Marine energy - Wave, tidal and other water current converters - Part 100: Electricity producing wave energy converters - Power performance assessment

IEC/TS 62600-100:2012(E) provides a method for assessing the electrical power production performance of a Wave Energy Converter (WEC), based on the performance at a testing site. Provides a systematic method which includes:
- measurement of WEC power output in a range of sea states;
- WEC power matrix development;
- an agreed framework for reporting the results of power and wave measurements.
The contents of the corrigendum of April 2017 have been included in this copy.

General Information

Status
Published
Publication Date
29-Aug-2012
Current Stage
PPUB - Publication issued
Start Date
30-Aug-2012
Completion Date
30-Aug-2012
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IEC TS 62600-100:2012 - Marine energy - Wave, tidal and other water current converters - Part 100: Electricity producing wave energy converters - Power performance assessment
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IEC/TS 62600-100
Edition 1.0 2012-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 100: Electricity producing wave energy converters – Power performance
assessment
IEC/TS 62600-100:2012(E)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC/TS 62600-100
Edition 1.0 2012-08
TECHNICAL
SPECIFICATION
colour
inside
Marine energy – Wave, tidal and other water current converters –
Part 100: Electricity producing wave energy converters – Power performance
assessment
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
PRICE CODE
ICS 27.140 ISBN 978-2-83220-330-9

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – TS 62600-100 © IEC:2012(E)
CONTENTS

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

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

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

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

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

4 Sequence of work ........................................................................................................... 10

5 Test site characterization ............................................................................................... 10

5.1 General ................................................................................................................. 10

5.2 Measurements ....................................................................................................... 10

5.2.1 Wave measurement for wave power .......................................................... 10

5.2.2 Current measurement ................................................................................ 11

5.2.3 Tidal measurement .................................................................................... 11

5.2.4 Bathymetric survey .................................................................................... 11

5.2.5 Calculation of wave spatial transfer model ................................................. 11

5.2.6 Modelling of the test site ............................................................................ 11

6 Methodology ................................................................................................................... 12

6.1 General ................................................................................................................. 12

6.2 Sample duration and frequency ............................................................................. 12

6.3 Simultaneity .......................................................................................................... 13

6.4 Data recording....................................................................................................... 13

6.4.1 Amount of data to be recorded .................................................................. 13

6.4.2 Data format and retaining .......................................................................... 13

7 Measurement and data collection for wave data ............................................................. 13

7.1 General ................................................................................................................. 13

7.2 WMI and calibration ............................................................................................... 13

7.3 Instrumentation location ........................................................................................ 13

7.3.1 General ..................................................................................................... 13

7.3.2 Direct measurement .................................................................................. 13

7.3.3 Measures with spatial transfer model ......................................................... 14

7.3.4 Correction for WEC interference ................................................................ 14

7.4 Metocean data ...................................................................................................... 14

7.5 Procedure for the calculation of derived parameters .............................................. 14

8 WEC power output measurements .................................................................................. 15

8.1 WEC output terminals ............................................................................................ 15

8.2 Power measurement point ..................................................................................... 15

8.3 Power measurements ............................................................................................ 16

8.3.1 General ..................................................................................................... 16

8.3.2 Limitations on power production ................................................................ 16

8.4 Instruments and calibration ................................................................................... 16

9 Determination of power performance .............................................................................. 17

9.1 General ................................................................................................................. 17

9.2 Structure of the normalized power matrix .............................................................. 17

9.2.1 Core structure ........................................................................................... 17

9.2.2 Sub-division of the normalized power matrix .............................................. 17

9.2.3 Calculation of the capture length ............................................................... 17

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TS 62600-100 © IEC:2012(E) – 3 –

9.2.4 Representation of the capture length matrix............................................... 17

9.3 Calculation of power matrix ................................................................................... 18

10 Calculation of mean annual energy production (MAEP) .................................................. 18

10.1 General ................................................................................................................. 18

10.2 Standard methodology........................................................................................... 18

10.3 Alternative methodology ........................................................................................ 19

10.4 Completeness of the capture length matrix for MAEP ............................................ 19

Annex A (informative) Example production of a normalized power matrix ............................. 20

