Isle of Wight Tidal Stream Energy Technolgy and Test CentreSolent Ocean Energy Centre
The case for establishing an evaluation and research centre for ocean energy technologies
on the Isle of Wight
Report prepared for the Isle of Wight Council
December 2006
Marine and Technical Marketing Consultants (MTMC) Unit 28, Medina Village
Bridge Road Cowes
E-mail: icampbell@mtmc.fslife.co.uk
Table of Contents Foreword Executive Summary 1. Introduction
1.1 Energy targets 1.2 The Isle of Wight as a Centre for Marine Energy 1.3 Solent Ocean Energy Centre
1.3.1 National Significance 1.3.2 Regional Significance 1.3.3 Local Significance
2. Vision and Objectives
2.1 Mission of the Solent Ocean Energy Centre 2.2 Proposed Milestones
2.2.1 Objectives for 2007 2.2.2 Longer Term Timescales and Key Events
3. Marine Energy Extraction
3.2.1 Devices for Tidal Energy Extraction 3.2.2 Tidal Device Developers
3.3 Wave Energy 3.3.1 Devices for Wave Energy Extraction 3.2.2 Wave Device Developers
4. Test Facility Requirements 4.1 Introduction 4.2 Expected Range of Work 4.3 Facility Options and Availability
4.3.1 Towing Tank 4.3.2 Circulating Water Channel 4.3.3 Deep Tank 4.3.4 Sheltered Marine Test Site 4.3.5 Offshore Marine Test Site
4.4 Conclusions and Recommendations for Test Facilities
5. Instrumentation Requirements
5.1 Dynamometer 5.2 General Instrumentation 5.3 Work Boats and Crane Barge 5.4 Electrical Load / Electricity Network Connection 5.5 Conclusions and Recommendations for Instrumentation
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6. Marine Tidal Test Sites
6.1 Introduction 6.2 Requirements for Inshore, Sheltered Site 6.3 Inshore Site Selection and Ranking Methodology 6.4 Candidate Inshore Sites 6.5 Conclusions and Recommendations from Inshore Site Ranking 6.6 Requirements for Deep, Offshore Site 6.7 Offshore Site Selection 6.8 Candidate Offshore Sites 6.9 Conclusions and Recommendations for Offshore Site
7. Proposed Commercial Structure of the Centre
7.1 Business Model 7.2 Technical Support Structure 7.3 Technical Work Management
8. Collaboration
8.1 Strategy for Collaboration 8.2 Potential collaborators 8.3 Networks
9. Regional Infrastructure of Resources Available to the Test and Evaluation Centre
9.1 Introduction 9.2 Intellectual Resource Requirements 9.3 Organisations with Offerings for the Centre 9.4 Descriptions of the Organisations
9.4.1 ABPmer (Marine Environmental Research) 9.4.2 British Maritime Technology (BMT) 9.4.3 Wolfson Unit for Marine Technology and Industrial Aerodynamics (WUMTIA) 9.4.4 HR Wallingford 9.4.5 National Oceanographic Centre 9.4.6 QinetiQ Haslar 9.4.7 Other Organisations
9.5 Individuals and Small Companies with Offerings for the Centre 9.5.1 Small Consultancies 9.5.2 Small Engineering Companies
9.6 Benefits of the Regional Infrastructure 9.7 Conclusions and Recommendation
10. The Case for a Solent Ocean Energy Centre
10.1 Introduction 10.2 Overview of the UK Marine Renewable Energy Market
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10.3 Financial Drivers 10.4 Environmental and Political Drivers 10.5 Global Tidal Energy Sector 10.6 UK Tidal Energy Sector 10.7 Client Base and Value of Work 10.8 Centre Costs
10.8.1 Capital Cost Breakdown 10.8.2 Capital and Set-up Costs of the Inshore Marine Test Site 10.8.3 Cost of the Offshore Marine Test Site 10.8.4 Overhead / Running Costs
10.9 Funding Sources 10.9.1 Public Sector Funding 10.9.2 Private Sector Funding
10.10 Conclusions and Recommendations
Appendices
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Foreword Marine and Technical Marketing Consultants (MTMC) has been commissioned by the Isle of Wight Council to conduct a Feasibility Study into the establishment of the Solent Ocean Energy Centre - an evaluation and research centre for marine energy technologies on the Isle of Wight. Funding for the study has been provided by the South East England Development Agency (SEEDA). Those constituent elements, which would be necessary for the successful establishment of such a Centre, were identified in the initial project proposal, presented to the Isle of Wight Council in February 2006. The objective of the Feasibility Study is to expand comprehensively upon those elements, in order to provide a detailed overview of the resources and facilities that would be available to the Centre for its effective and profitable operation. MTMC was established in 1992 and acts as an umbrella company for a number of individual consultants and small businesses who frequently work together. Providing an integrated technical and commercial service to clients, the company specialises in marine performance evaluation and the design of specialist instrumentation for hydrodynamic testing.
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Executive Summary The government has set ambitious targets for generation of electricity from renewable sources, in order to fulfil its obligations under the Kyoto Protocol. This report sets out the result of a study to explore the feasibility of establishing a Centre for evaluation and research into marine renewable energy technologies on the Isle of Wight, which will underpin the achievement of those targets. The Centre will also contribute to several targets within the SEEDA Regional Economic Strategy, by promoting the Region’s knowledge in marine renewable energy, assisting the development of business consortia for the marine renewables sector and providing infrastructure to maintain international economic competitiveness in the marine industry. The Centre will provide integrated business support, particularly for micro- businesses, which are the core of its recommended business model. It will build on the local strength of marine-related companies on the Isle of Wight (and surrounding SEEDA region), potentially transforming the current low- wage economy into a technology and knowledge-based economy. A comprehensive review of the current state of wave and tidal stream technologies (in which the UK is a world leader) is presented in this report, together with a list of marine energy device developers categorised according to their location in the south of England, elsewhere in the UK or elsewhere in the world. Interviews with a number of these developers confirmed that there is a need for the proposed Centre in the SEEDA region. Cost-effective test facilities are required at all stages of device development, from proof-of- concept, through design optimisation to full prototype demonstration. Facilities for testing and development of ancillary equipment and of installation, maintenance and decommissioning procedures are also needed. Sufficient facilities exist already in the SEEDA region for laboratory testing of small-scale marine energy devices. A key facility is the GKN towing tank in East Cowes on the Isle of Wight, which will support model tests of both wave and tidal generators. A desirable addition would be the upgrading and relocation of a circulating water channel that is currently mothballed on the site of QinetiQ Haslar in Gosport. Some investment in instrumentation will be necessary, but most may be hired and charged to projects. Four candidate sites on the north and east shores of the Isle of Wight have been studied and ranked according to their suitability for a sheltered marine tidal test facility. Further investigations are recommended, prior to final site selection. Two potential deep offshore sites for testing prototype tidal stream generators with grid connection have been identified. Further investigations and consultations are recommended, to select the most appropriate site and to ensure that the application for consents will run smoothly. The cost of site construction and a grid connection for demonstrator devices would have to be
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met from the public purse, which can be justified in terms of strategic government support for development of a predictable form of renewable energy that will contribute to the UK energy targets and security of energy supply. Once established, the offshore site would be financially self- supporting. The commercial structure proposed for the Centre is based on a successful model developed by an informal grouping of Isle of Wight companies, to provide an integrated technical and commercial service to clients. It will only be necessary to establish an office facility with a technical and administrative manager, who could either work from a remote office or could be located centrally on the Island. Administrative services such as website design and publicity will be outsourced. This report demonstrates that there is a wealth of technical expertise residing in companies based on the Isle of Wight and in the surrounding SEEDA region. For each project conducted through the Centre, a group of companies will be selected from this technical resource and subcontracted to deliver the customer’s requirements. The proposed Centre is seen to be complementary to other UK marine energy test centres, such as NaREC, EMEC and Wavehub and there is potential for informal partnering arrangements with these establishments. An overview of the global marine renewable energy market and of financial, environmental and political drivers in the UK demonstrates the commercial opportunities presented by the sector. The UK has a competitive advantage based on its world-leading position in tidal energy technologies, a plentiful tidal resource and strong existing offshore skills. However, there are three main hurdles to achieving the full potential of marine energy generation, namely financing, grid access and planning / permitting. The proposed offshore test site will alleviate the latter two of these problems. Economic analysis shows that it is feasible for the Centre to commence operating immediately, using existing laboratory facilities, with an initial investment of £74k for the first year’s set-up and overhead costs and a desirable investment of £50k for instrumentation. It is recommended that the concept is taken forward at the earliest opportunity and that public funding is sought for the development of an inshore marine test site. Further investigations should be conducted to examine the feasibility of an offshore, grid-connected test site south of St Catherine’s Point on the Isle of Wight.
