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di Unificazione

Via Sannio, 220137 Milano, Italia

UNI EN 15316-4-7

MARZO 2009

Impianti di riscaldamento degli edifici

Metodo per il calcolo dei requisiti energetici e deirendimenti dellimpiantoParte 4-7: Sistemi di generazione per il riscaldamento degliambienti, sistemi di combustione a biomassa

Heating systems in buildingsMethod for calculation of system energy requirements and systemefficienciesPart 4-7: Space heating generation systems, biomass combustion systems

La norma fa parte di una serie di norme per il calcolo della presta-zione energetica e il rendimento energetico dei sistemi di riscalda-mento e produzione di acqua calda sanitaria.La norma definisce i dati di input, il metodo di calcolo e i risultati dioutput per i sistemi di combustione a biomassa a caricamentomanuale.

La norma si applica anche ai sistemi combinati per il riscaldamentoe la produzione di acqua calda sanitaria.I sistemi per la sola produzione di acqua calda sanitaria sono trat-tati nella UNI EN 15316-3-3.

TESTO INGLESE

La presente norma la versione ufficiale in lingua inglese dellanorma europea EN 15316-4-7 (edizione novembre 2008).

ICS 91.140.10

L icenza d ' uso concessa a UNIV E RS ITA' CE NTRO A TE NE O DOC.P OLO MONTE DA GO pe r l ' abbonamento anno 200 9 .

L i cenzad ' uso in te rno su pos taz i one s ingo la. R ip roduz i one v ie tata. E ' p ro ib i t o qual s ias i u t i l izzo in re te (LAN, in te rne t , e t c . . . )

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EUROPEAN STANDARD

NORME EUROPENNE

EUROPISCHE NORM

EN 15316-4-7

November 2008

ICS 91.140.10

English Version

Heating systems in buildings - Method for calculation of systemenergy requirements and system efficiencies - Part 4-7: Space

heating generation systems, biomass combustion systems

Systmes de chauffage dans les btiments - Mthode de

calcul des besoins nergtiques et des rendements dessystmes - Partie 4-7 : Systmes de gnration dechauffage des locaux, systmes de combustion de la

biomasse

Heizungsanlagen in Gebuden - Verfahren zur Berechnung

der Energieanforderungen und Nutzungsgrade der Anlagen- Teil 4-7: Wrmeerzeugung fr die Raumheizung,Biomasseverbrennungssystem

This European Standard was approved by CEN on 30 September 2008.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.

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.

EUROPEAN COMMITTEE FOR STANDARDIZATION

C O MIT E U R O P E N D E N O R MA L IS A T IO N

EUROPISCHES KOMITEE FR NORMUNG

Management Centre: rue de Stassart, 36 B-1050 Brussels

2008 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.

Ref. No. EN 15316-4-7:2008: E

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Contents

page

Foreword ..............................................................................................................................................................4

Introduction .........................................................................................................................................................6

1 Scope ......................................................................................................................................................6

2 Normative references ............................................................................................................................6

3 Terms, definitions, symbols and units ................................................................................................73.1 Terms and definitions ...........................................................................................................................73.2 Symbols and units .............................................................................................................................. 10

4 Principle of the method ...................................................................................................................... 114.1 Heat balance of the biomass combustion sub-system, including control of heat

generation ............................................................................................................................................ 114.1.1 Physical factors for biomass combustion sub-system ( biomass boiler ) taken into

account ................................................................................................................................................ 114.1.2 Calculation structure (input and output data) ................................................................................. 124.2 Generation sub-system basic energy balance ................................................................................ 134.3 Auxiliary energy .................................................................................................................................. 144.4 Recoverable, recovered and unrecoverable system thermal losses ............................................ 144.5 Calculation steps ................................................................................................................................ 154.6 Using net or gross calorific values ................................................................................................... 154.7 Boundaries between distribution and generation sub-system ...................................................... 15

5 Biomass combustion sub-system calculation ................................................................................ 166 Calculation method for boilers with automatic stocking................................................................ 16

7 Calculation method for boilers with stocking by hand ................................................................... 167.1 Available methodologies ................................................................................................................... 167.2 Operation periods ............................................................................................................................... 167.2.1 General ................................................................................................................................................. 167.2.2 Heating up operation cycle ................................................................................................................ 177.2.3 Boiler heating operation cycle .......................................................................................................... 177.2.4 Cooling down operation cycle ........................................................................................................... 177.2.5 Boiler non operation cycle ................................................................................................................. 187.3 Case specific boiler efficiency method ............................................................................................ 187.3.1 Principle of the method ...................................................................................................................... 187.3.2 Input data to the method .................................................................................................................... 197.3.3 Load of the boiler ................................................................................................................................ 207.3.4 Biomass boiler thermal losses .......................................................................................................... 217.3.5 Total auxiliary energy ......................................................................................................................... 237.3.6 Recoverable generation system thermal losses ............................................................................. 247.3.7 Fuel input ............................................................................................................................................. 257.3.8 Operating temperature of the biomass boiler .................................................................................. 257.4 Boiler cycling method ........................................................................................................................ 267.4.1 Principle of the method ...................................................................................................................... 267.4.2 Input data for the calculation method............................................................................................... 287.4.3 Load factor .......................................................................................................................................... 297.4.4 Specific thermal losses ...................................................................................................................... 297.4.5 Total thermal losses ........................................................................................................................... 337.4.6 Auxiliary energy .................................................................................................................................. 33

7.4.7 Recoverable system thermal losses ................................................................................................. 34

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7.4.8 Calculation procedure for a modulating biomass boiler (fan assisted) ........................................ 34

Annex A(informative) Additional formulas and default values for parametering the case specificboiler efficiency method ..................................................................................................................... 35

A.1 Information on the method ................................................................................................................. 35A.1.1 Basic assumptions and intended use ............................................................................................... 35

A.1.2 Known approximations ....................................................................................................................... 35A.2 Boiler efficiencies and stand-by heat losses.................................................................................... 35A.2.1 Default values for boiler efficiency at full load and intermediate load as a function of the

boiler power output ............................................................................................................................. 35A.2.2 Stand-by heat losses ........................................................................................................................... 36A.2.3 Correction factor taking into account variation of efficiency depending on boiler average

water temperature ............................................................................................................................... 37A.3 Auxiliary energy ................................................................................................................................... 38A.4 Recoverable boiler thermal losses .................................................................................................... 38A.4.1 Auxiliary energy ................................................................................................................................... 38A.4.2 Thermal losses (boiler envelope) ...................................................................................................... 39A.4.3 Default data according to boiler location .......................................................................................... 39

Annex B(informative) Additional formulas and default values for parametering the boiler cyclingmethod .................................................................................................................................................. 40

B.1 Information on the method ................................................................................................................. 40B.1.1 Basis assumptions and intended use ............................................................................................... 40B.1.2 Known approximations ....................................................................................................................... 40B.2 Default specific losses ........................................................................................................................ 40B.2.1 Default data for calculation of thermal losses through the chimney with boiler on .................... 40B.2.2 Default values for calculation of thermal losses through the boiler envelope ............................. 41B.2.3 Default values for calculation of thermal losses through the chimney with the boiler off .......... 42B.3 Default values for calculation of auxiliary energy ........................................................................... 43B.4 Additional default data for modulating burners ............................................................................... 43

