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UCL Home  /  Geography  /  Blog  /  Blog Entries  /  Bladdered fish mastered?

Bladdered fish mastered?

Posted by ucfaam0 at Nov 01, 2013 09:30 AM |

Investigating fish passage through the VETT hydropower system: UCL Geography industry collaboration

Guest post by Jennifer Gomez Molina, VerdErg Renewable Energy Ltd

Renewable Energy is big business nowadays. With the UK legally committed to the 2009 Renewable Energy Directive target to achieve 15% of its energy consumption from renewable sources by 2020, there is a major drive to get non-fossil fuel power sources up and running. In addition to addressing energy security and climate change, it is important to ensure that their installation and operation is environmentally considerate. For hydropower, concern has been raised about the increased hydrodynamic activity in aquatic environments and the consequent impacts on inter-linking ecosystems. Prime concerns are the impact on fish passage through these systems and the impact of these renewable energy devices on fish migration. There are various initiatives by environmental stakeholders and conservation groups to promote fish migration by decommissioning weirs but these weirs are ideal locations for hydropower generation. Can we find a balance between conservation and generating economic green energy?

I joined UCL in 2011 during my sabbatical from industry to do a Masters in Aquatic Science. Working in hydropower R&D, I wanted to advance my skills in aquatic ecosystems, environmental assessment techniques and conservation which my employer VerdErg Renewable Energy Ltd actively supported by funding my postgraduate degree and giving me the opportunity to collaborate with them for my thesis. Using VerdErg’s Venturi-Enhanced Turbine Technology (VETT) as a case study, we developed a MATLAB model with programmed safe hydrodynamic pressure boundaries from literature to determine specific design configurations and hydrodynamic conditions that would be safe for juvenile fish passage. VETT is designed to amplify low head hydropower sources by as much as five times so a conventional small, high speed turbine and generating equipment can be installed economically. 80% of the flow is passed through a primary circuit and venturi, creating region of low static pressure which draws the remaining flow via a turbine at an amplified head drop. The turbine, which takes 20% of the flow, will always be screened. The research outcomes proved invaluable and gave hope to the fact that hydropower can accommodate the conservation needs of vulnerable species and promote fish survival.

VerdErg’s Venturi-Enhanced Turbine Technology (VETT)

Schematic of VerdErg’s Venturi-Enhanced Turbine Technology (VETT)

After a month off to visit my family in Colombia (epic R&R required post thesis submission), it was back to work for me. The outcome of my research was inspiring, the next step was to acquire hard evidence; we all know “the proof is in the pudding”. VerdErg gave me the task to create and manage a testing programme to test live fish through a full scale instrumented prototype and determine their survivability with special focus given to juvenile fish due to their vulnerability to extreme hydrodynamic conditions in hydropower systems. The research for my thesis enabled me to identify key environmental and engineering test parameters such as which fish species to assess and under what operating conditions. In addition, my literature review identified the key concerns for fish migration and hydropower enabling me to liaise with the Environment Agency about how these could be addressed through this work.

In May 2013, we conducted the live trials in collaboration with Vis Advies BV at their facility in Nieuwegein, The Netherlands. The testing programme focussed on the hydrodynamic conditions that fish would experience when passing through the VETT’s primary circuit and venturi. This essentially would replicate what was modelled in the MATLAB model.

Jennifer Gomez Molina during installation of the VETT systemConducting live trials of the VETT system

Jennifer Gomez Molina during installation of the VETT system (left), and conducting live trials (right)

In total, 827 fish were tested comprising of European eel, Atlantic salmon, Rainbow trout and Round goby. Using the “forced exposure method” developed by Vis et al., 2011, these fish were tested at 1.0m, 1.5m and 2.0m head drop with a maximum flow rate of 450 l/s. Independent Third Party Verification was conducted by Dr Billy Sinclair from at University of Cumbria which was funded by the Technology Strategy Board Innovation Voucher scheme.

Jennifer testing live fish

Jennifer conducting weight and length measurements of test and control fish to determine their survivability through the full scale instrumented VETT prototype

No immediate or latent mortality or internal or external injuries from passage were observed for all test scenarios, rating the VETT model a maximum score of 1 with classification “Outstanding”. As the VETT is scalable, these findings can be extrapolated to tidal and river sites with the same hydrodynamic profiles.

A smolt in the culvert trying to swim upstream after passing through the venturi

A smolt in the culvert trying to swim upstream after passing through the venturi, demonstrating that fish can survive passage through the VETT system

These research outcomes inform key concerns with fish migration especially of salmonids and eels and have relevance to the efforts to restore their populations. In addition, they support the nation’s green energy goals to ensure renewable energy is environmentally considerate. VerdErg hopes to follow up this milestone achievement with a long term fish testing programme as may be required to address specific future project issues. You can find out more about the Venturi-Enhanced Turbine Technology and this project on VerdErg’s website and YouTube channel.

I am grateful for the lessons learnt from my taught courses at UCL which enabled me to apply my acquired knowledge to real life innovative work. For me now, it is back to saving the world, one VETT at a time.


Jennifer Gomez Molina works as an Environmental Analyst for VerdErg Renewable Energy. She completed the UCL Geography MSc Aquatic Science course in 2012 and continues to have links with the department.