Monitoring innovation in electrochemical energy storage technologies: A patent-based approach

The spread of intermittent renewable energy sources increasingly shows the lack of appropriate decentralized energy storage solutions for grid support and residential applications. Patents are a good metric to determine whether the necessary technological progress is indeed happening, as the mandatory publication of the underlying invention gives access to otherwise hidden R&D activities. Our paper contributes to the literature with a compiled array of technological classes related to important battery types in the novel Cooperative Patent Classification (CPC), which can be used to identify relevant patent applications of the competing technologies. Using the worldwide patent statistical database (PATSTAT), we find that promising technologies such as sodium-sulfur batteries and regenerative fuel cells (e.g. redox flow batteries) show increasing patent counts during the last years. The number of patent applications for regenerative fuel cells doubled from 2009 to 2011. Nevertheless, the patenting in technologies related to lithium is unchallenged. Annual patent applications in this area have reached very high levels in 2010 and 2011, allowing the conclusion that the introduction of improved modules will continue. Our analysis underlines that electrochemical storage and in particular lithium-based technologies can be expected to play an increasingly important role in future energy systems. Using the presented compilation of CPC groups, adjacent studies could identify the most important patents (for example by citation analysis) in the respective technologies and investigate technological progress in auspicious sub-branches in more detail.