Annex C(informative) Storage systems for biomass combustion systems .............................................. 45C.1 General ................................................................................................................................................. 45C.1.1 Accumulator storage system ............................................................................................................. 45C.1.2 Load balancing storage system ......................................................................................................... 45C.2 Sizing of storage systems for biomass combustion systems........................................................ 45C.2.1 Sizing of the volume of the accumulator storage tank .................................................................... 45C.2.2 Sizing of the volume of the load balancing tank .............................................................................. 46C.3 System thermal losses of storage systems...................................................................................... 46C.3.1 Thermal losses .................................................................................................................................... 46C.3.2 Auxiliary energy of the circulation pump .......................................................................................... 47

Annex D(informative) Calculation procedure with an example for biomass boiler with stocking byhand - Case specific boiler efficiency method ................................................................................. 48

Annex E(informative) Calculation procedure with an example for biomass boiler with stocking byhand (Cycling method) ........................................................................................................................ 50

Bibliography ...................................................................................................................................................... 53

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Foreword

This document (EN 15316-4-7:2008) has been prepared by Technical Committee CEN/TC 228 Heatingsystems in buildings, the secretariat of which is held by DS.

This European Standard shall be given the status of a national standard, either by publication of an identicaltext or by endorsement, at the latest by May 2009, and conflicting national standards shall be withdrawn at thelatest by May 2009.

This document has been prepared under a mandate given to CEN by the European Commission and theEuropean Free Trade Association (Mandate M/343), and supports essential requirements of EU Directive2002/91/EC on the energy performance of buildings (EPBD). It forms part of a series of standards aimed atEuropean harmonisation of the methodology for calculation of the energy performance of buildings. Anoverview of the whole set of standards is given in CEN/TR 15615.

The subjects covered by CEN/TC 228 are the following:

design of heating systems (water based, electrical etc.);

installation of heating systems;

commissioning of heating systems;

instructions for operation, maintenance and use of heating systems;

methods for calculation of the design heat loss and heat loads;

methods for calculation of the energy performance of heating systems.

Heating systems also include the effect of attached systems such as hot water production systems.

All these standards are systems standards, i.e. they are based on requirements addressed to the system as awhole and not dealing with requirements to the products within the system.

Where possible, reference is made to other European or International Standards, a.o. product standards.However, use of products complying with relevant product standards is no guarantee of compliance with thesystem requirements.

The requirements are mainly expressed as functional requirements, i.e. requirements dealing with the function

of the system and not specifying shape, material, dimensions or the like.

The guidelines describe ways to meet the requirements, but other ways to fulfil the functional requirementsmight be used if fulfilment can be proved.

Heating systems differ among the member countries due to climate, traditions and national regulations. Insome cases requirements are given as classes so national or individual needs may be accommodated.

In cases where the standards contradict with national regulations, the latter should be followed.

EN 15316 Heating systems in buildings Method for calculation of system energy requirements and systemefficienciesconsists of the following parts:

Part 1: General

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Part 2-1: Space heating emission systems

Part 2-3: Space heating distribution systems

Part 3-1: Domestic hot water systems, characterisation of needs (tapping requirements)

Part 3-2: Domestic hot water systems, distribution

Part 3-3: Domestic hot water systems, generation

Part 4-1: Space heating generation systems, combustion systems (boilers)

Part 4-2: Space heating generation systems, heat pump systems

Part 4-3: Heat generation systems, thermal solar systems

Part 4-4: Heat generation systems, building-integrated cogeneration systems

Part 4-5: Space heating generation systems, the performance and quality of district heating and large volumesystems

Part 4-6: Heat generation systems, photovoltaic systems

Part 4-7: Space heating generation systems, biomass combustion systems

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the followingcountries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, CzechRepublic, 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.

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Introduction

This European Standard presents methods for calculation of the additional energy requirements of a heatgeneration system by biomass combustion in order to meet the distribution and/or storage sub-systemdemand. The calculation is based on the performance characteristics of the products given in productstandards and on other characteristics required to evaluate the performance of the products as included in thesystem.

This method can be used for the following applications:

judging compliance with regulations expressed in terms of energy targets;

optimisation of the energy performance of a planned heat generation system, by applying the method toseveral possible options;

assessing the effect of possible energy conservation measures on an existing heat generation system, bycalculating the energy use with and without the energy conservation measures.

The user needs to refer to other European Standards or to national documents for input data and detailedcalculation procedures not provided by this European Standard.

1 Scope

This European Standard is part of a series of standards on the method for calculation of system energyrequirements and system efficiencies of space heating systems and domestic hot water systems.

The scope of this specific part is to standardise the:

required inputs;

calculation method;

resulting outputs,

for space heating generation by biomass combustion sub-systems (boilers) with stocking by hand, includingcontrol.

This European Standard is also intended for the case of generation for both domestic hot water production

and space heating. The case of generation only for domestic hot water production is treated in EN 15316-3-3.

2 Normative references

The following referenced documents are indispensable for the application of this document. For datedreferences, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including any amendments) applies.

EN 303-5, Heating boilers Part 5: Heating boilers for solid fuels, hand and automatically stocked, nominal

heat output of up to 300 kW Terminology, requirements, testing and marking

EN ISO 7345:1995, Thermal insulation Physical quantities and definitions (ISO 7345:1987)

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EN 15316-2-3, Heating systems in building Method for calculation of system energy requirements andsystem efficiencies Part 2-3: Space heating distribution systems

EN 15316-3-2, Heating systems in building Method for calculation of system energy requirements and

system efficiencies Part 3-2: Domestic hot water systems, distribution

EN 15316-3-3, Heating systems in building Method for calculation of system energy requirements andsystem efficiencies Part 3-3: Domestic hot water systems, generation

EN 15316-4-1:2005, Heating systems in building Method for calculation of system energy requirements andsystem efficiencies Part 4-1: Space heating generation systems, combustion systems (boilers)

3 Terms, definitions, symbols and units

3.1 Terms and definitions

For the purposes of this document, the terms and definitions given in EN ISO 7345:1995 and the followingapply.

3.1.1space heatingprocess of heat supply for thermal comfort

3.1.2domestic hot water heatingprocess of heat supply to raise the temperature of the cold water to the intended delivery temperature

3.1.3heated space

room or enclosure which for the purposes of the calculation is assumed to be heated to a given set-pointtemperature or set-point temperatures

3.1.4system thermal lossthermal loss from a technical building system for heating, cooling, domestic hot water, humidification,dehumidification, ventilation or lighting that does not contribute to the useful output of the system

NOTE Thermal energy recovered directly in the subsystem is not considered as a system thermal loss but as heatrecovery and is directly treated in the related system standard.

3.1.5auxiliary energyelectrical energy used by technical building systems for heating, cooling, ventilation and/or domestic hot water

to support energy transformation to satisfy energy needs

NOTE This includes energy for fans, pumps, electronics etc. Electrical energy input to the a ventilation system for airtransport and heat recovery is not considered as auxiliary energy, but as energy use for ventilation.

