Hydropower : Penstock

Components of Hydropower :

Penstocks 

 Penstocks are the pipe that conveys flow from the head pond or the forebay to the turbines.They are also called pressure conduits. Penstocks are usually made-up of steel, although reinforced, concrete, GRP, HDP penstocks have also been built in increasing numbers. 

Type of Installation of Penstock:

1) Exposed Penstock

2) Embedded or steel tunnel liner

3) Buried Penstock

1) Exposed Penstock : Are installed above the terrain surface and supported on piers.

Advantages

·         Continuous and adequate inspection, maintenance and repair.

·         Less expensive installation in case of large diameters.

·         Safety against sliding may be ensured by properly designed anchorage.

Disadvantages

·         Full exposure to external variations in temperature.

·         Water conveyed may freeze.

L          Longitudinal stresses may develop especially in pipes of larger diameter designed for low internal pressures.

2) Embedded or steel tunnel liner: •      Also called steel tunnel liner

•      These are located in a tunnel and fully encased in concrete or encased in a portion of dam.

3) Buried Penstock: Are supported continuously on the soil at the bottom of a trench backfilled after placing the pipe. The thickness of the cover over the pipe should be about 1.0 to 1.2 meters.

Advantages

·         Soil cover protects against untoward effects of temperature variations.

·         Protect conveyed water against freezing.

·         Do not spoil landscapes.

·         Immunity against rockslides, avalanches, falling trees.

·         Protection against violence.

·         Preferable from the structural point of view.

Disadvantages

·         Less accessible for inspection, maintenance, repair.

·         Installation is expensive. If friction coefficient of soil is low on step hillsides it have tendency to slide.