SIST-TS CEN/TS 12977-4:2010

Thermal solar systems and components - Custom built systems - Part 4: Performance test methods for solar combistores

This Technical Specification specifies test methods for the performance characterization of stores which are intended for use in small custom built systems as specified in CEN/TS 12977-1. Stores tested according to this document are commonly used in solar combisystems. However, also the thermal performance of all other thermal stores with water as storage medium (e.g. for heat pump systems) can be assessed according to the test methods specified in this document. This document applies to combisstores with a nominal volume up to 3 000 l and without integrated burner.

Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil 4 Leistungsprüfung von Warmwasserspeichern für Solaranlagen zur Trinkwassererwärmung und Raumheizung

Die vorliegende Technische Spezifikation legt Prüfverfahren für die Beschreibung der Leistung von Speichern fest, die in kleinen kundenspezifisch gefertigten Anlagen nach den Festlegungen von CEN/TS 12977 1 zum Einsatz kommen sollen.
Die nach dem vorliegenden Dokument geprüften Speicher werden häufig in solaren Kombianlagen eingesetzt. Jedoch kann auch die thermische Leistung aller anderen Wärmespeicher, bei denen Wasser als Speicher-medium zum Einsatz kommt (z. B. Wärmepumpenanlagen), nach den in diesem Dokument festgelegten Prüf-verfahren bewertet werden.
Das vorliegende Dokument gilt für Kombispeicher mit einem Nennvolumen von bis zu 3 000 l ohne integrierten Brenner.
ANMERKUNG   Das vorliegende Dokument nimmt weitgehend Bezug auf EN 12977 3:2008.

Installations solaires thermiques et leurs composants - Installations personnalisées - Partie 4: Méthodes d'essai de performances des dispositifs de stockage mixtes pour des installations de chauffage solaires

Le présent document spécifie des méthodes d’essai pour la caractérisation des performances des dispositifs de stockage destinés à être utilisés dans de petites installations personnalisées, comme indiqué dans la prCEN/TS 12977 1.
Les dispositifs de stockage soumis à essai conformément au présent document sont couramment utilisés dans les installations solaires mixtes. Cependant, la performance thermique de tous les autres dispositifs de stockage thermiques utilisant de l’eau comme support de stockage (par exemple pour des installations de pompe à chaleur) peut également être évaluée conformément aux méthodes d’essai spécifiées dans le présent document.
Le présent document s’applique aux dispositifs de stockage mixtes ayant un volume nominal jusqu’à 3000 litres et sans brûleur intégré.
Remarque : La présente norme est principalement basée sur les références du prEN 12977-3.

Toplotni sončni sistemi in sestavni deli - Neserijsko izdelani sistemi - 4. del: Preskusne metode delovanja sončnih zbiralnikov

Ta tehnična specifikacija opredeljuje preskusne metode za označitev delovanja zbiralnikov, ki so namenjeni uporabi v majhnih neserijsko izdelanih sistemih, kot je opredeljeno v CEN/TS 12977-1. Zbiralniki, preskušeni v skladu s tem dokumentom, se pogosto uporabljajo v solarnih kombiniranih sistemih. Vendar pa je v skladu s preskusnimi metodami, opredeljenimi v tem dokumentu, mogoče oceniti tudi toplotno učinkovitost vseh drugih toplotnih zbiralnikov z vodo kot medijem shranjevanja (npr. za sisteme s toplotno črpalko). Ta dokument se uporablja za zbiralnike z nominalnim volumnom do 3 000 l in brez vgrajenega gorilca.

