News articles – ReHydro

Key milestone in eel-friendly turbine design reached

Carina Belusa — Thu, 25 Jun 2026 08:52:59 +0000

Our most recent milestone makes a significant step toward making hydropower safer for one of Europe’s fish species most endangered by hydropower: the European eel.

Part of “Work Package 4 – Environmental improvements of refurbishments”, this marks the completion of numerical simulations for a redesigned turbine runner specifically optimized to improve eel survival during turbine passage. Since European eels are migratory, their long-established routes often lead them through countless river turbines. Many make it through without harm, but unlucky individuals can be critically injured or killed by the turbine blades. Previous studies have shown that the design of the turbines the eels pass through on their journey plays a big part in their safety, leading to ReHydro taking on the challenge of developing a turbine that greatly reduces the risk eels face on their migration and show that hydropower refurbishment has as many environmental benefits as it has financial ones.

The design work was grounded in a thorough review of eel physiology and literature (read the first steps here) and drew on input from partners across the project: CNR, EDF, EDP, and NINA. Using the European Standard Norm prEN 18110 as a framework, the team built an analytical model for predicting eel survival and embedded it directly into GE Vernova’s simulation pipeline. That allowed them to iterate on turbine runner geometry with both eel safety and hydraulic performance in mind.

The results are encouraging. Compared to a conventional Kaplan turbine design, the optimized turbine shows a notably lower probability of eels being exposed to damaging blade strikes. The key changes were targeted modifications to the leading edge profile and a reduction in blade count, while keeping pressure conditions within safe limits for passing eels. Hydraulic efficiency took a small hit, described in the report as “minimal yet non-negligible”, which ReHydro considers a reasonable trade-off.

The simulations were developed using the Belver hydropower plant in Portugal, operated by EDP, as the reference case.

Work is now turning toward physical validation. Next steps include reduced-scale model testing, a scan of the existing Belver runner for direct comparison, and calibration of the survival models against live fish test data from CNR and EDF field sites. All findings will feed into a final synthesis report under deliverable D4.2.

Fourth Consortium Meeting in Sion

Carina Belusa — Mon, 22 Jun 2026 10:35:41 +0000

ReHydro’s fourth Consortium Meeting brought together partners from across Europe for four days of presentations, excursions, and collaboration in and around Sion, Switzerland. It was by far our most eventful one yet!

A look at EPFL's test facilities

The day before the official opening, the consortium visited EPFL’s facilities in Lausanne, guided by Elena Vagnoni, leader of Work Package 2 – Flexibility Solutions. She walked the group through four test rigs, with the final one reserved for ReHydro’s own work.

In it, a Kaplan turbine hybridized with a battery was spinning at 1,500 rounds per minute. The only way to properly see it in action was under a flashing strobe light- and by quite literally going underneath the rig.

It was a fitting first in-person look at the work done in WP2. One of the central challenges hydropower faces today is the growing demand for flexibility: turbines are increasingly required to turn on and off rapidly in response to sudden spikes in energy demand, which accelerates wear and tear well beyond what they’d normally experience. When a turbine is hybridized with a battery, the battery can serve as an instantaneous energy source, absorbing the pressure of those sharp demand peaks and allowing the turbine to run at a steadier pace. This reduces wear while still delivering the flexibility the modern grid requires. By varying environmental parameters in the test rig, such as head heights and river water levels, this can be tested in detail and under realistic conditions.

Getting a tour of the laboratory was a great start to the week, but by far not the only excursion planned for it.

Day One: Work Packages

The official opening day took place at our partner HES-SO Valais-Wallis in Sion, with a warm welcome from host partner Alpiq before diving into a packed agenda.

A special moment came when Work Package 3 – Fit for Market took the floor. As well as sharing updates, they closed their own chapter: the planned work is now complete. While not an official project milestone, it’s a reason to celebrate no less.

The day wrapped up with an inspiring presentation from Matthias Gäumann, CEO of HYDRO Exploitation SA, followed by a social dinner giving the consortium members the opportunity to gather and catch up.

Day Two: Excursion to Forces Motrices de la Gougra

While day one was about presentations, day two was about perspective.

