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GUIDE TO STANDARD
ISO 9806:2017
A Resource for Manufacturers, Testing
Laboratories, Certification Bodies and
Regulatory Agencies
Version 1.0
26th October 2017
Guide to the standard ISO 9806:2017
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Guide to the standard ISO 9806:2017
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1 Purpose and Scope ........................................................................................................................................... 4
2 Normative References ....................................................................................................................................... 6
3 Certification (Solar Keymark, IAPMO and SRCC) ............................................................................................... 8
4 Solar Collector Types ...................................................................................................................................... 10
5.1 Test Overview .............................................................................................................................................. 12
5.2 Testing of Collectors with Specific Attributes ............................................................................................... 14
6 Internal Pressure Test (liquid heating collectors only) ....................................................................................... 16
7 Leakage Rate Test (closed loop operation only) ............................................................................................... 18
8 Rupture and Collapse Test (solar air heating collectors only) ........................................................................... 20
9 Standard Stagnation Temperature .................................................................................................................. 22
10 Exposure and Half-Exposure Test .................................................................................................................. 24
11 External Thermal Shock Test ......................................................................................................................... 26
12 Internal Thermal Shock Test (liquid heating collectors only) ........................................................................... 28
13 Rain Penetration Test .................................................................................................................................... 30
14 Freeze Resistance Test .................................................................................................................................. 32
15 Mechanical Load Test ................................................................................................................................... 34
16 Impact Resistance Test .................................................................................................................................. 36
17 Final Inspection ............................................................................................................................................. 38
18 Test Report ................................................................................................................................................... 40
19.1 Thermal Performance Testing .................................................................................................................... 42
19.2 Solar Irradiance Simulator .......................................................................................................................... 44
20 Collector Mounting and Location ................................................................................................................. 46
21 Instrumentation ............................................................................................................................................ 48
22 Test Installation............................................................................................................................................. 50
23 Performance Test Procedures ........................................................................................................................ 52
24.1 Computation of Parameters (liquid heating collectors) ............................................................................... 54
24.2 Computation of Parameters (air heating collectors) .................................................................................... 56
25 Effective Thermal Capacity and Time Constant ............................................................................................. 58
26 Determination of the Incident Angle Modifier ............................................................................................... 60
27 Determination of Pressure Drop .................................................................................................................... 62
Register
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The purpose of this guide is to provide guidance about the application and use of the ISO 9806:2017 standard,
concerning the testing of solar thermal collectors. It is intended to support the interpretation and application of the
standard. The guide has been developed with three different target groups and objectives in mind.
1. A guide directed to established and new test laboratories for collector testing. The main purpose here is
to give a quick introduction to the standard for new laboratories and in general to contribute to a uniform
interpretation of the standard and presentation of results.
2. A guide directed to manufacturers and importers of collectors. Here, the purpose is to give a very light
introduction to the standard and to explain how it is used for type testing as well as for innovation and
development support.
3. A guide directed to certification bodies. The intention here is to provide access to easy evaluation of the
presented results.
How to use the present guide ?
The present guide is divided into single Fact-Sheets, usually one per chapter of ISO 9806:2017.
Fact Sheet 1
gives very general information about the guide and the single fact sheets as well as the target group description.
Fact Sheet 2
gives very general information about the normative reference.
Fact Sheet 3
gives information about certification issues in alignment with ISO 9806:2017.
Fact Sheet 4
describes the different solar thermal collector types.
Fact Sheet 5.1
gives a schedule for the test sequence.
Fact Sheet 5.2
gives information for testing collectors with specific attributes.
Fact Sheets 6 to 27
are the most important. Each of these Fact-Sheet concisely gives:
- an introduction to the test procedure in the form of a flow chart (where possible);
- an information box about the main boundary conditions for testing without repeating all conditions from ISO
9806:2017;
- some “Tips and Tricks” about testing, mainly addressed to new and established testing laboratories;
- a “Manufacturers Information Box”, giving a very light introduction to the standard and to explain how it is
used for type testing as well as for innovation and development support;
- the “Exemplary Results” on one hand represents typical results for standard collectors and on the other hand
provides an idea for presentation of the results in the report.
1 Purpose and Scope
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The following standards are referred to in the text of ISO 9806:2017 in such a way that some or all of their content
constitutes requirement of this standard. For dated references only the edition cited applies. For undated references,
the latest edition of the referenced document (including any amendments) applies.
ISO 9060, Solar energy – Specification and classification of instruments for measuring hemispherical solar and direct
solar radiation
ISO 9488, Solar energy - Vocabulary
A Rough Comparison with other Solar Thermal Collector Standards
Beside ISO 9806:2017 there are a couple of other established testing standards. The following table shows a rough
comparison regarding the scope as well as the necessary tests and measurements of different collector test
standards.
Table 1: Comparison of scope, thermal performance and tests required by different standards.
Standard
EN 12975-1:2006
ISO 9806:2017
CSA F 378.1,2,
2011
Scope
SLHC (Solar Liquid Heating Collectors)
SAHC (Solar Air Heating Collectors)
×
WISC (Wind and Irradiance Sensitive Collectors)1
×
×
ICS (Integrated Collector Storage)
×
×
×
CSC (Concentrating Solar Collector)1
×
×
PV-T (Photovoltaic Thermal Collector)1
×
×
Thermal Performance
Efficiency measurement on SLHC
Efficiency measurement on SAHC
×
Determination of the thermal capacity
×
Determination of the leakage flow rate2
×
×
Collector time constant
×
Durability and Reliability Tests
Internal Pressure Test
Rupture and Collapse Test2
×
Exposure Test
External Thermal Shock Test
Internal Thermal Shock Test
×
Rain Penetration Test
×
Mechanical Load Test
Determination of the Stagnation Temperature
×
Determination of the max. Start Temperature2
×
×
Determination of Pressure Drop
×
Impact Resistance Test
×
×
Freeze Resistance Test
×
Final Inspection
1Could be SLHC or SAHC
2 Only for SAHC
2 Normative References
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This Fact Sheet gives a slight overview on the basic operation of
certification. As an example, a rough comparison between the testing
requirements for solar Keymark, IAPMO and SRCC is used.
Involved Parties and their Responsibility with the Example of Solar Keymark Certification
Certification Procedure with the Example of Solar Keymark Certification
The flow chart shows the
general certification process of
Solar Keymark Certification. Due
to legal requirements, a Solar
Keymark Certificate can only be
issued on the basis of tests
according to a European
standard. For this reason, the
European collector test standard
EN 12975 is mentioned within
this chart. Nevertheless the tests
and measurements must be
performed according to ISO
9806, which defines the testing
requirements and is the
reference in EN 12975.
3 Certification (Solar Keymark, IAPMO and SRCC)
Figure 4: Solar Keymark certification procedure (Source: Solar Heat Europe)
Figure 3: Certification flowchart with all parties involved (Source: Solar Heat Europe)
Figure 1: Solar Keymark, IAPMO and SRCC
Figure 2: Involved parties
(©Fraunhofer ISE)
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A Rough Comparison of Different Schemes
Solar Keymark certificates are issued by different empowered certification bodies (CBs), while in the US both the
Solar Rating and Certification Corporation (SRCC) and the International Association of Plumbing and Mechanical
Officials (IAPMO) provide certification to a number of solar-related standards, including SRCC Standard 100, which is
based largely on ISO 9806. In all cases tests and measurements are performed by accepted laboratories, which send
the test results to the CB. Laboratories must be accredited in accordance with ISO/IEC 17025 (General requirements
for the competence of testing and calibration laboratories), including accreditation to perform tests according to ISO
9806:2017. CBs must be accredited in accordance with ISO/IEC 17065 (Requirements for bodies certifying products,
processes and services), and inspection bodies must be accredited in accordance with ISO 17020 (Requirements for
the operation of various types of bodies performing inspection).
Solar Keymark requires that testing laboratories be recognized by one or more CB, while in the US recognition by
other CBs is not a requirement. CBs may impose additional requirements on testing laboratories, such as surveillan ce
of the quality system and the test equipment. The following chart shows a comparison of the specific tests required,
scope and certification schemes for Solar Keymark, IAPMO and SRCC.
Table 1: Comparison of certification requirements
Scope
SLHC (Solar Liquid Heating Collectors)
SAHC (Solar Air Heating Collectors)
WISC (Wind and Infrared Sensitive Collector)
CSC (Concentrating Solar Collector)
PVT (Photovoltaic Thermal Solar Collector)
Thermal Performance
SLHC performance measurement
SAHC performance measurement
Effective thermal capacity
Leakage rate
Time constant
Durability, Reliability and Safety
Internal Pressure Test
Rupture and Collapse Test
Exposure Test
External Thermal Shock Test
Internal Thermal Shock Test
Rain Penetration Test
Mechanical Load Test
Standard Stagnation Temperature
Maximum Start Temperature
Pressure Drop
Impact Resistance
Freeze Resistance
Final Inspection
Certification Requirements (surplus)
Factory Inspection
Remote Sampling
SKM
×
×
×
×
×
SRCC
×
×
×
×
×
×
×
IAPMO
×
×
×
×
×
×
×
Global Solar Certification Network (GSCN)
Figure 5: Global Solar Certification Network (GSCN), source GSCN
“The aim of “Global Solar Certification Network” (GSCN) is to facilitate cross-border trading for manufacturers and
other suppliers of solar thermal products; its objective is to minimize the need for re-testing and re-certification in
every new country where products are to be marketed and sold. The concept of “Global Solar Certification” is being
implemented for solar thermal collectors and is based on the test procedures given by ISO 9806:2017.
The “Global Solar Certification Network” is cooperation between solar certification bodies/schemes around the
world. When a product has been certified by one of the participating certification bodies/schemes, the product can
obtain certification from other participating certification schemes without re-testing of the product and without re-
inspection of production facilities. (Source: http://www.gscn.solar)
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The ISO 9806:2017 standard covers performance, durability and reliability testing of almost all collector types
available in the market. The standard is applicable to liquid heating collectors, air heating collectors, hybrid solar
collectors co-generating heat and electric power, as well as to solar collectors using external power sources for
normal operation and/or safety purposes (e.g. tracking concentrating collectors). Within the following table the most
common types of solar collectors are described, including their characteristics and their typical field of applications.
Collector Types
Collector type
Characteristics
Typical applications
WISC liquid heating
collectors
(Picture source: RISE)
- High performance at low
temperatures and highly
dependent on wind speed and
thermal irradiance;
- Can often withstand freezing;
- Sometimes designed for working
under dew-point of ambient air
(heat pumps).
- Swimming pools
- Evaporators for heat pumps
Flat plate collector
(Picture source: QAiST -
IEE/08/593/SI2.529236)
Good performance at higher
temperatures (typical temperatures
for domestic hot water)
- Domestic hot water systems
- Combi- systems
- District heating
Vacuum tube collector
(Picture source: RISE)
Good performance at higher
temperatures (typical temperatures
for domestic hot water and above)
- Domestic hot water and
Combi-systems
- District heating
- Solar assisted cooling
- Process heat
Stationary
concentrating collector
(Picture source: RISE)
Good performance at high
temperatures
- Domestic hot water and
Combi-systems
- District heating
- Solar assisted cooling
- Process heat
4 Solar Collector Types
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Collector with external
power source
(Picture source: QAiST -
IEE/08/593/SI2.529236)
Can be of Linear-Fresnel, parabolic
trough or dish type
- Solar assisted cooling
- Process heat
- Power plants
Air-collectors (incl.
WISC)
(Picture source: QAiST -
IEE/08/593/SI2.529236)
Can be of closed or open loop type,
WISC or non-WISC
- Drying of crops
- Pre-heating of air for building
ventilation
Hybrids (incl. WISC)
(Picture source: QAiST -
IEE/08/593/SI2.529236)
Broad variation of subtypes:
- WISC/non-WISC
- Liquid/Air heating
- Concentrating/non-
concentrating
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During the collectors’ lifetime some severe climatic and working conditions will be met. It is required that the
collectors do not suffer major failures under these conditions. The reliability and durability tests were designed to
reproduce the most probable extreme conditions that a collector would be subjected to. For each test, the standard
describes in a very simple way the conditions that are intended to be simulated.
Table 1 clarifies the test list taken from ISO 9806:2017 summarizing all tests covered in the standard along with the
preconditions or comments related to each test.
