WAVE ENERGY: TECHNOLOGY TRANSFER & GENERIC R & D RECOMMENDATIONS ETSU V/06/00187//REP. Contractor: Arup Energy Ove Arup & Partners International

Transcription

1 WAVE ENERGY: TECHNOLOGY TRANSFER & GENERIC R & D RECOMMENDATIONS ETSU V/06/00187//REP DTI Pub/URN 01/799 Contractor: Arup Energy Ove Arup & Partners International Prepared by: D Scarr R Kollek D Collier The work described in this report was carried out under contract as part of the Sustainable Energy Programmes, managed by ETSU on behalf of the Department of Trade and Industry. The views and judgements expressed in this report are those of the contractor and do not necessarily reflect those of ETSU or the Department of Trade and Industry. First published 2001 Crown Copyright 2001

2 EXECUTIVE SUMMARY The Wave Energy Industry has developed successful prototypes for devices on the coastline and is currently in the process of developing prototypes for proving in near and offshore areas. As the industry moves offshore, the opportunity exists for transfer of technology from other industries, notably from the offshore oil and gas industry. Ove Arup & Partners (Arup) were invited by the UK Department of Trade and Industry (DTI) Wave Energy Programme to carry out a study to review the current status of the technologies in the emerging Wave Energy Industry, to identify the potential for transfer of technology from other industries and to make recommendations for priorities in future research and development. It should be noted that identifying device costs was not part of the study scope. Arup have reviewed the status of the industry by way of individual interviews with all teams currently active in the UK as well as by research of international activities in the area. A preliminary technology workshop was organised to identify and discuss key issues with the teams and other industries. The following technology areas were discussed: 1. Regulatory Environment, HSE, Design Codes and Verification 2. Construction Methods and Project Cost Estimation 3. Marine Operations 4. Mooring Systems 5. Operations and Maintenance 6. Materials 7. Hydraulic Systems 8. Pneumatic Systems 9. Subsea Cables and Connectors 10. Control Systems 11. Power Quality and Grid Connection The recommendations were made bearing in mind the proposed programme of Wave Energy Converter (WEC) prototype and power station development and the perceived need for further cost reductions. The major conclusions of the study were: The Wave Energy Industry is poorly co-ordinated. At present, all teams are working independently and commercial considerations force them to keep their ideas secret. There remains a lack of investor confidence and hence industrial support for the industry. Teams tend to be relatively small working out of University Departments or SMEs with some industrial backing. No major technological barriers to the development of Wave Energy Prototypes have been identified. All the issues raised under design, construction, deployment and operation can be addressed by transfer of technology from other industries, especially the offshore industry. However, costs, risks and approvals will need to be addressed. However, some technology gaps have been identified, notably in the areas of mooring and cable connections detailing, hydraulic machines and grid connection and energy storage. The major recommendations of the study were: i

3 Set up a supported co-ordinating body to encourage technology transfer to the industry. Government support should be directed at the proving of prototypes, thereby improving confidence and encouraging industrial support. High initial project costs, especially for offshore devices, will otherwise be a significant barrier to the development of prototypes. Several generic R & D activities have been identified to address the technology gaps. The results of this study were presented in a Workshop organised by the DTI in East Kilbride, Scotland on 24 October The report has addressed issues raised by participants at this event. ii

4 CONTENTS Page 1. INTRODUCTION Objectives Main Contributors Additional Contributors 2 2. METHODOLOGY Literature Review Wave Energy Team Input Issue Identification Technology Workshop Issue Clarification and Study Recommendations 5 3. WAVE ENERGY DEVICES Wave Energy Collector Database Classification Wave Energy Collector Type Location UK Wave Energy Collector Schemes LIMPET Pelamis Edinburgh Duck PS FROG Sperbuoy KEY TECHNOLOGY ISSUES Regulatory Environment, HSE, Design Codes and Verification Construction Methods and Project Cost Estimation Marine Operations Mooring Systems Operations and Maintenance Materials Hydraulic Systems Pneumatic Systems Subsea Cables and Connectors Control Systems Power Quality and Grid Connection CONCLUSIONS AND RECOMMENDATIONS Conclusions Recommendations FIGURES ACKNOWLEDGEMENTS 63

5 APPENDICES A. WEC CONTACTS DATABASE A1-6 A1. WEC Teams A2. Industry contacts B. TECHNOLOGY WORKSHOP KEY ISSUES SLIDES B1-24 C. WEC TEAM QUESTIONNAIRE RESPONSES C1-32 D. TECHNOLOGY WORKSHOP MINUTES D1-9 E. TECHNOLOGY WORKSHOP QUESTIONNAIRE RESULTS E1-12 F. BIBLIOGRAPHY F1-3 F1. Literature Bibliography F2. Internet Bibliography F2.1 At Shore F2.2 Near Shore F2.3 Offshore F2.4 Academic F2.5 General

6 1. INTRODUCTION One of the largest potential areas for Renewables Energy Development is in the exploitation of Energy from the Waves. The Wave Energy Industry has developed successful prototypes for devices on the coastline and is currently in the process of developing prototypes for proving in near shore areas. As the industry moves offshore, the opportunity exists for transfer of technology from other industries, notably from the offshore oil and gas industry. The offshore oil and gas industry has itself undergone considerable development in the last ten to twenty years, with notable key developments in subsea, floating and unmanned facilities and technologies. Great efforts have also been made to reduce costs, notably the Cost Reduction in the New Era (CRINE) Initiative of the mid 1990s. The UK Department of Trade and Industry (DTI) Wave Energy Programme has recognised that this potential exists and has asked Ove Arup & Partners (Arup) to undertake a review of the current Wave Energy technologies and to identify areas where the potential for transfer of technology exists from other industries, notably the offshore oil and gas industry to the emerging wave energy industry. In addition, Arup were asked to identify where generic research and development might improve or adapt existing technology to enable the development of Wave Energy Converter (WEC) schemes. The Wave Energy Programme is currently being managed by the Energy Technology Support Unit (ETSU). Arup Energy, part of the Industrial Engineering Sector of Ove Arup, have carried out the study work. This report summarises the work carried out and in its draft version was used as preparatory material for a Technology Workshop organised by ETSU in East Kilbride, Scotland on 24 October Feedback from this workshop is included in this report. The study was carried out between August and December Objectives The study had the following objectives: Review existing wave energy technologies by consultation with current WEC developers and technologists. Identify the key technology issues facing the development of WECs. Propose transfer of technology from other industries, notably the offshore oil and gas industries to the emerging Wave Energy Industry. Make recommendations for generic research and development which would promote the development of WEC schemes. Make recommendations for future priorities and research and development funding strategy to support the industry. This report does not attempt to provide solutions to technical problems of the Wave Energy Industry or to evaluate the performance of any of the devices. Rather, it aims to identify common issues faced by developers of Wave Energy Technology and suggest the methods by which the issues should be resolved. Page 1

7 1.2 Main Contributors Arup Energy, part of Ove Arup & Partners, based in London, Aberdeen, Perth, Houston and Singapore provides multidisciplinary services focused on energy sector companies engaged in upstream activities from exploration and extraction to transmission and distribution. Projects include Steel and Concrete Offshore Platforms, Pipelines, Power Stations and Coastal Engineering. Arup Energy is a multidisciplinary organisation focusing on structural and civil engineering project design and management supported by core experience in naval architecture, hydraulics and mechanics, controls and instrumentation, risk and safety. Dr Tony Lewis from University College Cork assisted in the Arup study as a consultant for Wave Energy technologies. Dr. Lewis has monitored or been directly involved in the development of most of the Wave Energy schemes developed over the last twenty five years around the world. He has considerable experience in key wave energy technologies and has been previously involved in the European, UK and Irish Wave Energy Programmes. Dr Lewis is Director of University College Cork s Hydraulics and Maritime Research Centre. 1.3 Additional Contributors Arup Energy invited a number of WEC teams to contribute to the study. The following teams were interviewed: Wavegen Queens University Belfast Ocean Power Delivery Edinburgh University Professor Michael French Plymouth University The following WEC teams submitted a completed questionnaire: Energetech, Australia Hosepump, Sweden OMI, USA OWEC, USA Professor Johannes Falnes, Sweden Wavebob, Ireland Several companies provided input: ETSU Ramboll Lloyds Register HSE Offshore Contractors Association Noble Denton Conoco Rexroth BHR Group Alcatel Kabel ABB Page 2

8 Econnect Scottish and Southern Electricity WS Atkins Garrad Hassan Tronic Contact details are provided in Appendix A. Page 3

9 2. METHODOLOGY The overall project process adopted was as follows: Information was gathered through a review of published and internet based data Active WEC teams were interviewed by Arup personnel Key technology issues were identified in consultation with WEC teams A Technology Workshop was organised in London to facilitate discussions and continue transfer of technology between offshore industry personnel and WEC teams and to refine the understanding of Key Technology needs In each technology area, the potential for technology transfer was identified and recommendations for research and development made. 2.1 Literature Review The objectives of the early stages of the study were twofold: To identify and contact teams developing WECs or involved with Wave Energy Technology. Identify key issues for the development of WECs already publicised. Recent published information was reviewed. See Appendix F for a bibliography. A search of available internet sites was carried out. See Appendix F for a list of addresses. 2.2 Wave Energy Team Input There are only 6 WEC teams currently active in the UK. It was decided to meet with all of these teams. Teams outside the UK were also given the opportunity to participate in the study by , fax and telephone. The teams were asked to identify key technology issues perceived by them as technically unproven, incurring significant cost or areas outside their immediate control. Discussions covered all stages in the development of their scheme; design (structural, mechanical, hydraulics, electrical, control, etc), construction, transportation and installation, inspection, maintenance, repair and removal. Responses were recorded on a pro-forma questionnaire. Responses are included in Appendix C. Wave Energy Teams outside of the UK were contacted by . They were also requested to complete the questionnaire. Their responses are also included in Appendix C. 2.3 Issue Identification Responses to the questionnaires, minutes of meetings with WEC teams and all of the data collected to date were critically assessed by in-house specialists in each technology area. Consultation was sought with experienced parties in the offshore and other industries. Key technology issues requiring technology transfer and/ or research and development were identified in each technology area. Page 4