General Information

• Status: Withdrawn
• Public Enquiry End Date: 30-Jul-2008
• Publication Date: 21-Jul-2010
• Withdrawal Date: 03-Jun-2012
• ICS: 27.160 - Solar energy engineering
• ICS: 91.140.10 - Central heating systems
• ICS: 91.140.65 - Water heating equipment
• Technical Committee: TOP - Thermal insulation
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 26-Apr-2012
• Due Date: 19-May-2012
• Completion Date: 04-Jun-2012
• Ref Project: CEN/TS 12977-4:2010 - Thermal solar systems and components - Custom built systems - Part 4: Performance test methods for solar combistores

Relations

• Replaced By: SIST EN 12977-4:2012 - Thermal solar systems and components - Custom built systems - Part 4: Performance test methods for solar combistores
• Effective Date: 01-Jul-2012

Standards Content (Sample)

SLOVENSKI STANDARD
SIST-TS CEN/TS 12977-4:2010
01-september-2010
7RSORWQLVRQþQLVLVWHPLLQVHVWDYQLGHOL1HVHULMVNRL]GHODQLVLVWHPLGHO
3UHVNXVQHPHWRGHGHORYDQMDVRQþQLK]ELUDOQLNRY
Thermal solar systems and components - Custom built systems - Part 4: Performance
test methods for solar combistores
Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil
4 Leistungsprüfung von Warmwasserspeichern für Solaranlagen zur
Trinkwassererwärmung und Raumheizung
Installations solaires thermiques et leurs composants - Installations personnalisées -
Partie 4: Méthodes d'essai de performances des dispositifs de stockage mixtes pour des
installations de chauffage solaires
Ta slovenski standard je istoveten z: CEN/TS 12977-4:2010
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
91.140.10 Sistemi centralnega Central heating systems
ogrevanja
91.140.65 Oprema za ogrevanje vode Water heating equipment
SIST-TS CEN/TS 12977-4:2010 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST-TS CEN/TS 12977-4:2010

---------------------- Page: 2 ----------------------

SIST-TS CEN/TS 12977-4:2010


TECHNICAL SPECIFICATION
CEN/TS 12977-4

SPÉCIFICATION TECHNIQUE

TECHNISCHE SPEZIFIKATION
April 2010
ICS 27.160
English Version
Thermal solar systems and components - Custom built systems
- Part 4: Performance test methods for solar combistores
Installations solaires thermiques et leurs composants - Thermische Solaranlagen und ihre Bauteile -
Installations personnalisées - Partie 4: Méthodes d'essai de Kundenspezifisch gefertigte Anlagen - Teil 4:
performances des dispositifs de stockage mixtes pour des Leistungsprüfung von Warmwasserspeichern für
installations de chauffage solaires Solaranlagen zur Trinkwassererwärmung und
Raumheizung (Kombispeicher)
This Technical Specification (CEN/TS) was approved by CEN on 9 September 2008 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.






EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 12977-4:2010: E
worldwide for CEN national Members.

---------------------- Page: 3 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
Contents Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Terms and definitions .5
4 Symbols and abbreviations .5
5 Store classification .5
6 Laboratory store testing .6
6.1 Requirements on the testing stand .6
6.1.1 General .6
6.1.2 Measuring data and measuring procedure .6
6.2 Installation of the store .6
6.2.1 Mounting .6
6.2.2 Connection .6
6.3 Test and evaluation procedures .7
6.3.1 General .7
6.3.2 Test sequences .8
6.3.3 Data processing of the test sequences . 11
7 Test report . 13
7.1 General . 13
7.2 Description of the store . 13
7.3 Test results . 14
7.4 Parameters for the simulation . 15
Annex A (normative) Store model benchmark tests . 16
Annex B (normative) Verification of store test results . 17
Annex C (normative) Benchmarks for the parameter identification . 18
Annex D (informative) Requirements for the numerical store model . 19
Annex E (informative) Determination of hot water comfort . 20
E.1 General . 20
Bibliography . 21

Tables
Table 1 — Classification of combistores. 5
Table 2 — Flow rates and store inlet temperatures for Test CD . 9
Table 3 — Flow rates and store inlet temperatures for Test CI. 10
Table 4 — Flow rates and store inlet temperatures for Test DD . 10
Table 5 — Flow rates and store inlet temperatures for Test DI. 11
2

