This is the "Show and Tell" area, so I am starting a new thread about my next project. The plan here is to add nearly 4,000 watts of panels to my system to get close to 10 KW of total PV panels online. I have a HUGE thread here already from when I added a Schneider XW-Pro to add self consumption time shifting and backup power to my Enphase grid tied system. That thread is out to over 1,900 posts. Here is the link if you want to skim through that.
I am still fairly new on the forum, tried to answer a few questions as I asked some, and have been talking about my plans and purchases. I figure this is the right place to talk about what I am doing and where it is going.
My existing system is a very typical Enphase setup. I have 2 arrays of 8 panels each. The panels are Sil Fab 300M 60 cell units with an iQ7 inverter on each one. All 16 inverters are combined in the attic and go to an Envoy iQ3 on the wall of my garage near the power meter. I am at the limit of a single run with the 16 inverters. I have space to add more, but my...
After adding the XW-Pro and 18 KWHs of Chevy Bolt batteries, I added another 18 KWHs of battery to push it to 36 KWHs of storage and then added 2,000 watts of DC coupled solar panels to try and keep them charged. But with poor weather and more loads, it is just not keeping up anymore. I designed a very streamlined structure to support a 3x3 array of panels. I am still adjusting the exact size of the roof as I have not purchased the panels yet. I am looking in the 300-400 wat range per panel. I am waiting for a reply from Greentech Renewables, but if i don't hear back soon, I may order from San Tan Solar. The y have a few panels in the under 40 cent per watt range. For size and weight distribution with my design, I am looking at the "60 cell" form factor like my original Sil Fab 300 watt panels. The new versions about that size ae now over 350 watts at 1 meter wide and 1.7 meters long. Going 3 x 3 with that size panel, it ends up about 12 feet x 17 feet of panel. At 50 pounds per panel, it is 450 pounds of PV panels alone. Add in the racking and the wood "rafters" and it will be nearly 600 pounds. I don't have to even think about snow load here, so that is a good thing. In deck design, a single 4x4 post can support up to 600 pounds. So 4 posts has a reasonable safety factor. The 4 posts are at the corners of a rectangle just 8 foot x 10 foot. So the solar roof will overhang the 8 foot depth by a bit under 2 feet out the front and back. But in the long direction, it will be just over 3 feet out each end past the posts. Since this is in my back yard, it is north of my house. I am placing it as far west in my yard as I can, leaving room to be able to get the lawnmower behind it. That is the end of my house that is only single story. In the morning, it will get some shade from the second floor on the east end of the house. In spring to fall, there won't really be any shadow issues with this placement. But to get it up out of the shade in winter, the low end posts are 8 feet high, plus 6 inches on the concrete piers. The taller north end posts are 11 feet high on top of the piers. I drew it up at 1/2 inch - 1 foot and it looked like no big deal. But I stood up one of the 11 foot posts today. OUCH. That is higher than I pictured in my head, but it is correct. check out where the sun is hitting it in the pictures.
Here are the pre-cast concrete piers from Lowes.
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That is over a cubic foot of concrete, and they are HEAVY. They are meant for a deck, but I asked and they are also acceptable for "shade structures". I measured out the area, and of course, my yard is not square, and my house is not perfectly straight in the lot. Hmmm. I did my best, and I got it within 1/4 inch of square to the back wall of the house. so it should look fine. I dug the holes. I wanted to go down a full foot, but now I know why I can't grow decent grass. The "dirt" is mostly hard clay with sand in it, and not even 8 inches down, I was hitting hard rock. I managed to get all 4 of them in place and sunk 6 to 8 inches to get them all at the same height.
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If this was in an open field, I would want them deeper to deal with wind, but the structure is all going to be shaded from wind, and with my rock hard ground packed in around the pyramid shape, these are not going to move. A day after I packed the dirt in around one, I tried to pull up on it with a lever. It felt like I was just pulling against a concrete slab, and my lever was over 8:1 and I still could not make it move at all. So I am not going to try and dig them any deeper. I would need a jackhammer to go lower into the rock.
Here are the two west end posts up in position. They are being held vertical by temporary braces and stakes for now.
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At 7 feet off the ground, I will have level 2x6s connecting the 4 posts. Those will have 45 degree braces to the posts as well as between each horizontal bean inside the corners. That will keep everything square and I can then remove the temp braces holding the posts straight.
I took these pics at 4 pm, my rooftop Enphase system was down to just 200 watts from 4,800 watts of panels. In the middle of those 3 pics, you can see where the sunlight is hitting the top 4 feet of the taller north post. The south end post had just gone into shade. Due to how the shade moves in, I plan to split this array. The bottom south most panels are probably going on microinverters as they will have shade issues from time to time. The next row of 3 panels will be in series, and run in parallel with the top 3 panels that are also in series. Depending on the panel voltage I get, I hope to be able to use a 150 volt Victron and not have to get a 250 volt as the price takes a fair jump. 6 x 350 watt panels would be just over 2,000 watts, and push about 40 amps into my "48 volt" battery bank. I will get a 60 or even 75 amp charge controller in case I decide to add another parallel group string of 3 panels up on the wall, or instead of the microinverters on the bottom row. Whatever panels I get, I will likely buy a few extra that I could just lay against the wall and wire in for winter. I still have my BougeRV charge controller that would be perfect for that use.
Bridging between the 8 foot and 11 foot posts, I will have a 16 foot 2x8 that end up tilted 16 degrees towards my house. Due to the angle, it will extend less than 3 feet past the posts. I may also add a few braces of 1x4 between the level 2x6 and the long tilted 2x8. There will also be 6 2x4s between the long tilted 2x8s where the 6 Iron Ridge rails will go across. I was hoping to get away with the 11 foot rails, but that depends on which panels I get. The 375 watt panels I am looking at are listed at 41.34 inches wide. Put 3 of them against each other and that is 10 foot 4 inches. So I would have 8 inches to allow for 1 inch between panels and a couple inches for end clamps. But if I go with the 430 watt panels, they grow to 44.6 inches wide, and just the panels alone is then 11 feet and nearly 2 more inches, even with no space between the panels, OOPS!! I can't find anyone who sells 12 foot rails, they jump to 14 foot. The price difference is not huge, so I may go with the longer rials so I can go with larger panels later if I decide I need more power. I really would like 400 watt panels.
I had thought about also tipping it a bit more west for evening sun, but the heading of my house is already about 25 degrees west, and I think that is plenty far as I watched the sun set today. So the other pair of posts are exactly the same as the first pair. The solar panel roof will just be leaning towards the house. The low end does go a little lower than the edge of the house roof, but it is over 10 feet away. Even on the winter solstice, the sun was on the closer 8 foot post for over 5 hours. It gets better sun than the panels on the garage roof. All the panels I am looking at are the "Half Cut" type, so on that bottom row, even if the sun blocks the lower half, the top half will still produce well. The upper end of the lowest panels will still above and north of the lower posts. The 375 watt panels are just 70 inches long, less than 6 feet. So the gap between the first and second row of panels will be 2 feet inside of the space between the 2 posts standing in the pics.