10 2.4 Technology Workshop A Technology Workshop was organised to discuss and verify the Key Technology Issues identified. These were summarised in presentation slides used at the workshop (see Appendix B). The event provided an open forum to discuss problems faced by the Wave Energy Industry and current experience from the offshore and other industries. Participants were drawn from three fields: WEC Teams Offshore Oil and Gas Industries Other Industries In addition, it provided an opportunity for Wave Energy Teams to meet and develop contacts with representatives from the other industries. The technology workshop was held on September 15 th at the Arup offices in London. Over 40 attendees attended from a wide range of sectors. The agenda was structured by Arup around the key technology areas identified from the interviews and earlier consultation. Each topic was introduced by an Arup Facilitator, the key technology issues raised and a relevant presentation was made by a representative from the offshore industry. The open discussion which followed was minuted (see Appendix D). A second questionnaire was introduced at the workshop to help gauge support for key technology issues in each area. 2.5 Issue Clarification and Study Recommendations Following the workshop, the key technology issues identified earlier were reviewed in the light of the workshop findings. The workshop minutes were examined and the workshop questionnaire responses were collated and main messages identified (see Appendix E). Using this information, the most important key technology issues were refined. The in-house specialists considered each of the key technical issues and recommended a suitable course of action for their resolution. Page 5

11 3. WAVE ENERGY DEVICES 3.1 Wave Energy Collector Database A database has been compiled which lists all WECs under development worldwide. See Appendix A. The database contains the name, status, description and contact details for each device. 3.2 Classification Many different types of device are under development in the UK and worldwide. The approach of this study is to consider wave industry technology needs, without reference to specific devices. It was therefore decided to introduce a classification for families of devices that share similar features. There are many ways to classify devices. The system chosen for this study uses two methods; WEC type and location. 3.3 Wave Energy Collector Type 3.4 Location Buoyant Moored Device A device of this type floats on or below the water surface. It is moored to the seabed either with a taut or slack mooring system (Figure 3.1) Hinged Contour Device A hinged structure follows the contours of the waves and takes power from the motion at the joints. It is slack moored to hold it on station (Figure 3.2) Oscillating Water Column (OWC) An OWC uses an enclosed column of water as a piston to pump air. These structures can float, be fixed to the seabed or mounted on the shoreline (Figure 3.3) At Shore A device of this type is sited at a shoreline location on land Near Shore A near shore device will be sited in open water, within 12 miles of the shoreline. This distance has been arbitrarily chosen as the approximate average limit of visibility from the shore. Near shore should also be understood to refer to shallower water depths than offshore. Approximately 50m water depth has been arbitrarily chosen as the near shore water depth Offshore An offshore device will be sited further than 12 miles from the shoreline. Water depths of greater than 50m constitute offshore devices. Page 6

12 3.5 UK Wave Energy Collector Schemes The following sections introduce (in no particular order) the current range of WEC schemes under development in the UK. A brief description of the devices and the current status of the project is described. Key technology issues identified by the teams themselves in interviews with Arup are listed. The devices selected are not an exhaustive list of the schemes or teams under development in the UK. Rather, they were selected, in discussion with the UK based teams, to represent the range of devices currently under consideration. A more complete list appears in Appendix A1. Table 4.1 illustrates the diversity of types of WEC under development in the UK. Table 4.1 Classification of UK WECs Scheme Limpet Pelamis Edinburgh Duck PS Frog Sperbuoy Buoyant Moored WEC Type Hinged Contour OWC At Shore Suitable for Location Near Shore Off Shore Page 7

13 3.6 LIMPET Device Description Limpet 500 is a shoreline, Oscillating Water Column (OWC) type WEC (Figure 3.4). It is currently supplying 0.5MW of power to the grid on the Scottish island of Islay. The wave energy collector is in the form of a partially submerged shell into which seawater is free to enter and leave. As the water enters or leaves, the level of water in the plenum chamber rises or falls in sympathy. A column of air, contained above the water level, is alternately compressed and expanded by this movement to generate an alternating stream of high velocity air in an exit blowhole. If this air stream is allowed to flow to and from the atmosphere via a pneumatic turbine, energy can be extracted from the system and used to generate electricity Current Status The LIMPET 500 was scheduled for commissioning in October Further modules are planned in a second stage of development in the future. Limpet has been developed to its current commercial stage as a collaborative project between Wavegen (a private company) and Queens University, Belfast who have been involved in the research and development of wave power generation for over 20 years. Wavegen are developing a new offshore WEC, details of which have yet to be released Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. Clarification of HSE regulations and underwriter requirements. Guidelines for OWC construction. Wave data for WEC locations. Data for structural slam loads from waves. Estimating construction costs. Construction contracts. Rapid attach/detach moorings. Site investigation data for prototype anchorage. Design lifetime of components and materials. Erosion of rust. Power transmission by fluid to shore. Difficulties with the use of pneumatic systems offshore. Comparison between the different types of pneumatic turbines Subsea connector and cabling costs. Control algorithm optimisation Grid information; demand and supply locations, available capacity from nuclear power plant decommissioning, unrealistic specification of grid, comparisons with grids outside the UK. Page 8

14 3.7 Pelamis Device Description The Pelamis WEC is a hinged contour device for deployment offshore (Figure 3.5). The wave induced motion of the joints is resisted by hydraulic rams which pump high pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. A 750kW device will be 150m long and 3.5m in diameter and composed of 5 modular sections. Power will be linked to the grid via subsea power cables. Key features incorporated into the concept include: Survivability Power capture efficiency Non site specific Minimum on-site work 100% available technology Modular construction and systems Current Status Pelamis is being developed by Ocean Power Delivery (a private company). They have a development programme which aims to demonstrate the concept through a staged test programme. Model testing (both in the frequency and time domain) at 80 th (survivability), 35 th (numerical code validation) and 20 th (survivability and numerical model validation) scale have been successfully completed. The next immediate target is a 7 th scale prototype for systems development to be deployed in early Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. Standard test site to assist in prototype deployment and device comparison. Patent applications. Power absorption in structural design calculations. Estimating construction costs. Approval permits required and timetable. Fretting resistant design detail of mooring connection. Rapid attachment/detachment moorings. Mooring line material life. Hydraulic seals. Subsea cables and connectors. Time domain modelling. Short term smoothing of power. Feasibility of isolating the device from grid fault conditions. Page 9

15 3.8 Edinburgh Duck Device Description Ducks (Figure 3.6) have a stubby aerofoil cross section. A number of them rotate independently about a long articulated spine which obtains stability by spanning wave crests. The angular variation of displacement of the front surface is designed to match wave particle motion. In moderate sea states the mostly cylindrical back section of the duck creates no stern waves but the larger movements induced by rough weather shed energy through wave making to the rear. Spine joint movements and moments are controlled by rams which contribute to overall power capture and which give to shed energy in large waves. This puts a defined upper value on the stresses and reduces the mooring forces. The mooring needs at least 80 metres of water and uses a system of submerged weights and buoys to give an almost constant tension Current Status The Duck team is led by Professor Salter at Edinburgh University. This concept requires the development of new technologies. The team is working on component parts of a high torque hydraulic system. These include ring cam pumps and fast hydraulic motors with low part-load losses. The displacement of these machines is varied by digitally controlled poppet valves. The team have also developed a Wells Turbine with variable pitch for use at the Pico, Azores Oscillating Water Column project and are researching the Sloped IPS Buoy wave energy device Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. Estimating costs. Constant tension loading on mooring lines. Light, quite strong and cheap building material. (e.g. ultra light concrete). High performance hydraulics, inc. high torque ring cam pumps. Large, high velocity seals. Squeeze film bearings. Page 10

16 3.9 PS FROG Device Description The P S Frog is a WEC of the buoyant moored, offshore type which aims to generate a mean output of 600kW per unit (Figure 3.7). It is entirely enclosed within a floating sealed hull, with no external working parts. The FROG behaves as a point absorber with large motions; this requires resonance to achieve a high dynamic magnifier. The whole hull works as a pendulum to supply the reaction. The motion can be analysed into forced pitching about P, which provides the reaction, combined with resonant pitching about G, which provides the motion of the working surface (the paddle). It is tuned to the prevailing wave frequency by moving water ballast ( slow tuning ). A sliding mass restrained by hydraulic rams acts as the power take-off by providing an alternating gravitational torque about the pitch axis. There is a large hydraulic accumulator which provides both a store and smoothing, and a hydraulic motor driving the generator. Because real seas are irregular, the sliding mass must be controlled to achieve quasi-resonance, by switching the ram state between pumping, driving, idling and (judiciously) locked, (dynamic tuning) Current Status The FROG has been developed at Lancaster University in a team led by Professor Michael French. Work thus far has been almost exclusively conceptual. Limited model testing was carried out to verify the theoretical performance. A lack of funding has restricted development beyond this stage. Since last year the team have modified the design to locate the sliding mass above the water and fill the bottom compartment with ballast. The team claim this should increase the output, reduce the mass required and simplify the engineering Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. Wave data for use in design. Estimating Costs (construction, marine operations, moorings). Rubber joints used on moorings. Reliability of compliant mooring systems. Water based hydraulic systems. Hydraulic seals and leakage. Compatibility of cables with compliant moorings. Page 11

17 3.10 Sperbuoy Device Description The Sperbuoy is a floating oscillating water column device for deployment in the near shore environment (Figure 3.8). The device has four vertical capture chambers of different length. A floatation unit around the circumference provides buoyancy and the power take off sits on the top of the device. The unit is 12m long and 5m diameter. The aim of the multiple chambers is to extend the capture bandwidth of the device to improve efficiency. Power take off will be from an impulse turbine which drives a generator. The power generation target is 5kW although the prototype device will not supply the grid; it will be used to collect data. The device is transported to site on board a vessel. It is deployed by winching it overboard and attaching it to pre-laid moorings Current Status The project was initiated by Embley Energy and is being developed under the European Commission CRAFT scheme. The partners involved are a consortium of Small to Medium Enterprises (SME): Embley Energy Ltd CTP Limited IBK Bernard Bonnefond Hippo Marine Products There are also 3 Research to Development performers (RTD): PEP, University of Plymouth University of Cork Chalmers University of Technology The prototype Sperbuoy was scheduled for launch in the Plymouth Sound in November It will operate for a period of months during which time data will be collected on its behaviour Key Industry Technology Issues Identified by the Team The team identified the following as Key Technology Issues for the Wave Energy Industry as a whole. An archive of previous work to assist in research. Data on wave climate. Flexible attachment to the mooring system. Quick release mooring systems. Installation guidelines. Investigation of the relative efficiencies of a Wells Turbine and an Impulse Turbine. CFD analysis of the pneumatic system. A flexible power connection which floats. Page 12