Table 1: Test list based on ISO 9806:2017
SLHC
SAHC CL
SAHC OTA
Polymerics
Clause
Test
–
–
Clause 7
Air Leakage Rate Determination
–
Clause 8
Rupture and Collapse Test
Clause 9
Standard Stagnation Temperature Determination
Clause 10
Exposure Test
1
1
1
1
Clause 11
External Thermal Shock Test
–
–
Clause 12
Internal Thermal Shock Test
Clause 13
Rain Penetration Test
2
–
–
2
Clause 14
Freeze Resistance Test
–
–
Clause 6
Internal Pressure Test for Fluid Channels
()
()
()
()
Clause 15
Mechanical Load Test
()
()
()
()
Clause 16
Impact Resistance Test
Clause 17
Final Inspection
Clause 19 - 26
Thermal Performance Test
Clause 27
Pressure Drop Measurement
mandatory, 1 only for collectors without toughened glass, 2 only for collectors claimed to be freeze resistant
and collectors containing heatpipe, () mandatory but the manufacturer can define the maximum load to be zero,
– not mandatory or not possible, mandatory and under SSC (Standard Stagnation Conditions; clause 9).
SLHC
Solar Liquid Heating Collector
SAHC CL
Solar Air Heating Collector with Closed Loop operation
SAHC OTA
Solar Air Heating Collector with Open To Ambient operation
Polymerics
collectors in which organic materials are used for fluid channels thereby being exposed to high
temperatures and pressures respectively
5.1 Test Overview
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The ISO 9806:2017 covers the most current standard products. Some of those collector technologies require special
considerations in testing which are described here.
Test Procedure
Boundary Conditions
Due to special collector attributes the test procedures
for functional as well as efficiency testing might be
customized in accordance to the certain attribute.
Collectors may have one or several attributes.
Attributes not mentioned in the test report shall not be
considered as applicable for the tested collector.
Collector Types with Specific Attributes
Specific
Attribute
Explanation
Examples
External power
sources
Collector types that need an external power source for normal
operation.
SAHC with integrated
fans, tracking and
concentrating collectors
Active or passive
measures for
normal operation
and self-
protection
In order to prevent damages caused by operating conditions like
stagnation, pump-malfunction and others, some collector
technologies are equipped with active and/or passive protection
devices. Examples for active protection devices are:
- UPS-Systems, ensuring that power interrupts do not negatively
influence normal operation of the product.
- MSR-Technology to avoid damages caused by system
malfunctions, sudden changes of surrounding conditions, etc.
Tracking and
concentrating collectors
Co-generating
thermal and
electrical power
Collectors producing thermal energy and electricity
simultaneously.
PV-T Collectors
Wind and/or
infrared sensitive
collectors (WISC)
Wind sensitive means that the surrounding wind velocities
significantly influence the thermal behavior (convective losses) of
the collector. This is always given if the heat conducting
components of a collector are directly exposed to the surrounding
air.
Infrared sensitive means that the collectors efficiency is
significantly influenced by infrared irradiation. This is always given
if there is no transparent cover in between the absorber and the
radiation source/sink or if the transparent cover is in direct contact
with the absorber.
SAHC where the heat
transfer fluid is in direct
contact with the
transparent cover.
Formerly those collectors
were often called “Non-
covered collectors” like
swimming pool heaters,
PV-T Collectors,
Transpired SAHC’s.
Façade collectors
Collectors that, according to the manufacturer’s specifications, can
be operational at inclination angles above 75° shall be considered
as façade collectors.
Those products are often
highly integrated in the
function of a buildings
envelope. Testing has to
be customized.
Air and liquid
heating
Collectors which are constructed to operate with liquid heat
transfer fluids as well as air as heat transfer fluid.
This combination often
appears in the context of
solar thermal combined
with heat pump
technology.
5.2 Testing of Collectors with Specific Attributes
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Special Testing Considerations for:
Collectors using external power sources and/or active or passive measures for normal operation and self protection:
- If the collector which is using external power sources and/or active or passive for normal operation and self-
protection is installed at the testing side of the testing laboratory, it is recommended that the manufacturer
is present during the installation to avoid installation errors, errors in commissioning, and errors in system-
settings;
- External parts of collectors like cabinets, sensors, etc. shall be weatherproof. Components which are an
integral part of the collector (e.g. actuators, motors, cabinets, etc.) for which water penetration can be
expected shall be a part of the rain penetration test;
- The function of a USP-System (undisturbed power supply) can easily be checked by interruption of main
power supply.
Tracking and concentrating collectors CSC
- To be tested using the supplier’s tracking system;
- Specific aspects related to durability testing, e.g. active protection;
- The procedure for the determination of the incident angle modifier as given within ISO 9806:2017 might
not be applicable in case of unsymmetrical collector constructions without further adaptions;
- In-Situ testing might be necessary in case of large concentrating collectors;
- Testing shall be close to real operation conditions (e.g. pressure, temperature).
Collectors co-generating heat and electrical power PV-T
- All thermal performance tests shall be made under maximum electrical power point conditions (MPP-Mode);
- For all durability tests, the electrical power shall not be connected to any load (open circuit) to prevent
cooling and to simulate worst case operating conditions;
- Electrical safety is not included in the test procedure of ISO 9806:2017.
Wind and Infrared Sensitive Solar Collector WISC
- Long wave irradiance and wind speed are important variables during performance testing and special
considerations for measurements apply;
- Condensation effects on the performance are not accounted in the thermal performance test method.
Evacuated Tubular Solar Collector ETC
- Bi-axial incidence angle modifier (IAM) measurement required;
- Heat pipes and heat conduction paste, if present, need special attention;
- Heat pipe collectors must undergo a half exposure test before efficiency testing is started.
Façade collectors
- 50% of the initial outdoor exposure shall be made with the collector vertically installed.
Solar Air Heating Collectors SAHC
- The procedure for the determination of the incident angle modifier as given within ISO 9806:2017 might
not be applicable. Mostly IAM is determined by an estimation on the basis of the collector design;
- The inflow conditions can significantly influence the collector efficiency.
On-Side build collectors, customized collector
- In-situ or in-field testing maybe reasonable for collectors that are design for a specific costumer.
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The objective of the test is to determine if the absorber can withstand pressures which might occur during normal
operation. The apparatus and procedures for an internal pressure test are strongly dependent on the type of
material that the absorber is comprised of.
Test Procedure
Figure 1: Internal pressure test of a polymeric collector at the indoor
solar simulator of the TestLab Solar Thermal Systems, Fraunhofer ISE.
Boundary Conditions
Table 1: Differences between pressure tests for Polymeric and Non-
Polymeric absorbers
Non-Polymeric
fluid channels
Polymeric fluid
channels
Duration
> 15 min
> 60 min
Temperature
20 ± 15°C
Maximum
operating
temperature or
stagnation
temperature
Pressure
source
Hydraulic or pneumatic
Pressure
1.5 × maximum operating pressure
Pre-
conditioning
-
Half-exposure is
required before
start of the test
Requirement
5 % or 17 kPa
(whichever is
greater)
Droplets or loss
of air
Manufacturer´s
definition Maximum operating
pressure
Mounting:
- place the collector in suitable conditions
- install pressure gauge and air bleed valve
Polymeric fluid
channels? yes
yes
no
Δp > 5 % or
Δp > 17 kPa
Test at 20 °C ± 15 °C
no
Drain back
system?
Test at
Tmax or Tstag
Test at
Tmax
Hold the pressure
for 15 minutes
Hold the pressure for
1 hour
Droplets or
loss of air?
Qualified
no no
Repeat the test
once
yes
6 Internal Pressure Test (liquid heating collectors only)
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"Tips and Tricks"
- Note that “absorber” includes both the absorber plate as well as the fluid containing tubes;
- This test is only applicable for liquid heating collectors;
- This test is the last test of the test sequence before final inspection;
- Pay attention to avoid overpressure during pressurizing the collector;
- Be aware that there is a significant safety risk if the collector does not pass;
- The collector must be completely filled with fluid. Use an air bleed valve to ensure that no air remains;
- For fluid channels made of polymeric materials, one of the following methods can be used:
Table 2: Summary of the heating procedures for internal pressure tests using hydraulic pressure source.
Stagnation
temperature/Test
temperature
Pressure
source
Fluid
used
Heating procedure
Precautions during test
< 90°C
Hydraulic
Water
Submerge the absorber in a
heated water bath.
For safety reasons, the collector shall
be encased in a transparent box to
protect personnel in the event of
explosive failure during this test.
> 90°C
Hydraulic
Oil
Connect the collector to a
hot oil circuit.
Take safety measures to protect
personnel from hot oil in the event
of explosive failure during test.
Connect the collector to an
oil circuit / heat the collector
using a solar simulator.
Connect the collector to an
oil circuit / heat the collector
using natural solar
irradiance.
> 90°C
Pneumatic
Air
Heat the collector using a
solar simulator.
For safety reasons, the collector shall
be encased in a transparent box to
protect personnel in the event of
explosive failure during this test.
Heat the collector using
natural solar irradiance.
Manufacturers Information Box
- The manufacturer shall define the maximum operating pressure;
- Preliminary In-house-testing is recommended to check whether the collector withstands those requirements
(especially in case of polymeric fluid channels).
Exemplary Results
- Absorber leakage or such deformation that forms permanent contact between absorber and cover;
- As deformation of fluid channels cannot be recognized until the collector has been opened, it is strongly
recommended to check the fluid channels during the final inspection.
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The objective of the test is to quantify the volumetric leakage flow rate of solar air heating collectors with
dependence on the operation pressure.
Test Procedure
Figure 1: Test setup including a fan, a volumetric flow meter and an
electrical pressure gauge at TestLab Solar Thermal Systems,
Fraunhofer ISE.
Boundary Conditions
For collectors with polymeric materials in direct contact
with the working fluid, it is necessary to determine the
leakage rate under stagnation conditions.
(see chapter 9)
For all other collector designs, it is recommended to
determine the leakage rate at ambient temperature
and without irradiance.
Note: There is no range defined for measuring the
leakage rate. It is recommended to set the range limits
for maximum positive and maximum negative pressure
at 1.5 times the maximum operating pressure specified
by the manufacturer.
"Tips and Tricks"
- Preliminary quantified leakage rates resulting from testing facility itself shall be subtracted from the collector test
results;
- Realizing at least four positive and four negative pressure values to identify the correct curve, often it can be
fitted with a 3rd order function;
- Hold each pressure level for at least 10 minutes.
Manufacturer´s
definition
Mounting:
- seal outlet
- connect fan, volumetric flow meter at inlet
END
Measure:
- pressure in collector circuit
- inlet temperature in collector circuit
- volumetric flow rate
Measure under
standard
stagnation
conditions
Start measuring from ambient
pressure up to the maximum pressure
(positive and negative)
Polymeric
material?
Measure under
ambient conditions
yesno
Maximum operating
pressure
7 Leakage Rate Test (closed loop operation only)
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Manufacturers Information Box
- For collectors with polymeric materials in direct contact with the working fluid, the test will be conducted under
standard stagnation conditions (see Fact Sheet 9);
- The higher the leakage rate, the lower the power output of the collector;
- The leakage rate should be reduced as far as possible.
Exemplary Results
Figure 2: Typical Leakage rate curve fitted with a 3rd order polynomial on the basis of flow measurement points for positive and negative
pressures.
-16
-12
-8
-4
0
4
8
12
16
-320 -240 -160 -80 0 80 160 240 320
Leakage rate [m3/h]
Pressure [Pa]
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The objective of the test is to assess the ability of SAHC to withstand the pressure levels expected in the air duct
system with which the collector is incorporated. This test is analogous to the internal pressure test for liquid heating
collectors.
Test Procedure
Figure 1: Test setup including a fan, a volumetric flow meter and an
electrical pressure gauge at TestLab Solar Thermal Systems,
Fraunhofer ISE.
Boundary Conditions
There are different test methods for open to ambient
and closed loop collectors as well as for collectors with
polymeric materials.
Closed loop Operation:
- Pressure of 1.5 times the maximum (positive or
negative) collector operating pressure as specified
by the manufacturer
- Maintain this pressure for 10 minutes
- At ambient temperature
Open to ambient Operation:
- Raise air supply to 1.5 times the maximum flow
rate specified by the manufacturer in less than 15
seconds
- To be tested in normal use configuration
- Maintain air flow rate for at least 10 minutes
Collectors with polymeric materials in direct contact
with the working fluid:
- Shall be tested at maximum operation temperature
by using a heater, a solar irradiance simulator or
outdoors under natural solar irradiance
END
Measure:
- pressure in collector circuit
- temperature in collector circuit
- volume flow rate
OTA
Start measuring up to 1.5
times the maximum volumetric
flow rate
(positive and negative)
Polymeric fluid
channels?
Manufacturer‘s
definition
Report any rupture or collapse
and the related pressure
Operation
mode Open to ambient
(OTA)
Maximum volumetric
flow rate
Closed loop
(CL)
Maximum operating
pressure
Mounting:
- seal outlet
- connect fan
- volumetric flow meter
on inlet
Mounting:
- connect fan
- volumetric flow meter
on outlet
Measure under
standard
stagnation
conditions
yes
CL
Start measuring from ambient
pressure up to 1.5 times the
maximum operating pressure
(positive and negative)
Measure under
ambient
conditions
no
8 Rupture and Collapse Test (solar air heating collectors only)
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"Tips and Tricks"
- Caution: Protect personnel in the event of rupture failure.
