BOSTON--An everyday office building doesn't quite work when you need to hammer out a prototype of a solar-powered chiller or an inflatable wind turbine. So a group of entrepreneurs here have created a hands-on workshop to bring their clean-energy ideas to life. Greentown Labs held its official opening last week, bringing fellow entrepreneurs, city officials including Boston Mayor Tom Menino, and investors looking to plug into the active clean-energy technology scene. About 40 people from 10 fledgling companies have moved into this former baker and confectioner's supply warehouse in South Boston with the hopes of finding more like-minded green-tech start-ups. Among the offerings was beer chilled by solar panels. Their work environment is definitely not class A office space. A disorderly room houses work areas shared among four or five companies. There is separate space for small offices and another with a lab table set aside for electronics testing. In the basement is a large machine shop where inventors can bang out their first prototypes.