18 4. KEY TECHNOLOGY ISSUES The perceived Key Technology Issues affecting the Wave Energy Industry were identified and reviewed. The issues were discussed with the WEC teams active in the UK. Teams active outside of the UK were given the opportunity to contribute by way of questionnaires. The issues were verified at the Technology Workshop held in September. During this process, the following technology areas were identified for detailed consideration: 1. Regulatory Environment, HSE, Design Codes and Verification 2. Construction Methods and Project Cost Estimation 3. Marine Operations 4. Mooring Systems 5. Operations and Maintenance 6. Materials 7. Hydraulic Systems 8. Pneumatic Systems 9. Subsea Cables and Connectors 10. Control Systems 11. Power Quality and Grid Connection In the following sections, the Key Technology Issues for each technology area are identified. For each issue, the current status and recent advances which affect this issue are discussed, potential for technology transfer is identified and any generic research and development needs are recommended. Page 13

19 4.1 Regulatory Environment, HSE, Design Codes and Verification Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: What Regulations will apply? Will Energy Making Devices be treated the same as Offshore Oil and Gas Installations? Will prototypes be treated differently to full scale WEC Power Stations? What is the Planning Approvals and Licensing Route? Are there parallels with other Industries; e.g. Offshore Wind? These questions were raised by the WEC teams because the planning and approvals process for WEC prototypes is not well defined. They were aware that offshore wind schemes have experienced difficulties because of the many authorities responsible for coastal and offshore locations. Parallels in terms of lessons learned regarding design codes, approvals and technologies. Which Design Codes apply? Are the codes developed for offshore oil and gas applications still applicable for the design of WEC schemes? There are considerable design philosophy differences where human life is directly at risk and hazardous inventories are involved. What is the Verification and Underwriting Process? What Deficiencies exist in Input Data to the Design Process? Potential for Technology Transfer Applicable Regulations Design verification, underwriting and insurance will be required to gain approvals. Are there areas such as wave incidence, height, spectral information or persistence data missing for important sectors of the seas around the UK? The Health and Safety Executive (HSE) Regulations that apply to unmanned Wave Energy Devices were clarified at the Technology Workshop. They are: Health and Safety at Work Act (HSWA) Construction Design Management (CDM) Regulations Management Regulations. A Wave Energy Device does not fall into the same category as an offshore installation. Amendments are being made to the HSWA to classify Wave and Wind Page 14

20 Energy Converters as Energy Structures. A period of open consultation concluded on 11 August The amended regulations will come into force in mid The expected definition will be, A fixed or floating structure, other than a vessel, for producing energy from wind or water. WECs which supply power to an offshore installation will be classified as a Supplementary Units. They will be regarded as part of the installation which they support and Safety Case Regulations will apply. There is currently no reason to believe that WEC Prototypes will be viewed any differently from Full Scale WEC Power Stations. Planning Approvals and Licensing Route Currently, WEC Planning may require the approval of many authorities: The Health and Safety Executive Local and Central Government Crown Estates Fishing Industry Shipping Authorities Wind Energy companies have found the approvals process for offshore wind farms to be time consuming and complex. Approvals for the Blyth Wind farm took around one year and involved applications to thirteen different bodies. Since then, Wind Energy Companies have worked with the various authorities to streamline the procedure within 12 miles of the shoreline. This may assist at shore and near shore WECs. An exercise has been carried out in the Irish Republic to streamline the approvals process[1.14]. A similar study to investigate approvals in the UK will be useful for WECs. Design Codes Specific design codes for WECs do not currently exist, however there are a large number of different codes which may be used to design offshore structures: Det Norske Veritas (DnV), American Petroleum Institute (API), British Standard (BS), [1.1] to [1.12]. Extensive offshore industry engineering experience exists in selecting the correct parts of these codes and combining them in a consistent and compatible manner. This experience will be very useful to Wave Energy Teams during the design process. Verification and Underwriting Process Lloyd s Register and Det Norske Veritas are commonly involved in design verification of vessels and offshore structures in the oil and gas industry. The process for verification of WECs would be similar. The legislative framework would, as always, take account of the National Authorities, International Law, Existing Regulations (see Applicable Regulations above). Each design would be required to produce a functional specification and performance criteria and would be judged to applicable engineering standards. Some level of risk assessment should also be expected. The key issues for the design verification will be: Page 15

21 Performance issues Design life, maintainability and power output. Safety issues Risks to personnel during construction, installation and operation, loss of structural integrity or vessel worthiness and interference with other users; shipping channels, etc. Environmental issues Visual impact, fisheries, waste and emissions. Data Deficiencies Considerable work was done as part of the former Department of Energy s wave energy programme and by Queen s University Belfast in the 1990s on Metocean Data gathering and interpretation. However, it has been suggested that Metocean data deficiencies may exist in the following areas for near coastal areas for the development of coastal WECs: Coastal wave spectra, scatter diagrams, persistence data Coastal wave shapes and fluid loading These issues have, for near and offshore uses in the North Sea and more recently West of Shetlands, all been well researched and documented by the Offshore Oil and Gas Industry. Omissions certainly exist for coastal areas. However, it is unlikely that these omissions will seriously affect the structural design of a coastal structure such as a breakwater or seawall as their design is covered by the British Standard for Maritime Structures [1.10] and the American Army Shore Protection Manual [1.11]. A special case not covered by the codes is the inside of an OWC chamber. The JONSWAP (Joint North Sea Wave Project) Spectrum is commonly used for offshore platform design for fetch or duration limited seas. Other spectra commonly used are the Bretschneider and Pierson-Moskowitz spectra [1.1]. Scatter diagrams and persistence data applicable to near and offshore locations are also abundant. Their applicability for near coastal waves is questionable and incorrect wave statistical modelling will affect the prediction of power output from coastal devices. Near and offshore wave shapes and fluid loading have been exhaustively examined for the type of structure commonly encountered in the offshore oil and gas industry. Morison s equation and diffraction analysis methods [1.1] are commonly used to predict loading on fixed structures and floating bodies. For coastal areas, there is considerably less data and design codes are more empirical [1.10, 1.11, 1.12]. For offshore sites (see favoured Wave Energy Locations from [1.13], Figure 4.1), Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion Generic Research and Development Needs No generic R & D needs were identified. Although gaps in data exist (see previous sub-section), these are considered to be for coastal schemes only and are specific to location Conclusions and Recommendations The major conclusions of this sector are: Page 16

22 The Planning and Approvals process for at shore and near shore WEC schemes should benefit from the recent work carried out by the Wind Energy Industry. The approvals process for WECs requires clarification, and a study, similar to the one carried out in Ireland, should be commissioned. The Design and Verification Processes are well established for the Offshore Oil and Gas and Shipping Industries. These methods can be readily transferred to the design and verification of WECs. Although some data gaps exist, particularly for coastal areas, no generic research is recommended because each data gathering exercise will be site specific. Structural designs can be established based on existing offshore oil and gas and shipping industry methods and data. Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial References [1.1] Dynamics of Fixed Marine Structures, Barltrop and Adams, 3 rd Edition, Butterworth and Heinemann, [1.2] Floating Structures; A Guide for Design and Analysis, Barltrop, Oilfield Publications, Inc., [1.3] Health and Safety Executive, (HSE), Offshore Installations: Guidance on Design, Construction and Certification, 4 th Edition and Amendments to 1996, London HMSO. [1.4] American Petroleum Institute (API), Recommended Practice for Planning, Designing and Constructing Fixed Offshore Platforms Allowable Stress (API-RP2A-WSD 20 th Edition, 1993 or Load and Resistance Factor (API- RP2A-LRFD 1 st Edition, 1993), etc. [1.5] Det Norske Veritas, (DnV), Guidelines and Classification Notes for Fixed Platforms, 1998, Mobile Offshore Platforms, [1.6] American Bureau of Shipping (ABS), Rules for Building and Classing Steel Barges, 1991; Steel Vessels, [1.7] Lloyds Register, Rules and Regulations for the Classification of Fixed Offshore Installations, 1989, Mobile Offshore Units, 1996, Ships, [1.8] British Standard for Structural Use of Concrete, BS 8110: [1.9] British Standard for Structural Use of Steel, BS5950: [1.10] British Standard of Maritime Structures, BS [1.11] American Coastal Engineering Research Centre; Shore Protection Manual, 4 th Edition, [1.12] Rock Armour Manual, CIRIA. [1.13] Wave Energy, The Department of Energy s R&D Programme , ETSU for the Department of Energy, March [1.14] Discussion Document on Policy for Offshore Wind and Wave Electricity Generation, Irish Ministry for Marine and Natural Resources, February Page 17

23 4.2 Construction Methods and Project Cost Estimation Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: How to estimate project costs accurately within the design process? What yards/ factories/ contractors are available? What construction/ fabrication methods and guidelines can be considered? Potential for Technology Transfer Cost Estimation This major issue is necessary for WEC teams to make cost effective design decisions. Information on fabrication facilities significantly affects detailed designs. Fabrication information can significantly affect detailed design. The Offshore Oil and Gas, Onshore Civils and Manufacturing Industries have the means to accurately cost projects of this nature. Engineering Consultancies routinely need to estimate project costs for construction, installation and operation with only a conceptual design available. Most of this experience exists within Engineering Consultants and is regularly updated by new live projects and input from Fabricators, Installation Contractors and Operators [2.3]. In addition, Fabricators and Installation Contractors have excellent means of estimating their own yard or vessel costs. However, both parties tend to be reluctant to divulge this information as it is considered commercially sensitive. In short, suitable costing databases and costing methods exist and this experience and data needs to be accessed to carry out accurate cost estimates for WEC prototype development and, subsequently, WEC power station development. Only when the design process encompasses all the project driving issues of construction, installation and operation, can true life cycle costing estimates be achieved. However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down. Available Contractors The next step for each WEC team is to include input from construction/ installation experts and, ideally, the potential fabricator and installation contractor. This input Page 18

