Solar newbie post - 32kw off-grid solar diagram, can anyone review?

[PNW_Solar_Guy]

Hey everybody,

I've been reading through a number of threads on the forum, it's great to see so much support on here.

I have very little experience with solar but I would love to learn from some of you much more experienced folk out there on the system we are working on so far.

We have 65 acres in Oregon and were told by the electric company that it would cost $25k to tie us in to the grid. We were already thinking solar down the line, but that grid tie in price tag pushed us over the edge.

We plan to build a farm garage/outbuilding on that corner of the property (where there is no power), and then in a few years build a home next to it. We want this system to be expandable so we have plenty of power for both buildings by that point. But we're starting with just enough power for the garage/outbuilding for now.

I've attached our electrical design file to this thread, as well as a list (below) of the main details. If I'm omitting something please do reply and ask for it. I'm prepared to receive constructive criticism on this, as it's our first go at putting together plans for an off-grid solar system.

System details
Solar Array
Mount type: ground mount (adjustable between 18-65 degrees for our region)
Total panels / arrays (current): 70 / 5
Total kW (current): 32.2kW
Total panels / arrays (eventual): 120 / 9
Total kW (eventual): 55.2kW
Panel info: BlueSun 460w bifacial (model BSM460M-72HBD)
Panel configuration: 7S2P
Notes: Arrays are located exactly 300ft from the solar shed, where the inverters and batteries will be stored

Inverters
Desired AC output: 120/240v split phase power
Inverter model: MPP Solar LVX6048
Total inverters (current): 5 (in parallel)
Total inverters (eventual): 9 (in parallel)

Batteries
Battery model: Pytes LiFePO4 48V 5.1kWh battery
Total batteries (current): 5 (in parallel)
Total batteries (eventual): 20 (in parallel)

Loads
The buried line from the load panels in the solar shed to the garage (and eventually the house too) is exactly 170ft.
For our garage/outbuilding, we expect the loads to be minimal, between 10-20kw/day depending on the work that is being done there. In a few years when the house is built next to it, we expect the daily load to be between 60-80kw/day. We will have our main load suckers (heater, range/oven, hot water heater, dryer) all running off of our LP tank buried outside

I hope this is enough information to paint the broad strokes. I'm hoping to borrow some of your wisdom on this one as I am certain there are element's that I'm overlooking and that I need to dive more deeply into.

Cheers!

 

[nwmark]

Hi, I am new to the forum and are doing something similar to you only on a much, much, much smaller scale. Did you account for the 75% rule when sizing the panels or number of them? I am using 410 watt panels but only expect to get 307.5 watts out of them.

 

[mrzed001]

Very detailed plans

I am missing in this plans:
- over voltage protection for PV and AC (to protect against lightning's effects like LEMP)
- battery main disconnect and fuse


LVX6048 has a 450Voc MPPT. Its ideal working point is about 300Vmpp.
BSM460M-72HBD
- Voc: 50,8V
- Vmpp: 42,4V
- TCVoc: -0,26%/C
So in 7s config this is ideal


With 32.2kWp PV, 25.5kWh battery:
- 25 kWh/day load: 16 days
- 20 kWh/day load: 6 days
- 10 kWh/day load: 0 days
where battery goes empty in a year.

 

[PNW_Solar_Guy]

Hi, I am new to the forum and are doing something similar to you only on a much, much, much smaller scale. Did you account for the 75% rule when sizing the panels or number of them? I am using 410 watt panels but only expect to get 307.5 watts out of them.

Hi nwmark, I did (roughly) account for the power drop. It sounds like you are already aware of this, but each panel's spec sheet shows the power you ought to get out of it in standard test conditions, as well as in more realistic conditions (higher heat, etc). I did my best to account for that in the system design, and I'm curious to view the actual power production--especially based on the season, we have a rather wide gap in solar production capability, vs let's say New Mexico--numbers once the system is set up and running.

 

[PNW_Solar_Guy]

Very detailed plans

I am missing in this plans:
- over voltage protection for PV and AC (to protect against lightning's effects like LEMP)
- battery main disconnect and fuse


LVX6048 has a 450Voc MPPT. Its ideal working point is about 300Vmpp.
BSM460M-72HBD
- Voc: 50,8V
- Vmpp: 42,4V
- TCVoc: -0,26%/C
So in 7s config this is ideal


With 32.2kWp PV, 25.5kWh battery:
- 25 kWh/day load: 16 days
- 20 kWh/day load: 6 days
- 10 kWh/day load: 0 days
where battery goes empty in a year.

Yes thank you, mrzed001! Our revised plans include both of those additional mentioned items!

 

[Railgunner]

Don't forget to consider long term operating costs. Batteries degrade short term, inverters degrade mid term and panels degrade long term. The larger the system the higher the replacement costs will become. Did you prepare the report yourself? Is it a software package that outputs it? Very impressive.