Hydroelectric systems use the energy of flowing water to generate electricity. Systems range widely in size from pico run-of-stream to large scale dams.

Requires: Suitable stream or river, planning permission, environmental licence(s).

Works well with: Battery Storage, Heat Pumps (particularly those with a Thermal Store).

Hydroelectric systems convert energy from flowing water into electricity. The main advantage of hydroelectric systems over variable renewables such as solar and wind generation is that with enough flow these systems can run continuously, day and night in all weathers. Hydroelectric systems generate most over the winter months when demand for heating and lighting is highest. Comparatively, this consistency greatly reduces the need for investment in Battery Storage, although it may still be desired.

There are different kinds of hydroelectric systems. System selection will mainly depend on the size and gradient of the waterway. Generally, more water and steeper gradients yield more energy. Run-of-stream or river systems mean no reservoir is created, only small weirs with minimal environmental and visual impact. These divert water down a drop in gradient to a turbine then back into the stream or river at a lower point. These systems usually last over 25 years with minimal maintenance. (2,3)

Pico and micro hydroelectric systems generate 0-5 and 5-100kW of installed capacity respectively and are typically run-of-stream.23 Small run-of-river hydroelectric systems generate 100-5,000kW of installed capacity. Small-scale hydroelectricity is one of the cheapest forms of renewable electricity per unit.24 Larger scale hydroelectric systems (over 5,000kW, 5MW) can be run-of-river, water wheels, dams, reservoirs, or pumped storage. Larger systems often last over 40 years. (4)

Potential damage from debris at times of flooding should be minimised by screening the system intake. (1)

Hydroelectric installation costs vary widely depending on the type, size, and location of the system, but operational costs are comparatively low as hydroelectric systems are very reliable.

(1) Energy Saving Trust, Generating Renewable Energy, Hydro. Available from: https://energysavingtrust.org.uk/advice/hydroelectricity/ [Accessed 26^th January 2021]

(2) British Hydropower Association, Micro and Pico Hydro. Available from: http://www.british-hydro.org/micro-hydro/ [Accessed 26^th January 2021]

(3) British Hydropower Association, Small Run of River. Available from: http://www.british-hydro.org/small-run-of-river/ [Accessed 26^th January 2021]

(4) British Hydropower Association, Types of Hydro Generation. Available from: http://www.british-hydro.org/types-of-hydro/ [Accessed 26^th January 2021]