24 should initially take the form of collaboration at concept definition stage and subsequently partnerships or alliances should be formed to include designers, fabricators, installers and operators. Directories are readily available giving contact details by technological area in the onshore and offshore construction industries [2.1], [2.2]. Construction and Fabrication Guidelines A great deal of experience has been gained in the onshore and offshore construction industries as to the most cost effective ways of realising concrete and steel construction (Figures 4.2, 4.3). All fabricators will be able to give high level guidance about material usage, stockpiles, and favoured fabrication methods. The design can and should be modified to suit as far as possible. Successful inclusion of fabricator input at the concept design stage will minimise design complexity, the chance of failure and unforeseen increases in fabrication costs Generic Research and Development Needs In general, no generic technical work can or should be done to support the industry as a whole. Each device team would benefit from seeking advice from one of the industries identified above. All conceptual WEC schemes need to be subjected to Detailed Design, Fabricator and Installation Contractor Input and Cost Estimation along the lines outlined above. This can be done on a scheme by scheme basis by the WEC team contacting an appropriate contractor and engaging in discussions as to how cost savings can be achieved. For example, cheaper materials may be available for re-use, construction methods may offer considerable savings if a small design change is made, or economies of scale could be explored. To facilitate this process, a study should be commissioned to prepare a contact list of contractors interested in becoming involved with WEC teams and willing to engage in discussions. This should include: Onshore and Offshore Construction Yards (Steel and Concrete) Shipyards Manufacturing Industry Construction Technologists and Consultants Installation Contractors (see also Marine Operations) A start has been made as part of this project (see Contacts Database, Appendix A), but a more complete and thorough review of all relevant industries; offshore oil and gas, coastal protection, onshore construction and manufacturing industry taking in suppliers of conventional materials as well as those supplying more exotic materials such as plastics and alloys. It is recommended that a second study be commissioned to summarise simple construction and installation guidelines for steel and concrete construction with the goal of short-circuiting the WEC prototype design cycles and estimating realistic final project costs at an early stage of development. This study could be combined with the Wind Energy sector which is also currently extremely interested in construction and installation method guidelines. Page 19

25 4.2.4 Conclusions and Recommendations All the above issues are symptomatic of the Wave Energy Industry making the initial steps from Research and Development Projects to Prototype and Power Station Developments. The major conclusions of this sector are: Significant opportunity for transfer of costing information and methods exists from the Offshore Oil and Gas, Onshore Civils and Manufacturing Industries. However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down. A study is recommended to prepare a full contact list of all parties interested in being or becoming involved in WEC schemes. This to facilitate the design process of WEC prototypes and power stations and to enable more reliable cost estimates to be achieved. A study is recommended outlining fabrication and installation guidelines for WEC schemes to be produced from steel and concrete in offshore and onshore industry facilities. This should include manufacturing guidelines for WEC schemes that are likely to benefit from the production line manufacturing philosophy References [2.1] Offshore Oil and Gas Directory; published annually, Miller Freeman Information Services, Tel: , [2.2] Maritime Guide (Dry Docks, Shipbuilders Directory), ISBN , Lloyds Register of Shipping, [2.3] SPON s European Construction Costs Handbook, Edited by Davis Langdon and Everest, Third Edition, currently in production. Page 20

26 4.3 Marine Operations Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: What Marine Operations can be considered? All near shore and offshore WECs need to be transported to site and installed. The available technology, procedures and costs require investigation. Metocean Data Marine operations will be subject to prevailing weather conditions. Major cost and safety consequences result from poor statistical data and inadequate contingency planning. Risk and Safety Assessments These will be required to meet HSE approvals and to gain verification Potential for Technology Transfer Installation Guidelines A great deal of experience has been gained in the offshore oil and gas industries on the most cost effective ways of performing marine operations (Figure 4.3, 4.4). A vast array of vessels are now available [3.2] to carry out a variety of offshore tasks; lifting operations, transport operations, diver support, Remote Operating Vehicle (ROV) deployment, cable laying, pipelaying, trenching, etc. Acceptable sea states for vessel operation and different marine procedures are well known by Marine Contractors. The basic guidelines for planning offshore operations should be: To be well informed of Metocean data statistics and forecasting To minimise activities and time offshore To minimise exposure to unfavourable weather conditions with knock-on delays and exponential cost increases To plan for contingencies WEC designs should include careful consideration of these guidelines from early conceptual planning. This should be done by the teams including early input from marine operations experts and, ideally, the would be installation contractor. Successful inclusion of marine operations input and inclusion of the temporary condition load cases in the design at the concept design stage will minimise the chance of design complexity, offshore failure and unforeseen increases in marine operations costs. Page 21

27 To facilitate this process, a study should be commissioned to prepare a contact list of Installation Contractors interested in becoming involved with WEC teams. This should include Operators of: Tugs Crane Vessels Pipe Laying Vessels Cable Laying Vessels Piling Vessels Construction Jack-ups Diving Spreads and Diver Support Vessels Remote Operating Vehicle (ROV) Suppliers Marine Operations Technologists The study should include a summary of marine operations guidelines and approximate day rates and mobilisation costs with the goal of enabling the WEC teams to make informed decisions on these cost driving issues at an early part of the design process. Published directories exist giving contacts of vessel owners and operators, as well as marine technologists [3.1], [3.2]. Metocean Data Metocean data collected for use by offshore operators will help WEC teams to identify an installation weather window. This data will tend to be limited to those areas used by Oil and Gas Operators for platform sites, tow routes or pipeline routes. Hence, significant data exists from past and current projects in the North Sea and more recently, and more pertinently perhaps, the West of Shetlands area. Some sources of available data in the North Sea are given in references [3.3], [3.4]. Deficiencies in data have been identified in some coastal areas; see Section 4.1 for recommendations. Risk and Safety Assessments Risk and Safety Assessments are now well embedded in the Design Process for all Offshore Oil and Gas Facilities. Within UK waters, the Health and Safety Executive introduced a requirement to provide an Operational Safety Case for (A case for the safety of) all offshore Oil and Gas facilities following the Piper Alpha disaster of These typically consist of hazard assessment studies, consequence and risk assessment studies which, taken together with the ALARP principle (As Low As Reasonably Practicable), argue the case for the Operator having taken due care and attention in the design and operation of the facility. Similar issues will need to be assessed as part of the design process for WEC schemes, although current legislation is not expected to require as comprehensive an assessment as is typically required for offshore oil and gas facilities. This is largely because of the relatively low risk to human life and environmental damage associated with WEC schemes. Several companies have developed in the last ten years who specialise in these safety assessments for all types of offshore operations [3.1] Generic Research and Development Needs No generic needs have been identified in this area. Page 22

28 There are many different types of WECs and each requires different marine operations. It is difficult to identify common ground where a generic study would benefit the whole industry. The Offshore Industry has installed a wide range of structures and the current range of WECs could be installed as a matter of routine Conclusions and Recommendations All the above issues are symptomatic of the Wave Energy Industry making the initial steps from Research and Development Projects to Offshore Prototype and Power Station Development. The major conclusions of this sector are: Each device team would benefit from collaboration with the offshore industry in the above Key Technology Transfer issues. All conceptual WEC schemes need to be subjected to Marine Operations Input and Cost Estimation and Risk and Safety Assessment as part of the Design Process. This should be done on a scheme by scheme basis by the WEC team contacting the Installation Contractor and engaging in discussions as to how cost savings can be achieved. To facilitate this process, a study should be commissioned to prepare a contact list of Installation Contractors interested in becoming involved with WEC teams. The study should include a summary of marine operations guidelines and approximate day rates and mobilisation costs with the goal of enabling the WEC teams to make informed decisions on these cost driving issues at an early part of the design process. Offshore Operators can be recruited to supply Metocean data for tows and installation weather windows References [3.1] Offshore Oil and Gas Directory; published annually, Miller Freeman Information Services, Tel: , [3.2] Construction Vessels of the World, 5 th Edition, OPL, Oilfield Publications Ltd. [3.3] Health and Safety Executive, (HSE), Offshore Installations: Guidance on Design, Construction and Certification, 4 th Edition and Amendments to 1996, London HMSO. [3.4] Meteorological Office Home Page; Page 23

29 4.4 Mooring Systems Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: New Developments Reliability and Maintainability Deployment and Retrieval Potential for Technology Transfer New Developments Taut Moorings, Synthetic Fibre Ropes, Floating Production, Storage and Offloading (FPSO)s, Tanker Offloading Systems, Dynamic Positioning Systems All offshore WECs will be moored in some way to the seabed. The reliability of these systems will be paramount to their successful deployment, operation and verification. Quick Release/ Re-attachment Great potential for transfer of technology exists from the Offshore Industry to the Wave Energy Industry [4.1], [4.2]. Relevant technologies are Floating Production, Storage and Offloading (FPSO) systems. Of particular interest, because of their location, will be the recent experience West of Shetlands in the BP Foinavon and Schiehallion Fields. Also relevant are recent developments in Tanker Offloading Systems in general, as well as the use of Dynamic Positioning Systems in vessels which may be maintaining the WEC schemes. A major development in offshore mooring systems has been the use of synthetic ropes and taut leg moorings. The Campos Basin B27 installation is a good example. Synthetic ropes [4.2] potentially offer significant advantages over a conventional mooring line. They have a much higher strength to weight ratio and improved extreme dynamic tensions. The lower weight reduces some of the buoyancy required by a traditional catenary. Taut leg moorings may be of interest to developing WEC Schemes located in deep water. They have a smaller footprint and smaller wave frequency tensions than a catenary mooring system. The latter property could prove advantageous for snatch loading which was identified as an issue by one of the device teams. These recent developments could be utilised in the designs for Offshore WEC Schemes under certain circumstances Generic Research and Development Needs Reliability and Maintainability The Offshore Oil and Gas Industry has considerable experience in the reliability of key components in the design and operation of offshore facilities. However, it is understood that long term fatigue issues of lines and connection points at either end have not been analysed in detail to date. A useful study could be commissioned to Page 24

