Solar energy, radiation from the Sun capable of producing heat, causing chemical reactions, or generating electricity. The total amount of solar energy incident on Earth is vastly in excess of the world’s current and anticipated energy requirements. In the 21st century solar energy is expected to become increasingly attractive as a renewable energy source because of its inexhaustible supply and its nonpolluting character, in stark contrast to the finite fossil fuels coal, petroleum, and natural gas. 

The history of hydropower dates back thousands of years. For example, the Greeks used water wheels to grind wheat into flour more than 2,000 years ago. The evolution of the modern hydropower turbine began in the mid-1700s when a French hydraulic and military engineer, Bernard Forest de BĂ©lidor, wrote Architecture Hydraulique. Many key developments in hydropower technology occurred during the first half of the 19th century, and more recently, the past century has seen a number of hydroelectric advancements.Hydropower technologies generate power by using the elevation difference,  created by a dam or diversion structure, of water flowing in on one side and out, far below, on the other. 

The benefits of hydropower have been recognized and harnessed for thousands of years. In addition to being a clean and cost-effective form of energy, hydropower plants can provide power to the grid immediately, serving as a flexible and reliable form of backup power during major electricity outages or disruptions. Hydropower also produces a number of benefits outside of electricity generation, such as flood control, irrigation support, and water supply.