Running a small 5,000 BTU 115V Window Air Conditioning Unit

[john95]

Since summer is around the corner I thought I'd work on a solar project to cool me down with sun power just for fun.
I was planing on these components:

4x Trojan T105 6V batteries as a 24V array
2x Mission 320 Watt 24 Volt Monocrystalline
HQST 40A MPPT Solar Charge Controller
Go Power 600 Watts 24V Pure shine inverter
Usage will be only 6 hrs daily.

Do you think that this is doable? Thanks.

[SunEagle]

It might be doable but why would you want to spend $1.50/kWh to run that AC unit instead of just plugging it into the grid?

[littleharbor]

And that size inverter might have difficulty starting the compressor for that AC unit.

[john95]

Sorry, forgot to say, no grid there. It's a cabin in the middle of nowhere.

[john95]

And that size inverter might have difficulty starting the compressor for that AC unit.

It is a very small unit, I guess it may be about 800watts max, but I'll check when I get home. If it is 1,500 watts max then I'll have to get a bigger inverter, perhaps a 1,500 watts inverter to match it.

[SunEagle]

Sorry, forgot to say, no grid there. It's a cabin in the middle of nowhere.

Ok. You have no grid available. I agree with littleharbor that the inverter may be not big enough to start the AC unit.

The next issue may be exactly how many Watt Hours will that AC unit use in 6 hours?

Based on that battery bank it will safely provide about 1350watt hours which is about 25% discharge of that 24v 225Ah system. That means the AC unit can only use about 200watts each of those 6 hours. If it needs more then your battery system is not big enough.

Otherwise 640watts of panel, an MPPT 40A CC and a 225Ah battery is a nice balanced system. Just be aware that some inverters have high losses and will consume Ah out of the battery even if the AC unit is not running.

[SunEagle]

It is a very small unit, I guess it may be about 800watts max, but I'll check when I get home. If it is 1,500 watts max then I'll have to get a bigger inverter, perhaps a 1,500 watts inverter to match it.

Again. If that AC unit is rated more than 200Watts you do not have enough battery to run it 6 hours.

[Sunking]

Since summer is around the corner I thought I'd work on a solar project to cool me down with sun power just for fun.
I was planing on these components:

4x Trojan T105 6V batteries as a 24V array
2x Mission 320 Watt 24 Volt Monocrystalline
HQST 40A MPPT Solar Charge Controller
Go Power 600 Watts 24V Pure shine inverter
Usage will be only 6 hrs daily.

Do you think that this is doable? Thanks.

Absolutely doable, Go For It.

Here is exactly what it will take, nothing less. You have a 5000 BTU Window Shaker that requires roughly 500 to 600 watts of power x 6 hours = 3000 to 3600 watt hours per day to run.

Panel Wattage = 1600 Watts. $3200
65 Amp MPT Charge Controller. $500
24 Volt 625 AH battery that weighs 900 pounds and cost $2200 every few years. That would b 8 of those Trojan Batteries.
24 Volt 2000 Watt TSW Inverter. $650
Misc Materials $400
Total Cost Est = $7000

Absolutely doable.

[john95]

Absolutely doable, Go For It.

Here is exactly what it will take, nothing less. You have a 5000 BTU Window Shaker that requires roughly 500 to 600 watts of power x 6 hours = 3000 to 3600 watt hours per day to run.

Panel Wattage = 1600 Watts. $3200
65 Amp MPT Charge Controller. $500
24 Volt 625 AH battery that weighs 900 pounds and cost $2200 every few years. That would b 8 of those Trojan Batteries.
24 Volt 2000 Watt TSW Inverter. $650
Misc Materials $400
Total Cost Est = $7000

Absolutely doable.

Thanks for the components and capacities suggested. I just feel the price of these components is a little bit high.

For the panels alone, to make up the 1,600 watts requirement, I can pick up 5x 320 watts 24 Volts for like $720.
for the the batteries, I can get me 8x used 6 volt 225 Ah for like $200
80 Amp MPT Outback Flexmax for like $500
AIMS Power 2000 watts 24v $600

Total Cost= $2,020.00

Also, I'm thinking on building my own air conditioning unit that would spend no more than 70 watts @12V. 500 watts it is way too much.

[Sunking]

Thanks for the components and capacities suggested. I just feel the price of these components is a little bit high.

For the panels alone, to make up the 1,600 watts requirement, I can pick up 5x 320 watts 24 Volts for like $720.
for the the batteries, I can get me 8x used 6 volt 225 Ah for like $200
80 Amp MPT Outback Flexmax for like $500
AIMS Power 2000 watts 24v $600

Total Cost= $2,020.00

Also, I'm thinking on building my own air conditioning unit that would spend no more than 70 watts @12V. 500 watts it is way too much.

1. Cannot use a Prime number of panels.
2. Used batteries will not last one season, and using Trojan Golf Cart batteries is not the right battery for the application.

[SunEagle]

Thanks for the components and capacities suggested. I just feel the price of these components is a little bit high.

For the panels alone, to make up the 1,600 watts requirement, I can pick up 5x 320 watts 24 Volts for like $720.
for the the batteries, I can get me 8x used 6 volt 225 Ah for like $200
80 Amp MPT Outback Flexmax for like $500
AIMS Power 2000 watts 24v $600

Total Cost= $2,020.00

Also, I'm thinking on building my own air conditioning unit that would spend no more than 70 watts @12V. 500 watts it is way too much.

