7.920 KW SOLAR PV SYSTEM for off grid use

11JAGAN

Hai Every one!

i would like to run the below load for 12 hours( 8am-8 pm) every day with solar energy ( 10Kva generator for balance 12 hour, which is now taking care of the load for 24 hours)

• 2 air conditioner (12000 btu)-2400w
• 1 desktop computer-350W
• 1 television -40w
• a load of 60w

total load -2850
required energy -34200wh


i would like to use the maximum solar energy

so i designed like this

solar panel-36 x 220w Kyocera Kd220
charge controller-3 x Xantrex xw Mppt 60A (12 panel / charge controller)
Inverter-Xantrex XW 4548

Battery bank-48v,1000Ah ( i think its very small) is it?

my motive is to run the load with solar energy directly, the battery bank is to withstand the load during sudden shading


i need your valuable comments for the above design

will it function good?

Cariboocoot

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

34 kW hours off-grid is a massive amount of power.
You're looking at over 3000 Amp hours @ 48 Volts and 18kW minimum.

Just do the "short math": 34000 Watt hours / 4 hours sun / 0.52 = 16,346 Watt array.

Thirty-six 220 Watt panels isn't going to touch it: 7,920 Watt array * 4 hours * 0.52 =16kW hours.

You're about half size on battery and array minimally and those three Xantrex controllers will not be a good choice for a system of this size.

Re-evaluate those loads, starting with that air conditioner. There's more efficient ones available and when it comes to off-grid power conservation & efficiency is a lot less expensive than generation.

It can be done, but the first question is always "why do you want to?"

Les Nagy

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

To give you an idea of what is needed, I live in one of the best places in the world for solar energy, the Atacama Desert. I have a daily consumption of approximately 7kWH per day and I have 16 x 205 watt panels and I can get around 2900W maximum from my panels. This is sufficient to charge my batteries and run my loads during the day. I can also run my air conditioner which runs around 1500W during solar peak hours when it gets hot.When that happens my consumption is much higher of course, somewhere around 11kWH. You have at least 3 times the load I have, worst case, and live in an area of solar irradiance much lower than I.

Think more like 120 panels of that size and a battery bank that would sink Africa. As Cariboocoot says, reduce your loads first.

waynefromnscanada

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

Les Nagy wrote: »

a battery bank that would sink Africa.

Wow! Sounds pretty big. Would that be expensive? :D

11JAGAN

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

Hi Cariboocoot

first question is always "why do you want to?"

It for an service outlet in off grid location

Actually its an office made of 2 x 20 feet container

Just do the "short math": 34000 Watt hours / 4 hours sun / 0.52 = 16,346 Watt array.

how i calculated was=34000Wh/5 hours sun/ 0.77=8831watt array

8831/245=36 panels

three Xantrex controllers will not be a good choice for a system of this size.

can i know why?

Cariboocoot

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

11JAGAN wrote: »

how i calculated was=34000Wh/5 hours sun/ 0.77=8831watt array

8831/245=36 panels

Okay two things wrong with that: you're counting on more hours of direct sun than you will probably get (remember: direct is not the same as total, and you need to look at the worst day not the best) and the derating factor of 77% does not work for end-to-end calculations on a battery based system. It is 52% when all power is stored in/removed from batteries. This can increase with usage patterns favouring loads powered during charged times. 77% only works for charge controller & array derating or battery-less grid-tie systems.

can i know why?

If you need to us multiple large capacity controllers (such as this system trying to pass 300 Amps) you want to use the MidNite Classics with their ability to fully co-ordinate. Putting in the cheaper Xantrex units will just be a headache as they will not agree on Voltages and charge stage. The more controllers you have, the greater the disagreement. Good luck trying to get it to work consistently without MidNite's "Follow Me" function.

Another way to look at it: your proposed 1000 Amp hour 48 Volt battery @ 50% DOD would supply 24kW hours. Without inverter consumption and conversion derating that falls way short of the estimated 34kW hours spec'd.

zoneblue

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

Are you saying there is no grid power within a mile or more? Thats generally often the cheaper option.

Do have a budget for this 35kWh/day system? Just roughly thats going to be about $60,000.

$60k would go quite a long way to making the structure better insulated etc.

stephendv

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

11JAGAN wrote: »

It for an service outlet in off grid location

Actually its an office made of 2 x 20 feet container

Only a 2 x 20 feet container and you need 2400W air conditioner!!?? You could cool that much more efficiently with a newer mini-split aircon. We have a 48sqm house and the Daikin aircon draws around 400W to cool it. As zoneblue said, it will be much cheaper to better insulate the office and shade it than waste that money on solar.

How are the evening temperatures? Do you need to run the cooling at night too? If not, then you can save a lot on the battery as you'd just need it to carry the much smaller, non-airconditioner load.

waynefromnscanada

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

stephendv wrote: »

much cheaper to better insulate the office and shade it than waste (so much) money on solar.

I could not agree more! Properly done, insulation doesn't fail, break down, or require maintenance and will last the life of the buildings/containers. Install it and forget it.
Properly done, this would drastically reduce your electrical costs, as would dumping your proposed air conditioning units and go with, as mentioned, modern, high efficiency mini-split unit/s.

Rybren

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

stephendv wrote: »

Only a 2 x 20 feet container and you need 2400W air conditioner!!??

I suspect he means that he has two 20-foot-long containers.

11JAGAN

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

Attachment not found.Yes its two 20 feet container

stephendv

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

11JAGAN wrote: »

Attachment not found.Yes its two 20 feet container

Yes, yes, that's a TINY space. Our home is 48 square meters, bigger that two 20 foot containers and as I said, a single mini-split air conditioner cools it easily and draws between 300-600W depending on how powerful the setting is. If we leave it on 24 hours, then it just sips 300W constantly. The key is having a properly insulated and shaded building.

Can you ventilate under that roof? Is the roof over the container already installed- as you can get metal roofing with PU insulation sandwiched in between.

jcheil

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

stephendv wrote: »

Yes, yes, that's a TINY space. Our home is 48 square meters, bigger that two 20 foot containers and as I said, a single mini-split air conditioner cools it easily and draws between 300-600W depending on how powerful the setting is. If we leave it on 24 hours, then it just sips 300W constantly. The key is having a properly insulated and shaded building.

Can you ventilate under that roof? Is the roof over the container already installed- as you can get metal roofing with PU insulation sandwiched in between.

Insulation is gonna be the key. If you already framed the inside, then put an additional 2x6 insulated frame wall around the outside. Or attach furing strips to the outside and then use that 2" thick sheet insulation on the outside and put vinyl siding over it. And insulate the crap out of the roof. And the new mini-splits are amazing. I just installed 3 (2x9000 and 1x12000). As a test I just ran just the 12000 and it froze me out in my 650 sqft poorly insulated 1965 mobile home. I'm consuming about 18-20kwh per day and working out well on a 7.8k array, 740ah battery - but all said and done, about $32k.

stephendv

Re: 7.920 KW SOLAR PV SYSTEM for off grid use

Answering the OPs private message here:

All the major air-conditioner manufacturers have mini-split versions of their air conditioners. You can spot them when they're advertised as having "inverter" technology.
Daikin, Mitsubishi, LG, Panasonic etc.