hello from NJ

[secondhandluck]

Just getting started with a 7kw system here in NJ. I've been scrounging the components for a while and am trying to do this as inexpensively as possible. I'll probably post some questions after I lurk some more..
So far, I have 7kw worth of sunpower 305 panels, roof mounts for my barn, and a few spools of 10awg use2 wire. I'm a contractor/ fabricator/welder by trade, so much of this is familiar territory.
It's pretty simple to do as straight grid tied, but my desire to run a hybrid inverter for battery backup complicates things. Certainly threatens my budget.
Anyway, cheers.
SD

 

[Deleted member 165]

I grew up in Upstate NY, not far from you. It can be a challenging place for solar for 5 months a year or so.

 

[MichaelK]

Well, if you like to weld, I can show you pics of my unistrut arrays, which I'm very proud of. As a real welder, I'm sure you could do a better job than me. I use manual tracking to point the arrays east to west on days when I need maximal power. Tracking will help you get past a storm that seriously depletes your batteries. I grew up along the Delaware River, so I know what NJ winter weather is like. In my pic I'm showing an array with four 250W panels mounted vertically. With slight design changes you could squeeze six of your 305W panels mounted horizontally.

Depending on what Voc your system components can handle, you could make four 6-panel arrays. Each array could be wired either as 3S2P or 6S1P, though in below freezing weather, your Voc would be >300DC for 6S1P. Only the most serious charge controllers can handle DC that high. But, even a set of arrays wired for 3S8P would give you a series voltage high enough to run wire 100+ feet to the controller(s).

With that many panels, most systems would be overwhelmed at noontime by too much amperage. Using virtual tracking, you could point one or two arrays SE, with another one or two SW. On poor solar days, you could postion all the arrays towards weak sun if you're really low on power.

 

[Deleted member 165]

With that many panels, most systems would be overwhelmed at noontime by too much amperage. Using virtual tracking, you could point one or two arrays SE, with another one or two SW. On poor solar days, you could postion all the arrays towards weak sun if you're really low on power.

Respectfully, that is not true as long as the system is wired properly and the correct components are used. There are plenty of systems larger than 7kw. A system that is over amperage at noon is a poorly designed system.

 

[secondhandluck]

the current design has three strings of 8 panels wired in series, each string @440V/ 5.58A at average temp. I prefer this approach as the higher voltage limits my wire loss between the array and inverter (about 150').

 

[MichaelK]

Respectfully, that is not true as long as the system is wired properly and the correct components are used. There are plenty of systems larger than 7kw. A system that is over amperage at noon is a poorly designed system.

Sure, you can say that, but I am still astounded by the incrediably poor choices/advice some people make. I was just on another site today where someone was trying to design a 4000W system, and a poster recommended a battery no larger than 80AH.

Just on this site, last month, there was some guy that put together a 2000W system, and wired into 20AH batteries.

In my own case, I had what was supposed to be a properly balanced system, till the day I drove to the battery dealer to buy the Trojan IND9 batteries I wanted, but he refused to sell them to me. I could only buy them if I would pay for an entire pallet worth (18 batteries).

I've since found a new dealer in a town about 45 minutes away that lets me purchase the numbers of Rolls batteries I want. He even delivered them right to my door.

Designing a proper system is not exactly the same as putting together a proper system.

 

[Deleted member 165]

So you put together a crap system because you have trouble sourcing the components? ? 100 amp, 50 amp, what's the difference? Don't sweat the details, man.???

 

[MichaelK]

Being insulting is unprofessional.