3.1.6heat recoveryheat generated by a technical building system or linked to a building use (e.g. domestic hot water) which isutilised directly in the related system to lower the heat input and which would otherwise be wasted (e.g.preheating of the combustion air by flue gas heat exchanger)

3.1.7total system thermal loss

total of the technical system thermal loss, including recoverable system thermal losses

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3.1.8recoverable system thermal losspart of the system thermal loss which can be recovered to lower either the energy need for heating or coolingor the energy use of the heating or cooling system

3.1.9recovered system thermal losspart of the recoverable system thermal loss which has been recovered to lower either the energy need forheating or cooling or the energy use of the heating or cooling system

3.1.10gross calorific valuequantity of heat released by a unit quantity of fuel, when it is burned completely with oxygen at a constantpressure equal to 101 320 Pa, and when the products of combustion are returned to ambient temperature

NOTE 1 This quantity includes the latent heat of condensation of any water vapour contained in the fuel and of the watervapour formed by the combustion of any hydrogen contained in the fuel.

NOTE 2 According to ISO 13602-2, the gross calorific value is preferred to the net calorific value.

NOTE 3 The net calorific value does not take into account the latent heat of condensation.

3.1.11net calorific valuegross calorific value minus latent heat of condensation of the water vapour in the products of combustion atambient temperature

3.1.12calculation stepdiscrete time interval for the calculation of the energy needs and uses for heating, cooling, humidification anddehumidification

NOTE Typical discrete time intervals are one hour, one day, one month or one heating and/or cooling season,operating modes, and bins.

3.1.13calculation periodperiod of time over which the calculation is performed

NOTE The calculation period can be divided into a number of calculation steps.

3.1.14external temperaturetemperature of external air

NOTE 1 For transmission heat transfer calculations, the radiant temperature of the external environment is supposedequal to the external air temperature; long-wave transmission to the sky is calculated separately.

NOTE 2 The measurement of external air temperature is defined in EN ISO 15927-1.

3.1.15boilergas, liquid or solid fuelled appliance designed to provide hot water for space heating. It may (but need not) bedesigned to provide domestic hot water heating as well

3.1.16combustion powerproduct of the fuel flow rate and the net calorific power of the fuel

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3.1.17condensing boilerboiler designed to make use of the latent heat released by condensation of water vapour in the combustionflue products. The boiler needs to allow the condensate to leave the heat exchanger in liquid form by way of a

condensate drain

NOTE Boilers not so designed, or without the means to remove the condensate in liquid form, are called non-condensing.

3.1.18modes of operationvarious modes in which the heating system can operate (set-point mode, cut-off mode, reduced mode, set-back mode, boost mode)

3.1.19modulating boilerboiler with the capability to vary continuously (from a set minimum to a set maximum) the fuel burning ratewhilst maintaining continuous burner firing

3.1.20accumulator (storage) systempart of the generation system tank which stores excess heat during operation time (resulting from thedifference between the boiler output and the actual heat input to the heating system)

3.1.21load balancing (storage) systempart of the generation system tank which improves the operation conditions during operation time (resulting inreducing the starting intervals and increasing the running time of automatic fired biomass boilers(see EN 15316-4-1)

3.1.22

biomass boilerbiomass fuelled appliance designed to provide heating medium (e.g. water, fluid) for space heating

3.1.23load factorratio between the time with the boiler ON and the total generator operation time

3.1.24operation cycletime period of the operation cycle of a boiler

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3.2 Symbols and units

For the purposes of this document, the following symbols and units (Table 1) and indices (Table 2) apply.

Table 1 Symbols and units

Symbol Name of quantity Unit

b temperature reduction factorc -

c coefficientc various

c specific heat capacity J/kgK orWh/kgK

a

Eenergy in general (except quantity of heat,mechanical work and auxiliary (electrical)energy

J orWh

a

e expenditure factor c -

f factorc -

H calorific valueJ/mass unit orWh/mass unit

b

H heat transfer coefficientc W/K

k factorc -

m mass kg

n exponent -

N number of items integer

P power in general including electrical power W

Q quantity of heatJ orWh

a

t time, period of times orh

a

V volume L

V' volume flowm/s orm/h

a

W auxiliary (electrical) energy, mechanical workJ orWh

a

loss factor %

load factor -

prefix for difference

efficiency factor %

Celsius temperature C

heat flow rate, thermal power Wa If seconds (s) is used as the unit of time, the unit for energy needs to be J;

If hours (h) is used as the unit of time, the unit for energy needs to be Wh.b Mass unit for fuel may be Stm, Nm or kg.

c Coefficients have dimensions; factors are dimensionless.

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Table 2 Indices

acc accumulator gen generationsubsystem

on on

aux auxiliary gnr generator op operation

avg average grs gross out output fromsubsystem

brm boiler room H heating P0 at zero load

cham chamber hup heating up Pint at intermediate load

ch chimney i, j, k indices Pn at nominal load

ci calculation step in input to subsystem Px at x load

cmb combustion ins insulation rbl recoverable

cod cooling down int intermediate ref reference

cor corrected / correction lob load balancing rvd recovered

ctr control ls losses s gross (calorific value)

dis distribution m mean sby in stand-by operation

em emission max maximum ta tank

fa factor mass massic test test conditions

fib fire bed min minimum W heating system water

fg flue gas net net w water

ge generator envelope off off z indices

The indices specifying symbols for sub-system energy balance quantities are in the followingorder:

the first index represents the use (H = space heating, W = domestic hot water etc.);

the second index represents the sub-system (gen = generation, dis = distribution etc.);

the third index represents the balance item (ls= losses, in = input, aux = auxiliary etc.).

Other indices may follow for more details (rvd = recovered, rbl = recoverable etc.).

4 Principle of the method

4.1 Heat balance of the biomass combustion sub-system, including control of heatgeneration

4.1.1 Physical factors for biomass combustion sub-system ( biomass boiler ) taken into account

The calculation method of the boiler takes into account heat losses and/or recovery due to the followingphysical factors:

heat losses to the chimney (or flue gas exhaust) during total time of boiler operation (running and stand-by);

heat losses through the boiler envelope during total time of boiler operation (running and stand-by);

auxiliary energy.

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The relevance of these effects on the energy requirements depends on:

type of the boiler;

location of the boiler;

part load ratio;

operating conditions (temperature, control etc.);

control strategy (on/off, modulating).

4.1.2 Calculation structure (input and output data)

The calculation method of this European Standard shall be based on the following:

heat demand of the distribution sub-system(s) for space heating, QH,dis,in, calculated according toEN 15316-2-3;

heat demand of the distribution sub-system(s) for domestic hot water, QW,dis,in, calculated according toEN 15316-3-2, where appropriate.

The performance of the boiler may be characterised by additional input data to take into account:

type and characteristics of the boiler;

boiler settings;

type of the boiler control system;

location of the boiler;

operating conditions;

heat requirement.

Based on these data, the following output data are determined by calculations according to this EuropeanStandard:

fuel heat requirement, EH,gen,in;

total generation thermal losses (flue gas and boiler envelope), QH,gen,ls;

recoverable generation thermal losses, QH,gen,ls,rbl;

generation auxiliary energy, WH,gen,aux.

