An anonymous reader writes: Today Steven Chu, U.S. Secretary of Energy, released a letter indicating that he won't continue to hold the job for President Obama's second term. He'll continue until the ARPA-E Summit at the end of February, and then perhaps a bit longer until a replacement is found. MIT's Technology Review sum up his contributions thus: 'Under his leadership, the U.S. Department of Energy has changed the way it does energy research and development. He leaves behind new research organizations that are intently focused on solving specific energy problems, particularly the Advanced Research Projects Agency for Energy as well as several Innovation Hubs. The latter were modeled closely on Chu’s experience working at the legendary Bell labs, where researchers solving basic problems rubbed shoulders with engineers who knew how to build things. At one Innovation Hub, for example, researchers who are inventing new materials that can absorb sunlight or split water are working together with engineers who are building prototypes that could use those materials to generate fuel from sunlight. Chu also brought an intense focus on addressing climate change through technical innovation, speaking clearly and optimistically about the potential for breakthroughs to change what’s possible.'