Solar thermal electric plants - Part 5-2: Systems and components - General requirements and test methods for large-size linear Fresnel collectors

IEC 62862-5-2:2022 specifies the requirements and the test methods for the characterization of a large-size linear Fresnel collector.
This document covers the determination of optical and thermal performance of linear Fresnel collectors, and the tracking accuracy of the collector one-axis tracking system. This test method is for outdoor testing only.
This document applies to linear Fresnel collectors according to Annex A equipped with the manufacturer-supplied sun tracking mechanism.
This document applies to the whole collector field in-situ or as a minimum unit to be tested to an individual collector string (loop) connected to the main piping (flow, return flow) to and from a heat sink, covering the full temperature range of the field.

General Information

Status
Published
Publication Date
09-May-2022
Current Stage
PPUB - Publication issued
Completion Date
10-May-2022
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IEC 62862-5-2:2022 - Solar thermal electric plants - Part 5-2: Systems and components - General requirements and test methods for large-size linear Fresnel collectors
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IEC 62862-5-2
Edition 1.0 2022-05
INTERNATIONAL
STANDARD
colour
inside
Solar thermal electric plants –
Part 5-2: Systems and components – General requirements and test methods for
large-size linear Fresnel collectors
IEC 62862-5-2:2022-05(en)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 62862-5-2
Edition 1.0 2022-05
INTERNATIONAL
STANDARD
colour
inside
Solar thermal electric plants –
Part 5-2: Systems and components – General requirements and test methods for
large-size linear Fresnel collectors
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.160 ISBN 978-2-8322-0096-4

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

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC 62862-5-2:2022 © IEC 2022
CONTENTS

FOREWORD ........................................................................................................................... 5

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

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

3 Terms, definitions and symbols........................................................................................ 7

3.1 Terms and definitions .............................................................................................. 7

3.2 Symbols .................................................................................................................. 8

4 Testing requirements ....................................................................................................... 9

5 Instrumentation ................................................................................................................ 9

5.1 Solar radiation measurement .................................................................................. 9

5.2 Flow rate measurement ........................................................................................... 9

5.3 Temperature measurements ................................................................................... 9

5.4 Wind speed measurement ..................................................................................... 10

5.5 Data acquisition .................................................................................................... 10

5.6 Tracking accuracy measurement ........................................................................... 10

6 Test procedure .............................................................................................................. 10

6.1 General ................................................................................................................. 10

6.2 Collector description ............................................................................................. 10

6.3 Test equipment ..................................................................................................... 10

6.3.1 Performance test ........................................................................................... 10

6.3.2 Optical characterization for performance testing ............................................ 11

6.3.3 Tracking error test ......................................................................................... 12

6.4 Measurement procedure ....................................................................................... 12

6.4.1 General ......................................................................................................... 12

6.4.2 Cleanliness .................................................................................................... 12

6.4.3 Test conditions .............................................................................................. 13

6.5 Calculation and test results evaluation .................................................................. 13

6.5.1 General ......................................................................................................... 13

6.5.2 Useful power ................................................................................................. 14

6.5.3 Incidence angle modifier (IAM) ...................................................................... 15

6.5.4 Evaluation for the quasi-dynamic test method QDT ........................................ 17

6.5.5 Evaluation for the dynamic test method DT .................................................... 18

6.5.6 Validation performance test ........................................................................... 19

6.5.7 Tracking error test (optional) .......................................................................... 20

6.5.8 Uncertainty estimation ................................................................................... 21

7 Reporting format ............................................................................................................ 21

Annex A (informative) Linear Fresnel collector description ................................................... 22

A.1 General description ............................................................................................... 22

A.1.1 Overview ....................................................................................................... 22

A.1.2 Collector row structure ................................................................................... 23

A.1.3 Support structure and foundation ................................................................... 24

A.1.4 Primary reflectors .......................................................................................... 24

A.1.5 Mirror support ................................................................................................ 24

A.1.6 Mirror drives .................................................................................................. 25

A.1.7 Receiver ........................................................................................................ 25

A.1.8 Receiver tube ................................................................................................ 25

A.1.9 Receiver cavity .............................................................................................. 26