The consortium split into two groups early in the morning and headed to the Mottec hydropower plant in Vissoie and the Navizence intake respectively, later switching so everyone got to see both. Guided by project partner HYDRO Exploitation SA, the group learned about the history and operation of the entire Forces Motrices de la Gougra (FMG) system: how the facilities work together, the reasoning behind key decisions over the years, and planned future refurbishments. People were engaged, and many questions were asked.

Some highlights from what the group learned: more than half of Switzerland’s energy production comes from hydropower. The FMG system is already well into a series of modernisation and refurbishment measures, including a planned heightening of the Moiry Dam, which already stands at an impressive 148 meters and sits roughly 2,250 meters above sea level.

After regrouping for lunch in the picturesque village of Grimentz, the full consortium headed to the Moiry dam and reservoir; the largest in the FMG system. Sturdy clothes and hiking boots were the dresscode, despite walking around a lake, the path turned out to be quite steep in places.

At this time of year, the water level is expected to be relatively low. Glacial meltwater from Moiry and other sources will gradually fill the reservoir through the summer until around September, when demand for energy rises, daylight shortens, and photovoltaic output drops. That’s the moment hydropower steps up as a renewable source unaffected by the change in daylight hours.

That said, hydropower is far from immune to the pressures of a changing climate. The Moiry Glacier has been retreating for years, and this year’s yield from glacial melt and general snowmelt was slightly lower than usual. Climate change is affecting hydropower directly, and many of the modernisation efforts underway in systems like FMG are specifically aimed at ensuring hydropower remains a reliable energy source in the decades ahead. It’s a challenge ReHydro takes seriously, so visits like this one serve as a great visual reminder of exactly what the project is working towards.

Day Three: Demonstration Sites and group work

With all Work Package updates already covered on the opening day, the final day of presentations focused on updates from ReHydro’s demonstration sites. Overall, things are going very well. Some adjustments to earlier plans have been made to better align with ongoing refurbishment efforts at the sites, and the first publishable results are expected soon.

This also freed up time for something that tends to generate some of the most valuable conversations of any consortium meeting: structured group work. With people from all partner organisations and work packages deliberately mixed together, the groups tackled ReHydro’s core themes: flexibility in pumped storage and hybridization with batteries, fish migration and turbine passage, societal services, economic sustainability and markets, and climate change resilience. The last of these sparked particularly lively discussion, fresh off the visit to Moiry Dam and the visible impact of glacial retreat on water availability. Bringing together people from different workstreams was intentional, and the energy in those groups showed it was worth it.

The meeting closed with final words from project coordinator Atle Harby and advisor Klaus Jorde, before the group headed into summer with new ideas and renewed energy.

Excursion to the Forces Motrices Hongrin-Léman (FMHL) pumped storage scheme

For those who could stay, the meeting wasn’t quite over. A sizable group made a final trip to Veytaux to tour the Forces Motrices Hongrin-Léman (FMHL) pumped storage scheme. With temperatures in Switzerland well above 30°C that day, stepping into a power station built inside a cave was, to put it mildly, a welcome bonus.

ReHydro would like to thank HES-SO Valais-Wallis for hosting the meeting, HYDRO Exploitation SA and Alpiq for the extraordinary excursions, and all consortium partners for their continued dedication to the project.

Advanced monitoring technologies validated across three demonstration sites

Carina Belusa — Tue, 12 May 2026 06:45:50 +0000

Hydropower plants across Europe are facing growing pressure from two directions at once. On one side, climate change is intensifying sediment loads in rivers, accelerating wear and erosion on turbines and other components. On the other, the shift to a more flexible, renewables-heavy electricity grid is pushing plants to operate across a wider range of conditions. This increases the risk of cavitation, vibration, and fatigue damage, which ultimately result in unplanned downtimes for maintenance, during which the hydropower plant cannot operate.

We have now taken a big step towards a solution. Building on earlier concept validation work, the ReHydro team has now moved to real-world implementation across three demonstration sites, focusing on gathering reliable data under actual operating conditions.

At the Valeira hydropower plant in Portugal, an integrated monitoring system has been deployed to track both long-term efficiency and cavitation phenomena in Kaplan turbines. The system draws on acoustic sensors, a dedicated data acquisition setup, and both local and cloud-based infrastructure. Operational data from the plant’s SCADA (Supervisory Control and Data Acquisition) system is used to evaluate turbine performance, while several multivariate regression models have been developed to estimate expected efficiency, allowing the comparison between measured and predicted performance. The results confirm that it is possible to build a robust methodology for long-term efficiency monitoring using existing plant data, while also detecting cavitation events and their spatial non-uniformities across different operating regimes.

