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
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