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Thread: Is Running and Air Conditioner possible with solar power?

  1. #1
    paleontol99 Guest

    Default Is Running and Air Conditioner possible with solar power?

    Hello, I do not know much about solar power. Is is possible to run a 5000 btu air conditioner with solar panels and batteries. Would it take many batteries or alot of solar panels? Is it even possible? I assume there would be drawbacks? Thanks for any help.

  2. #2
    Join Date
    Apr 2010
    Location
    Near Phoenix
    Posts
    1,872

    Default Re: Is Running and Air Conditioner possible with solar power?

    Quote Originally Posted by paleontol99 View Post
    Hello, I do not know much about solar power. Is is possible to run a 5000 btu air conditioner with solar panels and batteries. Would it take many batteries or alot of solar panels? Is it even possible? I assume there would be drawbacks? Thanks for any help.
    If you have net metering is is certainly possible. I have 2 ground mount AC units and a swimming pool in the Phoenix area and my electric bills are around $20 and most of that is fees and taxes. This being said it is not cheap, my utility offered about 50% of the installed cost as a rebate and then the Fed & state tax credits on top of that. My utility lets me roll over any credited kWh early in the year to be used later on my very high summer consumption months.

    At $6 a watt before any of the above compensation and say about a 8,000 watt grid tie setup you are in the realm of $50,000. The key is to use the grid as your battery by running the meter backwards enough to compensate for your non solar hours consumption where those rolled back kWh are then consumed. Conserve as much as possible first by adding insulation, energy efficient appliances and use any other conservation measure first. Then measure your loads and size the system accordingly.

    Battery maintenance and cost drive the costs up greatly, some off grid guys here claim $1 to $2 a kWh. Really the only time a battery system makes sense is if you are far from the utility lines and the cost to get grid power delivered is extremely high. Most would consider my consumption off the charts for a battery system. WOW I just checked and we had a 129 kWh day last week on the hot day. This time of year with the high temps affecting panel output, my system only produces about 65 kWh. Good thing I have 3000 kWh in my utility bank (well I did, it will be interesting to see this month bill).
    My TED 5000 system
    Sticking it to the power company one watt at a time!
    60 Ningbo Electric 175 watt panels and 12 Canadian Solar 180 watt panels with 2 PVP 5200 Inverters

  3. #3
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    19,687

    Default Re: Is Running and Air Conditioner possible with solar power?

    If this is a remote/off-grid application--it is certainly possible and more people seem to be doing it these days...

    First, remember that off-grid solar power is about 10x the cost of grid power--so extreme conservation will really pay off--Lots of insulation, shading of windows, and a very efficient "off-grid" friendly A/C unit.

    The Sanyo Mini-Split has been used by a few people here now and they cannot say enough good things about the unit.

    Sanyo mini split AC (inverter/variable speed)

    Very efficient almost 2x as efficient as a typical window mount A/C unit. With its power control technology, it has very little starting surge (unlike typical A/C systems) and can be set on low speed with a ~300 watt draw.

    Now, that is not to say that you can run these units on a couple of small batteries and solar panels.

    It will take a fairly substantial battery bank and set of solar panels to run the system during the summer.

    What size solar array/battery bank where you thinking of (either in Watts or $$$) to run the A/C?

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  4. #4
    paleontol99 Guest

    Default Re: Is Running and Air Conditioner possible with solar power?

    What size solar array/battery bank where you thinking of (either in Watts or $$$) to run the A/C?


    I had no idea. I was going to build the batter bank to meet the requirements of a half decent air conditioner. I figure the air conditioning is most important to me as it does not seem to take much to run the other things I need to run.

  5. #5
    Join Date
    Mar 2006
    Location
    SF Bay Area (California)
    Posts
    19,687

    Default Re: Is Running and Air Conditioner possible with solar power?

    Lets pick the Sanyo Mini-Split system... and you want to run it on Low for 16 hours per day (300 watts average). This will be an off-grid system (although, if you have grid power, I would really suggest the Grid Tied system as it will cost 1/4 as much as the same thing in Off-Grid--If you want emergency backup power for a grid system--that is another discussion).

    And you live somewhere around Long Beach California... 1kW of solar panels, 0.52 derating, and you want to run the AC 6 months of the year (there is a heat pump version--very neat for cool weather areas with lots of sun).

