Task 4 - final
Preparatory Study on Eco-design of CH Boilers
Task 4 Report (FINAL) Technical Analysis (incl. System Model)
René Kemna Martijn van Elburg William Li Rob van Holsteijn
Delft, 30 September 2007
VHK Van Holsteijn en Kemna BV, Elektronicaweg 14, NL-2628 XG Delft, Netherlands Report prepared for: European Commission, DG TREN, Unit D3, Rue de la Loi 200, 1100 Brussels, Belgium Technical officer: Matthew Kestner
DISCLAIMER & IMPORTANT NOTE The authors accept no liability for any material or immaterial direct or indirect damage resulting from the use of this report or its content. This report contains the results of research by the authors and any opinions in this report are to be seen as strictly theirs. The report is not to be perceived as the opinion of the European Commission, nor of any of the expertsor stakeholders consulted.
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission II
CONTENTS
page
1 INTRODUCTION ...... 1 1.1 Scope ...... 1 1.2 Approach...... 2 1.3 Report structure...... 3
2 BASIC ENERGY AND MASS BALANCE ...... 5 2.1 Introduction...... 5 2.2 Global chemical reaction ...... 6 2.3 Mass balance...... 6 2.3.1 Stoichiometric volume balance ...... 6 2.3.2 Air factor/ lambda ...... 6 2.3.3 Humidity of combustion air ...... 7 2.3.4 Influence of emissions ...... 7 2.3.5 Converting volume into mass balance...... 9 2.4 Energy balance combustion...... 10 2.4.1 Introduction...... 10 2.4.2 Combustion heat Qrad + Qconv ...... 11 2.4.3 Latent condensation heat Qlatent...... 13 2.4.4 Heat loss in excess combustion air Qxsair ...... 15 2.4.5 Fuel loss Qfuel-loss ...... 15 2.5 Energy balance burner...... 17 2.6 Heat balance primary heat exchanger ...... 22 2.6.1 Introduction...... 22 2.6.2 Flue gas losses in on-mode ...... 24 2.6.3 Losses through the generator envelope in on-mode ...... 26 2.6.4 Standing losses in off-mode...... 27 2.6.5 Start-stop losses...... 31 2.6.6 Primary heat exchanger: Flow diagram ...... 33 2.7 Heat balance secondary and tertiary heat exchanger...... 34 2.7.1 Secondary heat exchanger ...... 34 2.7.2 Tertiary heat exchanger ...... 35 2.8 Heat balance with storage facilities ...... 36 2.9 Auxiliary energy ...... 37 2.10 Total energy balance ...... 38
3 EMISSIONS ...... 40 3.1 Introduction...... 40 3.2 Environmental impact ...... 41 3.3 Emissions grouped by origin ...... 43 3.4 Low non-CO2 Carbon Emission...... 44 3.4.1 Formation ...... 44 3.5 Low NOx technology...... 45 3.5.1 Introduction...... 45 3.5.2 Formation of NOx...... 46 3.6 Principles of Primary Control of NOx Emissions...... 47 3.6.1 Modification of Fuel/Air Delivery-Burner System...... 48 3.6.2 Modification of Gas Burner ...... 51 3.6.3 Primary NOx Control Technology Status...... 54 3.6.4 Secondary Control of NOx Emission...... 56 3.7 Low emissions vs boiler performance/efficiency ?...... 56 3.8 References...... 58
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4 BURNERS ...... 59 4.1 Introduction...... 59 4.2 Trends ...... 59 4.3 Types ...... 60 4.3.1 Surface burners...... 60 4.3.2 Jet burners...... 64
5 HEAT EXCHANGERS...... 68 5.1 Introduction...... 68 5.2 Typology...... 70 5.3 HE – material...... 73 5.4 HE – shape and design ...... 74 5.4.1 Heat exchangers based on tubes (finned and un-finned) ...... 74 5.4.2 Heat exchangers based on plates...... 77 5.4.3 Heat exchangers based on integrated castings (aluminium, cast-iron)...... 78 5.4.4 Other heat exchangers types...... 80
6 BOILER CONTROLS ...... 81 6.1 Introduction boiler control &components...... 81 6.2 Power input control ...... 83 6.2.1 Pneumatic ratio-control...... 83 6.2.2 Integrated mixing & control valve ...... 84 6.2.3 Turndown ratio oil boilers...... 85 6.2.4 Multi-stage boiler installations (cascade) ...... 86 6.3 Fuel/air ratio control ...... 86 6.3.1 Measurement of flame ionization...... 88 6.3.2 Measurement of O2 ...... 89 6.3.3 Measurement of CO ...... 89 6.3.4 Measurement of viscosity ...... 90 6.4 Pump- and feed temperature control ...... 90 6.4.1 Flow control ...... 91 6.4.2 Feed temperature control ...... 93 6.5 Summary...... 94
