Easy DIY Solar Lighting
(Page 4 of 5)
April/May 2007
By Charles Higginson
Notes on Assembly
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We built this system as a portable demonstration setup, creating some complications you wouldn’t encounter in a permanent domestic installation. Even so, it took one person only about seven hours to put it together, including a trip to the hardware store.
The kit went together easily, using just three screwdrivers, a wire stripper, an adjustable wrench, and a hand drill with two bits. Mount your devices with sufficient room between them for convenient routing. Wiring could hardly be easier — cut wires to length, strip the tips, twist the strands together tightly and screw them into the proper terminals. The wiring diagram provided by Real Goods was crystal-clear.
It’s critical to maintain polarity — all LEDs, and CFLs made for DC, are unidirectional. We used outdoor extension cord to connect the PV panel, and we were lucky that the conductors in the cord had color-coded insulation. The rest of the wire was inexpensive zip-cord type, which had words embossed along one conductor only. We arbitrarily designated that side as positive. Some wire has a ridge molded along one conductor only, and some speaker wire has clear insulation with conductors of different colors. Just make sure you connect positive to positive and negative to negative throughout.
You don’t have to tin the wire ends with solder, but it’s never a bad idea with stranded wire, and it would make some connections easier to secure. We suggest soldering spade lug terminals onto the tips of the two battery cables, to allow more reliable connections and easier disconnects.
It was distinctly odd to run circuits with no provision for grounding, but that’s part of the simplicity of this setup. In general, grounding is optional for PV systems under 50 volts, but it’s a good idea on larger systems and essential anywhere lightning protection is needed.
Two things surprised us the first time we flipped the switches. We expected at least one poor connection, but lo and behold, the lights came right on. And we did not expect them to be as bright as they are — even the LED puts out a nice, bluish gleam. No question about it, this is a genuinely useful solar lighting system.
Ways to Save on a Solar Light Setup
We purchased our components new at retail for about $760, and some were oversized for the immediate need. With a bit of time and energy, you could build a similar system for less money. (Real Goods is offering the kit for $699.)
The PV panel is the most expensive item in the system. There’s a market for used solar panels, which could provide distinct savings. A solar panel that hasn’t been damaged should operate for 25 years without significant degradation, so a panel just a few years old should work for quite a while. Norman Franks of Real Goods says you generally can’t get a warranty on a used panel, but PV is so reliable that the savings are worth the risk.
Batteries also are expensive, and also can be found used, but their life expectancy is considerably less. A used battery would be a way to get started, but anything more than two years old is likely to fail within a couple of years.
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