    Using PV Watts:

    "Station Identification"
    "City:","Long_Beach"
    "State:","California"
    "Lat (deg N):", 33.82
    "Long (deg W):", 118.15
    "Elev (m): ", 17
    "PV System Specifications"
    "DC Rating:"," 1.0 kW"
    "DC to AC Derate Factor:"," 0.520"
    "AC Rating:"," 0.5 kW"
    "Array Type: Fixed Tilt"
    "Array Tilt:"," 33.8"
    "Array Azimuth:","180.0"

    "Energy Specifications"
    "Cost of Electricity:","12.5 cents/kWh"

    "Results"
    "Month", "Solar Radiation (kWh/m^2/day)", "AC Energy (kWh)", "Energy Value ($)"
    1, 4.43, 65, 8.12
    2, 5.00, 67, 8.38
    3, 5.52, 81, 10.12
    4, 6.21, 88, 11.00
    5, 6.12, 88, 11.00
    6, 6.09, 85, 10.62
    7, 6.63, 94, 11.75
    8, 6.79, 96, 12.00
    9, 6.18, 85, 10.62
    10, 5.46, 79, 9.88
    11, 4.81, 68, 8.50
    12, 4.34, 64, 8.00
    "Year", 5.63, 960, 120.00
    So, for March, a 1kW off-grid system would supply around 81 kWH per 1,000 watts of solar panels.

    • 81 kWH per month / 31 days =2.6 kWH per day
    • 300 watts * 16 hours = 4,800 WH per day = 4.8 kWH per day for A/C
    • 4.8kWH of power * 1/2.6 kWH per day per 1,000 watts of panels = 1,846 Watts of solar panels minimum

    Battery Bank wise--A good starting rule of thumb is 3 days of no sun and 50% maximum discharge (for longer battery life). And assume your inverter is 85% efficient. The recommended size battery bank would be (assume 48 volt bank to use a single 60 amp MPPT charge controller--Note a 24 volt battery bank will probably work fine with a single 60 amp MPPT charge controller too):

    • 4,800 Watt*Hours * 1/48 volts bank * 1/0.85 efficiency * 3 days * 1/0.50 max discharge = 705 AH of 48 volt battery bank

    For an Off-Grid system, you are probably looking at ~$20,000-$40,000 for such a system (depending on components you purchase, if you do it yourself or not, etc.).

    We can go deeper into suggesting the major components if you would like.

    If you are Grid Tied--You can probably get a similar amount of power for ~-$7-$9,000 and depending on where you live, a 30% federal tax credit and possible state and/or local rebates too.

    Remember, I am not in the solar business--Just trying to give you very round numbers to figure out what direction you wish to go...

    I have no idea if 300 watts * 16 hours a day is under or overkill for cooling your home. Since solar power is so expensive, getting a good handle on your power needs before you build the solar system is very important so you don't wast your funds on too large or too small of system (which needs an immediate upgrade).

    -Bill
    20x BP 4175B panels (replacement) + Xantrex GT 3.3 inverter for 3kW Grid Tied system + Honda eu2000i Inverter/Generator for emergency backup.

  6. #6

    Default Re: Is Running and Air Conditioner possible with solar power?

    Quote Originally Posted by paleontol99 View Post
    What size solar array/battery bank where you thinking of (either in Watts or $$$) to run the A/C?.
    This will vary wildly depending on your temp settings, the size and insolation of the building and placement on the lot, and local weather.

    I run an AC on solar at my cabin, my plans centered around this when I knew I was going to expland my array...

    I have a well insolated 10x16 cabin with high ceiling, It has @ R28-32 floors (10"), R 20- 22 (6"+ 1"OSB) walls and roof (+1/2 blue board, high pitch). The cabin is in the shade 90% of the day.

    I run a 5300 btu window unit 3-4 hours a night, on energy saver mode, After the first 2 hours the duty cycle is down to 30% on the worst nights. I will sometimes run an extra hour or 2 if it stays above 80 outside.

    That cools it down and allows me to get my sleep over the summer, Often I do run it in the afternoon once I'm at Bulk for an hour or so. Largely a storage problem as I just have 4 golf cart batteries, and will until they expire, going pretty strong for 5 year old batteries, and we had a brutile summer this year in Missouri.

    I did this for 2 years on a 1000 watt array and brought it up to 1300 the last 2 summers. I think 1300 would run this situation around the clock on thermostat with normal summer days, and enough storage.

