Frequently Asked Questions

Refurbishment decisions are usually triggered by a combination of technical, operational, economic and environmental challenges. In many existing hydropower plants, turbines were originally designed for stable base-load operation, while today they are increasingly required to operate under flexible, off-design and transient conditions. This can lead to higher mechanical stress, lower efficiency, increased fatigue, cavitation, pressure pulsations, vibration, unplanned downtime and higher operation and maintenance costs. REVHYDRO specifically addresses problems occurring away from the Best Efficiency Point, including deep part-load inter-blade vortices, part-load rotating vortex rope phenomena in the draft tube and full-load hydraulic instabilities that may affect the turbine lifetime and operating range. From a practical perspective, the most common triggers for refurbishment include declining turbine efficiency, recurrent failures, increased start-stop cycles, excessive vibration or pressure pulsations, cavitation damage, difficulties in operating at partial load or deep part load, outdated control systems, high O&M costs, environmental compliance requirements and the need to improve biodiversity protection. REVHYDRO aims to support refurbishment solutions that improve efficiency, flexibility and sustainability while avoiding major modifications to the hydraulic system whenever possible.

The data typically available depend on the level of digitalisation of the hydropower plant. In most cases, useful information can be collected from SCADA systems, maintenance logs, inspection reports, vibration monitoring systems, operational alarms, downtime records, efficiency tests, repair history and O&M cost records. For turbine condition and fatigue assessment, the most relevant data include operating hours, number of start-stop cycles, load profiles, head and flow conditions, pressure fluctuations, vibration levels, strain measurements where available, cavitation observations, inspection findings and historical failure records. In the REVHYDRO testing methodology, model turbine assessment includes efficiency measurements, pressure fluctuations, velocity measurements and dynamic strain measurements, which are used to validate numerical models and evaluate fatigue behaviour. For circular economy and sustainability assessment, additional data are needed: quantities of materials used, reused or replaced; energy consumption during refurbishment; transport distances; waste streams; emissions; CAPEX and OPEX; maintenance frequency; lifetime extension; and environmental or biodiversity-related information. These data support LCA, LCI and LCC studies, which are part of REVHYDRO’s circular refurbishment methodology.

A useful comparison should include technical, economic, environmental and circularity indicators. Technical indicators may include turbine efficiency at BEP, PL and DPL, operating range, vibration levels, pressure pulsations, cavitation behaviour, fatigue reduction, start-stop flexibility, unplanned downtime and lifetime extension. Economic indicators should include CAPEX, OPEX, O&M cost per MWh, lifecycle cost, payback period, avoided repair costs, reduced outage duration and additional value from increased flexibility or system services. REVHYDRO expects that circular refurbishment methods and polymer add-ons can reduce refurbishment costs and improve efficiency by mitigating harmful off-design flow structures. Circular and environmental indicators should include virgin material use, reused or recycled material content, waste diverted from disposal, renewable energy used during refurbishment, CO₂ emissions avoided, water quality impact, biodiversity performance and improvement in the overall sustainability index. REVHYDRO also proposes the Circular Economy Integrated Indicator, CEII, as a benchmarking tool that considers virgin material use, renewable energy consumption and the duration of turbine operation between refurbishment cycles.

The main barriers are technical validation, risk perception and acceptance by plant owners. Hydropower assets are valuable and often operated for decades, so owners may be cautious about adopting novel technologies that have not yet been demonstrated over long service periods. REVHYDRO identifies this conservatism as an important implementation barrier for RFC and DFC systems, which are novel technologies not yet commonly used in hydraulic turbines. For polymer-based runner add-ons, the technical challenges include material durability, fatigue resistance, water absorption, adhesive compatibility, polymer-metal interface performance, underwater operating conditions, dynamic loading, long service life, inspection procedures and certification. REVHYDRO addresses these barriers through material and adhesive characterisation, testing under relevant hydraulic conditions and validation of the selected material and bonding system before industrial uptake. Other barriers include guarantees, insurance, standardisation, intellectual property, access to confidential turbine geometry, supplier data, proprietary measurements and lack of established testing methodologies for bonded assemblies in hydropower applications. This is why REVHYDRO also includes IP management, testing methodologies and eco-design guidance as part of its exploitation and sustainability approach.

