Is Running and Air Conditioner possible with solar power?

System · August 2010

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.

solar_dave · August 2010

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

paleontol99 wrote: »

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).

BB. · August 2010

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

System2 · August 2010

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.

BB. · August 2010

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

Photowhit · August 2010

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

paleontol99 wrote: »

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.

Photowhit · August 2010

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.

Vic · August 2010

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

System2 · August 2010

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.

trkarl · August 2010

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.

BB. · August 2010

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

Looks like:

256 AH * 48 volt bank = 12,288 WH or 12.288 kWH

That is a fair chunk of power!

-Bill

dmiller · August 2010

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

One aspect to consider for longer run times is to use a small inverter generator. My camper is designed to run a 7000 BTU A/C for 3-4 hours. But for longer A/C run times I've ordered a little 1000w Yamaha inverter genset that is converted to propane. When the A/C is cycled off the generator drops down to 47db and produces 300-400w to charge batteries.
If I wanted to further automate the system I could use a gas valve solenoid to cut off the generator at a preset time (say 3.a.m.) An electric start propane generator would be more easily automated but those are bigger and more expensive. I prefer small, lower power and quiet.
Yamaha inverter gensets can be propane converted without warranty problems. They can still be run on gas after conversion.
In an off-grid house rather than buying enough panels to accommodate the darkest winter weather a quiet generator with electric start may be simpler and easier on the batteries. With the right system this could be run automatically (gen start at 12v) or manually. A quiet generator could be run all from 3-9 pm without notice rather than a contractor generator banging away for 2-3 hours. Better for both batteries and people.

Mangas · August 2010

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

Yes it can be done.

I am running off grid two 2.5 ton zone controlled central A/C units (compresors and air handlers).

As said, you have to size the solar system properly to reliably meet your A/C power requirements after taking judicious conservation measures.

This site covers very well the importance of conservation.

We spent three years planning and designing our remote off grid system evaluating technology, land conservation, costs and lifestyle trade offs. Excluding the stand by genny, we built into our system about 35% overcapacity which increases reliablity and reduces our apprehension during the winter months. In my opinion no matter what your set up you'll use the 35%.

Accordingly, our final system configuration decision was not simply a matter of "cost".

kf6gse · September 2013

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

Yes it is not only possible but quite efficient to do so. First of all you need to locate a good SEER20 or better mini split such as the DC25GW and choose the volatge you prefer. I use a DC25GW 24 volt DC 9000 BTU model and power it directly from 4 235 watt solar panels during the day to cool my house in Mexico. It works VERY well. Then if you desire to have it run at night add a charge controller and four 180 AH golf cat batteries and you're in Business. These days one can buy sola rpanels consitently for a buck a watt and the DC25GW 9000 BYU mini split will set you back around 900 bucks. Not a bit deal really. By the way, my house in Southern Baja Mexico has both off grid and grid tied solar systems. My grid tie is to run things like my electric coffee maker and big microwave oven. The off grid systems consist of a 12 volt off grid system, a 24 volt off grid system and a couple PV panels connected directly to a 24 VDC HWH element in a 10 gallon electric hot water heater. All works very well and I've never been without power.

waynefromnscanada · September 2013

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

post removed at request of company--unauthorized marketing company

Unfortunately such things are not "one size fits all". Some areas have more sunlight per day, some higher intensity sun while other areas are way off in the other direction. Additionally, some areas have extremely high heat loads to deal with, others not nearly so much. There tends to be way too many variables site to site to be successful with universal kits.

solar_dave · September 2013

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

post removed at request of company--unauthorized marketing company

The both have a different set of variables. One is a load profile and one is a generation profile. It is better to take a total load profile and fit the generation to match, whether it be on grid or off grid. Of course off grid is much more expensive to implement. Today the cost have come down on solar but it is hardly grid parity without some subsidies.

H2SO4_guy · September 2013

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

I run a 9000 watt Mitsubishi heat pump for both heat and cooling. It is 26 SEER rating, runs on 220 vac, so I use an Outback 220 volt transformer. I can run this off of an Exeltech XP-1100 inverter or the Outback, both work just fine. I tried to do my setup on the cheap so I could afford a bigger system and use more solar panels and used batteries, as the batteries are the weak part of the system. When the temp is up to 96 degrees I can get the living quarters (175 sq ft) to 62 degrees if I like on sun power alone. At night I use a $1300 battery pack that is 2080 AH @ 48 VDC with 6 spare 2 volt cells so as they fail I have replacements that are of the same age and from the same batch. Works great for me, but as Vic says YMMV.

Skip

bill von novak · September 2013

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

H2SO4_guy wrote: »

At night I use a $1300 battery pack that is 2080 AH @ 48 VDC with 6 spare 2 volt cells so as they fail I have replacements that are of the same age and from the same batch.

