Renewables: Hydro Power

Hydro power systems use running water turning a turbine to produce electricity. A micro hydro plant is one that generates less than 100kW. Improvements in small turbine and generator technology mean that micro hydro schemes are an attractive means of producing electricity. Useful power may be produced from even a small stream.

Hydro power requires the source to be relatively close to where the power will be used, or to a suitable grid connection. Hydro systems can be connected to the main electricity grid or as a part of a stand-alone (off-grid) power system. In a grid-connected system, any electricity generated but not used can be sold to electricity companies.

In an off-grid hydro system, electricity can be supplied directly to the devices powered or through a battery bank and inverter set up. A back-up power system may be needed to compensate for seasonal variations in water flow.

The capital cost is high but the prospect of not having electricity bills or making money by selling energy back to a power supplier may tempt you!

Hydro power systems convert potential energy stored in water held at height to kinetic energy (or the energy used in movement) to turn a turbine to produce electricity.

Energy available in a body of water depends on the water's flow rate and the height (or head) that the water falls. These are divided into low head, medium head and high head, where the height drop is greater. The scheme's actual output will depend on how efficiently it converts the power of the water into electrical power (maximum efficiencies of over 90% are possible but for small systems 60 - 80% is more realistic).

If you are interested in installing hydro , typical installation cost for a small scale system is dependant on the head height however £4,000 per kW for low, £2,000 per kW for medium are realistic with a fixed cost of about £10,000, however grants are available from the low carbon buildings programme (funded by the Department of Trade and Industry, DTI). To be eligible for a grant you will need to use a certified installer and products. The low carbon buildings programme offers a maximum of £2,500 or 30% of the relevant eligible costs, whichever is the lower for Hydro systems.