Bifacial solar panel pergola

[jflorey2]

sorry but that is not a good reason to use bifacials.

We have a restaurant down here that has a ~100kW bifacial system that covers their exterior deck. Generates most of the power they use and provides shade while allowing a little light through. People seem to really like it. That seems like a good reason.

[J.P.M.]

I did that very thing, put the panels on normal racking, and then used 2" wide aluminum tape (not half mill thick foil, but real aluminum) and using a pencil as a form for an expansion channel, taped the joints. Been holding for 3 years now.

Un taped:
20160821_090914.jpg


post tape:
20160821_122339.jpg

You can see in the shadow, there is no stripe of light. I just didn't bother to take a pic of the tape

The tape goes on the top side, only on the frame bezel, not on the glass.

FWIW, I've used aluminum duct sealing tape (note : NOT duct tape) in a similar application. After a yr. or so it oxidized (passivated) but is still fit for service after 6+ yrs. I'd only suggest being mindful of the location and panel orientation with respect to future accessibility - much less of a concern w/ ground mounts. There may be some considerations with respect to air flow and its impact on panel temp. and wind loads - perhaps/probably minor but worth considering.

[khanh dam]

elastomeric sealent with a 1" wide by 1/8" thick strip of aluminum or similar on top will probabaly make the sealent much more resistant to UV degredation and heat

[NewBostonConst]

Here is my DYI install at it's current state. Do plan on finishing it more though.

https://photos.app.goo.gl/tMgx5FWJiLqpWpvk8

I didn't want a large inverter hanging out there so we went with Micro Inverters. The clear panel idea I might do on my next but will likely do a steel frame. Spans and loading was done to the same specs as a 2 car garage. We plan on using a elastomer sealer between the panels to keep the water from going through.

Good Luck with your project.

[khanh dam]

that will look nice for a couple of years max and then it will need to be restrained or sealed. but if you like it, contact the makers listed on the webpage.

pergola by Burgurello/Rastelli Construction of Reno, NV. not going to post my files for the whole world, you can figure something out if you really want them.

[jtc331]

no big deal, my pergola is made out of treated lumber and OP seems to be leading towards the modern aluminum ones anyway.
and yes micro inverters/optimizers probably can't be hidden by those narrow aluminum wire troughs to will look messy. metal roof with tounge and groove ceiling is best solution for under panel asesthetics IMHO.

I'm actually not looking to use aluminium; here's an example of one that I think looks quite nice: https://www.altenergymag.com/article...aspergola/1099

[khanh dam]

This board has disabled the PM function.....

no big deal, my pergola is made out of treated lumber and OP seems to be leading towards the modern aluminum ones anyway.
and yes micro inverters/optimizers probably can't be hidden by those narrow aluminum wire troughs to will look messy. metal roof with tounge and groove ceiling is best solution for under panel asesthetics IMHO.

[littleharbor]

If you're looking for some aesthetics I think the micro inverters with all the extra cabling involved will negatively impact your overhead view.

[jtc331]

In your opinion, in what ways do bifacial panels affect aesthetics ?

The underside of standard panels with white backing sheets looks not great IMO; at least I probably wouldn't want it to be the ceiling I look up and see under a for-shade pergola.

The all glass look, as well as the partial light transmission makes it look much better, good enough IMO to be the roof you look up and see. That is, it almost becomes a statement piece rather than a industrial tech installation.

Also, and to the degree that (relative) cost effectiveness is a consideration in all this, if at all, since a panel's production is largely but not entirely f(P.O.A. irradiance), and since most all the irradiance to the underside of a (mostly) horizontal panel is either diffuse or reflected diffuse irradiance, and most of the time that irradiance amounts to somewhere between 5 - 10 % or less of the frontside irradiance, why would paying more than 5-10 % additional $$ for a bifacial panel over a non bifacial panel make financial sense ?

The relative cost effectiveness (per watt) isn't a particularly large factor (though I'm not looking to buy $1.25 per watt "highest possible efficiency" panels), but as I've noted earlier there are some bifacial panels (LongI from CivicSolar, for example) whose cents per watt isn't that much off from a mono panel, so I'm not sure the price has to be huge problem anyway (unless you're comparing to the cheapest per-watt poly panels and have unlimited space, don't count per-panel optimizer cost, racking cost, etc.)