In Switzerland, at the Vissoie and Bitsch plants, the focus has been on understanding how sediment affects Pelton turbines. A comprehensive monitoring architecture has been installed, combining thermodynamic efficiency measurements, turbidity and density sensors, high-frequency accelerometers, and a dedicated imaging system for tracking bucket erosion. These field measurements are complemented by computational fluid dynamics simulations and laboratory analyses, providing both real-time estimates of sediment concentration and detailed insights into erosion mechanisms. Especially the imaging system makes a case for future automated erosion analysis using artificial intelligence.

In Norway, the Røldal–Suldal system has served as a testing ground for digital integration. Parallel digital twins of the hydropower system have been developed to simulate plant behaviour across different operating conditions, and a transient digital twin captures dynamic processes in real time. By feeding these models with live operational and environmental data, the team has been able to validate simulations, test optimisation strategies, and demonstrate that digital twin frameworks can meaningfully support production planning and operational decision-making.

Across all three sites, the results point in the same direction: advanced monitoring technologies, combining on-site measurements, data-driven analysis, and numerical modelling, are technically feasible under real operating conditions and can deliver consistent, high-quality data with genuine value for predictive maintenance and refurbishment planning. The work reinforces the broader ReHydro ambition to support the digitalisation of hydropower, and with it, the long-term reliability and sustainability of a technology that remains central to Europe’s low-carbon energy future.

A full account of the methods, results, and findings will be made public in the future.

ReHydro’s First Open Webinar: Barriers and Drivers in Modernising European Hydropower Fleets

Carina Belusa — Fri, 20 Mar 2026 08:20:26 +0000

ReHydro held its first ever open webinar in collaboration with D-HYDROFLEX on March 18^th, bringing together around 80 participants from across the hydropower community for an hour and a quarter of study findings, input from operators who placed these findings in the broader context of day-to-day hydropower operations, and live discussions. A promising start to what will become a regular format!

Understanding why modernisation decisions are made or not made is a prerequisite for making ReHydro’s work genuinely useful to hydropower plant operators and owners. In April 2025, we set out to answer this question: we conducted a study across Europe asking the question “what is actually driving the modernisation of ageing hydropower fleets, and what is holding it back”? A year later, we could now present the answers

Quentin Boucher from SUPERGRID walked attendees through the findings from our survey, as well as the project’s broader analysis of how flexibility needs, market and policy developments, licensing processes, and environmental requirements are shaping upgrade decisions across the continent. This was complemented by the results of a similar study conducted by the D-HYDROFLEX project, a parallel EU-funded initiative focused on digital solutions for hydropower, presented by Katerina Drivakou. Discovering synergies and divergences between the two studies in the following live discussions was a particular highlight of the session.

Following the presentation of the study findings, Jérôme Auguste from EDF and Even Tjørhom from Lyse joined the panel discussion from the hydropower operators’ perspective and contextualised ReHydro’s and D-HYDROFLEX’ findings within the practical realities of operating hydropower assets. Their contribution broadened the scope of the webinar substantially, and kicked off the FAQ closing the webinar.

Participants ranged from students to established industry professionals and experts, and the questions and input from the audience enriched the discussion throughout. Project coordinator Atle Harby moderated the session.

For those who missed it or were unable to attend due to time zone differences, the full recording is freely available on ReHydro’s YouTube channel. Subscribe there to be notified of future recordings, and follow our LinkedIn and newsletter to be notified of future webinars well in advance- the next one is already being planned for September!

Life Cycle Assessment

Carina Belusa — Mon, 08 Dec 2025 06:52:38 +0000

Hydropower plants are able to produce low-carbon electricity during their service life. To maintain or extend their initial lifetime, refurbishment actions can occur to retrofit and modernise existing hydropower plants. Quantifying the environmental performance of these actions is important to minimise the impacts of the hydropower systems.