30 address this. The issues and references are discussed in Operation and Maintenance (Chapter 4.5). Deployment and Retrieval The Offshore Oil and Gas Industry now has considerable experience in the installation of buoys and mooring systems. A means of quick release and re-attachment between WEC devices and its mooring system for change out and retrieval has been identified as a potential technological issue. A specific review of the available technology for achieving this would be valuable and, it is recommended that the development of a standard connection detail resilient to extreme and fatigue loads should be supported. All offshore WECs will benefit from this development. As part of the above study, the design of the means of connecting subsea dynamic cables to WEC devices should also be considered; either along mooring lines or as a separate system. The connector for the cable should also be considered and it is recommended that the search for a standard connection design should be supported. A series of mooring studies for the major different types of Wave Energy Devices would provide useful generic information; essentially a technology and cost audit of leading WECs. The costs associated with laying anchors and mooring lines (site investigations, marine operations) represent a high proportion of project capital expenditure. For prototype testing, these one off costs are prohibitively high. A WEC test site would encourage prototype testing. In addition, current numerical modelling techniques for motion predictions of individual units are good, but for arrays of floating devices are limited. Software should be developed to improve this as the expected configuration of offshore WECs will be in groups of devices Conclusions and Recommendations Mooring systems used in current WEC designs are mainly conventional systems, such as a catenary or angel and sinker. They use chain or wire with concrete gravity blocks or a pull in anchor. The major conclusions of this sector are: Great potential for transfer of technology exists from the Offshore Industry to the Wave Energy Industry. Particular reference should be made to recent developments in the use of synthetic ropes and taut moorings. Generic studies are recommended into the following Key Technology Issues; long term fatigue issues of lines and connection points, standard connector designs for the quick release and re-attachment of mooring systems and subsea cables. A series of mooring studies for the major different types of Wave Energy Devices would provide useful generic information; essentially a technology and cost audit of leading WECs. Software development is recommended in the area of predictive modelling of the motions of arrays of devices in a given sea-state. Page 25

31 4.4.5 References [4.1] Single Point Moorings of the World, Halyard Offshore, OPL, Oilfield Publications Limited. [4.2] Deepwater Fibre Moorings; An Engineers Design Guide, Noble Denton, OPL, Oilfield Publications Limited. Page 26

32 4.5 Operations and Maintenance Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: How to Keep Operational Costs Down? Potential for Technology Transfer Development of a maintenance strategy sufficiently robust to withstand minimal routine maintenance and plan for major refits as required is a goal of all WEC teams. This technology area can be addressed largely by transfer of knowledge and technology from the offshore oil and gas industry. To achieve the above target, the WEC operational strategy and design criteria should be: Design for Unmanned Operation Design for Zero Maintenance Design for Long Distance Performance Monitoring Design for Annual Inspections (or less frequent inspections) in calm weather periods If major refits are required, affected parts of the device should be retrieved, returned to shore and replaced. These criteria are similar to the design criteria for unmanned offshore oil and gas facilities, notably subsea installations, buoys, tanker offloading systems and notnormally-manned installations. For inspection and light maintenance activities, Diving Intervention and Dedicated Remote Operating Vehicles (Figure 4.5) can be considered, but costs are high, safety issues would need to be addressed, and use should be limited to annual inspections or less often. It follows that the vessels, operational strategies and material selection used for these facilities may also be relevant for the design of the WEC schemes. The MET office can offer predictions of suitable weather windows and past data for the preparation of O & M procedures of wave energy devices. Five day weather predictions are offered by the MET in support of operational and installation decisions. A desk study is recommended to describe how the offshore oil and gas industry currently undertakes inspection and monitoring of subsea or unmanned floating or fixed facilities, maintenance and repair (for example how change out operations are performed for subsea units). This would also include a list of contacts in this industry for suppliers of technology and services of this nature Generic Research and Development Needs No generic technical needs have been identified; operational strategies will be very dependent on WEC device types. Page 27

33 As discussed in Section 4.3, Marine Operations, WEC Design Operational Strategies should be prepared in consultation with Vessel Operators and designs should be selected which minimise maintenance, inspection and repair activities Conclusions and Recommendations The major conclusions of this sector are: Great potential for transfer of technology exists from the Offshore Industry. No generic technical needs have been identified; operational strategies will be very dependent on WEC device types. A desk study is recommended to describe how the offshore oil and gas industry currently undertakes inspection and monitoring of subsea or unmanned floating or fixed facilities. Page 28

34 4.6 Materials Key Technology Issues The following issues were identified as a result of industry interviews and from the Technology Workshop: What Corrosion Strategies can be considered? How to achieve a balance between low cost and high performance materials? How to carry out Life Cycle Analyses? WEC teams made the following additional requests during the workshop: Information on trends in reliability of materials. Erosion of rust due to wave action and water-borne solids Potential for Technology Transfer The opportunity exists for the technology and experience gained from the offshore oil and gas industry to benefit the WEC teams. The performance of the two most commonly used materials (steel and concrete) likely to be utilised by the WEC industry for the main structure in the offshore environment is well understood. In component manufacture, more exotic materials are more likely to be relevant, and here again, current industry experience should be exploited. Primary material producers, e.g. Corus in the case of steel or Avesta Sheffield in the case of stainless steels, are good and reliable sources of information. Technology transfer in the form of either material processing or manufacturing technology or proprietary products may prove to be beneficial, e.g. the wind energy industry is currently adopting the use of a product known as Bi-steel, produced by Corus, which may have potential in wave energy devices. Corrosion Strategy Corrosion strategies for the protection of steel can be prepared on the basis of well proven predictive methods and reliability data. Strategies [6.1, 6.2] can involve: Coatings, Cathodic protection Corrosion allowances, Adopting more corrosion resilient alternatives, or A combination of the above However, it should be noted that corrosion protection control with respect to conventional offshore structures is based upon service life requirement of 20 to 30 years. For structures with longer lives the approaches given in the references may need modification. Concrete is highly durable in the marine environment as long as adequate cover is included in the design and quality control procedures are maintained throughout the construction process. This is demonstrated by the concrete substructures used by the oil and gas industry. Usually, no additional maintenance or repair is required. Page 29

35 WEC teams are currently concentrating on proving prototypes with relatively short design lives. Accordingly, corrosion resistance is not a high priority. This will, however, become of greater importance during WEC Power Station development. Balance between Low Cost and High Performance Materials Achieving this balance is the goal of all designers. The most fruitful way of achieving this is to consult relevant materials specialists and suppliers who are able to predict behaviour and refine designs and operational strategies in consultation. Life Cycle Analysis Life cycle analysis or life cycle costing is increasingly becoming a key driver in material selection, and is an issue that successful designs cannot ignore. In very simplistic terms it enables an appropriate balance to be achieved between capital and operational costs of materials within the design process. The importance of life cycle costing in the design process has been internationally recognised through the publication of an ISO standard, [6.3]. It is understood that work is in hand drafting a specific part of the ISO standard which deals specifically with maintenance and life cycle costing, but the likely publication date is unknown. The methods of Life Cycle Costing are well established and can be readily applied to WEC schemes. Reliability of Materials (trends) Reliability performance of materials in particular application can be gained directly from primary materials producers. Alternatively, specific data can be sourced from OREDA [6.4]. Erosion Damage Some erosion damage has been reported in association with turbine blades used in OWCs. This is assumed to be the result of water droplets entrained in the air stream passing through the turbine impinging on the blades. This issue may be addressed through technology transfer. Generic Research and Development Needs A huge range of materials with widely different properties are currently used everyday for applications in offshore environments. The development of new materials for the WEC industry in isolation is not considered necessary Conclusions and Recommendations The major conclusions of this sector are: The opportunity exists for the technology and experience gained from the offshore oil and gas industry to benefit the WEC teams. A reliability data library and contact database should be set up to include materials data and suppliers of materials likely to be instrumental in the development of WEC schemes. No generic research and development work is recommended. Page 30

36 4.6.4 References [6.1] NACE RP Corrosion Control of Fixed Offshore Platforms Associated with Petroleum Production. [6.2] DnV RP B401, Recommended Practice Cathodic Protection Design, [6.3] ISO 15686: Building and Constructed Assets Service Life Planning General Principles. [6.4] Offshore Reliability Data Handbook, 3 rd Edition, OREDA Participants, Page 31

37 4.7 Hydraulic Systems Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: Hydraulic fluids Hydraulic fluid containment is an issue for performance and environmental reasons, as oil based fluids might leak. Power conversion and transmission There did not appear to be any consensus on the question of hydraulic power conversion. Each team appears to be pursuing its own concept and the designs are quite disparate. Questions may arise in the future as to which concepts should be progressed towards commercialisation and how the potential viability of such concepts should be evaluated prior to significant levels of support. System integrity Long term survival and response to extreme environmental events was recognised as a potential problem for the majority of WECs using hydraulic power takeoff Potential for Technology Transfer Hydraulic fluids If oil is used as a medium, containment must be the priority. The performance and durability of dynamic hydraulic seals is currently seen as a problem. Whereas static seals are widely used in many applications and high standards are achievable, the performance of dynamic seals depends on a number of factors, including distance and velocity of travel, quality and retention of surface finish, and the cleanliness of hydraulic fluid and the surrounding media. The potential for technology transfer is likely to be limited and may come from areas where maintenance is highly restricted, e.g. offshore engineering. Power conversion and transmission Component parts of hydraulic systems are already widely used in many industries. Wave power requires an element of role reversal. Hydraulic rams, used typically as actuators in industry, will be required in wave power, in one configuration or another, to act as pumps. Rotary hydraulic machines, used more commonly as pumps in industry, would be required by wave power to act solely as motors. The opportunities for technology transfer may be application specific, taking into account such facts as speed and torque capacity, controllability, part load performance and efficiency. Rectification generally takes place in hydraulic systems through the use of non-return valves. Throttling losses in such devices may detract from efficiency, especially at part load. Development of alternatives could be of value. Material choice will be Page 32

