Thursday, April 21, 2011

A Low Cost Solar Lighting System For Micro Homes

   Let's say that you have found that great piece of land with a super location, and the view that goes on forever.  Of course, it is located way out in the boonies, and there isn't any electrical power.  Should you be worried about that?  I would say no, under certain conditions.  I have designed many solar electric power systems in the past forty years, and it only gets expensive if you want to run heavy stuff like washers, dryers, large refrigerators, air conditioners, and other large energy sucking appliances.  By the way, the same engineering works with wind and hydro power, except wind and hydro are less money for a cost per installed watt figure.
   I would like to describe a small lighting system that I researched out the building costs for only this morning. It is a DIY system with no labor included, and should be doable in one full day.  Anyone can assemble and install a system like this with simple hand tools.  Let's assume that you have already wired your micro home for lighting.  The basic power system parts needed are listed below.
1. A Solar electric module at least 50 watts output to charge 12 volt DC Solar Batteries.    Approximately $200.00 on sale.  I saw it this morning on the Internet.  I have no connection with that company.
2. A solar charging regulator.  $30.00  Harbor Freight
3. A Lead Acid 12 volt deep cycle marine type battery as low as $42.00 at Wal Mart
4. A 750 Watt modified sine wave inverter to make 110 volts house current from the 12 volts DC provided by the solar system.  $40.00 Harbor Freight
And be careful as this voltage can kill you just like the current in your home.
5. Light bulbs.  You have two choices that really matter.
   A.  Compact fluorescent bulbs drawing 27 watts and equaling the lighting power, or lumen's of a 100 watt bulb.  You can check the lumen's on the packaging, available in six packs at about $3.50 a bulb.  These are not popular with everyone because of the light color and the mercury content of the bulbs.
   B.  Light emitting diode bulbs that draw only 2.8 watts and equal 40 watts of light.  These bulbs cost about $11.00 each but last 50,000 hours.  The problem is that the light is not great for reading. They get the job done and that's about it.  They do save a lot of watts.
   C.  I have to mention that yes, you could use a regular incandescent 60 or 100 watt bulb but it would discharge your battery pack very rapidly.
   I think you can do the system under $350.00 for lighting and minor charging jobs.
D.  There is one more trick to help you save money.  There is an inexpensive wiring device (J C Whitney) for your car or truck.  It allows you to charge a spare battery while you are driving your vehicle. That battery will cost another $42.00 but is a super backup power source, and you can use your vehicle to charge your solar system on cloudy days if necessary. You can add more solar modules and a larger amperage voltage regulator, and more storage batteries as your budget grows.  
   Now, there is some simple math to remember.  I could make it a lot more complicated but I'm not going to do that.  I'll explain it this way.  If the sun pumps 400 watts a day into your solar storage battery you can only use about 90% of that or (360 watts) a day to light your lights.  So, the lower the wattage on your light bulbs, the longer it will take to run your solar battery down.  If you want to charge a cell phone, or run small radio or TV. There is a watts rating per hour on every appliance label.  For example, if a phone charger puts out 5 volts and 1 amp the formula is 5 volts x 1 Amp = 5 watts, and that 5 watts would be the draw per hour in watts.  You can always look up the basic ohms law on the Internet.
Off grid power systems are not rocket science, and most of them are expanded versions of the one described above.  I have produced a short film below on the subject.
   The system in the video below is a direct current system using a 12 volt light emitting diode bulb.  That means that no inverter to make ac voltage is required. So you can save the $40.00 cost of the small inverter, but without the AC inverter you have no safe way to charge cell phones etc.  If you don't understand, please don't mess with it.  Check with a pro.