Periodic Reporting for period 1 - STORE2HYDRO (Novel long-term electricity storage technologies for flexible hydropower)
Periodo di rendicontazione: 2024-01-01 al 2025-06-30
Europe’s energy transition increasingly relies on intermittent renewable sources such as wind and solar power, creating growing challenges for grid stability and efficient energy management. Existing storage solutions remain insufficient to absorb surplus generation during peaks and deliver it during lulls. Against this backdrop, the Horizon Europe–funded Store2Hydro project (Grant No 101136176), coordinated by Luleå University of Technology and running from 1 January 2024 to 31 December 2027, steps in with a forward-looking approach.
Stire2Hydro proposes a novel strategy: retrofit existing high‑head (reservoir‑to‑reservoir) and low‑head (river stretch to river stretch) hydropower plants with reversible pump‑turbine technology, enabling both generation and pumping. This intervention can dramatically expand Europes electricity storage capacity—by over 22 TWh per year. This approach seeks to enhance flexibility and efficiency without altering reservoir sizes or river volumes, keeping in step with the European Green Deals environmental and operational priorities.
Stire2Hydro proposes a novel strategy: retrofit existing high‑head (reservoir‑to‑reservoir) and low‑head (river stretch to river stretch) hydropower plants with reversible pump‑turbine technology, enabling both generation and pumping. This intervention can dramatically expand Europes electricity storage capacity—by over 22 TWh per year. This approach seeks to enhance flexibility and efficiency without altering reservoir sizes or river volumes, keeping in step with the European Green Deals environmental and operational priorities.
The partners involved in Store2Hydro have carried out robust technical and scientific activities across multiple work packages to deliver innovations for storage of electricity. To exemplify:
1. Mapping & Potential Assessment
The first work package, led by TU Wien, has systematically mapped Europe’s existing hydropower sites to identify reservoirs and river systems suitable for retrofitting with reversible pump-turbine setups. Using satellite and geospatial analysis, a database has been developed to quantify the storage potential of water reservoirs. This database encompasses information on over 1,200 hydropower plants across Europe, including fundamental parameters such as installed capacity and geographical location, as well as detailed technical specifications like storage volume and turbine runner types. To facilitate exploration and analysis, a categorization system has been introduced, grouping hydropower plants based on the extent of retrofitting required for their conversion into pumped storage systems. All processed data is derived from publicly available sources. Utilizing this dataset, a comprehensive mapping of the potential has been created through a visualization tool. The database will be further expanded and updated throughout the project.
2. Innovations
Under Work Package 2 by NTNU the is a development towards and experimental validated a novel rim-driven thruster integrated into a draft-tube system. This design aims to maintain sufficient suction head (NPSH), minimizing cavitation and enabling a wider operating range while keeping both CAPEX/OPEX low. Numerical simulations and analysis lay grounds for experiments in lab-scale physical models. In addition, to assess the potential of existing European hydropower infrastructure for pumped-storage, new digital tools have been developed. A computational tool was created to generate simplified river bathymetries from user-defined parameters such as cross-section, length, depth, width, slope, and side slopes. It can also include meanders and downstream reservoirs, enabling efficient creation of tailored river geometries. These geometries have been used in hydraulic models for RoR applications, and large-scale river dynamics under pumping operations are currently under analysis. Pumped-storage hydropower also influences sediment transport in both Reservoir-to Reservoir (RtR) and Run-off-Rivers (RoR, mainly river stretch to river stretch) systems. To investigate this, two hydraulic–sediment transport models were implemented. For RtR, a synthetic case was simulated using Flow3D Hydro (3D CFD), modelling turbine and pump operations and analysing sediment erosion and diffusion near dams. For RoR, eight synthetic cases with rectangular river sections and varying sediment sizes (from silt-clay to cobbles) were modelled in HEC-RAS 1D. These simulations evaluated large-scale channel modifications and the impacts of sediment trapping by barrages on upstream and downstream riverbed slopes.
3. Environmental & Cost-Effectiveness Analysis
A life cycle analysis (LCA) has been set-up for a pumped storage plant and several scenarios have been defined to evaluate the best one for reducing the PHS plant's environmental impacts. These scenarios will be set-up so the additional impact of integrating the reversible pump turbine (RPT) machine, developed in the project, can be studied.
For monitoring environmental impact, loggers placed in a reservoir are used. This includes so called HOBO loggers that are small, durable temperature and environmental data recorders often used in ecological research. A literature review on environmental impacts and societal acceptance of pumped hydro is now in the analysis phase, with key topics identified for further study. To support this, a survey on public acceptance is being prepared for autumn 2025, together with interviews of stakeholders and power companies involved in pumped hydro development.
4. Integration of wind/solar and hydropower in the energy system
For the integration of mainly wind/solar and hydropower in the energy system three parallel activities are carried out: dynamic system analysis, distribution network modeling, and techno-economic evaluation.
