The sun is an inexhaustible source of energy that can be used for a wide range of applications. Passive solar energy for instance is captured when constructional measures use sunlight for heating rooms. solar energy can also be used more actively. Solar panels convert sunlight into electricity. This is called photovoltaic solar (PV) energy, or solar power. Solar heaters convert sunlight into heat in order to warm water and rooms. This is called thermal solar energy.