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IEC 62862-5-2:2022 © IEC 2022 – 3 –

A.1.10 Receiver support and casing .......................................................................... 27

A.1.11 Tracking system ............................................................................................ 27

A.2 Operation modes .................................................................................................. 28

Annex B (normative) Documentation to be supplied by the collector manufacturer ............... 29

B.1 General configuration of the linear Fresnel collector ............................................. 29

B.1.1 Model and manufacturer ................................................................................ 29

B.1.2 Axes and movements..................................................................................... 29

B.1.3 Collector grouping ......................................................................................... 29

B.2 Geometric characterization of the linear Fresnel collector ..................................... 29

B.3 Mechanical characterization of the linear Fresnel collector .................................... 29

B.4 Optical characterization of the linear Fresnel collector .......................................... 30

B.5 Description of linear Fresnel collector operating modes ........................................ 30

B.5.1 Design operating conditions ........................................................................... 30

B.5.2 Normal operating conditions .......................................................................... 30

B.5.3 Reduced weather/geological operating conditions (features to be
reduced shall be defined (optical, thermal performance) and how much

they are reduced) .......................................................................................... 30

B.5.4 Stow conditions ............................................................................................. 30

B.5.5 Survival conditions ........................................................................................ 30

B.6 Optical and tracking accuracy ............................................................................... 30

B.6.1 Accuracy under normal operating conditions .................................................. 30

B.6.2 Accuracy under reduced operating conditions ................................................ 30

B.7 Linear Fresnel collector component information .................................................... 30

B.7.1 Linear Fresnel collector structure ................................................................... 30

B.7.2 Receiver tube ................................................................................................ 31

B.7.3 Receiver cavity .............................................................................................. 31

B.7.4 Primary and secondary reflectors................................................................... 31

B.7.5 Drive mechanism ........................................................................................... 31

Annex C (normative) Testing report ..................................................................................... 32

C.1 General ................................................................................................................. 32

C.2 Collector characteristics ........................................................................................ 32

C.3 Linear Fresnel collector limitations ........................................................................ 33

C.4 Description of the experimental setup ................................................................... 33

C.5 Results ................................................................................................................. 33

Annex D (informative) Deflectometry mirror testing .............................................................. 35

D.1 Mirror shape quality .............................................................................................. 35

Annex E (informative) Tracking error testing ........................................................................ 36

Bibliography .......................................................................................................................... 37

Figure 1 – Test equipment installation................................................................................... 11

Figure 2 – Sketch of one module of linear Fresnel collector as seen from above ................... 15

Figure 3 – Incidence angles for a linear Fresnel collector ...................................................... 16

Figure 4 – Sketch of parameter identification procedure used for the DT method [3] ............. 18

Figure A.1 – General view of a north-south axis Fresnel collector ......................................... 22

Figure A.2 – General view of an asymmetric east-west axis Fresnel collector ....................... 23

Figure A.3 – Schematic drawing of individual drive a), group drive b) and field drive c)

options .................................................................................................................................. 25

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– 4 – IEC 62862-5-2:2022 © IEC 2022

Figure A.4 – Typical receiver cavity with secondary reflector and glass cover ....................... 26

Figure A.5 – Typical receiver cavity with secondary reflector and without glass cover .......... 27

Figure A.6 – Typical receiver cavity with multiple parallel tubes ............................................ 27

Table C.1 – Alternate tracking accuracy reporting template ................................................... 33

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IEC 62862-5-2:2022 © IEC 2022 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
SOLAR THERMAL ELECTRIC PLANTS –
Part 5-2: Systems and components – General requirements
and test methods for large-size linear Fresnel collectors
FOREWORD

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rights. IEC shall not be held responsible for identifying any or all such patent rights.

IEC 62862-5-2 has been prepared by IEC technical committee 117: Solar thermal electric

plants. It is an International Standard.
The text of this International Standard is based on the following documents:
Draft Report on voting
117/148/CDV 117/160/RVC

Full information on the voting for its approval can be found in the report on voting indicated in

the above table.
The language used for the development of this International Standard is English.
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– 6 – IEC 62862-5-2:2022 © IEC 2022

This document was drafted in accordance with ISO/IEC Directives, Part 2, and developed in

accordance with ISO/IEC Directives, Part 1 and ISO/IEC Directives, IEC Supplement, available

at www.iec.ch/members_experts/refdocs. The main document types developed by IEC are

described in greater detail at www.iec.ch/standardsdev/publications.

