A major new research project – lead by the University of Dundee – has been launched with the aim of helping make offshore wave energy a sustainable proposition.
Sustainable offshore wave energy has the potential to make a real contribution towards the binding European Union commitment to source 20% of its electricity requirements from renewable sources by 2020. The vast wave energy resource along Europe’s western seaboard is unparalleled anywhere in the world. Consequently the EU has an opportunity to become international industry leaders in what is becoming a rapidly evolving and dynamic marketplace.
However, technical and economical hurdles associated with anchoring wave energy devices to the seabed threaten to stall and limit the impact that renewable wave energy has the potential to deliver.
Consequently the offshore renewable wave energy industry has collectively identified “mooring and anchoring systems” as a research topic of immediate relevance and priority.
The `GeoWAVE’ project has been launched to address this issue. Lead by the University of Dundee and funded with €1.1million from the European Union FP7 programme, the project also involves the University of Western Australia and University College Cork, together with a number of small to medium-sized enterprises (SMEs): Lloyds Register, Seaflex AB, Deep Sea Anchors, Wavebob Ltd and Cathie Associates.
“There is great potential for wave power to be a valuable source of renewable energy but if it is to be realised we have to make it robust and cost-effective,” said Dr Jonathan Knappett, Senior Lecturer in the School of Engineering, Physics and Mathematics at the University of Dundee, who is co-ordinating the project.
“One of the big challenges facing the industry is how wave energy convertors can be safely attached or anchored to the sea bed. Currently this accounts for around one-third of the production costs of convertors. That cost needs to come down if they are to be used within a fully commercial wave farm.
“If we can reduce the costs associated with station-keeping, then it will go a long way to making wave power an energy source that we can harness more effectively.”
GeoWAVE aims to address this immediate research need by conducting industry-specified research on a new generation of offshore anchors and mooring components deemed to have the highest economical and technical merit for mooring wave energy devices.
By doing this, GeoWAVE will remove the technical and economical hurdle of mooring wave energy converters to the seabed so that widespread deployment on a commercial scale becomes viable. The new knowledge generated by the project will be fully assigned to the SME partners in the project, thereby providing new business opportunities. The new approaches generated within GeoWAVE may also benefit other types of offshore green energy solutions such as floating platforms for offshore wind turbines.
The consortium will apply complementary methodologies in numerical, analytical and experimental modelling combined with field trials to increase the understanding of the combined response of the system and to develop economical and practical design solutions for the wave energy industry.
Sustainable offshore wave energy has the potential to make a real contribution towards the binding EU commitment to source 20% of its electricity requirements from renewable sources by 2020. The vast wave energy resource along Europe’s western seaboard is unparalleled anywhere in the world. Consequently the EU has an opportunity to become international industry leaders in what is becoming a rapidly evolving and dynamic marketplace. However technical and economical hurdles associated with anchoring wave energy devices to the seabed threatens to stall and limit the impact that renewable wave energy has the potential to deliver. Consequently the offshore renewable wave energy industry has collectively identified “mooring and anchoring systems” as a research topic of immediate relevance and priority.
GeoWAVE aims to address this immediate research need by providing a structure whereby industry specified research will be conducted on a new generation of offshore anchors and mooring components deemed to have the highest economical and technical merit for mooring wave energy devices. In so doing GeoWAVE will remove the technical and economical hurdle of mooring wave energy converters to the seabed so that widespread deployment on a commercial scale becomes viable, thereby providing new business opportunities for the SMEs.
This 2 year project brings together 3 SMEs, 3 RTD performers and 2 end-user groups from 5 EU member states. The research approach adopted by the consortium involves using complementary methodologies in numerical, analytical and experimental modelling combined with field trials to increase the understanding of the combined response of the system and to develop economical and practical design solutions for the wave energy industry.
The new knowledge generated by the project will be fully assigned to the SMEs, who will exploit the assigned intellectual property rights by maximising the market opportunity that is considered to open up by 2016.
- 1. To investigate the most suitable mooring configurations and components for Wave Energy Convertors that will minimise seabed footprint, motion impedance of the Wavebob WEC and anchor loads.
- 2. To provide performance data for a new generation of technically efficient anchors that will quantify expected anchor geometries for a given mooring configuration, water depth and seabed profile.
- 3. To utilise the new performance data from Objective 2 to develop and calibrate design methods for anchor installation, in-service performance of the moorings and anchors and an integrated station keeping tool for the WEC.
