Alternativ till fortsatt elektrisk generering i Olidan
In this thesis a possible cost effective runner change of some of the units in the hydroelectric power station Olidan is investigated. The possibility to drive a unit at the same efficiency point through a change of the turbine shaft speed and the rate of discharge is tested. Furthermore the theories behind model testing, determination of efficiency increase from model to prototype and efficiency measurements shall be discussed and analyzed with Olidan as a starting point.A predicted curve has been built on information from model tests and field measurements on the existing runners and runner data from the test of the new model. The predicted curve shows the difference in efficiency between an existing runner and a modern one. It is the difference in efficiency that is used in the calculations that are to show whether changing to a pair of new runners will be cost effective or not. A calculation shows that the possible change is not cost effective. A modern runner gets better characteristics due to cavitation because of its more optimally designed runner vanes. This leads to fewer losses in the turbine chamber and enables the turbine to handle a greater discharge before problems associated with cavitation appear.From the model test data, the oak tree diagrams and the unit values, you can see that it is theoretically possible to keep the efficiency point constant while the net head varies. Handledare: Lennart