Renewable Energy from the Oceans: From wave, tidal and gradient systems to offshore wind and solar

Cover
Contents
Preface
1 A review of progress on ocean energies
1.1 A risky business
1.2 In the beginning
1.3 Shocks to the system
1.4 The challenge of ocean energy
1.5 Technology Readiness Levels
1.6 Wave energy – TRL 7
1.7 Tidal and current energy
1.7.1 Tidal range – TRL 9
1.7.2 Tidal stream – TRL 8
1.8 Thermal and salinity gradient systems
1.8.1 Ocean thermal energy conversion – TRL 8
1.8.2 Salinity gradient – TRL 4
1.9 Offshore wind – TRL 8
1.10 Marine solar
1.11 Enabling technologies and actions
References
2 Wave energy
2.1 The wave resource
2.1.1 Wave resource assessment
2.1.1.1 Methods
2.1.1.2 Mediterranean wave assessment
2.1.1.3 Wave assessment at Pantelleria
2.1.1.4 Conclusions
2.1.2 Wave measurements
2.1.2.1 Wave characterization for energy applications
2.1.2.2 Instrumentation for wave measurement
2.1.2.3 Staff gauges
2.1.2.4 Laser range finder
2.1.2.5 Pressure sensors
2.1.2.6 Wave measurement buoys
2.1.2.7 Acoustic Doppler current profilers
2.1.2.8 X-band radar
2.1.2.9 HF-radar
2.1.2.10 Satellites
2.2 Wave energy devices
2.2.1 The ISWEC plant at Pantelleria
2.2.1.1 Introduction
2.2.1.2 The ISWEC
2.2.1.3 ISWEC evolution: from model to full-scale device
2.2.1.4 The ISWEC prototype plant at Pantelleria
2.2.1.5 Conclusions
2.2.2 Harbour breakwaters for wave energy conversion
2.2.2.1 Breakwater-integrated WECs
2.2.2.2 Site-specific design challenges
2.2.2.3 Breakwater-integrated oscillating water column
2.2.2.4 Breakwater-integrated overtopping device
2.2.2.5 Full-scale devices
2.2.2.6 Conclusions
2.2.3 Overview of the development of a pivoting buoy system
2.2.3.1 System configuration and operation
2.2.3.2 System modelling
2.2.3.3 Small-scale model test of the pivoting system
2.2.3.4 Optimization based on potential flow simulation
2.2.3.5 Large-scale prototype
2.3 PTO development
2.3.1 Introduction
2.3.2 Design and test methods
2.3.3 Innovative PTOs
2.3.4 Magnetic gears
2.3.5 Dielectric elastomer PTO
2.3.6 Electromechanical ballscrew-based PTO
2.3.7 Conclusions
2.4 Modelling and control8
2.4.1 WEC models
2.4.1.1 CFD-based models
2.4.1.2 Boundary element models
2.4.2 WEC control
2.4.2.1 WEC control basics
2.4.2.2 WEC control structures
References
3 Tidal and current energy
3.1 Introduction
3.1.1 Characteristics of tidal current energy
3.1.1.1 Predictability
3.1.1.2 Daily and two-weekly variation in tidal current energy
3.1.1.3 Energy production estimation
3.1.2 Basic physics of tidal energy
3.2 The resource
3.3 Tidal rise and fall concepts
3.3.1 Tidal barrages
3.3.2 Tidal lagoons
3.3.3 Dynamic tidal power barriers
3.3.4 Turbines for tidal rise and fall schemes
3.4 Tidal bridges and fences
3.5 Tidal, ocean current and river HKTs
3.6 Differences between hydrokinetic and wind energy
3.6.1 Limited depth suitable for turbines
3.6.2 Tidal and ocean current flow velocities are lower than wind
3.6.3 Much higher fluid density
3.6.4 Cavitation
3.6.5 Predictability
3.6.6 Bidirectional flow
3.6.7 Limited flow field
3.6.8 Floating debris
3.7 Axial flow turbines
3.8 Crossflow turbines
3.9 Ducts and diffusers
3.10 'Flying' turbines
3.11 Oscillating foils
3.12 Vortex shedding
3.13 Tidal sails
3.14 Arrays
3.14.1 Tidal farm layout
3.14.2 Mixing and wake recovery – streamwise and lateral spacing
3.15 Economics
3.16 Actual progress to date on large-scale grid-connected hydrokinetic power
3.17 Case study – development of GEM, a tidal stream energy system
3.17.1 GEM system configuration
3.17.2 Turbine and diffuser experimental tests (small-scale models)
3.17.2.1 General definitions
3.17.2.2 Model set-up
3.17.2.3 Tests on single turbine
3.17.3 Tests on full model in small scale
3.17.3.1 GEM tethered model set-up
