Solar Pergola Racking Recommenation

[ametrine]

If anyone is interested, I worked with a company that supplied me with alumawood patio cover, and they got me the structural stuff sorted out with a cover letter stamped by a PE. I can supply the details if its needed by anyone.

[heimdm]

I would be interested in that option.

[ametrine]

@heimdm, Give James a call on 800-xxxxxxx. If he wants a point of reference (since it was about 2 years back that I bought) then say the name Richard that did solar, and he can probably design something similar. Their website is actually www.try-tech.com and in fact the first picture you see is my patio cover.

Mod Note: Please do not attach phone numbers to your post.

[ametrine]

@heimdm, I tried to post the info, but it may not get approved (perhaps a violation of terms here?). If you can perhaps PM me, then I can pass it on I guess.

[heimdm]

It's been awhile, so thought I'd give a quick update. The yard was sloped a pretty good amount so that was dug out and retaining wall was constructed along with utilities trenched in. Being in southern Indiana, there is quite a bit of large rocks/limestone. This slowed down the excavation quite a bit. At this point, I am waiting for our electric company to give approval of the interconnect. We lucked out with the mild weather, that this was able to be completed in December/January.



image1 (1).jpegimage4 (1).jpeg

[heimdm]

Just another update. Duke Energy has sure taken their time on the interconnect agreement. Originally submitted back in November, and today they finally submitted it to their technical review team. They wanted the address on the one line diagram to not have "South" on the street name. Just a lot of wasted time and a little frustrating. Hopefully this means by the end of this month we will have confirmation of how much power that will let us backfeed.

[heimdm]

Quick update:
- Received Duke Energy Interconnect agreement. They approved 36.8 kW (DC).
- Purchased LG Bifacial Panels LG405N2T-J5 (transparent backsheet). I got them for $250 a panel. That comes out to $0.61/watt. I had prices for REC around $0.48/watt. It was either all black panels or transparent from a visual perspective. Since we plan to use the area under the structure as a patio, having some light under there was preferred.

[bcroe]

I am guessing, the PoCo brought a feed for a small service building for your inverters,
and DC lines go from there to the panel array? With that low angle, the inverter AC
capacity may be well below the panel peak rating. As for snow sliding off, good luck.
Here at 42 deg Lat in IL, that only happens with temps not much below freezing.

Give the distances involved, you might want to calculate (ohms law, etc) how much of
the generated solar power will be lost in wire resistance getting to the meter. That was
substantial here with the distances involved, but heavier wire eventually got the AC and
DC total below 3%. Bruce Roe

[heimdm]

We are fed by 50 kvA transformer, and we are the only ones on it. Our angle will be 15 degree's, which optimally would be about 2x that. I am in southern indiana, which for the past 5 years, we have not got much snow. So, if there is an uptick in snow in the area in the next couple of years, you can blame me.

We did add extra panels to make the winter performance not as bad. My intent is that we will underproduce during the winter months (Nov-Feb). Until 2032, we have net-metering. Once we get past that, we might add some panels at a steep angle on the ground, to offset winter (December, January). Bruce, what kind of performance do you get during the winter months? Trying to determine if the energy is worth hunting during a Midwest winter.

The distance between the inverters and grid interconnect is about 75ft. Current design calls for 4/0 wire. Always appreciate your insights and feedback.energyUsage.png

[khanh dam]

Purchased LG Bifacial Panels LG405N2T-J5 (transparent backsheet).

I'm surprised you got a plastic backsheet, glass is going to be much more durable. Hopefully they last 25+ years.

If anyone is interested, I worked with a company that supplied me with alumawood patio cover, and they got me the structural stuff sorted out with a cover letter stamped by a PE. I can supply the details if its needed by anyone.

Yes I would love that option, but this forum does not allow private messaging, please post link? Never mind I see it was already blocked. this place is locked down more than a maximum security prison.

[heimdm]

Hopefully the backsheet holds up. Found this as a good comparison between dual glass and transparent backsheet.
JinkoSolar: Transparent backsheet vs dual glass--- Advantages and disadvantages | PV Tech (pv-tech.org)

The modules have a 25 year warranty.


In the account -> privacy settings there is an option to enable private messaging.

[khanh dam]

Jinko makes crap panels with white backsheets that crack and fail. I wouldn't trust their data on a transparent back sheet at all.
I'm pretty sure transparent backsheets have just come out in the last few years, there is no 20 to 30 year samples we can point to as a success. hopefully they work and lg is around that long if warranty is needed.

