2 Liter Bottles of Light provide as much light as a 50 watt light globe. The slums of the Philippines are getting an extreme home makeover in the form of two liter bottles in their ceilings. The bott (Bottle Lights Ceiling)
By using standard 2Watt Polycrystalline cells, available on sites like eBay, you'll enable yourself to build a 100 Watt panel for around $125. Some people even opt for chipped, or B-Grade cells, that produce the same amount of power but are defective by the manufacturer's standards (ie chipped corners, etc). With this choice of solar cells a completed 100 Watt panel may cost less than $70.