New project - 100 X 320W panels - some advice please

[DenisJ]

Hi there all,
I'm near to finish my new house project, and because I'm newbie on the PV world, I need some advice please.

Here is what I want realize on the roof of my future house:
I


This because I will need a lot of current for my home consume, greenhouse, water pump, EV car... etc
So practically I want to make a 30-35 kW photovoltaic field on my roof,
and a LiFePo4 battery backup of about 40 kW (16S3P of 280Ah).

The PV panels will have aprox. Vmp= 33.3V / Imp= 9.6A / Voc=40V.
The roof will be South oriented, but only at 14° inclination (best in my zone is 30° aprox).
Here is the result of the production of the PV system:



All connected to the grid and also (if possible) have a quick switch from grid to batt. backup
in case of blackout of the grid power.

I also so a lot of Will Prowse video (thanks a lot Will), but I still not understand
witch is the difference between "MPPT + Inverter" and "Inverter that already include MPPT".

So can please help me with some advice please of witch can be the less cost Inverter for my case,
how many I must buy and how I must calculate the PV strings.
Or maybe if is too complicate, please tell me what I must to search in order to learn more,
and find by myself the near best combination.


Thanks all in advance.
Denis

 

[snoobler]

Confirm with your authority having jurisdiction (AHJ) that you can populate your roof that densely. There are NFPA requirements for rooftop accessibility. Even with off-grid, installations are still subject to building codes, and a rooftop array may be far more expensive than a ground array depending on the AHJ requirements.

If you're grid connected, that's less of a big deal, but if you're grid-tied, i.e., you can export solar back to the grid, then that's another can of worms.

Without knowing what you're going to power, i.e., your peak loads you intend to run with the inverter, we can't recommend anything.

Start with your highest power items and decide how many of them you'll want to run at once.

 

[DenisJ]

Thanks a lot for your answer Snoobler.
Well I don't know what is the low in my country about the max number of panels (Romania)
But I have a friend with 27kW panels on his roof near the place where my house will be build.
Anyway... I must ask someone that know for sure.

About the peak loads, the usual load will be under a kW,
but I will have a heat pump, induction oven, water pump for the greenhouse, PC server
and an EV car to charge (maybe in future will be 2 EV car)
So I think the peak loads will be something like 6-10kW

Here I want to ask, if there is the possibility to power my home with more kW of what is
the grid power.
For example, usually there is 32A of 230V grid power. (7+ kW)
If I have battery bank that is near full, and my home want 10kW for some minutes,
so more than 7kW, is this possible please ?

It will be a grid-tied system (I just learn this expression, thanks).
But I think I will make some home automation,
that will start consume all the curent when will be a surplus.
For example in my actual house I have 8kW pannels and I make a program
that control if the PV generate more than 1kW and if the Tesla PoerWall2 batt.
have more than 90% charge then the Tesla car (70kW) will begin to charge.

Another think... my dream is to go off grid in the future, but for now I don't know
if in the winter time (sometime near -20°C) I can have all I need in the batts.

Again thanks a lot for you help.
Denis

 

[snoobler]

With grid-tie, I don't have any expertise. Hopefully, someone knowledgeable will post.

 

[DenisJ]

Thanks anyway... I still must begin to build the house
...then will be the FV system

Denis

 

[Diysolar123]

regarding the layout, consider putting in a walkway down the middle so you have easy (or at least some) access to all your panels and wiring.
Given that many panels on the roof, perhaps some lightning rods on peak to avoid any accidents from mother nature??

grid tie is "complicated" and depend highly on your local laws...best to start there.

where, and how far, to your battery bank? What voltage do you plan from the solar panels (how many panels in series)to your MPPT?

regarding hardware such as MPPT and inverters:
The MPPT takes the DC power from you panels and converts it into DC power to charge your battery bank. It also tries to take care of your batteries and so have the MPPT feed power to your batteries while at the SAME TIME haing the invert use some of that power can cause some MPPT devices to get confused.

Inverter takes DC power from your batteries (or MPPT) and converts it into 220VAC, they also monitor your grid power and handle transfer from grid to battery as needed.

These two devices can be seperate but as you can see there is some coordination needed between them all.
THis is why it is helpful to have an "all-in-one" device that contains the MPPT, inverter, and battery charger together.
This way the single device has access to everything going on(amount of incoming solar power, grid power, state of the batteries, how much load is on the inverter). It can decide if the current inverter load can be handled by solar,grid, or batteries. What power source should be used to charge the batteries? Do you want the system to focus on charging the batteries with solar even if grid is available? How about always using grid power if its available even if the batteries are fully charged?

These are the kind of things that an all-in-one unit with fancy software can help you setup.

 

[snoobler]

Critical to establish what the regulatory requirements are.

Here, I can't connect to the grid as grid-tie without a contract with my utility. My utility has rules above and beyond code that I must meet before they will approve it.

