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Small-scale hydro electricity

Small-scale or micro hydroelectric systems can use the power of a small stream or river to provide more than enough power for most homes.
Small-scale hydro-electricity

What is it?

Hydroelectric power uses moving water to generate electricity. Improvements in small generator technology means 'micro-hydro' is being looked at more seriously. In fact small-scale hydropower is one of the most cost-effective and reliable renewable technologies.

The technology

Using the flow of water around a turbine (water wheel) to generate energy is probably the oldest form of renewable energy. They produce electricity by converting the gravitational energy stored within the water when it is held at height into kinetic (moving) energy. It is this moving energy which causes the turbine to move and generate electricity.

A micro hydro system usually consists of several elements including:

  • A water intake (usually as part of a weir), which diverts the flow of the water source.
  • Trash screens and fish screens (to remove rubbish and to ensure that fish cannot swim into the system)
  • A penstock pipe (this allows the water to move from the intake to the turbine)
  • A powerhouse (where the turbine generates the electricity)
  • An outflow system (which allows the water to flow back into the water source)
  • Electricity cables (usually beneath the ground or overhead cables)

For domestic properties, micro hydroelectric systems can use the power of a small stream or river to provide up to 100kW of electricity which can be used to power appliances, lighting and electrical heating systems, although most properties would require a smaller amount of energy. Small-scale hydroelectric systems obviously only work when your property is situated close to a stream or river. Systems come in two types, those that are connected to the mains grid and those which are not.

Stand-alone (off grid) systems use an inverter or battery bank to directly supply appliances with electricity. However, if there are significant changes in the level and flow of the water source used to power your hydro system throughout the year, it may be a good idea to keep a back-up power supply. If this is mains electricity, you can switch to a green energy or renewable tariff, more details of which can be found under the energy efficiency section of this pack. If your system is grid-connected you may be able to sell any extra electricity that is produced back to energy supply companies through the grid.

Some of the advantages of micro-hydro systems include:

  • High system efficiency (converting between 70% and 90% of the energy into electricity)
  • High level of predictability
  • Continuous production of energy means the possibility of selling back significant amounts of energy to the grid.

To produce hydroelectricity, water from a stream, river or canal is diverted through a turbine which turns the energy from the movement of the water into electricity via a generator. The amount of power that the turbine generates depends on the rate of water flow, which is related to the distance the water falls (from the top of the turbine) and the volume of water available.

Hydropower produces no waste products during operation and once in operation the energy source is free. It can even improve water quality through improved oxygenation of the river or stream.

Small hydro systems are particularly suited to rural areas and can supply electricity directly to the homes or can be used to charge batteries or as a back up to a diesel generator. If you are interested in micro hydro your property will need to be in an area with a good level of rainfall and good drainage.

Hydroelectric systems are classed as either low or high head systems, depending on the height from which the water falls. It is possible to produce 10 kW of electricity from a system with a relatively low head of water by using a micro hydro turbine. If you are thinking of installing a micro hydro system it is really important that you have accurate information on the flow rate of the water source as well as having a survey conducted to assess the suitability of your property and the best way of meeting your energy needs. The Environment Agency may be able to provide you with details of the flow rate of local water sources and can be contacted on 08708 506 506.

The cost of micro hydro systems is difficult to estimate, as they are dependent on a variety of factors, with no two sites being the same. They often involve a higher installation cost than other renewable technology systems however the benefits of year-round supply (meaning little or no money spent on energy bills) and the option of selling electricity back to the grid can help to offset some of this cost.

Lifespan and warranty

Hydroelectric systems are usually very robust and some systems come with warranties of up to 10 years. However, as with all technologies, it is always advisable to find out about warranties and guarantees from a registered installer when they carry out an estimate.

Cost

Due to the individual nature of each location, there is no typical system cost for small-scale hydro systems, however sites with an existing weir will benefit from reduced costs.

Contact details

South Derbyshire District Council
Energy Officer
Civic Offices
Civic Way
Swadlincote
DE11 0AH

Tel: 01283 595974
Online: contact form
email: energy@south-derbys.gov.uk

Page ref: SDDC 134

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