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I am looking to have solar power at my cabin used over the weekends and is approximately 750SF. The kicker is I bought a 24k btu mini split system before I thought of this. What are my options to achieve off grid power with generator backup? Will send some ideas a little later this evening.
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You can run lights cheap enough, couple hundred bucks, a small panel, 1 battery, charge controller.
To run the 24K BTU, you are going to have to step that up a couple notches and likely be in for over $5KPowerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister -
Would the $5k be all in or without batteries?Comment
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Being a Split System means good efficiency. Not sure what the SEER is but assuming SEER = 16 draws 1.5 Kw. What that means is say at 24 volt battery requires a minimum 450 to 500 AH battery. That is just to handle the load the Ductless AC puts on the battery and has nothing to do with run time. FWIW a 24 volt 500 AH battery could only run it for 4 hours to discharge to 50% at which point you would need to recharge. Just to charge you are looking at 2000 watts of panels with a 80 amp CC.
It means a lo tof generator run time and fuel and $5K is just a down payment bare bones minimum just to turn it on and run a few hours each day. on battery.Last edited by Sunking; 06-18-2018, 08:29 PM.MSEE, PEComment
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I was looking at this battery set up to run the AC/Heat for 6-8 hours a day. Would this be realistic and work?
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For the battery part yes. But what do you plan to charge it with? Requires a minimum 40 amp charge rate (C/10) and recommended is 100 amps (C/4).
To translate that means 40 amps @ 48 volts is 2000 watt solar, and 100 amp is 5000 watts. For a genny is a 7 Kva genny and a 48 volt 100 AMP charger.Last edited by Sunking; 06-18-2018, 08:36 PM.MSEE, PEComment
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What wattage panels would you recommend?Comment
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Is this what you would reccomend? Any options that should be adjusted up or could save money? How long could a system like this run the AC for continuously?
link to mini split
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Can't tell. You have to factor in the thermostat setting, insulation present, doors open. All sorts of stuff. Running an AC, even mini-split, is going to be expensive.Is this what you would reccomend? Any options that should be adjusted up or could save money? How long could a system like this run the AC for continuously?
link to mini split
https://www.homedepot.com/p/MRCOOL-D...230A/207085061
For weekend use, I'd really suggest using a generator for a couple weekends, use a Kill-a-watt meter to see what your daily load is, and then you can engineer a system
The issue is :
1) plan too small, and you kill batteries and are unhappy
2) overbuild enough to "Be Sure" and you spend a lot of excess money.
Because AC is such a "heavy load" you have to size it just right. Rent a honda eu 3000 and a remote fuel tank, run it 24/7 and measure your loads. If you let the system shut down, the killl-a-watt looses it's memory and resets.Powerfab top of pole PV mount (2) | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-ListerComment
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As many have said here, it's not trivial to power an A/C unit like this from solar.
I considered the same for an RV and although I can do it, in reality the battery capacity is too costly for 24/7 operation.
I found the most reliable way was with a quiet Honda generator, gas and generators are cheap, portable and work on cloudy days..
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gas and generators are cheap,
Clearly you're not in California.
2.2kw Suntech mono, Classic 200, NEW Trace SW4024Comment
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Sell that 24,000btu and buy a 12,000 , even the hot spot unit that works on DC 48v as it is the most efficientComment
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12,000 BTU is too small, and 24,000 BTU is too large for 750/ft2. 18,000 BTU hits the sweat spot. Couple that with as high as an efficiency (SEER) as you can afford gets demand as low as possible. Example a 18K BTU with SEER = 16 demands 1120 watts. At SEER = 20 is 900 watts. In terms of energy makes a significant difference with 12 hours run time in a 24 hour period. At SEER 16 consumes 13.44 Kwh and at SEER 20 is 10.8 Kwh. In terms of battery cost would require a 40 Kwh battery at 16 SEER ($5000) and at 20 SEER requires a 32.4 Kwh $4000 battery. That hurts buying new batteries ever few years.MSEE, PEComment
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