sceptics say that solar panels, devices made mainly of silicon which convert sunlight into electricity,are always being heralded as the coming thing, but they never actually become economical. shell International Petroleum,however, predicts that by the year 2050 renewable power, particularly solar,will play a larger role in world energy production than non-renewable sources. Strikingly, the cost of electricity from solar panels has fallen from around 500 dollars per watt in the 1960s to under four dollars in the late 1990s. Many companies are making large investments to break the two-dollar barrier - the crucial price, as it is the average cost of electricity in California.