The dynamic analysis focused on large-scale integration of wind, solar, and hydropower, using simulation models to assess stability under high renewable conversion. Scenarios included grid disturbances, reduced inertia, and power-electronics-dominated systems. Results highligh the critical role of flexible hydropower storage in maintaining frequency and voltage stability, and work has begun on formulating high renewable grid scenarios, including weak grid configurations. For the distribution network modeling literature review have been carried out and scenarios have been tested on the IEEE 123-bus feeder. Findings showed that pumped hydro storage mitigates variability by balancing solar output, enhances flexibility through community-level coordination, and maintains system stability across different storage sizes and renewable mixes. These outcomes provide a basis for further stochastic and resilience-focused simulations. An optimization platform has been developed for the techno-economic analysis, first tested on a small-scale model, and prepared for large-scale integration studies using high-performance computing. Future work will incorporate detailed datasets to quantify system flexibility requirements and storage needs for high shares of wind, solar, and hydropower.
1. Mapping & Potential Assessment
The first work package, led by TU Wien, has systematically mapped Europe’s existing hydropower sites to identify reservoirs and river systems suitable for retrofitting with reversible pump-turbine setups. Using satellite and geospatial analysis, a database has been developed to quantify the storage potential of water reservoirs. This database encompasses information on over 1,200 hydropower plants across Europe, including fundamental parameters such as installed capacity and geographical location, as well as detailed technical specifications like storage volume and turbine runner types. To facilitate exploration and analysis, a categorization system has been introduced, grouping hydropower plants based on the extent of retrofitting required for their conversion into pumped storage systems. All processed data is derived from publicly available sources. Utilizing this dataset, a comprehensive mapping of the potential has been created through a visualization tool. The database will be further expanded and updated throughout the project.
2. Innovations
Under Work Package 2 by NTNU the is a development towards and experimental validated a novel rim-driven thruster integrated into a draft-tube system. This design aims to maintain sufficient suction head (NPSH), minimizing cavitation and enabling a wider operating range while keeping both CAPEX/OPEX low. Numerical simulations and analysis lay grounds for experiments in lab-scale physical models. In addition, to assess the potential of existing European hydropower infrastructure for pumped-storage, new digital tools have been developed. A computational tool was created to generate simplified river bathymetries from user-defined parameters such as cross-section, length, depth, width, slope, and side slopes. It can also include meanders and downstream reservoirs, enabling efficient creation of tailored river geometries. These geometries have been used in hydraulic models for RoR applications, and large-scale river dynamics under pumping operations are currently under analysis. Pumped-storage hydropower also influences sediment transport in both Reservoir-to Reservoir (RtR) and Run-off-Rivers (RoR, mainly river stretch to river stretch) systems. To investigate this, two hydraulic–sediment transport models were implemented. For RtR, a synthetic case was simulated using Flow3D Hydro (3D CFD), modelling turbine and pump operations and analysing sediment erosion and diffusion near dams. For RoR, eight synthetic cases with rectangular river sections and varying sediment sizes (from silt-clay to cobbles) were modelled in HEC-RAS 1D. These simulations evaluated large-scale channel modifications and the impacts of sediment trapping by barrages on upstream and downstream riverbed slopes.
3. Environmental & Cost-Effectiveness Analysis
A life cycle analysis (LCA) has been set-up for a pumped storage plant and several scenarios have been defined to evaluate the best one for reducing the PHS plant's environmental impacts. These scenarios will be set-up so the additional impact of integrating the reversible pump turbine (RPT) machine, developed in the project, can be studied.
For monitoring environmental impact, loggers placed in a reservoir are used. This includes so called HOBO loggers that are small, durable temperature and environmental data recorders often used in ecological research. A literature review on environmental impacts and societal acceptance of pumped hydro is now in the analysis phase, with key topics identified for further study. To support this, a survey on public acceptance is being prepared for autumn 2025, together with interviews of stakeholders and power companies involved in pumped hydro development.
4. Integration of wind/solar and hydropower in the energy system
For the integration of mainly wind/solar and hydropower in the energy system three parallel activities are carried out: dynamic system analysis, distribution network modeling, and techno-economic evaluation.
The dynamic analysis focused on large-scale integration of wind, solar, and hydropower, using simulation models to assess stability under high renewable conversion. Scenarios included grid disturbances, reduced inertia, and power-electronics-dominated systems. Results highligh the critical role of flexible hydropower storage in maintaining frequency and voltage stability, and work has begun on formulating high renewable grid scenarios, including weak grid configurations. For the distribution network modeling literature review have been carried out and scenarios have been tested on the IEEE 123-bus feeder. Findings showed that pumped hydro storage mitigates variability by balancing solar output, enhances flexibility through community-level coordination, and maintains system stability across different storage sizes and renewable mixes. These outcomes provide a basis for further stochastic and resilience-focused simulations. An optimization platform has been developed for the techno-economic analysis, first tested on a small-scale model, and prepared for large-scale integration studies using high-performance computing. Future work will incorporate detailed datasets to quantify system flexibility requirements and storage needs for high shares of wind, solar, and hydropower.
Results are moving beyond the state-of-the-art in all areas described in the previous chapter. By following the project outline like taking part in main conferences on the subject and using recommendation from the Store2Hydro Advisory Board this will be secured.