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CEN/TC 228

Date:  2004-12

TC 228 WI 00228 027

CEN/TC 228

Secretariat:   DS

Heating systems in buildings — Method for calculation of system energy requirements and system efficiencies — Part 2.2.5 Space heating generation systems, the performance of quality district heating and large volume systems

Einführendes Element — Haupt-Element — Ergänzendes Element

Élément introductif — Élément central — Élément complémentaire

ICS:  

Descriptors:  



Contents Page

Foreword 3

Introduction 3

1 Scope 3

2 Normative References 5

3 Terms and Definitions 5

3.1 Definitions 5

3.2 Symbols and units 6

4 Principle of the Method 7

4.1 Part of district heating situated outside the building - Primary Energy Factor 7

4.2 Energy Requirements of the Dwelling Substations 8

5 District heating system calculation 9

5.1 Primary Energy Factor 9

5.1.1 Calculation based on measurements 9

5.1.2 Calculation from Planning Data 10

5.1.3 Auxiliary Energy Consumption 12

5.1.4 Recoverable Heat Losses 12

5.1.5 Calculation Period 12

5.2 Energy Requirements of the dwelling substations 12

5.2.1 Heat Losses of the dwelling substation 13

5.2.2 Auxiliary Energy Consumption 14

5.2.3 Recoverable Heat Losses 14

Annex A
(informative)
100
Examples 15


A.1 Typical Situation of Public Utilities of a City 15

A.2 Typical Situation of an Industrial Power Plant Supplying Internal Requirements and a City Nearby 16

A.3 Typical Situation of Small Heat and Power Cogeneration Systems 16

Annex B
(informative)
200
Primary energy factor, dwelling substation performance 18


Foreword

This document TC 228 WI 00228 027 has been prepared by Technical Committee CEN/TC 228 “Heating systems in buildings”, the secretariat of which is held by DS.

This document is currently submitted to the CEN Enquiry.

Introduction

All the standards of CEN TC 228 are system standards. This standard presents a method for the cal­cu­lation of the energy performance of district heating systems and dwelling stations. The results of the calculation are the primary energy factor of the specific district heating system and the heat losses of the dwelling stations. The method is applicable for all kinds of heat sources including heat and power cogeneration. It is independent from the use which is made of the heat including subsequent gene­ra­tion of cooling energy in the building. It may be applied in the same way for district cooling based on cogeneration or the use of lake or sea water.

The calculation is based on the performance data of a district heating system respectively a dwelling station, which can be calculated or measured according to this standard and other European stan­dards cited herein.

This method may be used for the following applications:


  • judging compliance with regulations expressed in terms of energy targets,

  • optimisation of the energy performance of planned district heating and dwelling stations by varying the input parameters,

  • assessing the effect of possible energy conservation measures on existing systems by chan­ging the method of operation or replacing parts of the system.

The user shall refer to other European standards, European directives, and to national documents for input data and detailed cal­culation procedures, which are not provided by this standard.

Only the calculation method and input parameters are normative. All other values necessary to parameter this method should be put in a national annex.


1Scope


This standard is part of the method for calculation of system energy requirements and system effi­cien­cies prEN 14335.

The scope of this specific part is to standardize the method of assessing the energy performance of district heating and cooling systems and to define



  • the system borders,

  • the required inputs,

  • the calculation method, and

  • the resulting outputs.

The method applies to district heating and cooling systems and any other kind of combined production for space heating and/or cooling and/or domestic water heating purposes.

2Normative References


This standard incorporates by dated or undated reference provisions from other publications. These normative references are cited in the appropriate places in the text and the publications are listed hereafter. For dated references subsequent amendments to or revisions of any of these publications apply to this standard only if incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to applies.

Directive 2004/8/EC on the promotion of cogeneration based on a useful heat demand in the internal energy market and amending Directive 92/42 EEC

prEN ISO 12241

Thermal insulation for building equipment and industrial installations

prEN 14335

Heating systems in buildings - Method for calculation of system energy requirements and system efficiencies

3Terms and Definitions

3.1Definitions


cogeneration

Simultaneous generation in one process of thermal energy and electrical and/or mechanical energy.



delivered energy

energy supplied through the system boundary to satisfy the energy requirement


net energy

energy supplied by the energy systems to provide the required services. Recovered losses or gains are taken into account



primary energy

energy that has not been subjected to any conversion or transformation process (e.g. oil in the oil fields).

