The cutting edge of renewable energy is littered with long-established ideas such as the Stirling. From generating power from the wind to harvesting liquid fuel from algae, some of today's most promising new technologies are actually quite old.
Technology often stands on the shoulders of prior discovery. In the energy field in particular, there are precious few killer apps -- ideas that supersede earlier methods. New energy technologies tend to develop slowly and spread at a snail's pace. It takes time and money to accomplish small improvements, and even more of both to spread those improvements across the energy system.
Full story from the Wall Street Journal