Biodiversity protection should be considered from the earliest planning phase, not only at the permitting stage. This means that refurbishment studies should include an initial screening of fish species, migration periods, turbine intake risks, existing fish passage infrastructure, water quality constraints, sediment issues, legal requirements and expected environmental impacts. REVHYDRO proposes the I-Fish system, an intelligent behavioural fish barrier designed to guide fish away from turbine intakes and towards safe passage routes. The system combines a bubble curtain, an acoustic source and a strobe light source, which can be adjusted according to fish species, maturity and local environmental conditions. The project target is to redirect at least 95% of fish away from the turbine intake. Earlier integration can be achieved by including biodiversity experts, operators, local authorities and environmental stakeholders in the refurbishment concept phase; assessing fish passage alternatives before final technical design; aligning refurbishment with water quality and biodiversity requirements; and using monitoring data to evaluate the effectiveness of fish protection measures. REVHYDRO’s approach links turbine refurbishment, biodiversity protection and circular economy assessment into one integrated sustainability framework.

Engineers and technicians would benefit from practical, applied training that connects circular economy principles with day-to-day hydropower refurbishment decisions. Training should cover circular design, maintenance planning, material selection, repair versus replacement decisions, life-extension strategies, design for disassembly, waste prevention, reuse and recycling, LCA/LCI/LCC, CEII calculation, eco-design guidelines, digital monitoring and data collection for sustainability reporting. REVHYDRO foresees a circular economy training programme for engineers and technicians in the hydropower sector. The purpose is to build capacity, support practical implementation of circular economy principles and promote best practices across the sector. A useful training structure could include: introduction to circular economy in hydropower; practical indicators for circular refurbishment; case studies comparing conventional and circular refurbishment; LCA and LCC exercises; data collection templates; material and component circularity assessment; biodiversity and water quality integration; and use of digital tools for predictive maintenance and lifecycle impact assessment.

The most useful topics would be those that help operators, engineers, manufacturers, researchers and public stakeholders understand how REVHYDRO results can be applied in practice. Priority topics should include: First, off-design turbine operation and refurbishment needs, explaining BEP, PL, DPL, cavitation, rotating vortex rope, pressure pulsations, fatigue and start-stop cycles in accessible language. Second, RFC and DFC technologies, showing how runner flow control and draft tube flow control can reduce fatigue, improve flexibility and reduce refurbishment impact. REVHYDRO identifies RFC and DFC as key results for pressure pulsation mitigation, turbine lifetime enhancement and lower refurbishment cost. Third, circular refurbishment methodology, including LCA, LCI, LCC, CEII, material reuse, resource efficiency, lifecycle impact and eco-design. Fourth, I-Fish and biodiversity protection, explaining how behavioural fish barriers, AI-supported monitoring and the WellFish app can support fish passage and biodiversity objectives. Fifth, data confidentiality and open data, especially how partners and stakeholders can contribute useful operational insights while protecting sensitive industrial data. REVHYDRO’s data management approach distinguishes between public data and sensitive/confidential or IP-protected data, with sensitive data excluded from public repositories. Sixth, practical implementation barriers, including certification, guarantees, acceptance of new materials, operator concerns, risk management and stakeholder engagement.

REVHYDRO is a European-funded research and innovation project dedicated to efficient and eco-friendly hydropower refurbishment. It develops innovative flow and fish control technologies combined with a circular design approach to improve the performance, flexibility, resilience and sustainability of existing hydropower plants.

The main objective is to design and validate refurbishment solutions that can improve the efficiency, flexibility and sustainability of existing hydropower plants. The project focuses on flow control devices installed in the runner and draft tube, an intelligent fish barrier, and circular economy methodologies for lower environmental impact and better resource efficiency.

Many hydropower plants were designed decades ago for more stable operating conditions. Today, plants are increasingly required to support flexible electricity systems, integrate variable renewable energy sources and operate away from their original best efficiency point. Refurbishment can help existing assets remain reliable, efficient, environmentally compliant and economically viable without building entirely new infrastructure.

REVHYDRO is funded under Horizon Europe, within the Climate, Energy and Mobility programme. The project is linked to the topic focused on developing hydropower equipment for improved techno-economic efficiency and equipment resilience in refurbishment situations.

The project started on 1 October 2024 and is planned to run until 30 September 2028. During this period, the consortium will develop, test, validate and disseminate the project solutions and results.

The main beneficiaries include hydropower operators, asset managers, turbine manufacturers, maintenance teams, environmental and biodiversity experts, public authorities, policymakers, researchers, students and other organisations interested in sustainable hydropower refurbishment.

The consortium brings together universities, research organisations, technology providers, service companies and hydropower utilities. This multidisciplinary structure combines expertise in hydraulic engineering, fluid mechanics, material science, biodiversity protection, circular economy, LCA/LCC, dissemination and stakeholder engagement.

REVHYDRO addresses challenges linked to ageing hydropower equipment, operation away from the best efficiency point, pressure pulsations, rotating vortex rope phenomena, cavitation, fatigue, vibration, reduced flexibility, downtime and the need for better biodiversity protection and circular resource use.