- In case of polymeric materials, which are in direct contact to the hot heat transfer fluid, the test at maximum
operating temperature is required by chapter 8 of ISO 9806:2017 for testing. Deviating from this standard
stagnation conditions are required by chapter 9 of ISO 9806:2017. Therefore it is recommended to perform the
test under from stagnation temperature;
- In case of open to ambient collectors with polymeric materials in direct contact with the working fluid, the
maximum operating temperature is reduced because of testing with 1.5 times the maximum flow rate, if no
artificial heater is used;
- For closed loop SAHC’s the test setup can be identical to that of the leakage rate test (see Fact Sheet 7) or to
the test setup of the performance test (see Fact Sheet 19);
- With proper planning, this test could be performed consecutive to the leakage rate test to reduce the mounting
effort;
- Make sure that the connection from the air ducts to the collector is tight and fastened.
Manufacturers Information Box
- Closed loop collectors are tested with 1.5 times the maximum operating pressure (positive and negative)
specified by the manufacturer;
- Open to ambient collectors are tested with 1.5 times the maximum mass flowrate specified by the
manufacturer;
- Collectors with polymeric materials in direct contact with the working fluid are tested at elevated temperatures;
- In-house testing is recommended.
Exemplary Results
On the collector:
- Distortion, deformation, loss of bonding, leakages
The following test results will be deemed as major failures:
- Unintended contact between absorber and transparent cover
- Collapsing of structure
- Permanent displacement of (internal) collector components
- Structural damage
- Permanent deformation
Major failures shall be reported with photos in the test report.
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The purpose of this test is to determine the collectors´ maximum temperature with no heat removal under high solar
radiation and high ambient temperature. This temperature is used for the right choice of insulation and piping
material.
Test Procedure
Figure 1: Test setup at TestLab Solar Thermal Systems, Fraunhofer
ISE.
Boundary Conditions
Standard Stagnation Conditions (SSC) are defined as:
Irradiation: 1000 W/m² ± 100 W/m²
Ambient temperature: 30 °C ± 10 °C
Surrounding air speed: < 1 m/s
The standard stagnation temperature is furthermore
needed for the following tests:
- Internal pressure test, for collectors with polymeric
parts in direct contact with the working fluid
- Air leakage rate test, for air heating collectors with
polymeric parts in direct contact with the working
fluid
- Rapture or collapse test, for air heating collectors
with polymeric materials
- Exposure test
"Tips and Tricks"
Sensor installation:
- The installation of the temperature sensor (position and connection to the absorber) has a significant influence
on the measured temperature and affects the stagnation temperature. There are solutions for taping, clamping
or riveting.
- For flat plate collectors, the “hottest point” can be estimated as farthest away from all the edges. If the tilting
angle at the exposure is significant, the hottest point is in the upper third rather than in the middle.
- For Heat pipe collectors, often a single tube is exposed with the temperature sensor on the condenser in a very
Manufacturer´s
definition
By measurement and
extrapolation
By using efficiency
parameters
Determination of the
Standard Stagnation
Temperature
Mount the collector for
worst case condition and
attach a temperature sensor
Use Equation (1) of the
standard
Standard Stagnation
Temperature
Performance measurement
is needed in advance
Use Equation (2) of the
standard
Determine the efficiency
parameters
Measure stagnation
temperature after 1.5 h
under standard stagnation
conditions
Stagnation temperature
on the type plate
9 Standard Stagnation Temperature
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well isolated and rain protected mounting.
Method1:
- This approximation is acceptable only if the irradiance level (Gm) used during testing is within 10% of the
irradiance specified for the stagnation conditions (Gs).
Method 2:
- To have a good approximation the thermal performance test shall include test data with T*m approaching
T*m, stagnation. If all efficiency data have values of T*m less than half of T*m, stagnation, method 1 above shall be used.
- Measurements of performance data is done at a much higher wind speed than in stagnation conditions which is
compensated by a factor of 1.2 in equation 2 of ISO 9806:2017.
Manufacturers Information Box
This test provides information on the design temperature for all materials used in the collector. Manufacturers
should pay attention to the standard stagnation temperature value when designing the collector or choosing
materials, recommending insulation materials downstream, and selecting the heat transfer fluid.
In-house testing is recommended to check whether the collector withstands those requirements.
Exemplary Results
The following chart shows exemplary temperature ranges of reachable standard stagnation temperatures depending
on the collector technology.
Figure 2: Attainable range of standard stagnation temperatures for different collector technologies. (Source: Fraunhofer ISE)
*Stagnation is avoided by defocusing for CSP because temperatures can be too high
0
100
200
300
400
500
600
700
WISC PV-T WISC SAHC WISC SLHC FPC VTC (Heat
Pipe)
VTC (Direkt
Flow)
CSP (e.g.
Fresnell)*
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Exposure and half-exposure are short term ageing tests with the objective to give an indication of the ageing effects
which are likely to occur during a longer period of natural ageing. Particularly adverse situations including cycles of
high and low temperature, high and low irradiance (between solar noon and night) and humidity variation are taken
into account.
Test Procedure
Figure 1: Outdoor exposure at the testing facility of Fraunhofer ISE
Boundary Conditions
The collector shall be exposed until the minimum
irradiation H and the minimum hours at certain
irradiation and temperature levels as defined in Table 2
of ISO 9806:2017 are reached. This can be done by
either a single initial outdoor exposure or the
combination of the initial outdoor exposure with one
of the following three additional methods.
Choosing method 1 means to finalize the exposure test
outdoors under same conditions as the initial outdoor
exposure.
Choosing method 2 requires that a heat transfer
medium is pumped through the collector at the
highest possible mass flow rate. The temperature of
the heat transfer medium shall be 10°C higher than
the standard stagnation temperature.
Choosing method 3 means to fulfil the requirements
given in Table 2 of ISO 9806:2017 by using a solar
simulator.
Particular boundary conditions for all of these methods
are given in chapter 10 of ISO 9806:2017.
"Tips and Tricks"
- It is absolutely important to check the collectors’ appearance at least once a week. It is further recommended to
document this check by photographs;
- The test duration can significantly be shortened by the usage of tracking devices;
- Method 2 (pumped heat transfer loop) leads obviously not to an equal aging process of the whole collector as
no degradation caused by UV-Radiation occurs.
Manufacturer´s
definition Climate Class
Mount the collector outdoor
Initial outdoor exposure:
- 30 days under any climatic condition
- 15 days for half exposure
Weekly visual inspection
- report any signs of damage
Method 1:
Outdoor and
indoor
exposure
Method 2:
Pumped heat
transfer loop
Method 3:
Indoor
exposure under
SSC
Method
selection
Achieve the values for selected climate class
10 Exposure and Half-Exposure Test
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Manufacturers Information Box
The standard now offers the opportunity for the manufacturers to choose the climate reference class for the
exposure test (also valid for external and internal thermal shock tests).
The reference conditions given in Table 1 of ISO 9806:2017 are correlated to the annual global horizontal irradiation
values as given within the following table and figure. Threshold values for the different classes were defined based
on the irradiation map. Values for an actual location can be taken from this map or other similar sources.
Table 1: Annual Global Horizontal Irradiation values for different climate classes
Property
C
B
A
A+
Annual Irradiation (H) [kWh/m2]
H≤1000
1000<H≤1600
1600<H≤2000
H>2000
Figure 2: Yearly sum of Global Horizontal Irradiation (GHI); ; Source Metenorm 7.0 (www.meteonorm.com); uncertainty 8%; Period 1986 – 2004;
grid cell size: 0.25°
Test Evaluation and Typical Failures
The evaluation of the exposure test and classifying of potential problems as minor problem or major failure shall be
done based on visual observation of the collector at the end of the test. A ‘major failure’ can be defined as a
problem that may have a strong impact either on the thermal performance of the collector or on the durability of
the collector. This classification is dependent on the judgment of the test laboratory. Table 1 gives guidance on the
criterion for classification of major failure after the exposure test.
Table 2: Recommendations for classification of a potential problem as major failure after exposure test
Collector component/s
Potential problem
Evaluation
Consider as major failure if:
Collector box/fasteners
Cracking
Large areas are affected resulting in future rain
penetration problems
Warping
Corrosion
Rain penetration
If exceeding the limits of rain penetration test
Seals/gaskets
Cracking
Large areas are (potentially) affected resulting in future
rain penetration problem; also smaller failures that can
be expected to progress during longer exposure
Adhesion
Elasticity
Cover/reflector
Cracking
Areas affected will result in decrease of thermal
performance.
Fast increase of the problem during the test period*
Crazing
Buckling
Delamination
Absorber coating
Cracking
Areas affected will result in decrease of thermal
performance.
Fast increase of the problem during test period*
Crazing
Blistering
Insulation
Outgassing
Will result in decrease of thermal performance
*This criterion will only be possible to evaluate if the laboratory makes a daily register of observations of the collector
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The objective of the test is to assess the capability of a collector to withstand a severe thermal shock that can result
from a sudden rainstorm on a hot sunny day.
Test Procedure
Figure 1: External Thermal Shock Test; Fraunhofer ISE
Boundary Conditions
Liquid heating collectors shall either be operated under
standard stagnation conditions (SSC).
An array of water jets shall provide a uniform
distribution of water spraying over the front of the
collector.
The collector shall be exposed for 1 hour prior to the
test with the selected climate reference conditions as
given in Table 2 of ISO 9806:2017.
The collector shall be sprayed with water at a
temperature between 10°C – 25°C at the spraying rate
of 0.03 kg/m2s for at least 15 minutes.
This test shall be performed twice on the collector.
Collectors with overheating protection shall be
operated close to the self-protection trigger
temperature.
"Tips and Tricks"
- Take care of the water spraying temperature. On hot sunny days, the water can be heated up within the inlet
tube;
- Make sure that the spray covers the whole collector front or if it is a very large collector, at least two complete
glass planes.
Manufacturer´s
definition
Test passed
Toughened
glass? yes
Expose the collector to
climatic conditions as
given in Table 2 of ISO
9806:2017
Connect the collector to
a fluid loop as described
in method 2 of Fact
Sheet 10
1h
Spray water for at least 15 min:
- water temperature 10 – 25°C
- spray rate 0.03 kg/m2s
Standard
Stagnation
Temperature is
reached?
yes
no
Glass
breakage?
Test failed
Climate reference conditions as
given in Table 2 of ISO 9806:2017
yes no
no
11 External Thermal Shock Test
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Manufacturers Information Box
- Climate reference conditions as given in table 2 of ISO 9806:2017 must be chosen by the manufacturer;
- In-house testing is recommended to check whether the collector withstands those requirements (also in case of
toughened glass).
Exemplary Results
- Cracking or breakage of collector cover and rain penetration are problems that could be detected within this
test;
- Fogging i.e. condensation of gases on the inside of the cover usually occurs when it is cooled by water. However
this often looks much worse when observed directly after the shock compared to some time after. The result
therefore may need to be reevaluated after the temperature of the collector cover is close to the ambient
temperature.
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The objective of this test is to assess the capability of a collector to withstand a severe internal thermal shock that
can result from the intake of a cold fluid on a hot sunny day. This is likely to occur during system installation when
the collector loop is filled or after a period of shutdown, when the installation is brought back into operation.
Test Procedure
Figure 1: Internal thermal shock test; Fraunhofer ISE
Boundary Conditions
- The collector shall be mounted either outdoors or
in a solar simulator and operated under standard
stagnation conditions (SSC).
- The collectors shall not be filled with fluid.
- One of the fluid pipes shall be connected via a shut
of valve to a heat transfer fluid source.
- The collector shall be exposed for 1 hour prior to
the test with the selected climate reference
conditions as given in Table 2 of ISO 9806:2017.
- The collector is flushed with cold heat transfer fluid
(<25°C) at a fluid flow rate of 0.02 kg/m²s for at
least 5 minutes.
- This test shall be performed twice on the collector.
- Collectors with overheating protection shall be
operated close to the self-protection trigger
temperature.
"Tips and Tricks"
- The test is usually performed in association with the exposure test. To perform the test, keep the collector in dry
stagnation on a sunny day and, after solar noon, flush cold water (mains water) in the collector for 5 minutes.
The fluid flow rate should be similar to the flow rate recommended for the collector in normal operation;
- Pay attention to the blowout of water vapor;
- Direct flown vacuum tube collectors are often highly sensible to internal shocks. Pay attention to the glass
breakage at the lower tube end.
Manufacturer´s
definition
Test passed
Expose the collector to
climatic conditions as given in
Table 2 of ISO 9806
1h
Flush with heat transfer fluid:
- fluid temperature < 25°C
- fluid flow rate 0.02 kg/m²s
Standard
Stagnation
Temperature is
reached?
yes
no
Any
damages?
