Newb - What size do I need to run a......

[SDaniels]

My wife gave me a project that I am losing my mind over. Please help.
Looking to run one 5000 BTU window air conditioner, draw is 550 Watts or 5 amps at 110 VAC. This needs to run 100% of the time on solar/battery system. No generator. Only going to be used for about 50 days in summer months.
What I need to know is minimum watt panel system, controller, inverter, and battery size and count to accomplish this. I will probably oversize everything by 10%+ depending on cost.
My brain is just on overload looking at parts, pieces, kits, numbers, calculators etc...
It will not run consistently day and night, but will need to start and stop to maintain temps. Get what I mean? Am I missing something? Any other info needed?
Project is basically a trailer mounted walk in cooler about 70 sq ft. The AC unit is already oversized, haven't found one smaller.
Thanks in advance.

[Sunking]

Your wife is a smart lady and will love it I promise. You not so much.

550 watts x 24 hours = 13,200 watt hours or 13.2 Kwh/day which works out to $1.50 day to utility.

Here is what you need:

• 48 volt battery = 1375 AH. You are talking a battery that weighs 4000 pounds, cost $10,000, needs spill containment, and a dedicated room to hold them. In 3 to 5 years replace them at higher cost.
• Panel Wattage = 4000 Watts. Another $5000 to $8000
• 80 Amp Mppt Charge Controller. $600
• 1500 to 2000 Watt TSW Inverter. $1000
• Misc hardware like Battery Racking, Panel Racking, Hard Ware, Combines,, Fuses, Wiring, Utility boxes, blah blah blah $4000

About $22,000 not including labor, permits, spill containment and inspections.

The great news you must have a generator with a 100 Amp 48 volt charger, or you will destroy your batteries the first year. That will run you another $5000 plus LPG or diesel fuel tank to run a day or two each month. So in the end $30,000 plus.

Here is the part you will really like. Depending on where you live, that mean ole utility charges you around 11 to 15-cent per Kwh. Now you want to use solar battery and just in battery replacement cost every 5 years you will pay your friendly battery dealer 75-Cents per Kwh and we are not including anything else. You just volunteered for a 1000% electric rate increase and a new part time job with no days off.

More great news. I will be tickled pink to design the system, build it, commission it, and teach you how to operate it. All I need is a $10,000 good faith check to get started. I will even give you a pink feather at no charge so you and your wife can be tickled pink too. Your wife will just love it. You wil need a dedicated room for the batteries, so just throw one of the kids out.

[SDaniels]

OUCH!
Are we seeing the same thing? How are people running a refrigerator? Refrigerators take about 75% or this power or a microwave at 1200 watts or a toaster at 800 watts. Almost seems like I could run an entire house with that system. I was seeing a system about 1000 watts at 12 vdc, controller, inverter and 114 AH batteries. It's the smallest window air conditioner I could find. Thanks, you wanna tell my wife?

[ButchDeal]

Off grid is the problem. Install an on grid system without batteries and you can save money. Try to do the same thing off grid, no so much savings.

[Sunking]

I was seeing a system about 1000 watts at 12 vdc, controller, inverter and 114 AH batteries. It's the smallest window air conditioner I could find. Thanks, you wanna tell my wife?

I have no idea how you figured that. 1000 watts @ 12 volts is 100 Amp, less than 1 hour on a 114 AH battery.

[SDaniels]

Like I said earlier, way too many different calculators and conversions to keep up with, every site was a one stop shop. I didn't think that was right myself when it spit it out.

[SDaniels]

Off grid is the problem. Install an on grid system without batteries and you can save money. Try to do the same thing off grid, no so much savings.

I cannot hook to anything, it is a stand alone trailer not near a power source. I wish to not use fuel, like a generator otherwise I would use a propane unit. It is not about saving money in this case, we need it to be hands off self contained and remote.

[organic farmer]

OUCH!
Are we seeing the same thing? How are people running a refrigerator? Refrigerators take about 75% or this power or a microwave at 1200 watts or a toaster at 800 watts. Almost seems like I could run an entire house with that system. I was seeing a system about 1000 watts at 12 vdc, controller, inverter and 114 AH batteries. It's the smallest window air conditioner I could find. Thanks, you wanna tell my wife?

I have a refrigerator and 3 chest freezers, on timers so they only run during day-light. Of course I have a battery-bank, but my batteries do not power them.

I also have a coffee maker, a microwave, dishwasher, clothes washer, dryer, and lots of power tools [no toaster and no A/C]. All of these things we operate during day-light. No problem

[adoublee]

OUCH!
Are we seeing the same thing?

Some here really love the grid and some earn income from utilities. But you do really have to want it.

[SDaniels]

So let's say I run the unit only in daytime hours on a timer, as the box should stay cold enough overnight.
Would I need a battery bank?
What is the smallest panel array I could get a way with to run an AC unit?
Unit rated to draw 5 Amps at 110 VAC while compressor is running and <1 Amp when idle (fan only).
Would I need one battery to make the inversion to AC?
Almost more baffled now than before...... Sorry for the elementary questions.