Figure 1 shows the calculation inputs and outputs of the generation sub-system.

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Key

SUB generation sub-system balance boundary

HF heating fluid balance boundary (see Equation (1))

QH,gen,out generation sub-system heat output (input to distribution subsystem(s))

EH,gen,in generation sub-system fuel input (energyware)

WH,gen,aux generation sub-system total auxiliary energy

QH,gen,aux,rvd generation sub-system recovered auxiliary energy

QH,gen,ls generation sub-system total thermal losses

QH,gen,ls,rbl generation sub-system thermal losses recoverable for space heating

QH,gen,rbl,th generation sub-system thermal loss (thermal part) recoverable for space heating

QH,gen,rbl,aux generation sub-system recoverable auxiliary energy

QH,gen,nrbl,th generation sub-system thermal loss (thermal part) non recoverable

QH,gen,nrbl,aux generation sub-system non recoverable auxiliary energy

NOTE Figures shown are sample percentages.

Figure 1 General generation sub-system inputs, outputs and energy balance

4.2 Generation sub-system basic energy balance

The basic energy balance of the generation sub-system is given by:

lsH,gen,rvdaux,H,gen,H,gen,outinH,gen, QQQE += (1)

where

EH,gen,in heat requirement of the generation sub-system (fuel input);

QH,gen,out heat supplied to the distribution sub-systems (space heating);

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QH,gen,aux,rvdauxiliary energy recovered by the generation sub-system (e.g. pumps, burner fan);

QH,gen,ls total thermal losses of the generation sub-system (e.g. through the chimney, generatorenvelope).

NOTE 1 QH,gen,ls takes into account flue gas and boiler envelope losses, part of which may be recoverable for spaceheating according to location of the boiler. See A.4.2.

NOTE 2 If the boiler provides heat for space heating and domestic hot water, the index H needs to be replaced by HW. Inthe following (apart from Equation 2), only H is used for simplicity.

NOTE 3 Generally biomass boilers are not designed for controlling the emission part of heating systems.

If there is only one boiler, the heat output from the boiler equals the sum of heat input to the connecteddistribution systems:

+= j jin,dis,W,i iin,dis,H,outgen,HW, QQQ (2)

4.3 Auxiliary energy

Auxiliary energy is the energy, other than fuel, required for operation of the burner, the primary pump and anyequipment whose operation is related to operation of the heat generation sub-system. Auxiliary energy isaccounted for in the generation part as long as no transport energy from the auxiliary equipment is transferredto the distribution sub-system (example: zeropressure distribution array). Such auxiliary equipment can be(but need not be) an integral part of the boiler.

Auxiliary energy, normally in the form of electrical energy, may partially be recovered as heat for spaceheating or for the generation sub-system.

Examples of recoverable auxiliary energy:

electrical energy transmitted as heat to the water of the primary circuit;

part of the electrical energy for the boiler fan.

Example of non-recoverable auxiliary energy:

electrical energy for electric panel auxiliary circuits, if the boiler is installed outside the heated space.

4.4 Recoverable, recovered and unrecoverable system thermal losses

Not all of the calculated system thermal losses are necessarily lost. Some of the losses are recoverable andpart of the recoverable system thermal losses are actually recovered.

Example of recoverable system thermal losses:

thermal losses through the envelope of a boiler installed within the heated space.

Examples of non-recoverable system thermal losses:

thermal losses through the envelope of a boiler installed outside the heated space;

thermal losses (flue gas losses) through the chimney.

Recovery of system thermal losses to the heated space can be accounted for:

either as a reduction of total system thermal losses within the specific part (simplified method);

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or by taking into account recoverable system thermal losses as gains (holistic method) or as a reductionof the energy use according to EN 15603.

This European Standard allows both approaches.

Generation system thermal losses recovered by the generation sub-system are directly taken into account inthe generation performance.

EXAMPLE Combustion air preheating by flue gas losses.

4.5 Calculation steps

The objective of the calculation is to determine the energy input of the heating generation sub-system and thesystem losses for the entire calculation period (usually one year). This may be done in one of the following twodifferent ways:

by using average data for the entire calculation period and performing the calculations using average

values (usually annual data and values);

by dividing the calculation period into a number of calculation steps (e.g. months, weeks, bins, operationmodes as defined in EN ISO 13790), performing the calculations for each step using step-dependentvalues and sum up the results for all the steps over the calculation period;

For biomass boilers with stocking by hand, the calculation period shall be 24 h.

4.6 Using net or gross calorific values

Calculations described in Clause 7 may be performed according to net or gross calorific values. Allparameters and data shall be consistent with this option.

If the calculation of the boiler energy performance is performed according to data based on net calorific valuesHi, total losses QH,gen,ls,net, non recoverable thermal losses QH,gen,ls,th,nrbl,net and generation sub-systemenergyware EH,gen,in,net(i.e. fuel input for combustion systems) based on net calorific values may be convertedto values QH,gen,ls,grs, QH,gen,ls,th,nrbl,grsand EH,gen,in,grsbased on gross calorific values Hsby addition of the latentheat of condensation Qlataccording to the following:

i

isnetin,H,gen,lat

H

HHEQ

= (3)

latnetin,gen,H,grsin,gen,H, QEE += (4)

latnetls,gen,H,grsls,gen,H, QQQ += (5)

latnetnrbl,th,ls,gen,H,grsnrbl,th,ls,gen,H, QQQ += (6)

NOTE The latent heat of condensation Qlat varies extremely depending on the type of biomass fuel, place of origin,quality of storing etc. Therefore reference values should be given in a national annex.

4.7 Boundaries between distribution and generation sub-system

Boundaries between generation sub-system and distribution sub-system should be defined according to theprinciples described in 4.8 of EN 15316-4-1:2005.

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- boiler heating up tgnr,hup

- boiler heating operation tgnr,op

- boiler cooling down tgnr,cod

boiler in non operation tgnr,offconsisting of 2 sub-periods:

- boiler in fire bed operation tgnr,fib

- boiler in non operation tgnr,non

The total operation period tgnr,totof the boiler is given by:

tgnr,tot = tgnr,on+ tgnr,off (7)

NOTE Boiler in fire bed operation is only relevant for boilers with fan assistance.

7.2.2 Heating up operation cycle

The operation period for the heating up operation cycle tgnr,hupis influenced by:

quality of the biomass fuel applied;

quantity of the biomass fuel applied (according to the required quantity of the loaded biomass fuel).

7.2.3 Boiler heating operation cycle

The operation period for the heating operation cycle tgnr,opis influenced by:

quality of the biomass fuel applied;

quantity of the biomass fuel applied (according to the required quantity of the loaded biomass fuel);

intermediate load of the boiler.

The running time of the boiler in heating operation cycle, tgnr,op,dis calculated by:

davgoutgnrH

dindisH

dopgnr

Qt

,,,,

,,,

,,

= (h) (8)

where

tgnr,op,,d running time in heating operation cycle within a 24 h operation period in h;

QH,dis,in,d heat to be supplied to the distribution system within a 24 h operation period in kWh;

H,gnr,out,avg,daverage heat output from the biomass boiler within a 24 h operation period in kW.