Test failed
Climate reference conditions as
given in Table 2 of ISO 9806
no
yes
12 Internal Thermal Shock Test (liquid heating collectors only)
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Manufacturers Information Box
- Climate reference conditions as given in table 2 of ISO 9806:2017 must be chosen by the manufacturer;
- In house testing is recommended to check whether the collector withstands the requirements (especially in case
of direct flow vacuum tube collectors).
Exemplary Results
- Loss of vacuum or breakage of the tubes in evacuated tubular collectors, loss of bonding between tubes and
absorber plate or permanent deformation of the absorber plate in flat plate collectors are the most common
problems that can be detected with this test;
- Glass breakage most often occur while testing direct flow vacuum tube collectors. The following pictures show
typical signs of glass breakage.
Figure 2: Damaged collectors after testing; Fraunhofer ISE
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The objective of the test is to assess if collectors are substantially resistant to rain penetration. Collectors may be
equipped with ventilation and/or drain holes but these shall not permit the entry of drifting rain.
Test Procedure
Figure 1: Positioning of collector and spray nozzles for rain
penetration test; Source: ISO 9806:2017
Boundary Conditions
Even for ETC rain is spread on header and bottom
support including caps respectively because water
accumulation at that part would lead to freezing
damage.
Original mounting shall be used especially if the
collector is sold with an in-roof solution.
The detailed test conditions including information
about the required spray nozzles, mass flow rate, spray
angle, and drop size are given in chapter 13.3 of
ISO98026:2017.
Please not that it is not possible to give the exact
positioning of the spray nozzles for each type of
collectors. It is in the responsibility of the testing
laboratory to identify all critical points (areas) where
water penetration could occur.
The number and description of positions of spray
nozzles shall be reported.
Manufacturer´s
definition: Shallowest installation
angle
Mount the collector:
- shade from light if mounted outdoor
- collectors which are installed exclusivly
into a roofstructure shall be mounted in a
simulated roof with their back protected
Pass through half-
exposure?
yes
Half-exposure
no
Collector type
Leave at ambient
temperature
air heating
collector
Keep warm
by circulating a
hot fluid
liquid heating
collector
Determine:
- number of nozzles
- position of the spray
nozzles
Mount and adjust the nozzles
Spray for four hours
Collector should not be
exposed to sun or warm
conditions until final
inspection
Within 72 hours:
final inspection
END
13 Rain Penetration Test
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"Tips and Tricks"
- In case of SAHC, sometimes rain can enter the collector casing quite easily, which maybe not be problematic
issue if the collector is drying out in time according to the standard;
- Water penetration shall be determined by the final inspection within 72 hours after the rain penetration test. But
in-between rain penetration and final inspection tests, the collector has to undergo internal pressure test,
mechanical load test and impact resistance test;
- If the internal pressure test needs to be done at elevated temperatures, it is not admissible to perform both tests
on the same collector;
- If the above mentioned three tests are performed on the same collector as the rain penetration test, the collector
shall be handled in such a way that the result of the rain penetration test is not negatively influenced;
- If the collector does not pass one of these three preceding tests, no evaluation of the rain penetration test shall
be given within the report. The report shall only state that the test has taken place without valid evaluation;
- It is strongly recommended to use a further collector to avoid the aforementioned circumstances;
- Problems are more likely to occur if the collector is mounted with a low tilt angle.
Manufacturers Information Box
The manufacturer can recommend the shallowest collector tilt angle at which the collector can be used in order to
avoid rain penetration problems. If this angle is not indicated the test is performed with a 30º tilt.
Exemplary Results
Examples of problems that are likely to occur if water penetrates and stays in the collector are corrosion of the
collector casing and absorber surface, reduced thermal performance due to persistent condensation on the inner
side of the glass, or reduced insulation properties when the insulation is wet.
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The objective of the test is to assess if a collector which is claimed to be freeze resistant can withstand freezing and
freeze/thaw cycling.
Test Procedure
Figure 1: Climate chambers of the TestLab PV-Modules, Fraunhofer
ISE
Boundary Conditions
Two test procedures are recommended, one for
collectors which are claimed to be freeze resistant
when filled with water or are claimed to resist freezing
after being drained, and the other for collectors
containing heat pipes.
For collectors claimed to be freeze resistant, the
collector shall be mounted in a cold chamber. The
collector shall be fitted correctly, shut completely, and
inclined at the smallest tilt angle to the horizontal
recommended by the manufacturer. Water in the
collector absorber shall be maintained at - 20 ± 2°C for
at least 30 minutes during the freezing part and raised
to above 10 °C during the thawing cycle. Duration of
thaw cycle shall be at least 30 minutes. The collector
shall be subjected to three freeze-thaw cycles and then
inspected for failures.
For collectors containing heat pipes the test can also be
performed in a low temperature fluid loop. The
difference for heat pipe collectors is the tilt angle. Here
the highest recommended tilt angle is considered. The
freeze resistance test consists of ten cycles for this type
of collectors.
Manufacturer´s
definition
Collector
type
Smallest tilt angle to the hoizontal
and lowest temperature
Highest tilt angle and lowest
temperature
- Mount in a cold chamber at
smallest tilt angle
- Install a temperature sensor
Collector type?
Filled with
water at
operating
pressure at
each cycle
freeze resistant
collector
Filled with
water for 10
min,
drained for 5
min
drain down
freeze protection
Test conditions:
Test temperature
such that the
temperature sensor
indicate the required
temperature
END
Select minimum six
heat pipes
(one heat pipe as
control sample)
Half-exposure?
no
Mount in a cold
chamber at
highest
recommended tilt
angle
Test the whole
collector
Mount in a low
temperature fluid
loop at highest
recommended tilt
angle
Detailed initial
inspection of all
heatpipes
Install one
temperature sensor
on a heat pipe at
the lower end
Three cycles:
- 1 h cold
- 1 h warm
Ten cycles:
- 1 h cold
- 1 h warm
heat pipes
Heat pipes
removable?
yes
no
yes
Claimed to be freeze resistant Containing heat pipes
14 Freeze Resistance Test
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"Tips and Tricks"
Freeze resistant collectors:
Collector shall be filled with water at operating pressure and cold chamber temperature, and shall be cycled. At the
end of each cycle the collector shall be refilled with water to operating pressure. Water temperature shall be
monitored during the whole test.
Collectors with drain-down protection:
Collector shall be filled with water and kept at operating pressure for 10 minutes and then drained using the device
installed by the manufacturer.
Collectors containing heat pipes:
The documentation of the shape (round, oval, etc.) and the outside dimensions of all parts of the heat pipes during
the initial inspection as well as the final inspection shall be done by photographs on a graph paper (millimeter
paper), in order to have a direct comparison.
Manufacturers Information Box
Collectors claimed to be freeze resistant:
The test laboratory needs the lowest tilt angle and also the lowest temperature. The test shall be at -20 °C or as
specified by the manufacturer.
Collectors containing heat pipes:
The test is mandatory for all heat pipe collectors. The test laboratory needs the highest tilt angle and also the lowest
temperature. The test shall be at -20 °C or as specified by the manufacturer.
Exemplary Results
Typical results of freeze resistance tests are cracking and/or breaking of fluid channels. The following pictures shows
typical results of a freeze resistance test on heat pipes, done within the project HPQUAL - Investigation of freeze
resistance testing of heat pipes. Both shown results, cracking as well as the deformation shall be deemed as major
failure.
Figure 2: Heat pipe before freeze resistance test (Source: HPQUAL - Investigation of freeze resistance testing of heat pipes; Fraunhofer ISE)
Figure 3: Heat pipes after freeze resistance test (Source: HPQUAL - Investigation of freeze resistance testing of heat pipes; Fraunhofer ISE)
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The mechanical load tests are intended to assess the extent to which the collector and its attachment points are able
to resist positive pressure load due to wind or snow, and negative pressure or uplift forces caused by wind.
Note: The mounting hardware itself is not evaluated by this standard.
Test Procedure
Figure 1: Mechanical load test; Fraunhofer ISE
.
Boundary Conditions
Methods:
- Use of flexible foil and gravel, sand or water
- Suction cups
- Air pressure
Mounting:
- Collector is placed horizontally
- Using the manufacturer´s original mounting
equipment
Maximum test pressure:
- Not specified; is to be define by the manufacturer
Load steps:
- Max. 500 Pa
- Min. 5 minutes per load step
Note 1: If none of these methods is applicable (e.g. for
tracking and concentrating collectors), the laboratory
shall design specific procedures.
Note 2: Depending on the collector type, other
methods may be suitable as well.
Manufacturer´s
definition Maximum positive and negative
load, installation manual
Mount the collector
(use original equipment)
Homogenous load distribution:
- raise load to first load step of min
500 Pa
- hold for minimum 5 min
Permanent
deformation?
Raise load step
by 500 Pa
Document via
photos
Release load
Maximum load
reached?
no
Disassemble and check deformed
parts, document via photos
yes
Final inspection
no
yes
15 Mechanical Load Test
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"Tips and Tricks"
- For the method using suction cups an equal distribution of the pressure is very important;
- The distance between the suction cups and the collector frame shall be half of the distance between the suction
cups itself;
- A continuous measurement of the deflection is recommended to determine if a permanent deformation occurs;
- If a failure of the fixing or mounting system occurs, the test cannot be continued as the degree of freedom for
the collector movement has changed in a way that the representative result for the collector is no longer valid. In
this case, it is recommended to state that the collector resisted one load step before the fixing or mounting
failed;
- If different fixing and/or mounting systems are applicable, it is recommended to use the one with the smallest
load resistance according to the documentation of the manufacturer;
- Relieving the pressure after every load step to 0 Pa is very important to possibly state that the last load step has
withstood before a possible failure occurred.
Manufacturers Information Box
The collector has to be installed using the manufacturer’s original mounting equipment. The documented pressure is
the maximum negative and positive pressure the collector resists during the test.
These values divided by a safety factor can be related to permissible snow and wind load. In each country there are
specific legislations on wind and snow loads since building envelopes have to resist these loads.
Exemplary Results
Typical failures:
- In testing and handling:
o Suction cups, gravel or sand not evenly distributed over the collector
- On the collector:
o Permanent deformation or distortion
o Glass breakage in case of evacuated tube collectors
- Failure of the fixing or mounting system
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The objective of the test is to assess the extent to which a collector can withstand the effects of impact.
Test Procedure
Figure 1: Impact resistance testing facility at Fraunhofer ISE
Boundary Conditions
- The test can be performed using ice or steel balls
- The test procedure consists of 4 shots/drops of the
same impact strength
- Impact locations depending on the collector
technology are defined
Using ice balls:
- The collector shall be mounted on a stiff support,
perpendicular to the path of the projected ice ball
- Ice ball and test specifications are:
Diameter [mm]
15
25
35
45
Mass [g]
1.63
7.53
20.7
43.9
Velocity [m/s]
17.8
23.0
27.2
30.7
Using steel balls:
- The collector shall be mounted on a stiff support,
perpendicular to the path of the dropping steel ball
- Steel ball and test specifications are:
Mass [g]
150 ± 10
Drop Height [m]
0.4, …2 m (0.2 m increment)
.
"Tips and Tricks"
- In case of ETCs, severe impacts can lead to small (non-visible) cracks and loss of vacuum. This can be identified by
the tone of the tubes when softly hit or by whitening of the getter material at the lower end of the tube;
- Proper preparation is important, as in case of a glass breakage the shot/drop cannot be repeated;
Manufacturer´s
definition
damages
no damages
-> next Position
damages
no damages after 4 shots
Ice ball
diameter
Steel ball
drop height
Purchase/
produce and
store ice balls
Install the collector on
a stiff support
allowing for realistic
movements
Pre-
inspection
Adjust drop height/
velocity
Shot/drop
Visual
inspection
abort
END
Define and
document the
impact location(s)
16 Impact Resistance Test
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- The points of impact shall be defined before testing;
- Special considerations on ETCs: If one tube breaks, the test shall be repeated on another tube. If the second one
also breaks, the test shall be considered as failed;
- Perpendicular shot/drop can be difficult, especially when testing ETCs.
Manufacturers Information Box
- The test is started with the smallest ice ball diameter or the lowest steel ball dropping height specified by the
manufacturer;
- The test will be stopped at the largest ice ball diameter or highest steel ball dropping height, or after the first
visible damage;
- The largest ice ball diameter or the highest steel ball dropping height without any damages will be reported.
Exemplary Results
- The collector is visually inspected after testing. Typical results can be small cracks or dents in header box mirrors
or frames, broken glass, or loss of vacuum in case of vacuum tubes;
- The results can often be reported easily by photo documentation;
- Obviously no damages occur on toughened glasses of FPCs with a thickness ≥ 3.2 mm when using ice balls with
diameters ≤ 25 mm.