Primary energy may be either resource energy or renewable energy or a combination of both.
primary energy factor

primary energy divided by delivered energy, where the primary energy is that required to supply one unit of delivered energy of the same type, taking account of the energy required for extraction, processing, storage, transport, generation, transformation, transmission, distribution, and any other operations necessary for delivery to the building in which the delivered energy will be used. Primary energy may be resource energy, or renewable energy, or a combination of both. Delivery operations may call for energy of various types (e.g., electricity, oil), and each of those shall also be measured as primary energy using the appropriate factor.



primary resource energy factor

resource energy divided by delivered energy, where the resource energy is that required to supply one unit of delivered energy, taking account of the resource energy required for extraction, processing, storage, transport, generation, transformation, transmission, distribution, and any other operations necessary for delivery to the building in which the delivered energy will be used. Any renewable energy component of the delivered energy is ignored. Delivery operations may call for energy of various types (e.g. electricity, oil), and each of those should also be measured as resource energy using the appropriate primary resource energy factor.



recoverable losses

part of the loss from the heating, ventilation, cooling, lighting and hot water systems which may be recovered to lower the energy requirements.



recovered loss

part of the recoverable loss which has been recovered to lower the energy requirements.



renewable energy

energy taken from a source which is not depleted by extraction (e.g., solar, wind) .



resource energy

energy taken from a source which is depleted by extraction (e.g., fossil fuels).


3.2Symbols and units


Table 1 — Symbols and units

B

Coefficient depending on the type of the dwelling station and its insulation level.

D

Coefficient

f

factor.

H

Heat exchange coefficient

Q,i

Quantity of energy

W

Cogenerated electricity

η

Efficiency

σ

Relation of power and heat production of the cogeneration appliance.

β

Relation of heat produced by the cogeneration appliance to the total heat production.



Temperature



heat power

Table 2 — Indices

amb ambiant

F fuel

i, ,j indices

CHP combined heat + power







DH district heating system

Gen Generation

p primary

DS dwelling substation







elt electrical

HP heating plant

S secondary

ext external

HN heating network





4Principle of the Method


The performance of a district heating system is evaluated by dividing the district heating system into two parts (cf. figure 1):

The outside part is rated by the balance of primary energy consumption of heat generation and heat distribution of the district heating system.

T
he inside part is rated by the additional energy requirements of the dwelling substation. Thus the substation can be con­si­dered to replace the heat generator within the building.



Figure 1 — Systematic of Rating the Performance of District Heating Systems

4.1Part of district heating situated outside the building - Primary Energy Factor


The performance of a district heating system can be rated by evaluating the primary energy factor fP,DH of the specific district heating system. The primary energy factor of a district heating system is the relation of the primary energy input QP to the system compared to the heat QC delivered at the border of the supplied buildings, i.e. at the primary side of the dwelling substation. Thus the heat losses of the dis­tri­bu­tion piping system are in­cluded as well as all other energy amounts for extrac­tion, preparation, re­fining, processing, and transportation of the fuels to produce the heat.

(1)

where:


QP primary energy input to the system

QC heat delivered at the border of the supplied buildings

The primary energy factor is defined to be greater or equal zero*).

The primary energy factor has to be determined within the thermodynamic system borders of the specific district heating system. This is usually the area supplied by one heat distribution piping system.

Within this area all energy inputs and all energy outputs are considered. Energy as input to the system is weighted by its specific primary energy factor.

In this balance electrical power is included as well using a primary energy factor according to that part of the fuel mix, which is replaced by heat and power cogeneration (power bonus method).

Waste heat and regenerative heat sources are included by appropriate primary energy factors. According to the regional situation of energy supply deviating values may be defined in national annexes to this standard. Primary energy factors for fuels and electricity (informative values) are given in annex B table B1.

In principle the balance can be written as



(2)

where


fP,DH

Primary energy factor of the district heating system.

fP,F,i

Primary energy factor of the i-th fuel or final energy input.

fP,elt

Primary energy factor of replaced electrical power.

