Business Green: Using a home computer’s spare processing power in the search for extraterrestrial intelligence is old-hat — today’s PC owners are being invited to solve the world’s green energy problems. IBM and Harvard University’s new Clean Energy Project hopes to harvest thousands of internet-connected PCs to speed the development of a cheaper and less energy-intensive material than current solar cells. The aim is to “look for the best molecules possible: organic photovoltaics to provide …