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1. Introduction This paper sets out the results of a study to establish the feasibility of an evaluation and research Centre for tidal stream and other marine energy generating devices on the Isle of Wight, which will underpin regional targets for electricity generation from renewable sources and will form the focus for a new marine energy industry in the SE region. The Centre will facilitate investment and innovation in an emerging market sector, helping businesses to seek out new opportunities and new markets. 1.1 Energy Targets Through the Kyoto Protocol, the UK has a legally binding target to reduce emissions of greenhouse gases by 12.5% below 1990 levels in the period 2008 – 2012. The government has also set a domestic goal to cut carbon dioxide emissions by 20% below 1990 levels by 2010. The Energy White Paper published in February 2003 contains a long-term goal for a 60% reduction in the UK’s carbon dioxide emissions by 2050, with real progress made by 2020. In line with these goals, the government has set national targets to meet 10% of UK electricity generation from renewable sources by 2010 and 15% by 2015. There is a further aspiration to increase this figure to 20% by 2020. The corresponding targets for electricity generation from all appropriate renewable sources in the SE Region1 are 620 MW (5.5%) installed capacity by 2010 and 895 MW (8%) by 2016. The energy potential of fast-flowing tidal currents around the British Isles was the subject of a study2 by the energy consultancy Black and Veatch in 2005. The report concluded that the UK’s tidal stream resource is equivalent to 12 TWh and could supply up to 5% of the UK's electricity requirement. More recently, Prof Ian Bryden from Edinburgh University has argued that the figure may be as high as 60TWh. The advantage of this form of renewable energy over other technologies such as wind and solar is that it is entirely predictable – the expected times and strengths of tidal currents are routinely published in nautical almanacs. A further advantage is its high energy density: since water is 830 times denser than air, water flow contains 830 times more energy than wind blowing at the same speed. The DTI’s atlas of UK Marine Energy Resources3 shows the potential for large scale, commercial exploitation of the energy for export to the national grid from several tidal races along the south coast of England, such as the St 1 Harnessing the Elements: Supporting Statement to the Proposed Alterations to Regional Planning Guidance, South East – Energy Efficiency and Renewable Energy. Report by the South East England Regional Assembly, May 2003 ISBN 1-904664-01-6 2 The UK Tidal Stream Resource and Tidal Stream Technology. Report prepared for the Carbon Trust Marine Energy Challenge, Black and Veatch, 2005 3 Atlas of UK Marine Renewable Energy Resources. DTI, Report No R1106 Dec 2004
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Catherine’s race off the Isle of Wight and the Dover Straits off South Foreland. The extractable energy is on the order of tens of MW, with the advantage that the time of maximum tidal flow at subsequent coastal locations is sequential, thus “smoothing” the intermittency of the tidal energy resource. Small-scale tidal stream devices, which will operate in shallow water, are also evolving and these have the potential to service compact waterside residential or industrial development. Further research will illustrate how such devices can contribute to the energy requirements of waterside developments in the SE region. 1.2 The Isle of Wight as a Centre for Marine Energy The tidal regime around the Isle of Wight has some unique features that make it especially suitable for demonstrating the concept of tidal stream energy. One of these is a result of its location along the English Channel, at a position where interference between diurnal and semi-diurnal tides creates a long dwell at high water and a short dwell at low water. This results in two periods of strong tidal stream (on falling and rising tides), with a fairly short temporal separation between them. The geography and bathymetry around the Island produce a number of local eddies and races during these periods, resulting in very strong streams at a number of locations The Island's technical, industrial, and scientific infrastructure is substantial - particularly in areas associated with marine technology. A small number of large, high-technology companies are based on the Island. Generally, these companies trace their origins through many metamorphoses back to famous technology names, such as Plessey Radar, FBM Marine Ltd, Saunders-Roe, GKN-Westland Aerospace and the British Hovercraft Corporation. Each metamorphosis of these companies has spawned the creation of a few very small, very highly-specialised, technically competent businesses. MTMC is one such business, others range from Strainstall (specialists in marine structure and strain monitoring), through Physe (specialists in provision of MetOcean data and analysis to offshore oil contractors), down to one-man businesses with unique specialised engineering skills. Many operate in informal or formal clusters, such as Vectis Energy. The Island is unique in the amount of data, and the level of understanding, of local coastal processes, because it has its own Centre for the Coastal Environment. The existence of such a specialist centre is a direct consequence of the unique complication of the Island's coastal regime and also of its geology and susceptibility to coastal erosion. Much of this information is properly managed and catalogued at the Coastal Visitor Centre in Ventnor. This situation is in marked contrast with many other coastal areas in the region and nationally, where information is fragmented and neither centrally held nor centrally managed.
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There are also many regional centres of associated expertise. Academic centres concerned with the marine environment are based at Southampton, Bournemouth and Portsmouth Universities, and include the National Oceanographic Centre at Southampton. Southampton Solent University has a strong role in maritime operations research and training. A number of government (or quasi-government) laboratories exist outside the universities and specialise in a wide range of marine technologies, most linked to the Royal Navy, but with mission statements that include targets for "technology transfer" to civil applications. The region's industrial base includes businesses ranging from Naval Shipbuilders through Marina Developers to constructors of small leisure and working craft. The marine industry is one of the few buoyant sectors of UK manufacturing and enjoys substantial export success. All of these regional resources will support, and be supported by, the proposed marine energy centre. The Isle of Wight Council has recently reiterated its support for the development of tidal energy close to the Island in the 2006 Renewable Energy Action Plan. The Council recognises the potential for the Island to accelerate the UK marine energy industry by enhancing the Island’s established marine technology infrastructure to fit the needs of this burgeoning international market. 1.3 Solent Ocean Energy Centre This study examines the feasibility of establishing a centre for evaluation and research into marine energy technologies on the Isle of Wight: the Solent Ocean Energy Centre (SOEC). The longer-term aim of the Centre is to facilitate the achievement of local, regional, and national targets for renewable energy generation, through exploitation of the regional tidal energy resource. 1.3.1 National Significance The UK government set four goals in the 2003 Energy White Paper for the country’s energy policy:
• To put ourselves on a path to cut the UK’s CO2 emissions by some 60% by about 2050, with real progress by 2020
• To maintain the reliability of energy supplies • To promote competitive markets in the UK and beyond, helping to raise
the rate of economic growth and to improve productivity • To ensure that every home is adequately and affordably heated.
In the long term, marine renewables can contribute significantly to the first two of these goals, by meeting 15-20% of current UK electricity demand. The Carbon Trust’s Marine Energy Challenge4 estimates that 3 GW of wave and
4 The UK Tidal Stream Resource and Tidal Stream Technology. Report prepared for the Carbon Trust Marine Energy Challenge, Black and Veatch, 2005
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tidal stream capacity could be installed by 2020, representing 2.1% of electricity supply in that year. The UK has established a leading position in the development of marine renewable energy devices (see Sections 3.2.2 and 3.3.2) and it is important to develop an infrastructure to support this embryonic industry, in order that the global competitive advantage is maintained (third goal of the energy policy). The proposed Solent Ocean Energy Centre will form a key component of that infrastructure by providing services for:
1. Evaluation of initial designs using a standard procedure, whereby the most promising may be selected for further development
2. Validation of the performance of prototype energy extraction devices in the marine environment, to attract private investment and assist commercialisation
3. Assessment of environmental impacts of marine energy devices, to inform the national planning and consents procedure
1.3.2 Regional Significance By establishing the Solent Ocean Energy Centre, SEEDA will demonstrate that it competes at the forefront of technology, concentrating on prototyping and development rather than mature manufacturing markets. The proposed Centre sits comfortably within the objectives set out in SEEDA’s Regional Economic Strategy (RES). It will promote the region’s knowledge base in the field of marine renewables, both nationally and internationally (Target 2), assist development of business consortia for the marine renewables sector (Target 3) and provide infrastructure to maintain international economic competitiveness in the marine industry (Target 4). The RES aims (Target 5) to provide integrated business support, particularly for micro-businesses, and the latter form the core of the business model and Technical Support Structure of the Centre set out in Section 6 of this report. Further synergies with the RES arise through the targets and aims related to Sustainable Prosperity, whereby business opportunities arising from energy policy will be promoted and exemplar projects for local energy supply will be conducted. Promoting the integration of tidal stream energy micro-generation within waterside residential and industrial developments, which has been recommended as a core activity for the Centre (see Section 2.1), will support high visibility projects that encourage the public to embrace the concept of local electricity generation from renewable sources. Under pressure to meet energy targets, local and regional regulators may find themselves unable to properly evaluate the claims of competing marine renewable energy device suppliers and installation companies. They may even be persuaded to approve schemes that claim to contribute to achievement of energy targets, but are suspected to be detrimental in other respects.