7.2.4 Cooling down operation cycle

The operation period for the cooling down operation cycle tgnr,codis influenced by:

time when the operation cycle starts again;

mass of the relevant parts of the boiler;

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water content of the boiler;

heat loss of the envelope.

NOTE By a permanent operation cycle it is assumed, that the next heating up operation cycle starts immediately afterthe end of the cooling down operation cycle.

7.2.5 Boiler non operation cycle

Depending on the heat to be supplied to the distribution system during a 24 h operation period, two differenttypes of non operation cycles are to be considered:

boiler in fire bed operation cycle - operation period tgnr,fib

NOTE 1 In this case, the boiler temperature is the same as the regular boiler operating temperature.

boiler in non operation cycle - operation period tgnr,non

NOTE 2 In this case, the boiler temperature is the same as the ambience temperature (no heat loss).

7.3 Case specific boiler efficiency method

7.3.1 Principle of the method

This method is related to the test values according to relevant European Standards. If no values are available,default values are given in Annex A or in a national annex.

a) data are collected for three basic load factors or power outputs:

gnr,Pnefficiency at 100 % load;

gnr,Pintefficiency at intermediate load;

gnr,ls,P0heat losses at 0 % load.

b) efficiencies and heat losses data are corrected according to actual boiler operating conditions(temperature);

c) thermal losses at 100 % load, gnr,ls,Pn, and at intermediate load, gnr,ls,Pint, are calculated according to thetemperature corrected efficiencies;

d) calculation of thermal losses corresponding to the actual power output is made by linear or polynomialinterpolation between thermal losses determined for the three basic power outputs;

NOTE For the case specific boiler efficiency method, thermal losses and the load factor gnrare referred to boileroutput.

e) auxiliary energy is calculated taking into account the actual power output of the boiler;

f) recoverable boiler envelope thermal losses are calculated according to a tabulated fraction of stand-byheat losses and boiler location;

g) recoverable auxiliary energy is added to recoverable boiler envelope thermal losses to provide the totalrecoverable thermal losses.

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7.3.2 Input data to the method

7.3.2.1 Boiler data

The boiler is characterised by the following data:

Pn boiler output at full load;

gnr,Pn boiler efficiency at full load;

gnr,w,test,Pn boiler average water temperature at test conditions for full load;

fcorr,Pn correction factor for full-load efficiency;

Pint boiler output at intermediate load;

gnr,Pint boiler efficiency at intermediate load;

gnr,w,test,Pint boiler average water temperature at test conditions for intermediate load;

fcorr,Pint correction factor for intermediate load efficiency;

gnr,ls,P0 stand-by heat loss at test temperature difference gnr,test,P0;

gnr,test,P0 difference between mean boiler temperature and test room temperature at test conditions;

Paux,gnr,Pn power consumption of auxiliary devices at full load;

Paux,gnr,Pint power consumption of auxiliary devices at intermediate load;

Paux,gnr,P0 stand-by power consumption of auxiliary devices;

gnr,w,min minimum operating boiler temperature.

Data to characterise the boiler shall be taken from one of the following sources, listed in priority order:

a) product data from the manufacturer, if the boiler has been tested according to EN 303-5;

b) default data from the relevant national annex.

If no data according to a) or b) are available, default data are given in Annex A.

It shall be recorded whether or not the efficiency values include auxiliary energy recovery.

7.3.2.2 Actual operating conditions

Actual operating conditions are characterised by the following data:

QH,gnr,out heat output to the heat distribution sub-system(s);

gnr,w,m average water temperature in the boiler;

i,brm boiler room temperature;

bbrm temperature reduction factor depending on the location of the boiler.

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7.3.3 Load of the boiler

7.3.3.1 Boiler average power

Boiler average power H,gnr,outis given by:

totgnr

outgnrH

outgnrHt

Q

,

,,

,, = (9)

where

tgnr,tot is the total time of boiler operation.

7.3.3.2 Load ratio

The load ratio factorgnr

during the heating operation cycle is given by:

Pn

outgnrH

gnr

=

,, (10)

where

Pn is the nominal power output of the boiler (kW);

H,gnr,out is the average boiler output (kW).

The average boiler output is calculated by:

,

,

, ,

gnr cham

gnr out

gnr cham ref

=

(11)

where

gnr,cham is the heat output for each filling of the combustion chamber in kW. If the performance of theboiler has been tested according to relevant EN 303-5, it can be taken into account. If no valuesare available, default values should be given in the relevant national annex;

gnr,cham,ref is the reference combustion power in kW.

7.3.3.3 Boiler with double service (space heating and domestic hot water production)

During the heating season, the boiler may produce energy for the space heating installation and the domestichot water (double service). For a biomass boiler it is not necessary to consider a specific calculation of theoperating temperature.

NOTE The minimum operating temperature of biomass boilers are always higher than the required runningtemperature of the domestic hot water production.

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7.3.4 Biomass boiler thermal losses

7.3.4.1 Biomass boiler thermal loss calculation at full load

The efficiency at full load gnr,Pn is measured at a reference biomass boiler average water temperature

gnr,w,test,Pn. This efficiency has to be adjusted to the actual boiler average water temperature of the individualinstallation.

The temperature corrected efficiency at full load gnr,Pn,corris calculated by:

)( ,,,,,,,,, mwgnrPntestwgnrPncorrPngnrcorrPngnr f += (12)

where

gnr,Pn boiler efficiency at full load. If the performance of the boiler has been tested according to relevantEuropean Standards, it can be taken into account. If no values are available, default values aregiven in A.2.1 or in the relevant national annex;

fcorr,Pn correction factor taking into account variation of the full load efficiency as a function of the boileraverage water temperature. The value should be given in a national annex. In the absence ofnational values, default values are given in A.2.1. If the performance of the boiler has been testedaccording to relevant European Standards, it can be taken into account;

gnr,w,test,Pn boiler average water temperature at test conditions for full load (see A.2.3);

gnr,w,m average water temperature in the boiler, as a function of the specific operating conditions (see7.3.8).

In order to simplify the calculations, the efficiencies and heat losses determined at test conditions are adjustedto the actual boiler average water temperature. This is allowed, as it is physically correct to adjust theperformance at each load to the actual boiler average water temperature of each load.

The corrected biomass boiler thermal loss at full load gnr,ls,Pn,corris calculated by:

Pn

corrPngnr

corrPngnr

corrPnlsgnr

=

,,

,,

,,,

)100(

(13)

where

Pn boiler output at full load.

7.3.4.2 Biomass boiler thermal loss calculation at intermediate load

The efficiency at intermediate load gnr,Pint is measured at a reference boiler average water temperaturegnr,w,test,Pint. This efficiency has to be adjusted to the actual boiler average water temperature of the individualinstallation.

The temperature corrected efficiency at intermediate load gnr,Pint,corris calculated by:

)( ,,int,,,int,int,int,, mwgnrPtestwgnrPcorrPgnrcorrPgnr f += (14)

where

gnr,Pint boiler efficiency at intermediate load. If the performance of the boiler has been tested accordingto relevant European Standards, it can be taken into account. If no values are available, defaultvalues are given in A.2.1 or in the relevant national annex;

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fcorr,Pint correction factor taking into account variation of the efficiency as a function of the boiler averagewater temperature. The value should be given in a national annex. In the absence of nationalvalues, default values are given in A.2.1. If the performance of the boiler has been testedaccording to relevant European Standards, it can be taken into account;

gnr,w,test,Pint, boiler average water temperature at test conditions for intermediate load (see A.2.3);

gnr,w,m average water temperature in the boiler, as a function of the specific operating conditions (see7.3.8).

