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bifacial panels any drawbacks?

rockwind1

Natural selection intervention specialist
Joined
Nov 19, 2020
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85
Location
Az
local solar guy was warning me about bifacial panels, said he didn't approve, he's been in the biz long time. thoughts? maybe they can't handle hot climates?
 
local solar guy was warning me about bifacial panels, said he didn't approve, he's been in the biz long time. thoughts? maybe they can't handle hot climates?
Think more he like to sell old junk first.

The only drawback i know of it that it need to go from the ground .
So you have to set them higher from the ground.
So on a roof or on a flat roof of een rv than you can go for the classic solarpanels.
 
local solar guy was warning me about bifacial panels, said he didn't approve, he's been in the biz long time. thoughts? maybe they can't handle hot climates?
They work great power wise but seem flimsy. As long as what you have them mounted too is structurally sound I wouldn't worry about them being a problem. Compared to my normal panels they weigh less and flex more easily. Power output is nice.
 
They radiate heat from the back,
making my patio 10-15* hotter.
Working great for 2 years now.
63# for the 395W bifacal canadians
43# for 365W Qcells
Do you think bifacial will radiate heat on a flat roof flush mount 5 inches from the roof? Also do you have any gain on your setup? thanks
 
They work great power wise but seem flimsy. As long as what you have them mounted too is structurally sound I wouldn't worry about them being a problem. Compared to my normal panels they weigh less and flex more easily. Power output is nice.

I think some bifacials are actually heavier. The 450 Watt Boviet Vega's are over 68lb .
 
Do you think bifacial will radiate heat on a flat roof flush mount 5 inches from the roof? Also do you have any gain on your setup? thanks
I would assume yes,
My panels have never put out 100% rating, my temps definitely hurt output.
 
One spec that caught my attention is the thickness of the front glass with the standard panel at 3.2 mm & a bifacial at 2 mm. this is comparable panels , both 600W from the same manufacture. The weight as well. With the bifacial at 32 kg & the standard at 28 kg. The claimed efficiency is 22.30& for the bifacial & 23% for the standard ??? Maybe a typo in the datasheet ? What should I be looking at to compare ? ISC or VOC ?
For me, the glass thickness is an issue thinking about hailstone impact.
 
Hi

I am on the fence about these as well. I need to understand a few things:

e.g 700 Bifacial:
Case 1: Flat on a black not reflective roof
Case 2: Same bifacial, say mounted at angle, 40 inches from the plane of a reflective white painted concrete roof, for exemple
  • Will they deliver the same amount of power?
  • What would be the difference?
  • Another way to ask the question: Is the quoted max power measured without taking into account the gain from the back?

Help from the collective will be much appreciated.

Zep
 
Do you think bifacial will radiate heat on a flat roof flush mount 5 inches from the roof? Also do you have any gain on your setup? thanks

All solar panels typically have little or no insulation value so all panels will get hot(on both sides) and radiate heat from both sides.
 
Hi

I am on the fence about these as well. I need to understand a few things:

e.g 700 Bifacial:
Case 1: Flat on a black not reflective roof
Case 2: Same bifacial, say mounted at angle, 40 inches from the plane of a reflective white painted concrete roof, for exemple
  • Will they deliver the same amount of power?
  • What would be the difference?
  • Another way to ask the question: Is the quoted max power measured without taking into account the gain from the back?

Help from the collective will be much appreciated.

Zep
Bipanel power rating is only for front side. You can get additional power depending how much reflected light can hit backside: Example 1 there's not going to be much backside production, but example 2 may get you something like +10-20%. Albedo is the word used to rate surrounding reflectivity.

First I added some white glossy plastic around my panels and got ~15% more production.
20240919_184611.jpg

So decided to paint the whole landscape white to get even more production...
20241101_082809.jpg
 
Bipanel power rating is only for front side. You can get additional power depending how much reflected light can hit backside: Example 1 there's not going to be much backside production, but example 2 may get you something like +10-20%. Albedo is the word used to rate surrounding reflectivity.

First I added some white glossy plastic around my panels and got ~15% more production.
View attachment 255494

So decided to paint the whole landscape white to get even more production...
View attachment 255495
That is great! But you made a mistake in example 2, you added the snow but removed the SUN. I think that might hurt your production.
 