- 4. To utilise design methods from Objective 3 and performance data from Objective 2 to develop costing methods for mooring and anchoring Wavebob WECs at a particular site, permitting an economical viability assessment.
- 5. To conduct offshore testing to collate field data and verify design methods from Objectives 3 and 4.
WP1: Project management
The work package involves all administration and management of the project, particularly in relation to ensuring timely completion of deliverables from the technical work packages (WP2 to WP5) within the planned resource allocation.
WP2: Numerical and analytical modelling
The purpose of WP2 is to arrive at an optimal mooring and anchoring configuration which will minimise seabed footprint (and hence component costs), reduce anchor loading (and hence sizes), and reduce the impedance of the motion of the WEC (maximising power transmission). An initial screening exercise will qualitatively constrain the project to the site conditions (e.g. water depths, seabed properties, environmental loading regime) relevant for Wavebob WEC installations. Numerical analyses will then be conducted to simulate the response of a number of potential mooring configurations under generic and site specific loading. A key aspect of the work in WP2 is the development of a numerical model that incorporates the Seaflex mooring â€œspringâ€ component to permit realistic dynamic modelling of the mooring. The numerical model will be used to optimise the mooring configuration and to define the mudline loads that will be imparted to the anchor. Numerical and analytical studies of the anchor response will initially focus on quantifying the installation response of the anchors during installation, before analysing the capacity of the anchors as required both during in-service performance (under cyclic environmental loading), and during extreme (storm) events. WP2 is interdependent on both the physical modelling (WP3), and the field testing (WP4).
WP3: Physical modelling
This work package intends to establish by means of physical tests the performance of mooring configurations and anchors selected on the basis of their potential merit in economically and efficiently mooring the Wavebob WEC.
Both fixed beam and drum geotechnical centrifuges will be used to model and quantify the installation response and the in-service and ultimate holding capacity of reduced scale anchors (e.g. 1:100), whereas the UCC Ocean Wave Basin will be used to physically model and quantify the mooring line loads and motions under a variety of simulated active sea states. The output from this work package will be the experimental data from the anchor and mooring experiments which will iteratively be used to refine and calibrate the numerical and analytical models in WP2. As such WP3 is interdependent on the numerical and analytical modelling (WP2).
The combined output of WP2 and WP3 will define the mooring configuration and anchor to be used in the field testing (WP4).
WP4: Offshore field tests
The purpose of this work package is to provide the field data to validate the outputs from the numerical and analytical modelling (WP2) and the physical modelling (WP3). The main outputs from this work package are the field data and an interpretative report that compares the field data with predictions based on the design methods developed in WP5. In this work package, a series of offshore anchor installations and subsequent anchor loadings will be conducted at two offshore sites, the first with a sand seabed and the second with a soft clay seabed. The installations will be achieved using a marine work vessel (e.g. see Figure) and the deck winch on the vessel will be used to load the mooring and anchor. These tests will provide field data that is necessary to fully verify design procedures for installation of the anchors and in-service performance of the anchors and moorings.
WP5: Development of design and costing methods
Data from the numerical and analytical modelling (WP2), physical modelling (WP3) and offshore field trials (WP4) will be analysed collectively to develop and calibrate design tools for:
- quantifying anchor installation effort required to achieve target anchor embedment depths (in the seabed), and
- quantifying anchor holding capacity under in-service loading conditions (when the WEC is producing electricity), and during extreme storm events (when the WEC power takeoff is disabled and the sole requirement of the mooring is survivability by keeping the WEC on station).
Design criteria from these methods will be incorporated into a high-level integrated station keeping tool which will be used as a decision making tool for selecting the most appropriate mooring configuration and anchor type for given site characteristics. In addition the design methods and performance data from WP2 and WP3 will be used in the development of costing methods that will input directly into the mooring and anchoring element of the cost model for deployment of Wavebob WECs.
WP6: Dissemination, knowledge transfer and IP exploitation
In this work package dissemination, knowledge transfer and IP exploitation activities are planned and facilitated to maximise benefit to the SMEs in GeoWAVE and the EU wave energy industry. Dissemination is to different target audiences, including the general public, energy utility companies, certifying bodies and the engineering community (particularly offshore geotechnical and mooring designers). In this context, the involvement of the non-SME participants Lloydâ€™s Register and Cathie Associates play a key role in this work package. LR will provide input from a certification perspective, ensuring that the research outcomes, particularly the design tools are either compatible with the relevant standards, or are sufficiently robust to amend existing standards or inform new standards.