Solar Powered Deep Freezer Fridge

I already have the Freezer/Fridge so buying a new one is out of the question. 

BB. said:

For a standard fridge/freezer--The 1,000 Watt inverter may or may not reliably start the compressor--Typically, 1,200 to 1,500 Watt is recommended for reliable compressor operation.

And, we do not know how much energy the freezer will use as a refrigerator... Just to be relatively conservative, lets guess 500 WH per day. 2 days of storage, and 50% maximum discharge (longer battery life) on a 12 volt battery bank:

• 500 WH per day * 1/0.85 AC inverter eff * 2 days storage * 1/0.50 max battery discharge * 1/12 volt battery bank = 196 AH @ 12 volt battery bank

So--While you should be able to run with a 200 AH @ 12 volt battery bank (2x 6 volt @ 200 AH golf cart batteries)--With a flooded cell battery, I would recommend a 480 AH @ 12 volt battery bank to support ~1,200 Watt starting load (AGM can use the 200 AH @ 12 volt battery bank).

Suggest 5% to 13% rate of charge for battery bank--And 10% or more for full time off grid (vs weekend/seasonal system usage). The solar array for such a battery bank would be:

• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.05 rate of charge = 452 Watt array minimum
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.10 rate of charge = 903 Watt array nominal
  
• 480 AH * 14.5 volts charging * 1/0.77 panel+controller deratings * 0.13 rate of charge = 1,175 Watt array "cost effective" maximum

Note, the larger the battery bank, the larger the suggested minimum array.

Then there is sizing array based on energy usage and by season... You did not say if this was for backup power, full time off grid, inside or outside, generator backup, other power usages (LED lighting, cell phone charging, laptop computer, etc.)... A nominal system design would look like (assuming Missoula Montana):
http://solarelectricityhandbook.com/solar-irradiance.html

Missoula
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 43° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
2.66	3.75	4.71	5.12	5.13	5.41
Jul	Aug	Sep	Oct	Nov	Dec
6.11	5.90	5.20	3.93	2.86	2.37

Normally, toss the bottom three months (assume generator use for bad weather--And for a refrigerator out on the back porch, energy usage may fall in freezing weather), pick February as "break even month":

• 500 WH per day * 1/0.52 off grid system eff * 1/3.75 Hours of sun per Feb day = 256 Watt minimum array (Feb break even)

If, you expected 500 Watts per day, and little to no genset backup, then you should run daily power usage to 65-75% of designed power output (to allow for some bad weather), and if you pick December as break even month:

• 500 WH per day * 1/0.65 daily power usage * 1/0.52 off grid system eff * 1/2.37 Hours of sun per Feb day = 624 Watt array minimum (12 months per year)

If we go back to suggested minimum solar array for battery bank (based on starting surge current), it was ~903 Watt array for 10% rate of charge with a 1,200 Watt minimum AC inverter....

So--Without knowing much about where you are located, if you will use genset for winter/bad weather, etc... At this point, I would be suggesting a ~903 Watt minimum array (note, solar math is not that exact.... I am using 903 Watts so you can see where I am pulling the numbers from -- Anything within ~10% is pretty much "exact" in solar power estimate).

And possibly a larger AC inverter (1,200 Watts minimum)... It is possible that your 1,000 Watt Tripplite will work fine for you--I just do not know.

Also, with a 903 Watt array--You will have lots of extra power for much of the season...

• 903 Watt array * 0.52 off grid AC system eff * 3.75 hours of sun (9 months of the year) = 1,761 Watt*Hours per day
  

That is enough to keep a cabin well lite and the folks entertained (laptop, cell phone, LED TV) and probably a 12 volt RV water pump for plumbing (surface water, or use deep well pump + cistern + genset or a "solar friendly" deep well pump).

Your corrections/questions about my guesstimates?

-Bill

softdown said:

Your batteries may be dead in a couple months if you don't have the panel power. Then you lose what you have in the freezer/fridge. December is coming.....short, cloudy days. Try to put the freezer/fridge in a cold area. I'd add that extra panel asap.