IEC TS 62600-2:2016

IEC TS 62600-2 ®
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 2: Design requirements for marine energy systems

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IEC TS 62600-2 ®
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –

Part 2: Design requirements for marine energy systems

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-3580-5

– 2 – IEC TS 62600-2:2016 © IEC 2016

CONTENTS
FOREWORD . 8

INTRODUCTION . 10

1 Scope . 11

1.1 General . 11

1.2 Applications . 11

2 Normative references. 12

3 Terms and definitions . 13

4 Symbols and abbreviated terms . 13
5 General considerations . 15
5.1 General . 15
5.2 Regulations . 15
5.3 Suitability and/or relevance of standards . 15
5.4 Quality assurance and quality control . 15
5.5 Safety levels . 16
5.6 Design principles – structure and foundations . 17
5.7 Load definition and load combinations . 17
5.8 Other considerations . 18
5.8.1 Stability and watertight integrity . 18
5.8.2 Electrical, mechanical, instrumentation and control systems . 18
5.8.3 Reliability issues . 18
5.8.4 Corrosion protection . 18
5.8.5 Design for operation, inspection, maintenance and decommissioning . 18
5.9 Operational and structural resonance . 18
5.10 Basis of design . 19
6 External conditions . 19
6.1 General . 19
6.2 Waves . 19
6.2.1 Normal sea state (NSS). 19
6.2.2 Normal wave height (NWH) . 19
6.2.3 Extreme sea state (ESS) . 20
6.2.4 Extreme wave height (EWH) . 20
6.2.5 Breaking waves . 21

6.2.6 Wave run-up . 21
6.3 Sea currents . 21
6.3.1 General . 21
6.3.2 Sub-surface currents . 21
6.3.3 Wind-generated near-surface currents . 22
6.3.4 Tidal currents . 22
6.3.5 Breaking wave-induced surf currents . 22
6.3.6 Normal current model (NCM) . 23
6.3.7 Extreme current model (ECM) . 23
6.3.8 Normal turbulence model (NTM) . 23
6.3.9 Extreme turbulence model (ETM) . 23
6.4 Wind conditions . 24
6.5 Water level. 24
6.5.1 General . 24

6.5.2 Normal water level range (NWLR) . 25

6.5.3 Extreme water level range (EWLR) . 25

6.6 Sea and river ice . 25

6.7 Earthquakes . 26

6.8 Marine growth . 26

6.9 Seabed movement and scour . 26

6.10 Ship collisions . 26

6.11 Other environmental conditions . 26

7 Loads and load effects . 26

7.1 General . 26
7.2 Loads . 26
7.3 Design situations and load cases . 28
7.3.1 General . 28
7.3.2 Interaction with waves, currents, wind, water level and ice . 28
7.3.3 Design categories . 29
7.3.4 Limit states . 29
7.3.5 Partial safety factors . 30
7.3.6 Simulation requirements . 31
7.3.7 Design conditions . 32
8 Materials . 40
8.1 General . 40
8.2 Material selection criteria . 41
8.3 Environmental considerations . 42
8.4 Structural materials . 42
8.4.1 General . 42
8.4.2 Metals . 42
8.4.3 Concrete . 43
8.4.4 Composites . 43
8.5 Compatibility of materials . 45
9 Design of primary structures for wave and tidal/current energy converters . 45
9.1 General . 45
9.2 Design of steel structures . 45
9.2.1 General . 45
9.2.2 Load and resistance factor design (LRFD) . 46
9.2.3 Ultimate limit state . 46

9.2.4 Fatigue limit state . 47
9.2.5 Serviceability limit state . 47
9.3 Design of concrete structures . 47
9.3.1 General . 47
9.3.2 Limit states . 47
9.3.3 Bending moment and axial force . 48
9.3.4 Slender structural members . 48
9.3.5 Transverse shear . 48
9.3.6 Torsional moments . 48
9.3.7 Bond strength and anchorage failure . 48
9.3.8 Fatigue limit state . 48
9.3.9 Serviceability limit state . 49
9.3.10 Stresses in pre-stressed reinforcement . 49
9.3.11 Stresses in concrete . 49