The technical details matter very little when you have to meet regulatory requirements.

 

[time2roll]

Yes it is possible to do as you describe above. Need to contact the local electric utility about a permit. Also contact your local city government about safety permits. I would assume you are already talking to the city to get a permit for the house itself. Your architect can also help with design.

 

[magic8192]

Another check with the utility. In my area, you can't push that much to the grid unless you are a business.

 

[DenisJ]

Deal all... thanks a lot for your answers, I'll try to explain all your questions.

The law in my country (Romania) let me to take power from the grid and also let me
to inject power to the grid...
In case of inject power to the grid, they pay me every kW at the market price. (now aprox. 60 eu. /mW)

regarding the layout, consider putting in a walkway down the middle so you have easy (or at least some) access to all your panels and wiring.
Given that many panels on the roof, perhaps some lightning rods on peak to avoid any accidents from mother nature??

Yes, I have think about the walkway in the middle of panels, and in this case I can take out 20 from 100 panels in order to have space.
I also will have also a lightning rods on the entire length of the roof, also at the north part of the house I have a lot of tall trees.

where, and how far, to your battery bank? What voltage do you plan from the solar panels (how many panels in series)to your MPPT?

The battery bank will be in the cellar under the house (there will be 300m2 of lab.) so from the peak of roof will be max 10 mt of cable.
But here is my problem... I don't know how to divide all the panels in paralel/series in order to input to the inverters.

I think first of all I must find the inverters that can take care of about 30kWp of panels.
And for this I need all your help please
I can't use a Vectron inverters cause for a system like this one, is too much cost.
I prefer to lose some kW and pay less for the inverters.

THis is why it is helpful to have an "all-in-one" device that contains the MPPT, inverter, and battery charger together.
This way the single device has access to everything going on(amount of incoming solar power, grid power, state of the batteries, how much load is on the inverter). It can decide if the current inverter load can be handled by solar,grid, or batteries. What power source should be used to charge the batteries? Do you want the system to focus on charging the batteries with solar even if grid is available? How about always using grid power if its available even if the batteries are fully charged?

What I want is to:
- use the PV current on my house first of all
- if my house is not consume it, the current must go in the battery bank first until 90% of batts and then inject to the grid
- if the current of PV is not suficient for my house, then I must take the rest from battery bank
- if the current of "PV + battery bank" is not suficient for my house, then I must take the rest from grid
- if the grid go in blackout, the grid must be interrupted automatically and connect it again when the blackout is finish (security/law)
Maybe I forget something ?
So if I understand, to make all this possible I need inverters and not separate MPPTs and separate inverter...did I get it right ?

Return to the system calculation, for example if i buy 3 inverters like this one... can be ok for my system ?
Cause if I drop the 100 panels to 90 panels, I can make 3 string of 30 panels.
30 panels in 15S2P will be 499V and 19A (9590W)... so if I understand the Volt can be ok, but the Amp is too much.
So here I need a lot of you help please. Decide for me like you must pay

Thanks a lot again
Denis

 

[Zwy]

Hi there all,
I'm near to finish my new house project, and because I'm newbie on the PV world, I need some advice please.

Here is what I want realize on the roof of my future house:
IView attachment 41843


This because I will need a lot of current for my home consume, greenhouse, water pump, EV car... etc
So practically I want to make a 30-35 kW photovoltaic field on my roof,
and a LiFePo4 battery backup of about 40 kW (16S3P of 280Ah).

The PV panels will have aprox. Vmp= 33.3V / Imp= 9.6A / Voc=40V.
The roof will be South oriented, but only at 14° inclination (best in my zone is 30° aprox).
Here is the result of the production of the PV system:
View attachment 41844


All connected to the grid and also (if possible) have a quick switch from grid to batt. backup
in case of blackout of the grid power.

I also so a lot of Will Prowse video (thanks a lot Will), but I still not understand
witch is the difference between "MPPT + Inverter" and "Inverter that already include MPPT".

So can please help me with some advice please of witch can be the less cost Inverter for my case,
how many I must buy and how I must calculate the PV strings.
Or maybe if is too complicate, please tell me what I must to search in order to learn more,
and find by myself the near best combination.


Thanks all in advance.
Denis

Panels and mounts are weight, your roof will require not only a weight bearing rating for snow but also the weight of the panels. That can add to construction costs considerably. As the roof slope decreases due to wanting wider house width but keep roof peak lower, the framing under it needs to be increased also. If you have much snow in your area, you will need to either clean the panels off or mount them at a steeper slope so the snow slides off. That is the inherent problem with roof mounted solar in areas of snow, and I've seen the snow pile up at the base of the panels and shade the lower cells. Combine that with winter sun angle and output can be basically non existent.

 

[DenisJ]

Thanks a lot Zwy
I know all that cause I already have a PV system.

Denis