The promise of free energy is an enticing one -- that's free as in renewable source, not cost. (This is capitalism, after all, someone's got to foot the bill.) Economic gripes aside, research outfits like M.I.T. are getting us one step closer to this cleaner fuel future with the creation of three dimensional photovoltaic cells. The team's findings, recently published in the journal Energy and Environmental Science, demonstrate how these computer-modeled structures, rising upward in an unfolded accordion shape, have bee