WCHP

Cogenerated electricity as defined in Annex II of Directive 2004/08/EC.

 QC,j

Sum of the heat energy consumption measured at the primary side of the dwelling stations. of the sup­plied buildings within the period of interest (usually one year).

QF,i

Final energy consumption to produce heat and power of the i-th fuel within the same period.


4.2Energy Requirements of the Dwelling Substations


The energy performance of the dwelling substations is rated by evaluation of its heat losses.

The electricity consumption of auxiliary equipment can be neglected.

The heat losses depend on


  • the insulation,

  • the nominal load of the station,

  • the temperature differences between the heating media and the ambient temperature.

5District heating system calculation

5.1Primary Energy Factor

5.1.1Calculation based on measurements


F
or existing district heating systems usually all needed inputs are known by measurements. Figure 2 shows the method of the calculation.

Figure 2 — Method of the Balance for an Existing District Heating System

The inputs to the calculation are:



QF,i

Fuel (final energy) input to the heating plants and to the cogeneration plants within the considered system within the considered period (usually one year). The amount of this energy is measured at the point of delivery.

fP,F,i

Primary energy factor of the fuel (final energy) inputs. These factors are given in a national annex to this standard. If no national values are available the values from annex B table B1 can be used as informative values.

WCHP

Electricity production of the cogeneration plants of the considered system.

QCHP,ext

Heat delivery to the considered system from external cogeneration power plants.

WCHP,ext

Power losses of external cogeneration plants due to heat extraction, if heat is delivered to the system from outside (only used, if fP,CHP,ext is not available).

fP,elt

Primary energy factor of electrical power. This factor is given by the European average (informative value in annex B table B1) or in a national appendix to this stan­dard determined in accordance to principles laid down in Annex III of Directive 2004/08/EC.

QC,I

Heat energy consumption measured at the primary side of the dwelling substations of the supplied buildings within the period of interest (usually one year).

HN

Efficiency of the heating network.

The result of the calculation is the primary energy factor fP,DH of the considered district heating system. The calculation formula results from the above balance:

(3)

External heat supply to the district heating system

External heat deliveries to the considered system should be treated in the same way as a fuel input by weighting the external heat delivery Qext by its primary factor fext,.

If cogenerated heat QCHP,ext is delivered to the considered district heating system and its primary factor fP,CHP,ext is not known, the power loss WCHP,ext due to the heat extraction of the external cogeneration plant weighted by the primary energy factor fP,elt of electrical power and the effi­ciency HN of the external heating net­work can be used in­stead as the appropriate input to formula (3):

(4)

HN can be set to HN = 0.90. The power losses of external cogeneration plants WCHP,ext applying to the considered district heating system should be calculated in relation to the total power losses of these plants. The relation of these losses to the total heat production of these plants is the power loss factor s:



(5)

This factor should be applied to the external CHP heat delivery to the system:



(6)

Examples are provided in annex A.


5.1.2Calculation from Planning Data


For cogeneration systems the usual planning data are used as input to the calculation. The method of balancing is drawn in figure 3.




Figure 3 — Method of Balance on the Basis of Planning Data

Efficiencies i should be used, which were evaluated according to the appropriate CEN stan­dards:

Combustion heat generator: (7)

Cogeneration appliance: (8)

where:

QF,HP

Fuel consumption of the combustion heat generator during the period of interest (usually one year).

QHP

Heat production of the combustion heat generator measured at the output of the generator during the same period.

QF,CHP

Fuel consumption of the cogeneration appliance during the same period

WCHP

Power production of the cogeneration appliance during the same period measured at the output of the appliance

QCHP

Heat production of the cogeneration appliance during the same period measured at the output of the appliance

Besides the efficiency characteristics of the products, the following planning figures are necessary for the calculation:

- The relation  of power and heat production of the cogeneration appliance:



(9)

- The relation  of heat produced by the cogeneration appliance to the total heat production:



(10)

The efficiency factor of the heat distribution network HN can be set to

HN = 0.90

or may be evaluated in a national annex.