The intermediate load depends on the boiler type. Default values are given in A.1.

The corrected biomass boiler thermal loss at intermediate load gnr,ls,Pint,corris calculated by:

int

int,,

int,,

int,,,

)100(P

corrPgnr

corrPgnr

corrPlsgnr

=

(15)

where

Pint boiler output at intermediate load.

7.3.4.3 Biomass boiler thermal loss calculation at 0 % load

The boiler heat loss at 0 % load gnr,ls,P0is determined for a test temperature difference according to relevanttests. If no manufacturer or national annex data are available, default values are given in A.2.2.

The temperature corrected boiler thermal loss at 0 % load gnr,ls,P0,corris calculated by:

25,1

0,,

,,,0,,,0,,

=Ptestgnr

brmimwgnrPlsgnrcorrPlsgnr

(16)

where

gnr,ls,P0 heat loss at 0 % load at test temperature difference gnr,test,P0;

gnr,w,m average water temperature in the boiler, as a function of the specific operating conditions (see7.3.8);

i,brm indoor temperature of the boiler room. Default values are given in A.4.3;

gnr,test,P0 difference between mean boiler temperature and test room temperature at test conditions.

Default values are given in A.2.2.

7.3.4.4 Boiler thermal loss at specific load ratio gnrand power output Px

The specific load ratiognrof the boiler is calculated according to 7.3.3.

The actual power output Pxof the boiler is given by

gnrPnPx = (17)

If Pxis between 0 (gnr= 0) and Pint(intermediate load,gnr=int= Pint/Pn), the boiler thermal loss gnr,ls,Pxis calculated by:

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corrPlsgnrcorrPlsgnrcorrPlsgnr

P

PxPxlsgnr ,0,,,0,,int,,,

int

,, )( +

= (18)

If Pxis between Pintand Pn(full load,gnr= 1), the boiler thermal loss gnr,ls,Pxis calculated by:

corrPlsgnrcorrPlsgnrcorrPnlsgnr

PPn

PPxPxlsgnr int,,,int,,,,,,

int

int,, )( +

= (19)

gnr,ls,Px may also be calculated by 2nd

order polynomial interpolation. An equation for such interpolation isgiven in Annex B of EN 15316-4-1:2005.

The total boiler thermal loss Qgnr,ls during the considered time of operation tgnr,tot of the biomass boiler iscalculated by:

totgnrPxlsgnrlsgnr tQ ,,,, = (20)

7.3.4.5 Total generation thermal losses

The total generation sub-system thermal losses are the sum of the boiler thermal losses:

= lsgnr,lsgen,H, QQ (21)

7.3.5 Total auxiliary energy

The total auxiliary energy for a biomass boiler is given by:

totgnr,cioffaux,totgnr,Pxaux,auxgnr, ttPtPW += (22)

where

Paux,Px auxiliary power consumption corresponding to the actual power output Pxof the boiler;

Paux,off auxiliary power consumption when the boiler is not operating;

tci calculation interval;

tgnr,tot total time of boiler operation within the calculation interval.

The average auxiliary power consumption for each boiler Paux,Pxis calculated by linear interpolation, according

to the boiler loadgnr,between:

Paux,Pn auxiliary power consumption of the boiler at full load (gnr = 1);

Paux,Pint auxiliary power consumption of the boiler at intermediate load (gnr =int);

Paux,P0 auxiliary power consumption of the boiler at stand-by (gnr = 0);

If 0 gnr intthen Paux,Pxis given by:

( )0,int,int

0,, PauxPauxgnr

PauxPxaux PPPP +=

(23)

Ifint

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( )int,,int

int

int,,1

PauxPnaux

gnr

PauxPxaux PPPP

+=

(24)

The generation sub-system auxiliary energy WH,gen,auxis given by:

= auxgnr,auxgen,H, WW (25)

In the absence of detailed values, the power consumption of the auxiliary equipment can be calculatedaccording to A.3.

7.3.6 Recoverable generation system thermal losses

7.3.6.1 Auxiliary energy

For the recoverable auxiliary energy, a distinction is made between:

recoverable auxiliary energy transmitted to the heating medium (e.g. water). It is assumed, that theauxiliary energy transmitted to the energy vector is totally recovered;

recoverable auxiliary energy transmitted to the heated space.

The recovered auxiliary energy transmitted to the heating medium Qgnr,aux,rvdis calculated by:

auxrvdauxgnrrvdauxgnr fWQ ,,,, = (26)

where

frvd,aux

part of the auxiliary energy transmitted to the distribution sub-system. The value should be givenin a national annex. In the absence of national values, a default value is given in A.4.1.

Recovered auxiliary energy already taken into account in efficiency data shall not be calculated for recoveryagain. It has to be calculated for auxiliary energy need only.

NOTE Measured efficiency according to relevant standards usually includes the effect of heat recovered fromauxiliary energy for combustion air fan, control devices, primary pump (i.e. heat recovered is measured with the usefuloutput).

The recoverable auxiliary energy transmitted to the heated space Qgnr,aux,rblis calculated by:

auxrblbrmauxgnrrblauxgnr fbWQ ,,,, )1( = (27)

where

frbl,aux part of the auxiliary energy not transmitted to the distribution sub-system. The value should begiven in a national annex. In the absence of national values, a default value is given in A.4.1. Ifthe performance of the boiler has been certified, it can be taken into account;

bbrm temperature reduction factor depending on location of the boiler. The value of bbrm should begiven in a national annex. In the absence of national values, a default value is given in A.4.3.

7.3.6.2 Boiler thermal loss (boiler envelope)

Only the thermal losses through the boiler envelope are considered as recoverable. The thermal losses

through the boiler envelope are expressed as a fraction of the total stand-by heat losses.

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The recoverable thermal losses through the boiler envelope Qgnr,ls,env,rblare calculated by:

totgnrenvgnrbrmcorrPlsgnrrblenvlsgnr tfbQ ,,,0,,,,, )1( = (28)

where

fgnr,env thermal losses through the boiler envelope expressed as a fraction of the total stand-by heatlosses. The value of fgnr,envshould be given in a national annex. In the absence of national values,default values are given in A.4.2. If the performance of the boiler has been tested, it can be takeninto account;

bbrm temperature reduction factor depending on location of the boiler. The value of bbrm should begiven in a national annex. In the absence of national values, a default value is given in A.4.3;

tgnr,tot total time of boiler operation.

7.3.6.3 Total recoverable generation system thermal losses

The total recovered auxiliary energy QH,gen,aux,rvdis calculated by:

= rvdaux,gnr,rvdaux,gen,H, QQ (29)

The total recoverable generation system thermal losses QH,gen,ls,rblare calculated by:

+= rblaux,gnr,rblenv,ls,gnr,rblls,gen,H, QQQ (30)

7.3.7 Fuel input

Fuel heat input EH,gen,inis calculated according to Equation (1).