Figure 2: Collector after ice ball impact test
Figure 3: Damaged collector after steel ball
impact test
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The final inspection corresponds to the dismantling of the collector(s) and shall be done for all tested collector(s).
Most of the results of reliability testing are found at the final inspection. All abnormalities shall be documented and
accompanied by photographs.
Test Procedure
Boundary Conditions
The final inspection shall be done in a suitable
surrounding (e.g. indoors, without irradiation, at room
temperature, etc.).
The final inspection is a destructive test and shall
therefore be the concluding test.
It is recommended to do a final inspection test every
time a durability test procedure is completed. Especially
if the collector fails in one of the tests given in Fact
Sheet 6 to 16.
The collector shall be dismantled and inspected. Any
defects and abnormalities shall be documented. It is
recommended to document all defects and
abnormalities by photographs.
"Tips and Tricks"
- Collectors may contain harmful materials (fluid within heat pipes, getter material within vacuum tubes, thermal
insulation materials made of glass fiber, etc.). It is advisable to obtain the exact material specifications
beforehand from the manufacturer of the collector. Appropriate protective measures should also be taken;
- Dismantling the collector should not influence the results from preceding tests;
- It is recommended to check the material specifications and the design according to the manufacturer´s
specifications during the final inspection;
- In case of tracking and concentrating collectors all collector parts which are required for normal operation like
tracking device, actuators, sensors, etc. shall be inspected.
Manufacturers Information Box
Collectors which are undergoing a final inspection are not usable anymore. Nevertheless in some critical cases it
could be helpful to store the collector at the laboratory or to send it back to the manufacturer. This provides the
possibility for the manufacturer to improve the collector construction on the basis of the visible test results.
Manufacturer´s
definition
Dismantle the collector in an appropriate
sourounding
Technical product
information
Visually inspect all parts/components/materials
for defects and/or abnormalities
Make photographs of any findings
Document the results as required by annex A.2
and Table A.5 of ISO 9806:2017
17 Final Inspection
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Exemplary Results
Results shall be presented as required in chapter A.2 and Table A.5 of ISO 9806:2017.
Any defect and/or abnormality shall be classified in one of the following classifications:
- No problem: If the performance, durability, safety and visual appearance are considered as not affected by
preceding tests. The collector is deemed to remain stable for the expected lifetime.
- Minor problems: These are mainly aesthetical defects. Durability and safety are considered to remain stable
over the expected lifetime.
- Major failures: These are severe premature failures concerning performance, durability, safety or visual
appearance. Table 1 gives a slight overview of major failures found during the final inspection.
Note: All findings rated as ‘minor problem’ or ‘major failure’ shall be documented by photographs.
Table 1: Recommendations for classification of a potential problem as major failure during final inspection
Potential problem
Picture
Potential problem
Picture
Corroded collector box.
Manifold casing after
exposure test
Crack on absorber coating
Cracked collector box
Deformation of absorber tubes
and headers
Cracking of polymeric parts of
manifold
Loss of bonding in absorber tubes
Deformation of polymeric parts
of manifold
Outgassing
Cracked glass after external
thermal shock test
Degradation of PU foam
insulation in manifold casing after
exposure test
Outgassing within Heat Pipe
Tubes
Degradation of insulation
(Picture source: QAiST - IEE/08/593/SI2.529236)
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The compilation of an ISO 9806:2017 compliant test report is carried out in accordance with Annex A2 and A3 of
the standard. Surplus to these requirements, the present Fact Sheet addresses additional rules of conduct in the
preparation of test reports as well as the information required beyond the normative requirements to improve the
intelligibility of the report. The target group for the information given in this Fact Sheet is primarily the testing
laboratories. However, also for manufacturers and certifiers it can help to understand the results documented in the
report.
Test Procedure
"Tips and Tricks"
- A Test Report shall not be published in excerpts to avoid misuse;
- The Test Report is the product the contractor pays for. So it belongs to the contractor. If a third party asks for it,
only with agreement of the owner a test report can be provided;
- A report shall be signed by two responsible persons;
- Test Reports always describe only what has been done with the specific test sample. Based on this information, a
certification scheme might allow for transferring results to technically similar products;
- A Test Report is the ‘product’ of a testing laboratory. In case the laboratory is EN/EC/ISO 17025 accredited, the
Test Report is part of the tracked documents. Therefore a report contains numbering and versioning information
as well as all the details necessary to track the equipment used in this very test, down to the details of calibration
of used sensors;
- A Test Report has no expiry date;
- To implement any corrections, a new version has top be issued saying that it supersedes the pervious version.
Manufacturers Information Box
- To write and issue a report according to ISO 9806:2017 it is absolutely essential that all the data as required by
chapter A.2 of ISO 9806:2017 is available for the testing laboratory. Otherwise the collector design cannot be
clearly fixed and following it cannot be unambiguously assigned to which product design the result relates;
Manufacturer‘s
definition - Type plate
- Installation manual
- Technical documentation
- Data sheet
- Measurement
- Results
Report
18 Test Report
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- Besides, the collector must be accompanied by a type plate showing for e.g. the serial number, the sizes, etc.,
and an installation manual must be available for the testing laboratory to check whether there are information
regarding installation, safety and precautions as well as maintenance is given;
- The results given within the test report are only valid for the tested collector.
Exemplary Results
Exemplary results for the single tests and measurements are given on the related Fact Sheets. Here mentioned is the
newly implemented Standard Reporting Conditions (SRC). The SRC were implemented into the ISO 9806:2017 to
report the power output of the collector in a comparable form, independent of the tests method and the collector
technology. The following definitions are made:
- The SRC distinguish between “Blue Sky”, “Hazy Sky” and “Grey Sky” conditions. For each of those conditions
certain irradiation levels are defined. The exact values are given within Table 7 of ISO 9806:2017;
- The SRC distinguish between global and diffuse Irradiation, meaning, that the power output considers a defined
diffuse fraction, independent from the testing method (SST or QDT). This leads on the one hand to comparable
results. On the other hand the question raises “How to consider the diffuse fraction in case of SST-
Measurements. An answer on this question is given in Fact Sheet 24.1;
- The ambient temperature has been fixed to 20 °C;
- The longwave irradiance, which is to consider in case of measurements on WICS’s, has been set to -100 W/m²;
- The wind speed velocity, which is to consider in case of measurements on WICS’s, has been set to 1.3 m/s;
- The thermal capacity, resulting from QDT-Measurement is always set to zero to calculate the power output;
- The table below shows the detailed SRC:
Table 1: Detailed Standard Reporting Conditions
Climatic conditions
Blue sky
Hazy Sky
Grey sky
Gb
850 W/m2
440 W/m2
0 W/m2
Gd
150 W/m2
260 W/m2
400 W/m2
ϑa
20 °C
20 °C
20 °C
EL -σ.ϑa4 a
- 100 W/m2
-50 W/m2
0 W/m2
ua
1.3 m/s
1.3 m/s
1.3 m/s
dϑm/dtb
0 K/s
0 K/s
0 K/s
a
b
For WISC collectors only.
For quasi dynamic tested collectors only.
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Performance testing includes the assessment of the power output efficiency parameters by the collector under
various operating conditions. This is achieved by determining collector parameters like conversion factor, incident
angle modifier, heat capacity and time constant. The aim of Thermal Performance Testing is to compare different
collectors as well as collector technologies with each other in a fair and transparent way. It is also needed to
calculate the collectors' yearly energy gain (collector annual output, CAO) using different simulation tools.
Test Procedure
Figure 1: Typical outdoor test facility, Fraunhofer ISE
Table 1: Test method to be followed for different types of collectors.
Collector type
SST
QDT
Concentrating Collector (SLHC)
-
SLHC
SAHC
-
OTA-SAHC
-
WISC
SST
Steady State Testing
QDT
Quasi Dynamic Testing
SLHC
Solar Liquid Heating Collector
SAHC
Solar Air Heating Collector
OTA
Open To Ambient
WISC
Wind and Irradiance Sensitive Collector
Advantages/Disadvantages of Different Methods
The two performance test methods, Steady State Testing (SST) and Quasi Dynamic Testing (QDT) exist as equivalent
methods in the standard. Since only the QDT model includes the differentiation of diffuse and direct radiation, this
method is more applicable for collector technologies whose thermal performance is sensible to the diffuse fraction
(e.g. concentrating collectors). For QDT, no tracking facility is necessary which could be an advantage. In case of SST,
the boundary conditions have a direct influence on the collector parameters. Thus the influence of single
development steps (e.g. new absorber coating, etc.) can be easily observed in direct relation to the surrounding
conditions. The methods have been compared in several round-robin tests and the overall uncertainty achieved was
around ±2% (pp) for the ηhem value.
Overview of Thermal Performance Testing related Fact sheets
Fact Sheet 19.2
Thermal performance testing using a solar Irradiance simulator
Fact Sheet 20
Collector mounting and location
Fact sheet 21
Instrumentation
Fact Sheet 22.1
Test installation for liquid heating collectors
Fact Sheet 22.2
Test installation for air heating collectors
Fact Sheet 23
Performance test procedures
Fact sheet 24.1
Computation of results; liquid heating collectors
Fact sheet 24.2
Computation of results; air heating collectors
Fact Sheet 25.1
Measurement and calculation of the effective thermal capacity
Fact sheet 25.2
determination of the collector time constant
Fact Sheet 26
Determination of the incident angle modifier
Fact Sheet 27.1
Determination of the pressure drop; liquid heating collectors
Fact Sheet 27.2
Determination of the pressure drop; air heating collectors
19.1 Thermal Performance Testing
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A solar simulator creates the possibility of the weather-independent performance test, which can be scheduled at a
short notice, with a very high repeatability. On the other hand, it is subject to certain restrictions due to the
characteristics of the artificial irradiation.
Test Procedure
Following tests can be conducted using a solar
irradiance simulator:
Performance measurements:
- Steady-state efficiency measurement
- Determination of the thermal capacity and time
constant
- Determination of the Incident angle modifier (IAM)
Functional tests:
- Standard stagnation temperature
- Internal pressure test
- Air leakage test
- Rapture or collapse test
- Exposure test (after the initial outdoor exposure)
- External thermal shock test
- Internal thermal shock test
Irradiation Requirements of a Solar Irradiance Simulator for Steady State Efficiency Measurements
As the performance of collectors is sensitive to the amount of direct and diffuse d irradiation, only solar simulators
can be used where a near-normal incidence beam of simulated solar irradiation is directed to the collector.
The lamps shall be capable of producing a mean irradiance over the collector gross area of at least 700 Wm².
The irradiation G is usually measured with an automated X-Y system that moves the Pyranometer every 150 mm in
both directions over the whole collector gross area and in the plane of the absorber.
Uniformity of the Simulated Solar Irradiation
At any time the irradiance at a point on the collector gross area shall not differ from the mean irradiance over the
aperture by more than ± 15 %.
The uniformity of the solar simulator must be checked before each efficiency test.
It is desirable that the lamps' intensity settings can be individually controlled from a computer. In this way it is
continuously possible to see the radiation map on the collector and it is possible to adjust the uniformity of the
lamps in a visual and easy way.
Collimation of the Simulated Solar Irradiation
At least 80% (90% for IAM measurements) of the simulated solar irradiance shall lie in the range in which the
incident angle modifier varies by no more than ± 2% from its value at normal incidence.
One way to check the collimation requirement is to use a cylinder that geometrically fulfills the requirements
19.2 Solar Irradiance Simulator
Figure 1: Solar Irradiance Simulator at Fraunhofer ISE
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specified. This cylinder, which must be painted black inside to minimize the reflectance, is placed over the
Pyranometer and irradiance measurements are made at the same point of the collector plane with and without
cylinder. The measurement obtained with the tube must be above 80% for efficiency tests and 90% for incidence
angle modifier tests compared to the irradiance measured without tube in the same point.
Spectral Distribution of the Simulated Solar Irradiation
The spectral distribution of the simulated solar radiation shall be approximately equivalent to that of the solar
spectrum at optical air mass 1.5. It is difficult to find equipment or laboratories that can measure the spectrum from
0.3 µm to 3 µm, especially from 2.5 µm. The spectral distribution of the lamps must be measured by a
Spectroradiometer or outsourcing the characterization of the lamp to an accredited laboratory. It is recommended
to do these measurements for each replacement of the lamps.
In case of spectrally selective absorbers or covers, a check shall be made to establish the effect of the difference in
spectrum on the product for the collector. If the effective values under the simulator and under the optical air mass
1.5 solar radiation spectrum differ by more than 1%, a correction shall be applied to the test results. Measurement
of the solar simulator's spectral qualities shall be in the plane of the collector over the wavelength range of 0.3 µm
to 3 µm and shall be determined in bandwidths of 0.1 µm or smaller.
