USE OF A TUNNEL/RESERVOIR TO OPTIMIZE PRODUCTION OF A HYDROELECTRIC POWER PLANT

Cel

The aim of the project is to use the tunnel as a reservoir. This solution, particularly adapted to medium and high head projects with a flow below 10-20 m3/s, has many advantages :
* from an ecological point of view, a reservoir can be built without flooding a big area or building a large dam. The visual impact of the tunnel/reservoir is very reduced.
* from a technical point of view, the use of a tunnel reduces the loss head, and thus increases the production. The water storage in the tunnel allows an increased turbine flow to produce during peak hours.
The high cost of the tunnel is compensated by increased revenues, from 128.160.000 esc. a year for a classic solution (canal and penstock) to 172.338.000 esc. a year for this solution. The efficiency rate with this solution is 11.3% versus 9.5% for a classic solution.

Located in the Portuguese Region Norte, the hydroelectric plant of Ucanha valorizes 125 meters of level difference in the Varosa river, which has a medium flow of 3,5 m3/s.
The classic solution is to divert the river with a canal and a penstock but a subsequent analysis of the situation indicated that a tunnel could be an alternative.
The high cost of the tunnel did not improve profitability, so the idea that the tunnel should not merely serve to channel the flow, but also be a reservoir to regulate the flow, thus permitting the turbine to operate at maximum efficiency and to increase operation at peak hours. The idea to use the tunnel as a reservoir is an innovation.
Details of the innovation and advantages :
Type of project : Innovative solution Classic solution
Rated power : 5300 Kva 3300 Kw
Net Head : 124 120
Maximum turbined flow : 5250 l/s 3.600 l/s
Annual production 14.806.000 kWh 11.638.484 Kwh
Total cost (TC) 1.395.354.000 Esc 1.211.018.000 Esc
Estimated Revenues
(1993 base) (R) 172.338.000 Esc 128.160.000 Esc
Efficiency 11.3% 9.5%
Interest of the innovation :
* Ecological :
For the UCANHA project, it is not possible to create a reservoir with such a small dam. A similar problem occurs with many projects.
Ponding with dams creates many problems for the environment. The visual impact of the tunnel/reservoir is particularly reduced.
* Economic :
Using the tunnel as a reservoir will increase the storage capacity as well as production and revenues. It allows an increase in maximum producible power as the load losses in the tunnel are minimized. * Technical
The tunnel/reservoir has also the following advantages :
- water velocity being very low, the tunnel will allow a good settlingis is a relevant matter as Francis runners are particularly sensitive to foreign elements.
- low water velocity allows to reduce load losses from 8 m for a classic configuration to 3 m for tunnel/reservoir configuration.
Technical risks :
It is difficult to assess the risk of drilling a tunnel even though we have and will have geological reports based on seismic tests/core drilling.
The use of a tunnel increases the possibilities of air-binding due to pockets in the tunnel, while the filling and emptying of the tunnel may deteriorate the walls.
Finally, the use of a complete system of chamber regulation will create an advantageous situation, but it also introduces new problems which will have to be solved. The regulation will include the following parameters : 1) Measurement and control of upstream water level, 2) Measurement and control of levels inside the tunnel/reservoir, 3) Measurement of flow rate from the river to the water intake, 4) Control of the flap gate position according to theflow rate.

Program(-y)

ENG-THERMIE 1 - Programme (EEC) for the promotion of energy technology in Europe (THERMIE), 1990-1994

Temat(-y)

Data not available

Zaproszenie do składania wniosków

Data not available

System finansowania

DEM - Demonstration contracts

Koordynator

HIDROELECTRICA DE CASAL

Wkład UE

Brak danych

Adres

Portugalia

Koszt całkowity