3.17.3.2 Characterization of the submerged tethered system
3.17.3.3 Tether force and trim
3.17.4 Full-scale prototype tests
3.17.4.1 Test plant configuration
References
4 Thermal and salinity gradient systems
4.1 Energy resources
4.1.1 Oceanic thermal gradients
4.1.1.1 Optimal characteristics
4.1.1.2 Estimation of energy potential
4.1.2 Salinity gradients
4.1.2.1 Optimal characteristics
4.1.2.2 Energy potential
4.2 Ocean thermal energy conversion (OTEC) plants
4.2.1 Open-cycle plants
4.2.2 Closed-cycle plants
4.2.3 Hybrid-cycle plants
4.2.4 Feed-pump removal technique
4.2.5 OTEC and solar pond
4.2.6 OTEC systems characteristics
4.2.7 Environmental impact
4.2.8 Economic aspects
4.3 Salinity gradient energy (SGE) plants
4.3.1 Pressure-retarded osmosis membrane (PRO) plants
4.3.2 Reverse electrodialysis (RED) plants
4.3.3 Electric Double-Layer Capacitors plants
4.3.4 Faradaic pseudo-capacitor plants
4.3.5 SGE systems characteristics
4.3.6 Environmental impact
4.3.7 Economic aspects
Acknowledgments
List of acronyms
References
5 Offshore wind energy
5.1 Offshore wind characterisation
5.1.1 The random nature of wind
5.1.2 Long-term offshore wind speed characteristics
5.1.3 Turbulence
5.1.4 Wake flow effects
5.1.5 Other offshore-specific conditions
5.2 Wind turbine technology development: a historical perspective
5.3 Basic principles of wind turbine operation
5.3.1 Energy conversion and concentration
5.3.2 One-dimensional momentum and Betz
5.3.3 1D momentum with rotational wake
5.3.4 Basic aerofoil principles
5.3.5 BEM theory
5.3.6 Basic corrections to BEM
5.3.6.1 Tip loss correction
5.3.6.2 High-induction factor correction
5.3.6.3 Corrections for skewed wake effects under yawed rotor conditions
5.3.6.4 Corrections for dynamic inflow and dynamic stall
5.3.6.5 Corrections for 3D stall delay
5.3.6.6 Summary of BEM correction terms
5.4 Offshore wind turbine control systems
5.4.1 Control system fundamentals
5.4.2 Steady-state control
5.4.3 Dynamic control
5.4.4 Advanced control for load suppression
5.4.4.1 Load measurements as input for advanced control
5.4.4.2 Wind measurements as input for advanced control
5.4.4.3 Synthetic damping of wave-induced structural excitation
5.5 The future of offshore wind turbine technology
Acknowledgements
References
6 Marine solar energy
6.1 Solar cell technology
6.1.1 Semiconductor properties and growth
6.1.2 Semiconductor properties: the P – N junction
6.1.3 Crystalline solar cells
6.1.4 Thin film solar cells
6.2 Solar systems
6.2.1 Solar panels
6.3 Floating solar systems
6.3.1 Motivation
6.3.2 Components of a floating system
6.3.3 Chronology
6.3.4 Advantages and disadvantages
6.3.5 Systems at sea: motivation and special challenges
6.3.6 Systems at sea: current situation
6.3.6.1 The Solaqua Project (Malta)
6.3.6.2 Swimsol GmbH (Austria)
6.3.6.3 The Offshore Passive Photovoltaic Project (Malta)
6.3.6.4 Solar-at-Sea (The Netherlands)
6.3.7 Offshore solar: the future
References
7 Offshore support structure design
7.1 Offshore support structures
7.1.1 Bottom-fixed support structures
7.1.1.1 Gravity-based structures
7.1.1.2 Monopiles, jackets, and tripiles
7.1.2 Floating support structures
7.1.2.1 Spar platforms
7.1.2.2 Semisubmersible platforms and barges
7.1.2.3 Tension leg platforms
7.1.2.4 Mooring systems
7.2 Support structure design
7.2.1 Initial design
7.2.1.1 Scaling of wind or current turbines
7.2.1.2 Scaling of wave energy converters
7.2.2 Loads and load effects
7.2.2.1 Permanent loads
7.2.2.2 Variable loads
7.2.3 Short-term and long-term design analysis
7.2.3.1 Short-term analysis
7.2.3.2 Long-term analysis
7.2.4 Design standards, guidelines, and other considerations
7.2.4.1 ORE design standards
7.2.4.2 Other design considerations
References