Infrared Thermal Radiation
The amount of infrared thermal energy at the collector plane shall be suitably measured and reported. The thermal
irradiance at the collector shall not exceed that of a blackbody cavity at ambient air temperature by more than 5%
of global irradiance. To verify this requirement a Pyrgeometer can be used to measure the thermal radiation. Several
measurements are performed in the same plane of the collector and values have to fulfill the standard requirements
by calculation. This measurement is enough to perform for each change of lamps or when ever changes are made in
the simulator or its environment.
To minimize the effect of thermal radiation it is recommended to use a cold sky consisting of a double glass through
which cold air is circulating to get a glass temperature near to room temperature in between the collector and the
lamps.
"Tips and Tricks"
- In some cases, when the collector is manufactured with selective absorbers or covers, the value of the optical
performance measured in the solar simulator can differ from the optical performance value of the same collector
measured under outdoor conditions. This difference depends on the type of lamps used by the simulator and
selective materials used in the collector. It is recommended to check this difference to evaluate if it is necessary
to apply a correction factor;
- If the collimation of the simulator does not meet the requirements of the standard, results of the determination
of the optical performance value will be seriously influenced. Especially when measuring vacuum tubes collectors
or other collectors with odd IAM behaviors, or in incidence angle modifier measurements in general;
- Concentrating collectors should not be measured at all in solar simulators;
- Values in the range 300 W/m² to 1000 W/m² may also be used for specialized tests, provided that the accuracy
requirements can be achieved and the irradiance values are noted in the test report;
- It is recommended to use lamps with levels of radiation that can reach up to 1100 W/m2, so that the simulator
can also be used for function tests according to ISO 9806:2017;
- It is important to take the distance between the collector and the solar simulator into consideration to assure the
desired levels and distribution of radiation;
- It is important to age lamps at the beginning of their life to stabilize the different components of the lamp. It is
also recommended to stabilize lamps of the simulator before any test, the period required being dependent on
the type of lamps used.
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The way in which a collector is mounted will influence the results of thermal performance tests. The present Fact
Sheet gives introduction to normative mounting requirements and some special considerations in case of special
collector types.
Mounting Procedure
Figure 1: Testing facilities of the TestLab Solar Thermal Systems,
Fraunhofer ISE
Boundary Conditions
Normative mounting requirements:
- Mounting shall be done in the manner specified by
the manufacturer;
- Mounting shall in no way obstruct irradiance on
the collector, and shall not significantly affect the
back or side insulation (unless otherwise specified,
for example, when the collector is part of an
integrated roof array);
- Open mounting structures shall be used which
allows air to circulate freely around the front and
back of the collector;
- The collector shall be mounted such that the lower
edge is not less than 0.5 m above the local ground
surface. When collectors are tested on the roof of a
building, they shall be located at least 2 m away
from the roof edge.
Special considerations / collector types
- WISCs without backside shall be mounted on an
insulated backing with a thermal conductivity of
1W/m²K ± 0.3W/m²K, and the upper surface
painted matt white and ventilated at the back;
- ETC without back side mirror shall be mounted on
a dark surface to avoid irradiation on the tubes´
back side.
- Roof integrated collectors shall be mounted using
their original roof covering as delivered by the
manufacturer.
Manufacturer´s
definition
Use of other parts
can cause defects
or influence the
thermal
behaiviour!
Use of other parts
can cause defects
or influence the
thermal
behaiviour!
Installation instruction, flow
pattern, absorber layout, flow rate
Mount the collector on:
Open frame
structure in case
of on roof
collectors (FPC,
VCT, etc.)
Fix the collector using
the original parts
Insulated structure in
case of WISC and
collectors which are
built on-site
Simulated roof in
case of roof
integrated
collectors
Protect the collector
from irradiation (if
necessary)
To avoid internal
thermal shocks
while filling!
To avoid internal
thermal shocks
while filling!
Connect the collector
to the hydraulic circuit
Use the original
connectors to
avoid leakages!
Take care about
the flow direction!
Use the original
connectors to
avoid leakages!
Take care about
the flow direction!
Fill and rinse the
collector/hydraulic
system
It is recommended
to use a high mass
flow rate to ensure
that all air is
bleeded!
It is recommended
to use a high mass
flow rate to ensure
that all air is
bleeded!
Check the collector/
connectors for
leakages
leakages?
Insulate the
connectors
Set up the measurement parameters
(fluid flow rate, inlet temperature, etc.)
Start measurement
20 Collector Mounting and Location
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"Tips and Tricks"
- Always use the original mounting equipment to fix the collector to your testing facilities;
- Always use the original installation instruction to install the collector in the right manner;
- Always notice manufacturer’s limitations (e.g. inclination, mass flow rate);
- Always check the internal flow distribution before connecting the collector to your hydraulic circuit (e.g. by a
technical drawing);
- The minimum inclination of the collector should be reasonable in comparison to its technology;
- Air within the hydraulic circuit can be bled through a high mass flow rate. It’s important to install an air bleed
valve within the hydraulic circuit; vary the mass flow rate and temperature for bleeding;
- As the performance of collectors is sensitive to the wind conditions, the use of artificial wind generators is
recommended. Note that the turbulence level of artificially generated wind is often higher compared to that of
natural wind adjacent to the collector surface (esp. at required collector area of at least 3 m²) that leads to an
overestimation of heat loss and the wind depending coefficients;
- Long wave radiation: Due to the specific characteristics of infrared sensitive collectors it is particularly important
that surfaces in the field of view of the collector (including back side) are kept at temperatures close to the
ambient;
- Currents of warm air, such as those which rise up the walls of a building or an exhaust chimney, shall not be
allowed to pass over the collector;
- The use of inappropriate mounting equipment can lead to damages, which are not directly visible but influencing
the performance and/or the functionality.
Manufacturers Information Box
- The manufacturer should deliver the original mounting equipment;
- The manufacturer should deliver an installation manual describing how to install the collector as well as all the
limitations (mass flow rate, internal pressure, inclination, etc.).
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Solar Radiation Measurement – General
Accurate irradiance measurements are quite difficult to perform but indispensable for accurate determination of
collector efficiency. Care should be taken to avoid shading and reflected irradiance on collector and measuring
equipment. Measurement equipment shall always be well aligned with the collector tilt and azimuth. If a
Pyrheliometer is used, the tracking errors associated to the mounting on the tracker must not exceed ± 0.5°. All
irradiance sensors must be Class I or better, as specified in ISO 9060.
A good maintenance of radiation instruments includes regular cleaning and checking of desiccant
condition.
Global, Diffuse and Direct Irradiance
The power output of some collector designs such as ETCs, CPCs and any other concentrating type of collector will
strongly depend on the distinction between beam and diffuse irradiance. Diffuse irradiance can be measured by a
Pyranometer equipped with a shadow ring or tracking ball, direct irradiance by a tracked Pyrheliometer, global
irradiance by a regular Pyranometer. Depending on the combination of instruments chosen, one of the quantities
can be calculated from the formulas:
Best results will be reached with a combination including a Pyrheliometer to measure the direct normal irradiance
(DNI). For highly concentrating collectors (CR > 3) the usage of a Pyrheliometer is mandatory.
Thermal Radiation Measurement
The consideration of the long wave irradiance EL is needed for the characterization of infrared sensitive collectors
(e.g. collectors for swimming pool heating) and can be measured using a Pyrgeometer mounted in the plane of the
collector. If long-wave irradiance is accounted for, it shall be determined to a standard uncertainty of 10 W/m².
Temperature Measurement - General
Mounting position, immersion depth and fluid flow characteristics are crucial for the quality of temperature
measurements. The sensors shall not be more than 200mm from the collector inlet and outlet. The pipework should
be carefully insulated, ideally including the sensor head itself.
Liquid Heating Collectors
Air Heating Collectors
The sensor probe shall always point upstream, and a
bend in the pipe work, an orifice or a fluid-mixing
device shall be placed upstream of the sensor to
ensure turbulent flow at the position of temperature
measurement. A large immersion depth up to 10
times the inner pipe diameter minimizes
temperature losses to the outside. The difference
between the collector outlet and inlet temperatures
(ΔT) shall be determined to a standard uncertainty
of < 0.05 K and to an accuracy of better than 1 %.
The flow distribution shall be homogenized
constructively over the channel cross-section. The
temperature measurement shall be designed in a way
that temperature gradients are balanced over the
channels cross-section. The temperature of the heat
transfer fluid at the collector inlet shall be measured to a
standard uncertainty of ± 0.2 K.
21 Instrumentation
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Surrounding Air Temperature
A highly reflecting casing with forced ventilation is strongly recommended. Additionally, the sensor itself should be
positioned in the shade and no more than 10 meters away from the collector. The ambient air temperature shall be
measured to a standard uncertainty of < 0.5 K.
Flow Rate Measurement
The standard uncertainty of the mass flow rate measurement shall be within ± 1 % of the measured value for liquid
heating collectors and ± 2 % for air heating collectors.
Air Speed Measurement
Air speed measurement is not referring to meteorological wind speed but air velocity over the collector surface. This
quantity is difficult to measure as the sensors are positioned at the collector edges. The sensor monitoring the air
speed during performance testing shall be calibrated relative to the mean air speed measured 50mm over the
collector surface by a handheld anemometer.
The speed of the surrounding air over the front surface of the collector shall be measured to a standard uncertainty
of < 0.5 m/s.
Elapsed Time Measurement
A simple computer clock can be used to measure the elapsed time within acceptable uncertainty.
Humidity Measurement (Air Collectors)
The humidity ratio XW shall be measured to an accuracy of ± 0.001 (kg water/kg dry air) at 25 °C fluid temperature.
Collector Dimensions
The collector dimension shall be measured to a standard uncertainty better than 0.3 %. Measurements shall be
performed at a collector temperature of 20 °C ± 10 °C.
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This fact sheet contains information about the test installation.
Test Setup for Liquid Heating Collectors
Test Setup for Air Heating Collectors
Figure 1: Example of a closed test loop. Description of the
components can be referred to from the Standard.
Figure 2: Closed test loop for SAHC
Figure 3: Open to ambient test layout for SAHC
Boundary Conditions
Boundary Conditions
Use water or a fluid recommended by the collector
manufacturer (the specific heat capacity and density
should be within ± 1 % over the range of fluid
temperatures used during the test).
The pipe work and the fittings shall be insulated such
that the temperature gains or loses between the
temperature measuring point and collector inlet and
outlet are reduced as much as possible. Air bubbles
and any contaminants shall be removed.
The mass or volume flow rate through the collector
shall be stable within 1% despite temperature
variation.
Every component in the measurement loop shall have a
leakage rate less than 2 m³/h at 250 Pa.
The mass flow rate through the collector shall be stable
within ± 1.5 % despite temperature variations. The
waste heat from the fan shall not influence the
temperature measurement.
The preconditioning of the collector inlet temperature
shall be controlled by a device which can hold the inlet
temperature stable within ±1.0 K during the test
period.
The humidity ratio shall be the same in the collector
and of the surrounding air, if the test pressure is
negative, for example, by testing in an open loop.
22 Test Installation
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"Tips and Tricks"
"Tips and Tricks"
- The mass flow rate of the heat transfer fluid
should be the same during the test sequence used
to determine the power curve, time constant and
incident angle modifier for a given collector;
- Pipe lengths should generally be kept short to
reduce the effects of the environment on the
(inlet) temperature of the fluid;
- Insulate the pipes and use reflective covers (also
weather proof for outdoor measurements);
- Install a short length of transparent tube in the
fluid loop: air bubbles, contaminants can be
observed;
- Avoid any drift in the collector inlet temperature.
Note: If non-aqueous fluids are used the compatibility
with system materials should be confirmed.
General:
- To avoid any drift in the collector inlet temperature
an air preconditioning apparatus shall be used;
- It is important to measure and control the humidity
at the different measuring points. Especially it is
important to avoid condensation that occurs
within the testing loop.
Closed loop:
- If a speed controlled (RPM regulated) fan is used, a
flow meter should be used at the inlet and outlet;
- Measured at ambient pressure (can be realized by
using two fans).
Open to ambient:
- The mass flow can only be determined at the
collector outlet;
- The collector inlet temperature corresponds to the
ambient temperature.
Manufacturers Information Box
Manufacturers Information Box
The test laboratory needs the fittings for the test
installation and other installation materials.
The test laboratory needs the installation materials. In
cases of special connectors or special forms of collector
inlet and outlet, the test laboratory needs adaptors for
round flexible tubes with a standard diameter like
200mm.
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The thermal performance of a collector shall either be tested according to the Steady-State Testing (SST) or
the Quasi-Dynamic Testing (QDT) procedure as given in ISO 9806:2017.