Off-design operation refers to situations where a turbine operates outside the conditions for which it was originally designed. This can happen when a plant is used for flexible power generation, frequent start/stop cycles, partial load operation or operation under changing water levels and flow conditions.

The Best Efficiency Point is the operating condition at which the turbine reaches its highest efficiency. Operating far from this point can create unstable flows, pressure fluctuations and mechanical loads that may increase wear and reduce the lifetime of equipment.

PL means Part Load, when the turbine operates below its nominal or optimal load. DPL means Deep Part Load, a more severe low-load condition. Both are important because flexible electricity systems increasingly require hydropower plants to operate across a wider range of loads.

Pressure pulsations are unsteady pressure variations that can appear in the turbine and draft tube during off-design operation. If not controlled, they can increase vibration, noise, structural loading and fatigue, potentially limiting the safe operating range of the turbine.

Turbine fatigue refers to the gradual weakening of turbine components due to repeated mechanical loading over time. Frequent operation under challenging hydraulic conditions can increase fatigue and shorten equipment lifetime. REVHYDRO develops models and technologies to better understand, reduce and manage fatigue.

Yes. Refurbished hydropower plants can provide flexible, renewable electricity that helps balance variable wind and solar generation. By extending the lifetime and operating range of existing assets, refurbishment supports a more resilient and secure energy system.

Runner Flow Control is a refurbishment concept that uses polymer-based extensions or add-ons on the runner and/or distributor area to improve flow behaviour under challenging operating conditions. The aim is to reduce fatigue and extend the operational range without requiring a complete runner replacement.

Polymer-based extensions can be shaped for hydraulic performance and installed with limited modification of existing components. They are designed to provide a cost-effective way to improve turbine behaviour, reduce mechanical stress and avoid extensive refurbishment interventions where possible.

Draft Tube Flow Control is a system designed to mitigate pressure pulsations and unsteady flow phenomena in the draft tube of Francis turbines. It uses adjustable guide vane concepts and numerical optimisation to improve operational stability and reduce fatigue under part-load conditions.

RFC and DFC are expected to help turbines operate over a wider range of conditions with lower fatigue, improved reliability and enhanced flexibility. This can support lower refurbishment costs, reduced downtime and better integration of hydropower into modern electricity systems.

The project aims to develop solutions with minimal refurbishment impact. The intention is to improve performance and resilience without major changes to the hydraulic system or full replacement of critical components, although the final applicability will depend on each plant's technical conditions.

The project combines high-fidelity numerical modelling, CFD/FEA simulations, reduced-order models and experimental testing on Francis turbine models. Measurements such as efficiency, pressure, velocity and strain will be used to assess the effects of the proposed solutions.

I-Fish is an intelligent behavioural fish barrier designed to guide fish away from turbine intakes and towards safer passages. It combines adjustable stimuli such as bubble curtains, acoustic signals and strobe light with data-driven decision support.

I-Fish aims to reduce the risk of fish entering turbine intakes by adapting the barrier operation to fish species, size, maturity and local environmental conditions. By directing fish towards safer routes, it supports biodiversity conservation near hydropower facilities.

REVHYDRO targets the redirection of at least 95% of fish in the tested conditions. The system will be evaluated experimentally, with attention to both barrier effectiveness and fish welfare.

WellFish is the planned application and support tool connected to fish welfare and I-Fish optimisation. It is intended to help process data related to fish behaviour and welfare and support the optimisation of barrier operating parameters.

Artificial intelligence and machine learning are used to support optimisation and decision-making, for example in the design of flow control devices and in the analysis of fish behaviour and welfare data. The project does not rely on personal data for these technical optimisation activities.

Circular economy in hydropower refurbishment means extending the life of equipment, reducing virgin material use, reusing or refurbishing components where possible, reducing waste, selecting more sustainable materials and improving environmental and economic performance across the lifecycle.

The methodology is designed to support systematic, data-informed and circular maintenance and refurbishment decisions. It considers technical performance, lifecycle impacts, costs, resource use, equipment lifetime, waste reduction and value creation.

Life Cycle Assessment (LCA) evaluates environmental impacts across the lifecycle. Life Cycle Inventory (LCI) collects the data used in LCA, such as materials, energy and emissions. Life Cycle Costing (LCC) analyses costs across the lifecycle, including investment, operation, maintenance and end-of-life aspects.

CEII means Circular Economy Integrated Indicator. In REVHYDRO, it is intended as a benchmarking and decision-support indicator to evaluate circular economy performance in hydropower refurbishment, including aspects such as virgin material use, renewable energy use and the duration of operation between refurbishments.

REVHYDRO considers environmental, economic and social dimensions, including carbon emissions, resource use, water-related impacts, biodiversity, operational efficiency, cost, stakeholder value and contribution to relevant Sustainable Development Goals.

