Jürgen Schilling Viessmann Werke sjue@viessmann.com Calculation of the integrated energy performance of buildings EN 15316: Heating systems in buildings Method for calculation of system energy requirements and system efficiencies Part 4-7: Space heating generation systems, biomass combustion systems Jürgen Schilling Viessmann Werke sjue@viessmann.com Johann Zirngibl CSTB johann.zirngibl@cstb.fr

The EU CENSE project (Oct. 2007 - March 2010) Aim of the project: To accelerate adoption and improved effectiveness of the EPBD related CEN- standards in the EU Member States These standards were successively published in the years 2007-2008 and are being implemented or planned to be implemented in many EU Member States. However, the full implementation is not a trivial task Main project activities: To widely communicate role, status and content of these standards; to provide guidance on the implementation To collect comments and good practice examples from Member States aiming to remove obstacles To prepare recommendations to CEN for a “second generation” of standards on the integrated energy performance of buildings

Brief introduction A brief introduction to the CENSE project and the CEN-EPBD standards is provided in a separate presentation:

More information More information and downloads: www.iee-cense.eu Disclaimer: CENSE has received funding from the Community’s Intelligent Energy Europe programme under the contract EIE/07/069/SI2.466698. The content of this presentation reflects the authors view. The author(s) and the European Commission are not liable for any use that may be made of the information contained therein. Moreover, because this is an interim result of the project: any conclusions are only preliminary and may change in the course of the project based on further feedback from the contributors, additional collected information and/or increased insight.

FITTING INTO THE CALCULATION SCHEME This standard is part of a series (EN 15316) for the calculation of heating system energy requirements and system efficiencies. The whole series of EN standards is a modular structure. The information going from one block to the next is the energy flow and, within systems, heating medium temperatures and water flow rates. More details on the general calculation scheme can be found in EN 15603 and EN 15316-1.

BUILDING ENERGY PERFORMANCE CALCULATION GENERATION SYSTEMS HEATING SYSTEM 15316-4-1 BOILERS This standard does not cover oil and gaz fired boilers and air heaters which are treated as dedicated parts (EN 15316-4-1 and prEN 15316-4-8 respectively). Specific parts of EN 15316-4 are dedicated to other generation devices (heat pumps, solar systems, etc.) as well. The standard provides calculation methods for the energy performance of heat generation of biomass combustion systems with respect to: - type of stocking device (automatic or by hand); - type of biomass fuel (pellets, chipped wood or log wood); - including control. Boiler sizing is not covered by this standard. This standard is intended to calculate the in-use energy performance of a given boiler, either existing or as designed and sized. 15316-4-7 BIOMASS

More than 1 generator? The complete calculation flow for a heating and domestic hot water system is as follows: start with building needs calculation (2 zones heating and 1 zone d.h.w. as shown) continue the calculation adding up losses of each subsystem until you reach storage and distribution give priority to the appropriate generation subsystem (solar system in this case) calculate priority generation subsystem first (solar system according to EN 15316-4-3 as shown) and get required input energy per each energy carrier calculate the back-up generation subsystem then (boiler according to EN 15316-4-7 as shown) and get required input energy per each energy carrier get total delivered energy as the sum of energy inputs to all generators, per energy carrier (see NOTE for auxiliary energy simplification in this example) convert delivered energy into primary energy according to your national primary energy factor (… or to CO2 emission or whatever) per each energy carrier get the total primary energy get the system efficiency as the ratio of needs to corresponding primary energy NOTE: to simplify the picture, auxiliary energy has been considered in the generation subsystems only. Any auxiliary energy used in the other subsystems (i.e. distribution, emission, etc.) shall be added to the electricity carrier total and some recovery might be considered in the relevant subsystems.

