House air conditioning on stand alone power

[Aussie]

I want to air condition my home. Have been told I could not do it with solar. I have a 48 volt system 24x 2volt x 1025ah batts. 3.8 kva inverter.
I live in Queensland Australia. I think a split system , inverter air con should be possible. Comments and advice is welcomed
I have 24 x 80 watt and 8 x 200 watt solar panels

 

[John Frum]

You have 12.3 kwh to consume in any way you wish.
How much will your ac draw?
How will you recharge the batteries?

 

[Aussie]

I have not looked at air cons yet because I need to know what I can power.
I have 24 x 80 watt and 8 x 200 watt panels

 

[John Frum]

The other factor on the discharge side is max load.
You will need significant headroom on the inverter to handle the current spike of getting the compressor moving.

 

[Aussie]

I want to cool at least an area 10m x 5m and if possible a bedroom about 4m x 4m
Really don't know what is possible. I have been told it can't be done

 

[John Frum]

looks like you have enough solar to recharge the batteries on a daily basis.

 

[Aussie]

Inverter is rated 10500 surge

 

[Aussie]

My understanding is if I charge at too many ahrs ( my reg shows ahrs in ) I will reduce the life of my batterys I think my batterys can take up to 40 ahrs charge without detrimental effects

 

[John Frum]

My 9000 btu casement AC can handle about 60% of that area in a Toronto summer.
Draws about 750 watts continuos and 3x that to get the compressor going.
Possibly 4x if it has to start hot.

 

[upnorthandpersonal]

You have 12.3 kwh

Correct me if I'm wrong (it's late here), but if OP has 2V 1025Ah batteries (which I assume are Tubular Gel batteries) and he has 24 of those to make a 48V battery, doesn't that make the total capacity 49.2kWh, of which 50% is usable (although you could go lower with these), so 24.6kWh?

 

[John Frum]

My understanding is if I charge at too many ahrs ( my reg shows ahrs in ) I will reduce the life of my batterys I think my batterys can take up to 40 ahrs charge without detrimental effects

You have amp hours and hours confused but yes I see your point.

 

[John Frum]

Correct me if I'm wrong (it's late here), but if OP has 2V 1025Ah batteries (which I assume are Tubular Gel batteries) and he has 24 of those to make a 48V battery, doesn't that make the total capacity 49.2kWh, of which 50% is usable (although you could go lower with these), so 24.6kWh?

My bad.
Its past math oclock and well into happy hour here.
I will leave you in good hands OP.

 

[upnorthandpersonal]

You could do it, but I would put a limit on how low you draw your batteries. In other words, some kind of fail safe that prevents the AC from kicking in if the battery is below x%. This is mostly driven by the amount of time you need to put power back into the battery with the amount of solar power available (and how much of this can be dumped in your battery, based on your current limitations).

 

[Aussie]

Thanks for the reply's. I shall look at some systems and get some actual numbers to work with.

 

[NMNeil]

I built an experimental system for one room, and it can be done.
My system consists of: six 235 watt Canadian solar panels, two cheap Chinese 40 Amp MPPT controllers, eight golf cart batteries wired to 24 volt and a cheap 2.5Kw Chinese pure sine wave inverter.
I'm fortunate that my house in southern New Mexico faces due south and the roof is at the perfect summer/winter compromise angle.
This easily runs my 12K Btu inverter split system, but nothing else as it's a dedicated system and uses the batteries as a buffer rather than storage.
The A/C unit is soft start so no surge current to worry about and the running draw is only about 900 watts. As the sun is going down I turn the A/C to maximum and use the concrete floor as a 'cool' storage. The A/C is turned off when the panels are no longer generating an output, and at night I rely on the stored 'cold'. For the last two years, it's worked just fine and I installed another splt system in my bedroom that will be solar powered in the near future.

 

[upnorthandpersonal]

use the concrete floor as a 'cool' storage.

That's what I use my floor heating for as well in summer: radiant cooling.

 

[John Frum]

That's what I use my floor heating for as well in summer: radiant cooling.

You run cold water through the pex?
Is condensation a problem?

 

[upnorthandpersonal]

You run cold water through the pex?
Is condensation a problem?

Yep, cold water. No issues with condensation.

 

[Aussie]

Thanks NM Neil. Would you tell me the specs of your a/c system. Sounds like I can do it.

 

[tictag]

I want to air condition my home.
I have 24 x 80 watt and 8 x 200 watt solar panels

Are you looking to simply power your A/C during the day? Or do you need all-day cooling?

If the former, you have 3,520W of PV energy available to you during the day (OK, yes, STC, angle to the sun, inverter losses etc etc) ... ballpark. This will power all but the largest A/C units. You'll need a smallish battery to buffer the load but if that's all you need, buy a circa 3,000W A/C and crack on. Your A/C will come on in the morning when the sun comes up and turn off in the evening when the sun goes to bed. Your battery would be cycled 100% DoD every day but that's fine with a good quality LiFePO4 battery - you'll still get many thousands of cycles.

If the latter, then things get a little more complicated, you will need to consider total energy consumption over a 24 hour period, ensure you have battery sufficient battery capacity to meet that consumption and sufficient PV energy every day to replenish it. If you need cooling even when the weather is bad, then you need to increase your storage capacity accordingly.

But first things first, are you just looking to power your A/C during the day?