[J.P.M.]

Yes, the reasoning on bifacial panels is largely aesthetic. I am curious where you're getting 35c/w panels though; I've generally seen about 50c/w at the low end, and that's on the cheapest poly panels. I've seen some bifacial panels that rival the cheaper mono panels at 66c/w.

In your opinion, in what ways do bifacial panels affect aesthetics ?

Also, and to the degree that (relative) cost effectiveness is a consideration in all this, if at all, since a panel's production is largely but not entirely f(P.O.A. irradiance), and since most all the irradiance to the underside of a (mostly) horizontal panel is either diffuse or reflected diffuse irradiance, and most of the time that irradiance amounts to somewhere between 5 - 10 % or less of the frontside irradiance, why would paying more than 5-10 % additional $$ for a bifacial panel over a non bifacial panel make financial sense ?

[inetdog]

I don't appear to be able to PM you...unsure if that's because I'm a new user or some other reason.

This board has disabled the PM function in response to a plague of abusive chain referral operations not sanctioned by the board owner.

[Ampster]

My goal currently isn't so much the best possible economics, but to try to also factor in actual ability to avoid net metering/have a system that makes sense even as those situations change.

So the coordination is more so that the existing system knows when to charge the battery. If it's not aware of the second system it could reasonably assume my own demand isn't being met by the solar generation and not charge the battery, even though the other system is already filling the slack, leading to unnecessary export.

Another couple of good reasons. Not to mention it is nice to have all your production data in one place.

[jtc331]

I've never used solar edge products. does combining two inverters somehow make the system more efficient? By spending thousands more on the module level output you will gain the extra thousands of $$$$ back over the 25 year panel life time? It seems like with panel prices being 50 cents or lower it is almost always easier to just add more panels than to try and tweak the system to be even better.

My goal currently isn't so much the best possible economics, but to try to also factor in actual ability to avoid net metering/have a system that makes sense even as those situations change.

So the coordination is more so that the existing system knows when to charge the battery. If it's not aware of the second system it could reasonably assume my own demand isn't being met by the solar generation and not charge the battery, even though the other system is already filling the slack, leading to unnecessary export.

[jtc331]

sunpower is consider one of the top brands in the industry, not cheap panels. the chances of any solar panel maker being in business in 25 years is a total absolute joke. Look at the history of solar panel companies, it's not a small percentage that goes belly up with no warranty cover , it is in fact a huge percentage ,. Combine that with the absolutely horrific resale value and it makes economic sense to self warranty your panels knowing that the warranty is probablay worthless and in 5 years the panels might be worth 1/3rd what you paid. simple math.

You are right about aesthetics, what I meant it was not an economical reason to use bifacials. Personally I would rather spend the money on a real metal roof with a "real wood ceiling" with maybe a few ceiling fans underneath. Much more enjoyable to be under in the hot summer and looks better as well to me. Yes the aluminum pergolas with flush panels looks very modern, but when one compares their price & performance vs something more practical it is a tough pill to swallow.

That's fair; I overstated on the panel quality while mostly thinking about the retail and warranty situation.

Some panel warranties are by a third party, which helps, and some are big enough to survive (LG for example). But it's a fair point that if cheap enough that may not add value.

As to economics, my price comparison originally was much closer, so that's a factor, and bifacials also aren't affected by the tariff, which helps. I'll chew on the different options a bit more; I do want to understand if the original idea is really feasible. I am trying to avoid the look of panels on top of the roof (as opposed to roughly a continuous top or embedded in the roof) somewhat just to see what's possible and somewhat because I hunk it will look nicer.

[khanh dam]

it kinds makes sense for me to use SolarEdge for this also so the inverters can coordinate.

I've never used solar edge products. does combining two inverters somehow make the system more efficient? By spending thousands more on the module level output you will gain the extra thousands of $$$$ back over the 25 year panel life time? It seems like with panel prices being 50 cents or lower it is almost always easier to just add more panels than to try and tweak the system to be even better.