The balance is

(11)

Solving this equation for fP,DH and replacing all terms by the planning figures respectively the product efficiency characteristics yields



(12)

An example is given in appendix A.


5.1.3Auxiliary Energy Consumption


Auxiliary energy consumption is included in the above balance in that way, that only the net power pro­duction, i.e. the power production minus all auxiliary consumption e.g. for pumps etc., is used for the ba­lance.

If there is no electricity production in the district heating system, than the electricity consumption of the auxiliary equipment has to be reported separately.


5.1.4Recoverable Heat Losses


No losses are recoverable.

5.1.5Calculation Period


It is recommended to use one year as the calculation period. For the winter and the summer period primary energy factors may be calculated additionally. According to this method it is as well possible to calculate monthly balances, which is usually too complex.

5.2Energy Requirements of the dwelling substations


The dwelling substation is characterised by the insulation level of its components. This level is described in prEN ISO12241.

The energy requirement of the dwelling substation is the heat loss of the station.

Auxiliary power consumption can be neglected.

Note:

The insulation level of the primary circuit should be one class above that of secondary circuit. All components of the dwelling station should be in­su­la­ted except the control components.

5.2.1Heat Losses of the dwelling substation


The heat loss QDS of the dwelling substation is calculated with:

QDS = HDS  (DS – amb) (13)

where:

HDS

Heat exchange coefficient of the substation calculated by equation (14)

DS

Mean temperature of the dwelling station calculated by equation (15)

amb

Ambient temperature at the location of the dwelling station

HDS = BDS  DS 1/3 (DS in kW, HDS in kWh/Ka) (14)

where:


BDS

Coefficient depending on the type of the dwelling station and its insulation level. BDS should be provided in a national annex. Informative values are given in table 3.

DS

Nominal heat power of the dwelling station in kW.

DS = DDS  P,DS + (1 – DDS)  S,DS (15)

where:


DDS

Coefficient depending on the type of the dwelling substation and its control. DSS should be pro­vided in a national annex. Informative values are given in annex B table B2.

P,DS

Mean heating medium temperature of the primary circuit of the dwelling substation. Typical values should be provided in a national annex. Default values are given in annex B table B2.

S,DS

Mean water temperature of the secondary circuit of the dwelling substation calculated in the same way as if there were any other heat generator (see another part of prEN 14335)

The above equations are numerical equations. If the unit of the nominal power of the dwelling station is kW, the result of the calculation if the heat loss QDS is kWh/a.







Insulation Class of the Components of the Dwelling Station According to prEN ISO 12241

Insulation of Secondary Circuit

4

3

2

1

Insulation of Primary Circuit

5

4

3

2

Type of Network

Hot Water, Low Temperature

3.5

4.0

4.4

4.9

Hot Water, High Temperature

3.1

3.5

3.9

4.3

Vapour, Low Pressure

2.8

3.2

3.5

3.9

Vapour, High Pressure

2.6

3.0

3.3

3.7

Table 3 —  Coefficient BDS as Function of Insulation Type and Category

5.2.2Auxiliary Energy Consumption


The auxiliary energy consumption is neglected.

5.2.3Recoverable Heat Losses


If the dwelling substation is located in the heated space the total amount of the heat losses of the dwelling station is recoverable.

If the dwelling substation is located in an unheated part of the building, the heat losses are not recovered.



Bibliography

GEMIS: Global Emission Model of Integrated Systems, Ökoinstitut, Freiburg, Germany (available free of charges from www.oeko.de/service/gemis/)

CEN/CENELEC Workshop 14 on "Manual for the Determination of CHP Products"

Directive 2001/77/EC on the “Promotion of Electricity Produced from Renewable Energy Sources in the Internal Electricity Market”

Draft Directive COM (2003) 739 on “Energy End-use Efficiency and Energy Services” presented by the Commission in December 2003


  1. (informative)
    100

    Examples

    1. Typical Situation of Public Utilities of a City


The public heat and power supply company of a city operates a cogeneration plant and a heat plant in another part of the city. Natural gas is used as fuel. The system border is the total heat supply area. The following figures were measured during one year:

Total heat consumption, measured at the primary side of the dwelling stations:

 QC

350,000 MWh/a

Annual gas consumption of the cogeneration plant, measured at the delivery point of the gas:




1,050,000 MWh/a

Annual gas consumption of the heating plant, measured at the delivery point of the gas:




50,000 MWh/a

Total gas consumption:




1,100,000 MWh/a

The unit of the gas consumption refers to the combustion energy inclusive the condensation enthalpy. Thus the total gas consumption has to be cor­rected according to the condensation enthalpy, which is 10 %. Corrected value of the total gas consumption:

 QF

1,000,000 MWh/a

Power production, total, measured at the input to the public power supply network:




350,000 MWh/a

Internal power requirements for pumps etc.:




3,000 MWh/a

Net power production:

WCHP

347,000 MWh/a

All other values of equation (3) do not apply. The primary energy factor of natural gas is 1.10 and of electrical power 2.50. From equation (3) the primary energy factor of the district heating system of

can be calculated.


    1. Typical Situation of an Industrial Power Plant Supplying Internal Requirements and a City Nearby


A large industrial complex operates its own power plant mainly for the internal needs of power, heat and cooling energy. As well the plant serves a nearby city with heat. The city heat network is operated by a public enterprise of the city. The system border is the city heating system.

From the technical data of the power plant and from measurements at the points of delivery the following data are known:



Maximum power capacity of the plant in full condensation operation:




350 MW

Average power capacity during heat extraction operation:




300 MW

Power loss due to heat extraction (350 - 300) / 300:




16.7 %

Total annual power production of the plant:




2,200,000 MWh/a

Total heat extraction of the plant:




1,900,000 MWh/a

Total power loss of the plant (16.7 % of 2,200,000 MWh/a)




366,700 MWh/a

Heat delivery to the city district heating system:




1,600,000 MWh/a

Net power loss due to the district heating system (delivered/total heat  power loss 1.600.000 / 1.900.000  366.700):

WCHP,ext

308,800 MWh/a

Total heat consumption within the district heating system:

 QC

1,400,000 MWh/a

With this figures formula (3) yields:


    1. Typical Situation of Small Heat and Power Cogeneration Systems


A small heat and power cogeneration system is planned to supply a new settlement of 100 one family houses. The heating design load of the settlement is 500 kW, the basic load is 50 kW. A gas motor shall be used for heat and power cogeneration. Its heat power is 50 kW, the electrical power 40 kW, the fuel consumption 115 kW. The cogeneration module can operate 6,000 h/a determined from the frequency of the heat loads. The remaining heat is produced by heating boilers. The total heat energy needed equals 1,400 h/a full load operation.

Efficiency of the cogeneration module: CHP = (40 + 50) / 115 = 0.78

Efficiency of the heating vessels: HP = 0.87

Efficiency of the heating distribution network: HN = 0.90

Power to heat ratio of the cogeneration module:  = 40 / 50 = 0.80

Cogeneration heat to total heat ratio:  = (50  6,000) / (500  1,400) = 0.43



With these figures equation (12) yields




  1. (informative)
    200

    Primary energy factor, dwelling substation performance


Fuel

Primary Energy Factor

Primary resource Factor

Lignite Coal

1.30

1.30

Hard Coal

1.20

1.20

Oil

1.10

1.10

Natural Gas

1.10

1.10

Excess heat e.g. from industrial proc.

1.05

0.05

Regenerative Energies (e.g. Wood)

1.10

0.10

Waste as Fuel, Landfill Gas

1.00

0.00

Electrical Power, European Average

2.80

2.60

Table B.1 — B.Primary Energy Factors (Informative value)

Type of Dwelling Station

Primary Temperature P,DS ( °C)

DDS

Hot Water, Low Temperature

105

0.6

Hot Water, High Temperature

150

0.4

Vapour, Low Pressure

110

0.5

Vapour, High Pressure

180

0.4

Table B.2 — B. Primary Temperature and Coefficient DDS According to the Type of Dwelling Station

*) In the case of heat and power cogeneration based on regenerative energies such as biogas negative primary energy factors may occur. These are set equal zero.

Document type:   European Standard

Document subtype:   

Document stage:   CEN Enquiry

Document language:   E


  STD Version 2.1c



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