Procedure
"Tips and Tricks"
- In case of SAHC, it is important to measure the time constant first because it can reduce the time effort for
testing significantly and avoid failures in testing;
- In case of liquid heating FPCs, usually a “time constant” of 10 minute is sufficient. The time constant shall be
long enough to make sure that the steady state conditions have been reached;
Manufacturer´s
definition
Installation instruction, fluid flow rate
Precondition the collector
Mounting and installation
(see Fact Sheets 20 and 22)
Test Period SST:
· 4 inlet temperatures equally
distributed over the working
temperature range
· at each temperature level 4 efficiency
points are required
· stationary conditions for the mass flow
rate, the irradiation, the ambient
temperature, etc., are required
· only one test sequence is required,
which can be performed on one day
with blue sky conditions
SST or QDT
Data evaluation SST
See Fact Sheet 24.1 and 24.2
Data evaluation QDT
See Fact sheet 24.1
Test Period QDT:
· 4 Inlet temperatures equally
distributed over the working
temperature range
· at each temperature level 4 efficiency
points are required
· variable conditions regarding the
irradiation are needed
· stationary conditions only required for
the mass flow rate and the inlet
temperature
· different test sequences on single days
are required
23 Performance Test Procedures
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- It is recommended to check the flow pattern against the chosen flow rate before testing. Often a simple
calculation shows that the fluid flow will change from transient to intransient behavior by the temperature rise.
This could lead to a discontinuous efficiency curve;
- In case of WISCs, it is important that the radiation towards the collector´s acceptance angle is well known and
taken into account by the radiation sensor. A close-by building, lake or even window refection can cause
significant influence.
Manufacturers Information Box
There has been inter-comparison test on different methods as well as different testing laboratories. The variation for
example η0,hem result was within ± 2% (pp). From an accredited laboratory one can expect such an uncertainty at
maximum.
Exemplary Results
The power output curves shown in the following figure are based on the SRC. For more information about the SRC
see Fact Sheet 18. These power curves show the behavior of the collector under different irradiation conditions over
its working temperature rage.
Figure 1: Power output curves per collector unit under different irradiation conditions
- The power output is given in Watt (y-axis) over the difference of the collector mean temperature and the ambient
temperature (x-axis). Since extrapolation causes a high risk of errors, the power curve shall only be drawn in a
range of maximum +30 K over the highest tested inlet temperature and maximum -10 K lower than the lowest
inlet temperature;
- The peak power is reached where the collector middle temperature is equal to the ambient temperature,
meaning that no thermal losses occur;
- The peak power must always be stated within the test report;
- Furthermore, it must be clearly stated that the results is only valid in the shown range;
- The power output is always given per collector unit;
- Negative power outputs shall not be given within the chart and/or the related table.
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This Fact Sheet contains information about the computation of collector parameters including the power
extracted
, the solar energy intercepted, and information about modelling the instantaneous efficiency
and the power output of liquid heating collectors.
Procedure
Useful power extract as defined by Eq, 10 of ISO 9806:2017
Measurement as described in Fact Sheet 23
Perform last square fit
using Eq. 11 of ISO 9806:2017
SST
Energy intercept as defined by Eq. 11 of ISO 9806:2017
Data file consiting of at least 4 valid data points per inlet
temperature
Sets of SST parameters
yes
Tratio < 3
for one of the parameters?
Set the parameter to
zero
Final set of parameters
Calculate η0,b and KΘ,d
(requires information about the IAM)
Calculate the power output of the collector under SRC
no
Manufacturer´s
definition All technical information as defined in annex A.2 of ISO 9806:2017
Measurement as described in Fact Sheet 23
Perform last square fit
using Eq. 13 of ISO 9806:2017
QDT
Energy intercept as defined by Eq. 13 of ISO 9806:2017
Data file fulfilling the requirements given in chapter 23.6.2.3 of ISO
9806:2017
Sets of QDT parameters
yes
Tratio < 3
for one of the parameters?
Set the parameter to
zero
Final set of parameters
Calculate the power output of the collector under SRC
no
Parameter a5 > 0 ?
no
yes
24.1 Computation of Parameters (liquid heating collectors)
Guide to the standard ISO 9806:2017
55
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"Tips and Tricks"
- Under no circumstances it is admissible to set parameters to zero without repeating the data analysis and
without re-fitting the other parameters;
- For WISC or collectors with a concentration ratio the parameter a8 may set to zero;
- For covered collectors tested with artificial wind source the coefficients a3, a4, a6 and a7 are set to zero;
- Concentrating collectors without transparent cover and a concentration ration of CR < 10 shall be treated as
WISC collectors;
- Concentrating collectors with transparent cover and with a concentration ratio of CR < 3 shall be treated as any
other collector;
- For concentrating collectors with a transparent cover and a concentration ratio of CR > 3, wind speed
dependency can be neglected;
- For evacuated concentrating collectors wind speed dependency can be neglected independent of the
concentration ratio CR;
- The thermal performance of highly concentrating tracking collectors is usually tested according the quasi-
dynamic test method. The steady-state method may be used if a distinction between beam and diffuse
irradiance is taken into account. However, in this case the requirements for quasi-dynamic testing related to
concentrating collectors shall be followed;
- For collectors with a concentration ratio of CR < 20 the use of ƞ0,b, K(ƟL, ƟT), a1, a2 and a5 is mandatory for the
computation of the efficiency result;
- For collectors with concentration ratio CR > 20, the parameters a2, a3, a4, a6, a7 and Kd may be set to zero. a5 is
mandatory an shall be identified;
- Since SST does not distinguish between direct and diffuse irradiation, an additional calculation step is necessary
to determine the parameters ƞ0,b and Kd, which are necessary to calculate the power output according to the
SRC. Basic information for the calculation of these parameters is the result of the IAM-Measurement. This leads
to the situation that, unlike the former standards, the SST efficiency measurement will be incomplete without
performing the IAM measurement.
Manufactures Information Box
It is important to deliver all the technical information as defined in annex A.2 of ISO 9806:2017 to the testing
laboratory. Otherwise the test lab cannot estimate if the result is plausible for the tested product.
Exemplary Results
The data file for the last square fit shall contain at least the information given within the following table.
Table 1: Measurement Data from SST or QDT measurement as a basis for the last square fit
- In case of liquid heating collectors as well as closed loop solar air heating collectors, the results of the last square
fit must be reported as shown in Table A.6 of ISO 9806:2017;
- For a good comparability It is important to use exactly the decimal places as given within Table A.6 of ISO
9806:2017;
- The calculation of the power output is to perform on the basis of the values given within Table A.6 of ISO
9806:2017 according to the SRC.
Guide to the standard ISO 9806:2017
56
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This Fact Sheet contains information about the computation of collector parameters including the power
extracted
, the solar energy intercepted, and information about modelling the instantaneous efficiency
and the power output of air heating collectors.
Procedure
Useful power extract as defined by Eq. 14 0f ISO 9806:2017
Measurement as described in Fact Sheet
23
Energy intercept SHAC OTA as defined
by Eq. 14 of ISO 9806:2017
Perform last square fit
(per mass flow rate) using Eq. 11 of ISO
9806:2017
Energy intercept for SAHC CL as defined
by Eq. 11 of ISO 9806:2017
Data file consiting of at least 4 valid data
points per inlet temperature at 3
different mass fow rates
three sets of
parameters (one per
mass flow rate)
yes
Tratio < 3
for one of the
parameters?
Set the
parameter to
zero
Three final sets of parameters (one per
mass flow rate)
Put in the final parameter sets into the
software tool AirCow
(www.kollektortest.de)
Get the mass flow optimized efficiency
ηopt
Calculate η0,b and KΘ,d
Calculate the power output of the
collector under SRC
no
Measurement as described in Fact Sheet
23
Calculate the instantaneous efficiency
per mass flow rate as the mean value of
each inlet temperature level
Data file consiting of at least 4 valid data
points per inlet temperature at 3
different mass fow rates
Calculate the power output of the
collector under SRC
Measurement as described in Fact Sheet
23
Energy intercept for WISC SAHC as
defined by Eq. 16 of ISO 9806:2017
Data file consiting of at least 4 valid data
points per inlet temperature at 3
different mass flow rates and 3 different
wind velocities
Calculate the instantaneous efficiency per
mass flow rate and per wind speed
velocity as the mean value of each inlet
temperature level
Calculate the wind speed dependent
efficiency value bu
Calculate the power output of the
collector under SRC
Manufacturer´s
definition All technical information as defined in annex A.2 of ISO 9806:2017
24.2 Computation of Parameters (air heating collectors)
Guide to the standard ISO 9806:2017
57
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"Tips and Tricks"
- In case of air heating collectors only SST-Measurements are possible;
- The equation for the useful power extracted (Eq. 14 of ISO 9806:2017) requires to take both inlet and outlet
fluid flow rate into consideration as both flow rates can differ from each other due to leakages;
- In case of closed loop SAHCs, the same equations for the last square fit are used as the computation of SST-
Parameters of liquid heating collectors;
- The parameters of closed loop WISC SAHC are computed in the same manner as SST-Parameters of liquid
heating collectors;
- Under no circumstances it is admissible to set parameters to zero without repeating the data analysis and
without re-fitting the other parameters;
- To make the results of air and liquid heating collectors comparable to each other, a software tool called AirCow
was developed by Fraunhofer ISE. This tool calculates on the basis of three sets of parameters, one optimum
mass flow rate as well as the mass flow rate optimized efficiency value. Therewith it is possible to feed in the
results into e.g. Solar Keymark data sheets in the same manner as the liquid heating collectors. Besides the
calculation of the yearly energy gain can be done in a comparable way (e.g. using ScenoCalc);
- Since SST does not distinguish between direct and diffuse irradiation, an additional calculation step is necessary
to determine the parameters ƞ0,b and Kd, which are necessary to calculate the power output according to the
SRC. Basic information for the calculation of these parameters is obtained from IAM-Measurement. This leads to
the situation that, unlike the former standards, the SST efficiency measurement will be incomplete without
performing the IAM measurement;
- In case of open to ambient SAHCs the inlet temperature cannot be adjusted to certain levels. This leads to the
situation, that for those collector technologies only instantaneous efficiency points can be determined. If closed
loop testing is possible (e.g. by constructing individual inlet ducts), it is strongly recommended to perform a
closed loop measurement. This could avoid disadvantages in marketing and heighten the comparability to other
products;
- In case of open to ambient SAHC-Measurements it is not possible to calculate ƞ0,b and Kd. A calculation of the
power output according to SRC is not possible yet. However to calculate the power output of OTA SAHCs, it is
recommended to calculate it on the global hemispherical irradiation Ghem.
Manufactures Information Box
- It is important to deliver all the technical information as defined in annex A.2 of ISO 9806:2017 to the testing
laboratory. Otherwise the test lab cannot estimate if the result is plausible for the tested product;
- The manufacturer shall deliver suitable air ducts to connect the collector to the hydraulic circuit of the testing
facility;
- The manufacturer shall define the range of mass flow rates in which the SAHC is operated.
Exemplary Results
- The data file for the last square fit shall at least contain the same information as shown in Fact Sheet 24.1;
- The power curve for closed loop SAHCs are presented in the same manner than shown in Fact Sheet 23;
- The thermal performance of open to ambient SAHCs shall be presented as required by Table A.9 of ISO
9806:2017;
- The power output of open to ambient SAHCs shall be presented in form of single instantaneous power points
over the temperature difference of the collector mean temperature and the ambient temperature.
Guide to the standard ISO 9806:2017
58
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a
The effective thermal capacity and the time constant of a collector are important parameters which describe its
transient behaviour.
Determination of the Effective Thermal Capacity
Determination of the Time Constant
Boundary Conditions
Boundary Conditions
- The effective thermal capacity of a collector can
be determined directly via quasi dynamic testing
(term c5), through a separate indoor or outdoor
measurement or via a calculation;
- If QDT method is chosen-
o use a flow rate equal to that of the
efficiency measurement
- The time constant of a collector can be determined
through covering or uncovering the collector;
- Use a flow rate equal to that of the efficiency
measurement;
- The collector shall be shielded from the solar
radiation by means of a solar-reflecting cover, and
the temperature of the heat transfer fluid at the
Manufacturer´s
definition
Method 1
Measurement with
irradiance
Method 2
Measurement with
QDM
Method 3
Calculation
Mount the collector
as for performance
measurement testing
Shield the collector
from solar
radiation (natural
or simulated)
C = Eq. 18 of ISO
9806 C = a5 • A
Investigate the
mass of all material
on the basis of
technical
documentation or
weighing of the
single components/
materials
yes
Set
ϑin ≈ ϑa
Steady stade
conditions
reached?
no
Remove the cover
quickly
Collect data
ϑout <0.5 K or
steady stade
conditions
reached?
no
Fluid flow rate,
technical description of the product
Perform QDT-
measurement
(see fact sheet 23)
Parameter
identification
(See Fact Sheet
24.1)
yes
Determine the
thermal capacity of
each component/
material
Weight the single
capacities by the
weighing factor pi
as given in Table 8
of ISO 9806:2017
C = Eq. 19 of ISO
9806
END
Method 1
covering
Method 2
uncovering
Mount the collector in a solar
irradiance simulator or outdoor
under natural solar irradiance
Measure:
- collector fluid temperature on
inlet and outlet
- surrounding air temperature
Measure up to steady-state-
conditions with the collector inlet
temperature approximatly equal to
to ambient air temperature
cover the collector by shielding
from solar radiation
measure up to steady-state
conditions
Plot the graph as shown in the
exemplary results and determine
the collector time constant.