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The centre will provide local authorities and regulators with knowledgeable and impartial advice to inform their decisions, whilst also providing reputable companies with the means to substantiate their claims and to optimise their designs. 1.3.3 Local Significance The Centre and it’s proposed business model will build on the local strength of small marine-related companies on the Isle of Wight and surrounding region, whereby the current “low-wage” economy has real potential for transformation to a technology and knowledge-based economy. If the test and evaluation facility is established locally, the financial value of testing and consultancy work for regional companies and authorities will be retained within the region. Conversely, the financial value of work for companies from outside the region may be imported. It is also important that devices from developers in the SEEDA region are tested here, in order to prevent drift of regional expertise abroad. Conversely, attracting evaluation work from outside the region effectively imports experience and knowledge at no financial cost. The presence of a national R&D Centre on the Isle of Wight will encourage participation from the higher education sector, bringing benefits to the Island’s social make-up and providing aspirational models for young people.
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2. Vision and Objectives 2.1 Mission of the Solent Ocean Energy Centre A fitting Mission Statement for the Solent Ocean Energy Centre is: “To develop a Centre for evaluation and research of marine energy technologies in the SEEDA region, which will be the location of choice for the testing of scale model and demonstrator generating devices by device developers in Europe and will be the focus of related marine renewable energy initiatives and applications” It is envisaged that the Centre will underpin developments of tidal stream and other marine renewable energy generation initiatives in the SEEDA region by:
• Providing world class test and evaluation facilities alongside a technical and logistical support structure, for model and small scale prototype marine renewable energy generating devices
• Promoting the integration of tidal stream energy micro-generation within waterside residential and industrial developments (such as the Cowes Waterfront and Woolston Riverside projects), through information dissemination, technical advice and practical assistance
• Supporting local industry involvement in tidal stream energy technologies, by provision of the infrastructure for an industry network which will be a resource for technical information and client opportunities
• Encouraging and supporting innovative concepts for the generation of energy from tidal stream and other marine energy resources, through mentoring of inventors and collaboration with local Institutes of Higher Education
2.2 Proposed Milestones In order to progress the concept, MTMC has identified feasible objectives for 2007 and proposes longer term timescales for key events. 2.2.1 Objectives for 2007
• Formalise the business plan for the Centre • Appoint part-time technical and administration manager • Contract agency to prepare PR material and design website. • Formal launch of the Centre • Perform a comprehensive survey of inshore sites identified in this study
as having potential for field testing of tidal stream energy generators and their ancillary equipment / deployment procedures.
• Select site and initiate permit applications • Survey the existing local and regional capabilities with potential for
contributing to the Centre and create a directory or database
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• Engage with EMEC, Wavehub and NaREC, with a view to formal or informal collaboration.
• Develop and agree a protocol for validation of device performance • Aim to contract 3 clients for testing a marine RE device in the existing
towing tank / wave tank facilities. • Form a regional business network for companies with skills and
expertise relating to marine renewable energy.. • Engage with organisations such as Institutes of Higher Education and
Marinetech South regarding new marine energy technologies and concepts.
• Identify suitable waterside sites for tidal stream micro-generation and initiate discussions with stakeholders.
• Engage with development companies, to progress the concept of incorporating tidal stream micro-generation into waterside developments.
2.2.2 Longer Term Timescales and Key Events Year Event 2007 Launch of the Solent Ocean Energy Centre
Permit applications for inshore marine test site 2008 Permit applications for demonstration tidal stream micro-generation
project at a waterside development Permit for inshore marine test site granted First field test at inshore site: aim for120 days utilisation in first year Investigate offshore tidal stream demonstrator test site Site selection and permit application for offshore site
2009 Installation of demonstration tidal stream micro-generation project Further projects tested at inshore site: aim to maintain 120 days p.a. Permit for offshore tidal stream demonstrator site granted
2010 Monitor and refine demonstration micro-generation project Further projects tested at inshore site: aim for increased usage Installation of first offshore tidal generator commences
2011 Further installations of tidal stream micro-generation projects Installation of offshore tidal generator complete Generation commences: aim for 4 total
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3. Marine Energy Extraction 3.1 Introduction The UK possesses some 35% of Europe’s wave energy resource and 50% of its tidal resource. According to data from the Carbon Trust’s Marine Energy Challenge5, 3GW of wave and tidal energy capacity could be installed in the UK by 2020, generating approximately 8 TWh per annum (2.1% of the UK’s electricity demand in that year). In the long term, marine renewable energy could meet 15 – 20% of the UK’s current demand for electricity. The potential for this level of deployment gives wave and tidal energy strategic importance as a contributor to the UK’s aspiration of supplying 20% of electricity from renewable sources by 2020 and intention to reduce carbon emissions by 60% in 2050. 3.2 Tidal Stream Energy Tidal energy originates from the gravitational pull of the moon – and to a lesser extent of the sun – on the waters of the world’s oceans. As the earth rotates, it presents an ever-changing face to the moon, which in turn attracts the oceanic waters, first in one direction and then the other, in an oscillatory motion. The sun increases the amplitude of this oscillation when it is in conjunction with the moon (i.e. on the same side of the earth) or in opposition (i.e. on the opposite side of the earth). The resultant large tides are known as spring tides and occur about every 14 days. The lesser tides, known as neap tides, occur when the sun and moon are out of phase, midway between the occurrence of subsequent spring tides. The associated horizontal movement of water, or tidal streams, are insignificant in the deep ocean when compared with major ocean currents such as the Gulf Stream. They become significant only when they reach the relatively shallow water of the continental shelf and increase still further when the cross-sectional area available for the flow is reduced by surrounding landmasses and geographical obstructions, such as headlands and islands. It is the favourable geography of its coastline that results in the British Isles possessing 50% of Europe’s tidal resource and 10 – 15% of the known global resource. The key advantages of tidal stream energy over other forms of renewable energy are:
• High energy density – since water is 830 times denser than air, flowing water contains 830 times more energy than wind blowing at the same speed. However, the exploitable range of wind speeds is much higher
5 The UK Tidal Stream Resource and Tidal Stream Technology. Report prepared for the Carbon Trust Marine Energy Challenge, Black and Veatch, 2005
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than tidal flows, and power is proportional to the cube of speed, so on average the energy density of tidal stream flows is about 4 times greater than that of wind. This means that the rotors can be smaller (and hence cheaper) than those of a typical wind turbine.
• Predictable energy resource – the amount of energy and the exact time when it will be available is totally predictable, because the times of high and low water and the tidal range are routinely and accurately predicted for the use of seafarers worldwide. This overcomes the problem of intermittency encountered with many sources of renewable energy.
• The times of maximum flowrate (and hence maximum energy resource) are sequential along the coast of the English Channel, which improves the continuity of electricity supply.
• Low visual impact – most, if not all, of the generation equipment is located underwater.
3.2.1 Devices for Tidal Energy Extraction It is possible to exploit the height difference between high and low water by building a tidal barrage such as the structure across the mouth of the River Rance in Dinard, Northern France. Barrages may have significant visual and environmental impacts that are difficult to deconstruct, should their negative impacts be found to outweigh the advantages of renewable energy generation. Tidal stream generators, which are devices for extracting energy from the flow of water in a tidal stream and converting it into electricity, form a viable and attractive alternative to such permanent structures. This Section of the report summarises the current state of tidal stream technologies. The main components of a tidal stream generator are:
1. The prime mover, which extracts energy from the moving water. It may be a rotor of some sort, or an oscillating foil
2. Foundations, which hold the prime mover in the flow and react the hydrodynamic loads to the seabed. Foundations may work on gravity, through a pile or via anchors
3. The powertrain, which consists of a gearbox and electricity generator 4. The power-take-off system, for exporting electrical power to a shore
station. The prime movers would be the components most frequently tested in the laboratory facilities of the proposed Solent Ocean Energy Centre and are worthy of further consideration. They may be conveniently categorised as follows.
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Horizontal Axis Turbine The rotors of horizontal axis turbines are similar to those of conventional wind turbines. The number and shape of the blades differ according to the specific design and as the name suggests, the blades rotate in a vertical plane, about an axis in the horizontal plane.
Figure 3.1 Twin rotor horizontal axis turbine The twin rotor horizontal axis turbine designed by Marine Current Turbines (MCT) shown in Fig 3.1 is mounted on a pile driven into the seabed. The twin rotor concept maximises use of the expensive pile-driving operation and will be employed in MCT’s Seagen project for a 1 MW tidal stream generator currently under construction in Strangford Lough, Northern Ireland. The cross beam supports the rotors in the middle of the water column where tidal flow is maximum. It is mounted on a collar around the pile and can therefore be raised above the surface of the water to facilitate maintenance operations. The alternative of deploying divers or Remotely Operated Vehicles (ROVs) for underwater maintenance in a fast-flowing tidal stream is a hazardous operation. Seagen is a development from the Seaflow project, which is a 300 kW single rotor turbine installed in 2003 off the coast of Lynmouth in the Bristol Channel.
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Seaflow utilises the same maintenance procedure, by raising the rotor above the surface, as shown in Fig 3.2.