---------------------- Page: 4 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
Foreword
This document (CEN/TS 12977-4:2010) has been prepared by Technical Committee CEN/TC 312 “Thermal
sorla systems and components”, the secretariat of which is held by ELOT.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: Austria, Belgium, Bulgaria, Croatia, Cyprus,
Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.
3

---------------------- Page: 5 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
Introduction
The test methods for stores of solar heating systems as described in this document are required for the
determination of the thermal performance of small custom built systems for combined domestic hot water
preparation and space heating, so-called solar combisystems, as specified in CEN/TS 12977-1.
These test methods deliver parameters, which are needed for the simulation of the thermal behaviour of a
store being part of a small custom built system.
NOTE 1 With the test methods for stores given in EN 12897 only a few parameters are determined in order to
characterise the thermal behaviour of a store. These few parameters are not sufficient for the determination of the thermal
performance of small custom built systems as described in CEN/TS 12977-2.
NOTE 2 The already existing test methods for stores of conventional heating systems are not sufficient with regard to
thermal solar systems. This is due to the fact that the performance of thermal solar systems depends much more on the
thermal behaviour of the store (e.g. stratification, heat losses), as conventional systems do. Hence this separate document
for the performance characterisation of stores for solar heating systems is needed.
NOTE 3 For additional information about the test methods for the performance characterisation of stores see
EN 12977-3 and [1] in Bibliography.
4

---------------------- Page: 6 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
1 Scope
This Technical Specification specifies test methods for the performance characterization of stores which are
intended for use in small custom built systems as specified in CEN/TS 12977-1.
Stores tested according to this document are commonly used in solar combisystems. However, also the
thermal performance of all other thermal stores with water as storage medium (e.g. for heat pump systems)
can be assessed according to the test methods specified in this document.
This document applies to combisstores with a nominal volume up to 3 000 l and without integrated burner.

NOTE This document is extensively based on references to EN 12977-3:2008.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 12828, Heating systems in buildings — Design for water-based heating systems
EN 12977-3:2008, Thermal solar systems and components — Custom built systems — Part 3: Performance
test methods for solar water heater stores
EN ISO 9488:1999, Solar energy — Vocabulary (ISO 9488:1999)
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12977-3:2008 and
EN ISO 9488:1999 apply.
4 Symbols and abbreviations
For symbols and abbreviations refer to EN 12977-3.
5 Store classification
Solar combistores are classified by distinction between different charge and discharge modes. Five groups
are defined as shown in Table 1.
Table 1 — Classification of combistores
Group Charge mode Discharge mode
1 direct direct
2 indirect direct
3 direct indirect
4 indirect indirect
5 stores that cannot be assigned to groups 1 to 4
5

---------------------- Page: 7 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)

NOTE 1 All stores may have one or more additional electrical heating elements.
NOTE 2 Stores that can be charged or discharged directly and indirectly (e.g. a store of a space heating system with
an internal heat exchanger for the preparation of domestic hot water) can belong to more than one group. In this case the
appropriate test procedures or the assignment to one of the groups respectively, should be chosen depending on its mode
of operation.
6 Laboratory store testing
6.1 Requirements on the testing stand
6.1.1 General
The hot water store shall be tested separately from the whole solar system on a store testing stand.
The testing stand configuration shall be determined by the classification of the combistores as described in
Clause 5.
An example of a representative hydraulic testing stand configuration is shown in EN 12977-3:2008, Figure 1
and Figure 2. An appropriate test facility consists of two charge loops as shown in EN 12977-3:2008, Figure 1
and two discharge loops as shown in EN 12977-3:2008, Figure 2.
6.1.2 Measuring data and measuring procedure
The requirements specified in EN 12977-3:2008, 6.1.2 shall be fulfilled.
6.2 Installation of the store
6.2.1 Mounting
The store shall be mounted on the testing stand according to the manufacturer's instructions.
The temperature sensors used for measuring the inlet and outlet temperatures of the fluid used for charging
and discharging the storage device, shall be placed as near as possible at least 200 mm to the inlet and outlet
connections of the storage device. The installation of the temperature sensors inside the pipes shall be done
according to approved methods of measuring temperatures.
If there is/are more than one pair of charging and/or discharging inlet or outlet connections, then only one may
be connected to the testing stand (at the same time) while the other(s) shall be closed.
The pipes between the store and the temperature sensors shall be insulated according to EN 12828.
6.2.2 Connection
The way of connecting the storage device to the testing stand depends on the purpose of the thermal tests
which shall be performed. Detailed instructions are given in the clauses where the thermal tests are described.
Connections of the store which do not lead to the charge or discharge circuit of the testing stand shall be
closed, and not connected heat exchangers shall be filled up with water. All closed connections shall be
insulated in the same way as the store.
Since fluid in closed heat exchangers expands with increasing temperature, a pressure relief valve shall be
mounted.
6

