Hydro Power - Civil Engineering

Weir and Intake

A (overflow) weir maintains a constant water level in the river at this point. This allows to divert a constant amount of water from the river into canal, penstock and turbine. If there is substantial silt in the water (muddy or sandy grounds) it requires a flush gate. Such gate can be opened to clear out silt which is usually transported with waters downstream but settles before a weir.

Intake is the structure between river an canal. It consists of a gate to open/close the water feed. A rake prevents major debris to enter the system. The intake is located preferably on an outside of a river bend in a way that silt and debris is not “automatically” streamed in. Due to it’s location in/on the river it is to be designed to withstand floods.

Canal

The canal transports the water towards the point where it drops steeply. To gain much height difference possible it is aligned with as little slope as possible. Canals usually lay on valley slopes. It is to be secured that no waters cross the canal uncontrolled (flushing above or under) from its side.. 1 - ½ meter path between hillside and canal allows its comfortable maintainance and prevents slides blocking the flow.

Forebay and Trash Rack

In the forebay tank the connection towards the penstock must not be the lowest point. The lowest point is towards a flush pipe. At such sand and mud can be flushed out during maintenance intervals. The forebay is closed by a trash rack. It's preventing  any debris entering the penstock!
Trash rack Features: As wide as possible to prevent quick blocking by debris. Grid should be cleanable by a rake from the top. Easy access and comfortable handling make regular cleaning more probable.

Pipeline (Penstock)

Within the penstock pipeline the height difference creates pressure on the water. The pressurized water feeds the turbine. On top of the penstock a breather pipe prevents negative vacuum effects within the pipe during sudden shutting of the shut-off valve. This valve is mounted directly before the turbine. It allows to close the water flow during maintenance or in emergency. This is to be done carefully to prevent a water hammer (strong pressure impulses). A pressure gauge mounted on the pipe before entering the turbine indicates the “net-head”. It also allows to monitor eventual irregularities within penstock or turbine.

Penstock is to be rested on support blocks in a way that they can slide on top due to heat/cold expansion/shrinking. Expansion joints are required to avoid changes in length to damage the structure. No forces from penstocks must act on neither forebay nor turbine. Avoid steep angles (>135º) in pipe conduction. It reduces net-head and degrades much quicker than straight pipe (strengthening required on outer bend of an elbow).

Shut-off Valve

 

A shut-off valve is necessary, and should be directly in front of the turbine in case an immediate shutdown of the system is required. This valve should be of high quality and very durable. It is recommended that to  close and then open the valve slightly on a regular basis to insure they don’t become seized in the open position and then don’t function when most needed.

Power House

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The turbine, generator, and electrical control boxes should all be "housed" in a weather proof building, where waterpower s converted to energy.  The building should resist inclement weather, animals, and intruders (children & unwelcome visitors) .  

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Tail Race (water outlet

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A necessary and sometimes forgotten component in design is the tail race. Water must have a convenient and non-restricted path back to the stream or pond. In cold climates, these returns must be designed to prevent freezing in the winter. The tail race must also be designed to prevent erosion, since a large continuous volume of water may pass through them.

Poles - Protection/durability

Das in den 70ger Jahre in Burundi eingesetzt "Boucheriesystem" hat sich nicht bewährt, da es nicht gegen Termiten wirksam war. Hersteller der Chemikalie WOLMANIT war/ist:  Dr. Wollmann GmbH   D- 7573 Sinzheim,   Tel. 0 72 21/800-0. Die zum notwendigen Mastkappen werden schon lange nicht mehr industriell hergestellt.

Das einzig wirksame Mittel in den Tropen ist: Teeröl/Kreosote, weil es auch gegen Termiten hilft.

Man kann die Maste "Tauchen - nicht sehr wirksam, da nur die Außenseite des Mastes bedeckt ist. Nach kurzer Zeit läuft das Mittel den Mast hinab. Zurück bleibt das nackte Holz. Einziger Vorteil: An der Erdübergangszone verdichtet sich der Schutz.

Wirksamsten Holz-Schutz bietet das industrielle "Druck-/Vakuumverfahren" mit Teeröl an.
Stahlrohrmaste sind zwar langlebig aber entschieden teurer als Holzmaste.
Als bester europäischen Hersteller von galvanisierten, achteckigen Stahlrohrmasten gilt für mich die Firma Petitjean, Frankreich.