## Solar Power Information

Important Math:
• Watts= (Volts * Amps)
• Amps = (Watts / Volts)
Parts List:
 Part Price Solar Charge controller kit 12vDC, 20A Max/240W@12V - Solar Power Center 12vDC 9A \$55 205@24V 7.71A Solar Panel \$543.25 (\$2.65/Watt) 400W Wind Turbine (+\$578) (\$1.445/Watt) TOTAL \$598.25 (+\$578) 12V 70A (840W) to 110VAC/60Hz Inverter \$1000 TOTAL \$1598.25 (+\$578) OBPS4-VFX3648Q 14.4kw 110/220vac

This provides a simple system, that provides 12vDC output of 183 Amps. Adding additional batteries will increase the runtime in direct proportion to what is added. Insure that you do not overload your system.
 Battery Draw Output Wattage Max Runtime 12V @ 1A 12 Watts 183 Hours 12V @ 2A 24 Watts 91 Hours 12V @ 4A 48 Watts 45 Hours 12V @ 8A 96 Watts 22 Hours 12V @ 16A 192 Watts 11 Hours 12V @ 32A 384 Watts 5 Hours 12V @ 183A 2196 Watts 1 Hour

Estimated Loss of 1.25-1.5 will reduce your runtime through normal battery loss, as well as loss from an inverter. This reduces 12V@32A (384W) to 12V@25A (307W) or 12V@21A (252W) when figuring your battery capacity.

Excerpt from: HowStuffWorks.com:

A car's battery has a reserve capacity rating. A typical rating is 80 minutes, which means the battery can supply 25 amps at 12 volts for 80 minutes. If you consume 120 watts continuously, that means that you are draining about 10 amps from your car's battery continuously. A typical car battery can supply power at that level for perhaps three hours. A deep-cycle battery can supply power at that level for six or eight hours. Then you will need to recharge the battery (which takes awhile). However, if you are running two compact fluorescent bulbs at 15 watts each, total consumption is only 30 watts, or 2.5 amps at 12 volts. A car battery can supply power for about 12 hours at that level. A deep-cycle battery can supply power for a day or two at that level.

While technically you can use a car battery for these purposes, clearly a deep cycle battery will provide the performance you desire.

It is important to keep in mind that your battery charge time will be extensive. In the case listed above, of a 75W panel @ 12vDC assuming you only get 50% output from the cells, and you get 8 hours of sunlight a day (accounting for dimmer conditions at night), your estimated charge time is calculated as follows:

(12v*3amps) / 1.25(loss) = 28Wh => 28Wh*8h = 224Wh/day
That puts the charge time at aprox 1.2 days (or 10 hours)
Excerpt from SCC3 information page:

It is advisable to match the solar panel's maximum current to the battery's amp-hour rating (C), a typical battery charging current is C/20, so a 100 amp hour battery should have a solar panel rating of around 5 amps. Consult the battery manufacturer's data sheets for the best rating.

## Number of batteries needed

If you use the numbers from the sample load numbers link at the end of the page, you turn out needing 6310W peak and a total of 20950Wh/day. This comes out at 51 Amps peak, and a total of 174 Amp Hours in a day at 120 Volts. To handle these peak loads, it is important to use electrical wiring of the correct gauge to carry the current. 51 Amps @ 120 Volts (or 526 Amps@12vDC) is hazardous. One should not forget that batteries have a limited life span. Any system should be designed such that you can easily replace batteries without disrupting much of your load. You may need to diagnose to determine what batteries have lost their ability to retain a charge. These will be the long term operational costs of any system. Electrocution occurs when a small, specific amount of electrical current flows through the heart for 1 to 3 seconds. 0.006-0.2 Amps (that's 6-200mA milliamps) of current flowing through the heart disrupts the normal coordination of heart muscles. These muscles loose their vital rhythm and begin to fibrilate. Death soon follows. To provide an example of how small an amount of current it takes to kill; a 15 Watt night light draws about 125mA.

That being said, if you're going to draw 526 Amps peak from your 12V batteries to feed your inverter, you will need at least 3 of the 183Amp batteries listed above. If you desired to have a 24 hour reserve of power, consuming 20950Wh, you will need aprox. 10 batteries. To avoid deep discharge, I recommend adding another 25-50%. This will increase your runtime in the most extreme situations. I do understand that this becomes quite expensive as well. 10 batteries @ \$359 = \$3,590. It may be more cost effective in these cases to consider having a gasoline generator to run things, until you bring enough panels and batteries online.

## Ventilation

You also need to provide some ventilation as the batteries charge (consider a low voltage DC fan that runs off the batteries or charge controller.. this will allow it to run only while you are charging). Some information about your ventilation requirements can be found online.

## Inverters

If you are not trying to run your whole house, and want to go for a more home-brew system to make your important electronics stay alive, there are smaller inverters avaiable besides the one listed in my parts list above.. Here is a sample list of some that could be used to provide the necessary AC voltage. You can also build your own. If you are attempting to run a TV, Computer or other sensitive device, you should pay close attention to if the inverter outputs Square Wave or Sine wave. Some electronics do not operate well unless they have a true Sine wave.

Zip Code to Sun Hours/Day - (Very useful to estimate)
Bob's Solar Project - An excellent case of how to use solar shingles
Solar System Sizing Calculator (have your bill handy)