Friday, February 17, 2012
The brick and morter of solar panels
Solar industry is growing at an accelerated rate as the world is facing an uncertain oil future and nuclear disaster. The cost of solar panels is steadily decreasing, but still it is beyond the reach of millions of people. Why the cost is so high and what can be done about it? In fact, the basic raw material for solar panel is nothing, but beach sand in the form of silicon dioxide. But the cost of sand increases from next to nothing to $ 1300 per kg, as it transforms into electronic grade polysilicon wafer. There are number of steps involved to convert raw sand into electronic grade silicon ingot that includes energy intensive processes and high technology inputs. The raw sand is often contaminated with various impurities, thus displaying different colours.The best quality sand with least impurities are further melted in arc furnace at 2000 C to get 95-98% pure silicon, called metallurgical grade silicon, with an estimated cost at $2 per kg.The metallurgical sand is further treated with Hydrochloric acid in a fluidized bed reactor and distilled to get Trichlorosilane. High purity silicon is made from Trichlorosilane (TCS) by chemical vapor deposition (CVD). The trichlorosilane is reduced with hydrogen gas forming pure grade Silicone crystal. The process involves high temperature reaction and toxic doping gases. The resulting electronic grade polysilicon costs almost $80 per kg at this stage. This is grown into single silicon crystal and drawn into an ingot. The highly pure silicon crystal ingot costs about$ 400 per kg .The silicon ingot is sliced into thin wafer using diamond saw. This process of wafering and polishing is expensive and the resulting silicon wafer costs as much as $1300 per kg.The thinly cut silicon wafer is doped with Phosphorus, coated on the heated surface of the wafer so that it diffuses into wafer uniformly. The doped wafer can generate electricity on exposure to sunlight. These wafers are cut into various sizes, polished and arranged on a back panel to form a solar panel. Conductive copper strips are fixed on the surface of the cells facing the sunlight. Finally a layer of glass is glued on top of the solar cells as a protective layer. The completed crystalline solar panel is ready for installation. The cost of solar panel varies from $2.5 up to $ 7.00 per watt, depending upon the make and construction. Some companies are already selling solar panels at the rate of $1 per watt, making it affordable. As the technology improves, the cost of solar panels is likely to come down further, making it competitive with conventional power sources. The cost benefit analysis will certainly favor solar energy in the future, as we are counting the cost of the damages done, by unprecedented weather conditions in many parts of the world, attributed to global warming. The cost of solar power is estimated at $0.25 per kwhr without any Government subsidy, based on solar panel cost at $ 5.00per watt. But this cost may come down to $0.06 per kwhrs, as the cost of $1.00 per watt solar panel, is made available in the market. In fact many individuals claim to assemble solar panels on their own at a cost much cheaper than market prices. The solar power cost will be certainly comparable to conventional power sources in the future. Those who don’t join the race now will be left behind with costly power bills.