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.
NOTE   This document is extensively based on references to EN 12977-3:2008.

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

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

La présente spécification technique 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 CEN/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 de l’EN 12977-3 :2008.

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
Publication Date
06-Apr-2010
Withdrawal Date
03-Apr-2012
Current Stage
9960 - Withdrawal effective - Withdrawal
Start Date
04-Apr-2012
Completion Date
04-Apr-2012

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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

---------------------- 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.
---------------------- 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.
---------------------- 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
---------------------- 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.
---------------------- 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);
---------------------- 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

---------------------- 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.
---------------------- 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.
---------------------- 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.
---------------------- 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.

---------------------- 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

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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

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