sentence: Hydroelectricity is very powerful, safe and produces no waste.
sentences_before: The way the electricity is produced does not harm the environment as much as fossil fuels like oil or coal.
sentences_after: Hydroelectricity can be made very quickly. This makes it useful for times when demand for electricity is high. Also hydroelectricity can not run out as long as there is a good water supply. Once the dam is built the electricity is free, no waste or pollution produced and electricity can be generated constantly.
concept_name: hydroelectricity
headings: Hydroelectricity Advantages of hydroelectricity
categories: Technology Hydropower