Mount the collector in a solar
irradiance simulator or outdoor
under natural irradiance
Measure:
- collector fluid temperature on
inlet and outlet
- surrounding air temperature
Measure up to steady-state-
conditions with the collector
inlet temperature approximatly
equal to ambient air
temperature
Cover the collector by shielding
from solar radiation
Uncover the collector
Measure up to steady-state
conditions
Plot the graph as shown in the
exemplary results and
determine the collector time
constant.
Manufacturer´s
definition Fluid flow rate,
technical description of the product
25 Effective Thermal Capacity and Time Constant
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59
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o Test under SST conditions
o Use a reflecting coverage material
- If QDT is used, a high variability in solar radiation
during the test is required so that the thermal
capacitance effects will be significant. If the
parameter c5 cannot be properly identified by
QDT, it can be calculated by method 2;
- If the calculation method is used, the thermal
capacity of the collector C (expressed as Joules
per Kelvin) is calculated as the sum, for each
constituent element of the collector (glass,
absorber, liquid contained, insulation), of the
product of its mass mi (expressed in kilograms), its
specific heat ci (expressed as joules per kilogram
Kelvin) and a weighting factor pi.
collector inlet shall be set approximately equal to
the ambient air temperature. When a steady-state
has been reached, the cover shall be removed and
measurements continued until steady-state
conditions have been achieved again;
- Alternatively a method that provides equivalent
results is to measure the time constant during a
cool down period rather than a heat up period. To
accomplish this, first achieve steady-state
conditions with a steady inlet temperature and
irradiance, and then turn off the irradiance while
monitoring the required measurement quantities.
"Tips and Tricks"
"Tips and Tricks"
- In case of SLACs the fluid content has a high
effect on the effective thermal capacity and shall
not be neglected. The thermal capacity of the
heat transfer fluid used shall be considered for the
calculation of the effective thermal capacity;
- In case of SAHCs the fluid capacity shall be
calculated as described in VDI 4670. All parts of
the collector which are in direct contact with the
air flux shall be weighted by 1;
- For drain-back and drain-down systems, the
capacity should be reported for the collector while
it is filled with water and while it is empty.
- Since outdoor conditions are often unstable it is
recommended to perform indoor measurements to
determine the collectors’ time constant;
- The calculation of the factor b as well as the result
presentation can be done by the following
equation:
)
which leads to:
Manufacturers Information Box
Manufacturers Information Box
- Higher the effective thermal capacity of a
collector, slower is its response to temperature
changes;
- The knowledge of the effective thermal capacity
allows the precise calculation of the annual
collector energy gain within several simulation
tools.
The time constant of the collector is the elapsed time
between turning off the irradiance and the point
where the collector temperature rise drops to 63.2 %
of its steady-state value, since the final steady-state
value will be a temperature rise of zero.
Exemplary Results
Exemplary Results
Table 1 shows typical range of the effective thermal
capacity for different collector technologies.
Table 1: Effective thermal capacity
FPC
ETC
SAHC
Ceff (kJ/m2K)
6 – 12
10 – 25
15 - 45
Figure 1: Graph of temperature difference between inlet and outlet
of collector (ϑe-ϑa) versus time
Guide to the standard ISO 9806:2017
60
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The incidence angle modifier is defined as the ratio of the peak efficiency at a given angle of incidence and the peak
efficiency at a defined reference angle of incidence. Determination of collector incidence angle modifier helps to give
an accurate representation of collector output over a wide range of climate conditions when solar irradiance is not
near normal incidence. This collector characteristic is for instance used in ScenoCalc when simulating collector
energy yield throughout an entire year under varying climate conditions.
Test Procedure
Figure 1: Longitudinal and transversal plane as reference for IAM
description; Fraunhofer ISE
Boundary Conditions
The determination of the IAM is only necessary if the
efficiency measurement has been done by SST. In case
of QDT the IAM is an integral result of the collector
model.
The knowledge about the IAM behavior is important.
Or else the results from the different collector models
are not comparable to each other.
"Tips and Tricks"
Since the inlet temperature of open to ambient SAHCs cannot be varied from the working temperature range of the
collector, the determination of the optical efficiencies ƞ0,hem and ƞ0,hem(ƟL,ƟT) is not possible. Further the calculation
of the IAM-value Khem(ƟL,ƟT) is also not possible. In case of open to ambient SAHCs, it is recommended to estimate
the IAM on the basis of a calculation or simulation and to try and validate the result by an efficiency measurement at
the same incident angle.
A simple device for measuring the angle of incidence of direct solar radiation can be produced by mounting a
pointer normal to a flat plate on which graduated concentric rings are marked. The length of the shadow cast by the
pointer may be measured using the concentric rings and used to determine the angle of incidence. The device shall
be positioned in the collector plane and to one side of the collector.
For collectors with more complex optical properties, values at 20, 40 and 60° might be required to have an accurate
determination of the complete incidence angle modifier. Collectors with non-symmetrical behaviour around normal
incidence require separate measurements before and after solar noon for a proper determination of its behaviour.
Manufacturer´s
definition
Operate the collector as for efficiency
measurement
Set the mean fluid temperature as close
to the ambient temperature as possible
Measure at least at two different incident
angles between 20° and 70° using one
of the following methods
Method 1, applicable for:
- indoors using a simulator
- outdoors using a two-axis
tracking facility
Method 2, applicable for
outdoor measurements on a
stationary rack
Operate the collector under
stable SST-Conditions
Operate the collector under
unstable SST-Conditions
Requires to measure one value
before and one additional after
noon!
Gdiff shall be
less than
30%
Take Care of
the tilt
Gdiff shall be
less than
30%
Take Care of
the tilt
Take Care of
the tilt angle
of the
collector,
especially in
case of heat
pipe collectors
Take Care of
the tilt angle
of the
collector,
especially in
case of heat
pipe collectors
Calculate the efficiency value
Ƞ0,hem (ƟL, ƟT)
In case of Method
2, use the
average value of
both directions
In case of Method
2, use the
average value of
both directions
Calculate the IAM-Value
Khem (ƟL, ƟT) = Ƞ0,hem (ƟL, ƟT)/Ƞ0,hem
Installation instruction,
fluid flow rate
26 Determination of the Incident Angle Modifier
Guide to the standard ISO 9806:2017
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Unlike former standards the calculation of IAM values on the basis of the Ambrosetti function is permitted. Thus the
measurement at one incident angle would be sufficient to calculate the values in a range of 0° up to 90°.
Nevertheless the standard requires measuring at least at two different incident angles.
Manufacturers Information Box
The longitudinal plane (index L) runs parallel to the optical axis of the collector, and the transversal plane (index T) is
perpendicular to the optical axis. The angles ƟL and ƟT are the projections of the incidence angle onto the
longitudinal and transversal planes.
For those collectors (e.g. evacuated tube collectors and CPC collectors) for which the incidence angle effects are not
symmetrical with direction of incidence, it is necessary to measure the incident angle effects from more than one
direction to fully characterize the incident angle modifier. For conventional flat plate collectors it is enough to
measure the incidence angle modifier at 50° incidence angle in one plane.
Exemplary Results
For conventional flat plate collectors the IAM can be given either as a constant value for 50°. It can also be given as
constant values at e.g. 10°, 20°, 30°, 40°, 50°, 60°, 70°, and 80° without distinguishing between longitudinal and
transversal. For collectors with non-symmetric optical characteristics it is necessary to distinguish between
longitudinal and transversal for these angles (i.e. bi-axial IAM) and it can also be necessary to determine individual
IAMs for each of the four quarter spheres (i.e. multi axial IAM) .
IAMs at high incidence angles have a higher uncertainty but on the other hand they normally have a low influence
on the annual energy output.
Figure 2: Graph of IAM K(Ɵ) versus Incidence angle Ɵ; Fraunhofer ISE
Guide to the standard ISO 9806:2017
62
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For designers of solar collector systems, the pressure drop across a collector maybe of importance (e.g. for sizing of
pumps).
Test Setup
Figure 1: Test setup for determination of pressure drop; Fraunhofer
ISE
Key
1
Pyranometer
2
Outlet temperature (Tout)
3,6
Pressure gauge
4
Ambient Temperature (Tamb)
5
Inlet temperature (Tin)
7,9
Ventilator
8
Volumetric flow meter
Test Procedure
Boundary Conditions
The following data shall be measured:
- fluid temperature at the collector inlet;
- fluid flow rate;
- heat transfer fluid pressure drop between the
collector inlet and outlet connections;
- the heat transfer fluid pressure drop across the
collector shall be measured with a device having a
standard uncertainty of 5 % of the measured value
or ± 10 Pa, whichever is higher.
The following test conditions are given during the test:
- the fluid flow rate shall be held constant within
±1% of the nominal value;
- temperature of the fluid shall be 20 ± 2°C;
- at least five measurements shall be made at values
equally spaced over the flow rate range. The zero
levels for flow rate and pressure drop shall be also
checked;
- the pressure drop of the fittings has to be
subtracted from the measured values after the test
(e.g. determination through a short circuit test
using only the fittings).
Manufacturer´s
definition Mass flow range,
flow direction
Install:
- temperature sensor at inlet
- differential pressure sensor at inlet and
outlet
- fluid flow meter
Place the collector indoors. It shall not be
heated up by irradiation while testing
Determine the function of the pressure drop
curve by fitting the measurement points.
Additional pressure drop caused by your
measurement equipment (e.g. connectors)
shall be substracted from the collectors
pressure drop
Measure the pressure drop across the
collector over its mass flow range
Present the results as a table and graphically
as a function
27 Determination of Pressure Drop
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63
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"Tips and Tricks"
- As different heat transfer fluids result in different pressure drop characteristics and thus give different curves, the
pressure drop should preferably be measured using a fluid with similar properties as the one to be used in
practical applications. In particular if the results are to be used by system designers and not only for relative
comparisons;
- In the absence of specific flow rate recommendations by the manufacturer, pressure drop measurements shall
be made over the range of flow rates from 0.005 kg/s to 0.03 kg/s per square meter of collector gross area;
- For unglazed collectors flow rates from 0.02 kg/s to 0.1 kg/s per square meter of collector gross area shall be
used if the specifications are not given from manufacturer;
- The fluid shall be inspected to ensure that it is clean. The collector shall be vented of air by means of an air bleed
valve or other suitable means, such as increasing the fluid flow rate for a short period to force air from the
collector;
- Pressure drop tests at other temperatures may be important for oil-based heat transfer fluids;
- Particular attention shall be paid to the selection of appropriate pipe fittings at the collector entry and exit ports;
- The edges of the holes on the inside surface of the duct shall be free of burrs;
- Particular attention shall be paid to the selection of appropriate pipe fittings at the collector entry and exit ports.
Manufacturers Information Box
- The determination of pressure drop is no more an optional test. The manufacturer documents have to show
data for pressure drop across the collector. The standard does not state if the test is obligatory or not. It depends
on the certification scheme rule;
- The flow direction can have an influence about the pressure drop. Therefore the laboratory needs information
about the flow direction;
- Depending on the purpose of testing (for sizing of pumps or for documentation issues) the manufacturer should
suggest a specific fluid for the test;
- The manufacturer should recommend the operational specific range of flow rates of the collector.
Exemplary Results
The pressure drop between the collector-inlet and the collector-outlet is shown in the pressure drop curve at
different flow rates. The pressure drop curve is normally a quadratic function of the fluid flow rate, which means
that the pressure drop increases with the square of the flow rate.
If the collector also operates at low flow rates, e.g. when the flow is laminar, a different relation must be used.
Figure 2: Typical pressure drop values for different SLHCs Figure 3: Typical pressure drop values for different SAHCs
Guide to the standard ISO 9806:2017
64
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Created by:
Stefan Mehnert
Dr. Korbinian Kramer
Konstantin Geimer
Max Reinhardt
Sven Fahr
Christoph Thoma
Fraunhofer Institute for Solar Energy Systems
Heidenhofstr.2
79110 Freiburg
Germany
www.collecortest.com
With contribution from:
Peter Kovac
Patrik Ollas
RISE Research Institutes of Sweden AB
Mäster Samuelsgatan 60, plan 9
111 21 Stockholm
Sweden
Layouted by:
Sumukha Dhathri
