Old water wheel site suitable for low head development
Typical burn with hydro potential
What Does it Cost?
The cost of hydro schemes varies considerably. The key factors that influence the cost are:
- Size of the scheme. A 500 kW scheme will cost more (but return more) than a 100 kW one. Generally the costs per kW diminish as the scheme size increases. Schemes under 30 kW typically provide a limited return.
- The steepness of the watercourse involved. A steeper watercourse means less distance between the intake and the turbine, therefore requiring a shorter pipe/lade. Pipe/lade costs, including the necessary civil engineering are normally one of the more significant elements of a scheme.
- The geography and geology of the land around the intake, pipe route and turbine house, in particular, the ease of the civil engineering. Steep terrain where it is difficult to arrange safe access for machines and significant areas of rock are normally the two factors that push up costs.
- High head systems are usually more economically viable than low head schemes. A low head scheme will require a lot more water to generate an equivalent power (and therefore return). This higher flow will require relatively large-scale civil engineering and larger pipe, turbine, etc.
- Electrical connection to the grid. Connection from the turbine house is usually made to either an existing meter location or direct to the grid network. If this is a significant distance, the cable required is needs to be large (and therefore expensive) to reduce losses. If the connection can be made as three phase, rather than single phase, this is beneficial. In addition, particularly for larger schemes, the local grid needs to have the capacity to take the generated power. Should the local distribution network operators (SSE or Scottish Hydro) need to upgrade the grid to provide capacity this can add significantly to the costs.
- Existing infrastructure. Any existing infrastructure in workable or repairable condition can deliver savings. This is more common on low head schemes, often old mill sites, where weirs, lades and outfalls may already be in place.