text: The sun supplies endless free energy.  People place solar collectors of roofs to collect it and heat water and use banks of photovoltaic cells on their roofs to generate electricity.  In some countries people use reflector ovens to collect solar energy and cook food.  The devices aren't free but the energy is.  Solar energy even warms the earth and oceans and lights the skies, except at night.  The earth is a huge light switch.  I guess that's a free energy device.