Anyways that will be amazing once done. What are you using for the rafters? I assume it will have to be metal since the span is so long? I'm guessing 2x6 steel with 1/8" wall. please let me know as I'd love to make a similar project latter on.

[heimdm]

Will do for sure. I should have design specs for the steel structure in the next couple of weeks. With it finally starting to feel like winter, not too much will be happening from a construction perspective until March would be my guess, as concrete foundation work is next.

[bcroe]

We are fed by 50 kvA transformer, and we are the only ones on it. Our angle will be 15 degree's, which optimally would be about 2x that. I am in southern indiana, which for the past 5 years, we have not got much snow. So, if there is an uptick in snow in the area in the next couple of years, you can blame me.

We did add extra panels to make the winter performance not as bad. My intent is that we will underproduce during the winter months (Nov-Feb). Until 2032, we have net-metering. Once we get past that, we might add some panels at a steep angle on the ground, to offset winter (December, January). Bruce, what kind of performance do you get during the winter months? Trying to determine if the energy is worth hunting during a Midwest winter.

The distance between the inverters and grid interconnect is about 75ft. Current design calls for 4/0 wire. Always appreciate your insights and feedback.

75 feet with 25 more for both end terminations (mine took more than that), gives about a
200 foot loop, 0.049 ohms per 1000 feet of copper 4/0 wire. With 36.8KW (92 400W panels),
a lower angle Cos of .95, and an inverter + DC wire efficiency of 0.95, an inverter AC output
of 33.2KW is possible. At 250VAC line that is 133A, causing around 1.3VAC drop in the loop,
or 0.5% power loss, a pretty good number. Increase that by about 1.6 if the wire is aluminum.

For my 42 Lat midwest, mid winter KWH production is about 1/3 my mid summer production.
The main factors are much shorter days, much more prevalent clouding, and a poor seasonal
elevation angle on fixed sections of the arrays. The seasonal increased clouding is the
biggest thing, with cloud dispersed light the angle matters less. A few days ago the array
under excellent sun produced about 57% of the best summer day ever, but 10% on the
worst day.

I clear snow after every storm, not so hard with my design. That will be nearly impossible for
you, so a good part of winter production may be lost. That is a smaller part of the picture,
but it is large enough to get me out pushing snow (manually), in between cleaning paths
(with a tractor).

I see no practical way to bring winter production up to summer levels, so net metering is
the essential bridge here. It might be possible to reduce the need by building a new super
insulated house.

With a given ground area, the same energy may be collected by covering it with flat
panels, or by a considerably reduced number of panels elevated to the angle to
intercept that sunlight on a perpendicular. With optimal mounts costing more than
panels these days, I see nothing wrong with using lots of flat mounted panels on
that existing pergola.

If you do add ground mount panels later, you might consider something like I built
here after half a decade of experiments. The elevation may easily be changed
seasonally, both for production and to minimize snow accumulation. This winter,
this array has stayed snow free, while my conventional array required 5 cleanings.
Note the high ground clearance to avoid snow accumulation.

The next of these arrays will be 2 sided, to replace a decade old wooden support
section. Going this route with string converters, you could arrange to collect a lot
more energy with a lot more panels, while still using your original inverter plant
and AC wiring. That is done here by east directly facing the rising sun, west
facing the setting sun, with the other panels taking care of mid day and boosting
output under clouds. Peak energy will not increase, but the number of production
peak hours a day will jump. My best unclouded day produced 10.5 sun hours.
Since only a fraction of the panels are at peak at any one time, the same inverters
will handle near the same output, over a longer day.

Expansion here is based on panel strings totaling 720 cells, about 360 VDC in
summer, 420 in winter. I am less concerned with the exact panel arrangement
or voltage specs, all my varied 720 cell strings play nicely together. Just need
a combiner box with more inputs. Mine has 12 strings, will take 14.

I see arrays of large X by Y panel numbers. These DO NOT save ground space,
but they make it impossible to change the tilt or clear the snow. Designs here
are for 2 high landscape mounted panels, set at a steep angle for winter, any
convenient length, arrays. More panels = more length, NOT height. What snow
does collect, is easily reached with a pusher. Yes more foundation and support
structure is needed, my back and snow pushing mid winter dictate my tradeoff.
good luck, Bruce Roe


Array20Rear1.JPG

[heimdm]

A little setback today. Thought I had the LG bifacials all squared away. Distributor went to order them, and LG will only ship those modules for commercial projects. My backup module at this point is the REC Alpha Black module.