Annex B (normative) Method for power loss compensation where the measurement

point is located on shore ....................................................................................................... 28

Annex C (normative) Evaluation of uncertainty ..................................................................... 31

Annex D (normative) Error analysis of the wave spatial transfer model ................................ 33

Bibliography .......................................................................................................................... 35

Figure 1 – Timeline of assessment ........................................................................................ 10

Figure 2 – Data flow diagram ................................................................................................ 12

Figure A.1 – Power scatter.................................................................................................... 21

Figure B.1 – Location options for metering equipment ........................................................... 28

Figure B.2 – Positive sequence cable model ......................................................................... 29

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

Table A.1 – Sample data ....................................................................................................... 20

Table A.2 – Average capture length ...................................................................................... 22

Table A.3 – Standard deviation of capture length .................................................................. 23

Table A.4 – Maximum capture length .................................................................................... 24

Table A.5 – Minimum capture length ..................................................................................... 25

Table A.6 – Number of data samples .................................................................................... 26

Table A.7 – Power matrix ...................................................................................................... 27

Table C.1 – List of uncertainty components .......................................................................... 31

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– 4 – TS 62600-100 © IEC:2012(E)
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
MARINE ENERGY –
WAVE, TIDAL AND OTHER WATER CURRENT CONVERTERS –
Part 100: Electricity producing wave energy converters –
Power performance assessment
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 62600-100, which is a technical specification, has been prepared by IEC technical

committee 114: Marine energy – Wave, tidal and other water current converters.
---------------------- Page: 6 ----------------------
TS 62600-100 © IEC:2012(E) – 5 –
The text of this technical specification is based on the following documents:
Enquiry draft Report on voting
114/87/DTS 114/95/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 web site 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.
The contents of the corrigendum of April 2017 have been included in this copy.
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 – TS 62600-100 © IEC:2012(E)
INTRODUCTION

This part of IEC 62600, which is a Technical Specification, provides performance assessment

methods for Wave Energy Conversion Systems (WECS). A Wave Energy Converter (WEC) is

a device which generates electricity using the action of water waves and delivers electricity to

an electrical load.

Wave energy industry development is transitioning from preliminary stages to commercial

production stages. Validated data gathering and processing techniques are important to

improve existing technologies. This technical specification will be subject to changes as data

are collected and processed from testing of WECS.
The expected users of the specification include:
• device developers who want to validate the performance of their WEC;
• investors who want to assess the performance of a device developer’s WEC;
• project developers who want to assess the performance of their project against
manufacturer’s claims;
• surveyors contracted to carry out the assessment.
---------------------- Page: 8 ----------------------
TS 62600-100 © IEC:2012(E) – 7 –
MARINE ENERGY –
WAVE, TIDAL AND OTHER WATER CURRENT CONVERTERS –
Part 100: Electricity producing wave energy converters –
Power performance assessment
1 Scope

This part of IEC 62600, which is a Technical Specification, provides a method for assessing

the electrical power production performance of a Wave Energy Converter (WEC), based on

the performance at a testing site.
The scope of this Technical Specification includes:
a) all WECs that produce electrical power from wave energy;
b) all sea resource zones (near and offshore, deep and shallow water);
c) the specification applies to commercial scale WECs that are:
1) compliantly moored,
2) tautly moored,
3) bottom mounted,
4) shore mounted.
The scope of this Technical Specification does not include:

a) WECs that produce other forms of energy unless this energy is converted into electrical

energy;
b) resource assessment;

c) scaled devices in test facilities (tank or scaled sea conditions) where any scaling would

need to be carried out to extrapolate results for a full scale device;
d) power quality issues;
e) environmental issues;
f) power matrix transposition from one location to another.
This Technical Specification provides a systematic method which includes:
– measurement of WEC power output in a range of sea states;
– WEC power matrix development;
– an agreed framework for reporting the results of power and wave measurements.
2 Normative references

