Alternative energy is any energy source that is an alternative to fossil fuel and nuclear power.
The nature of what constitutes an alternative energy source has changed considerably over time, as have controversies regarding energy use. Because of the variety of energy choices and differing goals of their advocates, defining some energy types as “alternative” is considered very controversial.
Over the years, “alternative energy” has been used to describe solar power and wind, but also “clean coal,” fracking, and more. Therefore Germans use the term “renewable energy” to talk about solar, wind, and hydropower and biomass, the main sources of power for the energy transition.