Marine energy - Wave, tidal and other water current converters - Part 102: Wave energy converter power performance assessment at a second location using measured assessment data

IEC TS 62600-102:2016(E) describes the required methods and the required conditions to determine the power performance of the Wave Energy Converter 2 (WEC 2) in Location 2, possibly at a different scale and with configuration changes to accommodate the new site conditions, in all cases based on measured power performance of WEC 1 in Location 1. This technical specification allows for assessment at Location 1 or Location 2 based on limited/incomplete data material, as long as this is accompanied by a validated numerical model or physical model and assessment of the uncertainty involved. Another key element is transparency in the assessment.

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Status
Published
Publication Date
08-Aug-2016
Current Stage
PPUB - Publication issued
Start Date
09-Aug-2016
Completion Date
09-Aug-2016
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IEC TS 62600-102:2016 - Marine energy - Wave, tidal and other water current converters - Part 102: Wave energy converter power performance assessment at a second location using measured assessment data
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IEC TS 62600-102
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 102: Wave energy converter power performance assessment at a second
location using measured assessment data
IEC TS 62600-102:2016-08(en)
---------------------- Page: 1 ----------------------
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IEC TS 62600-102
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 102: Wave energy converter power performance assessment at a second
location using measured assessment data
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.140 ISBN 978-2-8322-3530-0

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC TS 62600-102:2016 © IEC 2016
CONTENTS

FOREWORD ......................................................................................................................... 4

INTRODUCTION ................................................................................................................... 6

1 Scope ............................................................................................................................ 7

2 Normative references..................................................................................................... 7

3 Symbols and units ......................................................................................................... 8

4 Sequence of work .......................................................................................................... 9

5 Limitations of this technical specification ...................................................................... 10

6 Description of wave energy conversion (WEC) technology ............................................ 10

7 Assess and characterize wave resource related to Location 1 and Location 2 ............... 10

7.1 General ............................................................................................................... 10

7.2 Ambient condition ............................................................................................... 10

7.3 Wave resource at Location 1 and Location 2 ........................................................ 10

8 WEC power capture data at Location 1 ......................................................................... 10

9 WEC model validation .................................................................................................. 11

9.1 General ............................................................................................................... 11

9.2 Bin selection ....................................................................................................... 11

9.3 Error per bin........................................................................................................ 11

9.4 MAEP error ......................................................................................................... 11

9.5 Accounting for PTO losses .................................................................................. 12

10 Modifications to the WEC ............................................................................................. 12

11 Calculate capture length matrix for use at Location 2 .................................................... 13

11.1 Evaluate appropriate dimensionality of the capture length matrix at Location 2 ........ 13

11.2 Calculate information for each bin of the capture length matrix ............................. 13

12 Quality assurance for cells based on measurements at Location 1 ................................ 14

13 Complement capture length matrix to cover range of conditions at Location 2 ............... 14

13.1 Capture length matrix complementation requirement ............................................ 14

13.2 Interpolation or extrapolation of the capture length matrix .................................... 14

13.3 Numerical model ................................................................................................. 14

13.4 Use of physical model ......................................................................................... 14

14 Calculate MAEP at Location 2 using complemented capture length matrix and

Location 2 resource data ............................................................................................. 15

15 Assessment of confidence ........................................................................................... 15

Annex A (informative) Example analysis ............................................................................. 17

A.1 General ............................................................................................................... 17

A.2 Description of the WEC technology (Clause 6) ..................................................... 17

A.3 Assess and characterize wave resource related to Location 1 and Location

2 (Clause 7) ........................................................................................................ 18

A.4 Assess and characterize wave resource at Location 1 .......................................... 19

A.5 Assess and characterize wave resource at Location 2 .......................................... 20

A.6 WEC power capture data at Location 1 (Clause 8) ............................................... 21

A.7 WEC model validation (Clause 9) ........................................................................ 22

A.8 Calculate capture length matrix for use at Location 2 (Clause 11) ......................... 24

A.8.1 Assess the appropriate dimensionality of the capture length matrix at

Location 2 (11.1) .......................................................................................... 24

A.8.2 Calculate information for each bin of the capture length matrix (11.2) ............ 24