    Early this year we had the weather I'm use to in north Florida for 3-4 days with high hazzy clouds and high heat and humidity, and I ran the battery bank down to the point the inverter shut down 22 volts, at rest the batteries were at 22.6, I think. Not normal weather here. Lucky I had planed to be gone the next day and a half and reached float in a couple days with just the fridge running.

    I work security, My office/guard shack is 8x12 and lives with out shade, it has r11 in the walls and I'd bet the AC has a duty cycle near 95% and it will not cool below 84 on bad days (lots of comimg and going, 5200 btu)

    Hope this helps.
    Home system- 20 - 200W Evergreen blems, 2 Classic Lites, E-Panel, Prosine 1800 watt inverter, up and running 1 Classic Lite and 14 Suntech 185W in spare room.
    Cabin system- 8-115watt 12V, 6 - 170-5watt 24v, Pulse/Trace PC250 Power Center, 800AH 24V forklift Batt, ProSine 1800 watt (24v) inverter.
    Odds and extras, Rouge CC, 80-4/5watt 6v panels

  7. #7

    Default Re: Is Running and Air Conditioner possible with solar power?

    Forgot to say how much I've adapted just to run the AC, the Kitchen/bathroom is a seperate, un AC'd, building, the only thing that adds heat to the cabin is the fridge, it would run much more in the hot kitchen.
    Home system- 20 - 200W Evergreen blems, 2 Classic Lites, E-Panel, Prosine 1800 watt inverter, up and running 1 Classic Lite and 14 Suntech 185W in spare room.
    Cabin system- 8-115watt 12V, 6 - 170-5watt 24v, Pulse/Trace PC250 Power Center, 800AH 24V forklift Batt, ProSine 1800 watt (24v) inverter.
    Odds and extras, Rouge CC, 80-4/5watt 6v panels

  8. #8
    Join Date
    Jun 2007
    Location
    Center of Nowhere, NOR CAL
    Posts
    1,595

    Default Re: Is Running and Air Conditioner possible with solar power?

    At my off grid site, run two el-cheapo 6000 Btu window A/Cs -- one for the Power Room (this one has #1 priority!), and one for the bedroom. This season, the bedroom A/C has been little used, as we have had a mild Summer (so far), a fan has sufficed.

    Depending on your humidity, a swamp cooler might do fine, altho these can use quite a lot of water, but are more miserly on power. They work well in low humidity environments, as I am sure you know.

    Am close to adding more panels to allow more wreckless use of A/C. Some off gridders try to get a jump on cooling fairly early in the day, as this can (perhaps) reduce the battery capacity required, and so on.

    Vic
    Off-Grid, Sys1: 1280 AH 48 V bat, 3.150 KW STC PV, Classic 150, MX-60, Xantrex Stacked SW+ 5548s; EU6500isa, 21KW Kubota diesel gens, misc Honda Eu gens
    Sys2: 1280 AH 48 V 4KS25 Surrettes, 5.88 KW STC, Two Classic 150s, MN SPDs, Stacked X SW+ 5548s; Kohler 18 KW LP, EU 3000isa gens, HB DC Charger, Midnite Breakers/boxes. Thanks for this great Forum!

  9. #9
    paleontol99 Guest

    Default Re: Is Running and Air Conditioner possible with solar power?

    Thanks so much to everyone for the information. Its fantastic! Im starting to get the idea and be able to put the pieces together on how to do this.

  10. #10
    Join Date
    Jan 2009
    Location
    Cape Coral, FL
    Posts
    33

    Default Re: Is Running and Air Conditioner possible with solar power?

    I ran my central ac which is a Trane 16 seer 2 ton variable speed system one night last July I believe it was from 6pm to 6am set on 76 just to see how far down it would pull the batteries.

    This is sw fla so in the summer it is hot enough. It pulled 256 amp/hrs off the bank which was about a 50% dod on my system. This was confirmed by a sg check.

    So yes it can be done but just size your system accordingly.
    12 BPSX3200 3 x 4 2.4 kw, FM 80, 4 BP590 w/ 2 BP585 1 string 530 w and 6 BPSX175NQ 2 x 3 1050 w, MX 60, SMA 5048U, PSX 240 , Trimetric 2020, 8 Rolls 6cs17ps 48v bank.

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