Bi-Facials, installation height matters just as much as the angle of the dangle

Jennifer

Electricity kills, think twice before acting.
To all those installing bi-facials or who've watched Will's latest video, here's some additional information I came across as I'm currently putting in 20 Longi 380 watt bi-facials. The lowest spot of the panel's height above ground (or surface) is very important, see attached PDF and screen shots. 1 meter seems to be the sweet spot for uniform coverage onto the backside.

Jen

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Attachments

  • Bifacial_design_guide_Full_ver.pdf
    1.6 MB · Views: 15

HRTKD

Boondocker
Hey, that's good to know! There was a question recently about putting bifacial panels on an RV. This pretty much puts the nail in the coffin on that idea.
 

Jennifer

Electricity kills, think twice before acting.
Hey, that's good to know! There was a question recently about putting bifacial panels on an RV. This pretty much puts the nail in the coffin on that idea.
Yea I'm torn, I have 65 acres in NW Arizona and was going to put them on a 5th wheel toy hauler but it's not worth it unless you never move it and then the racking and height would cause other problems with wind loading, bi-facials need to be right at that 1 meter window for max gain.. which leads me to ask, what about all the gazebo's their putting them on now, i guess if you throw enough panels at it, you make up for the loss... i'll probably just do low racking for all mine, if you're going to do that, you might as well put white rock ect underneath as well... you either do bi-facials 100% right or it's not worth doing at all. As Wills video shows, they're not the gift everyone thinks they are unless you dial them in perfectly.... a lot easier just to use mono's and toss a few extra in than dick around with height,white rock etc... I got mine SUPER cheap or wouldn't have bought them to begin with.
 

HRTKD

Boondocker
Yea I'm torn, I have 65 acres in NW Arizona and was going to put them on a 5th wheel toy hauler but it's not worth it unless you never move it and then the racking and height would cause other problems with wind loading, bi-facials need to be right at that 1 meter window for max gain.. which leads me to ask, what about all the gazebo's their putting them on now, i guess if you throw enough panels at it, you make up for the loss... i'll probably just do low racking for all mine, if you're going to do that, you might as well put white rock ect underneath as well... you either do bi-facials 100% right or it's not worth doing at all. As Wills video shows, they're not the gift everyone thinks they are unless you dial them in perfectly.... a lot easier just to use mono's and toss a few extra in than dick around with height,white rock etc... I got mine SUPER cheap or wouldn't have bought them to begin with.

Yep, sounds like they aren't worth the hassle in your situation. Maybe you could trade them for standard panels?
 

Jennifer

Electricity kills, think twice before acting.
Yep, sounds like they aren't worth the hassle in your situation. Maybe you could trade them for standard panels?
or just use them as regular panels, I got them OOOOOOOOOBER cheap.... and it's not worth the hassle or the risk of damage to mess around with them...
 

svetz

Works in theory! Practice? That's something else
SAM has a module for bifacial panels where you can play with the height, tilt, and albedo (which you can adjust by putting shells, limestone chips, or just painting the ground white).
 

Jennifer

Electricity kills, think twice before acting.
SAM has a module for bifacial panels where you can play with the height, tilt, and albedo (which you can adjust by putting shells, limestone chips, or just painting the ground white).
Yup, there it is again, in SAM, PowerPoint (attached).... 1 meter.

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Attachments

  • sam-webinars-2018-pv-bifacial.pdf
    780.7 KB · Views: 9

eXodus

Solar Addict
Yea I'm torn, I have 65 acres in NW Arizona and was going to put them on a 5th wheel toy hauler but it's not worth it unless you never move it and then the racking and height would cause other problems with wind loading, bi-facials need to be right at that 1 meter window for max gain..
I think that chart states that above 1m (108cm) 4 ft your don't have any additional gain anymore. It's not getting worse when you go higher up. You can put them on parkinglot above the cars and the would work excellent.
 

eXodus

Solar Addict

Fpoet

Solar Enthusiast
Hey, that's good to know! There was a question recently about putting bifacial panels on an RV. This pretty much puts the nail in the coffin on that idea.
I do not have one, but would a highly reflective roof not somewhat help? Like metallic silver
 

svetz

Works in theory! Practice? That's something else
I do not have one, but would a highly reflective roof not somewhat help? Like metallic silver
White probably more than silver. You can get the reflectivity index from a variety of roofs from the cool roof rating council (https://coolroofs.org/directory). Although, given the elevation/clearence required, a roof might not be the best location for them.
 

Jennifer

Electricity kills, think twice before acting.

Hey thanks for that, those are awesome!!!!!

Very interesting... see below
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Jennifer

Electricity kills, think twice before acting.
I think that chart states that above 1m (108cm) 4 ft your don't have any additional gain anymore. It's not getting worse when you go higher up. You can put them on parkinglot above the cars and the would work excellent.
You're probably right, I had read the above PDF I included that you'd lose as you went over 1 meter but I misread, you may not gain any but you don't lose any if I read that correctly... see below

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eXodus

Solar Addict
You're probably right, I had read the above PDF I included that you'd lose as you went over 1 meter but I misread, you may not gain any but you don't lose any if I read that correctly... see below

View attachment 53825
I work in Academia and so I'm used to the lingo. "Bifacial gain would be saturated" - just means - after this point it's not getting more - it's saturated.

When you look at the curves they are flattening- You always have to consider the audience those documents are written for. So this is written for a solar field installer - and every cm higher - is additional material and cost. So they want to know what's the least amount to elevate the bifacial to get gains.

In your and my case - I don't care to make the post of my carport 1m or 4m long . (4ft or 14ft) that's maybe a hundred or two hundred bucks - on a one term expense. The remainder you have to pay anyhow on the racking. Doesn't matter if it's one meter above ground or four.
 

Jennifer

Electricity kills, think twice before acting.
I work in Academia and so I'm used to the lingo. "Bifacial gain would be saturated" - just means - after this point it's not getting more - it's saturated.

Thank you for confirming for me, this is very helpful.... I'm looking at around 45 or 50 foot long by about 16 -20 wide and at least 14 foot tall (for covering a 5th wheel) so it'll be pricey.

Jen
 

eXodus

Solar Addict
Thank you for confirming for me, this is very helpful.... I'm looking at around 45 or 50 foot long by about 16 -20 wide and at least 14 foot tall (for covering a 5th wheel) so it'll be pricey.

Jen
true that's a large structure. I'm looking at building a 20-22ft wide and 30ft long. Got quotes for $4-5k in a steel structure

My comparison was with a ground mound system. The piers in the ground and the racking system is most of the cost - not the length of post.
I'm researching for my farm - what solar system to get.

And figured that for the price of racking and mounting to another building or ground-mount - I can build a carport - with less hassle (permitting of roof mount system is annoying here in Hurricane country Florida) and also create a shaded place for my Class A RV.

It's not cheap undertaking - but not a lot more cost then ground or roof mount.
 

bgflyguy

Solar Enthusiast
Maybe I'm an optimist, but it was interesting to see they were getting gains at only 7cm. With the prices we are seeing for the et solar 410w panels, I thinks it's still worth it for 5-10%.
 
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