

In my testing of a 100 watt Poly and 100 Watt Mono side by side it really depends on the air temperature - In the cool mornings the Poly had higher output power but as the air warmed and the sun heated the panels the Mono won out. Over the course of the day however the total energy metered was nearly identical.

Peak readings were 95 watts for the Mono and 86 Watts for the poly at mid day at about 80 degrees air temperature. However early and late the numbers looked like this:
Mono 34 watts and Poly 42 watts.

This testing was done with our Apollo model charge controllers and a precision energy meter. A/B swap was also performed to validate the difference was from the solar panel and not from the controller.

So I would say in a hot climate the Mono is a better choice but where the days get short in the cold winter the Poly is a better choice. Largely due to the temperature variance is less with the Mono panels than the poly panels.

Cheers,

Rob

Any data on (panel temps. - amb. air temp. as f(POA irradiance, wind vector) ?

[MPPT_Rob]

Air temp was about 80 degrees that day, very little wind less than 5 mph, full sun mid day in Southern Lower Michigan mid June. The Mono and Poly were side by side and each had a calibrated power meter on the controller. My point in all of this was to highlight the differences between the two - total day's energy though was nearly identical less than 1% difference. Cell temperature measured with a Fluke 62 IR Thermometer was about 60 degrees C (140F).

It can come down to color preference or cost when deciding on which one as they both perform well.

Cheers,

Rob
< moderator deleted signature > Rob, please leave your self promotion at home

[J.P.M.]

Air temp was about 80 degrees that day, very little wind less than 5 mph, full sun mid day in Southern Lower Michigan mid June. The Mono and Poly were side by side and each had a calibrated power meter on the controller. My point in all of this was to highlight the differences between the two - total day's energy though was nearly identical less than 1% difference. Cell temperature measured with a Fluke 62 IR Thermometer was about 60 degrees C (140F).

It can come down to color preference or cost when deciding on which one as they both perform well.

Cheers,

Rob

Thank you.

What are the dimensions, length X width for mono and poly panels ?
Are the panel dimensions the same ?
What is tilt and azimuth ?
Each panel's STC power output ?
Any irradiance measurement capabilities ?
Any wind vector measurement capabilities ?

There is more to consider than instantaneous or day long output when defining performance.
The poly panels will probably suffer faster and perhaps greater long term performance degradation than mono panels.
While the ploy panel's acquisition cost may be less, the poly panel's area efficiency is generally less which may be a problem in space constrained applications and can also make racking and installation more expensive.

[MPPT_Rob]

Most of what you ask is in my original post - Both were 100 watt STC ratings. The Mono Cell is 33 cells and the poly 36 cells. while the electrical ratings are the same I find they behave different in real world conditions. Both are made by windy nation and bought off Amazon for demonstration purposes at outdoor shows we do - you can look them up easily. The Mono is taller but narrower.

As for tilt they were facing south with about a 45 degree tilt and sun elevation was about 68 degrees at peak. I do not have any wind or irradiance measurement devices but it was a very clear, calm day in June of this year.

As for your other comments - I am not experiencing degradation with 7 year old Poly Panels from Canadian Solar - just measured the 245 STC watt panel output at 216 watts output power with our Apollo model MPPT controller on a sunny day. Given the cell temp and assuming full sun that works out about right to a calculated power. all 12 of my panels are measuring between 212 and 220 watts peak power out of the controller in full sun mid day... these have been in full service 24/7/365 for 7 years now.

Most companies rate their panels at 25 or 30 years to 80% power output regardless of if its Mono or Poly type... so I think those differences are long gone with advances in manufacturing.

As for space requirements - its maybe at most a 5% difference for a given wattage... not like it used to be 7 years ago.

Even the cost discrepancy between the two is not that much anymore - in fact my 100 watt mono cost LESS than the 100 watt poly I bought last year.... both available for under 100 dollars shipped to USA address.

For hot climates I would lean towards Mono and cooler climates / cloudy a lot with the Poly.... though either one will work well as my total days output shows.

The single biggest difference is the operating voltage at MPPT is a bit higher with Mono versus Poly.... again not huge as the controller takes care of the power conversion.

Cheers,

Rob

(admin note, I removed your self promotional sig line,if I see it again you will be on a long holiday)

[littleharbor]

MPPT_Rob, Not sure if you're seeing the Admin. editing of your posts. You need to look at the one above this post here. I think you have a lot that can be contributed to this forum but you can not advertise here. I look forward to reading more of your posts so hopefully your advertising will be removed from your future contributions.

[J.P.M.]

Most of what you ask is in my original post - Both were 100 watt STC ratings. The Mono Cell is 33 cells and the poly 36 cells. while the electrical ratings are the same I find they behave different in real world conditions. Both are made by windy nation and bought off Amazon for demonstration purposes at outdoor shows we do - you can look them up easily. The Mono is taller but narrower.

As for tilt they were facing south with about a 45 degree tilt and sun elevation was about 68 degrees at peak. I do not have any wind or irradiance measurement devices but it was a very clear, calm day in June of this year.

As for your other comments - I am not experiencing degradation with 7 year old Poly Panels from Canadian Solar - just measured the 245 STC watt panel output at 216 watts output power with our Apollo model MPPT controller on a sunny day. Given the cell temp and assuming full sun that works out about right to a calculated power. all 12 of my panels are measuring between 212 and 220 watts peak power out of the controller in full sun mid day... these have been in full service 24/7/365 for 7 years now.

Most companies rate their panels at 25 or 30 years to 80% power output regardless of if its Mono or Poly type... so I think those differences are long gone with advances in manufacturing.

As for space requirements - its maybe at most a 5% difference for a given wattage... not like it used to be 7 years ago.

Even the cost discrepancy between the two is not that much anymore - in fact my 100 watt mono cost LESS than the 100 watt poly I bought last year.... both available for under 100 dollars shipped to USA address.

For hot climates I would lean towards Mono and cooler climates / cloudy a lot with the Poly.... though either one will work well as my total days output shows.

The single biggest difference is the operating voltage at MPPT is a bit higher with Mono versus Poly.... again not huge as the controller takes care of the power conversion.

Cheers,

Rob

(admin note, I removed your self promotional sig line,if I see it again you will be on a long holiday)

Without a pyranometer and, depending on pyranometer setup, a way to convert GHI to POA irradiance, and a way to determine panel temp. as well as a way to determine how clean a panel is or is not, it i9s not possible to claim to know what panel degradation is.

I do all that and more, including an approx. site correlation for wind influence on average array temp. I've got my hands full. About the best SWAG on panel instantaneous efficiency I can get after ~ 6 years of close to ~ 1,000 readings on clear days and recording of instantaneous data on a 1 minute basis under all conditions and times, as well as 6 additional measurement events done the same way of at least 40 daily data sets, but each of those events done after daily array cleaning on days and at times of day (usually ~ 20 minutes past solar noon, when the cosine of the angle of incidence on my array is calculated and visually verified to be > 0.99, about the best I can claim for accuracy on fouling or instantaneous efficiency +/- ~ 0.75 % (latest clean set data done 07/02 - 09/04/19: min. 0.007, max. 0.008, std. dev. 0.004, N = 44). That's done using and assuming the data sheet annual performance degradation of 0.40 %/yr., and using (0.004/365 per day average panel efficiency degradation since startup on 10/17/2013. Over the years, the data seems pretty consistent.

Point is, with incomplete data, particularly irradiance data, but also cell temperature data, you can claim you've not experienced any degradation but you have no way to back up that claim.

Even with more data and instrumentation, most panel's published annual degradation is small enough to get lost in the noise of measurement.