---------------------- Page: 8 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
NOTE The performance of a solar heating system depends on the individual installation and actual boundary
conditions. With regard to the heat losses of the store besides deficits in the thermal insulation, badly designed
connections can increase the heat loss capacity rate of the store due to natural convection that occurs internally in the
pipe. In order to avoid this effect the connections of the pipes should be designed in such a way that no natural convection
inside the pipe occurs. This can e.g. be achieved if the pipe is directly going downwards after leaving the store or by using
a heat trap siphon.
6.3 Test and evaluation procedures
6.3.1 General
The aim of store testing as specified in this document is the determination of parameters required for the
detailed description of the thermal behaviour of a hot water combistore. Therefore, a mathematical computer
model for the store is necessary. The basic requirements on suitable models are specified in Annex A and
Annex B.
The following parameters shall be known for the simulation of a store being part of a solar system:
a) stored water:
1) height;
2) effective volume respectively effective thermal capacity;
3) heights of the inlet and outlet connections;
4) heat loss capacity rate of the entire store;
5) if the insulation varies for different heights of the store, the distribution of the heat loss capacity rate
should be determined for the different parts of the store;
6) a parameter describing the degradation of thermal stratification during stand-by;
NOTE 1 One possible way to describe this effect in a store model is the use of a vertical thermal conduction. In this
case the corresponding parameter is an effective vertical thermal conductivity.
7) a parameter describing the characteristic of thermal stratification during direct discharge;
NOTE 2 An additional parameter may be used to describe the influence of different draw-off flow rates on the thermal
stratification inside the store, if this effect is relevant.
8) positions of the temperature sensors (e.g. the sensors of the collector loop and auxiliary heater
control);
b) heat exchangers:
1) heights of the inlet and outlet connections;
2) volume;
3) heat transfer capacity rate as a function of temperature;
4) information on the capacity in respect of stratified charging;
NOTE 3 The capacity in respect of stratified charging can be determined from the design of the heat exchanger as well
as from the course in time of the heat exchanger inlet and outlet temperatures.
5) heat loss rate from the heat exchanger to the ambient (necessary only for mantled heat exchangers
and external heat exchangers);
7

---------------------- Page: 9 ----------------------

SIST-TS CEN/TS 12977-4:2010
CEN/TS 12977-4:2010 (E)
c) electrical auxiliary heat source:
1) position in the store;
2) axis direction of heating element (horizontal or vertical). If the auxiliary heater is installed in a vertical
way, also its length is required;
3) effectivity that characterises the fraction of the thermal converted electric power which is actually
transferred inside the store.
NOTE 4 Badly designed electrical auxiliary heaters may cause significant heat losses during operation. In this case the
electrical power supplied to the heater is not equal to the thermal energy input to the store.
The following clauses describe the way, how the listed parameters can be determined. Therefore, specific test
sequences are
...

