RainWindSun - Renewable Energy Swindon Wiltshire

Huntersbrook House, Hoggs Lane, Purton, Wiltshire SN5 4HQ - Tel: 01793 772277 - email

Micro Hydro System

How it works...

Micro Hydro FAQs

What is micro hydro?

Small-scale hydropower is one of the most cost-effective and reliable energy technologies to be considered for providing clean electricity generation.

In particular, the key advantages that small hydro has over wind, wave and solar power are:

  • A high efficiency (70 - 90%), which, arguably, is by far the best of all energy technologies
  • A high capacity factor (typically > 50%), compared with 10% for solar and 30% for wind
  • A high level of predictability, varying with annual rainfall patterns
  • Slow rate of change; the output power varies only gradually from day to day (not from minute to minute)
  • A good correlation with demand i.e. output is maximum in winter
  • It is a long-lasting and robust technology; systems can readily be engineered to last for 50 years or more

It is also environmentally benign. Small hydro is in most cases “run-of-river”; in other words any dam or barrage is quite small, usually just a weir, and little or no water is stored. Therefore run-of-river installations do not have the same kinds of adverse effect on the local environment as large-scale hydro.

How does micro hydro work?

Hydraulic power can be captured wherever a flow of water falls from a higher level to a lower level. This may occur where a stream runs down a hillside or where a river passes over a waterfall or man-made weir, or where a reservoir discharges water back into the main river.

The vertical fall of the water, known as the “head”, is essential for hydropower generation; fast-flowing water on its own does not contain sufficient energy for useful power production except on a very large scale, such as offshore marine currents. Hence two quantities are required: a flow rate of water, and a head. It is generally better to have more head than more flow, since this keeps the equipment smaller.

Will micro hydro work at my home?

In practice, sites that are suitable for small-scale hydro schemes vary greatly. They include mountainous locations where there are fast-flowing mountain streams and lowland areas with wide rivers. In some cases development would involve the refurbishment of a historic water power site. In others it would require an entirely new construction.

There is some essential information is needed to be obtained when considering your site for hydro generation:

  • A significant energy source will need to be identified. This involves estimating or measuring the flow and available head, and estimating what annual energy capture would result
  • If the potential output of a scheme is suitable, then you need to be certain that permission will be granted to use all of the land required, both to develop the scheme and to have the necessary access to it
  • There needs to be a clear destination for the power. Is there a nearby load that needs to be supplied, or is there a convenient point of connection into the local distribution network?

Is micro hydro easy to maintain?

Modern, automated equipment requires very little maintenance. As the machine ages, there will eventually be extra costs associated with replacing seals and bearings, a new generator, refurbished sluice gates, etc., but these should not occur for at least 10 years.

Will planning permission or licences be required?

Formal and informal consultation should underpin every stage of a development and may be handled either by the developer or by a hydro professional. Consultation will be tailored to each individual development. Some sites, for instance, may not be located on fishing rivers and therefore consultation with fisheries bodies or angling clubs would be limited. Similarly, where a site does not require planning permission, there is no need for detailed consultation with the relevant planning authorities.

Full consultation will ensure that any problems are identified at an early stage, and this may prevent the incurring of unnecessary expenditure.

All water courses of any size in England and Wales are controlled by the Environment Agency. To remove water from them (even though it may go back in) will almost certainly require their permission in the form of a licence. There are three licences that can apply to a hydropower scheme.

Abstraction Licence, if water is being diverted “away from the main line of flow of the river”. In practice, this means that the only type of scheme which can avoid an abstraction licence would be a barrage-type project where turbines are installed on an existing weir and the water remains between the existing banks of the river. All new abstraction licences are now time-limited to 12 years, after which they must be renewed. The Environment Agency has stated that there will be a “presumption of renewal”, but this is clearly an area of risk for new developments.

Impoundment Licence, if changes are being made to structures which impound water, such as weirs and sluices, or if new structures are to be built.

Land Drainage Consent, for any works being carried out in a “main channel”.

The Environment Agency may also require a Section 158 Agreement to be drawn up, which defines certain further details on the way the scheme must be operated in order not to conflict with the Agency’s river management duties, e.g. rights of access, the control of river levels, flood waters, maintenance of the weir and river structures, etc.