The known world has already been through three pivotal epochs: the agricultural, industrial and information-technology revolutions. Now, a fourth is taking place: the renewable-energy revolution.

At least that is how the German director Carl Fechner presents it in his documentary film, "The 4th Revolution — Energy Autonomy," which shows some of the many projects worldwide now generating electricity entirely from natural sources. The film opened in Tokyo on Dec. 17 and will be shown at other cinemas in the capital until Jan. 27. Afterward, further screenings are planned around the country.

Back in October, when 58-year-old Fechner was in Japan for the film's premiere here, at the Goethe Institut Japan in Tokyo, he was all smiles as he told The Japan Times in an interview how "The 4th Revolution" has already been seen by more than 200,000 people in Germany since it was released in March 2010.