Small Solar Power System
In 2005, I installed a small solar power system on our house in Maryland to power two lights on my night stand. When we moved to Utah, I reinstalled it on our new house and it is still working well.
Photovoltaic Panel
I collect solar energy using an 8 watt (0.5 amp) Sun-Mate photovoltaic (PV) panel. I received this PV panel as a gift. It works fine, but you can get more watts for your dollar from panels made by the large PV panel manufacturers. A good 10W-20W panel is about the same price and will charge your batteries faster. See CirKits Links to Alternative Energy Web Sites for links to manufacturers and distributors web sites.
Charge Controller and Battery
The PV panel is wired to a charge controller I bought as a kit from CirKits. The charge controller charges two 12V, 12AH sealed lead-acid batteries (pdf) I bought from American Science & Surplus. The batteries are unused take-outs and cost $9.95. These are a great deal and cost less than half the cost of a new battery (unfortunately they are no longer available).
Lighting
I have two lights that run off this system. One is a normal table lamp with a 15W DC spring lamp (compact fluorescent lamp) that I bought from Real Goods. This lamp puts out the same amount and quality of light as any other 13W-15W compact fluorescent lamp. It nicely lights up the whole room like a normal table lamp. According to my multimeter, this lamp uses about 0.85 amps. I use this lamp for an hour or two every night. If the next day is bright and sunny, the system will get back to a full charge in about three to five hours.
My other light is an Ikea reading lamp I converted from a halogen bulb to 10 white LEDs. This was quite simple to do. I soldered 10 white LEDs (also from American Science & Surplus) and 4 resistors to limit the current to a small Radio Shack circuit board. I soldered two wires to the circuit board which I plugged into the socket holes for the halogen bulb. I also needed to trim the corners off the circuit board so that it would fit into the recess of the reflector area. The lamp's UV glass neatly fits over the LED circuit board leaving a nice finished look. This lamp is great for reading in bed, since it has a directed beam of light that doesn't light up the whole room (and bother other people sleeping there). According to my multimeter, this lamp uses about 0.1 amps. This lamp can be used all night and still not drain the batteries below the point where the PV panel can charge them in one day. This setup worked for a few years, but eventually some of the LEDs failed (I think I was allowing too much current through them - I needed more resistance). I replaced the LED board I had built with a one watt Luxeon LED bulb from Superbrightleds.com. Now days they sell great 12v LED bulbs designed to replace halogen bulbs directly. Most have a built-in buck driver and can run from a wide range of voltages (8-30v).
