Types of hydropower
Hydropower is power derived from the force of moving water. It is widely used to produce electricity, among other useful purposes.
Hydropower is a versatile, flexible technology that at its smallest can power a single home, and at its largest can supply industry and the public with renewable electricity on a national and even regional scale. In terms of generation capacity, hydro accounts for eight of the world’s ten biggest power stations.
There are four broad hydropower typologies:
- Run-of-river hydropower: a facility that channels flowing water from a river through a canal or penstock to spin a turbine. Typically a run-of-river project will have little or no storage facility. Run-of-river provides a continuous supply of electricity (base load), with some flexibility of operation for daily fluctuations in demand through water flow that is regulated by the facility.
- Storage hydropower: typically a large system that uses a dam to store water in a reservoir. Electricity is produced by releasing water from the reservoir through a turbine, which activates a generator. Storage hydropower provides base load as well as the ability to be shut down and started up at short notice according the demands of the system (peak load). It can offer enough storage capacity to operate independently of the hydrological inflow for many weeks or even months.
- Pumped-storage hydropower (see illustration above): provides peak-load supply, harnessing water which is cycled between a lower and upper reservoir by pumps which use surplus energy from the system at times of low demand. When electricity demand is high, water is released back to the lower reservoir through turbines to produce electricity.
- Offshore hydropower: a less established but growing group of technologies that use tidal currents or the power of waves to generate electricity from seawater
These technologies can often overlap. For example, storage projects can often involve an element of pumping to supplement the water that flows into the reservoir naturally, and run-of-river projects may provide some storage capability.