Bi Facial panels - back reflectors

[EL34xyz]

Hi All,
I have my 6 x 400 watt Bi-Facial panels up and running
They are attached to my Sol-Ark 15k and 6 x LifePower 4 batteries (5120wh x 6)

All is working great

The solar panels are ground mounted on tilting brackets
They are currently set at about 15 degrees for my Lat-Lon and June settings
The expanding legs are not installed yet.

My question is about reflecting light back up onto the rears of the solar panels
Since they are bi Facial, would something white and reflective behind them be beneficial?

If so, does anyone have a product they would recommend?

White plastic like you see used in crawl spaces is what I was thinking?
Just some strips approx 36 inches x 6 feet under each panel?
Or something else very reflective?

I attached an image of my setup
Thanks

 

[400bird]

I am planning to put white gravel around and under my bifacial panels. But, I'm not there yet in the build, so I don't have results yet.

 

[hwy17]

Yes but in that mounting configuration you're not gonna get much back gain with or without white reflector.

Ideal mounting height is like 4ft off the ground. Maybe as low as 2-3ft in 1 panel landscape like that.

 

[EL34xyz]

I am planning to put white gravel around and under my bifacial panels. But, I'm not there yet in the build, so I don't have results yet.

View attachment 153403

That's interesting.
Hopefully you get some reflections off the gravel.

 

[EL34xyz]

Yes but in that mounting configuration you're not gonna get much back gain with or without white reflector.

Ideal mounting height is like 4ft off the ground. Maybe as low as 2-3ft in 1 panel landscape like that.

Not sure I need it, just asking to see if it is worth doing
I did see one day where the Sol-Ark showed that 2480 watts were being produced by the panels

The panels are 400 watts x 6 = 2400 watts
I was getting 80 watts more than they were rated.

 

[DIYrich]

Bleached clam shells.

 

[400bird]

Bleached clam shells.

Is that something you can buy in bulk? Such as for use in landscaping.
A quick search makes me think it is not.

 

[hwy17]

I briefly researched using Perlite the other day, until I learned it floats away in the rain.

Concrete with a skim coat of white plaster might cost effective and long lasting.

 

[Bluedog225]

I was thinking any cheap rock. Spread a layer. Spray with the cheapest white gloss paint you can find. Use a pump sprayer. Renew every couple of years.

but agree, the panels are too low to get benefit of bifacial.

 

[DIYrich]

Is that something you can buy in bulk? Such as for use in landscaping.
A quick search makes me think it is not.

In cap cod you can.

 

[shadowmaker]

Snow seems to work really well with bifacials. When the picture was taken my 44,1kWp system produced 8kW, which is 20%...


If snow isn't an option white paint (or white gravel) will do. Just look at this video.

Of course it would be much better if you raise your panels higher and leave 10-15cm gap between each panel in the row. Also backside production hates shadows from rails, fasteners, etc. If needed you can use bifacials deeper than optimal angle as what you loose in front side production, you gain from backside.

Here's my take on the subject (Bluesun 700W panels at golden hour time, backside, one set of three panels is 150kg and 2,8 x 4m). Unfortunately even here we don't have snow all year round... Best daily winter production so far 333kWh and summer 284kWh, even though available sun hours have doubled. Have thought of using old (=free) metal roof panels on the ground and painting them white.

 

[xjaw4]

Silage tarps are white on one side. The disadvantage of rocks or any irregular surface is the light gets trapped and or reflected away from the array.

 

[42OhmsPA]

This stuff is very reflective and pretty thick.
VIVOSUN Black and White Panda Film, 10' x 100' 5.5 Mil Poly Film, Blackout Tarp for Warm House https://a.co/d/8WiYxpx

 

[Supervstech]

Silage tarps are white on one side. The disadvantage of rocks or any irregular surface is the light gets trapped and or reflected away from the array.

Exactly.
Rocks reflect in random dispersed directions.
You want all sun reflecting at the panels.
A smooth white surface would be good.

 

[400bird]

Yes, an uneven surface would reflect in all directions, that includes rocks that are feet away reflecting sideways towards the array. A smooth reflective surface would need to track the sun or would only function at one time per day, right?

 

[hwy17]

I would think the point of white is that it scatters the light pretty evenly either way, while a mirror would only work once a day. So even an uneven white surface should provide fairly even reflection.

But that's just conjecture.

 

[JLD]

Roofing membrane, last 25+ years.

 

[EL34xyz]

So I have a question about raising my panels up higher since mine are close to the ground

The Sun has to hit the reflective surface from a side angle and bounce up the rear of the panels?
So I would need more height for that to work, correct?

If the sun was directly over the panels, it would beam straight down and not be able to reflect off the surface under the panel?
Just making sure I understand the whole bi-facial rear thing.

 

[Bluedog225]

You understand correctly. Somewhere, this was studied and my memory was that 4’ or so off the ground was good. This could be tough on a roof.

And some go vertical. Handy in places with snow.

 

[EL34xyz]

You understand correctly. Somewhere, this was studied and my memory was that 4’ or so off the ground was good. This could be tough on a roof.

And some go vertical. Handy in places with snow.

Thanks, that clears it up nicely!

So I don't really have to worry about my ground level panels unless I decide to raise them up higher.