Solar energy is the sun's energy that is harnessed and can be used as an alternative to fossil fuels. The sun's energy comes from nuclear fusion reactions, with a small amount of mass converted to a large amount of energy. Only a tiny fraction of the sun's energy reaches Earth, mostly as infrared and visible light. This solar energy can be converted into thermal or electrical energy through the use of solar panels and collectors. While solar energy is clean and free, its intermittent nature and high costs have limited its widespread adoption. New technologies aim to improve solar energy storage to increase its viability as a renewable alternative energy source.

1. Ch 17 Alternative Energy Sources 17.1 Solar Energy