Increasing the flexibility of the hydropower system will have impacts on the environment and there is a need for knowledge and solutions for hydropeaking, pumping and expansion of existing power stations (increased capacity). In addition, societal effects and attitudes towards expansion of hydropower needs to be addressed. In the project Sustainable upgrading and expansion of the hydropower system researchers from different research topics will work together on challenges and cases from the industry to find solutions for a flexible hydropower system while minimizing or improving environmental and societal costs.

Solutions for flexible power generation

In RP-2.2, NTNU (EPT) aims to investigate the booster pump technology for the reversible pump-turbine. In Norway, several hydropower plants will be upgrades in next decade. Through this project work and with the help of two PhD candidates, NTNU (EPT) aim to study Francis type turbines and upgrade with the pump-turbines to enable operational flexibility. Traditionally, upgrading to pump-turbines requires the replacement of several components of the turbine and changing large structures of civil engineering. This puts extra capital expenditure and requires more resources including high cost. Through this project, we aim to minimize the replacement components of turbine (sustainable upgrading with minimum cost) and provide suitable capacity for the pump-turbine by integrating the booster pump technology. This allows us to reduce the reduce the structural changes at the draft tube and tail water side of the turbine. The requirement of suction head will be met by the booster pump integration in the draft tube.

More flexible operation of the hydropower system will introduce more stress on turbines, generators and tunnels and dams. The PhD candidate of NTNU (IEL) will therefore investigate the effects on generators. Additional losses/forces introduced by new harmonics in the magnetic field. Applying converter-fed synchronous machines (CFSM) implies that new harmonics in the magnetic field are introduced. This may cause additional losses and forces/vibration needed to be known and mitigated. The approach is to use numerical modelling that is verified in the laboratory, and then execute case studies in combination with RenewHydro partners. The research activity of SINTEF will work in synergy with the PhD candidate at IEL, and also RP-1.1, 1.2, and 1.3. Activities include continuous online monitoring of electrical discharges and offline data collection and data post-processing.

During FME HydroCen, a comprehensive instrumentation was carried out to assess the pore-pressure development in the rock mass due to pressure transient caused by changing operational environment (start-stop sequence) in pressure tunnels of Norwegian hydropower plants. It is revealed that there is a hydraulic impact on the rock mass due to pressure variation between tunnel and rock mass joints, which leads to long-term fatigue. This fatigue is expected to cause more block falls and collapses in the pressure tunnels. Therefore, the PhD research of NTNU (IGP) will therefore be oriented to quantify the extent of fatigue in different rock mass environments so that it is possible to find out the lifetime of pressure tunnels located at different geological formation where both existing and future hydropower plants are/will be located. The finding will be very important to the lifetime assessment of pressure tunnels for future Pump Storage Plants.

The core of an embankment dam is composed of an impermeable material to decrease seepage through the dam. The core can be exposed to deteriorating processes leading to internal erosion due to high hydraulic gradients and more. Internal erosion can result in a complete dam failure. It is needed to investigate the effects of pressure variations due to flexible hydropower operation on the core, and the potential to trigger deteriorating processes that will affect the lifetime of the dam. Also, rapid drawdown of the reservoir influences the stability of the dam slopes. Hence, the Phd research of NTNU (IBM) will create new knowledge relating to the effect of more frequent and rapid variable loadings on the core and or the slope stability. The findings will be important for dam safety evaluations and for the lifetime assessment of embankment dams.

Operational efficiency and marked designs

The research aims of USN's PhD candidate is to enhance the operational efficiency and economic performance of hydroelectric generators in the Nordic Flow-Based Market Coupling (FBMC by developing innovative flexible time aggregation methods). By creating advanced techniques that allow for variable and adaptive time intervals in hydroelectric scheduling models, the study seeks to capture short-term market dynamics and flexibility services more accurately. Additionally, it focuses on optimizing flexibility value stacking strategies, enabling hydroelectric generators to maximize revenue by simultaneously participating in multiple market services such as energy arbitrage, frequency regulation, balancing services, and congestion management. Assessing the economic and operational impact of these flexible time aggregation methods is also a key objective, evaluating benefits like increased profitability, improved resource utilization, and compliance with operational constraints. Finally, the research aims to analyze the implications for market efficiency and provide policy recommendations to enhance market design and regulatory frameworks, thereby supporting the effective utilization of hydroelectric flexibility in the Nordic FBMC.

Environmental effects and solutions

The environmental research in this project aims to gain a better understanding of the environmental effects of a more flexible hydropower system and develop mitigation measures. The research will be a collaborative effort between NINA, NTNU and NORCE. Specifically, the PhD will work on the broad topic of PSH and effects on the biodiversity, temperature, nutrient flow and species composition in reservoirs. The specific topic will depend on user cases and the candidate. The overall research aim is to develop knowledge and solutions that contribute to the protection of biodiversity and ecosystem function in regulated watercourses, as we increase the flexibility in the Norwegian hydropower system.

Potential research topics include:

• Pump storage hydro and effects on the biodiversity, temperature, nutrient flow and species composition in reservoirs
• Mapping ecological distance between reservoirs and develop knowledge and methods for assessing “environmentally acceptable” pump storage projects
• Hydropeaking: environmental effects and solutions
• Land use and carbon budgets in hydropower development
• Developing operational and physical mitigation measures of environmental effects of hydropeaking. This activity will be linked to IBM#PhD4
• The purpose of the PhD project of NTNU (IBM) will be to improve mitigation measures downstream hydropeaking power plants. We may also extend this analysis to pumped systems. Topic of interest is:
• Physical effects in reservoirs downstream a hydropower outlet. Effects on water temperature, circulation patterns, ice conditions and outflow into downstream rivers. Several examples exists where the hydropeaking signal is observed in the hydrograph in rivers downstream of such reservoirs. Similar analysis can also be performed for reservoirs in pumped systems.
• Develop improved mitigation strategies for recipients downstream peaking power plants. This will include improved operation procedures in reservoirs to dampen the peaking wave or improvements to the regulation structures to obtain dampening, for pumped systems also evaluate impacts in the upper reservoir. For rivers, improved operational constraints or physical changes to prevent dewatering of critical areas.
• Evaluate the environmental status in current pumped systems with the aim to understand physical and ecological differences from nearby natural or reservoirs without pumping operation.
• Contribute to guidelines for best possible operation of hydropower plants running hydropeaking and to make future increased flexibility environmentally acceptable
• Public acceptance of the expansion and upgrading of hydropower. To gain a better understanding of societal effects and attitudes NMBUs PhD candidate will use survey experiments requiring respondents to make challenging trade-offs between technological, environmental, and regulatory factors in discrete choice experiments. Acceptance will be analyzed across different regional contexts. Reuse of these survey experiments will enable us to assess the temporal stability of public acceptance over time.