The following documents, in whole or in part, are normatively referenced in this document and

are indispensable for its application. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any
amendments) applies.
IEC 60044-1, Instrument transformers – Part 1: Current transformers
---------------------- Page: 9 ----------------------
– 8 – TS 62600-100 © IEC:2012(E)

IEC 60688, Electrical measuring transducers for converting a.c. electrical quantities to

analogue or digital signals
IEC 61000-3 (all parts), Electromagnetic compatibility (EMC) – Part 3: Limits

IEC 61869-3, Instrument transformers – Part 3: Additional requirements for inductive voltage

transformers

ISO/IEC Guide 98-1:2009, Uncertainty of measurement – Part 1: Introduction to the

expression of uncertainty in measurement

ISO/IEC Guide 98-3:2008, Uncertainty of measurement – Part 3: Guide to the expression of

uncertainty in measurement (GUM:1995)
ISO 8601, Data elements and interchange formats – Information interchange –
Representation of dates and times

EquiMar: Protocols for the equitable assessment of marine energy converters, Part II,

Chapters I.A.1 through I.A.5., Editors: David Ingram, George Smith, Claudio Bittencourt

Ferreira, Helen Smith. European Commission 7th framework programme grant agreement

number 213380, First Edition 2011

NDBC:2009, Technical Document 09-02, Handbook of automated data quality control checks

and procedures. National Data Buoy Center, August 2009
3 Symbols and units

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

Table 1 – Symbols and units
Symbol Definition Units
fcell
Frequency of occurrence in the i bin
Total positive sequence line-to-line capacitance of subsea cable farad
cable
Group velocity m/s
f Frequency Hz
Frequency at component i Hz
Energy at f distributed with angle θ
G(θ,f) 1/rad
NOTE
G(θ, f )⋅ dθ= 1
h Water depth m
Spectral estimate of significant wave m
Significant wave height m
Line current
meas
Omnidirectional measured wave energy flux
W/m
Omnidirectional measured wave energy flux per bin
W/m
L Capture length m
Capture length per bin m
---------------------- Page: 10 ----------------------
TS 62600-100 © IEC:2012(E) – 9 –
Symbol Definition Units
M Number of data sets in a bin -
MAEP Mean Annual Energy Production Wh
Frequency n order moments of the variance spectrum -
n Number of sea states -
Number of bins -
P Measured power output W
Measured power output per bin W
Real power W
meas
Power factor -
meas
Reactive power W
meas
Total positive sequence resistance of subsea cable Ω
cable
S Spectral density
S(f) Spectral density as function of frequency
Spectral density at WEC 2
S(f)
WEC
T ( f , t,θ , h,...)⋅ S( f )
Equals WMI
S(f) Spectral density at WMI
WMI
Directional spectrum
S(f, θ)
S( f )⋅ G(θ , f )
Hz⋅ rad
Spectral density at frequency component i
Standard deviation -
t Time lag or shift between the WMI and the WEC s
T Operational hours per record h
Energy period s
Spatial transfer model, for correction of the spectral density measured at the
WMI to the WEC
T(f, t, θ, h,...)
NOTE Not all the variables are listed. The correction depends on the test site.
U Line-to-line voltage V
Line-to-line r.m.s. voltage
meas
V , V
WEC side positive sequence voltage V
p1+ p1–
V , V
Shore side positive voltage V
p2 p2–
Total positive sequence reactance of subsea cable Ω
cable
Frequency spacing Hz
ρ Fluid density
θ Wave direction °
φ Phase angle °
---------------------- Page: 11 ----------------------
– 10 – TS 62600-100 © IEC:2012(E)
4 Sequence of work

Figure 1 shows the sequenced of work for the assessment as described in this technical

specification. The pre-test sections shall be conducted prior to the testing period. Following

the testing period the post-test sections shall be conducted.
Test site characterisation
PRE-TEST
Methodology
TESTING
Measurement and Wave energy
PERIOD
data collection for conversion power
wave data output measurement
Determination of power performance
POST-TEST
Calculation of mean annual energy
Figure 1 – Timeline of assessment
5 Test site characterization
5.1 General