A list of all parts in the IEC 62862 series, published under the general title Solar thermal electric

plants, can be found on the IEC website.

The committee has decided that the contents of this document will remain unchanged until the

stability date indicated on the IEC website under webstore.iec.ch in the data related to the

specific document. At this date, the document will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The "colour inside" logo on the cover page of this document 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.

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IEC 62862-5-2:2022 © IEC 2022 – 7 –
SOLAR THERMAL ELECTRIC PLANTS –
Part 5-2: Systems and components – General requirements
and test methods for large-size linear Fresnel collectors
1 Scope

This part of IEC 62862 specifies the requirements and the test methods for the characterization

of a large-size linear Fresnel collector.

This document covers the determination of optical and thermal performance of linear Fresnel

collectors, and the tracking accuracy of the collector one-axis tracking system. This test method

is for outdoor testing only.

This document applies to linear Fresnel collectors according to Annex A equipped with the

manufacturer-supplied sun tracking mechanism.

The testing method in this document does not apply to any collector under operating conditions

where phase-change of the fluid occurs. Although the principles of this document can be applied

also to collectors with phases-change, however, the sensors (enthalpy, flow, temperatures)

required for that are not described in this document.

This document applies to the whole collector field in-situ or as a minimum unit to be tested to

an individual collector string (loop) connected to the main piping (flow, return flow) to and from

a heat sink, covering the full temperature range of the field.
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 TS 62862-1-1, Solar thermal electric plants – Part 1-1: Terminology

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

uncertainty in measurement (GUM:1995)
ISO 9488, Solar energy – Vocabulary
ISO 9806:2017, Solar energy – Solar thermal collectors – Test methods
3 Terms, definitions and symbols
3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO 9488, ISO 9806:2017,

IEC TS 62862-1-1, and the following apply.

ISO and IEC maintain terminological databases for use in standardization at the following

addresses:
---------------------- Page: 9 ----------------------
– 8 – IEC 62862-5-2:2022 © IEC 2022
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.2 Symbols
Gross collector aperture area (projected mirror area on the ground
including the small gaps between facets and positioning of the mirrors
for the sun in the zenith)
Geometric concentration ratio: gross collector aperture area A
divided by the surface area of the receiver Α
Long-wave infrared sky radiation
W/m
Ratio between the optical efficiency of the collector for normal
incidence in a soiled state and a clean state.
Function describing the optical end loss of a collector with finite length
end
when the sun is in the longitudinal collector plane
G Solar irradiance W/m
Height of receiver above mirror plane m
rec
Incidence angle modifier for direct beam irradiation -
Incidence angle modifier for diffuse irradiation -
Incidence angle modifier for direct beam irradiation in the transversal
plane
Incidence angle modifier for direct beam irradiation in the longitudinal
plane
Length of primary mirror row in one collector module m
Length of receiver in one collector module m
rec
Q̇ Thermal power net output of the collector W
Mean fluid temperature K
Ambient temperature K
u Wind speed m/s
Project width of mirror row i on the horizontal m
Collector width (Width of mirror field perpendicular to row orientation in
one collector module)
specular reflectance of the soiled primary mirrors -
test
specular reflectance of the clean primary mirrors -
nom
Longitudinal solar incidence angle °
Transversal incidence angle °
Ratio of specular reflectance of soiled and clean mirror material -
reflector
Collector optical efficiency for direct beam radiation at normal
incidence
Indices
a ambient
b beam
dif diffuse
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IEC 62862-5-2:2022 © IEC 2022 – 9 –
L longitudinal
n normal
T transversal
Tilt tilted
4 Testing requirements

The linear Fresnel collector shall be equipped with all the components supplied by the

manufacturer (such as support structure, primary reflectors, receiver casing and support,

receiver tubes, actuator system and control) and mounted according to the manufacturer

instructions.

The different component/elements (such as the receiver parts, reflectors, mirror drives,

structure) should be previously tested separately by current testing methods or standards when

available. The documentation to be fulfilled by the manufacturer shall be according to Annex B.

