Hill: New research released Monday found there has been an explosion in renewable energy patents in the past decade. In the U.S., renewable energy patents surpassed 1,000 annually in 2009. During the period between 1975-2000, in contrast, the number was below 200 per year. Patents, research and development investment, and market growth in coal technologies showed a significant increase in the U.S., with the number of patents increasing to roughly 300 in 2009. The study, released in the journal PLoS...