Description
Nautricity tested its second-generation tidal turbine CoRMaT, a 500 kW prototype device suitable for deployment in water depths of 8 – 500 m. This follows deployment and testing of a mooring system at the European Marine Energy Centre (EMEC) which included Nautricity's 'Hydrobuoy' – a hydro-dynamic subsurface float whose lift varies with tidal flow velocity, and deployment of the turbine onto the mooring assembly at EMEC and observation of its performance in wave and tidal environments, both in 2013.
The CorMaT turbine employs two closely-spaced contra-rotating rotors, which drive the rotor and rotating stator sections of an electrical generator. The first rotor has three blades rotating in a clockwise direction while the second rotor, located directly behind the first, has four blades rotating in an anti-clockwise direction. Buoyancy chambers at the front and rear sections of the nacelle are tuned to achieve neutral buoyancy. The turbine is connected to a tensioned mooring at a point in the water column where the flow velocity is greatest and surface wave action minimized.
Location
The device was installed at berth 3 at EMEC’s tidal device test facility at Fall of Warness, Orkney, UK. Tidal range: 3 m. Tidal speeds up to 3.7 m/s.
Licensing Information
The CoRMaT project has an installed capacity of less than 1 MW, therefore no Section 36 Consent was required. A Marine License was granted under the Marine (Scotland) Act 2010 by Marine Scotland (the licensing authority) on 22nd February 2017 (Licence no. 06260/17/0), which can be viewed here.
Project Progress
The system underwent testing at EMEC’s Shapinsay Sound test site during 2014. In 2015, Nautricity signed up to a grid-connected tidal test berth at EMEC’s Fall of Warness tidal test site.
Installation of mooring infrastructure began at the beginning of March 2017, and the CoRMaT device was deployed in April 2017. In March 2018, the device was retrieved for investigation and analysis of the turbine and its supporting systems, to assess the impact of extended exposure.
All remaining marine infrastructure was removed from the Fall of Warness by the end of 2019.
Key Environmental Issues
Baseline studies for the Fall of Warness test site were performed by EMEC and can be found here.
The site’s seabed ranges from eroding sub-littoral sandbanks in the east to smooth scoured bedrock ridges and platforms with occasional boulders towards the center of the site. Fall of Warness is not a protected area; however, there are protected sites in close proximity. These include:
- Faray and Holm of Faray SAC – protected for its grey seal populations.
- Sanday SAC – Protected for its harbor seal populations, intertidal mudflats and sandflats, inshore sublittoal rock and subtidal sandbanks.
- Muckle and Little Green Holm SSSI – Nationally important grey seal breeding colony (Around 3% of the national breeding population).
Baseline Assessment: Nautricity at EMEC
| Receptor | Study Description | Design and Methods | Results | Status |
|---|---|---|---|---|
| Fish | Introduction of marine non-native species (via vessels, devices or other equipment) | Desk based study | Vessels from within Scotland will be used therefore there is no potential for introduction of NNS via vessels. | Complete |
| Fish | Electromagnetic field (EMF) effects | Desk based study | No significant effects | Complete |
| Physical Environment | Potential for changes to hydrodynamics and physical processes | Desk based study | No important impacts of relevance to hydrodynamics or physical processes are expected from developments at Fall of Warness. | Complete |
| Marine Mammals | Potential impacts on marine mammals and basking sharks as a result of support vessel activity (e.g., noise and physical presence) | Desk based study | Installation of the CoRMaT 500 will be completed using standard multi-cat type vessels assisted by a RIB. Installation activities will be completed in a relatively short timescale. No significant effects on any sensitive species are expected from this low level of vessel activity. | Complete |
Post-Installation Monitoring: Nautricity at EMEC
| Stressor | Receptor | Study Description | Design and Methods | Results | Status |
|---|---|---|---|---|---|
| Collision | Marine Mammals | Monitoring physical interactions of cetaceans, basking sharks, and harbour and grey seals with device | Device fitted with a video camera for collision and near-miss detection. Position and speed of turbine and rotors respectively monitored via speed sensor, accelerometers and inclinometers. Noise signature of device defined by a hydrophone survey. | N/A | Incomplete |