7.3.8 Operating temperature of the biomass boiler

The operating temperature of the boiler depends on:

type of control (taken into account by a correction factor);

technical limit of the boiler (taken into account by the temperature limitation);

temperature of the distribution sub-system connected to the generator.

The effect of control on the boiler is assumed to be a varying average temperature of the heat emitters.

Therefore two types of boiler control are taken into account:

constant water temperature;

variable water temperature depending on the operating range.

The operating temperature of the boiler is considered as

),max( ,,min,,,, mdisHwgnrmwgnr = (31)

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where

gnr,w,min minimum operating boiler temperature for each boiler. The values should be given in a nationalannex. In the absence of national values, default values are given in A.2.1;

H,dis,m temperature for heat distribution and storage system (if required) during the considered period.

7.4 Boiler cycling method

7.4.1 Principle of the method

7.4.1.1 General

This calculation method is based on the following principles.

7.4.1.2 Thermal losses of the boiler

Thermal losses of the boiler are taken into account separately for the five operation periods distinguished in7.2.

During the boiler heating up operation, the following thermal losses are taken into account:

heat of flue gas of the boiler according the intermediate load;

heat losses through the boiler envelope.

During the boiler heating operation, the following thermal losses are taken into account:

heat of flue gas of the boiler according the intermediate load;

heat losses through the boiler envelope at the running temperature.

During the boiler cooling down operation, the following thermal losses are taken into account:

no heat of flue gas of the boiler;


During the boiler fire bed operation, the following thermal losses are taken into account:

heat of flue gas of the boiler at fire bed load;


During the boiler non operation, the following thermal losses are taken into account:

no heat of flue gas of the boiler;

no heat losses through the boiler envelope.

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7.4.1.3 Auxiliary energy

Auxiliary energy is considered separately for appliances before and after the boiler:

Wbris the auxiliary energy required by components and devices that are installed before the combustionchamber following the energy path (typically boiler fan, see Figure 2);

NOTE 1 Typically these components and devices are running only when the boiler is on, i.e. during tgnr,on

Waf is the auxiliary energy required by components and devices that are installed after the combustionchamber following the energy path (typically primary pump, see Figure 2).

NOTE 2 Typically these components and devices are running during the entire operation period of the boiler i.e.during tgnr,tot= tgnr,on+ tgnr,off.

7.4.1.4 Recovered auxiliary energy

Part of the auxiliary energy will be recovered and considered in the energy balance. Calculation methods areavailable if detailed information can be used. Default formulas and default values are given in Annex A andAnnex B.

NOTE Auxiliary energy transformed into heat and emitted to the heated space may be considered separately and isadded to the recoverable heat losses.

7.4.1.5 Basic energy balance

The basic energy balance of the generation sub-system (biomass boiler) is:

envgnr,offch,onch,pmpbrcmboutgen,H, QQQQQQQ ++= (32)

NOTE This is the same as equation (1) where: envgnr,offch,onch,lsgen,H, QQQQ ++= , cmbingen,H, QE = and

pmpbrrvdaux,gen,H, QQQ += .

A schematic diagram of the energy balance of the generation sub-system is shown in Figure 2.

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Figure 2 Schematic energy balance of generation sub-system

7.4.2 Input data for the calculation method

7.4.2.1 Biomass boiler data

The biomass boiler is characterised by the following data:

cmb combustion power of the boiler, which is the reference power for Pch,on(either designor actualvalue);

cmb,min minimum combustion power of the boiler;

ref reference power for the heat loss factors Pch,offand Pgnr,env (usually ref= cmb);

Pch,on, Pch,off, Pgnr,env heat loss factors at test conditions;

Pch,on,min heat loss factor Pch,onat minimum combustion powercmb,min;

br electrical power consumption of auxiliary appliances (before the boiler) ;

kbr recovery factor ofbr;

br,min electrical power consumption of auxiliary appliances (before the boiler) at minimum combustion

power cmb,min;

af electrical power consumption of auxiliary appliances (after the boiler);kaf recovery factor ofaf;

gnr,w,m,test average boiler water temperature at test conditions for Pch,on;

ch,test flue gas temperature at test conditions for Pch,on;

i,brm,test temperature of test room for Pgnr,envand Pch,off;

gnr,env,test difference between average boiler temperature gnr,w,m,testand test room temperature i,brm,testattest conditions for Pgnr,envand Pch,off;

n, m, p exponents for the correction of heat loss factors.

NOTE Fan assisted biomass boilers operate in a modulating mode regularly.

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7.4.2.2 Actual operation conditions

Actual operation conditions are characterised by the following data:

Qgnr,out net heat output to the heat distribution sub-system(s);

gnr,w,m average water temperature in the boiler;

i,brm boiler room temperature;

kgnr,env reduction factor taking into account recovery of heat losses through the boiler envelope dependingon location of the boiler;

FC load factor.

NOTE All powers and the load factor FCrefer to boiler input (combustion power).

7.4.3 Load factor

The load factor FCis the ratio between the time with the boiler in operation and the total time of boileroperation:

, ,

, , ,

gnr on gnr on

gnr tot gnr on gnr off

t tFC

t t t= =

+ (33)

where

tgnr,tot total time of boiler operation (h);

tgnr,on time with the boiler ON (pre- and post-ventilation are not considered) (h);

NOTE 1 The boiler time in operation tgnr,on = tgnr,hup + tgnr,op (h);

tgnr,off time with the boiler OFF (h).

NOTE 2 The boiler time in non operation tgnr,off = tgnr,cod + tgnr,fib + tgnr,non (h).

The load factor shall either be calculated according to the actual energy, Qgnr,out, to be supplied by the boiler orbe measured (e.g. by time counters) on existing systems.

NOTE 3 The boiler heating up time tgnr,hupdepends on:

- total mass of the boiler ( metal + refractory + insulating materials )

- net calorific value of the fuel ( logwood ).

NOTE 4 The boiler cooling down time tgnr,coddepends on:

- total mass of the boiler ( metal + refractory + insulating materials )

- quality of the insulating materials of the boiler..

7.4.4 Specific thermal losses

7.4.4.1 General

Specific heat losses of the boiler are given at standard test conditions. Test conditions are identified by aquote.

Heat losses at test conditions are expressed as a percentage (Pch,on, Pch,offand Pgnr,ge) of a reference powerat test conditions.

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Test values shall be adjusted according to actual operation conditions. This applies both to standard testvalues and to field measurements.

7.4.4.2 Thermal losses through the chimney with the boiler on, Pch,on

The correction method for this loss factor takes into account the effects of:

average water temperature in the boiler;

load factor;

boiler settings (power and excess air changing the heat exchange efficiency).

Actual specific thermal losses through the chimney with the boiler on Pch,onare given by:

n

corrtestmwgnrmwgnronchonch FCfPP += )(' ,,,,,,, (34)

where

Pch,on are the heat losses through the chimney when the boiler is on at test conditions, in % (complementto 100 of the combustion efficiency). Pch,on is measured with the average water temperature

gnr,w,m,test. Heat losses through the chimney (flue gas loss) shall be expressed as a percentage of

the combustion powercmb.

