Concept
Run-of-the-river hydroelectricity is ideal for streams or rivers with a minimum dry weather flow or those regulated by a much larger dam and reservoir upstream. A dam, smaller than that used for traditional hydro, is required to ensure that there is enough water to enter the penstock pipes that lead to the lower-elevation turbines. Projects with pondage, as opposed to those without pondage, can store water for peak load demand or continuously for base load, especially during wet seasons. In general, projects divert some or most of a river’s flow (up to 95% of mean annual discharge) through a pipe and/or tunnel leading to electricity-generating turbines, then return the water back to the river downstream.
ROR projects are dramatically different in design and appearance from conventional hydroelectric projects. Traditional hydro dams store enormous quantities of water in reservoirs, necessitating the flooding of large tracts of land. In contrast, most run-of-river projects do not require a large impoundment of water, which is a key reason why such projects are often referred to as environmentally friendly, or "green power."
The use of the term "run-of-the-river" for power projects varies around the world and is dependent on different definitions. Some may consider a project ROR if power is produced with no storage while a limited storage is considered by others. Developers may mislabel a project ROR to sooth public image about its environmental or social effects. The Bureau of Indian Standards describes run-of-the-river hydroelectricity as:
A power station utilizing the run of the river flows for generation of power with sufficient pondage for supplying water for meeting diurnal or weekly fluctuations of demand. In such stations, the normal course of the river is not materially altered.
Many of the larger ROR projects have been designed to a scale and generating capacity rivaling some traditional hydro dams. For example, one ROR project currently proposed in British Columbia (BC) Canada—one of the world’s new epicentres of run-of-river development—has been designed to generate 1027 megawatts capacity.
Read more about this topic: Run-of-the-river Hydroelectricity
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