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IEC TS 62600-102:2016 © IEC 2016 – 3 –
A.9 Perform quality assurance on capture length matrix for application at

Location 2 (Clause 12) ........................................................................................ 24

A.10 Complement capture length matrix to cover range of conditions at Location 2

(Clause 13) ......................................................................................................... 25

A.11 Calculate MAEP at Location 2 using complemented capture length matrix

and Location 2 resource data (Clause 14) ............................................................ 26

A.12 Assessment of confidence ................................................................................... 26

Annex B (informative) Power take off efficiency .................................................................. 27

B.1 General ............................................................................................................... 27

B.2 Absorbed power .................................................................................................. 27

B.3 Power take off efficiency ..................................................................................... 27

Annex C (informative) Example calculation of PTO efficiency .............................................. 29

Annex D (informative) Sources of uncertainty for MAEP at Location 2 ................................. 31

D.1 Comparisons between Location 1 and Location 2 ................................................. 31

D.2 Bathymetry and water depth ................................................................................ 31

D.3 Current ............................................................................................................... 31

D.4 Wave spectrum ................................................................................................... 32

D.5 Wave direction and short-crested waves .............................................................. 32

D.6 Wave converter modifications .............................................................................. 32

Bibliography ....................................................................................................................... 33

Figure A.1 – The Wavestar prototype (diameter of each float is 5 m) .................................... 17

Figure A.2 – Map showing Location 1 Hanstholm and Location 2 Fjatring ............................. 18

Figure A.3 – Location 1 Wave Energy Flux Matrix, Hantsholm, Denmark (based on

measured data from Wavestar prototype Feb 2012 – Jan 2013) ........................................... 20

Figure A.4 – Location 2 Wave Energy Flux Matrix, Buoy 2031 (Fjaltring, Denmark) .............. 21

Figure A.5 – Wavestar prototype capture length matrix Location 1 ....................................... 22

Figure A.6 – Numerically modelled electrical power matrix, adapted from [2] ........................ 23

Figure A.7 – Model validation indicating percent difference in capture length between

observations and model (model-observations) ..................................................................... 24

Figure A.8 – Wavestar prototype capture length matrix for Loaction 2. Fjaltring,

Denmark ............................................................................................................................. 25

Figure B.1 – Overview of the PTO system used in the prototype of Wavestar ....................... 27

Figure C.1 – PTO efficiency matrix for the Wavestar prototype at Location 1,

Hantsholm, Denmark .......................................................................................................... 30

Table 1 – Symbols and units ................................................................................................. 8

Table A.1 – Locations 1 and 2, basic information ................................................................. 18

Table A.2 – Table of MAEP contributions............................................................................. 26

Table C.1 – Example records including wave conditions, absorbed and electrical

power and resultant PTO efficiency ..................................................................................... 29

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– 4 – IEC TS 62600-102:2016 © IEC 2016
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARINE ENERGY – WAVE, TIDAL AND
OTHER WATER CURRENT CONVERTERS –
Part 102: Wave energy converter power performance assessment
at a second location using measured assessment data
FOREWORD

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all national electrotechnical committees (IEC National Committees). The object of IEC is to promote

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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is

indispensable for the correct application of this publication.

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 62600-102, which is a technical specification, has been prepared by IEC technical

committee 114: Marine energy – Wave, tidal and other water current converters.
---------------------- Page: 6 ----------------------
IEC TS 62600-102:2016 © IEC 2016 – 5 –
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
114/179/DTS 114/187A/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.
---------------------- Page: 7 ----------------------
– 6 – IEC TS 62600-102:2016 © IEC 2016
INTRODUCTION

This technical specification, IEC TS 62600-102, provides a uniform methodology for

estimating and reporting the performance of a Wave Energy Converter (WEC) at a

prospective new deployment location. The performance estimation methodology is based

primarily on observations and measurement results gathered during field deployment of the

WEC at a primary location (as per IEC TS 62600-100) with different metocean conditions

compared to the prospective new location. Further, it is possible that the WEC design will

incorporate changes to accommodate the new site conditions. To assess the performance,

inclusion of additional information based on validated numerical and physical models is

specified. In this technical specification the completed field deployment location is referred to

as “Location 1” and the prospective deployment location is referred to as “Location 2.”