Calculation principles Objective: to calculate fuel and auxiliary energy need to fulfill the heat demand of the attached distribution subsystem(s) Basic input data: heat required by the attached distribution sub-system(s) QH,dis,in The calculation method takes into account heat losses (flue gas, envelope, etc.) auxiliary energy use and recovery other input data : location of the heat generator(s) (heated room, unheated room, ..) operating conditions (time schedule, water temperature, etc.) control strategy (on/off, multistage, modulating, cascading, etc.) Basic outputs is delivered energy as: fuel consumption EH,gen,in auxiliary energy consumption WH,gen,aux The three methods calculate fuel and auxiliary energy consumption of one or more boilers to fulfill the heat demand of the attached distribution subsystem(s). The methods take into account boiler heat losses and/or recovery due to the following physical factors: flue gas losses (burner on and boiler at fire bed load); draught losses (burner stand-by); envelope losses (burner on and stand-by); auxiliary energy use (standby/electronics, gas valve, pump, fan); auxiliary energy recovery.

Generation subsystem simplified energy balance TOTAL & RECOVERED AUXILIARY ENERGY 8 2 6 GLOBAL BALANCE 147 53 TOTAL LOSSES AND RECOVERABLE LOSSES 50 The basic inputs and outputs of the generation subsystem are shown. The common input data is the heat required by the attached distribution sub-system(s) QH,dis,in. Optionally, the additional load for domestic hot water distribution subsystem QW,dis,in may be taken into account when using a single generator for both services. Other input data is required to characterize: type and characteristics of the heat generator(s); location of the heat generator(s) (heated room, unheated room, ..); operating conditions (time schedule, water temperature, etc.); control strategy (on/off, cascading, etc.). The basic outputs are: fuel consumption EH,gen,in; auxiliary energy consumption WH,gen,aux; that are used as an input in EN 15603 to calculate primary energy required by the heating system. Other optional output information that may be extracted relates to: generation total heat loss (flue gas, draught and envelope losses); recoverable generation heat losses (explicit or already taken into account as a reduction of losses = recovered losses) seasonal generation efficiency. 3

Available methods Case specific Based on data declared according to Directive 2002/92/CE Primarily intended for new or recent boilers for which this data is available Boiler cycling Primarily intended for existing systems and condensing boilers Tabulated (precaculated) values Simplification to cover common case and avoid calculation burden to estimate simple repetitive cases 3 methods have been defined because no single method provides a correct solution for all cases. A too simplified method may not be able to show the effect of improvements, whilst a detailed method may be unnecessarily time consuming for common situations. The boiler typology method is based on data coming from direct measurements of the boiler efficiency (fuel in and heat out measured). It is a reliable and easily applied method, suitable for use by people with minimal modeling skills in common situations. The boiler cycling method is based on a calculation of losses (indirect method). It has proven suitable for existing systems, where very few data are available. Simple formulas can be derived to calculate seasonal efficiency according to data collected during an inspection. Precalculated values (according to the previous calculation methods). These values may be used for simple repetitive case (inspections?). If the assumptions for the precalculated values are not met (boundary conditions), boiler typology or boiler cycling method shall be used.

Case specific method calculation procedure Get performance data in standard conditions at 3 reference power levels Efficiencies at 100% and 30% load (according to Directive 92/42/EC) Stand-by losses power [W] at 0% load Correct data to take into account actual operating conditions (basically, the effect of water temperature in the boiler) Calculate losses power at 30% and 100% from corrected efficiencies Calculate losses at actual load by linear interpolation Use the same interpolation approach (based on data at 0…30%...100% load) for auxiliary energy calculation Parameters required to characterize the boiler for the case specific method are: generator output at full load (reference boiler power); generator efficiency at full load; generator average water temperature at test conditions for full load; generator efficiency at intermediate load; generator average water temperature at test conditions for intermediate load; stand-by heat losses at test temperature difference; difference between mean boiler temperature and test room temperature in test conditions; power consumption of auxiliary devices at full load; power consumption of auxiliary devices at intermediate load; stand-by power consumption of auxiliary devices; minimum operating boiler temperature. Full load and part load test data are generally available for new or recent boilers as they are required by the Boiler Efficiency Directive (92/42/EEC). For existing old boilers, these data are generally not available Standby-losses and auxiliary power consumption data are generally not available. Default data shall be given in a national annex to complete data for new boilers, and to use this method for existing boilers, as these factors are not easily measured directly.