5 Instrumentation
5.1 Solar radiation measurement

Solar radiation measurement shall be performed using a pyrheliometer for direct irradiance

according to 21.1 of ISO 9806:2017.

Incidence angles will be determined by calculation or with sun position sensors with accuracy

equal or better than ± 0,1° with a resolution of 0,01°.
5.2 Flow rate measurement
Flow rate measurement shall be performed according to 21.4.1 of ISO 9806:2017.
5.3 Temperature measurements

Temperature measurements (inlet, outlet and ambient temperature) shall be performed

according to ISO 9806:2017 with an accuracy better than 1 % of the temperature rise over the

collector

The collector inlet and outlet positions shall be defined by the manufacturer and pairwise

calibrated temperature sensors shall be installed at no more than 200 mm from this point. If due

to constructional constraints it becomes necessary to position the sensor more than 200 mm

away from the collector, then a test shall be made to verify that the measurement of fluid

temperature is not affected.

The problems caused by the concentrated light on the sensors if the sensors are mounted in

the focus zone shall be taken into consideration.

For piping diameters larger than 254 mm, 2 to 3 temperature sensors should be considered for

each position to have a more representative average.
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– 10 – IEC 62862-5-2:2022 © IEC 2022
5.4 Wind speed measurement

The mean wind speed in the horizontal plane shall be determined with a standard uncertainty

< 0,5 m/s. The sensor shall be installed at (10 ± 0,1) m height from the ground. The sensor

shall be installed within the collector field / solar plant. If there is no wind speed sensor close

enough to the meteorological station of the plant, one temporary sensor should be added at a

distance from the collector extremity (end support as shown in Figure A.1) not larger than 100 m

away.
5.5 Data acquisition
Data acquisition shall be according to 23.5.3 of ISO 9806:2017.
5.6 Tracking accuracy measurement

Experimental tracking accuracy measurements can be obtained using inclinometers. Resolution

of the inclinometers shall be at least 0,01° and accuracy shall be better than 0,1° over the whole

range of tracking angles. Combination of two or more inclinometers often solves this

requirement.

The true tracking angle is measured at two locations of the collector, one near the centre (where

the drive system is usually located) another one at one collector end.
A more detailed tracking error testing is optional (see 6.3.3).
6 Test procedure
6.1 General

Performance testing includes at least the assessment of the heat power delivered by the

collector under various operating and environmental conditions and the measurement of the

dependence of the thermal performance on the incidence angle of the irradiation onto the

collector. These two sets of parameters are required for the calculation of the collector heat

output. If possible, an effective thermal capacity according to ISO 9806:2017 should be also

determined. A minimum collector unit (Figure 1) as already stated in the scope may be a

complete collector row, a loop or even a subfield, covering the whole temperature range of

operation.
6.2 Collector description

The description of collector(s) should be supplied by the manufacturer according to Annex B.

All the components of the tested collector (reflectors, receiver, structure, etc.) shall be

representative of the product. The components shall have been selected randomly from the

production during the erection of the collector.

All the serial numbers and identification of those components should be reported in the testing

report.
6.3 Test equipment
6.3.1 Performance test

The sensors shall be mounted according to ISO 9806:2017. A scheme of principle for the test

installation is presented in Figure 1.
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IEC 62862-5-2:2022 © IEC 2022 – 11 –
Key
1 pump 6 temperature sensor (T )
out
2 flow meter 7 ambient temperature sensor (T )
3 temperature sensor 8 direct solar irradiance sensor
4 temperature sensor (T ) 9 anemometer
5 linear Fresnel collector unit
Figure 1 – Test equipment installation

During the tests of a linear Fresnel collector it will be necessary to guarantee that the reflectors

and glass envelopes of the receivers are kept clean. For testing purposes, the cleanliness factor

is defined as the ratio between the average optical efficiency during the test and the optical

efficiency with ideal clean surfaces. Depending on the receiver construction, not only the

cleanliness of the primary mirrors, but to a lesser degree also soiling of the tubular or plane

glass cover, and the secondary reflector may impact the collector cleanliness. The target is to

...

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