Description
The Paimpol-Bréhat pilot project aimed to pave the way for the pre-commercialisation of tidal farms from 2017. At the initial stage of the project a prototype version of the 0.5 MW 16m diameter OpenHydro device was installed and tested in 2011. Following this successful prototype testing, in 2015 OpenHydro completed the design and manufacture of two turbines for a grid-connected demonstration project (2 x 2MW turbines, 16m diameter).
The first turbine was installed on the 20th of January 2016 and the second turbine was installed on the 29th of May 2016. The turbines were installed using a dedicated barge designed by DCNS/OpenHydro. Once the barge was stabilized, the turbines were lowered to the seabed using an innovative winch system equipped with hydraulic motors.
During 2016 OpenHydro developed and built a power conversion system as part of the turbine control centre (TCC), housed in a subsea pressure vessel enclosure and mounted on the subsea base. The TCC is a power electronics apparatus which performs the dual functions of controlling the turbine to achieve optimum power output and converting the electrical output of the turbine to grid compliant power (however, these devices were never grid connected in the end).
In April 2019, testing with another tidal turbine began at this test site. The HQ-OCEAN tidal turbine designed by the French start-up HydroQuest and built by CMN was immersed to a depth of 35 m. By June 2019, this device had delivered its first kilowatt hour of electricity to the grid. The testing lasted until December 2021 upon which the device was retrieved from its place on the seabed.
OpenHydro released video footage of the installation of the first device: https://www.youtube.com/watch?v=Du7Jqscu3LE
Onshore Infrastructure: The substation that fed the electricity to the French grid is located close to the Arcouest Peninsula in Ploubazlanec.
Vessel Spread: Specifically designed catamaran barge (Triskell), a tug (Penfret) and a support boat.
Location
The project was located 16km off the coast of Brittany, France in water depths of 35m.
Project Progress
In January 2017 it was reported that the two turbines would need to be removed to replace a faulty part which prevented the system from operating correctly. It was discovered that corrosion of bolts and fasteners was the cause of the problem.
The first and second turbines were retrieved in April and July 2017 respectively for replacement of components that threatened the turbine’s resistance to corrosion. These turbines were never redeployed and the project was subsequently cancelled by EDF in 2018.
In April 2019 the HydroQuest turbine was installed. The HydroQuest turbine was then retrieved December 2021.
Key Environmental Issues
Key environmental issues include those relevant to other tidal stream developments such as:
- Noise impacts during construction and operation
- Disturbance to benthic habitats
- Potential for collision with turbine blades
Additionally, the recommendations of the Trégor-Goëlo SMVM sea development plan include:
- Importance of Maintaining Water Quality
- Ecological interest of the territory
- Risks associated with the evolution of the coastline
- The many dynamic activities and uses that exert strong pressure on environments and competition for limited space.
Papers, Reports, Research Studies
Environmental Monitoring: Paimpol-Bréhat Tidal Demonstration Project
| Phase | Stressor & Receptor | Design and Methods | Results |
|---|---|---|---|
| Baseline | Invertebrates | Drop down video monitoring at the project site and along the unburied section of the cable route A total of 57 videos profiles were recorded using a HD video camera (Sony HD CX6) mounted on a weighted frame equipped with two lasers, a light and an altimeter. The suspended video frame was successively dropped and lifted for a few seconds, while the research vessel was in neutral but still moving with the current. The video profiles were thus positioned following a random sampling design. Instantaneous high resolution pictures were taken each time the frame hit the bottom (representing a total of 1455 snapshots) allowing the identification of benthic epifauna. Some megafauna taxa were also recorded when the video frame is flying about 1 m above the bottom. | Completed
During the 2012 survey (i.e. before the deployment of pilot turbines and the installation of the cable), 105 taxa were identified, including 91 invertebrate taxa and 14 benthic flora taxa. The benthic community was dominated by hard-bottom epifauna characteristic for the circalittoral zone, including ascidians, bryozoans, cnidarians, sponges and encrusting algae. Conspicuous mats of unidentified yellow and red social ascidians were present on most of the video profiles. Several identified species were of ecological interest, either because they were abundant at the tidal site while being considered to be rare in this region (e.g., the bryozoans Flustra foliacea, the cnidarians Sagartia elegans, Sertularia argentea and Tubulariidae sp.), or because they play important ecological roles as ‘engineer species’ (e.g. Laminaria macroalgae). |
