Steven Chu. Photo courtesy PNNL via FlickrJet-engine wind turbines, fuel made from big batches of algae, enzymes that trap power plant CO2. Sound seriously far-fetched? They may be. But these concepts are fetching serious investment dollars from the Department of Energy. DOE Secretary Steven Chu — a Nobel Prize-winning inventor himself — has launched a new program dubbed “ARPA-E.” It’s modeled after DARPA (Defense Advanced Research Projects Agency), the Pentagon’s technology-innovation program that was responsible for the internet, cell phones, GPS, and other technical breakthroughs. ARPA-E is doling out multimillion dollar grants to the nation’s most visionary energy innovators — thrill-seeking, over-achieving uber-geeks from start-up companies and universities across America. To offer a glimpse of what they’re up to — and what America’s energy future might look like — we singled out seven of ARPA-E’s 37 recipients. These guys (yes, they’re all guys) are pursuing high-risk endeavors that may never see commercial applications. But if they do, the rewards could be staggering in scope.