Figure 3.2 Seaflow turbine, with rotor raised for maintenance Vertical Axis Turbine A representative vertical axis turbine designed by Blue Energy Canada is shown in Figure 3.3. Four hydrofoil-shaped blades are mounted at the ends of support arms on the rotor, which drives the gearbox and generator assembly. The latter sit above the surface of the water, where they are accessible for maintenance and repair. The foundation is a heavy concrete caisson, which anchors the unit to the seabed. There is a duct surrounding the rotor (not shown in the cross section view) which directs water flow through the rotor The system can be sized to produce between tens of kW for domestic (micro- power) consumption, up to hundreds of kW for waterside communities or industrial sites. For large-scale power production with national grid connection, multiple turbines would be used. To date, Blue Energy claims to have built and tested six prototypes under the auspices of the National Research Council of Canada.
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Figure 3.3 Vertical axis turbine designed by Blue Energy, Canada Cycloidal Turbine The Cycloidal turbine works on a principle similar to the Voigt Schneider propeller. The rotor consists of a baseplate upon which several blades are perpendicularly mounted. The blades articulate as the rotor revolves, presenting an ever-changing aspect to the flow.
Figure 3.4 Rotor of a Cycloidal turbine The concept is illustrated in Figure 3.4, where the top blade presents a flat face (with maximum drag) to the flow, which causes the flow to push the blade and top section of the rotor from left to right. Movement of the opposite blade opposes the flow and it is feathered to produce minimum drag. The orientation of blades in between is constantly changed so that each one works as a hydrofoil, generating a lift force at right angles to the flow – downwards on the right hand section of the baseplate, upwards on the left.
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This innovative concept may be less attractive than more basic designs because it requires energy input during operation, to control the angle of the blades. Helical Turbine A helical turbine for tidal stream generation (shown in Figure 3.5) is under development at Northeastern University in Boston, Massachusetts.
Figure 3.5 Helical turbine rotor The blades run in a helix pattern around a virtual cylindrical surface and rotate around a central shaft. This design is claimed to develop high torque when driven by relatively slow water flows.
Figure 3.6 Helical turbine trials in the Uldolmok Strait
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Several advantages over a more conventional “propeller-type” turbine have been cited. Slow rotational speeds avoid cavitation and the associated problems of vibration and fatigue. The rotor can be oriented vertically or horizontally, it can operate in shallow water and exhibits unidirectional rotation, regardless of the direction of the water flow. This design was first tested in 1996, in the Cape Cod Canal near Boston. The Korean Ocean Research and Development Institute has subsequently conducted trials in the Uldolmok Strait: see Figure 3.6. Oscillating Foil Hydrodynamicists have long been intrigued by the apparent efficiency with which marine mammals use the energy from their tail fins to propel themselves through the water. Oscillating foil tidal generators operate on a similar principle, but with energy transfer in the opposite sense. Instead of transferring energy from the oscillations of the fish’s tail into the water, the energy from flowing water forces a hydrofoil to oscillate up and down and the resultant mechanical energy is transformed into electrical energy by the generator. Figure 3.7 Oscillating foil tidal stream generator Figure 3.7 is an artist’s impression of Stingray, a tidal generator that was developed by the Engineering Business with substantial DTI funding at the beginning of the present decade. It consists of a hydrofoil whose angle of attack relative to the approaching water stream is varied by a simple mechanism. This causes the supporting arm to oscillate, which in turn forces hydraulic cylinders to extend and retract. High-pressure oil is produced and is used to drive a generator. Development of Stingray was put on hold in 2004 for financial reasons. A similar device called the Pulse Generator is now being taken forward by a consortium lead by IT Power, for shallow water applications and field trials are to be conducted in the River Humber.
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3.2.2 Tidal Device Developers The UK has established itself as an early market leader in tidal technologies. Tables 3.1 and 3.2 illustrate that over 30 developers are headquartered in the UK, compared to about 15 in the rest of the world (Table 3.3). In addition, the UK has pioneered the establishment of shared facilities for testing both wave and tidal devices, such as the European Marine Energy Centre (EMEC) in Scotland and Wavehub in SW England. During the course of this study, four local tidal device developers were interviewed face-to-face and a further four from the south of England were interviewed on the telephone (a total of eight interviews). Six of these were at an early (conceptual) stage of advancement and had not tested their devices under rigorous laboratory conditions. All but one expressed great interest in using the test facilities on the Isle of Wight, although it was not clear whether they had access to funds for this activity. Their testing requirements are discussed more fully in Section 4.2. The exception was a developer who stated that he had investigated use of the GKN tank on the Osborne site, but he needed deeper water for his device and was considering alternatives such as the tank owned by the Seafish Authority at Hull. The conversation with more advanced developers provided useful insight into the need for a relatively sheltered and accessible marine site with high tidal flows, for short term device testing in a more aggressive environment than the laboratory, as well as for trials of ancillary equipment, such as foundations and moorings. This site would also be useful for demonstration and refinement of deployment and maintenance procedures. One developer has identified a suitable site in Scotland, but would prefer to use more local facilities in the south of England, if they were available.
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Table 3.1: Tidal Device Developers in the South of England Company Website Location Comments Device Subsea Turbines www.subseaturbines.com Bath The SST is rated at 1 MW. Ducted horizontal axis turbines. Seabed
mounted. MCT www.marineturbines.com Bristol 1 MW pre-commercial demonstrator in
Strangford Lough. Twin horizontal axis turbines, pile-mounted
Tidal Generation Ltd * www.tidalgeneration.co.uk Bristol CEO used to work for MCT. Broke away to form TGL
Deep-gen: bottom-mounted, horizontal axis
Aquascientific www.aquascientific.com Devon Connected with Exeter Uni. Consortium lead by IT Power
Combined lift and drag turbine. Plan to test off the back of a boat in the River Exe
QinetiQ Winfrith www.qinetiq.com Dorset Concept study: CFD and physical modelling
Cycloidal vertical axis design
Susgen www.susgen.com now unavailable
Dorset Collaboration with Southampton University was claimed in 2004
The turbine and generator are positioned in the mid-section of concrete box-shaped base, with flared ends to funnel the water.
Hales Energy * www.hales-turbine.co.uk East Sussex Vertical axis, flat tipping blade(?) Crystal Consultants ** Isle of Wight Director used to work at Kilowatt Whale. Improved version of the Kilowatt Whale
device Kilowatt Whale Ltd ** Isle of Wight Venturi device
WaB Energy Systems Ltd **
Isle of Wight Shallow water vertical axis device
RVG ** Isle of Wight At early stage of development Current to Current UK Ltd
Kent Very strong design and management team. DTI Consortium with Cambridge Uni
Deep-water application. Innovation is gearbox with toroidal drive for high torque at low rpm
Tidal Stream Partners *
www.tidalstream.co.uk London Very strong partnership with Rolls Royce and Oxford University
System for supporting axial turbines in deep- water locations. Testing at Haslar.
Hydroventuri www.hydroventuri.com London A working model (0.6m aperture system) has been tested successfully in Grimsby
Rochester venturi - awaiting tests at EMEC
www.soton.ac.uk Southampton 25 cm diameter prototype has been tested in University ship tank
Shallow water, horizontal axis device. Works with flow in either direction
Cormorant Ltd Surrey DTI Consortium with Plymouth and Bristol Universities
Contra-rotating design. Looking to deploy a 50kW prototype
McMenemie device Sussex Inventor wishes to involve someone better qualified to optimise for testing.
Tidal/sea current energy device
Loadpoint ** Swindon, Wilts. Bath Uni is involved on the electrical side. Device has been tested in the Thames
Based on Savonius rotor. Works with flow in either direction
Key: * Company interviewed face-to-face during this study ** Company interviewed by telephone during this study
Company Website Location Comments Device Lunar Energy www.lunarenergy.co.uk East Yorkshire Rotech owns the technology. It's not
clear how well advanced this is Rotech Tidal Turbine: bottom-mounted, ducted rotor
Neptune Renewable Energy Ltd
Ducted turbines, mounted under a barge
Pulse Generation www.pulsegeneration.co.uk Hull Testing in the Humber, with DTI support. IT Power and BMT renewables in consortium.
A flappy device - I suspect not very efficient
Blue Energy UK Ltd www.bluenergy.com Inverness-shire May be an attempt by Blue Energy Canada to access DTI money. Two partners are start-up companies
Tidal turbine "fence" based on Darieus turbines (vertical axis, according to EMEC)
Open Hydro www.openhydro.com N Ireland Technology developed in US. Operations in Florida and Ireland
Bottom-mounted paddlewheel with permanent magnet in outer rim of rotor, surrounded by a duct
SMD Hydrovision www.smdhydrovision.com Newcastle- upon-Tyne
Testing 1 MW unit at EMEC in 2006 Twin contra-rotating turbines mounted on a crossbeam
Engineering Business
Scotrenewables (Marine Power) Ltd
www.scotrenewables.com Orkney Testing 1/40th scale model at Haslar, inc. mooring system
Combined tidal current and wave. Floating, horizontal axis. Next plan is 1MW demo
RTVL: (Renewable Technology Ventures Ltd
Scotland To be built at EMEC with £2m from DTI and £650k from the Scottish Exec.
