Researchers from Trinity College Dublin and University College Dublin have developed and field-tested a prototype system that enables fish migration through river barriers while generating renewable electricity. The design aims to provide a cost-effective alternative to full barrier removal, potentially reducing associated costs by 50–85%.
The system was tested using both artificial and live fish at a fish farm in Ireland. Results suggest it could help meet EU river restoration targets while also contributing to national renewable energy goals.
The research, led by Prof. Aonghus McNabola – formerly of Trinity’s School of Engineering and now at RMIT University, Australia – has been published in the peer-reviewed journal Energies.
Prof. McNabola said: “The recently adopted EU Nature Restoration law emphasises the urgent need to address the ecological impacts of river barriers, which fragment habitats and disrupt natural flows. However, efforts to remove barriers are often constrained by prohibitive costs, regulatory hurdles, and public opposition.”
“This presents a major problem, which we set out to solve as a team of Engineers and Scientists with the desire to create a win-win solution that benefits the environment and makes a significant financial saving. We will now work to further refine our prototype and are excited about the difference it could make.”
He added: “Sustainable hydropower is very important in the broader context of renewable energy strategies as it is relatively untapped and could, with development, provide essential grid flexibility amidst growing solar and wind contributions.”
Ireland has an estimated 73,000 river barriers. Removal costs range from €200,000 to €500,000 per structure. While removal often restores ecological function, it also eliminates opportunities for converting barriers into small hydropower installations, reducing potential contributions to Ireland’s target of 80% renewable electricity generation by 2030.
Patrick Morrissey, Martin Naughton Assistant Professor in Trinity’s School of Engineering, explained: “We wanted to design our river barrier modification system to serve the dual purposes of upstream and downstream fish lift over barriers, while also making it capable of generating electricity by using a fish-friendly pump-as-turbine unit.”
He added: “Under normal flows the unit generates electricity and during low flows it operates in pumping mode to enable safe fish passage.”
The system is intended to accommodate fish species protected under the EU Habitats Directive, including Atlantic salmon, European eel, and river lamprey.
Prof. Mary Kelly-Quinn of University College Dublin said: “Moving forward, we need to conduct more detailed analyses of the renewable energy potential and in-depth fish impact assessments to affirm the viability of the solution.”
“But with further refinements and formal certification this system could play a pivotal role in achieving the dual objectives of the EU Nature Restoration Regulation and the Climate Action Plan 2023, thereby contributing to a more sustainable and ecologically balanced future for the EU.”
The research was funded by Research Ireland through the National Challenge Fund under the 2050 Challenge Subscrew Hydro Project.
