The HiWave project was initiated to address the reliability and the high Levelised Cost of Energy (LCOE) of current Wave Energy Converters (WECs), which have so far been too large, heavy, and costly compared to their energy output. As part of the HiWave project consortium, CorPower Ocean has developed a WEC with a Power Take-Off (PTO) system, which incorporates a phase control module to make the device oscillate in resonance with incoming waves. This amplifies the motion and power capture, which facilitates the capture of a large amount of energy using a comparatively small device. The phase control module additionally enhances the device’s survivability by detuning the device in stormy conditions.
With funding from the Interreg North-West Europe Funding Ocean Renewable Energy through Strategic European Action (FORSEA) project, CorPower Ocean’s WEC was deployed at the European Marine Energy Centre’s (EMEC) Scapa Flow test site in January 2018. The deployment consists of the following technical elements:
- C3 WEC single surface floating point absorber, approximately 10m in length and 4.3 in diameter, with a power rating of 25kW;
- Buoyancy units supporting lazy wave cabling;
- Tension mooring system and anchor bracket attached to an existing gravity-based anchor; and
- Umbilical cable attached to a resistive load bank located on the EMEC test support buoy.
The device was installed at European Marine Energy Centre (EMEC) scale wave device test area in Scapa Flow, Orkney, UK.
Berth 1, Anchor Point A
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.
Licences held by EMEC include:
- Town and Country Planning (Scotland) Act 1997;
- Crown Estate Act 1971;
- Food & Environment Protection Act 1985 Part II Deposits in the sea (FEPA);
- Coast Protection Act 1949 (section 34) (CPA); and
- Electricity Act 1989 (section 36).
Each developer 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 C3 WEC has an installed capacity of less than 1MW, therefore no Section 36 consent was required. 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) Consent||Marine Scotland||06480/17/2||28 September 2017||30 March 2019|
CorPower Ocean's product development followed a structured five-stage verification process established as best practices for ocean technology by Wave Energy Scotland (WES) and the European Technology and Innovation Platform for Ocean Energy (ETIP Ocean), which involve a step-wise validation of survivability, performance, reliability, and economics.
Stage 1 (2012) and 2 (2013 – 2014) proceeded with the study of primary conversion (wave-body interactions) with numerical models calibrated by tank testing (small prototypes at 1:30 and 1:16 scale), followed by secondary conversion (PTO, mechanical to electricity) with numerical models calibrated by PTO rig testing (1:3 scale) . Fully integrated WEC models will continue to be tested in increasing scales up to array demonstration in Stage 5.
Implementation of the Stage 3 program (1:2 scale C3 WEC device) was guided by best practice support from EMEC, with experience from offshore power generation company Ibderola Engineering and EDP, the University of Edinburgh, and WavEC Offshore Renewables’ expertise in cost and performance modelling. The stage 3 demonstration was funded by WES, the Swedish Energy Agency, and InnoEnergy, with deployment at EMEC being supported by the Interreg North-West Europe Funding Ocean Renewable Energy through Strategic European Action (FORSEA) project.
The 1:2 scale C3 WEC device was successfully installed at the EMEC Scapa Flow site in January 2018. The contracted period for testing of the 1:2 scale device in Orkney was six months, including temporary recovery for onshore inspections and testing, with planned decommissioning upon completion of the test period.
In June 2018, EMEC issued a performance statement to CorPower following seven months dry testing of CorPower’s PTO system on the Hardware-In-Loop (HIL) rig. Onshore PTO testing forms part of the WES funded Hi-Drive project, which has completed its Stage 3.
CorPower completed the C3 testing during the summer of 2018 and aimed to incorporate understanding from wet testing into the development of their next-generation technology, as part of the Horizon 2020 funded project WaveBoost and full-scale HiWave-5 project. The performance testing of C3 device at EMEC was officially completed in October 2018.
Building on the Stage 3 program HiWave-3, the HIWave-5 Project consists of stage 4-5. It commenced in 2018 and with the aim of making wave energy a bankable technology, attracting renewable energy finance by introducing certified and warrantied WEC products to the market by the end of 2013-2024.