2 - CORRECTED DATA AT ACTUAL OPERATING CONDITIONS 4 – ACTUAL LOSSES 1 - TEST DATA AT REFERENCE CONDITIONS 3 – ACTUAL LOAD The animation highlights the calculation procedure Corrections of efficiencies are assumed to be linear according to average water temperature. A second order interpolation of the 3 points is also allowed in the standard.

Boiler directive data ??? Sometimes it is not easy to find boiler directive data… especially for old boilers like the 2 shown in the picture.

Boiler cycling generation energy balance CALCULATION START DISTRIBUTION NEED CALCULATION RESULT FUEL & AUXILIARY BOILER BURNER The diagram shows the detailed energy balance when using the boiler cycling method. This method performs an analysis of boiler LOSSES. Note that there are 2 contributions to auxiliary energy: Auxiliary energy for the burner fan (Wbr) , which is dependent on the boiler load Auxiliary energy for any primary pump (Wpmp) on the generation circuit, which is assumed to be constant power. LOSSES

Boiler cycling method For single stage burners, the calculation interval is divided into two basic operating conditions, with different specific losses: Burner ON time, with flue gas and envelope losses Burner OFF time , with draught and envelope losses Loss factors are given as a percentage of combustion power (input to the boiler) Loss factors are corrected according to operating conditions (water temperature in the boiler, load factor) The required input load factor to meet output requirement is calculated Modulating and multistage boilers are taken into account with a third reference state: burner ON at minimum power Basic boiler characterization input parameters for the boiler cycling method (single stage burner) are: maximum combustion power of the generator (test conditions); heat loss factors at test conditions for flue gas losses (burner on), heat loss factors at test conditions for draught losses (burner stand-by) heat loss factors at test conditions for envelope losses (burner on and stand-by); average boiler water temperature at test conditions for burner on; average boiler temperature at test conditions for burner off; temperature of test room; electrical power consumption of auxiliary appliances (before the generator, typically burner fan) and related recovery factor; electrical power consumption of auxiliary appliances (after the generator, typically primary pump) and related recovery factor. Full load and part load flue gas losses with burner on are generally available for new boilers and can easily be measured on existing boilers (see EN 15378, Annex C). Standby-losses and power consumption data are not typically available, nor are they easily measured. Missing data shall be estimated using tables with default values.

Boiler cycling method Specific losses at different situations are discribed in the table: Deleted Basic boiler characterization input parameters for the boiler cycling method (single stage burner) are: maximum combustion power of the generator (test conditions); heat loss factors at test conditions for flue gas losses (burner on), heat loss factors at test conditions for draught losses (burner stand-by) heat loss factors at test conditions for envelope losses (burner on and stand-by); average boiler water temperature at test conditions for burner on; average boiler temperature at test conditions for burner off; temperature of test room;

BOILER CYCLING METHOD: LOSSES WITH BURNER ON Envelope αge  2% (0,5…5%) Chimney αch,on  10% (3…15%) Losses through the chimney with burner ON Losses shall be corrected according to the operating water temperature. Losses through the chimney with burner ON increase with flue gas temperature (approx. 1% every 20 °C). In turn, flue gas temperature increases just like the average water temperature in the boiler Losses through the envelope are controlled by the boiler insulation layer and are therefore proportional to the difference between average temperature in the boiler and boiler room temperature. A small correction is also performed according to the load factor (exponential correction) to take into account the fact that at very low loads the losses are reduced. BOILER CYCLING METHOD: LOSSES WITH BURNER ON

BOILER CYCLING METHOD: LOSSES WITH BURNER OFF Envelope αge  2% (0,5…5%) Chimney αch,off  1% (0,2…3%) Losses through the chimney with burner OFF Losses shall be corrected according to the water temperature. Losses through the envelope are controlled by the boiler insulation layer and are therefore assumed to be proprotional to the difference between average temperature in the boiler and boiler room temperature. Losses through the chimney with burner OFF increase with flue gas temperature and are assumed to be proportional to the difference between average temperature in the boiler and boiler room temperature. BOILER CYCLING METHOD: LOSSES WITH BURNER OFF

