In the present electrical market there is an increasing penetration of intermittent energy sources. Several studies have examined its effect on the planning of hydropower operation and the conclusion is that an increasing intermittent production is likely to result in a more variable hydropower operation, utilising a wider span of operational set points. The wear of a hydropower unit is generally at a minimum when operated close to best efficiency and increases when operating at higher or lower set points. This study introduces a method to calculate an operation dependent cost (ODC) function for an arbitrary hydropower unit or unit combination based on vibration measurements and operational data. The method is tested in a case study where an ODC is implemented in Akkats, located in the Small Lule River in order to evaluate its effect on operational pattern, profitability and balancing contribution. The results show that the implemented ODC mainly affects Akkats. For an increasing ODC, Akkats is operated closer to the best point of efficiency and the operational pattern gets less variable and the effect gets more apparent the lower the spot price. Akkats ability to follow the spot price is reduced, decreasing the earning per produced energy with a few percent­ages. Akkats balancing contribution decreases significantly more, due to a less variable operational pattern. The study compares the reduced ODC to the reduced spot income and concludes that the wear cost in Akkats has to be above 1,21 €/MWh in order to be economically feasible to include in the planning. The operational pattern for the simulated river is close to unchanged at highest price hours but during lower price hours an increasing ODC results in an increased production, due to an increasing mean flow and changed operational pattern in Akkats. More production during low prices hours results in a decreasing profitability for all plants along the river. The balancing contribution is close to unchanged in all plants except Akkats, since the production still follows the same pattern.

The growing share of installed wind power in the Swedish electricity system has caused concerns whether the available regulating power will be sufficient. Several studies have examined the need of regulating power using both statistical and modelling approaches. However, there is a risk that some aspects of the short-term regulation of hydropower might have been missed. By using one of Vattenfall’s hydropower planning tools, the short-term operation of The Lule River has been simulated with an increasing penetration of wind power. The tool includes detailed models of reservoirs, generating units including efficiency curves and start/stop costs. By introducing a day-by-day simulation with a seven-day window price forecast, updated with a new wind forecast for each iteration, a 21-days scenario has been simulated. Transmission limits are disregarded and the thermal production is reduced with the average wind production. To quantify and compare the regulation capacity, the regulation factor is introduced. It reflects the ability to utilise high-price hours and considering that the need of regulating power for the short-term perspective is reflected in the price it will also reflect the regulation capacity. It is shown that the regulating factor is correlated to the discharge factor,whichis the relation between the maximum discharge to the average statistical discharge for a plant. A high discharge factor provides the flexibility to utilise the fluctuations in price. The discharge factor is adapted to the plants placement in the reach, accounting for both reservoirs located upstream and downstream, especially for The Lule River which has been designed to regulate for the fluctuations in the load. The flexibility required by the rest of the Nordic rivers is quantified for future studies. It is concluded that The Lule River is able to meet some of the fluctuations of wind power production due to the overcapacity ininstalled power. The production can, at the expense of decreased efficiency of the generating units, alter the production to suit a more fluctuating price.It is important to emphasise that The Lule River alone cannot balance a large penetration of wind power. To fully take into account the effects of a large penetration of wind power the study must be expanded to include more scenarios. The study should include different types of hydrological prerequisites and the seasonal variations in power production as well as additional rivers.