The two steps (4 and 5) consist of product verification and certification;
• Stage 4; Demonstration and prototype certification of a single full scale ’C4’ WEC, planned for 2018-2021. Taking the technology from Technology Readiness Level (TRL) 6 to TRL 7; and
• Stage 5; Demonstration and type certification of pilot array with three full scale ’C5’ WECs, planned for 2022-2023. Taking the technology from TRL 7 to TRL 8.
In addition, to certify the technology availability and performance, the HiWave-5 project aims at having a minimum of three operational devices demonstrated in a pilot farm delivering electricity to the grid.
Key Environmental Issues
Baseline studies for the Scapa Flow scale test site were performed by EMEC and can be found here.
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.
Further details can be found in EMEC’s Environmental Description specific to the Scapa Flow test site, which can be downloaded from here.
Potential environmental risks anticipated by CorPower in their project information summary  include:
- Loss of the C3 device due to hull breach and water ingress;
- Breakage of the mooring line; and
- Fluid leakage – the working fluid for the majority of the device is pressurised air, and the cooling system will use sea water and distilled water that does not contain refrigerant or other additives. The fluid used in device cylinders which will be in contact with the ocean environment is CompWay68, for which here is an MSDS available.
Raw wildlife observational data available at: https://www2.gov.scot/Topics/marine/science/MSInteractive/Themes/EMEC-W…;
A bottom-based foundation module was installed at the test berth which provides force reference from the WEC to the seabed and includes a mooring system with tidal adjustment function and tensioning capacity up to 60 tons. The installation operation included the subsea attachment of the foundation frame to a pre-laid gravity base, and the laying of an umbilical cable which controls the tidal adjustment unit.
As the site is not grid-connected, no export cable was present. The WEC was connected to a floating microgrid unit provided by EMEC, which was designed to allow the C3 device to behave as if grid-connected by providing a stable voltage and frequency reference, simulating the impedance of a typical grid connection, absorbing power from the device under test, and providing power to auxiliary systems.
The following vessels were used during construction:
|Name and type of vessel||Activity|
|Installation of bottom-based foundation module and device|
Papers, Reports, Research Studies
• Preliminary assessment of the conservation importance of benthic epifaunal species and habitats of the Pentland Firth and Orkney Islands in relation to the development of renewable energy schemes
• Scapa Flow Scale Site Environmental Description 2019
• Scapa Flow Scale Site: Environmental Description 2011
Baseline Assessment: CorPower Ocean at EMEC
|Receptor||Study Description||Design and Methods||Results||Status|
|Marine Mammals||Baseline acoustic characterisation.||Seabed-mounted hydrophone deployments.||Background noise levels were in line with that which could be expected for this type of shallow water site. Contributions over and above these conditions were then identified, with the major contribution being the natural sounds from wind/waves and precipitation. The major anthropogenic source was shipping noise from distant static and mobile sources. Local shipping traffic also contributed to the sound field, although this was only present for around 7% of the time. Other sounds identified included a thunderstorm, aircraft and various biological sources.||Completed|
|Physical Environment, Sediment Transport, Invertebrates||Initial site selection: determining biota and sediment particle size.||Grab sampling.||Moderately low energy site. “Sheltered Muddy Gravels” and “Subtidal Mixed Sediments”. |
The infaunal community was composed largely of deposit feeding species (mainly polychaetes and bivalve molluscs), with only a few crustaceans present. Two common species were Lumbrineris gracilis and Thyasira flexuosa which made up approximately 10 - 20% of individuals at all stations.
|Physical Environment||Initial site selection: Bathymetry commissioned by EMEC to Netsurvey Ltd.||Geophysical survey.||Water depths ranged from 15 to 30m across the site approximately 1 m deeper than charted depths.||Completed|
Post-Installation Monitoring: CorPower Ocean at EMEC
|Stressor||Receptor||Study Description||Design and Methods||Results||Status|
|Habitat Change||Invertebrates||Benthic grab analysis.||Survey samples sieved and analysed regarding species and abundance.||Study undertaken to assist in setting up the scale site, no further work deemed necessary unless additional or different types of infrastructure are propose.||Completed|
|Attraction, Avoidance||Birds, Marine Mammals||Wildlife observations.||Observations of birds and mammals by EMEC wildlife observers.||Raw data is publically available from the link below, however no report has been published.||Completed|