An analysis of the prospective test site shall be undertaken to ensure that it is suitable for

power assessment of a WEC. The incident wave climate shall be evaluated to ensure the

power performance matrix can be populated. In order to infer the incident wave power at the

location of a WEC, the effect of bathymetry and marine currents on the incident wave climate

shall be sufficiently analyzed to determine whether a transfer model between the Wave

Measurement Instrument (WMI) and WEC will be required. If a transfer model is required, the

analysis shall support the development of a suitable transfer model.
5.2 Measurements
5.2.1 Wave measurement for wave power

A WMI shall be deployed at the proposed WEC location prior to WEC deployment. A second

WMI shall be deployed simultaneously at the proposed post-deployment wave measurement

location. The WMIs shall be deployed for a minimum of 3 months prior to WEC deployment

and it is recommended the WMIs record data for 12 months prior to WEC deployment to

account for seasonal variations.

The spectral data shall be calculated from WMI time series data. Estimates of the significant

wave height estimate and energy period shall be calculated from the spectral data. The

following parameters, to be used to determine the power matrix, shall be included in the

determination of the power matrix:
a) spectral shape;
b) directionality of waves;
c) directional frequency spectrum;
d) water depth including tidal effect;
---------------------- Page: 12 ----------------------
TS 62600-100 © IEC:2012(E) – 11 –
e) tidal and marine current, direction and velocity;
f) wind speed and direction;
g) density of water;
h) occurrence and thickness of ice.

Parameters from the above list that have not been recorded, and thus not included in the

development the power matrix, shall be identified and the rationale for their exclusion

justified.
5.2.2 Current measurement

Marine currents at the test site shall be recorded and documented. The current speed and

direction data shall be measured simultaneously with the wave measurement and shall extend

over a minimum of 30 days. The sampling period shall be a maximum of 10 minutes. At least

one current speed and direction record will be taken from the upper half of the water column

during the deployment period. The primary purpose of current records is to facilitate the

development of a marine current model of the area. Tidal and non-tidal currents shall be

estimated and differentiated.

It is recommended, however, to measure current velocity and directions at different points of

the water column in order to adequately describe the velocity profile at the site.

5.2.3 Tidal measurement

Tidal heights shall be recorded at the test site. The measurements shall extend over at least

30 days and shall be analysed to estimate tidal ranges.
5.2.4 Bathymetric survey

The boundary of the test site shall be defined and documented. A bathymetric survey of the

area shall be undertaken and documented. The resolution of the bathymetric survey shall be

as needed to support the wave spatial transfer model, see 5.2.5.
The survey should provide the details on the bottom profile.
5.2.5 Calculation of wave spatial transfer model

The sea state at the location of the WMI shall be representative of the sea state at the

location of the WEC. If the difference between the energy flux at the WMI and the WEC – as

determined by the deployment of a minimum of two WMIs, one at the wave measurement

location and one at the WEC location – is less than 10,0 % for 90,0 % of the records then it

can be assumed that the wave field is statistically equivalent.

NOTE It is expected that this will be the case for a well-chosen deep-water test site.

If the above condition is not met then a spatial transfer model shall be generated and

validated. The spatial transfer model can either be an existing modelling program or a custom

modelling program. The modelling program shall be validated. The accuracy of the model

shall be determined as shown in Annex D.
5.2.6 Modelling of the test site

The spatial transfer model shall predict the spectrum at the WEC based on the spectrum at

the WMI. The test site should be modelled to assist in the development of a spatial transfer

model. The spatial transfer model shall be acceptable if it predicts the energy flux at the WEC

to within 10,0 % of the measured energy flux for 90,0 % of the of the data recorded according

to 5.2.1.
NOTE The spatial transfer model would generally be in the form:
---------------------- Page: 13 ----------------------
– 12 – TS 62600-100 © IEC:2012(E)
(1)
S( f ,θ ) = T( f ,t,θ,h,...)⋅ S( f ,θ )
WEC WMI
6 Methodology
6.1 General

This technical specification governs the methodology for measurement, analysis and

presentation of data to assess the power performance of an electricity generating WEC.

The sea state incident at the WEC shall be measured to the accuracy specified in Clause 7.

The sea
...

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