Energy transition is one of the fundamental steps needed to fight climate change and to lead towards sustainable technology able to fulfill the energy requirements of the present while preserving the planet. The commitments to limit the increase of temperature on Earth below 1.5°C and to reach net-zero CO2 emissions by 2050 move the energy sector to a renovation, in which renewable energy sources will be pivotal. In order to pursue sustainable paths, the application of the concept of circular economy is fundamental also in the energy sector; efforts to recover critical materials used in RES systems will be important for a life cycle sustainability.