The specification provides a methodology for arriving at the mean annual energy production

(MAEP) for the WEC at Location 2. Other Technical Specifications in this series
(IEC TS 62600) are drawn upon to provide the wave resource and WEC performance
information needed to enable this analysis. The methodology involves:
• assessment of the wave resource at Location 1 and Location 2,
• characterization of the WEC performance at Location 1,

• assessment and compensation for the impact of discrepancies in the metocean conditions

between Location 1 and Location 2 on the WEC performance characterization,

• assessment of the impact of changes to the WEC configuration between Location 1 and

Location 2 on the WEC performance characterization,

• complementing the performance observations from Location 1 with fit, experimental or

numerically modelled data,

• estimating the MAEP based on the composite performance characterization of the WEC.

This technical specification provides:
a) guidance on the use of observations from Location 1,

b) methods for assessing and reporting the validity of numerical and physical models,

c) limits on the permissible changes to the WEC between Locations 1 and 2,
d) limits on the use of data fitting techniques, and
e) requirements for reporting.

The wave power industry is at an early stage of development. There is little practical

experience with field-scale WECs deployment. Because of this, the present document is

designated as a technical specification and will be subject to change as more data is collected

and experience with wave energy converters develops. This Technical Specification, when

used in conjunction with other Technical Specifications in this series (IEC TS 62600), is

intended for several types of users, including, but not limited to, the following:

• Project developers – income, return on investment
• Device developers – performance of device

• Utilities/investors – reliability/predictability of supply, return on investment

• Policy-makers/Planners – usage of seascape, optimisation of resource, power supply

issues

• Consultants to produce resource data/due diligence – compatible/readable data format

---------------------- Page: 8 ----------------------
IEC TS 62600-102:2016 © IEC 2016 – 7 –
MARINE ENERGY – WAVE, TIDAL AND
OTHER WATER CURRENT CONVERTERS –
Part 102: Wave energy converter power performance assessment
at a second location using measured assessment data
1 Scope

Wave Energy Converters (WEC) need to be designed to operate efficiently at different

locations. Systematic methods should be used to evaluate the power performance of a WEC

at a second location (hereinafter Location 2) based on power performance assessment at a

first location (hereinafter Location 1). The degree of similarity of the measured WEC (WEC 1)

and the metocean conditions at Location 1 to the secondary WEC (WEC 2) at Location 2

determine the methodology and the applicability of this technical specification.

This part of IEC 62600, which is a Technical Specification, describes the required methods

and the required conditions to determine the power performance of the WEC 2 in Location 2,

possibly at a different scale and with configuration changes to accommodate the new site

conditions, in all cases based on measured power performance of WEC 1 in Location 1. This

technical specification allows for assessment at Location 1 or Location 2 based on

limited/incomplete data material, as long as this is accompanied by a validated numerical

model or physical model and assessment of the uncertainty involved. Another key element is

transparency in the assessment.
This technical specification includes:

a) Specification of data requirements needed from the original measurements at Location 1

including an assessment of the uncertainty involved (if based on limited/incomplete data

material) in addition to those specified in IEC TS 62600-100 and IEC TS 62600-101.

b) Limitation on the changes that are allowed to the WEC and the specification of the

location.
c) Wave data required at Location 2, as a minimum the requirements found in IEC
TS 62600-101.
d) Development of the power matrix at Location 2.
e) Validation of the power matrix at Location 2.

f) Assessment of uncertainties in the derived performance parameters at Location 2.

g) Requirements for the allowable power performance transfer by geometric, kinematic and

dynamic similarity.

h) Requirements for the allowable incorporation of additional empirical model data.

i) Requirements for the allowable incorporation of additional numerical model data.

The technical specification does not cover the following items:
j) The original data measurement at Location 1 (see IEC TS 62600-100).
k) Environmental concerns.
l) Operation and maintenance.
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

---------------------- Page: 9 ----------------------
– 8 – IEC TS 62600-102:2016 © IEC 2016

cited applies. For undated references, the latest edition of the referenced document (including

any amendments) applies.

