2V or 12V dilemma

[Sunking]

Need a little help here

8kw system
8000 watt inverter 24v
800 watts of solar panels
500 Ah 24 v Battery bank?
40 amp mppt charge controller?


Loads
Washer 1150 (2hrs maximums a day)
Fridge 840 (intermittent all day)
Television 240 (5hrs continuos)
A/C 2300 (10hrs continuos)
Water pump 2900 (10 secs) 30 times a day

I am in the Bahamas so I have about ten hours of sun in the winter and thirteen hours of sun in the Sumer
Is this an adequate system??

Not even a remote snowball chance in hell's it will work. You do not even have a down payment made yet.

First problem is you do not have 10 or 13 sun hours. No place on earth has that much sun. In the Bahamas for an off-grid system you have 4.5 Sun Hours in winter is the number we have to work with.

Second problem, and it is a huge very expensive problem, is you are a huge energy hog when it comes to off grid demanding:

Washer 1150 (2hrs maximums a day) = 2300 wh
Fridge 840 (intermittent all day) = 2500 wh assuming 33% run time
Television 240 (5hrs continuos) = 1200 wh
A/C 2300 (10hrs continuos) 23,000 wh

Total = 27,812 wh/day.

In your location that will require:

Panel Wattage = 10,000 watts, you only have 800.
MPPT CHARGE CONTROLLER = 2 units of 80 amp operating at 48 volt battery. You only have a single 40 amp controller.
48 volt Battery Capacity = 2800 AH or 7500 pounds worth. You only have 250 AH @ 48 volts and 600 pounds worth
Generator 10 Kw you do not have.
48 volt, 200 amp AC charger for generator you do not have.
500 to 1100 gallon LPG tank or 200 to 400 gallon diesel tank for generator you do not have.

With what you have can run the fridge or washer, but not both. Or you could run the TV for 10 hours. Take your pick.

[ChrisOlson]

If you use 5.7 you will be dark with no power and dead batteries from August to March. Or you could run your generator every day from late August to March.

Pretty interesting conversation here. Not much I can add to what Sunking has already said. Except for the above. Many of us that live off-grid in the north DO actually run our generators every single day during the dead of winter. This is the logged data for our system for the month of December in 2013 showing genset input to our power system vs PV input (6.75 kW installed capacity):



We could install 40 or 50 kW of solar capacity and it still would not meet our loads in the winter. The generator is way cheaper than continuing to throw solar panels and more batteries at the problem.

[Dagr8one]

Not even a remote snowball chance in hell's it will work. You do not even have a down payment made yet.

First problem is you do not have 10 or 13 sun hours. No place on earth has that much sun. In the Bahamas for an off-grid system you have 4.5 Sun Hours in winter is the number we have to work with.

Second problem, and it is a huge very expensive problem, is you are a huge energy hog when it comes to off grid demanding:

Washer 1150 (2hrs maximums a day) = 2300 wh
Fridge 840 (intermittent all day) = 2500 wh assuming 33% run time
Television 240 (5hrs continuos) = 1200 wh
A/C 2300 (10hrs continuos) 23,000 wh

Total = 27,812 wh/day.

In your location that will require:

Panel Wattage = 10,000 watts, you only have 800.
MPPT CHARGE CONTROLLER = 2 units of 80 amp operating at 48 volt battery. You only have a single 40 amp controller.
48 volt Battery Capacity = 2800 AH or 7500 pounds worth. You only have 250 AH @ 48 volts and 600 pounds worth
Generator 10 Kw you do not have.
48 volt, 200 amp AC charger for generator you do not have.
500 to 1100 gallon LPG tank or 200 to 400 gallon diesel tank for generator you do not have.

With what you have can run the fridge or washer, but not both. Or you could run the TV for 10 hours. Take your pick.

POCO says my average daily power consumption is between 7.0 to 10 kW
However this was during a time I was using an inductor cooker (I am now using a propane stove)

I do have a generator it is rated at 5550 running watts and 7350 starting watts ( this can supply my daily usage without peaking ( except when the water pump kicks in, which running for a few seconds a time)

I have already purchased a 24v 8000 watt pure sine inverter and I am now trying to calculate battery and panel wattage

[ChrisOlson]

I have already purchased a 24v 8000 watt pure sine inverter and I am now trying to calculate battery and panel wattage

A 24V 8000 watt inverter? Holy balls! How big are the wires going to that thing? And how many wires are feeding it? I hope the answers, respectively, are: "big" and "lots".

[Dagr8one]

A 24V 8000 watt inverter? Holy balls! How big are the wires going to that thing? And how many wires are feeding it? I hope the answers, respectively, are: "big" and "lots".

Well!! The inverter came with two dc input (two positive and negative terminals) I was thinking about six feet of 0 gauge wiring x2

[paulcheung]

You need 4000 AH batteries to run this monster properly. I love to know how this system turn out.

[russ]

Well!! The inverter came with two dc input (two positive and negative terminals) I was thinking about six feet of 0 gauge wiring x2

You should sit back and study while making a totally new start. Right now you are in the ready, fire aim mode.

[Sunking]

I have already purchased a 24v 8000 watt pure sine inverter and I am now trying to calculate battery and panel wattage

Then you are a fool and will loose a lot of money.

General rules of thumb.

• Inverter Wattage shall be no larger than panel wattage. That means you need a minimum 8000 watt panel. That will cost you $15,000
• For battery maximum load current = C/8. A 8000 watt inverter on 24 volt battery will require 350 amps of current which means you need a minimum battery of 24 volts @ 2800 AH, or about 4000 pounds of battery and $13,000 worth of batteries.
• 8000 watts of solar panels on a 24 volt battery will require a minimum of 4 very expensive 80 amp MPPT Charge Controllers at $800 per unit cost, another $3200 out of your pockets
• You will also need a 8 Kw genset, 500 gallon LPG tank, and a very expensive 300 amp 24 volt rectifier. Another $10,000 out of your pockets.
• Then you will need a copper mine to supply a few thousand pounds of very heavy copper wire, buss work, Switches, breakers, and distribution. ext. Another $10,000

Here is the real fun and educational part. In 5 years you get to replace $13,000 worth of batteries.

Have fun, you got what you asked for. SCREWED! You just went from paying the POCO 11-cents per Kwh to over $1.00 per Kwh. Enjoy.

[Mike90250]

..I have already purchased a 24v 8000 watt pure sine inverter and I am now trying to calculate battery and panel wattage

You are going to want to return that and get a 48V model, if you ever expect to pull more than 2Kw from it.

[hataf]

How much solar panels I need

It's really wonderful thread to learn about the solar capacities. Sunking's answer's are very help full.

I need advice on that, How much solar panel watts do I need to charge 12 x 2 v @ 500 AH Battery.

1200 watts/hr consumption

Currently I have the following

1. 3 kv PWM Hybrid Inverter with 50 AMP charge controller
2. 1600 watts solar panels
3. 12 x 2 v @ 500 AH Battery ( Coming in few days, I have fed up with lead acid and dry batteries 12v )

Sun shines averagely in Faisalabad - Pakistan

Nov-Jan 9 hrs 25 C - 5 C
Feb-Apr 10.5 hrs 18 C - 36 C
May - July 13 hrs 33 C - 47 C
Aug - Oct 11 hrs 29 C - 42 C