Energy from the Sky chronicles the developments of wind turbines and photovoltaic cells. The narrative stressed the importance of Denmark for wind development and of NASA for photovoltaic development. Illustrated explanations show in detail how present-day forms of each operate. Theoretical limits on their efficiencies are explained, and potential improvements are examined. The narrative elaborates the distinction between variable renewable energy (VRE) from wind and sun and dispatchable renewable energy from hydroelectric and geothermal plants.