For the design of new systems, Pch,on is the value declared by the manufacturer.For existing systems, Pch,on is given by a measure of combustion efficiency. Combustion efficiencymeasurement shall be realised according to national standards or recommendations. When

combustion efficiency is measured, the corresponding average water temperature gnr,w,m,test and

combustion powercmbshall be measured as well.

If no data is available, default values are given in B.2.1.The source of data shall be clearly stated in the calculation report.

gnr,w,m,testis the average water temperature in the boiler at test conditions in C (average of flow and returntemperature, usually flow temperature 80 C, return temperature 60 C).

For the design of new systems, gnr,w,m,test is the value declared by the manufacturer.

For existing systems, gnr,w,m,testis measured with combustion efficiency.

If no data is available, default values are given in B.2.1.The source of data shall be clearly stated in the calculation report;

gnr,w,m average water temperature in the boiler at actual conditions in C (average of flow and return

temperature);

fcorr correction factor for Pch,on(-). Default values for this factor are given in B.2.1.

n exponent for the load factor FC (-). Default values for this exponent are given in B.2.1.

NOTE 1 The factor FCn takes into account the reduction of losses with high intermittencies, due to a lower average

temperature of the flue gas (higher efficiency at start). An increasing value of n corresponds to a higher value of cmass,defined as the ratio between mass of the heat exchange surface between flue gas and water and nominal combustionpower of the boiler.

NOTE 2 Equation (34) takes into account variation in combustion efficiency depending on average temperature of waterin the generator by a linear approximation. The assumption is, that temperature difference between water and flue gas isapproximately constant (i.e. a 20 C increase of average water temperature causes a 20 C increase of flue gas

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temperature). A 22 C increase of flue gas temperature corresponds to 1 % increase of losses through the chimney, hencethe default value 0,045 for fcorr. Equation (34) does not include the effect of any latent heat recovery.

NOTE 3 Equation (34)does not take into account explicitly the effect of varying air/fuel ratio. The default constant 0,045

is valid for standard excess air (3 % O2in flue gas). For new systems, a correct setting is assumed. For existing systems,the air/fuel ratio contributes to Pch,on. If required, the constant 0,045 should be recalculated according to the actual air/fuelratio.

NOTE 4 Equation (34) does not take into account explicitly the effect of varying combustion power. If the combustionpower is significantly reduced, the procedure for existing systems shall be followed (i.e. Pch,onneeds to be measured).

7.4.4.3 Thermal losses through the boiler envelope, Pgnr,env

Actual specific thermal losses through the boiler envelope Pgnr,envare given by:

m

testbrmitestmwgnr

brmimwgnr

envgnrenvgnrenvgnr FCkPP

=

)(

)('

,,,,,

,,,

,,,

(35)

where

Pgnr,env heat losses through the boiler envelope at test conditions in %. Pgnr,envis expressed as a percentage

of the reference powerref(usually nominal combustion power of the boiler).

For the design of new systems, Pgnr,envis the value declared by the manufacturer.

If no data is available, default values are given in B.2.2.The source of data shall be clearly stated in the calculation report;

kgnr,env reduction factor taking into account the location of the boiler (-)Takes into account recovery of thermal losses as a reduction of total losses.

Default values are given in B.2.2;

i,brm,test temperature of the test room in C. Default values are given in B.2.2;

i,brm actual temperature of the room where the boiler is installed in C. Default values are given in B.2.2;

m exponent for the load factor FC (-). Default values for this exponent are given in B.2.2 depending onthe parameter cgnr, defined as the ratio between the total weight of the boiler (metal + refractory

materials + insulating materials) and the nominal combustion powercmbof the boiler.

NOTE 1 The factor FCm takes into account the reduction of heat losses through the boiler envelope if the boiler is

allowed to cool down during non operation cycle. In all cases m = 0 inhibits this correction.

NOTE 2 It is assumed that heat losses through the envelope are related to the temperature difference between the

average water temperature in the boiler and the temperature of the boiler surroundings. The relation is assumed to belinear (heat conduction through the boiler insulation).

NOTE 3 Pgnr,env can be determined as the difference between the combustion efficiency and the net efficiency of theboiler at test conditions (continuous operation).

Recovery of losses through the boiler envelope is taken into account as a reduction of total losses by thereduction factor kgnr,env.

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7.4.5 Total thermal losses

Thermal losses through the chimney (flue gas losses) with the boiler on are given by:

ongnrcmb

onch

onch tP

Q ,,

,100

= (39)

Thermal losses through the chimney with the boiler off are given by:

offgnrref

offch

offch tP

Q ,,

,100

= (40)

Thermal losses through the boiler envelope are given by:

)(100 ,,

,

, offgnrongnrref

envgnr

envgnr

ttP

Q += (41)

The total generation thermal losses are given by the sum of the total thermal losses of each biomass boiler:

++== )( envgnr,offch,onch,lsgnr,lsgen,H, QQQQQ (42)

7.4.6 Auxiliary energy

7.4.6.1 Specific auxiliary energy

For each auxiliary device of the biomass boiler, the following data shall be determined:

Electrical power consumption Pgnr,aux,i. Values can be:

declared by the manufacturer;

measured;

or default values calculated according to B.3.

The source of data shall be clearly stated in the calculation report.

Running time ton,aux,i, as a function of load factor FC where appropriate (i.e. burner auxiliaries).

Variable electrical power consumption should be approximated by an equivalent constant average electrical

power consumption.

7.4.6.2 Total auxiliary energy

The total auxiliary energy required by the boiler is given by:

= i iaux,on,iaux,gnr,auxgnr, tPW (43)

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7.4.7 Recoverable system thermal losses

7.4.7.1 Recoverable auxiliary energy

The recoverable auxiliary energy transmitted to the heated space Qgnr,aux,rblis calculated by:

auxrblbrmauxgnrrblauxgnr fbWQ ,,,, )1( = (44)

where

bbrm temperature reduction factor depending on location of the boiler. The value of bbrmshould be given ina national annex. In the absence of national values, default values are given in B.3.

frbl,aux part of the nominal electrical energy not transmitted to the distribution sub-system. The value shouldbe given in a national annex. In the absence of national values, a default value is given in B.3. If theperformance of the boiler has been certified, it can be taken into account.

7.4.7.2 Recoverable thermal loss (boiler envelope)

If not otherwise specified in a national annex, Qgnr,env,rbl= 0.

7.4.7.3 Total recoverable generation system thermal loss

The total recoverable generation system thermal losses QH,gen,ls,rbl are given by the sum of the recoverablesystem thermal loss of each biomass boiler:

+= rblaux,gnr,rblenv,gnr,rblls,gen,H, QQQ (45)

7.4.8 Calculation procedure for a modulating biomass boiler (fan assisted)

The calculation procedure and an example are given in Annex E.

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Annex A(informative)

Additional formulas and default values for parametering the casespecific boiler efficiency method

A.1 Information on the method

A.1.1 Basic assumptions and intended use

This methodology assumes that thermal losses and auxiliary power consumption are linearly dependant onboiler load in two ranges:

from 0 to intermediate load;

from intermediate load

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UNI 15316-4-7_2009