Dilemma about solar project

zarapp · October 2018

Hello to everyone .

I`m kinda a crypto enthusiast and during those few years i have been dealing with mining/asics and so on i have made few extra money which i plan to use for solar power and of course lowering my power bill . Right now i have new home with close to 1500 sq. meters free space (with no shade) and planing to start putting up panels there . However since i dont plant to fill it up at once i cant hire a specialist to install everything from me (nor do i want to) so my idea is to install it parts by parts each month or so. So considering i have constant load which i can control (500, 600, 800, 1000,1350 watts) up to 18 Kw i plan something like this:

Panels something like 260-280wp/24v as example . 6-7 panels on each installment and lets say constant load on those panels of 1400 watts .

So my dilemma is this:

Considering a battery bank is charged with 10% of its nominal AH (example 2x 24v/125AH batteries = 25A/24v charger) do i get a MPPT 85 A for those 7 panels and 7 batteries to can have the full capacity of the panels as battery storage and after that with 230v inverter to pull from the battery bank and have the constant load (which of course this setup will be costly , but kinda secure probably since the MPPT should cut off the inverter when batteries run too low )

or

use the same number of panels + the same MPPT and single battery (which on 77amp should destroy it much sooner than expected) and then with the inverter to get the needed load .

Since each constant load isnt connected to the others i think it should be possible to be installed in parts and not get 100-200++ panels at start .

Anyhow i`m open for suggestions if anyone have another idea .

I`m aware of Inverters that can be connected to the panels and the main grid , but cant figure out yet do they need batteries or no . Also i`m wondering about them how they can utilize a load of 1400 for example (with no battery) if the panels at evening produce only 700 ?

I`ll keep reading thru the forum . Maybe someone had the same (or close to it) issue and have wrote some solutions .

Regards

Estragon · October 2018

I think what you're after is a grid-tied inverter that uses solar power, to the extent available, to support loads. I don't think batteries are needed for this.

mike95490 · October 2018

Sadly, doing incremental installs, generally require a new electrical permit, inspection and a new agreement

with the electric company, every time.

zarapp · October 2018

Estragon said:

I think what you're after is a grid-tied inverter that uses solar power, to the extent available, to support loads. I don't think batteries are needed for this.

If i can skip the battery that will be perfect , however so far i have found only inverters that can pull up/monitor the load on the battery and when not enough to start taking from the main grid .

@mike95490 maybe it will sound strange , but where i leave i dont care about the electric company and so on . I have main phase of 13 Kw on my house and backup three phase each of 13 kw . I can make easy breaker boards (on 230v) with as many breakers i need . So basically for my idea i have to install a 12 switch board each with 16A breaker and i`m done . The only thing left will be each time to tie up a batch of solar to a breaker main grid and will have what i need .

Regards

mike95490 · October 2018

Simple Grid tie inverters do not need batteries.

As to the actual install and connection, while you seem to have decides on your chosen path, it may not end up being that simple. Best of luck

zarapp · October 2018

@mike95490 i think its simple enough (well maybe i`m mistaking . After all i have picked this sub-forum for a reason) . If grid-tie inverter is the only thing needed and no batteries then the wiring and installment should be like this:

6 panels 250 w /24v (11 amp) for example . 2 by 2 wired in parallel (maybe i`m mistaking the name , idea is to increase the voltage to 48) and then the 3 pairs wired in series (to increase the amps to 33) . 1 single main cable 10 (cm2? (on 230v wiring 10 cm2 is ideal for up to 13kw (230v/63amp)) which will lead all of those 48v/33amps into a 40 amp MPPT . MPPT will be wired to the DC input on the inverter and one of the 230v breakers will be wired on the 230v input on the inverter . And from the inverted will be that constant load in the range 1300-1400w .

Unless i`m mistaking something it should be straight forward (unless i have to lower the panels to be sure they dont exceed the load from the inverter) .

The perfect idea is to use every single w from the panels and the rest to be from the main grid .

zarapp · October 2018

I mean mm2 for the cable ... not cm2

Photowhit · October 2018

A grid tied inverter will use all available power to push back into the grid, it doesn't care what your loads are! You are basically using the grid as a big battery. The equipment should be just a single unit called a grid tie inverter. It will likely want all 6 panels in a single string and may even require more! It will convert the incoming DC to an acceptable AC to back feed the grid. You will likely need some additional safety equipment, ask your grid electric provider.

Estragon · October 2018

+1 on checking with your local electricity supplier. You may not care about them, but they likely have a lot of control over what (if any) sort of grid-tied system you can install. There is a wide variety of regimes, from some that subsidize power sold into the grid, to those making it very difficult or impossible. Best to check before going much further.

zarapp · October 2018

Ok , i think i maybe didnt make myself clear on the idea i have for the solar panels .

Yes , i have the option to fill out application to sell the solar power to the main grid . However that will stop me from sizing whenever i can (which is probably the thing @mike95490 was talking about as "permits" ) .

Instead i want/need a option where i can use all of the solar power that panels produce and the rest of the needed power to be drawn from the main grid .

So far i have found information that this is possible , but only if there is batteries (solar panels >MPPT>battery>inverter>power from batteries until some point(or some volt range on the battery) and then switch to main grid) .

Also i`m reading right now about the Pure Sin UPS which should be possible to do the very same thing . However i`m not sure yet does that UPS still need batteries (as the above example) or can be used directly .

From what i know about battery banks they are limited to number of charges . However if the constant charge is close to full (in other words the energy just to pass thru them without depleting them) on theory they can last much longer than normal use (which is something i would love to do too since i wont replace them every 1-2 years or so) .

Would appreciate any through from experience .

Regards

Dilemma about solar project

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