SLOVENSKI STANDARD
kSIST-TS prCEN/TS 12977-4:2008
01-julij-2008
7RSORWQLVRQþQLVLVWHPLLQVHVWDYQLGHOL1HVHULMVNRL]GHODQLVLVWHPLGHO
3UHVNXVQHPHWRGHGHORYDQMDVRQþQLK]ELUDOQLNRY
Thermal solar systems and components - Custom built systems - Part 4: Performance
test methods for solar combistores
Thermische Solaranlagen und ihre Bauteile - Kundenspezifisch gefertigte Anlagen - Teil
4 Leistungsprüfung von Warmwasserspeichern für Solaranlagen zur
Trinkwassererwärmung und Raumheizung
Installations solaires thermiques et leurs composants - Installations personnalisées -
Partie 4: Méthodes d'essai de performances des dispositifs de stockage mixtes pour des
installations de chauffage solaires
Ta slovenski standard je istoveten z: prCEN/TS 12977-4
ICS:
27.160 6RQþQDHQHUJLMD Solar energy engineering
kSIST-TS prCEN/TS 12977-4:2008 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

TECHNICAL SPECIFICATION
FINAL DRAFT
prCEN/TS 12977-4
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
May 2008
ICS 27.160

English Version
Thermal solar systems and components - Custom built systems
- Part 4: Performance test methods for solar combistores
Installations solaires thermiques et leurs composants - Thermische Solaranlagen und ihre Bauteile -
Installations personnalisées - Partie 4: Méthodes d'essai de Kundenspezifisch gefertigte Anlagen - Teil 4
performances des dispositifs de stockage mixtes pour des Leistungsprüfung von Warmwasserspeichern für
installations de chauffage solaires Solaranlagen zur Trinkwassererwärmung und
Raumheizung
This draft Technical Specification is submitted to CEN members for Technical Committee Approval. It has been drawn up by the Technical
Committee CEN/TC 312.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,
Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Warning : This document is not a Technical Specification. It is distributed for review and comments. It is subject to change without notice
and shall not be referred to as a Technical Specification.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2008 CEN All rights of exploitation in any form and by any means reserved Ref. No. prCEN/TS 12977-4:2008: E
worldwide for CEN national Members.

---------------------- Page: 2 ----------------------

prCEN/TS 12977-4:2008 (E)
Contents Page
Foreword.3
Introduction .4
1 Scope.5
2 Normative references.5
3 Terms and definitions .5
4 Symbols and abbreviations .5
5 Store classification.6
6 Laboratory store testing.6
6.1 Requirements on the testing stand.6
6.1.1 General.6
6.1.2 Measuring data and measuring procedure .6
6.2 Installation of the store .6
6.2.1 Mounting.6
6.2.2 Connection.7
6.3 Test and evaluation procedures.7
6.3.1 Test sequences.8
6.3.2 Data processing of the test sequences.12
7 Test report.13
7.1 General.13
7.2 Description of the store .14
7.3 Test results.15
7.4 Parameters for the simulation.16
Annex A (normative) Store model benchmark tests .17
Annex B (normative) Verification of store test results.18
Annex C (normative) Benchmarks for the parameter identification .19
Annex D (informative) Requirements for the numerical store model .20
Annex E (informative) Determination of hot water comfort .21
E.1 General.21
Bibliography .22

2

---------------------- Page: 3 ----------------------

prCEN/TS 12977-4:2008 (E)
Foreword
This document (prCEN/TS 12977-4:2008) has been prepared by Technical Committee CEN/TC 312 “Thermal
solar systems and components”, the secretariat of which is held by ELOT.
This document is currently submitted to the Technical Committee Approval.
3

---------------------- Page: 4 ----------------------

prCEN/TS 12977-4:2008 (E)

