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I am planning to design my design in such a way that I can run my 1.5 ton AC easily during daytime i.e. 9am to 5pm plus some load of around 500 watt. I am planning to use following:

1 - 5000va/4000W 48vdc pure sine wave inverter (power factor 0.8)

2 - solar panels 250 x 12 = 3000 Watt

3 - 4 x 12V 200ah batteries

Will this setup work? theoretically it should.

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    \$\begingroup\$ What is the electrical load of your AC? \$\endgroup\$ – JRE Aug 30 '16 at 12:18
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    \$\begingroup\$ 1.5 ton alternating current? I guess it's some sort of vehicle, but I'm not familiar with that abbreviation. \$\endgroup\$ – Arsenal Aug 30 '16 at 12:35
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    \$\begingroup\$ AC=Air conditioner. \$\endgroup\$ – JRE Aug 30 '16 at 12:38
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    \$\begingroup\$ @JRE thanks for that, now I know that 1 ton is not 1000 kg (that would be a tonne) but 12000 BTU per hour (among other things it could mean). Units are really horrible. \$\endgroup\$ – Arsenal Aug 30 '16 at 12:57
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    \$\begingroup\$ @Arsenal: No argument about the units. They suck. \$\endgroup\$ – JRE Aug 30 '16 at 13:01
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Rather than use an inverter to power the air conditioner, you could take an air conditioner unit that is readily designed to run from DC voltage available from solar power systems.

Many companies are making DC powered air conditioner units, because for the manufacturer, it's a relatively small design change to the unit. Basically all AC units today are 'invergter driven' e.g. they have a frequency changer to drive the motor(s). That already runs from a DC voltage, which is taken from a rectifier stage, and just needs to be tweaked to accept DC input at a suitable voltage.

Here's one such solution from one manufacturer (GE innovations) that I found from Google:

http://www.geinnovations.net/solar_air_conditioner.html

http://www.geinnovations.net/solar_air_conditioner.html

Using a DC powered air conditioner unit eliminates redundant power conversions making it more efficient. It's also much more easier since the air conditioner unit can do decisions such as low voltage cut off much easier than a separate inverter which must work on a very large operating range.

Finally, solar power and cooling is a perfect match because you need the most cooling power exactly when the sun is shining and solar power is available! When it's cloudy and the solar cells generate less power, you also need less cooling!

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1.5 ton of cooling power is equivalent to 5.3 kW cooling. Suppose you have a CoP of 2, then there is 2.7 kW of electrical load. Add the 500 W of other load and you're at 3.2 kW load. AT this load, the solar panels could not produce enough power in full sun to keep this running. Nevermind cloudy days, inverter efficiency, etc. Perhaps you could double the solar setup.

Now you may get a CoP better than 2 - some of the time. It will depend on your weather conditions, etc. If you have a meter, you might take some measurements of the input power at various outdoor air temperatures to be able to better describe the required input power. Also, have you confirmed that 1.5 ton is adequate? Perhaps a smaller unit could meet the cooling needs.

You might use a "automatic transfer switch" to revert to AC mains when you run out of juice. That will make it forgiving of high cooling loads.

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  • \$\begingroup\$ COP of 2 is really, really poor for modern units. Most minisplits I'm seeing in the 5kW range are around 4-4.5. \$\endgroup\$ – Someone Somewhere Dec 29 '17 at 1:56
  • \$\begingroup\$ It's -20°C here. CoP not the best atm. \$\endgroup\$ – scorpdaddy Dec 31 '17 at 19:29
  • \$\begingroup\$ I mean, your cooling COP would be really good at those temps... Reducing COP generally reduces maximum capacity, not input power. It's still going to draw ~1.5kW; it's just going to deliver ~3kW of heat, not 6kW \$\endgroup\$ – Someone Somewhere Dec 31 '17 at 23:13

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