Energy star tag says annual cost to run is about $41.00

[Mike90250]

First, is the trailer box a living space for a human, or a cold storage root cellar ? Will the doors be opened a lot, or never ?
Insulate the heck out of it with the 2" thick rigid foam board, and spray foam the seams. Seal it up. Would thermal mass help inside?

550 watts running all 24hrs day =13,200 watt hours say it actually runs 70% of the time = 9,240wh More you insulate,
less heat you have to pump out of the envelope, less power, less $$

The more you can tell us what you need, the more ideas we come up with, other than NO.

Look at a mini-split style air conditioner, with a vari-speed (DC inverter) compressor. Very low surge requirement when starting,
The starting surge on a AC is the huge problem. It takes a large inverter to start it, not so large to keep it running, BUT you can't mix
and match, so you are stuck with a large inverter, idling along, wasting power.

Then there is the reality of only 4 or 5 solar hours in a day, you have to harvest all the power for the next 20 hours in that small time window.
And if you have 1 cloudy day, you have no recharge = no power = no AC = sweat.

Batteries, For 50 days, you could run the snot out of them, beat them hard and expect them to die on day 51. Golf cart batteries should last
for 50 deep cycles. buy a new set each year. $800 + tax + core deposit for 8, 6V 200ah batteries, That's 8,640 watt hours of usable storage.
Divide by a 4 hour charging window, that's a 2,592 watt PV array into a 55A, MPPT charge controller.
Where do you want to mount 12 large PV panels for the array ? Shaded roof structure for the trailer ?
Batteries can go in the shade under the trailer, on the dirt.

Throwing ideas out, to see what sticks

[SDaniels]

First, is the trailer box a living space for a human, or a cold storage root cellar ? Will the doors be opened a lot, or never ?
Insulate the heck out of it with the 2" thick rigid foam board, and spray foam the seams. Seal it up. Would thermal mass help inside?

Not living space, door expected to open maybe 4 times a day, never at night. this is for vegetable storage at a produce stand. I need to hold at about 45 degrees (I know, I need to trick out the unit) It is planned to be about 70 sq ft. Planning on 4 inch solid boards of foam walls sandwiched between rigid panels somewhere around R20 all the way around.

I have actually found self contained solar window air conditioners with battery and aux power built into them. But they are pricey, like 5k pricey vs. a $119 for the window unit. I'll spend the rest on fun parts, I am looking for a system that I can revamp / tweak when I need to, replace parts not the whole unit.

I am getting closer to using dry ice and wood chips. I was really hoping to do this the responsible way, but propane or a gas genny are looking more and more of an option.

Still in shock that I could spend $30000+ power my entire home 100% off grid but can not use the smallest air conditioner made during day time only for 6 weeks.

[ButchDeal]

Window AC units are not the most efficient and 5,000 BTU is not the smallest.
What you need is a very efficient and low draw A/C unit, that will run continuously but draw little.
The problem that you have is that you have little space to fit all the required modules to power such a cheap A/C unit.

It is unlikely that you could take a grid designed home off grid for $30k, and the $30k worth of solar equipment is not going to fit on the trailer.
The only way to make it work is to use an A/C unit designed for the job, or at least close, like a mini split.

[SunEagle]

Not living space, door expected to open maybe 4 times a day, never at night. this is for vegetable storage at a produce stand. I need to hold at about 45 degrees (I know, I need to trick out the unit) It is planned to be about 70 sq ft. Planning on 4 inch solid boards of foam walls sandwiched between rigid panels somewhere around R20 all the way around.

I have actually found self contained solar window air conditioners with battery and aux power built into them. But they are pricey, like 5k pricey vs. a $119 for the window unit. I'll spend the rest on fun parts, I am looking for a system that I can revamp / tweak when I need to, replace parts not the whole unit.

I am getting closer to using dry ice and wood chips. I was really hoping to do this the responsible way, but propane or a gas genny are looking more and more of an option.

Still in shock that I could spend $30000+ power my entire home 100% off grid but can not use the smallest air conditioner made during day time only for 6 weeks.

For $30k I would expect that home does not use much power 24/7.

Is that the number a sales person gave you for a system or did you run the calculations based on the value of daily watt hours burned to live comfortably?

The numbers that Mike and Sunking came up with is pretty close to what you would spend to run that veggie fridge. Unfortunately an off grid system can cost about $3000/kWh of generation.So for $30k you might get between 10kWh and 12kWh a day. Any one else tells you it will cost less is not using a standard system or will see their batteries last 5 years.

[littleharbor]

[QUOTE=ButchDeal;n341517]Window AC units are not the most efficient and 5,000 BTU is not the smallest.


Mini split units may be more efficient but unfortunately the smallest ones still pull a lot more than the 4.5 amps of a 5000 BTU window mount AC unit. I would love to find a smaller BTU sized AC unit but have never seen one. I am adding a 5000 BTU unit to a single bedroom in the Baja house. I added another 16 amps of panels to my array to help compensate for the ac unit. Being this is a 150 square foot room I could get away with a smaller than 5000 BTU unit if they actually exist.