To evaluate these impacts in a consistent way, the ReHydro project applies Life Cycle Assessment (LCA), a standardised methodology to quantify potential environmental impacts. In the context of Work Package 5, an LCA study is carried out on one of our demonstration sites owned by our partner CNR (Compagnie Nationale du Rhône) near Caderousse. Two refurbishment actions of this run-of-river hydropower plant have been proposed by CNR and ENGIE tailored to the demonstration sites’ needs:

The construction of a new fish ladder to ease the passage of different fish species.
The construction of a Small Hydropower Plant (SHPP) to compensate for the producible loss occurring due to a French regulation, which mandated an increase of the environmental flow (water dedicated purely to the ecosystem) and thus a decrease of the water available for hydropower production.

These different actions were integrated in scenarios that will be thoroughly examined via the LCA-study to understand their environmental impacts. The final deliverable will include the complete LCA analysis of these scenarios and is expected in October 2026.

You can find the full paper in our knowledge hub!

Development of matrix of future water use

Carina Belusa — Mon, 08 Dec 2025 06:41:01 +0000

Across Europe, water is becoming an increasingly limited resource. Rising temperatures, longer low-flow periods and more frequent flash floods are putting tension on many aspects on our lives; from hygiene and public health over socioeconomical topics such as agriculture, to leisure activities like fishing or swimming. Especially southern Europe is affected during summer. Competition for water is already happening, and is expected to worsen in the coming years.

To help anticipate and manage these issues, our partners from EDF have developed a methodological framework to assess the satisfaction of future water use under different climate change scenarios, and applied it to our demonstration site Saut-Mortier in the Ain Valley, France. “Water use” in this case describes an ecosystem service consumed in a defined area over a given period. These services have been divided into four categories:

Supply services (food, drinking water, … .)
Regulatory services (erosion control, habitat for aquatic life, … .)
Support services (any necessary to produce other services)
Cultural services (fulfil aesthetic, symbolic, and recreational values)

The matrix developed by our partners assesses the compatibility of different water use cases, depending on which category they fall into. This will give us a better overview of where water is needed most, and where events such as low-flow periods or flash floods pose the highest risk. Hydropower operations can help alleviate the problem – once we know where to act.

The first application of the matrix will take place on the at the Saut-Mortier demonstration site on the Ain River. Using the digital twin developed in Work Package 2, our partners will test future hydro-thermal scenarios under different climate change conditions, and compare them with usage satisfaction criteria based on the developed matrix. In following steps, the matrix will be applied to other demonstration sites as well (e.g. on the Rhône River), and results will be linked to social benefits and stakeholders’ perceptions.

The full deliverable is available right here in our knowledge hub!

Research for monitoring technologies successful

Carina Belusa — Fri, 05 Dec 2025 10:56:36 +0000

As global efforts majorly move towards renewable energy sources, hydropower’s role in the energy grid continuously grows. It is already the largest source of renewable electricity in Europe, and demands are rising. However, increased hydropower production increasingly experiences two big challenges: Climate change and the operational requirements of a dynamic electricity.

Climate change is altering the environment, melting glaciers and causing more sediment in rivers and reservoirs used in hydropower operations. The increased amount of sediment places strain on hydropower plant components, such as turbines, which suffer damage and erosion much quicker than before. Similarly, the demand for hydropower plants to operate more flexibly and respond to immediate trends also increases wear-and-tear on component due to cavitation, vibration, and other stress factors.

To combat these challenges, our partners have developed and tested a series of monitoring solutions and tools across three of our demonstration sites: Valeira (Portugal), Vissoie and Bitsch (Switzerland), and Røldal–Suldal (Norway). All three sites are affected differently by the aforementioned challenges, which makes them excellent testing grounds to explore which monitoring systems work best for their unique cases, and can be applicable on a grand scale. Systems employed include acoustic sensors, cloud-based analytics, and virtual powerplants (digital twins).

The research conducted by our partners turned out positive, and tests successful. It became clear that various combinations of monitoring solutions are not only feasible, but have potential to significantly contribute to extended asset lifespans and reduced operational costs. This creates opportunities for refurbishment decisions and thus ultimately enhance the role of hydropower as a provider of flexibility and stability in Europe’s future low-carbon energy system.

Temperature modelling in the Ain River

Carina Belusa — Mon, 13 Oct 2025 09:06:10 +0000

The Ain River hydropower chain is one of France’s most strategically important systems for energy production and water resource management. It stretches approximately 60 km along the Ain River and includes six main installations. Among them are the Saut-Mortier reservoir and Vouglans dam.

