How much solar power do I need?

Question

I'm going to build a little underground house that has very low energy needs. It will have four lights, a small fridge, a tiny ac unit that will probably never get used, and I will run my computer and tv for three to four hours a day and maybe a record player. The heat will be wood and the water will be manually pumped.

Answer 1

The computer and TV will be the big energy drainers when they're on.  Maybe you would use a computer with a tuner card in our computer as your TV, to save space?  A flat panel display uses a lot of power because of its backlight.  If you get a modest laptop, it might use 50 watts.  You can get a computer that uses 7 watts, or even 1 watt, but that type will be very limited (uses flash instead of a hard drive).  I'd allocate 1 kWh a day for the computer/TV.

If you have money, you can buy a SunFrost refrigerator, and use maybe half a kWh a day.

Again, if you have money, you can invest in LED lighting.  Something like

http://www.ledwholesalers.com/store/inde...

uses 3 watts, and provides enough light to read by.  4 of those, 12 watts - maybe 0.1 kWh a day.

400 to 500 watts of panel should cover you for that kind of situation, just to pull a wild number out of the air.  If you have a list of your appliances, try asking the question on the Northern Arizona Wind and Sun forum, where more experts are in attendance.

Note that if you use a cheap, crappy old refrigerator, you could easily use 30 times as much electricity per day.  I was surprised that one of those little 4-foot high dorm refrigerators uses almost as much electricity as a full size.  Because of poor insulation, it can run all the time.

Answer 2

Add up the wattage of all the appliances, divide by whatever solar cell voltages you plan to use to charge your batteries. If you plan to charge 12 volt batteries and use an inverter to create 120 VAC, you should manufacture about 25 to 50 percent more energy from your solar system than you calculate.

600 watts. Divided by 12 Volts = 50 amperes. You may need more like 75 amps to run an inverter to get 120 VAC for all the stuff. Several batteries would be needed to deliver 50 amps for an evening, or however long you plan to run your system, and lots of solar cells. A large panel produces about 2.5 Amps in bright sunlight (about 6 square feet of a quality solar panel) so you'd need 20 times that much, or 120 square feet of solar panels at least. Do you have that much room?

Figure the weight of supports etc. for your solar panels.

And you'll need a pretty good budget for that kind of solar panel array.

My suggestion? Go on regular power, and use a much smaller solar system to provide auxilliary power, or to run a few 12 volt lights (get them at RV store). You can also buy a 12 volt refrigerator (again, the RV store). Then you can charge the batteries with "shore power" AND use solar cells when it is sunny.

  

Answer 3

idk but why will you want to live underground?