38 relevant should designers opt for water-based hydraulic fluids if longevity is to be achieved and performance maintained. Published literature suggests that hydraulic accumulators suitable for wave power duty for multi-wave storage are likely to be very costly. Some form of short term energy storage (intra-wave) is nevertheless essential if fluctuations in hydraulic pressure are to be avoided during the power generation cycle. Compressed gas offers the most obvious basis for workable hydraulic accumulators. Issues likely to arise are containment, sealing, choice of fluids and the provision of a suitable gas-liquid interface. There could be some benefit in linking clusters of devices together and combining their outputs in common generation systems. System integrity Corrosion, erosion and protection of working metal surfaces in an aggressive environment are important for long term survival. Hydraulic use in other industries has shown long term performance and reliability depend on low rates of wear of fundamental hydraulic components and seals and long life hydraulic fluids. These in turn tend to be dependent on velocities and distances of travel. Maintainability is a problem. There was general recognition that maintenance intervals should be as long as practicable and that the practicability of maintenance of devices at sea is highly problematic, if not impossible. Designs should therefore allow for shore based maintenance at the concept stage. Survival in the extreme event takes two forms: the end stop problem of hydraulic rams exceeding their design travel the high forces imposed during extreme events, especially if linear devices are designed with limited travel. There is a generic problem which relates to the application of fender type systems to absorb energy and reduce forces at the end stop problem. All such mechanical devices require similar systems and the transfer of technology from the fendering industry could be investigated Generic Research and Development Needs Hydraulic fluids The workshop participants recognised the theoretical benefits of fresh water or seawater as a hydraulic fluid. This is not well established although the difficulties in using water and water based fluids seemed to be well recognised. It was suggested that leakage rates using water based fluids could exceed those for high viscosity fluids one thousand-fold. Specific sealing problems included temperature, pressure, speed, size, cycling and deposition of solids. Dynamic seal performance is currently not well understood. There is a specific requirement for the testing and development of suitable materials for long term dynamic sealing for wave energy applications. Power conversion and transmission In line with the published literature, little interest was shown at the workshop in remote hydraulic power transmission. It was generally considered that any potential benefits would be outweighed by the disadvantages of long and costly pipework systems, pressure losses and the potential for water hammer. Page 33

39 Because of the specific requirements of WEC systems it may be necessary in the long term to develop a whole new family of hydraulic devices to cope with these. The part load performance of existing hydraulic systems must be investigated Conclusions and Recommendations The major conclusions of this sector are: Static seal technology is well advanced. Dynamic seal technology needs to be developed. The use of oil as a hydraulic fluid is well established technology. An elegant and environmentally friendly solution would be to use water as the hydraulic fluid, but considerable research will be required in this area to achieve adequate seal effectiveness here. The component parts for a WEC prototype with a hydraulic take off mechanism already exist. Technology should be transferred from other industries to facilitate prototype development. For full scale WEC power stations with a longer design life than a prototype development work is required to improve reliability and economic returns. To prepare for WEC Power Station deployment in the medium term, the following research and development activities are recommended: Dynamic Seal development and testing is undertaken to extend the design life of a system. A study of the potential for the Fendering industry to mitigate the end-stop problem. Development of hydraulic machines (motors with low part load losses, high torque pumps). Development of systems using water as the hydraulic fluid. Page 34

40 4.8 Pneumatic Systems Key Technology Issues The following key issues were identified during the Industry Interviews and at the Technology Workshop: Turbine development Reliability and Maintainability Self rectifying air turbines are used in all OWCs, but which type is the best? There is limited data available on the long term performance of Wells Turbines (Figure 4.6) Potential for Technology Transfer Turbine development This type of system is rather specific to WEC devices so there are not many other industries which could contribute here. The design and fabrication of turbine blades using novel materials could be transferred from the aircraft industry. Reliability and Maintainability Benefit may be derived from the Wind Energy Industry in generic matters such as value engineering, long maintenance life and, from future offshore wind developments, resistance to aggressive environments and electrical connections Generic Research and Development Turbine Development Initial experience of pneumatic transmission is with the Wells turbine in single row configuration. This technology has been demonstrated and shown to work in several locations worldwide. Recent developments of the concept include twin rotor machines and the use of guide vanes. Alternatives to the Wells turbine which are near demonstration are reported to include a self rectifying design of impulse turbine and a variable pitch aerofoil turbine. There is little information available on the mechanical efficiency of the basic Wells configuration or the potential benefits of the more highly developed versions. It is therefore not clear at this stage whether there would be economic merit in developing the concept further on account of uncertainties over: the improvements in efficiency potentially available the likely demand for onshore devices, which are site specific and probably unsuitable for large scale implementation on account of visual intrusion and acoustic disturbance. These devices may therefore be limited in their potential for large scale development but will be a means of raising the immediate profile of wave energy. Interest was however expressed at the Workshop in the comparative testing of different types of turbine and improvements in durability in respect of bearings and blade erosion of high performance aerodynamic machinery in marine environments. Page 35

41 4.8.4 Conclusions and Recommendations The major conclusions of this sector are: Pneumatic turbines are most suited to operation in an at shore WEC (rather than near shore or off shore). At shore WECs are a maturing technology although a few areas for development do still exist. It is recommended that a series of turbine trials be undertaken in one facility to test the various turbines and their efficiency. Page 36

42 4.9 Subsea Cables and Connectors Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: How to select and install cables and connectors at low cost? Can cables be used with flexible moorings? Cables, Connectors and their Installation are generally high cost items. How can this cost be reduced? Buoyant Moored and Hinged Contour WECs may require a flexible power connection. What is established practice for use in these circumstances? Reliability and Maintenance Design Life and Reliability of Cables will significantly affect overall WEC project costs. This is not a technology area developed in detail by Wave Energy Teams to date. They generally believe the technology essentially exists and the major barrier is its cost. Most hope that sponsorship can be gained for offshore prototype schemes for the relatively short distances required to prove the prototypes. In the longer term, it is hoped that economies of scale will result in overall project cost reductions per unit power generated. Many hope that prices will also fall following standardisation and mass production of subsea connectors and the expansion of offshore wind and WEC Power Stations Potential for Technology Transfer There is considerable potential for transfer of technology from both static and dynamic cables and subsea/ wet matable connector experience in the offshore oil and gas industry. Cable and Connector Selection and Cable Laying - Cost Issues The Power Transmission Industry and the Offshore Oil and Gas Industry has laid static high voltage cables subsea to provide power to isolated communities and offshore platforms and facilities. Typically, these are laid by dedicated cable laying vessels and a typical lay rate of 5km/ day can be expected. More recently, the Offshore Oil and Gas Industry has also developed dynamic cable technology which will be extremely attractive for WEC schemes as they move offshore. Cable selection and WEC scheme location needs to take account of the following general guidelines. The process of cable laying makes up a significant part of the total cost. The vessel used is an important consideration; it should be selected in consultation with an experienced operator. Typical considerations are: Weather This is affected by the location and the time of year. A large vessel will have a higher day rate than a smaller vessel. However, the larger vessel will be able to operate in more extreme sea states and will have less down time from weather than a smaller vessel. This increased productive use of paid Page 37

43 time can make a larger vessel more economic than a smaller one. Cable quantity The required deck space for the cable increases with the cable length and the minimum bend radius. Water depth A deep water depth creates a high tension in the cable as it is laid and hence increases the required vessel buoyancy. Seabed conditions A cable damage assessment and seabed investigation will be carried out and protection for the cable chosen (exposed, covered or buried). Depending on the type of protection and seabed conditions, Dynamic Positioning (DP) may be required or a Remote Operating Vehicle (ROV). An ROV will be required to avoid freespans if seabed contours suggest that this may be likely. Current regime Both tidal and dominant currents are factors. It is possible to lay cables in currents up to 4-5 knots near the seabed. Static cables are significantly less expensive than dynamic cables so should be used over long distances. Dynamic cables should be considered for connecting a floating offshore WEC scheme to the seabed or to each other (if appropriate). To give an idea of the state of the art; in 1996, the Troll Platform in the Norwegian Sector of the North Sea was connected to shore via a static AC cable; 20MW power, 67km length at 52kV. The cable contains 3No. core 240mm 2 cables and is protected by an XLPE lead sheath (Figure 4.7); in the vicinity of the Asgard platform dynamic supply cables have been installed for the heating of pipelines. The cable contains 4No. core 1600mm 2 cables at 12kV and has 210mm outer diameter and unit weight 135kg/m (Figure 4.8); dynamic cables have been designed for up to 90kV voltage level. Dynamic cables have been installed in up to 400m water. Lower voltage cables are less expensive to fabricate. However, lower voltage cables experience greater percentage electrical losses. 3 core AC submarine cables can be used up to km route length. Beyond this, percentage losses or project costs become unacceptable. Polymer insulated submarine cables can be used up to 145kV voltage level. A wet design philosophy may be used up to 36kV. Above this voltage, radial water blocking is required and connector costs increase. Shorter Cables are less expensive, but since a large component of the cost will be for mobilisation of a vessel, the laying of a short length of cable may well be similar in cost in the laying of a long one. Key factors which influence the costs are vessel availability, seabed material, current regime, weather, cable size, water depth and beaching. Cables can be buried on a sand bed using water jets which avoids the need to excavate a trench. Cables lade on a rock bed must be buried by rock dumping. Connectors increase in cost with size and the need for protection from water ingress. All connectors for small WECs will need to be of the wet rather than dry type. The cost of connectors is high although a significant part of this cost is associated with the marine operations rather than the material and fabrication costs. Connectors currently in use are over-specified from the point of view of a WEC. Typically a connector for an oil and gas project is designed to be fitted underwater by a ROV. There is potential to rewrite this specification for use with WECs and reduce the price. Page 38