IEC TS 62600-1, Marine energy – Wave, tidal and other water current converters – Part 1:

Terminology

IEC TS 62600-100, Marine energy – Wave, tidal and other water current converters –

Part 100: Electricity producing wave energy converters – Power performance assessment

IEC TS 62600-101:2015, Marine energy – Wave, tidal and other water current converters –

Part 101: Wave energy resource assessment and characterization

International Towing Tank Conference (ITTC), Recommended Guidelines 7.5-02-07-03.7,

Wave Energy Converter Model Test Experiments
3 Symbols and units

For the purposes of this technical specification, the symbols and units listed in Table 1 apply.

The terms and definitions are in accordance with IEC TS 62600-1.
– Symbols and units
Table 1
Symbol Definition Units
Group velocity m/s
Direction of maximum directionally resolved wave
θ deg
Jmax
power
f Frequency Hz
f Frequency at component i Hz
Water depth m
H Spectral estimate of significant wave height m
H Significant wave height m
Omnidirectional measured wave power W/m
J Omnidirectional measured wave power per bin W/m
Average wave power W/m
Minimum wave power W/m
∧ J
Maximum wave power W/m
∨ J
Capture length m
L Capture length per bin m
Average capture length m
Minimum capture length m
∧ L
Maximum capture length m
∨ L
MAEP Mean Annual Energy Production
W⋅h
n Number of records -
N Number of bins -
P Measured power output W
P Measured power output per bin W
P Hydraulic power input W
---------------------- Page: 10 ----------------------
IEC TS 62600-102:2016 © IEC 2016 – 9 –
Symbol Definition Units
S Spectral density
S(f) Spectral density as function of frequency
Directional spectrum as a function of frequency and
direction
S(f, θ)
Hz⋅ rad
S( f )⋅ G(θ, f )
S Spectral density at frequency component i
T Energy period s
f Frequency spacing Hz
θ Wave direction Deg
P Absorbed power W
abs
P Electrical power output W
P Power loss (dissipated) in the PTO W
pto
η Power take off efficiency -
pto
ρ Density kg/m
σ Standard deviation -
4 Sequence of work
The sequence of the work is outlined below:
a) Describe the WEC technology.

b) Assess and characterize wave resource at Location 1 and Location 2 using IEC TS 62600-

101.

c) Calculate the capture length matrix from WEC power capture data at Location 1 using IEC

TS 62600-100.

d) Evaluate the appropriate dimensionality of the capture length matrix from Location 1 for

Location 2 and complement the capture length matrix from Location 1 to cover the range

of metocean conditions at Location 2 using numerical or experimental data.
e) Validate the model against measured data from Location 1.
f) Specify changes to the WEC to accommodate the new metocean conditions.

g) Evaluate the impact of changes to the capture length of each bin using validated

numerical model data incorporating the parameters in question. If the capture length in a

bin is changed by more than 10 % it shall be filled using physical or numerical modelled

data.

h) Perform quality assurance on capture length matrix for application at Location 2.

i) Calculate MAEP at Location 2 using the complemented capture length matrix and
Location 2 resource data.

j) Report separately the MAEP at Location 2 contributed by the cells of the power matrix that

are based on either:
1) measured data at Location 1, or
2) interpolation or extrapolation from measured data, or
3) modelled data.
k) Estimate the uncertainty related to the MAEP calculated at Location 2.
---------------------- Page: 11 ----------------------
– 10 – IEC TS 62600-102:2016 © IEC 2016

Annex A provides a detailed illustration of the concepts and calculations in each step in the

sequence of work.
5 Limitations of this technical specification

This specification allows for changes to the WEC when moved from Location 1 to Location 2

in order to accommodate the new metocean conditions. Changes to the WEC should be

clearly specified and may include: dimensions, geometry, power take off system, control logic

and moorings system. Allowable changes and procedures are specified in Clause 10.

6 Description of wave energy conversion (WEC) technology

The wave energy converter WEC 1 deployed at Location 1 and the WEC 2 to be deployed at

Location 2 shall both be described in terms of:
• Operational principle.
• Geometry and dimensions.
• Mass properties.
• PTO system.
• Mooring arra
...

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