Description
Mocean Energy concluded the Mocean Wave Energy Converter (WEC): Blue Horizon project to complete the detailed design, build, and testing of a sea-going prototype Mocean WEC, funded by Wave Energy Scotland (WES) through its Novel WEC Programme.
The primary purpose of testing has been to gather performance data and learnings from deployment of the device in order to inform further development of Mocean’s wave energy converter designs. In addition to the power performance of the WEC, the test programme assessed the behaviour and practicalities of the mooring system and the electrical connection.
The Mocean WEC is a hinged raft that differs radically in shape from the classic symmetric twin-pontoon configuration. During the course of the project, Mocean constructed and operated a prototype 10kW WEC, named “Blue X”, with dimensions 19.3m (L) x 4.6m (W) × 7.6m (H). A notable characteristic of the prototype is that is designed to operate without connection to an umbilical. This design requirement was put in place to facilitate the testing at the performance test site. The rotation of the aft hull with respect to the forward hull drives a gearbox and then a generator. Power from the generator is then conditioned and used onboard the WEC to power local system. Power beyond that needed to power on-board systems is stored in 30 kWh of batteries. Once the batteries are fully charged, excess power is dissipated through an onboard dump resistor.
The mooring system was made of two identical mooring lines, each line consisting of an anchor clump weight then heavy ground chain, lighter riser chain followed by a 3t subsea buoy and connected to each other with further light chain and polyester line. This system allowed 360-degree yaw of the device around the swivel allowing it to self-orientate and maximising energy capture.
Location
The device was installed at EMEC Scapa Flow Non Grid-Connected Wave Test Site, to the south of Kirkwall, Orkney Island, United Kingdom.
Licensing Information
The European Marine Energy Centre (EMEC) has been accredited with the UK Accreditation Service (ISO 17025) since 2005. EMEC has been granted the consents required to install an agreed ‘envelope’ of device types at these sites.
For each developer wishing to install at EMEC’s test sites the consenting process requires the developer to produce the following documentation to accompany their Marine Licence applications, alongside the relevant site-wide environmental report and navigational risk assessment:
- Project Information Summary
- Project-specific Environmental Monitoring Programme (PEMP)
- Project-specific Navigational Risk Assessment (NRA)
- Third-party Verification/Certificate (TPV/TPC)
- Decommissioning Programme (DP)
Blue X had an installed capacity of less than 1MW and was not connected to the grid, therefore no Section 36 consent was required or Environmental Impact Assessment. In addition, EMEC test site deployments require no terrestrial planning applications. No Licence to Disturb European Protected Species or Basking Shark was required for this project, therefore only a Marine Licence was necessary.
| Licence | Competent Authority | Reference | Date Issued | Expiry date |
| Marine Licence (Marine Scotland Act) | Marine Scotland | MS-00009295 | 29/04/2021 | 30/08/2021 |
| Marine Licence extension | Marine Scotland | MS-00009422 | 18/08/2021 | 30/12/202 |
Project Progress
The detailed design stage started in the January of 2019, and fabrication was completed in the spring of 2021 in Fife. The project had seen an approximate delay of 6 months due to Covid-19. Fabrication of Blue X was postponed which had a knock off effect on succeeding planned tasks and brought further delays due to replanning and resubmission of licences with revised timelines.
In detail, Blue X was constructed at Cowdenbeath and transported by road to Rosyth for final assembly and commissioning in April 2021. At Mocean’s Rosyth site, Mocean carried out the first lifts of the complete WEC. The wet commissioning and trim adjustment in the water by the addition of ballast was completed by May, before Blue X was transported by road and ferry to Kirkwall in Orkney. As built WEC mass and mass distribution was very close to design, resulting in minimal ad hoc ballast.
The WEC was transported as a whole unit on a low-loader trailer from Rosyth to Orkney via the Aberdeen freight ferry as part of the detailed route planning, which took into account dimension limits and road suitability.
It was then launched from Hatston Pier and towed to EMEC’s Scapa Flow scale test site to begin its test phase in mid-June. Blue X was installed at the test site over the course of two days; the first day was the mooring installation, and the second day was the tow and WEC hook up.
Following the installation at Scapa Flow, Blue X operated successfully for the 5-month testing period on site at Scapa Flow before recovery to the quayside in November 2021 after 154 days at sea. The WEC was briefly recovered to Copland’s Dock (Stromness, Orkney) for an electrical upgrade halfway through the 5-month testing program where operations as lifting, detachment and reattachment of WEC from moorings, and maintenance were further demonstrated and improved.
Key Environmental Issues
The seabed throughout the Scapa Flow test site is composed of flat muddy sand, with the identified biotope (loose lying mats of Phyllophora crispa on infralittoral muddy sediment) not listed on the UK Biodiversity Action Plan or the Scottish Biodiversity List.
The Scapa Flow test site is not located within any designated conservation areas, however, the site is located within a wider expanse of Orkney coastline and inshore habitats which represent, in some areas, Special Areas of Conservation (SACs) and Special Protection Areas (SPAs). The nearest protected sites are:
- Keelylang Hill and Swartabeck Burn site of special scientific interest (SSSI), 7.6 km north-northwest: moorlands which are important for density and diversity of the bird community including birds of prey and moorland breeding birds.
- Orkney Mainland Moors SPA, 7.6 km north-northwest: a site that supports populations of European importance of the Annex I species hen harrier, red-throated diver, and short-eared owl.
- Waulkmill SSSI, 7.6 km northwest: site which encompasses a wide range of nature conservation interests including a sandflat and well-vegetated shingle spit.
Key environmental areas that are requested by EMEC to be addressed in each developers environmental plans and the mitigations that were in place as part of the PEMP are presented below:
| Impact | Mitigation |
| Displacement due to noise (during installation, maintenance, operation and decommissioning of device)(particularly vessel noise) |
The Scottish Marine Wildlife Watching Code (SMWWC) was adhered to. EMEC monitored noise using static and drifting passive acoustic recorders as part of the SeaWave project. |
| Displacement due to physical presence of device | Aggregation study was undertaken by Universities of Exeter and Plymouth. |
| Physical harm caused by collision | The Scottish Marine Wildlife Watching Code (SMWWC) was adhered to. |
| Physical harm caused by entanglement in device moorings | Mooring lines were kept onsite for as short a period as possible. |
| Physical harm caused by noise |
The Scottish Marine Wildlife Watching Code (SMWWC) was adhered to. EMEC monitored noise using static and drifting passive acoustic recorders as part of the SeaWave project. |
| Introduction of non-native species (via vessel or equipment) | Local vessel and equipment was used, reducing the potential for introduction of NNS. Compliance with good practice measures. |