The Scottish tidal energy developer installed the first two Nova Innovation 100kW (M100) turbines in Bluemull Sound, Shetland in 2016, creating the world’s first offshore tidal array. A third turbine was added in 2017. The M100 device comprises a cylindrical nacelle unit, rotor attached to a steel frame gravity base foundation (therefore requiring no seabed drilling or additional site works). The negatively-buoyant nacelle is securely connected to the base by means of a latching system. The turbine has a rotor diameter of 9 m and a hub height of 9 m, making the total height 13.5 m from the bottom of feet to the tip of the blades. The turbines n the Shetland Tidal Array are installed in water depths of between 30 and 40 m, so clearance is always at least 15 m below lowest astronomical tide. As a result the are no navigational restrictions around the array or requirements for surface markers on. The footprint of each device is 13.5 x 12.2 m, and the weight in water is 80 tonnes.
Each turbine has a separate 1.2 km export cable which also contain fibre-optic cables for data and communications. The three cables come ashore at Cullivoe Pier, where onshore infrastructure receives information on operation and performance of the turbines and a small sub-station converts and supplies the electricity into the Shetland grid. In 2018 Nova Innovation also installed a series of Tesla lithium ion batteries and associated infrastructure at Cullivoe, enabling energy storage. The Shetland Tidal Array is now supplying baseload tidal power to the Shetland grid.
The next phase of the Shetland Tidal Array involves the addition of three further 100 kW turbines in 2020. In addition, a subsea hub and inter-array cabling will be used in the expanded array to remove the need for a dedicated export cable for each turbine.
The small size of Nova’s devices enables local vessels to be used for deployment, operations and maintenance and facilitated the development of local supply chain. To date the project has been delivered with 20 % content from the Northern Isles, over 80% from Scotland and 100% from within the European Union.
Bluemull Sound, Shetland in water depth between 30 and 40 m.
A Marine Licence was issued under the Marine (Scotland) Act 2010 by Marine Scotland for the extension to the Bluemull Sound site on 13 April 2018 (Licence no. 06642/18/0).
The marine licence document and other information can be found at the following link: http://www.gov.scot/Topics/marine/Licensing/marine/scoping/nova
After successful deployment and operation of the Shetland Tidal Array, in May 2017, secured around £190,000 in capital support to build and operate an energy storage solution for the Shetland Tidal Array. Tesla lithium ion batteries and associated infrastructure were installed at Cullivoe Pier in 2018 and the array is now suppling baseload power to the Shetland grid and contributing to grid stability.
The key aim of the project was to demonstrate the economic and technical benefit of Nova Innovation’s Tidal Energy Storage System (TESS) to expand and overcome grid constraints.
Nova Innovation is the lead partner in a €20.2 million flagship Horizon 2020 project, Enabling Future Arrays in Tidal (EnFAIT). The EnFAIT project began in July 2017 and will run until June 2022.
The EnFAIT project will expand the Shetland Tidal Array to six turbines with a total rated capacity of 600kW, and demonstrate that high array reliability and availability can be achieved using best practice maintenance regimes. The layout of the turbines will be adjusted to enable array interactions and optimisation to be studied for the very first time at an operational tidal energy site.
In May 2019 it was announced that EnFAIT has reduced the cost of tidal energy by 15 % and grown its supply chain from 4 to 14 countries. In May 2019 Nova Innovation was awarded €5 million funding for another Horizon 2020 project, ELEMENT, which will incorporate Artificial Intelligence technology to improve tidal turbine performance. The project will deliver an adaptive control system that improves turbine performance, decreasing the lifetime cost of energy by 17% and driving the tidal energy sector to commercialisation. The control technology will be demonstrated on the Nova M100 turbine in the Shetland Tidal Array.
Key Environmental Issues
The key environmental issues identified were the potential for impacts on qualifying features of Yell Sound Coast Special Area of Conservation and Hermaness, Saxa Vord and Valla Field Special Protected Area (SPA). This included possible disturbance as well as collision risk. Marine Scotland carried out a revised Appropriate Assessment (AA), required under Regulation 48 of the Conservation (Natural Habitats, &c.) Regulations 1994, for the project in 2018 in support of their determination process for the Marine Licence. Nova Innovation also produced an Environmental Assessment Report (EAR) for the project, since a statutory Environmental Impact Assessment was not required. The EAR and AA included updated collision risk assessments for the proposed six-turbine array and included an assessment for the proposed Special Protected Area (pSPA). They also considered the proximity of the development site to the Yell Sound Coast SAC and the foraging range of harbour seals, as well as the risk of collision between diving birds and operational turbines. Species specifically considered to be potentially significantly impacted by the proposal and requiring more detailed assessment included:
Yell Sound Coast SAC
- Harbour seal (Phoca vitulina).
Following this further assessment it was concluded that there would be no adverse effect on the harbour seal feature of the Yell Sound Coast SAC and therefore no adverse effects on site integrity.
Hermaness, Saxa Vord and Valla Field SPA
- Gannet (Morus bassana);
- Puffin (Fratercula arctica);
- Red-throated diver (Gavia Stellata);
- Guillemot (Uria aalge); and
- Shag (Phalacrocorax aristotelis).
Following further assessment it was concluded that there would be no significant effects on the above qualifying species of the SPA and therefore no adverse effect on site integrity.
Bluemull and Colgrave Sound pSPA
- Red-throated diver (Gavia stellata).
Following further assessment it was concluded that there would be no significant effects on the red throated diver feature of the pSPA and therefore no adverse effect on site integrity.
The conclusions of the EAR and AA were dependent on a program of monitoring to understand collision risk and collision risk factors for diving birds and marine mammals.