– 4 – IEC TS 62600-2:2016 © IEC 2016

9.3.12 Detailing of reinforcement . 49

9.3.13 Corrosion control . 49

9.4 Design of grouted connections . 49

9.4.1 General . 49

9.4.2 Design principles . 49

9.5 Design of composite structures . 49

9.5.1 General . 49

9.5.2 Design principles . 50

9.5.3 Joints and interfaces . 52

10 Electrical, mechanical, instrumentation and control systems . 52

10.1 Overview. 52
10.2 General requirements . 52
10.3 Abnormal operating conditions safeguard . 53
11 Mooring and foundation considerations . 54
11.1 Overview. 54
11.1.1 General . 54
11.1.2 Unique challenges for wave energy converters . 54
11.1.3 Unique challenges for tidal energy converters . 54
11.2 Tethered floating structures . 54
11.3 Fixed structures . 55
11.4 Compound MEC structures . 55
12 Inspection requirements . 57
12.1 General . 57
12.2 Consideration during the design stage . 57
12.3 Inspection and maintenance planning . 58
12.4 Data management . 58
12.5 Condition assessment and integrity evaluation (against performance
requirements) . 59
12.6 Maintenance execution . 59
13 Life cycle considerations . 60
13.1 General . 60
13.2 Planning . 62
13.2.1 General . 62
13.2.2 Installation conditions . 62
13.2.3 Site access . 62

13.2.4 Environmental conditions . 62
13.3 Documentation . 63
13.4 Receiving, handling and storage . 63
13.5 Assembly of and installation of MECs . 63
13.5.1 General . 63
13.5.2 Access . 64
13.6 Fasteners and attachments . 64
13.7 Cranes, hoists and lifting equipment . 64
13.8 Decommissioning . 64
Annex A (normative) Load definition and load combinations . 66
A.1 Load combinations . 66
A.2 Load calculations . 67
A.3 Floating and moored devices . 69

A.4 Flow analysis methodology . 69

Annex B (normative) Reliability issues . 71

B.1 General . 71

B.2 Structure and foundation . 71

B.3 Mechanical system . 71

B.4 Electrical system . 72

B.5 Control and protection system . 72

B.6 Instrumentation . 72

B.7 Testing during qualification . 72

Annex C (normative) Corrosion protection . 73
C.1 General . 73
C.2 Steel structures . 73
C.2.1 General . 73
C.2.2 Corrosion rates . 74
C.2.3 Protective coatings . 74
C.3 Cathodic protection . 74
C.3.1 General . 74
C.3.2 Closed compartments. 75
C.3.3 Stainless steel . 75
C.4 Concrete structures . 75
C.4.1 General . 75
C.4.2 Provision of adequate cover . 75
C.4.3 Use of stainless steel or composite reinforcement . 76
C.4.4 Cathodic protection of reinforcement . 76
C.5 Non-ferrous metals . 76
C.6 Composite structures . 77
C.7 Compatibility of materials . 77
C.8 Chains, steel wire and fibre rope . 77
Annex D (normative) Operational and structural resonance . 78
D.1 General . 78
D.2 Control systems . 78
D.3 Exciting frequencies . 78
D.4 Natural frequencies . 78
D.5 Analysis . 79
D.6 Balancing of the rotating components . 79

Annex E (informative) Requirements for a basis of design. 80
E.1 General . 80
E.2 Design life . 82
E.3 Design standards . 82
E.4 Regional regulations . 82
E.5 Environmental conditions . 82
E.5.1 General . 82
E.5.2 Meteorology and climatology . 82
E.5.3 Air/water conditions . 82
E.5.4 Water level . 83
E.5.5 Currents . 83
E.5.6 Waves . 83

