http://www.renewableenergyworld.com/rea/blog/post/2012/08/clean-energy-patents-at-quarterly-high-1stquarter-clean-energy-patent-growthindex?goback=%2Egde_36507_member_149032989

Link to a Clean Energy Patent Growth Index (CEPGI) report on numbers and types of recent clean-tech patents, and companies leading in patent filings.