Environmental monitoring of dam-integrated tidal power plant

Dam-integrated tidal power plant

The Oosterschelde storm surge barrier is a dam that contains 62 gates that can be closed when there is an increased risk of flooding. In 2015, the Dutch company Tocardo Tidal Power installed a 1.2MW tidal power plant in one of the gates comprising an array of 5 turbines. With global sea level rise, Tocardo foresees a market to integrate tidal turbines in future barriers to both protect and power densely populated delta’s worldwide. Over 400 suitable locations have been identified.

Partners and funding

Bluespring set-up a project to conduct a multi-disciplinary monitoring programme to assess impacts on both the biotic and abiotic ecosystem as well as effects on the reliability of the storm surge barrier itself. The collaborative research was undertaken by four research institutes: Wageningen Marine Research, University of Utrecht, TU-Delft, Deltares. Changes in flow patterns were monitored and modeled, the decrease in tidal amplitude, impact on sedimentation processes, the development of numbers of porpoises and seals in the Oosterschelde and collisions risk between these mammals and the turbines were all part of the study. Bluespring and Zeeuwse Milieu federatie (ZMf) were responsible for stakeholder engagement.

Challenges and approach

The main challenge for this project was to increase the public confidence in tidal energy, especially with the consenting and regulatory government bodies. Bluespring designed a project around quality of results and the quadruple helix model. The quadruple helix model recognises the main actors to advance innovation: science, policy, industry, and society. In keeping with this model, a greater public involvement can be achieved in the innovation processes.

Implementation

In order to overcome the main challenges, the following key actions were implemented:

Multidisciplinary collaboration around both the study of environmental effects and advancing technological innovation.

Nurturing conditions for data exchange and collaboration between knowledge institutions and government stakeholders, such as the Directorate-General for Public Works and Water Management (RWS), the province and environmental organizations.

Assurance of quality and independence of research by appointing Wageningen Marine Research (WMR) as scientific coordinator and peer reviewer of all contributions.

Involving and informing stakeholders by organizing regular communication activities and events in the region organized by community organisation ZMf

Develop a roadmap for costs reduction by bringing industrial partners together to share experiences from the operational Roompot 8 project and generate new ideas for the design of a second power plant in Roompot 10.

Increase energy production of Roompot 8 in close coordination between RWS and Deltares to remove (perceived) risks and uncertainties through extensive modelling and data analyse.

Download the main reports from here:

• Report: Monitoring Getijdenturbines Oosterscheldekering (NL)

• Position paper: Effects of the Eastern Scheldt Storm Surge Barrier and tidal energy turbines on harbor porpoise (Phocoena phocoena) and harbor seal (Phoca vitulina) movements (ENG)

• Article I: The performance of a weir-mounted tidal turbine: Field observations and theoretical modeling

• Article II: The performance of a weir-mounted tidal turbine: An experimental investigation

• Article III: Estimating the stability of bed protection of a weir-mounted tidal turbine

Conclusion

Erosion and sedimentation

Changes in the flow velocity patterns due to the existing and planned tidal power plants in two gates have no additional effect on the sandbanks in the Eastern Scheldt and do not appear to have significant effects on the erosion and sedimentation dynamics caused by 'sandhunger'

Seabed protection

Model simulations showed that turbulent velocity fluctuations were lower at most locations near the bed protection when the tidal turbines were installed, as they reduce the strength of turbulent eddies from the barrier sill. However, at other locations velocities and velocity fluctuations increased slightly. Therefore, the overall impact on bed protection was considered neutral for this pilot plant. In case of enlargement when several gates are filled with tidal turbines, the flow velocities at the non-turbine gates could change, which could modify the hydrodynamic loading on the bed protection at these gates.

Harbor porpoise and Seals

The small number of porpoises in the Eastern Scheldt most likely only pass the barrier around high tide. The water is then almost still so the turbines turn very slowly - if they have not already been lifted out of the water. The swept area of the turbines occupies 13% of the projected area of the opening of the gate. The turbines are only installed in one gate of 62. This makes the chance of porpoises coming into contact with the turbines virtually nil.

Common seals are also not expected to come into contact with the turbines because they can use different sensory systems to detect the moving turbine blades and they have enough space to swim under the turbines.

Seals and porpoises found dead in or just outside the Oosterschelde were subjected to pathological examination. Some animals were found to have died after a hard blow with an unknown object ('blunt trauma'). However, such trauma has also been found in animals found dead elsewhere in the Netherlands, in years before the turbines in the Eastern Scheldt storm surge barrier were put into operation.