– 6 – IEC TS 62600-2:2016 © IEC 2016

E.5.7 Marine life . 83

E.6 Seabed conditions . 83

E.6.1 General . 83

E.6.2 Bathymetry and coastal topography . 83

E.7 Material standards and testing . 84

Annex F (informative) Wave spectrum . 85

F.1 Overview. 85

F.2 The Pierson-Moskowitz spectrum . 85

F.3 Relationship between peak and zero crossing periods . 88

F.4 Wave directional spreading . 88
Annex G (informative) Shallow water hydrodynamics and breaking waves . 89
G.1 Selection of suitable wave theories . 89
G.2 Modelling of irregular wave trains . 90
G.3 Breaking waves . 90
Annex H (informative) Guidance on calculation of hydrodynamic loads . 93
H.1 General . 93
H.2 Large bodies . 94
H.3 Hybrid structures . 94
H.4 Short term statistics . 95
H.5 Breaking wave loads . 95
H.6 Dynamic loads due to turbulent flow . 96
Bibliography . 97

Figure 1 – Definition of water levels (see IEC 61400-3) . 24
Figure 2 – Examples of compound position mooring systems for wave (a, b) and tidal
(c, d) energy conversion systems . 56
Figure C.1 – Profile of the thickness loss resulting from corrosion of an unprotected
steel structure in seawater (1 mil = 0,025 4 mm) . 73
Figure E.1 – Quality assurance system . 81
Figure F.1 – PM spectrum . 86
Figure F.2 – JONSWAP and PM spectrums for typical North Sea storm sea state . 87
Figure G.1 – Regions of applicability of stream functions, stokes V, and linear wave
theory . 89
Figure G.2 – Breaking wave height dependent on still water depth . 91

Figure G.3 – Transitions between different types of breaking waves as a function of
seabed slope, wave height in deep waters and wave period . 92
Figure H.1 – Relative importance of mass, viscous drag and diffraction forces on
marine structures . 93

Table 1 – Safety levels. 16
Table 2 – Types of loads that shall be considered . 27
Table 3 – ULS combinations of uncorrelated extreme events . 29
Table 4 – Design categories . 29
Table 5 – ULS partial load safety factors γ for design categories . 31
f
Table 6 – Design load cases for WEC . 33
Table 7 – Design load cases for TEC . 35
Table 8 – ISO test standards . 44

Table 9 – Material factors γ for buckling . 46

M
Table 10 – Summary of model factors . 52

– 8 – IEC TS 62600-2:2016 © IEC 2016

INTERNATIONAL ELECTROTECHNICAL COMMISSION

____________
MARINE ENERGY – WAVE, TIDAL AND

OTHER WATER CURRENT CONVERTERS –

Part 2: Design requirements for marine energy systems

FOREWORD
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
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9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.

The main task of IEC technical committees is to prepare International Standards. In
exceptional circumstances, a technical committee may propose the publication of a Technical
Specification when
• the required support cannot be obtained for the publication of an International Standard,
despite repeated efforts, or
• the subject is still under technical development or where, for any other reason, there is the
future but no immediate possibility of an agreement on an International Standard.
Technical Specifications are subject to review within three years of publication to decide
whether they can be transformed into International Standards.
IEC TS 62600-2, which is a Technical Specification, has been prepared by IEC technical
committee 114: Marine energy – Wave, tidal and other water current converters.

The text of this Technical Specification is based on the following documents:

Enquiry draft Report on voting

114/168/DTS 114/176A/RVC
Full information on the voting for the approval of this Technical Specification can be found in

the report on voting indicated in the above table.

This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.

A list of all parts in the IEC 62600 series, published under the general title Marine energy –
Wave, tidal and other water current converters, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC website under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
• transformed into an International Standard,
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.
A bilingual version of this publication may be issued at a later date.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates
that it contains colours which are considered to be useful for the correct
understanding of its contents. Users should therefore print this document using a
colour printer.
– 10 – IEC TS 62600-2:2016 © IEC 2016

INTRODUCTION
This part of IEC 62600 outlines minimum design requirements for marine energy converters

and is not intended for use as a complete design specification or instruction manual.

Several different parties may be responsible for undertaking the various elements of the

design, manufacture, assembly, installation, erection, commissioning, operation and

maintenance of a marine energy system and for ensuring that the requirements of this

document are met. The division of responsibility between these parties is a contractual matter

and is outside the scope of this document.

