Construction & characteristics

Construction details of a microhydro plant are site-specific, but the common elements of all hydroelectric plants are present. A supply of water is needed — this can be a mountain stream, or a river. Usually microhydro installations do not have a dam and reservoir, relying on a minimal flow of water to be available year-round. Sometimes an existing mill-pond or other artificial reservoir is available and can be adapted for power production. An intake structure is required to screen out floating debris and fish, using a screen or array of bars to keep out large objects. In temperate climates this structure must resist ice as well. The intake may have a gate to allow the system to be dewatered for inspection and maintenance.

Water withdrawn from the source must move along a power canal or a pipe (penstock) to the turbine. If the water source and turbine are far apart, the construction of the penstock may be the largest part of the costs of construction. In mountainous areas, access to the route of the penstock may provide considerable challenges.

At the turbine, a controlling valve is installed to regulate the flow and the speed of the turbine. The turbine converts the flow and pressure of the water to mechanical energy; the water emerging from the turbine returns to the natural watercourse along a tailrace channel.

The turbine turns a generator, which is then connected to electrical loads; this might be directly connected to the power system of a single building in very small installations, or may be connected to a community distribution system for several homes or buildings.