They're not going to be the same age once the old ones fail. Then you will have a bank of 22 cells with hundreds of cycles on them and 2 cells with no cycles on them. I wouldn't try to do that without active balancing.

H2SO4_guy · September 2013

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

I purchased 54 Panasonic AGM 2 volt cells for $1300 (Not counting lead trade ins) The 6 spare cells are in a 12 volt system which do get cycled occasionally. I'll take my chances with them, they are working just fine. They run everything I need at this time.

gww1 · September 2013

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

I did just use 48 volts worth of scrap batteries to check if my inverter was working. I used it for two days then plugged in a skill saw and pulled the trigger and a battery blew up. wow it was an impreesive explosion. H20, I love what you are doing and am keeping my eye on your progress reports so when I ruin my fork truck battery I will still have options.
Cheers
gww

SolarPowered · September 2013

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

paleontol99 wrote: »

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.

Converting electricity to BTU is 1/3 in proportion. Depends on how long you chose to use your system for. 8 hours of Air conditioner to 8 hours of PV watts means you would need 16.5 kwh of PV.
Geo thermal is really the only way to go. 30 feet under ground constant temperature regulates heating and cooling needs. 5000BTU geo thermal uses 2/3 less electrical energy than conventional coolant/refrigerant based systems.

gulfyankee · September 2013

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

SolarPowered wrote: »

Converting electricity to BTU is 1/3 in proportion. Depends on how long you chose to use your system for. 8 hours of Air conditioner to 8 hours of PV watts means you would need 16.5 kwh of PV.

I beg to differ. I run (2) 6500BTU window units, (5) ceiling fans, our entertainment center, charge phones, tablets, and laptops, and all of the lighting in our house. Our highest production thus far has been 16.5 KWH feeding our 16 GC2 sams club specials. This has been done through a summer of 100+ temperatures in humid southeast TX. Surely a single 5000BTU AC unit could be run with much less.

SolarPowered · September 2013

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

8 hours of air conditioner meaning a "constant" value. That means no thermostat shut off. If the unit was to run constantly with no periodic shut downs for 8 hours it would be the equivalent of 16.5kwh of solar. Reality is once an internal temp has been met the unit shuts off so there is a variable. Works no different than refrigeration, once the temp is maintained the compressor unit works at a fraction of what it should, to its name plate rating. Always calculate for worst case scenario and assume losses along the way.

I have a heat pump in my home. I live in a condo roughly 1100sq/ft. 20 year old Seer 18 heat pump, plus to run our regular equipment comes out to a consumption in our home per day is roughly 7.1 kwh, we have vaulted ceilings that don't account for sq/ft. I would need 24.8kwh of solar 'minimum" if I chose to go off grid. With a fixed system at 18* tilt, un accounted angle of azimuth would suggest I would need an additional 7kwh of solar to compensate for angle, thats not very realistic for realestate with only 1100 sq/ft to compensate for it.

techntrek · September 2013

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

Air-sourced inverter-based A/C (or heat pump) has nearly the same SEER as ground-sourced heat pumps (most of which do not use inverter technology yet), and are much cheaper to install and maintain. I used to be sold on the idea of ground sourced heat pumps, even convinced a friend to build his new house with one. I wouldn't do it now. Room-by-room zoning is another good reason to go with the inverter A/Cs, too. You can leave most of your rooms set at 50 F in the winter, or 85 F in the summer, and then quickly warm or cool them as needed.

I doubt your condo has an 18 SEER heat pump if it is 20 years old. Even up to about 10 years ago the standard was 12-13 SEER.

Mangas · September 2013

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

Don't know if this contributes much to the discussion but after initially running our heat pumps for a year, I had them disconnected. They were using too much power.

Without the heat pumps hooked up, cycling the A/C compressors in summer and propane furnaces in winter, I was able to significantly hold higher battery storage levels, especially through the night.

We have two very efficient variable speed HVAC units.

Photowhit · September 2013

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

SolarPowered wrote: »

8 hours of air conditioner meaning a "constant" value. That means no thermostat shut off. If the unit was to run constantly with no periodic shut downs for 8 hours it would be the equivalent of 16.5kwh of solar.

This is made in reference to "...run a 5000 btu air conditioner..." So basically you are either being ambiguous or your just wrong. I have a 5200 btu A/C and it draws a bit less than 500 watts running, so would use about 4KWhs in an 8 hour period. Even adjusting for the amount of energy if you have to store it would be less than 8KWhs of harvest, and an A/C will often be needed when the sun is shining so less loss in storage.

Is Running and Air Conditioner possible with solar power?

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