To Bi-Facial or not Bi-Facial

[Y2KINDYZ]

Hello everyone,
My question is the following: I there a benefit in Using Bi-Facial solar panels in a hot sunny climate? I am located in northern mexico / south texas. I was all set with getting 36 of these from Signatur Solar

Preorder - 16.56kW Pallet - BlueSun 460W Bifacial Solar Panel (Silver) | Up to 575W with Bifacial Gain | Full Pallet ( 36 ) - 16.56kW Total

solar panels, pv, solar, bluesun, 460w, 460, 400w, mono, monocrystalline, 20% efficiency, solar-residential

signaturesolar.com

Then I watched one of Will's videos and he mentioned that Bi-Facial panels don't work well if they get too hot. Would I be better off with these https://signaturesolar.com/solarever-455w-split-cell-mono-perc-solar-panel-silver-full-pallet-31/ ?

I was planning on using 3 EG4 inverters. Four, 7-panel strings for 2 EG4's for the house and two 4 panel strings and 1 EG4 for a smaller system to run stuff in a barn. That is a total of 36 panels. I will have 6 server rack batteries. 5 batteries for the house and 1 for the barn.

Any thoughts or comments will be appreciated,

Oscar

 

[Danke]

Where will they be shipped to? Or are you doing local pickup?

 

[BentleyJ]

Then I watched one of Will's videos and he mentioned that Bi-Facial panels don't work well if they get too hot. Would I be better off with these https://signaturesolar.com/solarever-455w-split-cell-mono-perc-solar-panel-silver-full-pallet-31/ ?

This is where "words mean things". Did he specifically say the bi-facials were less tolerant to heat than other panels or was it just a reminder comment about solar panels in general regarding the negatively correlated Temp/Voltage relationship. In cold weather panel voltage goes up and in hot weather panel voltage, thus output watts, goes down.
The datasheet for the specific solar panel model number will list this coefficient its generally something like -0.3% per degree C. The lower the coefficient the less it will be affected by temperature changes. The answer to your question will be found by comparison based on the published specs.
Also, when comparing panels note that their output will go down year by year. A quality panel manufacturer will include information related to expected panel degredation and there can be significant differences. Many times the lowest cost panel is not the best long term value.

 

[Y2KINDYZ]

Where will they be shipped to? Or are you doing local pickup?

Shipped to South Texas

 

[Danke]

Shipped to South Texas

If shipped or picked up in Texas, you will pay sales tax. So add > $700

 

[OzSolar]

Any thoughts or comments will be appreciated,

I didn't see ground or roof mount?

Generally speaking unless you are doing a ground mount on a carefully prepared site AND doing regular seasonal tilt adjustments you aren't going to get any meaningful annual kWh gain from Bi Facials. So don't pay extra for them if that was a question. They be will just fine in the heat so don't "sweat" that.

Cunningham's law says that I'm about to get dog piled for saying that. lol

 

[Solar Guppy]

There is no difference in the cells of solar panels that are bi-facial, its just the backing doesn't have tedlar and has glass instead. So at worst, it add nothing but no performance declines in any situation.

 

[Danke]

Someone posted a guy doing an experiment recently and found bifacials did out perform regular panels.

Edit: I think this guy:

 

[Y2KINDYZ]

I didn't see ground or roof mount?

Generally speaking unless you are doing a ground mount on a carefully prepared site AND doing regular seasonal tilt adjustments you aren't going to get any meaningful kWh gain from Bi Facials. So don't pay extra for them if that was a question. They will just fine in the heat so don't "sweat" that.

Cunningham's law says that I'm about to get dog piled for saying that. lol

Thanks OzSolar,
These will be a ground mount application. Been thinking of adding the ability to tilt the array. But tilting a 36 panel array will take some effort. Looking at a slip post with holes for specific angles and using a bottle jack to lift.

I do not know Cunningham's law, please fill me in. Similar to Murphy?
The Bi-Facial were actually Less $. Pallet includes 36 vs 31 Panels. It also allows me to max out 2 of the EG4's and add a single EG4 to run a dedicated A/C for a Food Storage room in the barn, plus a few lights if needed I am sure.

