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 steaply. 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

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)

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Penstock pipeline carries water from forebay tank to the power house. The pipeline delivers water to the turbine from the settling tank and must be sized properly to prevent frictional losses from robbing available power. This will be a cost/benefit trade-off since a long penstock can cost more than the turbine. Penstocks should be buried if possible to protect them and prevent freezing in cold weather climates. The penstock should include a breather pipe, ideally near the settling tank. This will prevent the disastrous event known as an implosion. Depending upon the pipe chosen, and if the intake were to suddenly be shut off – a huge vacuum would develop in the pipe. This is caused by the water’s momentum and can be of a large enough magnitude to cause the pipe to collapse.

 

A pressure gauge should be installed at the end of the penstock, right in front of the turbine shut-off valve. It will be a quick way to monitor how the system and penstock are performing. A quick reading of the pressure shows if there is a change or a problem. Additionally, by monitoring this gauge when  closing the turbine shut-off valve water hammer problems can be detected. Water hammer is the opposite of the implosion issue noted above. If the valve is closed too quickly, the momentum of the water can dramatically increase water pressure to the point of bursting the penstock. Shutting down systems water flow should be done carefully.

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 früher benutzte "Boucheriesystem" hat sich in den Tropen nicht bewährt, da es nicht gegen Termiten wirksam war. (haben wir seinerzeit [70ger Jahre] in Burundi eingesetzt)

Hersteller der Chemikalie WOLMANIT war/ist:  Dr. Wollmann GmbH   D- 7573 Sinzheim,   Tel. 0 72 21/800-0

Die zum "Boucheriesystem" 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" ( wir haben während der Exkursion das Tauchbecken gesehen) - 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.

Den einzig wirksamen Schutz bietet das industrielle "Druck-/Vakuumverfahren" mit Teeröl an. 

Stahlrohrmaste sind zwar langlebig aber entschieden teurer als Holzmaste, ggf. muss man Kompromisse machen.

Als bester europäischen Hersteller von galvanisierten, achteckigen Stahlrohrmasten gilt für mich die Firma Petitjean, Frankreich.