Project Neptune: pile-mounted, horizontal axis. RTVL is owned by Scottish and Southern
Overberg Ltd www.overberg.co.uk Tyne and Wear Funded by OneNorthEast. DTI Consortium with NaREC
Deep water, floating, tethered
Company Website Location Comments Device Swanturbines www.swanturbines.co.uk Wales 1m diameter prototype was tested
by towing from University Research Vessel, 'Noctiluca'.
Horizontal axis rotor with gearless low speed generator. Seabed mounted on gravity base with yawing mechanism.
Tidal Hydraulic Generators Ltd
Wales? Successful pilot scheme in Milford Haven. Babtie are involved.
Bottom-mounted, horizontal axis
Table 3.3: Tidal Device Developers outside UK
Company Website Country Comments Device Karnauchow Turbine
Australia Suitable for shallow water. Vertical axis turbine with upper and lower hinged power blades
Tyson Turbine Australia Invented by an Australian farmer. First marketed in November 1992.
A propeller-like water wheel is suspended in a river between two pontoons
Woodshed Technologies Pty
Hydro-Gen www.hydro-gen.fr France Concept only: developed by 2 former navy officers
Horizontal axis floating paddle wheel
Ponte di Archimede International
Kobold Turbine: vertical axis
Swingcat Netherlands The vessel sheers on the anchor cable, due to tidal current-generated lift forces on its keels
Hammerfest Strom
Seapower International AB
www.seapower.se Sweden Has been tested at laboratory scale. A Joint Venture was established on the Shetland Isles in 2000.
Vertical axis, Savonius rotor
www.encorecleanenergy.com USA Riverbank Hydro Turbine: Vertical axis rotor, with opening and closing shutters
Gorlov Turbine USA Field trials in Cape Cod Canal, 1996-9. Testing by Korean Ocean R & D Institute, 2002
Helical turbine, vertical axis (similar to Darrieus)
UEK www.uekus.com USA Has tested in the Chesapeake Bay "Underwater electric kite". Positively buoyant, bottom-moored. Horizontal axis ducted turbine
Table 3.3 (cont): Tidal Device Developers outside UK Company Website Country Comments Device Underwater Electric Kite Corp
www.uekus.com USA A 40-foot wide twin-turbine is intended for deployment in the Gulf Stream off Florida.
Ducted horizontal axis turbines. The design features a self-contained moderately buoyant turbine-generator suspended like a kite within the tidal stream.
Verdant Power www.verdantpower.com USA Tested in Chesapeake Bay. 6-unit pilot in East River (pending)
Small scale, inshore units. Bottom-mounted, horizontal axis
Water Wall Turbine
www.wwturbine.com USA 6 paddle water wheel, horizontal axis on water surface
3.3 Wave Energy The marine wave energy resource is a concentrated form of solar energy. Winds generated by the differential heating of the earth interact with the surface of the oceans, transferring some of their energy to form waves. Power at the initial solar power level of about 100 W/m2 is concentrated to waves with average power levels of 70kW per meter of crest length, winter averages of 170 kW per meter and storm levels of over 1 MW per meter of crest length6. Wave size is determined by wind speed and fetch (the distance over which the wind interacts with the waves) and by the depth and topography of the seafloor (which can focus or disperse the energy of the waves). The offshore wave energy resource is less location-specific than tidal stream energy and therefore more abundant worldwide. However, despite improvements in the reliablitiy of short-term metocean forecasting, waves are less predictable than tides with respect to size and availability of the energy resource. 3.3.1 Devices for Wave Energy Extraction The waters around the Isle of Wight do not possess a significant wave resource and it is not envisaged that wave energy generators will be field tested at the proposed Solent Ocean Energy Centre. However laboratory testing of small scale models in the GKN towing tank with wavemakers is quite possible. Therefore the technology of wave energy devices will be discussed here, but in less detail than the technology of tidal energy devices. A wave energy converter (WEC) captures the energy from waves and converts it into electricity. A WEC must resist the motion of the waves in order to generate power. There are four main types, which are described below and examples of each type are presented. Buoyant moored device A buoyant moored device floats on or just below the surface of the water and is moored to the sea floor. The mooring is static and is arranged in such a way that the motion of the waves will move one part of the machine relative to another part. The motion induced by the waves may be horizontal (surge), vertical (heave) or rotational (pitch), or some combination of the three. Examples of this technology include Pelamis (shown in Figure 3.8), the Archimedes Wave Swing (AWS) and the Manchester Bobber.
6 Technology Status Report: Wave Energy. A report by ETSU as part of the DTI’s New and Renewable Energy Programme, 2000.
Figure 3.8 The Pelamis wave energy device Ocean Power Delivery, the manufacturer of Pelamis, has been contracted by the Portuguese government to deploy three 750 kW machines in a commercial wave farm off the coast of Portugal. Hinged Flap device A hinged flap device is bottom mounted. The movement of the waves causes the buoyant paddle to oscillate, forcing hydraulic fluid through hydraulic pumps to generate electricity. This concept has been exploited to develop AW Energy’s WaveRoller (Figure 3.9).
Figure 3.9 WaveRoller concept A 1/3 scale prototype of WaveRoller was successfully field-tested at EMEC (the European Marine Energy Centre) in Orkney in 2005. Oscillating water column An oscillating water column (OWC) is a partially submerged, hollow structure. It is open to the sea below the water line, enclosing a column of air on top of a column of water. Waves cause the water column to rise and fall, which in turn compresses and decompresses the air column. This trapped air is allowed to
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flow to and from the atmosphere via a Wells turbine, which has the ability to rotate in the same direction regardless of the direction of the airflow. The rotation of the turbine is used to generate electricity. The Limpet unit on the shore of Islay, which was the first commercial wave generator in the UK, has an inclined OWC. The unit’s performance has been optimised for annual average wave intensities of between 15 and 25kW/m. The water column feeds a pair of counter-rotating turbines, each of which drives a 250kW generator, giving a nominal rating of 500kW. Other devices utilising this technology include OREcon, currently being developed as a 1.5 MW prototype: see Figure 3.10.
Figure 3.10 Oscillating water column wave generator OREcon Overtopping device This type of device relies on physical capture of water from waves which is held in a reservoir above sea level, before being returned to the sea through conventional low-head turbines which generate power. The earliest example of this technology was the “Tapchan” system pioneered in Norway. The Wave Dragon pre-commercial demonstrator is another example of an overtopping device with a rated capacity of 7MW, which will be moored off Milford Haven on the Pembrokeshire coast. A 1:4.5 scale prototype of Wave Dragon has been deployed in Denmark since 2003. 3.3.2. Wave Device Developers The UK is a market leader in wave energy technologies, with Scottish-based Ocean Power Delivery contracted to deliver three of its Pelamis machines to Portugal for the world’s first commercial wave farm near Povoa de Varzim. This farm will produce 2.25 MW of electricity, sufficient to power 1,500 homes through the national grid. The pioneering work on wave power by Stephen Salter in the early 80s has led to a more diverse and global spread of the industry than for tidal technologies. No attempt is made in this report to identify all the wave energy
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projects either locally or worldwide. Tables 3.4 and 3.5 give examples of twenty-one established developers headquartered in the UK, which may be compared to about eleven in the rest of the world (Table 3.6). Since it is not envisaged that any additional facilities (apart from those already available on the Isle of Wight) will be procured by the Test Centre for testing wave devices, only two local developers were interviewed. One of these was at an early stage of advancement, having tested a small model of his device in shoreside waves. He expressed interest in using the GKN tank with wave- making facilities, although his funding situation is precarious. The second developer interviewed is more advanced, with a test programme already in place. Testing requirements for wave devices are discussed more fully in Section 4.2.
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Table 3.4: Wave Device Developers in the South of England Company Website Location Comments Device Embley Energy www.sperboy.com/ Bristol Completed Carbon Trust "Marine
Energy Challenge" Floating point-absorber; works through an oscillating water column
Offshore Wave Energy Ltd**
www.owel.co.uk Cornwall Has received DTI Smart award and Carbon Trust support. Have tank tested at NaREC, plan sea trials at EMEC
Grampus: Oscillating water column device
Trident Energy Essex 1/5 and full scale prototypes have been tested. Testing at NaREC in October 2005 was successful
The up and down motion of the buoy drives a linear generator.
Wavestore** Hants Concept developed by 2 marine engineers - has been on hold since 2003
Wavestore device - has been tested for concept in shallow water
AquaEnergy Group Ltd
www.aquaenergygroup.com London It does not appear that a device or model has been built yet
AquaBuOY combines elements of proven technology: the IPS Buoy and the Swedish Hose-pump
ORECON Ltd www.orecon.com Plymouth Want 12 month sea trials OWEC with novel energy converter C-Wave www.cwavepower.com Southampton Has received Carbon Trust funding
and funding from Business Angels C-Wave - a buoyant moored device where floating walls are forced to move relative to one another through the action of waves
Ocean Power Technologies Ltd (OPT)
www.oceanpowertechnologies.com/ Warwick Full scale (40kW) device deployed off New Jersey. Other contracts around the world.
