As cleantech develops as an industry, so do cleantech related patents. The Cleantech Group at Heslin Rothenberg Farley & Mesiti P.C, publishes a quarterly growth index 

of patents in the field of clean energy. Patents in the field are primarily related to fuel cells and secondarily to wind, sold and hybrid electrical energy in a similar weight, the former are the only field characterized by a continuous growth in patent numbers. Overall the study  includes over 200 US patents per quarter which is quite small. It is important to keep in mind that the current state of the cleantech field may better mirrored by the numbers of patent applications, however these are not published till 18 months after filing, and prosecution may take at least a time period that is similar in duration. The index thus reflects the situation in the industry 3-4 years ago. The role of regulation on the cleantech industry is discussed in this context by Alexis Madrigal at Earth2Tech.

 Another source analyzing biofuels in more details is the forum of the CleanTech Group LLC. For example, Ronald Kamis and Mandar Joshi have published a counting of patents in the field , dominated quite expectedly by patents relating to biodiesel in the US, which will be interesting to follow.

 Finally, to look at this theme from a different angle related to another buzzword, the nanotechwire reports that nanotech’s impact on cleantech is growing rapidly as reflected by an increase in cleantech patents that are enabled by nanotechnology, most of them related to the energy field.