Great price on the panels but I would be very cautious with the used batteries. Not knowing their true condition may end up costing you a lot more when one or more fail.

[J.P.M.]

Also, I'm thinking on building my own air conditioning unit that would spend no more than 70 watts @12V. 500 watts it is way too much.

How would you go about building your own A/C unit ? Just curious. 70 Watt input might give you ~ 200-300Watts cooling for a reasonably efficient DIY. Any idea what cooling load you're designing for ? Always good to start with a reasonably defined set of design criteria.

[NEOH]

Thanks for the components and capacities suggested. I just feel the price of these components is a little bit high.

For the panels alone, to make up the 1,600 watts requirement, I can pick up 5x 320 watts 24 Volts for like $720.
for the the batteries, I can get me 8x used 6 volt 225 Ah for like $200
80 Amp MPT Outback Flexmax for like $500
AIMS Power 2000 watts 24v $600

Total Cost= $2,020.00

Also, I'm thinking on building my own air conditioning unit that would spend no more than 70 watts @12V. 500 watts it is way too much.

Will the compressor in the Window A/C run 100% of the time?
What if it operates at 50% duty cycle?
I found a GE 5,000BTU that uses 3.6 amps (running)

115 volts x 3.6 amps x 6 hours x 50% duty cycle = 1,242 Watt-Hours consumed per night from batteries
6 hours (sun equiv) x 5 panels x 320 watts = 9,600 watt-hours generated each sunny day
8 batteries x 6 volts x 225 ah x 50% DOD = 5,400 watt-hours usable

How many hours of unobstructed sun does your location get daily?
How many consecutive cloudy days?
How deep do you want to discharge the battery bank? 50% MAX?

The battery bank will easily run the A/C for one night.
And the PV will easily replace the 1,242 Watts-Hours consumed, the next afternoon.

Now, what if you have 4 consecutive days of no sun?
The battery bank will run the A/C for 4 nights with absolutely no solar power input.
It might take two consecutive sunny days to recharge from 50% DOD up to 100% SOC.

Periodically verify all 8 batteries are well balanced in those 4 parallel banks.

[LETitROLL]

Since summer is around the corner I thought I'd work on a solar project to cool me down with sun power just for fun.
I was planing on these components:

4x Trojan T105 6V batteries as a 24V array
2x Mission 320 Watt 24 Volt Monocrystalline
HQST 40A MPPT Solar Charge Controller
Go Power 600 Watts 24V Pure shine inverter
Usage will be only 6 hrs daily.

Do you think that this is doable? Thanks.

A/C is not Cheap, or easy to run from basic solar, Large, expensive, solar setup = no problem. Solar panel prices are coming down tremendously in most locations, i also see brand new 280 to 310w panels in my area for about .50 cents per watt., with that in mind the only way to "cut corners" and play with a fun cool down project for a fair cost is to oversize the panel array (they are cheap now and last a long time), then mostly only run the system during sunny daylight hours, if cloudy it is usually not as hot so you would not need to run system much, and a modest battery bank will allow you to run it for an hour or 2 in the evening after sundown. The batteries in any off grid system are by far the biggest loser (on a grand scale), solar energy by nature comes from the sun, that technology is getting better and cheaper all the time, trying to store the energy and use it later, well that is a giant inefficient process that is not really getting much better, or cheaper, so go with the sun and stay away from the storage in your design and you can do quite a bit without breaking the bank. Most high quality controllers allow current limiting so you can prevent your larger array from hitting your modest battery bank with too much current.

[john95]

Will the compressor in the Window A/C run 100% of the time?
What if it operates at 50% duty cycle?
I found a GE 5,000BTU that uses 3.6 amps (running)

115 volts x 3.6 amps x 6 hours x 50% duty cycle = 1,242 Watt-Hours consumed per night from batteries
6 hours (sun equiv) x 5 panels x 320 watts = 9,600 watt-hours generated each sunny day
8 batteries x 6 volts x 225 ah x 50% DOD = 5,400 watt-hours usable

How many hours of unobstructed sun does your location get daily?
How many consecutive cloudy days?
How deep do you want to discharge the battery bank? 50% MAX?

The battery bank will easily run the A/C for one night.
And the PV will easily replace the 1,242 Watts-Hours consumed, the next afternoon.

Now, what if you have 4 consecutive days of no sun?
The battery bank will run the A/C for 4 nights with absolutely no solar power input.
It might take two consecutive sunny days to recharge from 50% DOD up to 100% SOC.

Periodically verify all 8 batteries are well balanced in those 4 parallel banks.

If the 5,000 BTU A/C unit is run @ 77 F, the unit may work only like 1/4 of its full capacity, so it will cut your calculations to 1/4. @ 77 F there will be no humidity, no sweating, I can sleep very comfortable. Also, there are many things one can do to make the A/C unit to keep the room cool like sealing every hole in the room, install reflective paper on the windows, put some fans in the room to circulate the cool air, etc.

Once the room is cool, the A/C units just has to keep it at that temperature with not much effort.

Check on youtube all the videos where people demonstrate a 5,000 BTU and 6,000 BTU A/C units working fine on a RV or small cabins. Just search for "5,000 BTU air conditioning running on solar". This is the real thing, not meaningless calculations!