Close-up of a Francis turbine. Photo: Helge Hansen 

The various components in a hydropower plant are often designed for specific operational patterns or conditions, such as the use of continuous or variable speed. One can therefore imagine that production outside these specific operational patterns will lead to increased stress on the powerplant. This increased stress usually leads to more frequent repairs and replacements of parts, which often means significant expenses for the power producer.

In order to reduce these expenses, it is important to plan and weigh up how the current productional pattern and income affect the future expenses that the current operational pattern will cause for the facility. When making such difficult choices, it is important to have good figures and data to rely on in the production planning.

In his project, Arnt Ove Eggen has developed a model for these operational pattern-related costs. The model is a continuation on a model for the cost of a start/stop of the hydropower unit, where the model includes both the duration of the stoppage as well as the plant's technical condition. The model can also be used to estimate the cost of "ramping", i.e. how quickly you slow down or increase production, and the cost of operating the powerplant with loads the plant is not normally designed for (partial load and/or overload).

The results from the model should be included as input parameters to models or software that calculate the disposition of available water resources. It is therefore a good resource to be able to make better considered decisions related to production planning in various plants.

Part of a larger project

The model is part of a larger spreadsheet that was created in 2002 as part of the project "Start/stop and technical-economic consequences", and which was updated in 2010 as part of the project "Value-creating maintenance within power production". 

The model is calculated to look at production costs for a "typical Norwegian hydropower plant" with a main valve and a Pelton or Francis turbine, and with between 50-200 starts/stops a year.