44 Use with flexible moorings systems Flexible connections are widely used in the offshore industry. A good example is shown schematically in Figure 4.9. It is important to consider the cabling in the mooring analysis and to ensure the connector rigidity is less than that of the moorings. Heavy cables can affect device behaviour significantly, especially if the device is small and lightweight. They will cause the WEC to attract additional drag, and in extreme cases additional buoyancy may be required on the WEC. Flexible moorings are usually used in deep water (greater than 60m), if they are used in shallower water the cable may experience significant wear at the seabed. Specific protection with bend restrictors needs to be designed here. Reliability and Maintenance Properly designed and maintained dynamic and static cables are now extremely reliable. Alcatel, for example, claim a failure rate for all their cables as 0.18 faults per 100km per year. The major cause of faults is damage by accidental anchoring or fishing vessel clashes. Other hazards are damage during installation, icing, seabed clashes, and over-voltage. Most of the above can be mitigated by good design and adherence to construction and operating procedures. Increased reliability can be achieved by keeping cables buried in the seabed, dumping rocks over the cables where embedment is not possible and by inspection and monitoring at regular intervals. Static cable repairs would be attempted by replacement of the damaged section. Dynamic cable lengths would be replaced not repaired Generic Research and Development Needs The only generic research and development project identified as being potentially valuable for the wave energy industry as a whole is: Development of a standardised, flexible connector. Currently cables and connectors used offshore are bespoke designs. Standardisation would help to reduce the currently very high prices of these elements. This type of connector would be valuable both for floating wind and wave devices as they move offshore. However, suitable connectors exist already and although expensive, can already be used for WEC prototype proving Conclusions and Recommendations The major conclusion of this sector is: There is considerable potential for transfer of technology from experience of static and dynamic cables and subsea/ wet matable connectors in the offshore oil and gas industry. No technical barriers to prototype development exist but costs are still very high for cables and connectors. To reduce these costs study work is recommended to develop standardised, flexible connectors by revising existing specifications for Oil and Gas facilities. Page 39

45 4.10 Control Systems Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: System control Optimisation of power take off and survival in Remote control and monitoring extreme events are key features of any WEC. Because of the extreme or remote conditions at the WEC, it is often desirable to monitor or control it remotely. System reliability The measurement and control systems need to be highly reliable and have minimal maintenance requirements Potential for Technology Transfer System Control The broad range of WECs under development have many different control inputs, outputs and system requirements. This means that system control is not really an area which lends itself to generic consideration. Once WEC systems have been developed and a control system is in place, it is recognised that improvements in efficiency can be realised by the optimisation of control strategies. To determine the best control strategy simulation and modelling will be required. The majority of control system companies have skills in developing advanced control algorithms and some have the facilities for basic simulation. There are also specialist simulation companies offering comprehensive simulation services but these tend to be expensive. Control strategies have primarily been developed by the wave energy device teams themselves and/or in universities. The use of proprietary systems offered by industry may offer the advantages of flexibility and faster reconfiguration times, since they use more highly developed, higher level configuration tools. These facilities, in combination with telemetry, may prove very useful during development stages. Remote control and monitoring WEC schemes need the ability to monitor the status and performance of the WEC and possibly remotely control some tuneable parameters. During development, the ability to experiment with different control schemes (strategies) and reconfigure or download software may be required. Proprietary systems to help do this already exist. The most obvious areas for technology transfer are in SCADA and communications systems. Communications technology has become cheaper and more widely used since there is a more established infrastructure. Satellite communications, for example, is much more commonplace. System reliability All WEC devices will need to be reliable and have minimal maintenance strategies. Control and Instrumentation systems employed in the petro-chemical industry (not just offshore oil/gas) have been developed to have high levels of availability. They achieve this by various designs, but self diagnostics and auto testing techniques are widely used to warn of critical failures before they happen. Page 40

46 Equipment packaging and protection will also be important for improving reliability. Systems are available that can be fitted within enclosures which are sealed against the environment. These vary from weather protection to fully submersible systems. Subsea controls and measurement have developed most rapidly in recent years, although this technology is probably still too expensive to be directly useful Generic Research and Development Needs System Control The area which still needs research and development is the modelling and simulation of the proposed devices. This is so device specific that it is best done by WEC teams individually and is not an area for generic research. The issue of modelling and forecasting the wave input on a real time basis still needs to be addressed Conclusions and Recommendations The major conclusions of this sector are: Great potential for transfer of technology in the key technology areas of system control, remote control and monitoring and system reliability from the offshore oil and gas and petro-chemical industry exists. The facility to remotely reconfigure a WEC control scheme will be particularly useful. Device specific system response modelling should be carried out by individual device teams. Research into real time forecasting of detailed wave time behaviour is recommended References The Institute of Measurement and Control The Instrumentation, Systems and Automation Society 87 Gower St, London, WC1E 6AF. Page 41

47 4.11 Power Quality and Grid Connection Key Technology Issues The following key issues were identified as a result of the Industry Interviews and at the Technology Workshop: Grid geography Grid Connections Supplying Isolated Communities Fault Condition Management WEC teams have requested information on areas of demand, supply and connection points. They have also identified significant hurdles in the planning and approvals process. Connection to the grid requires standards of power quality to be met. This impacts on the generator type, control, and energy storage requirements Such problems have been encountered in connecting to the grid that the supply of isolated communities has been perceived as a potentially more suitable proving ground for individual WEC prototypes. This concerns protecting the grid from faults on the device, and protecting the device from faults in the grid Potential for Technology Transfer National Grid Geography Technology transfer from the Grid companies and Wind Energy Industry on this issue can assist WEC teams greatly in the short term. There is, however, a clear mismatch between demand and supply in the areas where the wave energy resource is greatest. The inevitable result of this is inadequate distribution capacity in these areas. A further effect is the potential for reverse power in the distribution system which cannot be accepted without modifications, both technical and in operating procedures. There is a wider issue of infrastructure development here which is beyond the remit of this study but needs to be considered for the development of natural energy sources in general. No map has yet been published of the location of suitable grid connections for significant attachment of wave generated electricity to the public system. The Scottish Executive is currently looking to update their 1993 Renewable Energy Report which identified on a geographic basis across Scotland the network capacity to accept new sources of electricity generation. In addition, the problem is being investigated by the DTI working group on Network Issues. WEC teams have found the process of connecting to the grid to be expensive. However, grid companies have suggested that for the small sizes of generator (below 0.5 MW) currently under development there will be locations where a relatively low cost connection is achievable. Co-ordination between WEC teams and grid companies is recommended during scheme planning. Page 42

48 Very high capital costs were quoted at the Technology Workshop for sufficient grid upgrades to permit the export of a significant quantity of wave generated electricity from the West Coast of Scotland to England. The only realistic driver for such upgrades is a real and substantial increase in the demand for renewable electricity in combination with the technology demonstrated at a prototype level. Currently, the attachment of prototypes is handled on a case by case basis. An assessment of the power quality which is acceptable to the grid Operator and the WEC Operator is established and a maximum power level agreed taking account of demand on the grid and the supply reliability. The wind industry has considerable experience of this problem and the potential for receiving advice from these other industries should be explored. The procedure is currently highly complicated and very dependent on the weakness of the grid in the most remote areas of the country. Efforts need to be made to streamline these discussions and it is recommended that one part of the grid be upgraded to readily accept these prototypes and to utilise the energy produced from them. It is recommended that the grid operators need, where possible, to promote the changes which facilitate the attachment of renewable energy devices to the grid. A study is recommended to identify the optimum location for testing of future prototypes. This will need to involve renewable energy teams and the grid operators. Supplying Isolated Communities The cost and complexity of grid connection has led to the suggestion that wave energy devices may, at least initially, be better suited to supplying isolated communities. Isolated communities are really only suitable for small scale deployment of prototypes as the local grid is usually dated, small and incapable of absorbing large amounts of power. However, as long as the power needs of the community are compatible with the prototype WEC device output, and back-up generation systems can be brought on stream during prototype testing, this may be a more fruitful course of action. A study is recommended to identify whether this is indeed the case and, if so, which communities would benefit or be interested in being involved. Fault Condition Management There exists a large amount of experience with the electrical utility regarding dealing with embedded generation related to the wind and hydro industries. No further study is therefore recommended Generic Research and Development Needs Grid Connections The issue of grid interfacing is common to all WEC schemes as well as other intermittent sources. Power quality was recognised as an issue. It was suggested that there is a technical limit to the proportion of conventional asynchronous generation that can be accepted by the system. There is a requirement for the grid operator to determine the capability of the local grid to accept such irregular generation. Alternative generator types may involve power conditioning at the point of generation. Power electronics systems for such conditioning are available and the adaptation to WEC use needs investigation. Energy storage is a generic issue for Renewables generators, although the demand for storage may be greater for wave energy than for other renewable sources. Storage Page 43

49 may take numerous forms and work is at various stages of development. Recent publicity suggests that chemical storage is close to commercialisation whereas the development of a hydrogen economy is probably a long way off. An interesting footnote to the question of storage is that in circumstances that electricity is used wholly or partially for desalination, the issue of electricity storage falls away. Ongoing work into the development effective storage devices is therefore recommended. Fault Condition Management Some WEC teams have experienced high grid connection costs which are apparently driven by grid fault conditions. There is a need to investigate the potential for fault detection and effective intervention strategies in the grid. Study work is recommended to achieve this Conclusions and Recommendations The outstanding issues in this area are, in general, generic to the generation of electricity from intermittent sources of renewable energy and a function of the UK grid being least capable of accepting near sources of energy in its least robust sections without significant upgrading. The major conclusions of this sector are: A grid map needs to be provided for the west coast of the UK so that potential WEC developers can identify the most suitable sites for future connection of devices. A study of the grid capacity with a view to recommending areas for upgrading in the vicinity of the more suitable locations for WEC development is recommended. The study should involve WEC operators (who can provide input on wave climate and device characteristics) and grid operators (who can provide input on grid topology). This to be included in a study to identify the best places for establishing a centre for standardised proving of WECs. Some generic areas for future R & D are recommended: 1. Testing and development of power conditioning modules for use in WEC systems is recommended. 2. Ongoing research into effective means of storing the energy during downtime is recommended. 3. Technology for the remote monitoring of faults should be studied and intervention strategies should be formulated. Page 44

