Future power production in Europe is expected to include large shares of variable wind and solar power production. Norway, with approximately half of the hydropower reservoir capacity in Europe, can contribute to balance the variability. The aim of this paper is to assess how such a role may impact the Norwegian hydropower system in terms of production pattern of the plants, changes in reservoir level and water values. The study uses a stochastic optimization and simulation model and analyses an eHighway2050 scenario combined with increases in the hydropower production capacities in Norway. The capacity increases from ca. 31 GW in the present system to 42 and 50 GW respectively. The study uses 75 years with stochastic wind, solar radiation, temperature and inflow data. The results show that the hydropower system is able to partly balance the variable production and significantly reduce the power prices for the analyzed case. The paper shows that some of the power plants utilize their increased capacity, while other plants do not due to hydrological constraints and model limitations. The paper discusses how the modelling can be further improved in order to quantify more of the potential impacts on the future power system.

Maintenance scheduling is an important and complex task in hydropower systems. In a liberalized market, the generation company will schedule maintenance periods to maximize the expected profit. This paper describes a method for hydropower maintenance scheduling suitable for a profit maximizing, price-taking and risk neutral hydropower producer selling energy and reserve capacity to separate markets. The method uses Benders decomposition principle to coordinate the timing of power plant maintenance with the medium-term scheduling of the hydropower system, treating inflow to reservoirs and prices for energy and reserve capacity as stochastic variables. The proposed method is applied in a case study for a Norwegian watercourse, and results, in terms of maintenance schedules and computational performance, are presented and discussed.

Thanks to its huge water storage capacity, Norway has an excess of energy generation at annual scale, although significant regional disparity exists. On average, the Mid-Norway region has an energy deficit and needs to import more electricity than it exports. We show that this energy deficit can be reduced with an increase in wind generation and transmission line capacity, even in future climate scenarios where both mean annual temperature and precipitation are changed. For the considered scenarios, the deficit observed in winter disappears, i.e., when electricity consumption and prices are high. At the annual scale, the deficit behaviour depends more on future changes in precipitation. Another consequence of changes in wind production and transmission capacity is the modification of electricity exchanges with neighbouring regions which are also modified both in terms of average, variability and seasonality.

New environmental constraints for hydropower improve ecosystems but reduce energy production and flexibility, creating a dilemma between protecting nature and ensuring a sufficient and reliable energy supply. Approximately 88% of Norway’s power comes from hydropower, produced by over 1770 plants. We assess how 285 potential new or revised environmental constraints affect hydropower production and flexibility in the Northern European power system. To do so, we combine a method for estimating environmental flow releases in bypass reaches and stochastic power system optimization. Our results show that reductions in hydropower output due to these constraints are consistent across power system scenarios and two power system models. The reductions amount to 3 TWh yr⁻¹ (2% of Norway’s production), by our estimates. These reductions are primarily driven by flow diversions to bypass river sections. Further, we find that high power prices increase and low prices decrease, reflecting reduced system flexibility. Price increases typically occur in dry spring periods and are linked to activation of season-dependent reservoir restrictions in that period, while price decreases result from higher reservoir volumes entering periods of rain-heavy summer or autumn periods, indirectly linked to restrictions active earlier in the year. In our simulations, we observe that flexibility losses due to environmental constraints to some degree are offset by increased flexible operation of unaffected reservoirs and transmission interconnectors. Finally, our findings suggest that reservoir restrictions may cause spilling, as higher water levels in regulated reservoirs increase the risk of spilling during wet summer or autumn periods. This system-level understanding is crucial for regulatory authorities designing new environmental requirements and revising the terms of hydropower licenses. Our study contributes to informed discussions for balancing hydropower production with local environmental benefits and offers a framework for studying similar constraints in other regions, such as Sweden, North America and European Alpine countries.