PowerBuoy: Central spar, fixed in relation to seabed. Buoy moves up and down around the spar with wave motion and pumps hydraulic fluid through a turbine
Key: ** Company interviewed by telephone during this study
Company Website Address 3 Comments Device Ocean Power Delivery Ltd (OPD)
www.oceanpd.com/ Edinburgh Have tested at EMEC. First commercial plant commissioned off Portugal
Pelamis: floating "hinged sausage" device
Caley Ocean Systems Ltd
www.caley.co.uk Glasgow Want to get the modelling capability of TUV NEL
Mid-water vertical axis turbine
Wavegen www.wavegen.com Inverness Wavegen owns it's own wave tank Limpet (a shore device) has been operating on Islay for several years. OWC with Wells turbine PTO
Lancaster University www.engineering.lancs.ac.uk Lancaster Selected by Carbon Trust for Marine Energy Challenge. Have done tank tests in Lancaster wave tank. Looking to develop a 1/5 scale sea-going prototype.
PS Frog Mk 5: floating point-absorber; waves act on a buoyant paddle attached to an integral ballasted handle which provides the reaction
Ocean WaveMaster Ltd: Manchester Uni/ Alex Southcombe
www.oceanwavemaster.com Manchester 3m model tested at Manchester and Newcastle Unis. 20m model was constructed by Bendalls and tested at NaREC. No news since.
Submerged platform with 2 linked chambers, one at high pressure beneath the wave crest, the other at low pressure beneath the trough
UMIST www.manchesterbobber.com Manchester Reported to be in the early prototype phase in November 2005. 1/10 scale trials were due to begin at NaREC
Bobber consists of a partially submerged float attached to a pulley via a cable, which turns a shaft as the float bobs up and down
Innova Ltd None Northumberland Developing concept with Robert Gordon Uni, which has a wave tank. Note email address!
Dive bobber is at initial numerical modelling and first experimental modelling stage
AWS Ocean Technology
Archimedes Wave Swing: Telescopic cylinder attached to the seabed
Ocean Power Technologies Ltd
www.oceanpowertechnologies.com/ Warwick Full scale (40kW) device deployed off New Jersey. Other contracts around the world.
PowerBuoy: Central spar, fixed to seabed. Buoy moves up and down around the spar pumping hydraulic fluid through a turbine
Table 3.6: Wave Device Developers outside UK
Company Website Country Comments Device Energetech www.energetech.com.au Australia During July 2006 the device operated
successfully in the open ocean at Port Kembla. 80% efficiency is claimed
Parabolic wall focuses the waves and an OWC drives an air turbine
Wave Dragon www.wavedragon.net Denmark Large commercial plant to be installed off Pembrokeshire
Over-topping device, the head of water drives a small turbine
Wave Star Energy www.wavestarenergy.com Denmark 1:10 Scale model in operation in Nissum Bredning
20 floats at the base of a hydraulic cylinder are lifted sequentially by the waves. The floats force oil into the machine’s common transmission system that drives a hydraulic motor.
WavePlane Production A/S
www.waveplane.com Denmark WavePlane has been deployed at sea for 3 years
The device has submerged damping plates that reduce its motion relative to the surrounding water. Water from waves is led through ducts into a flywheel
AW Energy www.aw-energy.com Finland Has been tested at EMEC Waveroller: hinged-flap device Clear Power www.clearpower.ie Ireland Wave Bob Ecofys www.ecofys.com Netherlands Has been tested a Strathclyde Uni,
Danish Hydraulic Institute and NaREC. Sea trials at Nissum Bredning in Denmark
Wave Rotor: Utilises both wave and tidal current water motions. Has vertical axis (Darrieus) and horizontal axis (Wells) blades.
Wave energy AS www.waveenergy.no Norway Project in cooperation with the Norwegian University of Science and Technology and supported by the Norwegian Research Council.
Seawave Slot Cone Generator (SSG): water is captured in several reservoirs placed one above ten other. The captured water runs through a multi-stage turbine
SeaVolt www.seavolt.com USA One third scale model tests have been performed in a tank. May be based on Wave Rider wave measurement buoy.
Wave Rider: Point absorber buoy system designed for water depths greater than 50m
1. New, unusual, flow direction insensitive, or mechanically simple turbines.
2. Unusual support structures, some requiring active control systems, such as depth regulating submerged rafts.
3. Electrical machines with large numbers of pole pairs, particularly suited to 50Hz generation at low rotational speeds.
4. Innovative ways of combining multiple machines into arrays. This group of potential clients are at an early stage of development and are either self-funding or are virtually unfunded. The immediate requirement is therefore to evaluate concepts to a sufficient extent that they can either be
eliminated from further development, or they can become the subject of formal funding bids (to either governmental or commercial sources of finance) with adequate supporting data and documentation. The information that is likely to be required at this early stage includes:
1. An authoritative estimate of device efficiency, including an assessment of the way in which efficiency varies with input conditions and device design parameters.
2. Identification of key engineering features, such as moving parts carrying exceptionally high loads, or parts that must move under the influence of very low flows over the lifetime of the device, in the presence of fouling, etc.
3. Characterisation of the affects of the device on the surrounding flow regime, to inform assessments of environmental impact and for engineering purposes, such as to inform estimates of the performance of arrays of machines.
4. Initial assessments of the stability of supporting structures, the controllability of non-gravity supporting structures, anchor system loads, etc.
The mid term requirement will arise when potential clients have obtained funding for development of their concepts. It is likely to include the same requirements as those listed above, but to higher levels of detail and accuracy; plus the acquisition of engineering data to inform detailed engineering design of prototype systems. The short term facilities and equipment may need enhancement for this work. At this stage it will be necessary to collect detailed data in order to optimise designs and arrays to particular applications. Marine sites and facilities in which installation and maintenance procedures can be tested in relative safety and under observation would also be desirable. The long term requirement is for the field evaluation of prototype versions of total systems. In the case of marine systems, this will include a field test facility in an area of strong tidal resource, close to a potential connection into the electrical distribution network, where the uncertain environmental impact of prototype devices is acceptable and can be monitored, where existing uses (such as shipping channels) are not compromised, where all necessary consents can be obtained, and where access is such that all aspects of performance can be monitored and any necessary maintenance or repair work is possible. A secondary requirement for this group of potential clients will be the provision of data on their target sites for eventual deployment of their devices as functioning contributors to the UK electricity supply network. This will be necessary, if only so that the conditions of the test deployment can be related to the conditions that the devices will face in long term service. The required data will include environmental information, data on the magnitude, range, and extent of the tidal resource, and information on the proximity and capacity
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of local connections to the electricity supply network. Contractors with the expertise to provide this information have been identified within the SEEDA region and will be invited to join the Centre’s commercial structure. 4.3 Facility Options and Availability The range of facilities to which the centre will require access follows naturally from the range of methodology statements that must be executed. Even before the methodologies are fully established, it is clear that the principal requirement is for facilities in which devices (or scale models of devices) can be subjected to controlled flows (in the case of tidal stream devices and micro- hydro generators), controlled variations of depth (in the case if devices utilising potential energy, such as tidal barrage devices and large scale hydro power installations) and controlled waves (in the case of wave energy devices). The current existence and availability of such facilities within the SEEDA region is discussed below, within the context of their incorporation within the Solent Ocean Energy Centre. For the early-stage work of the Centre (i.e. for the first group of clients), the requirement is likely to be for numerical or scale-model facilities. Many device developers consulted during the course of the present study highlighted the cost and accessibility of test facilities that already exist in the region as barriers to progressing their inventions. The role of the Centre will therefore be to provide the required access to testing and to take devices through a standard, cost-effective programme of testing and evaluation. The existing facilities on the Isle of Wight will meet most of the requirements of the first and second group of clients, although modest investment in updating and minor enhancements may be desirable. For the second group of clients they should be supplemented by an enclosed full-scale facility (a “deep tank”) in which diving operations, device deployment and maintenance procedures can be developed and practiced in safety. At least two suitable deep tanks have been identified in the region, although again some modest investment may be necessary to bring one of them into productive use. The third group of clients require at-sea facilities in which procedures developed in the deep tank can be refined and tested in a realistic marine environments and short-term testing of moorings, foundations and devices may be conducted. Extended tests on full-scale devices or arrays of devices over a naturally-occurring range of environmental conditions is also desirable. In our view, this requires two facilities. The first is a relatively unexposed site for procedure development and short-term tests. The second is a site for long- term deployment and monitoring of devices under representative “tide farm” conditions. No suitable facilities have been found to exist in the region, although they exist elsewhere in the UK, as discussed in Sections 4.3.4 and 4.3.5
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4.3.1 Towing Tank A type of facility that can be used for testing in flow and for testing in waves is called a towing tank. This is very long tank of water with a fairly large cross- section and a depth that is typically about half its width. At one end is a wave making machine that can produce long-crested regular or random waves. Spanning the width of the tank is a carriage that runs on rails along the length of the tank. Test objects mounted under the carriage are therefore towed through the water at the speed of the carriage and the water can be either calm or have waves propagating through it. Objects can be tested at any depth and at any speed from zero up to the maximum carriage speed. There are some limitations to the use of such a facility. The most important, particularly for tidal stream devices, is that when objects are tested by towing them through the water the duration of tests is limited by the speed and the finite length of the towing tank. Steady-state tests of an extended duration are not possible. Another limitation, affecting only wave power devices, is that although both regular and random waves are possible, wave energy is concentrated in a single direction of propagation and lacks the directional spread typical of a real sea. In spite of these, and a number of other important issues, a towing tank remains an ideal facility for a wide range of test methodologies. There are three towing tanks in the SEEDA region.