Any of the requirements of this document may be altered if it can be suitably demonstrated
that the safety of the system is not compromised. Compliance with this document does not
relieve any person, organization, or corporation from the responsibility of observing other
applicable regulations.
MARINE ENERGY – WAVE, TIDAL AND

OTHER WATER CURRENT CONVERTERS –

Part 2: Design requirements for marine energy systems

1 Scope
1.1 General
This part of IEC 62600 provides the essential design requirements to ensure the engineering
integrity of wave, tidal and other water current energy converters, referred to as marine
energy converters (MECs), for a specified design life. Its purpose is to provide an appropriate
level of protection against damage from all hazards that may lead to failure of the primary
structure, defined as the collective system comprising the structural elements, foundation,
mooring and anchors, piles, and device buoyancy designed to resist global loads.
This document includes requirements for subsystems of MECs such as control and protection
mechanisms, internal electrical systems, mechanical systems and mooring systems as they
pertain to the structural viability of the device under site-specific external environmental
conditions. This document applies to wave, tidal and other water current converters and to
structures that are either floating or fixed to the seafloor or shore. This document applies to
structures that are unmanned during operational periods.
This document addresses site-specific conditions, safety factors for critical structures and
structural interfaces, external load cases (including extreme load magnitude, duration, and
frequency), failure probability and failure consequences for critical structures and structural
interfaces (overall risk assessment), and failsafe design practices (demonstration of adequate
redundancy). The effect of subsystem failure on the primary structure is also addressed.
This document does not address the effects of MECs on the physical or biological
environment (unless noted by exception). This document is used in conjunction with the
appropriate IEC and ISO standards, as well as regional regulations that have jurisdiction over
the installation site.
1.2 Applications
This document is applicable to MEC systems designed to operate from ocean, tidal and river
current energy sources, but not systems associated with hydroelectric impoundments or

barrages. This document is also applicable to wave energy converters. It is not applicable to
ocean thermal energy conversion (OTEC) systems or salinity gradient systems.
Although important to the overall objectives of the IEC 62600 series, this document does not
address all aspects of the engineering process that are taken into account during the full
system design of MEC systems. Specifically, this document does not address energy
production, performance efficiency, environmental impacts, electric generation and
transmission, ergonomics, or power quality.
This document, to the extent possible, adapts the principles of existing applicable standards
already in use throughout the marine industry (structure, moorings, anchors, corrosion
protection, etc.) and by reference, defers to the appropriate international documents. This
document adheres to a Load Resistance Factor Design (LRFD) approach and the principles of
limit state design as described in ISO 2394.
MECs designed to convert hydrokinetic energy from significant hydrodynamic forces into other
forms of usable energy, such as electrical, hydraulic, or pneumatic may be different from

– 12 – IEC TS 62600-2:2016 © IEC 2016

other types of marine structures. Many MECs are designed to operate in resonance or

conditions close to resonance. Furthermore, MECs are hybrids between machines and marine

structures. The control forces imposed by the power takeoff (PTO) and possible forces from

faults in the operation of the PTO distinguish MECs from other marine structures.

The goal of this document is to adequately address relevant design considerations for MECs

that have progressed to an advanced prototype design stage or beyond. This refers to

technology concepts that have been proven either through analysis, open water test data,

scale model testing in tanks or dry land test facilities, and that are ready for

commercialization. It is anticipated that this document will be used in certification schemes for
design conformity.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
IEC 60812, Analysis techniques for system reliability – Procedure for failure mode and effects
analysis (FMEA)
IEC 61400-1, Wind turbines – Part 1: Design requirements
IEC 61643-11, Low voltage surge protective devices – Part 11: Surge protective devices
connected to low-voltage power systems – Requirements and test methods
IEC 62305-3, Protection against lightning – Part 3: Physical damage to structures and life
hazard
IEC TS 62600-1, Marine energy – Wave, tidal and other water current converters – Part 1:
Terminology
IEC TS 62600-10, Marine energy – Wave, tidal and other water current converters – Part 10:
Assessment of mooring system for marine energy converters (MECs)
ISO 527-1, Plastics – Determination of tensile properties – Part 1: General principles
ISO 2394, General principles on reliability for structures

ISO 12473, General principles of cathodic protection in sea water
ISO 13003, Fibre-reinforced plastics – Determination of fatigue properties under cyclic loading
condition
...