ABSTRACT
Energy from water is one of the oldest sources of energy, as paddle wheels were used to rotate a millstone to grind grain. A large number of watermills, 200-500 W, for grinding grain are still in use in remote mountains and hilly regions in the developing world. ere are an estimated 500,000 in the Himalayas, with around 200,000 in India [1,2]. Of the 25,000-30,000 watermills in Nepal, 2,767 mills were upgraded between 2003 and 2007 [3]. Paddle wheels and buckets powered by moving water were and are still used in some parts of the world for liµing water for irrigation. Water provided mechanical power for the textile and industrial mills of the 1800s as small dams were built, and mill buildings are found along the edges of rivers throughout the United States and Europe. en, starting in the late 1800s, water stored behind dams was used for the generation of electricity. For example, in Switzerland in the 1920s there were nearly 7000 small-scale hydropower plants.