 

[Y2KINDYZ]

Someone posted a guy doing an experiment recently and found bifacials did out perform regular panels.

Edit: I think this guy:

Great Video. I will stick with the Bi-Facial Panels. I am getting them as part of Singular Solars Off-Grid kit. So they will ship for free.

Main concern for my question was heat causing lower output, but that concern was answered by BentleyJ. Thanks again to all I am sure I will have more questions as I begin to install in the near future.

 

[Solar Guppy]

One nit pick on the video.

The original panels of the array are mono, but not half cut cells, that is a big difference, half cuts have lower voltage loss and less effected by heat. The tested bifacial are half-cut.

My arrays are half-cut ( not bifacial ) and is the best performing array I have ever built, and I have had a few over the years and being roof mounted bifacial would not have any ability of getting reflected light on them. High ground mount is the application of bifacial, though not sure the $$/Watt is better.

 

[OzSolar]

I do not know Cunningham's law, please fill me in. Similar to Murphy

Oh the perfect set up! Thank you. lol

 

[OzSolar]

One nit pick on the video.

The original panels of the array are mono, but not half cut cells, that is a big difference, half cuts have lower voltage loss and less effected by heat. The tested bifacial are half-cut.

My arrays are half-cut ( not bifacial ) and is the best performing array I have ever built, and I have had a few over the years and being roof mounted bifacial would not have any ability of getting reflected light on them. High ground mount is the application of bifacial, though not sure the $$/Watt is better.

Right, yeah that really wasn't much of an experiment. It was a nice YouTube video though. One day out of the year doesn't really tell us about the entire year. Sorry to nit pick.

Here is an actual published experiment from NREL. Assuming you get nice a base of white rock down under your array, bottom line is that you might get get somewhere around 6% - 9% more energy annually so don't spend too much extra money or time fiddling with seasonal adjustment.
Set it for the angle your modeling shows that your monthly kWh production will be short and go on about your day.

 

[Warpspeed]

I would not get too excited about published efficiency figures.
Sure its nice to think you are getting slightly more than someone else is getting, but that is just state of mind....

Its really watts per dollar.
And you might do better with using older less efficient used panels, and installing twice as many for half the cost.
If you have the available space to install them of course.

If you have a boat or a camper, sure go for premium panels.
But for a home installation with lots of available roof area, I would be looking more at watts per dollar.

 

[Danke]

More panels, more racking + possibly more micros or RSD/Optimizers.

 

[Warpspeed]

Its still watts per dollar.....

 

[OzSolar]

I'll offer that it's probably more about kWh per dollar.

With TOU metering becoming more common it's about when it saves you the most money. Extra kWh during the months you're already in surplus aren't worth much.

 

[Warpspeed]

kWh depends on location, and weather, and time of year, not much you can really do about that.

Rated watts (under standard conditions) are what you pay for and install.

 

[OzSolar]

kWh depends on location, and weather, and time of year, not much you can really do about that.

Rated watts (under standard conditions) are what you pay for and install.

That's all news to me. Thanks for pointing that out.

 

[svetz]

...Will ... mentioned that Bi-Facial panels don't work well if they get too hot...

You can't judge all bifacials based on off-hand comments.
Compare the temperature coefficient in the datasheet to whatever alternative panels you like to see how they'll compare temperature-wise.

Monocrystalline panels are typically the best for hot climates. For example, the SunPower (Maxeon) X-Series have a Temperature Coefficient: of -0.29%/degree C.

If you're not familiar with the temperature coefficient calculations there's an example in the FAQ post Figuring out how many panels in series and parallel based on your MPPT. At a 70°C panel temperature and insolation of 6, on a 10kW array the difference from -.36% to -.29% is ~2.4 kWh/d. But also factor in economics, it might be cheaper to buy more panels with a -.36% to make up the power loss.

It also works the other way; that is on cold days the panels make more than their rated power. So, if you have more cold days than hot days and need more power in the winter anyway.... than a larger temperature correction factor might be the way to go. A tool like SAM can help you figure that out.