7 ROOM TEMPERATURE CONTROL ...... 95 7.1 Introduction...... 95 7.2 Single Room Thermostat controlled systems...... 96 7.2.1 Principle...... 96 7.2.2 Developments ...... 96 7.2.3 Pros and Cons ...... 97 7.2.4 Product examples ...... 98 7.3 Weather controlled system ...... 99 7.3.1 Principle...... 99 7.3.2 Developments ...... 100 7.3.3 Pros and Cons ...... 100 7.3.4 Product examples ...... 101 7.4 Thermostatic valves ...... 102 7.4.1 Principle...... 102 7.4.2 Developments ...... 105 7.4.3 Pros and Cons ...... 105 7.4.4 Product examples ...... 106 7.5 Combined room- and feed temperature controlled systems...... 110 7.5.1 Principle...... 110 7.5.2 Product examples ...... 111 7.6 Multiple room temperatures controlled systems ...... 111 7.6.1 Principle...... 111 7.6.2 Product examples ...... 113
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7.7 Occupancy control ...... 115 7.7.1 Principle...... 115 7.7.2 Product examples ...... 117 7.8 Summary...... 118
8 DISTRIBUTION SYSTEM ...... 120 8.1 Introduction...... 120 8.2 Heat losses ...... 120 8.3 Hydraulic losses ...... 121 8.4 Piping components and materials ...... 123 8.5 Variable Speed Pumps ...... 125 8.6 Summary...... 127
9 EMITTER SYSTEM ...... 128 9.1 Introduction...... 128 9.2 Non uniform temperature distribution ...... 128 9.3 Position of emitter ...... 130 9.4 Radiators...... 131 9.4.1 Introduction...... 131 9.4.2 Heat output...... 132 9.4.3 Pros and Cons ...... 133 9.4.4 Developments ...... 134 9.4.5 Product examples ...... 134 9.5 Convectors...... 135 9.5.1 Introduction...... 135 9.5.2 Heat-output ...... 136 9.5.3 Pros and cons...... 136 9.5.4 Developments ...... 137 9.5.5 Product examples ...... 137 9.6 Surface heating ...... 139 9.6.1 Introduction...... 139 9.6.2 Heat output...... 142 9.6.3 Pros and Cons ...... 142 9.6.4 Developments ...... 143 9.6.5 Product examples ...... 143 9.7 Summary...... 146
10 HEAT PUMP BOILERS...... 147 10.1 Introduction...... 147 10.2 Typology...... 147 10.2.1 Vapour Compression Cycle...... 148 10.2.2 Absorption cycle°...... 148 10.2.3 Heat Sources and Heat Sinks ...... 149 10.2.4 Technical Product Configurations...... 150 10.2.5 Current Heat Pump Products ...... 150 10.3 System Design and Application ...... 154 10.3.1 System design and installation: critical factors...... 154 10.3.2 Application in new-built, renovation and retrofit ...... 155 10.3.3 Experience HP countries ...... 156 10.4 Energy Balance and Seasonal Efficiency ...... 160 10.4.1 Terminology...... 160 10.4.2 Seasonal Performance Factor (IEA HPP Annex 28) ...... 164 10.4.3 prEN 15316-4-2...... 169 10.4.4 Assessment of SPF -calculation methods...... 175 10.5 Technical Analysis Heat Pumps...... 179 10.5.1 Ground- and Water Source Heat Pumps...... 179 10.5.2 Air Source Heat Pumps ...... 191
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission V 10.6 Technical developments ...... 196 10.6.1 Heat pump controls ...... 196 10.6.2 Other Heat Pump Principles...... 198
11 SYSTEM ANALYSIS ...... 201
ANNEX A: ECOBOILER DOCUMENTATION...... 203
ANNEX B: MODEL REVIEWS ...... 225
ANNEX C: BOILER MODEL NOTES...... 237
ANNEX D: REFERENCE MATERIAL...... 266
ANNEX E: EMISSIONS ACCORDING TO GEMIS 4.2...... 283
ANNEX F: REFERENCES ...... 284
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LIST OF TABLES
page Table 2-1. Max. volume % Water of air (1013 mbar) and saturation pressure (psat) at various temperatures (Temp.) [source: Farago, 2004] ...... 7 Table 2-2. Emissions gas fired boilers (source Pfeiffer, 1) ...... 8 Table 2-3. Emissions oil fired boilers (source: Pfeiffer, 1) ...... 8 Table 2-4. Conversion from volume to mass balance of 1 m³ methane combustion...... 9 Table 2-5. Energy levels of different fuels at 273 K and 1013 mbar ...... 11 Table 2-7. Calculating calorific flame temperature for 1 m³ methane at air factor = 1,2...... 12 Table 2-8. Estimated temperatures and loads for pre-mix burners (at air factor 1,2, no preheat air)...... 19 Table 2-9. Default flue gas losses of the boiler on-mode as a percentage of nominal power under test conditions (P’ch,on) at typical boiler test temperatures (prEN 15316-4-1, table C1)...... 25 Table 2-10. Value of parameters A and B (heat loss through envelope parameters)...... 27 [prEN 15316-4-1, table C3] ...... 27 Table 2-11. Default values of factor kgn,env (reduction factor for recovery of heat losses of envelope) [prEN 15316-4-1, table C4]...... 27 Table 2-12. Parameters for calculation of stand-by heat losses. [prEN 15316-4-1, table B2] ...... 28 Table 2-13. Auxiliary energy consumption (electrical) [Source: Boiler Savelec Study, WP3] ..... 37 Table 2-14...... 38 Indication of characteristic generator heat losses for 4 boiler types and 2 control types (space heating only) [VHK estimate]...... 