Have a look at an article on green energy, using the Deep Green Underwater Kite to use energy of ocean currents. Further informatgion can be obtained directly from the website of the enterprise Minesto, www.minesto.com. A video on Minesto Tidal Eergy in avaiilable at YouTube.
A related article on "Top 20 Green Tech Ideas" can be found on time.com. A full list is available here.
Or have a look at some related videao on YouTube, like on video on tidal power or on wave power.