I keep seeing these 15watt solar panels for use with 12 and 18 volt car batteries with inverters. I am trying to figure out using my high school physics knowledge(which I took 13 years ago) how many panels I might need to run an Air conditioner that would normally run off a 20 amp circuit. Anyone with knowledge want to chime in and help me out?
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Thinking of an Electronics Project, Solar
- Thread starter Smash05
- Start date
Gollnick
Musical Director
- Joined
- Mar 22, 1999
- Messages
- 29,258
To run an air conditioner, you have four issues.
The first is power. This one is pretty easy. The panels produce 15 Watts. A typical small window air conditioner consumes about 900 Watts. So, 900 / 15 = 60. You will need 60 panels... but don't click "Add To Cart" just yet.
There is also the voltage problem. The panels product 12-18 Volts. The air conditioner requires 120. So, there will need to be some conversion there.
But, don't answer yet because there is problem #3: The air conditioner requires AC current and the panels deliver DC current. There will need to be some conversion here too.
But don't answer because the panels produce 12-18V. That's +/- 20%. The air conditioner wants much tighter control, so you'll need some regulation there as well.
Conversion and regulation always come with inefficiency. 15% is a reasonable guess on how much power you will loose getting from 12-18 VDC to 120 VAC.
So, you actually need 900 Watts + 15% more = 1035 Watts. 1035 / 15 = 69 panels. I'd use at least 70 if not 75 to allow a little extra.
Now, go ahead and order those panels.
The first is power. This one is pretty easy. The panels produce 15 Watts. A typical small window air conditioner consumes about 900 Watts. So, 900 / 15 = 60. You will need 60 panels... but don't click "Add To Cart" just yet.
There is also the voltage problem. The panels product 12-18 Volts. The air conditioner requires 120. So, there will need to be some conversion there.
But, don't answer yet because there is problem #3: The air conditioner requires AC current and the panels deliver DC current. There will need to be some conversion here too.
But don't answer because the panels produce 12-18V. That's +/- 20%. The air conditioner wants much tighter control, so you'll need some regulation there as well.
Conversion and regulation always come with inefficiency. 15% is a reasonable guess on how much power you will loose getting from 12-18 VDC to 120 VAC.
So, you actually need 900 Watts + 15% more = 1035 Watts. 1035 / 15 = 69 panels. I'd use at least 70 if not 75 to allow a little extra.
Now, go ahead and order those panels.
- Joined
- Feb 3, 2001
- Messages
- 32,359
Was that the sound of someones bubble burstin' I heard?
Nope, no bubble burst. Thats why I asked. I figured it wasn't simple. Yeah the more I thought about it, the more it didn't make sense in my head. Even if you ran the inverter included with the regulator I figured it would run down the battery MUCH faster than the panels could recharge. My gut was telling me even one appliance would use quite a bit of power, even if it was small. Appreciate the help.
Ed Ricketts
Gold Member
- Joined
- Oct 7, 1998
- Messages
- 1,341
I'm no expert, but AC and (electrical) heat use a huge amount of power.
- Joined
- Jun 10, 2003
- Messages
- 15,288
www.mcmaster.com has a portable heater ,12 v, for vehicles etc.
Actually I may still do this, but use it to offset some of my lesser electronics, such as my laptop, Iphone, Ipod, etc. Figuring those draw less power, sit for long periods of time, etc. Basically from what I have learned here and other places, i would need to run two 400watt portable wind turbines at max output to run a major appliance. Really these cells are designed to charge car and boat style batteries and run the kind of devices you might run off of a 400 or 1000 watt inverter(such as you might have hooked up to a rv or car). This is sort of a fun project for me to learn some of the technology and maybe save some money in the meanwhile. All things being equal I would love to own an Off the Grid home someday, but that is financially unlikely so I am just going to play in the solar/alternative energy sandbox for the time being. Thanks again for the help.