Germany giving up it's nuclear power by 2020?

The question you pose has a political component, the importance of which can't be under-estimated. Here in the U.S., "energy policy" is a creature of Congress and lobbyists from the oil, natural gas, and automotive industries. Environmentalists have a say, too, but it's not in a commanding voice. To succeed, Germany's non-nuclear plans will reqire a major buy-in from the nation's industrial players. Support from the Green Party will never be enough.