1. A large facility (270 m long, 12 m wide and 5.5 m deep, 12.25 m/s maximum speed)) at QinetiQ in Gosport, which is expensive (~£2,200 per day) and relatively inaccessible, because MoD usage takes priority over commercial work.
2. A smaller facility (60 m long, 3.7 m wide, 1.8 m deep, maximum speed 4.0 m/s) at Southampton Solent University, where student usage takes priority and the short length of run severely limits test duration.
3. A high-speed facility (200m long, 5 m wide, 1.7 m deep, maximum speed 15 m/s) at GKN Aerospace, Osborne site in East Cowes on the Isle of Wight, which would be available at competitive daily rates (~£1,000 per day) for use by the Centre.
4.3.2 Circulating Water Channel A circulating water channel (CWC) is rather like a wind tunnel (with which most people are familiar) filled with water. It can be used for tests similar to those described above for the towing tank. The CWC has four advantages and one disadvantage when compared with a towing tank for the type of work envisaged by the centre. The advantages are:
1. Devices and models are mounted in a fixed location and the water moves past them, as they would be in a real application. In a towing tank, devices must be towed through still water. Viewing, observation,
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video recording, and measuring (particularly measuring using optical methods such as laser-Doppler velocimetry) are much easier when all the equipment is stationary and the water moves, than when the water is stationary and all the equipment has to move.
2. The duration of tests is unlimited. In a towing tank, the length of tank and the speed of the carriage limit test durations. This has implications for the cost and duration of a test programme. As an example, consider the task of plotting the velocity field of efflux from a device. In a CWC, a single velocity sensor can be used to “scan” the efflux. In a towing tank, either an array of sensors must be used, or many runs must be taken in the tank
3. The flow is naturally turbulent in a CWC, like the flow through a device in a real installation
4. Operating a CWC and conducting a test in it are usually one-person tasks. Two or three people are needed to perform the same tasks in a towing tank
The disadvantage is that the cross-section of the flow is usually smaller, and often that the maximum flow speed is less. There are only two CWCs of significant size in the UK. One is in the region, at QinetiQ in Gosport, but it is currently mothballed. The other is at Liverpool University. The two facilities are virtually identical, having a flow cross-section of 1.4m width and 0.4m maximum depth. The maximum flow speed is about 6m/s (12knots), but speeds above 3.5m/s (7knots) present some practical difficulties. These speeds are more than adequate for the testing of tidal energy devices. 4.3.3 Deep Tank The third facility is required by potential clients in what we have called group 2. One of the requirements of these clients is a facility in which installation and maintenance procedures can be developed and verified, best described as a deep tank. It consists essentially of a deep, but not very extensive, tank of water that can be kept clean and reasonably warm, in which divers can work with moderately large items of equipment in much greater safety than is possible in real marine trials. The tank needs a supporting infrastructure heavily biased towards ensuring the safety of users, and operations will be very much easier if the tank is housed within a building. There are a number of candidate facilities in the SEEDA region, of which two stand out as being particularly appropriate. The first of these is owned and operated by QinetiQ in Gosport. It is 5.5m deep, and is equipped with (rather obsolete) wave making machines. Its enormous size (120m by 60m in plan) is, if anything, a disadvantage as it makes access difficult and has some safety implications. Although intended for model-testing of submarines, it has been used for diver training and ROV testing – mostly for defence rather than commercial applications.
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The second tank is in private ownership at Bembridge on the Isle of Wight. Known as the “Thorneycroft Tank”, it was constructed for testing model ships some time before the QinetiQ facility was built. It is also 5.5m deep, with a plan area about 20m by 10m (not rectangular, curvilinear). This smaller size is an advantage for the applications envisaged for the Solent Ocean Energy Centre. 4.3.4 Sheltered Marine Test Site MTMC’s contacts with potential clients have identified the need for two different field test facilities for the Centre and have incidentally identified sites at which permanent tidal power installations might be viable. The first facility will be an extension of the deep tank (described above) into a real, but relatively benign, marine environment. In this environment, installation, retrieval, and maintenance procedures will be developed, using divers, ROV’s, crane barges etc, under conditions that may be typical of those at permanent installations. These conditions are certain to include strong tidal streams, are likely to include a range of turbidity levels, will involve cold water and will present all the “real site” frustrations, such as occasional storms. There may be a requirement for different types of sea bed, from muddy through to rocky, for some applications – e.g. for testing the installation, performance, and maintenance of mooring systems, gravity bases, ground anchors and other similar equipment. For safety reasons, the site must be reasonably enclosed and very accessible, particularly to emergency services. Procedures and equipment developed in the deep tank will subsequently be subjected to these aspects of a real environment in this first type of marine facility. Another use for this site will be short-term trials for prototype tidal energy devices. It is envisaged that small devices would be temporarily mounted on an existing structure (e.g. a pier), or on purpose-built platforms (e.g. a moored raft) for their proof of concept in a real marine environment. A small number of suitable facilities exist already in the UK, the most notable being the diver training centres in Loch Linnhe in Scotland and in Plymouth Sound, but no suitable facility has been identified in the SEEDA region. The region does, however, have potentially suitable sites in the waters adjacent to the Isle of Wight that are fully described in Section 6 of this report. 4.3.5 Offshore Marine Test Site The second facility will be a suitable site for long-term deployment and monitoring of prototype devices under realistic in-service conditions. It follows that this facility should probably be sited in an area in which an operational “tidal energy farm” may eventually be located. In the SEEDA region, the candidate areas are the Straits of Dover, North Foreland, St Catherine’s and the Western Solent. Of these, St Catherine’s has a good tidal resource, is
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clear of major shipping routes and is also close to the other facilities of the centre. We have established that the Isle of Wight’s electricity network could absorb up to 7MW of power from external sources, of which about 5MW could be absorbed in the Ventnor area (Ventnor is the nearest significant town to St Catherine’s). This area is very clearly the front-running site for an operational tide farm in the region. A test site for marine trials of tidal devices exists at the European Marine Energy Centre (EMEC) in the Orkney Islands. A site off St Catherine’s would have significant advantages over EMEC including:
• A strong electricity network and substantial demand for electricity • Less aggressive wave environment, permitting longer windows for
deployment and maintenance • Good national and international travel access • Milder climate and longer daylight hours in Winter
However, we envisage some synergy between the two sites, in that developers may wish to test prototypes at St Catherine’s in order to gain confidence in their survivability for future deployment in the harsh environment at EMEC. 4.4 Conclusions and Recommendations for Test Facilities
1. Steps should be taken to secure the future of the towing tank at GKN Engineering Services on the Isle of Wight. The only other viable facility, at QinetiQ Haslar, is safeguarded by its status as a strategic facility for the Ministry of Defence, but this status also limits its attraction and availability for non-defence work. The GKN tank will be safeguarded if the Centre’s towing tank operations are concentrated there.
2. Steps should be taken to prevent the destruction of the circulating
water channel (CWC) at QinetiQ Haslar, which is currently mothballed because of low demand. This facility is potentially very useful for early- stage development and testing of new tidal turbine designs, offering both convenience and economy in the conduct of qualitative and early quantitative experiments. Reinstatement of the CWC will be less expensive than purchase and construction of an equivalent new facility.
3. If the circulating water tunnel is reinstated, consideration should be
given to co-locating it with the GKN towing tank.
4. An agreement should be negotiated with the owner of the Thorneycroft Tank at Bembridge, guaranteeing its availability in the event of its suitability for any of the Centre’s projects. Reinstatement as a working facility should form part of the costing calculations for the Centre.