50 5. CONCLUSIONS AND RECOMMENDATIONS 5.1 Conclusions The Wave Energy Industry is not co-ordinated All the WEC teams are relatively small. They are either university research departments or in two cases SMEs. Consequently, the speed of progress is slow towards development of first WEC prototypes and ultimately WEC power stations. It is apparent from the current study work that many disciplines are involved in the design and construction of a WEC prototype; it is not realistic for such small teams to cover the breadth of knowledge required. At present, all teams are working independently and commercial considerations force them to keep their ideas secret. This secrecy compounds the slow progress and delays any return on their good ideas Technology used in the Offshore and Other Industries can be transferred to the Wave Energy Industry. There are no major technological barriers to the deployment of a WEC prototype device. All of the operations of a WEC scheme (design, construction, transportation and installation, inspection, maintenance, repair and removal) have been developed in the offshore industry. Some WEC components still require refinement, but this is anticipated to be carried out during prototype development and is normally device specific. Significant opportunity for transfer of costing information and methods exists from the Offshore Oil and Gas, Onshore Civils and Manufacturing Industries. However, notice should be taken of the differences between wave energy devices and offshore installations within these cost estimates. Most offshore oil and gas projects are prototypes with a complete design process applied to each project. Wave energy projects are not considered viable if this approach is adopted here. The returns on investment are much lower. The wave energy industry should endeavour to select costs and technology gained in the offshore oil and gas industry, but, at the same time, to realise economies of scale and repeatability of design to keep costs down. The study has identified those issues within each Key Technology Area faced by the Wave Energy Industry that have already been largely developed by the Offshore or other Industries There are areas where generic research and development would be useful Technology gaps were identified where generic research and development would be beneficial (see Key Technology Area in Section 4). In general, these would not prevent deployment of prototype devices. However, the majority of these issues should be addressed for the development of a WEC power station There is a lack of investor confidence in the industry Investment in Wave Energy is very small. The Wave Energy Industry received less support in the last ten years compared with other Renewable Energies. The device Page 45

51 technology is perceived as being far from commercial realisation, carrying a high risk and having a long time scale on return for investors. To date, internationally, there have been no successful long term demonstration projects of the technology There are issues common to both the offshore wind and wave energy industries There are several areas in which the Offshore Wind Energy and Wave Energy Industries have common interests. Typical examples are planning approvals, subsea cabling, mooring systems, operating and maintenance strategies. Amongst these is the development of grid capacity to handle energy produced. 5.2 Recommendations The following actions are recommended to support the wave energy industry both in the UK and the rest of Europe. The recommendations are made bearing in mind the proposed programme of WEC prototype and power station development (Figure 5.1) and the perceived need for further cost reduction Promote co-ordination within the industry An immediate need exists for a co-ordinating body, similar to the Offshore Wind Energy Network ( or the British Wind Energy Association ( This should be responsible for setting up of an internet based information service (for example to transfer contacts, knowledge and technology, to transmit technical and commercial data, provide a forum for the sharing of ideas and developments and to assist in design decisions for the development of WEC prototypes and power stations. This will require the input of all WEC teams, technologists, consultants, operators and suppliers. The following urgent study work to support the development of an internet based WEC information system needs to be undertaken and maintained on a regular basis: References of previous technical work on Wave Energy to be compiled. This to include UK and international work on WEC and related technologies. Costing Database and Industry Guidelines for Construction, Installation, Operation and Maintenance activities of future WECs, (also relevant to offshore wind). Contacts List of interested parties; WEC design teams, operators, verification bodies, contractors, suppliers, technologists in WEC development or in related technologies. Reliability Database References; sources of information for construction materials and equipment. This activity could be linked in with the European Commission s WAVENET project Transfer of Technology The following technology transfer studies are recommended to support WEC teams and to feed the proposed web site. Several issues were identified in Section 4 as having potential for technology transfer. Page 46

52 Recommendations for WEC Prototype Deployment Offshore Industry guidelines on the use of appropriate structural design codes and verification. Offshore Industry guidelines for construction and marine operations planning. Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion. Oil and Gas Operator s Metocean data for identification of tow and installation weather windows. Grid company information on the best locations to connect WECs to the electrical grid. Offshore oil and gas industry inspection and monitoring procedures for remote facilities. Recommendations for WEC Power Station Development Use of synthetic ropes and taut moorings. Proprietary systems to reconfigure or download different control schemes (strategies). Self diagnostics and auto testing control schemes. The use of proprietary systems to optimise control strategies. SCADA and communications systems Implement generic research and development The following generic R & D studies are recommended to support WEC teams and to feed the proposed web site: A study to identify the potential locations for a prototype test facility for connection to the electrical grid. Input will be required from WEC teams and grid companies. A study to identify the capacity of the grid at specific locations identified above. Investigation into the potential for fault detection and effective intervention strategies in grids. Testing and development of power conditioning modules for use in WEC systems. A series of mooring studies relevant to the different types of WECs. Generic mooring detail studies; long term fatigue issues of lines and connection points, standard connector designs for the quick release and re-attachment of mooring systems and subsea cables. A series of turbine trials undertaken in one facility to test the various turbines and their efficiency. Enhanced modelling techniques for systems involving multiple devices. Research into real time forecasting of detailed wave time behaviour. Development of hydraulic systems based on water or other environmentally acceptable fluids. A standardised, flexible electrical connector. Research and development to continue to drive down the costs of cable and connector fabrication and cable laying. Development of hydraulic machines (motors with low part load losses, high torque pumps). Storage of energy. Page 47

53 5.2.4 Build investor confidence by proving the technology Investment is required to enable WEC teams to demonstrate the technology as soon as reasonably practicable. Successful demonstration will generate future investor confidence and industrial support. Governments (both individual countries and European) and Industry (Wave, Offshore Oil and Gas companies and onshore Fabricators/ Manufacturers) need to combine together in a co-ordinated funding programme in support of the proving of WEC prototypes. The government needs to support the creation of an environment which encourages the increased co-operation and organisation between device teams. Once developed, WEC Prototypes need to be compared and proven in a standardised wave environment in order to attract investment. Prototype demonstration will also assist in making well-informed decisions on the development of Offshore WEC Power Stations. However, a decommissioned oil and gas facility could be appropriate as an offshore WEC prototype proving base; such as the shortly to be decommissioned Phillips Maureen Articulated Loading column (Figure 5.2) The Offshore Wind and Wave Energy Industries should work together Efforts need to be made to identify generic efforts which would benefit both the offshore Wind Energy Industry and the Wave Energy Industry; e.g. subsea cabling, mooring systems, operating and maintenance strategies, grid connection. Combining funding programmes will lead to more efficient use of funds. There is potential to combine the power transmission from an offshore wind farm and a WEC. Multiple schemes could share a transmission cable, distributing the high overheads of cable laying amongst several parties. The Planning and Approvals process for at shore and near shore WEC schemes should benefit from the recent work carried out by the Wind Energy Industry. The approvals process for WECs requires clarification and a study, similar to the one carried out in Ireland should be commissioned. Official bodies who grant permission for the deployment of WECs should be encouraged to co-ordinate themselves now to streamline the planning approvals process. A study is required to assess the work required to upgrade the grid to handle large numbers of renewable energy devices Recommended Priorities The immediate priority of the Wave Energy Industry should be to direct government and industry resources towards successful deployment of successful prototypes. Devices closest to the market should be supported to achieve this goal. Industry co-ordination: immediate priorities An internet based information service should be established. Study work should be funded to support an internet based information service, containing: References of previous technical work on Wave Energy. Costing database and industry guidelines Page 48

54 Contacts List of interested parties. Reliability database. Efforts should be made to align the Wave Energy Industry with the Wind Energy Industry as they move offshore. Prototype deployment: immediate priorities Technology transfer study work should be funded in the following areas: Offshore Industry guidelines on the use of appropriate structural design codes and verification. Offshore Industry guidelines for construction and marine operations. Operator and Design feedback from the recently developed West of Shetlands Fields would be beneficial; i.e. BP Foinaven and Schiehallion. Oil and Gas Operator s Metocean data for identification of tow and installation weather windows. Grid company information on the best locations to connect WECs to the electrical grid. Offshore oil and gas industry inspection and monitoring procedures for remote facilities. Some generic research and development aimed at prototype deployment should be funded: A study to identify the potential locations for a prototype test facility for connection to the electrical grid. Input will be required from WEC teams and grid companies. A study to identify the capacity of the grid at specific locations identified above. Research and Development for the Longer Term In addition, during the next five years generic research and development activities described in the previous section should be supported to address the issues which will be faced when WEC power stations are deployed. Some of these issues will require long term effort; study work should therefore begin at the earliest opportunity if solutions are to be found which meet the target programme. Page 49

55 6. FIGURES Figure 3.1 WEC Type 1: Buoyant Moored Device Figure 3.2 WEC Type 2: Hinged Contour Device Figure 3.3 WEC Type 3: Oscillating Water Column Figure 3.4 Oscillating Water Column Chamber of LIMPET Figure 3.5 Pelamis 750kW device Figure 3.6 The Duck Figure 3.7 PS Frog Mark 4 Figure 3.8 Sperbuoy Figure 4.1 Favoured Wave Energy Locations Figure 4.2 Construction and Installation Options Figure 4.3 Concrete Offshore Platform Dry Dock Construction Figure 4.4 Installation and Deballasting of Subsea Oil Tank Figure 4.5 Subsea Remote Operating Vehicle (ROV) Figure 4.6 The Wells Turbine Figure 4.7 Troll Static Cable Figure 4.8 Asgard Dynamic Cable Figure 4.9 Asgard Dynamic Cable Arrangement Figure 5.1 Potential Programme for Development of Wave Energy Schemes Figure 5.2 Offshore Prototype Testing and Proving Facility Page 50

56 Figure 3.1 WEC Type 1: Buoyant Moored Device Page 51

57 Figure 3.2 WEC Type 2: Hinged Contour Device Page 52

58 Figure 3.3 WEC Type 3: Oscillating Water Column Page 53

59 Figure 3.4 Oscillating Water Column Chamber of LIMPET Figure 3.5 Pelamis 750kW device Page 54

60 Figure 3.6 The Duck paddle P G waves 10 m stem moving mass P G stem 'weight' Figure 3.7 PS Frog Mark 4 Figure 3.8 Page 55 Sperbuoy

61 Figure 4.1 Favoured Wave Energy Locations Page 56

62 Figure 4.2 Construction and Installation Options Page 57

63 Figure 4.3 Concrete Offshore Platform Dry Dock Construction Figure 4.4 Installation and Deballasting of Subsea Oil Tank Page 58

64 Figure 4.5 Subsea Remote Operating Vehicle (ROV) (photo by Sonsub) Figure 4.6 The Wells Turbine (photo by Wavegen) Page 59

65 Figure 4.7 Troll Static Cable Figure 4.8 Asgard Dynamic Cable EL. RISER AN D H EATIN G CABLE SYSTEM SID EVIEW Figure 4.9 Asgard Dynamic Cable Arrangement Page 60