Science/Engineering/Technical forums

Yes both the PVPowered 5200 are grid tie MPPT and work extremely well. As far as effort to cool 72 panels, I think I would just add 10-12 more and be done with it. My issue is going to be the interconnect with APS and the NEC rating on the service panel where the connection will take place. I am already at the service panel bus bar limit without derating the main breaker again, which might be OK as all that is on the panel is a pair of sub panels, 125 amp for the new building and 60 amp for the pair of car chargers.

Yes, I agree - you have a different case due to where you are and the lower angle off horizontal for the panels. I could suggest you mount them a little more off the roof to get the free convection, but it might be just fine as is. I know here the convection is a really big deal for keeping my roof cooler - and my AC loading down.

Sure is a PITA to meet all the codes, eh? I got lucky and got grandfathered in. The building inspector got the full tour of my mess, and when he saw the physics gear and asked how long this had all been working for - he was completely convinced that though I don't meet the NEC, I did *better* than that and know more than he (both are the case). So I got lucky. And it's nice to live in a small town for things like that, at least if you're friends with the other people in it. You get a pass on quite a bit.

Well, I now have a little more practical experience, though some of the numbers are hard to get as I don't have really enough loads to make it crumple during full noon sun, but I'm guessing around 180 amps delivered then if the batteries could take it. The reality on a sunny day is the batteries hit full charge in the early AM, around 10 or so, long before the full sun gets onto the panels. I guess I could use more batteries at this point if I wanted to do more high-draw stuff at night, but I can live without just fine.

The REAL milestone is that today - at 9:45 am, with this soupy clouds and rain where you cannot see the sun at all and don't make a shadow - I'm getting 40 amps (about a kilowatt)...looks like I'm going to have to establish a maintenance schedule for that generator so it gets run a little to keep it in shape! Zowie! If I just do my normal stuff, as in "don't be charging the car in the dark" - I have enough all the time. And this power hog computer is about to be replaced by a new one that draws half the power but is about twice as fast (going from a core2 quad to an i5, lower power draw vidcard too, monitors are the main draw).

Finally finished! After doing the main building, and leaving a bit of room there for a possible hot water solar heater - we had two racks of mixed/older panels left.
The arrangement that had them hanging off the main building panels to the ground didn't work so well - snow, too low, and so on. So we put them on what we call the "office trailer" which is to the north of the main building I live in. Despite being lower in altitude, that spot gets sun in winter when nothing else really does, simply due to the fact that it's that much farther from the treeline to the south - some of which I don't own, so I can't just cut them down (and don't want to cut down the ones between me and the road - privacy and dust control there).
So. Now it looks like this: To put things in perspective, I took another pic from farther to the south. These added panels aren't expected to do much in summer, when I don't need more anyway, most days. But in winter - they get sun the earilest and for the longest, and outperform in diffuse light, which is what we usually have then. Further, that trailer...needs shade on the roof, more than it had, or it becomes fairly unbearable in summer with just fans. Yeah, it has an air conditioner, but we restrict use of that to a few days a year when it's REALLY unbearable - and that's not many days, maybe 6-7 out of a year, when it's over 100f and about 90% humidity. Even I give in at that point.

H/T Mark Thomas, who helped with the heavy lifting and holding. This was actually a little tricky, as we'd placed these up there when we had the crane. They are longer than the part of the roof that will hold weight is wide, so it was a bit of a dance (actually a very accurate jump) to get someone on either side of the racks to lift them up to the angle they are now at. This is not a place you want to miss and land into some very expensive glass! Nor can you just lift one of these aluminum racks from one corner - things will twist enough to destroy panels. But we managed, and at that, by lunch time - and Mark and I celebrated with Margaritas and steaks...He more than earned that, also digging the wire trench (along with some pay, I'm not a bad guy to work for, which is why I get so much help I guess).

Even in the dark (pic taken at 6:30pm, and sun behind the panels) they put out 35-40w. They should do a few hundred in real sun, and most importantly, on those gray days of winter when we need it most.