Even before ReHydro, EDF has been working to modernize this hydropower system and enhance its flexibility. The focus is on transforming the Saut-Mortier reservoir into a pumped-storage hydropower facility capable of storing and releasing energy on demand. Additionally, the 40 km stretch of the downstream river is included in the impact assessment.

Now, the project team has begun the first phase of studies to support this transformation. Retrofitting the site with variable-speed reversible generating and pumping units will allow for better use of water, improved response to grid needs, and reduced environmental impacts, including lower hydropeaking intensity, better temperature regulation, and more controlled algae growth through managed water releases.

To support this work, EDF has been improving and testing detailed 1D and 3D models of the reservoir system. These models simulate how temperature and water flow interact under different operational scenarios. By consolidating them into a fully 3D digital twin, we now have a more accurate representation of spatial thermal processes and vertical stratification.

With the groundwork done, the follow-up goal is to qualify the “environmental sensitivity” of each reservoir, which describes their response to changes in weather, flow, and temperature. To support this, a semi-automated simulation tool has been created to test large sets of operational scenarios and connect multiple reservoirs within the system. The first flow-temperature scenario series for the entire reservoir chain is already in development.

These early studies lay the foundation for a smarter, more climate-resilient hydropower network. By linking ecological knowledge with flexible infrastructure, the Ain River system is becoming a model for modern river basin management under changing climate conditions.

Development of a new tool to assess hydropower’s environmental pressure

Carina Belusa — Thu, 25 Sep 2025 05:54:43 +0000

Hydropower plays a key role in Europe’s renewable energy future, but it also puts pressure on rivers and freshwater ecosystems. To help hydropower operators and decision-makers better understand these impacts, ReHydro is developing a practical tool that assesses environmental pressures across the entire life cycle of a hydropower project.

This new approach doesn’t replace ecological assessments, but complements them by integrating insights from multiple fields: environmental sciences, ecology, and life cycle analysis (LCA). The goal is to offer a more complete picture of a new project or refurbishment measures affect biodiversity, both locally and globally.

The tool is designed to be used for support in the early stages of planning, when decisions about design and operation are still flexible. It uses publicly available and/or easily accessible data to help compare options and guide eco-conscious choices. Local indicators, such as habitat changes, species pressures, or water quality, will be considered to see which best reflect ecological impact, even when data is limited.

Ultimately, the aim is to create a biodiversity footprint index that supports sustainable decision-making. For a more in-depth look at the first stage of the work done, the deliverable is publicly available here in our knowledge hub.

Mapping habitat conditions in Brattlandsdalsåa and Roalkvamsåa.

Carina Belusa — Wed, 24 Sep 2025 07:14:36 +0000

In late August, researchers from SINTEF headed into the stunning surroundings of Brattlandsdalsåa and Roalkvamsåa to assess their current habitat conditions. These rivers are part of Røldal-Suldal power system and currently receive only local runoff, as the main water flow is diverted for hydropower production. Together with our partners at Lyse, NINA, Intoto and INRAE, we are working to understand how much water is needed to support healthy habitat conditions and boost spawning opportunities for the local population of large trout. By investigating the local habitat conditions and comparing them with the trout’s known habitat preferences, we gain a quick and effective understanding of current conditions, and a clear idea of what changes could help improve them. This research is part of ReHydro’s broader goal: showing how sustainable hydropower refurbishment can also mean better outcomes for biodiversity.

We’re exploring two different approaches to restore flow in these rivers. In Roalkvamsåa, we’re looking at the option of releasing environmental flow from a small hydropower plant. While this may slightly reduce the total power production, the potential environmental gains are significant and could make the loss more than worth it. Meanwhile, in Brattlandsdalsåa, we’re evaluating the possibility of pumping water from the downstream lake Suldalsvatn back into the river to secure flow in key spawning areas in the most downstream part of the river.

In our efforts, we’re combining high-tech tools with tried-and-true field methods. We’re testing a simplistic habitat assessment method developed by our partner INRAE (France’s National Research Institute for Agriculture, Food and Environment), and using both remote sensing technologies and traditional hydraulic-habitat survey techniques.