Types of hydroelectric schemes
There are three main types of hydroelectric schemes:
Storage schemes
In storage schemes, a dam impounds water in a reservoir that feeds the turbine and generator, which is usually located within the dam itself.
Run-of-river schemes
Run-of-river schemes use the natural flow of a river, where a weir can enhance the continuity of the flow. Both storage and run-of-river schemes can be diversion schemes, where water is channelled from a river, lake or dammed reservoir to a remote powerhouse containing the turbine and generator.
Pumped storage
Pumped storage incorporates two reservoirs. At times of low demand, generally at night, electricity is used to pump water from the lower to the upper basin. This water is then released to create power at a time when demand, and therefore price, is high. Although not strictly a renewable energy (because of its reliance on electricity), pumped storage is very good for improving overall energy efficiency.