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Developed and maintained
by the NFCC



There are three types of hydroelectric schemes:

  • Impoundment, where a dam is built across a river, impounding a head of water behind it in a reservoir, which can then be released through a turbine to generate electricity
  • Diversion (sometimes called run-of-river) facilities that channel a portion of a river through a canal. They may not require the use of a dam and have a lower environmental impact. Given a suitable location, a run-of-river hydroelectric scheme may be a practical and economic project that could provide power for a single residence or community. Recent technological advances in turbine efficiency mean that even locations with relatively small flows can generate electricity efficiently.
  • Pumped storage facilities store energy when the demand for electricity is low, by pumping water from a lower reservoir to an upper reservoir. During periods of high demand for electricity, the water is released back through a turbine to the lower reservoir to generate electricity.

Figure 13: A hydro screw with protective guarding - photograph courtesy of Ian Moore

Hydropower is produced when the kinetic energy of flowing water is converted into electricity by a turbine connected to an electricity generator. Hydropower can be exploited on a wide range of different scales.

  • Large-scale is typically taken to mean more than 10MW of grid-connected generating capacity and is usually associated with a dam and a storage reservoir. There are many large schemes in Scotland, which were built during the 1950s. The potential for identifying new large-scale schemes is now much more limited, not only because there are fewer commercially attractive sites still available but also because of environmental constraints.

Small-scale schemes, of less than 10MW, now offer a greater opportunity for providing a reliable, flexible and cost-competitive power source with low environmental impacts. These schemes are making an increasing contribution towards new renewable energy installations in many regions of the world, especially in rural or remote regions where conventional sources of power are less readily available. Small-scale schemes can be associated with a dam and storage reservoir or can be located in a moving stream which turns a small turbine creating renewable electricity. The amount of energy produced from these systems depends on the flow rate of the river and the volume of water in the river.

Hazards (for further information refer to National Operational Guidance: Utilities and fuel)

  • Working on or near water
  • Whenever a turbine is moving it is generating electricity, and cables from the turbine to the inverter will remain live
  • Working at height

References and further reading