New Home Construction System Design

[Tomcat91709]

Ok, so after living in SoCal with our 14 panel, grid-tied but non-battery system, and getting shafted by the CPUC and SCE for years, we're leaving to move to another state.

We do love solar, though, and our plan is to be grid-tied, but primarily a battery-served home, with the option to feed the grid our excess solar production. Partly because we have the impression that NEM is going to go away, nation-wide.

My initial plan is to use a Signature Solar kit, with an EG4 18k inverter, 36 BlueSun 450w bi-facial panels in a vertical orientation, feeding a 6 EG-4 LL-S battery bank. We have 5 acres of land to deploy the panels, though I will have shade issues to contend with, as we live in an area with tall forest trees near-by. The West side of the property is where the forest is. I have attached a plot plan for our property for reference.

I know this system seems like overkill, but since we are putting the system into the construction budget, it works well on affordability.

My question is on orientation of my panels. I have been researching, and keep hearing two views. One group is saying South-facing, and the other is saying East-West. Does anyone have any substantive or authoritative source I can go to for a final answer?

 

[42OhmsPA]

Check out PVWatts, JRC and suncalc.org. They should help greatly with calculations and visualizations.

It's difficult to have an overkill system, you can never have enough

If I were starting over I'd have a primary array facing S and secondary arrays SE and SW pending shading issues.

 

[Tomcat91709]

Check out PVWatts, JRC and suncalc.org. They should help greatly with calculations and visualizations.

It's difficult to have an overkill system, you can never have enough

If I were starting over I'd have a primary array facing S and secondary arrays SE and SW pending shading issues.

This is a great start. I'm going to check these out and I'll post an update.

Thank you so much for your help!

 

[skyking1]

I pose the question:
Where does the most power go in your home?

 

[MichaelK]

Personally, I'd want something a bit higher quality than EG4.

Instead of fretting about array orientation, why not build single-pole rotating mounts like I did. With proper spacing, you can have your arrays facing East, South, or West, whenever you feel like it. The array pictured below can hold up to six large residential panels, in my case 6 X 250W. Built out of unistruts and schedule 40 steel pipe, it ran me about 400$ in steel.

 

[hwy17]

East/West is only beneficial if you have another constraint that benefits from spreading the production out - that would be limited battery capacity or limited amperage somewhere in the system. Or around TOU import rates if you plan to be importing.

But use PVwatts to make detailed comparisons in like the 160-210 range, some places have prevailing weather patterns like overcast mornings that will make west of 180 better. PVwatts uses weather modeling which is what makes it such a powerful tool.

I'd rather have Powerpro's than LL's now. And I'd want 3 of them at least.

 

[EZPZ]

The voc of those panels are 49.6 making 12 of them just under 600v without taking into account the voltage increase with the decrease in temp from 25 degrees c. You will fry the 18pkv above 600v so as soon as the panels drop below 25c (77f). I personally would not do it. This is assuming you will be using the 36 panels in 3 arrays of 12.

 

[EZPZ]

You could do
string 1 - 8 panels
String 2 - 8 panels
String 3 - 10 panels
String 4 - 10 panels

That will work on the 18pkv

Or 4 strings of 9 panels

 

[Quattrohead]

The 18k will take 2 sets of panels in parallel on mppt1, so 2x8 on mppt1 and 10 each on mppt 2 and 3.