8 Electrical power transmission and grid integration
8.1 Introduction
8.2 Implications of the grid-side converter topology on the grid integration of MECs
8.3 Impact of MECs' integration into power distribution systems
8.3.1 Power quality issues in marine energy installations
Voltage variations
Voltage fluctuations (flicker)
Unbalance
Waveform distortion
Frequency variation
Reactive power
8.3.2 System impact of marine energy installations
8.3.3 Case study
8.4 Impact of MECs' integration into power transmission systems
8.4.1 Additional ancillary services that can be provided by marine energy installations
Harmonic compensation
Low-voltage ride through
Black start
Power oscillation damping
8.4.2 Transmission technologies
HVAC versus HVDC technologies
Stability in DC power systems
8.4.3 Case study
8.4.4 Hybrid HVAC/DC systems and expansion planning
References
9 Offshore energy storage
9.1 Underwater compressed air energy storage
9.1.1 How much exergy is stored per unit volume of air containment
9.1.2 Corrections for air density and non-ideal gas behaviour
9.1.3 Structural capacity and its relevance to energy storage
9.1.4 Exergy versus structural capacity for underwater containments
9.1.5 The air ducts
9.1.6 Using thermal storage in conjunction with air storage
9.1.7 An example system design
9.1.8 Sites available for UWCAES
9.2 Offshore pumped hydro
9.2.1 Exergy storage density for UWPH
9.2.2 Key distinctions between UWPH and UWCAES
9.2.3 The EC2SC ratio for UWPH
9.3 Buoyancy energy storage systems
9.4 Offshore thermal energy storage systems
9.5 Other concepts
9.6 Integrating offshore energy storage with generation
References
10 Multipurpose platforms
10.1 Introduction
10.1.1 Context
10.1.2 Why multipurpose platforms?
10.1.2.1 Potential synergies
10.2 Multipurpose platform projects and concepts
10.2.1 EU projects
10.3 Design and analysis of multipurpose platforms
10.3.1 Multidisciplinary design methodology
10.3.2 Resource assessment: combined wind-wave resources
10.3.3 Modelling and analysis
10.4 Conclusions
References
11 Installation, operation and maintenance of offshore renewables
11.1 Introduction
11.1.1 Impact of installation, operation and maintenance activities in offshore renewable systems
11.1.2 Functional decomposition of offshore renewable systems
11.1.3 Concepts of reliability and failure analysis
11.2 Life cycle activities for offshore energy systems
11.2.1 Installation phase
11.2.1.1 Subsea power cable installation
11.2.1.2 Cable-to-cable connection
11.2.1.3 Offshore substation installation
11.2.1.4 Cable-to-device connection
11.2.1.5 Foundations
11.2.1.6 Mooring systems
11.2.1.7 Offshore renewable energy devices
11.2.2 Operation and maintenance phase
11.2.2.1 Inspection and monitoring
11.2.2.2 On-site interventions
11.2.2.3 Onshore interventions
11.2.3 Decommissioning phase
11.2.4 Vessels and equipment
11.3 Planning the operations
11.3.1 Strategies for planning the operations
11.3.2 Weather windows
11.3.3 Estimation of the delay time
11.3.4 Offshore standards and technical recommendations for operations
11.4 Economic modelling of installation, operation and maintenance
References
12 Challenges and future research
12.1 Challenge one – proving it
12.2 Challenge two – keeping it working
12.3 Challenge three – technical improvements
12.3.1 Servicing
12.3.2 Access
12.3.3 Data
12.3.4 Materials
12.4 Challenge four – environmental acceptability
12.5 Challenge five – social acceptability
12.6 Challenge six – making it work commercially
12.7 Challenge seven – getting the price down
12.8 Challenge eight – public support required
12.8.1 Financing arrays
12.8.2 Market pull
12.9 Challenge nine – market development
12.10 Challenge ten – making it happen
References
Index
Back Cover