admin answers:

Far more than you can afford.

A 3 ton central air conditioner draws about 7,500 watts. The sun doesn’t shine all the time, indeed you typically get less than 8 hours of usable sunshine for photovoltaics so you have to generate three times the power that you need in order to run the air conditioner around the clock so that’s 22,500 watts. Inverters are inefficient and are more inefficient the bigger they get to the point where motor generators are used with large sale DC to AC conversion, however most solar systems use an inverter so you’ll likely to have 60% efficiency therefore it’s 37,500 watts that’s needed. Air conditioners are ideally sized to meet the cooling demands as closely as possible as a short duty cycle results in high humidity so let’s say it has an 80% duty cycle, that brings the requirements to 30,000 watts. A solar cell costs $1.20 a watt to manufacture in China and $2 a watt to manufacture in the US but by the time a system is installed, it would likely be $5 per watt so your solar panels would cost $150,000. Oh, and you won’t have enough roof space facing the Sun.

If you do want solar powered air conditioning, your best bet would be evacuated tube solar thermal panels running an absorption air conditioner. But this won’t be cheap either and it will probably still require natural gas as a backup source of heat and it would mean completely replacing your air-conditioner.

admin answers:

A solar electric system consist of in simplest terms a panel, charge controller, battery, and a load “lights, radio, etc”. This system can be expanded on.
The first item you need to consider is the loads, what do you want them to be. How much energy do they consume per hour and how many hours a day are they used. The next is the voltage of the items 12volt dc, 24 volts dc, 120 volts ac. In general 120 volt ac itmes are easier to obtain but in general less effeciant but also have longer life spans then the 12 and 24 volt dc versions.
Example we use 1 light bulb that consumes 20 watts at 12 volt for 4 hours a day. This buld would need 20*4=80 watts of energy per day. Next lets say you had 5 of these light bulbs and they were all used the same amount every day, you would need 80*5=400 watts to run these lights. Next lets say you want 2 days of reserve enegy incase it rains or something 400 *2=800 watts.
These 2 figures help give us the panel and battery size. Lets look at the panels first. We determind we needed 400 watts per day. Look around on the interent and you will find a chart with hours a day of sun light for your area. Lets say your area get 2.5 hours of direct sun per day in the worst time of year you would need 400/2.5=160 watts of panels.
The next figure is the 800 watts of battery. You never want to discharge your battery more than 40% this will reduce your battery life. So lets do the math again. (800/40)*100=2000
Now lets assume your battery back is 12 volts 2000/12=167 amp hour back.
So your system would consist now of 160 watts of solar panels 167 amp 12 volt battery bank a charge controller mounting system for the panels, box for the batteries, and an small fuse or breaker panel to protect all the equipment.
This would be a very simple system but if you wanted to add tv’s radios computer etc. You need to do the load calcs on them add them all together and do the math. Don’t just go out and buy a system someone off the internet sales you it may not be right for what you need.
Something else you will need to see the sun most of the day no shading of the panels. Good luck solar is great.