All solar panels typically have little or no insulation value so all panels will get hot(on both sides) and radiate heat from both sides.
I can’t believe I didn’t get around to this while it was still hot.

Someone a while back measured heat under bifacial and the roof got no benefit from the partial shade.

But I still wonder if a roof is cooler under the shade of a regular panel.
 
One drawback might be charge controllers will need to sized according to VOC which might be higher on a bifacial panel. Most bifacial will increase current but not VOC however the VOC spec might be higher than a comparable sized non bifacial.
 
Weight appears to be one key difference.. W bifacials weighing roughly 5-10% more.

Maybe a non-issue for smaller installations, but definitely a consideration in larger and/or roof mount installations.
 
My 700W bipanels are ~39kg each, but there are similar size bipanels weighting only ~29kg, so I guess it varies greatly. For roof installation light would be ideal even they probably are little weaker than heavier panels.

I had to use excavator installing my 3x700W preassembled sets as they each weight around 150kg and the top is 5m high.
first panels.jpg
 
My 700W bipanels are ~39kg each, but there are similar size bipanels weighting only ~29kg, so I guess it varies greatly. For roof installation light would be ideal even they probably are little weaker than heavier panels.

I had to use excavator installing my 3x700W preassembled sets as they each weight around 150kg and the top is 5m high.
View attachment 255822
Big toys. I like big toys. So much fun and make $.
 
All of my bifacials are a bunch lighter in weight than similar sized normal panels.
I'll second that. Just last month I added array of four 200-watt bifacial panels and was surprised at how light and "thin" feeling they appeared. My first thought was, "Are they going to shatter during the next hail event?"
They sure do perform though! I've witnessed a high of 942 watts, as displayed on the new charge controller I had to buy. My Midnite 200 Classic is maxed out. That's about an 18% gain over the 800-watt rating if my math is right.
 
All solar panels typically have little or no insulation value so all panels will get hot(on both sides) and radiate heat from both sides.
The monofacial panels (at least some of them) have a white back sheet. White radiates less heat than black, considerably less. Here is an example (Canadian Solar CS6R series):

1731728400515.png

With the white backing, the roof will get less heat radiated to it.

In my brief testing using an IR thermometer, the roof tile under the panels was quite a bit cooler than the tile exposed to the full sun. This means the panels are actually reducing the roof temperature and thus saving cooling load on the house as well. The panels had about 5 inches of roof clearance so there is good airflow under the panels.

If you buy bifacial and put them on the roof, they will radiate more heat since their backside is black. Your roof will be hotter than the monofacial with white back sheet. I would not buy bifacial for a flat to roof install.

Mike C.
 
Very interesting data point Mike.

Q1: If the mono-facial are not radiating/transmitting as much heat to the roof times, does this mean those panels are hotter and therefore experiencing a reduction in solar production as the temperature reduces their conversion efficiency?

Q2: Or are those panels radiating the thermal energy out through the front of the panels?

Q3: Are there any formal studies that have explored these dynamics?
 
A1: It seems logical the heat goes somewhere, so it probably does raise the panel temperature a bit. I doubt it does it much since I think the majority of the heat is convection through the air and not radiated. I don't have a bifacial panel to compare to, so what the surface temperature delta is unknown.

A2: I suspect mostly by convection through the air, especially if on a tilted frame or inclined roof. I would think totally flat panels would suffer the most since there is no natural chimney effect to aid in the airflow exchange.

A3: Not that I am aware, it is mostly basic physics, though.

Mike C.
 
Very interesting data point Mike.

Q1: If the mono-facial are not radiating/transmitting as much heat to the roof times, does this mean those panels are hotter and therefore experiencing a reduction in solar production as the temperature reduces their conversion efficiency?

Q2: Or are those panels radiating the thermal energy out through the front of the panels?

Q3: Are there any formal studies that have explored these dynamics?

The panel temp would have to be hotter since a white backside reduces radiation cooling/heating. No matter if air cooling or radiation cooling one side black and one side white will cool less then 2 sides black.

It might be interesting to take a IR camera on a running solar panel of each type in full sun and compare the IR temp of the front and back. I have some ground mount bifacial ones that I can get back and front temps off the next time I get full sun.
 

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