38 Table 3-1. Use phase: Energy and emissions per GJ heat out CH boiler, (excl. Electricity for fossil fuel based heating) [VHK 2006, based on Öko-institut GEWIS database]...... 40 Table 3-2. Boiler operating conditions (GEWIS 4.2) ...... 40 Table 3-3. Target/Limit values in EC Ambient Air Quality directives (VHK, MEEUP, 2006).....41 Table 3-4. Comparison of primary NOx control strategies for residential gas appliances*. (source: Joynt, B, Wu, S., 2000)...... 55 Table 7-1. Description of room temperature control systems that are predominantly used (1 & 2) and a recently introduced room temperature control system (3)...... 95 Table 7-2 from prEN 15316-2-1: Energy performance factors for heat emission control according to DIN 4701-10...... 104 Table 7-3. Overview of presence detection sensors...... 116 Table 8-1. Table A.2 from prEN 15316-2-3:2005 ...... 121 Table 9-1. Heat emission efficiency for spaces with normal ceiling heights (< 4m); from informative annex A prEN 15316-2-1...... 130 Table 9-2. Spatial temperature variation by type of emitter and the corresponding spatial variation class; from informative annex D prEN 15316-2-1, based on the French RT2000 ...... 130 Table 9-3. Share of radiation in total heat output of radiators (according to EN 442) ...... 133 Table 9-4. Optimal and maximal average floor temperatures for various rooms (acc. ISSO manual)...... 139 Table 9-5. Properties of wet and dry floor heating systems ...... 140 Table 9-6. Properties of wet and dry wall heating systems ...... 140 Table 10-1. Matrix, illustrating the configurational options for heat pump application in heat pump boiler systems (compiled by VHK)...... 150 Table A-1. ECOBOILER Look-up Table...... 215 Table A-2. CH-piping lengths in existing and new buildings Germany (source: IWU Darmstadt) ...... 221 Table A-3. Central Heating distribution losses (IWU-Darmstadt 2005)...... 222 Table A-4. Central Heating distribution losses for typical classes (at Tsys = 50°C and Tambient= 20°C) ...... 222 Table A-5.Parameters for ECOBOILER per size class...... 223 Table A-6. ECOBOILER Look-up Table ...... 223 Table A1: BoM Heating Boilers, Functional Split, avg. EU []...... 267
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission VII Table A2. BoM Heating Boilers, Split by Material, avg. EU [i] ...... 267 Table A3. BoM Heating Boilers, Details per Component, avg. EU [i]...... 268 Table A4. Outcomes for 25 kW boiler at 30% load (7,5 kW) over product life ...... 271 Table A5. All Sectors 1990 ...... 272 Table A6. Gas- and oil-fired CH-boiler heat demand, New (sales) and Installed (stock) 2005 ...... 273 Table A7. Gas- and oil-fired CH-boiler electricity use (excl. CH pump), New/Installed 2005...... 274 Table A8. Electricity consumption of boilers ...... 275 Table A9. Reference scenario...... 275 Table A10. Potential improvements in heating system efficiency [ECI for BRE 2002, SAVE study] ...... 276 Table A11. Overview of scenario results [ECI for BRE, SAVE study]...... 278 Table A12. Bill of materials Nefit Turbo ...... 279 Table A13. Bill of materials Nefit Turbo, grouped...... 282
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission VIII
1 INTRODUCTION
1.1 Scope This is the Draft Final report on Task 4 of the preparatory study on the Eco-design of Central Heating Boilers for the European Commission, in the context of the Ecodesign of Energy-using Products directive 2005/32/EC. The scope of Task 4 is Product System Analysis. It looks into the interaction of the EuP with the installation/system in which it operates during the use phase. Probably more than with any other Energy Using Product, the System Analysis is a vital subject in the assessment of real life energy efficiency and the improvement potential of boilers. This task therefore includes a functional analysis of the system to which the product belongs, including a rough estimate of the overall impacts and an assessment of how the integration of the product into the system and its design can improve its overall environmental performance. For practical reasons this Task 4 report covers also a full technical analysis of boiler components and heating system components, describing technical product features and best available technologies. As such the report covers not only Task 4 but also parts of Task 5 and Task 6.
