The silicon cells manufactured from one ton of sand can produce as much electricity as burning 500,000 tons of coal. Silicon is the second most abundant element on earth. It is sensitive to light. When it is treated with certain impurities, it generates substantial voltage. Photovoltaic modules are arrays of solar cells that generate voltage when sunlight falls on them. But it takes a lot of electricity to manufacture these devices. An energy break even point may take one to three years to achieve. Also, issues of manufacturer-worker safety and semiconductor recycling, have to be addressed. The silicon in your computers and the silicon in your PV modules is the same. The life of PV modules is expected to be about 25 years.