BOILER CYCLING METHOD: EFFECT OF INTERMITTENCY Boiler cycling diagram This diagram shows graphically the calculation procedure for a single stage burner. The vertical axis is power, as a percentage of combustion power. The horizontal axis is time Areas are therefore energies. Areas with burner ON (minute 5 to 7 and 15 to 17) Area E = A1+A2+B+C is the total energy of fuel burned during burner ON time (100% of combustion power multiplied by ON time) Area A1 represents flue gas losses during burner ON time ηc is combustion efficiency. It can be measured according to EN 15378 annex C Area A2 represents envelope losses during burner ON time ηu is net efficiency. It is the value declared by the manufacturer at 100% load , according to directive 94/42/CE Area B + C is total heat delivered to the distribution subsystem during burner ON time Area with burner OFF(minute 7 to 15) Area B are losses through the envelope and through the chimney with burner OFF. Area B is heat taken back from the distribution subsystem during burner OFF time. An equal area B shall therefore be canceled in the burner ON time graph, determining the seasonal efficiency. Area C is the actual net heat delivered to the distribution subsystem during an entire ON-OFF cycle. Actual calculation procedure starts knowing area C and losses factors and determines the load factor. When the load factor is known. Losses can be calculated. BOILER CYCLING METHOD: EFFECT OF INTERMITTENCY

CONTINUOUS OPERATION AT AVERAGE POWER ON-OFF OPERATION @ MINIMUM POWER Modulating boilers BURNER LOAD BOILER LOAD Multistage and modulating generators (effect of burner control) are taken into account by addition of a third reference state: burner ON at minimum continuous power. The performance of these boilers is calculated assuming that the following operating conditions are possible: if the power required by the distribution system is less than the minimum ON power (left), the burner will operate cycling ON-OFF just as a single stage boiler but at minimum power; if the power required by the distribution system is higher than the minimum ON power (right), the boiler will stay ON continuously and its loss factors are calculated by interpolation between minimum load and maximum load values. CONTINUOUS OPERATION AT AVERAGE POWER ON-OFF OPERATION @ MINIMUM POWER

MINIMUM POWER IS THE SET VALUE (TYPICALLY 25…50% OF MAX. POWER) Envelope αge  2% (0,5…5%) Chimney αch,on,MIN  8% (1…12%) BOILER CYCLING METHOD: LOSSES WITH BURNER ON AT MINIMUM POWER (MODULATING AND MULTI STAGE BURNERS) MINIMUM POWER IS THE SET VALUE (TYPICALLY 25…50% OF MAX. POWER) For multi-stage and modulating burners, the following additional data are required: minimum combustion power with burner on (manufacturer data or actual set value); heat loss factors for flue gas losses (burner on) at minimum combustion power (can be measured); auxiliary energy power at minimum combustion power. This method takes into account two effects of modulating the burner power: improved load factor (this reduces the impact of stand-by losses) better efficiency at low loads (NOTE: for some types of burners, efficiency decreases at low load: this is taken into account as well)

Why several methods No single method is the correct solution for all cases. A too simple method may not be able to show the effect of improvements whilst A detailed method may be time wasting for common repetitive situations. The case specific method is meant to use as far as possible boiler directive data. The boiler cycling method is meant to deal with existing boilers/buildings, to keep a connection with directly measurable parameters (flue gas analysis).

Parametering the methods Required data and default data for common situations are included in the annexes Annex A: default data for case specific method Annex B: default data for boiler cycling method Annex C: storage systems Annex D: calculation example for case specific method Annex E: calculation example for boiler cycling method Default data can be adjusted through a national annex.

More information More information and downloads: www.iee-cense.eu Disclaimer: CENSE has received funding from the Community’s Intelligent Energy Europe programme under the contract EIE/07/069/SI2.466698. The content of this presentation reflects the authors view. The author(s) and the European Commission are not liable for any use that may be made of the information contained therein. Moreover, because this is an interim result of the project: any conclusions are only preliminary and may change in the course of the project based on further feedback from the contributors, additional collected information and/or increased insight.