Introduction
The test methods for stores of solar heating systems as described in this document are required for the
determination of the thermal performance of small custom built systems for combined domestic hot water
preparation and space heating, so-called solar combisystems, as specified in prCEN/TS 12977-1.
These test methods deliver parameters, which are needed for the simulation of the thermal behaviour of a
store being part of a small custom built system.
NOTE 1 With the test methods for stores given in EN 12897 only a few parameters are determined in order to characterise
the thermal behaviour of a store. These few parameters are not sufficient for the determination of the thermal performance
of small custom built systems as described in prCEN/TS 12977-2.
NOTE 2 The already existing test methods for stores of conventional heating systems are not sufficient with regard to
thermal solar systems. This is due to the fact that the performance of thermal solar systems depends much more on the
thermal behaviour of the store (e. g. stratification, heat losses), as conventional systems do. Hence this separate
document for the performance characterisation of stores for solar heating systems is needed.
NOTE 3 For additional information about the test methods for the performance characterisation of stores see prEN 12977-
3 and [1] in Bibliography.
4

---------------------- Page: 5 ----------------------

prCEN/TS 12977-4:2008 (E)

1 Scope
This document specifies test methods for the performance characterization of stores which are intended for
use in small custom built systems as specified in prCEN/TS 12977-1.
Stores tested according to this document are commonly used in solar combisystems. However, also the
thermal performance of all other thermal stores with water as storage medium (e.g. for heat pump systems)
can be assessed according to the test methods specified in this document.
This document applies to combisstores with a nominal volume up to 3000 litres and without integrated burner.

Remark: This standard is extensively based on references to prEN 12977-3.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 12828 Heating systems in buildings — Design for water-based heating systems
prCEN/TS 12977-1 Thermal solar systems and components — Custom built systems — Part 1:
General requirements for solar water heaters and combisystems
prEN 12977-3:2008 Thermal solar systems and components – Custom built systems – Part 3:
Performance test methods for solar water heater stores
EN ISO 9488:1999 Solar energy – Vocabulary (ISO 9488:1999)

3 Terms and definitions
For the purposes of this document, the terms and definitions given in prEN 12977-3:2008 and
EN ISO 9488:1999 apply.
4 Symbols and abbreviations
For symbols and abbreviations refer to prEN 12977-3:2008.
5

---------------------- Page: 6 ----------------------

prCEN/TS 12977-4:2008 (E)

5 Store classification
Solar combistores are classified by distinction between different charge and discharge modes. Five groups
are defined as shown in Table 1.
Table 1 — Classification of combistores
Group Charge mode Discharge mode
1 direct direct
2 indirect direct
3 direct indirect
4 indirect indirect
5 stores that cannot be assigned to groups 1 to 4

NOTE 1  All stores may have one or more additional electrical heating elements.
NOTE 2 Stores that can be charged or discharged directly and indirectly (e. g. a store of a space heating system with
an internal heat exchanger for the preparation of domestic hot water) can belong to more than one group. In this case the
appropriate test procedures or the assignment to one of the groups respectively, shall be chosen depending on its mode
of operation.
6 Laboratory store testing
6.1 Requirements on the testing stand
6.1.1 General
The hot water store shall be tested separately from the whole solar system on a store testing stand.
The testing stand configuration shall be determined by the classification of the combistores as described in
clause 5.
An example of a representative hydraulic testing stand configuration is shown in prEN 12977-3:2008, Figure 1
and Figure 2. An appropriate test facility consists of two charge loops as shown in prEN 12977-3:2008,
Figure 1 and two discharge loops as shown in prEN 12977-3:2008, Figure 2.
6.1.2 Measuring data and measuring procedure
The requirements specified in prEN 12977-3:2008, chapter 6.1.2 shall be fulfilled.