5. Recommendations for the marine test site are presented in Section 6.
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5. Instrumentation Requirements Most of the facilities described in Section 4 have much of the necessary associated equipment already installed or available. In this section, we consider other testing equipment that may be necessary, and its likely cost. Most of this equipment is portable (i.e. it could be moved between facilities if required). 5.1 Dynamometer By far the most important item of new equipment, needed for tests in either the towing tank or the CWC, is a dynamometer. A dynamometer can best be described as a calibrated brake with integral measuring equipment. Its use for the Solent Ocean Energy Centre will be as a controllable load on rotating machines, such as models of tidal stream turbines. The brake is connected to the turbine output shaft and applied progressively while the shaft speed and torque are measured. The product of speed and torque is the power being delivered by the turbine to the dynamometer. It is impossible at this stage to specify this dynamometer, because the range of turbine types for assessment is not known in sufficient detail. It is probable that two dynamometers (high speed, low torque and low speed, high torque) will be required. The best estimate of cost is of the order of tens of thousands of pounds. 5.2 General Instrumentation Velocimeters are devices for measuring the speed at which water flows. For this application, it will be necessary to measure flow profiles through cross- sections of the flow in both the inflow and the efflux of the devices. This implies that either a single sensor will be used to “scan” the flow, or multiple sensors will be used (either a small number scanned as an array or a large number covering the entire cross-section), or it will be necessary to use a device that can measure profiles directly. All these things are possible, ranging from simple miniature impeller meters, through arrays of pitot tubes, to laser-Doppler velocimeters, to particle image velocimetry. It is not appropriate here to describe and discuss all of these methods and equipment in detail. However, it is probable that the most cost- effective method will be to use an array of fairly widely spaced pitot tubes, and to enhance spatial resolution by “stepping” the array through a number of displaced positions in the cross-section of the flow. The cost of such a system will be similar to the cost of the dynamometer(s), and both are essential to the centre. A range of pressure transducers, wave probes, thermometers, video cameras and other instruments will also be needed. Individually, these items cost from a few pounds for a calibrated thermometer to a few hundred pounds for a wave probe.
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Data from experiments will need to be acquired and analysed, and video will need to be digitised, edited, rendered, and transferred to DVD (or some other appropriate medium). For this the Centre will need some fairly powerful computers (already available within the manpower resources that the Centre will call on), with a range of data acquisition cards, equipment, and software (that may need to be purchased specially). 5.3 Work Boats and Crane Barge If the Centre develops its own marine field site(s), frequent access to a small workboat, especially one equipped for diving and ROV (remotely operated vehicle) operations, will be required. The boat will be used during deployment, maintenance and monitoring work on test installations. A small crane barge will carry out deployment and recovery of devices under test and of other equipment such as power cables connecting devices to the shore. A second boat of similar size may be used to collect detailed survey and environmental data in both the marine test site and in target sites for permanent installations. This vessel will need to carry survey equipment such as accurate echo sounders, differential GPS (global positioning system) receivers, transponders and underwater video equipment. Specialist environmental monitoring equipment such as turbidity meters and chemical probes will also be required. It is envisaged that contractors to the Centre, such as the National Oceanography Centre in Southampton, would provide suitably equipped boats for these tasks. 5.4 Electrical Load / Electricity Network Connection The marine test sites will need an electrical load in order that devices are tested under realistic output, as well as input, conditions. The smaller of the two sites can probably be served by a simple resistive load, such as a water-cooled heating element. Electrical output from devices under test here may be only a few tens of kilowatts and tests will be intermittent rather than continuous. The load could be submerged close to the device under test, eliminating the need for shoreside buildings and facilities altogether, although this implies the use of either diver-retrieved submerged instrumentation and data acquisition, or a communications buoy with telemetry link to shore. Communications buoys can introduce difficulties – they are often “salvaged” by local fishermen and others (even when they are not adrift). A complete design appraisal for the small marine site is outside the scope of the present study, but it is clear that there are enough design options for the site to be feasible at a moderate, cost.
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The larger site will benefit from a connection to the local electricity distribution network. This is likely to consist of a power cable from device to shore, an inverter / interface to the shore power system, and a connection from the location of the interface to the nearest suitable network connection point. The device to shore cable can also bring signals from device instrumentation ashore, so the interface housing can be combined with a housing for data acquisition equipment. The housing will need to be secure, as will the transition of the cable through the surf zone and over the beach. In this context, it has been determined that the 11kV distribution network on the Isle of Wight can absorb an additional 7MW, of which 5MW could be absorbed by a connection made in the Ventnor area. This is more than sufficient capacity for a large test site offshore at St Catherine’s and indicates the size of permanent offshore tide farm that could be placed there without major changes to the local network. (Incidentally, the local 11kV network’s capacity to absorb 7MW, if continuous, represents about 11% of the Isle of Wight’s projected electricity demand in 2010. The local network appears to be just capable of absorbing the target level for renewable contribution without recourse to the higher voltage networks). 5.5 Conclusions and Recommendations for Instrumentation The test centre needs a small capital inventory of instrumentation and test equipment, some of which is already available. The main items for this inventory are:
• A dynamometer / balance specifically designed for testing various types of hydrodynamic turbine
• A system for flow velocity measurements
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6. Marine Tidal Test Sites 6.1 Introduction In this section of the report, we examine the potential for establishing test sites for tidal energy devices in the waters adjacent to the Isle of Wight. Section 4 identified the need for two sites – one at an inshore, sheltered location and a second site offshore, in deep waters. Since the two sites have different requirements they will be considered separately. 6.2 Requirements for Inshore, Sheltered Site Interviews with potential clients for the Centre established a need for a marine test site where strong tidal currents occur, but which is easily accessible by a small boat or rib, is located in shallow water and is relatively sheltered from waves. The combination of the requirements for strong tidal streams, shelter from the worst weather, accessibility, and a reasonable degree of enclosure limit the range of suitable sites. In particular, sites along exposed coastline are far less suitable than sites that are enclosed - for example within bays, harbours, estuaries, and around the Solent. Harbour and estuary sites are generally disadvantaged by concentration of vessel traffic through restricted areas and complicated local variations of flow. Unfortunately most bays provide shelter from tidal streams as well as from extreme weather conditions and bad weather running into bays can set up rip currents that contaminate the otherwise predictable tidal flows. These considerations eliminate almost all areas other than the Solent and its adjacent waters, which is where the search for suitable sites was focused. The primary requirements for this site are:
• Relatively strong peak tidal flow - a minimum cut-off value of 1.25 m/s (2.5 knots) was chosen
• Depth between 10 and 30 m (the minimum depth being governed by a requirement for useful demonstration of installation and operational methods, the maximum by decompression times for divers on normal air-breathing apparatus)
• Avoidance of commercial shipping Secondary site requirements were identified as:
1. Shelter from wind and waves 2. Proximity to harbour facilities 3. Proximity to area for shore base, accessible by road 4. Existing structure (e.g. pier) to carry power cable through surf zone 5. Avoidance of marine leisure activities (the Solent being a playground
for wealthy and influential boat owners and a centre for high profile yachting events such as Skandia Cowes Week)
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6. Avoidance of activities by other marine stakeholders, such as the fishing and dredging industries
7. Avoidance of Special Areas of Conservation (SACs) and other environmentally constrained areas
Although this is not listed as a requirement, an existing structure protruding into the maximum tidal flow (such as a long pier) to which test devices could be attached would be highly desirable. It should be noted that final site selection and approval would be subject to consenting arrangements as explained in the DTI guidance handbook7. The secondary requirements set out above are in part a first stage to achieving compliance with the DTI arrangements, but the establishment of full compliance is beyond the scope of the present study. 6.3 Inshore Site Selection and Ranking Methodology Candidate sites with strong tidal flows were initially selected by reference to the Admiralty Small Craft Folio of charts for the Solent and Approaches (SC 5600). Spring and neap rates and directions of tidal streams at specific locations around the Isle of Wight (marked by ‘tidal diamonds’) are conveniently tabulated on each chart, in hourly intervals referred to high water at Portsmouth. This source of information permitted an overview of tidal velocities in the area of interest, from which sites with peak rates less than 1.25 m/s were eliminated. The remaining candidate sites were scrutinised for conformity with the other primary requirements of depth and avoidance of commercial shipping. A further check of tidal rates was then conducted, using detailed information in the relevant Admiralty Tidal Stream Atlas8 and the tidal charts published by the renowned Solent yachtsman and navigator, Cmdr Peter Bruce RN9. The candidate inshore sites that remained after the initial screening described above were scored on a scale of 1 to 5 against the secondary criteria listed in Section 6.2. The resultant matrix was used to rank the sites in order of merit. Although this methodology is purely subjective, a more detailed assessment is outside the scope of the present study. 6.4 Candidate Inshore Sites The initial sift of tidal diamond data revealed eleven sites in the waters adjacent to the Isle of Wight (mostly in the western or central Solent) that 7 Planning and consents for marine renewables: Guidance on consenting arrangements in England and Wales for a pre-commercial demonstration phase for wave and tidal stream energy devices (marine renewables). DTI, November 2005 8 Admiralty Tidal Stream Atlas: the Solent and Adjacent Waters. NP 337, Hydrographic Office 9 Solent Tides, Peter Bruce. ISBN 1-871680-05-0
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match the criteria of peak tidal rates greater than 1.25 m/s. Of these, seven were discarded because of their proximity to commercial shipping cha