Final answer:
A hydroelectric dam is the least polluting, least costly, and most efficient means of converting the potential energy of water into electrical energy, making it a clean and renewable energy source.
Step-by-step explanation:
A hydroelectric dam is the least polluting, least costly, and most efficient means of converting the potential energy of water into electrical energy. Hydropower, as a source of renewable energy, uses the energy of moving water to spin turbines which in turn generate electricity. The process of generating hydroelectric power involves water being stored behind a dam and containing potential energy. When released, this water converts to kinetic energy, which is then used to turn the blades of turbines, ultimately causing a generator to produce electricity.
This form of energy is considered a clean and renewable source because it harness a natural cycle wherein solar energy lifts water, giving it gravitational potential energy, which hydropower systems capture and convert to electrical energy. Furthermore, it does not directly produce emissions of air pollutants, making it a nonpolluting energy choice. Despite their many benefits, hydroelectric facilities can have environmental impacts, such as obstructing fish migration, although mitigation strategies like fish ladders have been implemented to help alleviate these effects.