Description
Platform for Ocean Energy (PLAT-O) is a submerged taut moored, buoyant, subsea reaction sub-system, which acts as a support structure for tidal turbines. When in operation, the platform positions the turbines in the optimum high flow, low wave region of the water column for the extraction of energy from the tidal stream. PLAT-O has been designed to maximize power capture while minimizing operational costs and operations and maintenance (O&M) requirements.
PLAT-O relies on the buoyancy of the installed structure acting against a taut mooring system. The interaction of these elements produces a stable platform capable of supporting two turbines in normal operating conditions. The platform also has the ability to comply with the tidal stream, current and waves in extreme conditions reducing the loads produced. Since the load is transferred to the seabed in a straight line via the mooring lines, which act in tension, the weight of all system components is easily optimised in comparison to traditional seabed mounted structures. In addition, the turbines can be positioned in the optimum position to balance the loading caused by wave action against the increased power available in the tidal flow with separation from the seabed boundary layer.
SME has been developing the PLAT-O concept since its inception in 2012. In order to achieve a step change in the cost of tidal energy SME has pursued the development of small generation installations with matching diminutive capital expenditure and O&M costs. SCHOTTEL Hydro has supplied SCHOTTEL Instream Turbines (SITs) for the PLAT-O project.
Location
The device was installed at European Marine Energy Centre (EMEC) tidal device test area in Fall of Warness, Orkney, UK.
This document details information specific to SMEs PLAT-O#1 device.
The proposed device will be installed at a minimum clearance to surface of 11m within EMEC’s Fall of Warness tidal test site. The location of the rock anchors will be in the northwest of the EMEC test site, connecting to EMEC Berth 7.
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.
Each developer deploying at EMEC is required to submit device-specific information to support amendment of these consents to allow installation of their device. This information includes a project summary and details on how the specific device details align with the EMEC environmental description and navigational risk assessment. The following licence applications have been submitted by SME:
- Marine Licence under Marine (Scotland) Act 2010, Part 4 Marine Licensing
- Licence to disturb marine species (EPS licence) under The Conservation (Natural Habitats) Regulations 1994
- Licence to disturb basking sharks (Cetorhinus maximus) under The Wildlife and Countryside Act 1981 and the Nature Conservation (Scotland) Act 2004 (W&CA)
Project Progress
Rock anchors were installed on site in May 2016 with the device planned for instalment in September 2016. However, following this preparation the PLAT-O#1 device was not installed at the Fall of Warness test site and there are no plans to deploy anything in its place at present.
SME has since progressed onto development of the PLAT-I tidal energy platform in Grand Passage, Nova Scotia, which was installed in September 2018 and began generating power in February 2019.
Key Environmental Issues
The Fall of Warness 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).
EMEC has produced a specific Environmental Appraisal (EA) for the Fall of Warness site which can be downloaded from here.
Potential disturbance to marine mammals and birds as a result of vessel activity during installation and during O&M procedures, installation of the rock anchors resulting in noise impacts and the potential for collision with marine mammals and birds are considered the key environmental issues for the Project.
Baseline Assessment: PLAT-O at EMEC
| Receptor | Study Description | Design and Methods | Results | Status |
|---|---|---|---|---|
| Marine Mammals | Potential impacts on marine mammals and basking as a result of support vessel activity, e.g. noise and physical presence | Desk based study | Installation of the anchors and PLAT-O#1 will be completed using a standard multi-cat work vessel 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 |
| Marine Mammals | Underwater noise from foundation / mooring installation methods (drilling activities) leading to disturbance or auditory injury | Desk based study and results from previous deployments | The drilling operation will be completed in a relatively short timescale (estimated to be two days). Due to the small scale nature of the works proposed and the timescales involved, no significant effects are expected from the installation of the rock anchors. SME’s proposed drilling operations are small in scale and will be undertaken from a standard workboat. It is not therefore proposed to implement a mitigation zone or use MMOs during installation. SME has also undertaken acoustic monitoring during the anchor installation at their deployment site in Yarmouth; the results of which will be provided when available. | Complete |
| Marine Mammals | Underwater noise from turbine operation leading to disturbance | Desk based study and results from previous deployments | No significant effects are expected to result from underwater noise produced by the operation of a single tidal turbine. | Complete |
| Marine Mammals | Entanglement in mooring lines or cables leading to injury or death | Desk based study | A study commissioned by Scottish Natural Heritage (SNH) concluded that moorings associated with marine renewable energy devices are unlikely to pose a major threat in terms of entanglement risk to cetaceans and basking sharks due to the size and mass of the moorings. However, there is a greater risk for baleen whales due to their large size and foraging habits (Benjamins et al. 2014). Taut mooring systems present the lowest relative risk to large cetaceans and basking sharks. The proposed mooring lines will always be taut except when being connected and disconnected with a vessel on site. | Complete |
| Marine Mammals | Presence of tidal device and associated infrastructure leading to barrier effects | Desk based study | The presence of a single device within the Fall of Warness test site is not expected to result in any significant barrier effects for marine mammals or basking sharks. | Complete |
| Fish | Electromagnetic field (EMF) effects. Diadromous fish, gadoids and elasmobranchs. | Desk based study | No significant effects | Complete |
| Birds, Seabirds | Potential impacts on marine birds (seaducks, divers) as a result of support vessel activity, e.g. noise and physical presence | Desk based study | Installation of the anchors and PLAT-O#1 will be completed using a standard multi-cat work vessel 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 |
| 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 |
Post-Installation Monitoring: PLAT-O at EMEC
| Stressor | Receptor | Study Description | Design and Methods | Results | Status |
|---|---|---|---|---|---|
| Collision | Marine Mammals | Determine collision events with marine mammals and basking sharks | Video cameras will be installed on PLAT-O#1 device. Full details of the cameras, data analysis and reporting will be agreed with SNH and approved by MS-LOT prior to commissioning of the device. | Cancelled | |
| Habitat Change | Fish | Measure the effect the device has with respect to habitat creation and fish aggregation | Video cameras will be installed on PLAT-O#1 device. Full details of the cameras, data analysis and reporting will be agreed with SNH and approved by MS-LOT prior to commissioning of the device. | Cancelled | |
| Collision | Birds, Seabirds | Determine collision events with marine birds | Video cameras will be installed on PLAT-O#1 device. Full details of the cameras, data analysis and reporting will be agreed with SNH and approved by MS-LOT prior to commissioning of the device. | Cancelled |