Alternative energy generally refers to non-traditional energy sources and energy storage technologies that have low environmental impact. All energy resources that can replace fossil fuels The term “fungible” is relative to fossil fuels, so alternative energy sources do not come from fossil fuels. Some alternative energy sources are also renewable energy sources, and by definition, alternative energy sources do not have an impact on the environment, but renewable energy does not necessarily have an environmental impact if it does not have such a definition.