A big chunk of our clean-energy pie will be wind and solar. Somewhat smaller slices will be geothermal and nuclear and hydropower. But the last part, maybe the last 10 percent or so, might come down to more niche technologies like hydrogen fuel cells and marine power. The latter represents the cutting edge of clean energy R&D, and it’s primarily happening at the Department of Energy, where the Water Power Technologies Office is seeking to develop, test, and tinker with different devices until they’re commercially viable, at which point private firms will take it away. In general, these devices fit into a few main categories: wave, tidal, river current, and gradients.