6.2 Installation of the store
6.2.1 Mounting
The store shall be mounted on the testing stand according to the manufacturer's instructions.
6

---------------------- Page: 7 ----------------------

prCEN/TS 12977-4:2008 (E)
The temperature sensors used for measuring the inlet and outlet temperatures of the fluid used for charging
and discharging the storage device, shall be placed as near as possible at least 200 mm to the inlet and outlet
connections of the storage device. The installation of the temperature sensors inside the pipes shall be done
according to approved methods of measuring temperatures.
If there is/are more than one pair of charging and/or discharging inlet or outlet connections, then only one may
be connected to the testing stand (at the same time) while the other(s) shall be closed.
The pipes between the store and the temperature sensors shall be insulated according to prEN 12828.
6.2.2 Connection
The way of connecting the storage device to the testing stand depends on the purpose of the thermal tests
which shall be performed. Detailed instructions are given in the clauses where the thermal tests are described.
Connections of the store which do not lead to the charge or discharge circuit of the testing stand shall be
closed, and not connected heat exchangers shall be filled up with water. All closed connections shall be
insulated in the same way as the store.
Since fluid in closed heat exchangers expands with increasing temperature, a pressure relief valve shall be
mounted.

NOTE The performance of a solar heating system depends on the individual installation and actual boundary
conditions. With regard to the heat losses of the store besides deficits in the thermal insulation, badly designed
connections can increase the heat loss capacity rate of the store due to natural convection that occurs internally in the
pipe. In order to avoid this effect the connections of the pipes should be designed in such a way that no natural convection
inside the pipe occurs. This can e. g. be achieved if the pipe is directly going downwards after leaving the store or by using
a heat trap siphon.

6.3 Test and evaluation procedures
The aim of store testing as specified in this document is the determination of parameters required for the
detailed description of the thermal behaviour of a hot water combistore. Therefore, a mathematical computer
model for the store is necessary. The basic requirements on suitable models are specified in Annex A and
Annex B.
The following parameters shall be known for the simulation of a store being part of a solar system:
a) Stored water
 Height
 Effective volume respectively effective thermal capacity
 Heights of the inlet and outlet connections
 Heat loss capacity rate of the entire store
 If the insulation varies for different heights of the store, the distribution of the heat loss capacity rate
should be determined for the different parts of the store
 A parameter describing the degradation of thermal stratification during stand-by
7

---------------------- Page: 8 ----------------------

prCEN/TS 12977-4:2008 (E)
NOTE 1 One possible way to describe this effect in a store model is the use of a vertical thermal conduction. In this
case the corresponding parameter is an effective vertical thermal conductivity.
 A parameter describing the characteristic of thermal stratification during direct discharge.
NOTE 2 An additional parameter may be used to describe the influence of different draw-off flow rates on the thermal
stratification inside the store, if this effect is relevant.
 Positions of the temperature sensors (e. g. the sensors of the collector loop and auxiliary heater
control)
b) Heat exchangers
 Heights of the inlet and outlet connections
 Volume
 Heat transfer capacity rate as a function of temperature
 Information on the capacity in respect of stratified charging,
NOTE 3 The capacity in respect of stratified charging can be determined from the design of the heat exchanger as well
as from the course in time of the heat exchanger inlet and outlet temperatures.
 Heat loss rate from the heat exchanger to the ambient (necessary only for mantled heat exchangers
and external heat exchangers)
c) Electrical auxiliary heat source
 Position in the store
 Axis direction of heating element (horizontal or vertical). If the auxiliary heater is installed in a vertical
way, also its length is required
 Effectivity that characterises the fraction of the thermal converted electric power which is actually
transferred inside the store
NOTE 4 Badly designed electrical auxiliary heaters may cause significant heat losses during operation. In this case the
electrical power supplied to the heater is not equal to the thermal energy input to the store.
The following clauses describe the way, how the listed parameters can be determined. Therefore, specific test
sequences are necessary. The test sequences indicated by letters (e. g. TEST CD) can be subdivided into
phases indicated by a number (e. g. CD1 – conditioning). Between the end of one phase and the start of the
following phase, a maximum stand-by time of 10 min is allowed. During this stand-by time the ambient
temperature only shall be measured and recorded.
NOTE 5 One essential point of the described methods is, that measurements inside the store are avoided.
NOTE 6 The determination of all above listed store parameters is possible only according to the method described
under 6.3.1 and the data processing of the test sequences described under 6.3.2. For fur
...