The project targets reductions in CO2 emissions and resource consumption through circular refurbishing methodologies, improved material use, reduced waste and technologies that support more efficient and reliable operation. The project also addresses biodiversity through the I-Fish solution.

REVHYDRO aims to contribute to lower OPEX, lower CAPEX for refurbishment processes, reduced downtime, improved equipment lifetime and better operational flexibility. These benefits are assessed alongside environmental and social aspects.

REVHYDRO is particularly relevant to SDG 7 on affordable and clean energy, SDG 9 on industry, innovation and infrastructure, SDG 12 on responsible consumption and production, SDG 13 on climate action, and SDG 6 on sustainable water management. Biodiversity and ecosystem considerations are also embedded through the I-Fish work.

Yes. The project plans to develop guidance related to eco-design for hydropower turbines, including considerations such as material selection, design for disassembly, lifecycle impacts and end-of-life aspects.

Practical data from operators, maintenance teams, technology providers and other stakeholders helps the project understand real refurbishment challenges, validate circular economy approaches, identify useful indicators and improve the relevance of project results for the hydropower sector.

Useful data may include turbine type, installed capacity, operating regime, refurbishment scope, downtime, CAPEX/OPEX, O&M practices, failure modes, vibration or pressure data, production data, material flows, waste streams, environmental permitting aspects and sustainability indicators. Data can be provided at an aggregated or anonymised level where needed.

Yes. The forum and stakeholder engagement activities can use aggregated, anonymised or general examples. Contributors should not publish sensitive commercial, technical, operational or intellectual property information unless they have the right and explicit authorisation to do so.

The project follows data management principles that distinguish public data from sensitive or confidential data. Public research data may be made available through open repositories where appropriate, while sensitive data is protected and not published openly.

Yes. Operators are encouraged to share relevant experiences, especially if they relate to refurbishment, O&M challenges, lifetime extension, material reuse, circular economy, biodiversity, digitalisation or sustainability indicators. Case studies may be shared in a structured, anonymised format if needed.

Please keep the discussion at a general or aggregated level. For example, instead of disclosing supplier-specific prices, contributors may discuss cost categories, decision criteria, payback considerations or lessons learned from refurbishment planning.

You can follow updates through the REVHYDRO website, newsletter, social media channels, factsheets, webinars, events and scientific publications. The website also includes contact information for further questions.

REVHYDRO plans workshops, webinars, open seminars, stakeholder meetings, mentoring activities and dissemination events. These activities are designed to share project progress, collect stakeholder input and support the uptake of sustainable hydropower refurbishment solutions.

The forum is open to stakeholders interested in hydropower refurbishment, renewable energy, circular economy, biodiversity, digitalisation, maintenance and sustainability. This includes operators, technical experts, researchers, students, policymakers, NGOs and representatives of relevant industries.

Questions are welcome on technical challenges, refurbishment methods, circular economy indicators, LCA/LCC, fish protection, digital monitoring, O&M workflows, training needs, policy barriers, standards, stakeholder engagement and future webinar topics.

Yes. Students and early-career researchers are encouraged to use the forum to learn, ask clear questions, follow project resources and engage with topics such as hydropower flexibility, CFD/FEA, circular economy, LCA/LCC and biodiversity protection.

Resources are expected to be shared through the REVHYDRO website, including factsheets, scientific publications, updates, webinars, events and useful links. Public research outputs may also be shared through open-access platforms where appropriate.

For general information, use the contact details provided on the REVHYDRO website. For forum participation, events or stakeholder engagement, please use the official project communication channels and avoid sharing sensitive data in public comments.

The project develops solutions with replication potential, but applicability depends on each plant's turbine type, geometry, operating regime, environmental constraints, refurbishment window, technical condition and economic context. The forum can help collect questions and examples to better understand replication needs.

The project focuses on existing hydropower refurbishment and develops technologies for relevant turbine systems, especially Francis turbine contexts used for validation. Lessons on circular economy, maintenance, sustainability and stakeholder engagement may also be useful for a wider range of hydropower assets.

Policymakers can use project outputs to understand how refurbishment, circular economy, biodiversity protection and digitalisation can support energy security, climate objectives, resource efficiency and the long-term sustainability of hydropower assets.

Hydropower operators, manufacturers and service providers can use the results to inform refurbishment planning, maintenance strategies, circular design decisions, lifecycle costing, sustainability reporting and future investments in technologies that extend asset life and reduce environmental impacts.

Please post the question in the most relevant forum category and include enough context to make the discussion useful: turbine type if public, operational condition, type of challenge, type of data available and whether the example is general, anonymised or sensitive. Do not share confidential drawings, measurements or commercial data in the public forum.