Scotland: Westray South Tidal Array – Orkney

In April 2014 DP Energy acquired the development rights to the Westray South proposal. The project was awarded a 200MW Agreement for Lease (AfL) from The Crown Estate (TCE) in March 2010. A specific development company for the site, Westray South Tidal Development Ltd (WST)

Project Description

The site is located within the Westray Firth approximately 24km to the north of Kirkwall, the nearest sizeable port. The Crown Estate Agreement for Lease area covers approximately 13km2 (excluding grid connection corridor) within which the proposed development would occupy a smaller area; work on identifying this and related stakeholder consultation is ongoing.

The project development scope for consenting purposes being progressed encompasses the offshore works (tidal generators, array cabling and export cable to shore) and export cable landfall near the village of Tingwall. Development of the onshore substation to which the project will connect and wider grid infrastructure lies outwith the scope of the project.

At present the electricity network on Orkney and beyond is not able to accommodate projects of this scale and options for development of new grid connection infrastructure are being investigated.


In order to inform the environmental and navigational safety studies a Scoping Report and Preliminary Hazard Analysis were submitted for consultation in 2011. A scoping opinion in response to these was received from Marine Scotland in December 2011 and this, along with subsequent discussions, has guided the environmental and technical assessments which have been carried out thus far.


An Environmental Statement (ES) and Navigational Risk Assessment (NRA) will be submitted at the time an application for consent is lodged. These documents will describe the project and present an assessment of the likely significant effects which may result from it, including any proposed mitigation measures. Further public consultation will be undertaken prior to lodging a formal consent application.

At this stage in order to inform the preparation of the ES and NRA consultation has been undertaken to ensure that the scope and methods utilised for baseline studies will enable a robust Environmental Impact Assessment to be undertaken.


Ecological surveys were initiated in January 2012 in order to provide baseline data relating to habitats and species which use the proposed development area. The area of survey varies depending on the survey ‘target’ species or habitat, but in general the zone of interest for development and a buffer around this is covered. A key aim of the surveys is to ascertain if there are any species and/or habitats which may be sensitive to the construction, operation and maintenance of the tidal array and associated infrastructure. Although survey work for some species covers all seasons, particular attention has been given to breeding periods (typically April to July) and specifically when seals are pupping (July for common seal, late autumn for grey seal).

Detailed geophysical surveys with additional ROV seabed video footage have been collected and analysed. The AfL area consists largely of exposed bedrock (Devonian sandstone), with thin patchy distribution of sediment cover. There are few pronounced features except in the north where depths of up to 54m are reached. Areas of highest resource generally correlate with bedrock exposure with significantly fewer seabed features found in these areas.

Geophysical data and ROV footage has confirmed a generally even seabed which would suit a range of tidal device options. Ecologically conditions appear comparable to those at similar depths and current velocities elsewhere around Orkney and are not considered to be particularly sensitive.

A resource assessment of the site has been undertaken utilising seven seabed mounted acoustic doppler current profilers (ADCP), and a resource model developed and calibrated based on this measured data. The model enables predictions of resource for specific areas. Mean spring peak tidal velocities have been determined to be in the order of 3.5m/s (msp).