| Baseline | Birds, Marine Mammals | Marine mammal and bird surveys. Analysis of the initial state of the site and its environment. | Completed No direct impact on fish fauna, cetaceans or avifauna other than disturbance during installation operations was found. However, noise emissions from the boats and winches used could have an indirect disturbance to fish and cetaceans that may result in displacement during this period. The impact consists of a disturbance of the species. It is temporary, direct and indirect in scope, negligible to low and reversible at the end of operations. |
| Baseline | Human Dimensions | Survey of vessel traffic. Analysis of the initial state of the site and its environment. | Completed The vessels present during the installation of the tripod and tidal turbine will train an increase in noise. This temporary impact (a few days in total) will be very limited geographically and comparable to the impacts caused by commercial vessels. |
| Baseline | Invertebrates | Benthic fauna assessment. Analysis of impacts to benthic fauna. | Completed The impact on the benthos is related to the crushing of the bottom under the feet of the tripod. Since the rate of recovery varies greatly (10 to 80% of the surfaces), this impact can be considered negligible. The total surface area of the legs of the HQ-OCEAN tripod is 43.6m2 i.e. approximately 0.001% of the total area of the concession. The impacts of turbulence, due to wake effects, on the seabed will be equivalent to those of the tidal turbines tested by EDF (very similar turbine dimensions), i.e. not very significant. In conclusion, the impact on benthos remains non-significant. |
| Post-Installation Monitoring | Collision Fish |
Assessment of collision risk between fish and turbines. Desk based study. | Completed Fish have the ability to detect "obstacles" such as the presence of predators. Frequenting areas of high hydrodynamics, the species present in the Horaine have by definition swimming capacities, and therefore high avoidance reactions. Therefore, a low risk of collision with the machine can be expected. This risk is also significantly mitigated by the low rotational speed of the turbines: about 4 to 12 revolutions per minute maximum for a current of 3 m/s. |
| Post-Installation Monitoring | Habitat Change Invertebrates |
Monitoring of the artificial reef effect of the cable and concrete mattress cable protection Monitoring will be carried out using drop down video at least once a year during the operational period of the turbines. | Preliminary monitoring complete. Preliminary results showed that benthic colonisation is mainly composed with cirripeds, hydrozoans and ascidians. At least 2 introduced species (the ascidian Styela clava and the gastropod Crepidula fornicata) occur on the cable protection structures with significant abundances. Regarding the benthic colonisation on cable-stabilizing concrete mattresses, preliminary results showed that very few species have fixed on the structures after 6 months. However, a few individuals of young C. fornicata are already present. A large crustacean (young individual of Cancer pagurus) has been observed on one of the 2 investigated mattresses, suggesting that such artificial structure may act as potential new habitat for large vagile benthic fauna. |
| Post-Installation Monitoring | Noise Marine Mammals |
Acoustic study carried out by EDF on OpenHydro tidal turbines to obtain the noise impact of the turbine. Acoustic range and current measurements. | Completed The acoustic range was measured between about 500 m (2011, tide coef 90) and about 1200 m (2014, coeff. Tide 72 to 92). The noise radiated by the machine at 1 m depends on the frequency ranges (the emitted noise extending into the in the range of 20 to 4000 Hz approximately). The min/max intensities (at 1 m) estimated respectively by Altran (2011) and FEM (2014) are as follows (in dB): 90 (at 2750 Hz), 134 (at 20 Hz), 118 (at 40 Hz), 152 (at 128 Hz). The noise impact is "discontinuous" since it is linked to the rotation of the turbines, which only starts at current speeds above 0.8 m/s (i.e. about 70% of the time). |
| Post-Installation Monitoring | EMF Invertebrates |
Electromagnetic field effects on benthic fauna. Study on the electromagnetic field effects of the power cable on benthic fauna for OpenHydro turbines. | Completed In the context of the EDF project (connection of 4 tidal turbines) it was concluded that there was a negligible effect (40μTesla at 1m (i.e. the same level as the Earth's magnetic field, which is 47 μT), and 20μT at 2m. By way of comparison, this corresponds to levels 1000 times lower than the limit set for the exposure of the general public (40 mT – source International Commission on Non-Ionizing Radiation Protection www.icnirp.org). The connection of the HQ-OCEAN tidal turbine is not likely to result in an effect greater than these values. These elements allow us to conclude that there is no significant impact of the operation of tidal turbines on the composition or distribution of the benthic fauna (fixed or sessile) present on the seabed. |