Figure 1-1. Coverage Task 4 report
Task 6
Task 5
Task 4
0 20406080100
It must be clear that it is outside the scope of the EuP directive to look at measures other than those related to the design and installation (see Annex VII.4 of directive 2005/32/EC) of the EuP. Obviously, a boiler designer/ manufacturer cannot influence Climate characteristics (heating season, degree-days, etc.) Building shell characteristics (insulation heat losses, ventilation losses, orientation) Internal load (humans, appliances, solar, heat capacity of inventory) Heating system characteristics (radiator, convector, low temperature wall/floor heating, tubing, valves; etc.) However, there are certain characteristics of the boiler design that determine how well the boiler interacts with (variations in) the above parameters. These characteristics, in earlier studies referred to as acting on the ‘control efficiency’, determine a significant part of the energy consumption and the emissions of pollutants of the product. As mentioned in the Task 1 report, these characteristics are so far not captured in the EN product test standards (e.g. EN 303). Partly they are addressed in the new draft building performance standards (e.g. prEN 15316), but they are then not translated back at product level where they could be incorporated in CE-marking. For instance, the extend to which a boiler is equipped to follow the weather conditions, adjusting the
Eco-design Boilers, Task 4, Final 30 September 2007 | VHK for European Commission 1 boiler water temperature to the need, is not (fully) incorporated in the product test standard. Yet it is clearly a product feature. The fact whether a boiler is equipped with a flue valve, is clearly another boiler feature reducing the flue gas losses when the boiler is ‘off’, which again is not necessarily picked up in the product test standards. The extend to which a ‘condensing’ boiler can control the system parameters so it can actually achieve these condensing operation conditions in practice is not incorporated. The control of the hydraulic parameters (pump, mixing valves) to achieve optimal heat exchanger efficiency is yet another item. Task 4 sets out to identify and evaluate these boiler features (and more) on a systematic basis. Partly it builds on the data assessed in the SAVE Heating study 2002, mentioned earlier. In this study VHK already indicated and quantified a methodology for the heating system as a whole. Also the annex I in the ECCP-report is a valuable input in this respect. Finally, for the actual modelling the methodology that is developed in the EN standards for the Energy Performance of Buildings will play an important role. Extending on these sources a mathematical model is developed that on one hand is linked to the stock model from subtask 2.2 and on the other hand should incorporate the technical design options in the following tasks. The focus of the model is on the boiler characteristics and how they interact with the heating systems throughout the EU. The other characteristics (climate, housing stock and building shell, internal load, heating systems) are largely a given for the current (most recent) situation, but –e.g. for the sake of the impact analysis in Subtask 5.2— should be expandable to make future projections (2010, 2020) and design-solutions. It is not the intention of VHK to duplicate research work and modelling that is an ongoing activity in many research institutes. Rather it aims to harmonise what has been developed in the energy performance of building standards (prEN 15316) and the product test standards (e.g. EN 303), taking it one step further where necessary. Once this has been achieved, the technical modelling can be linked to the market and stock model from Task 2 and will allow modelling of design options in Task 6.
1.2 Approach For practical reasons, this Task 4 Report not only covers the Product System Analysis, but also a full Technical Analysis of the boiler and its components and of the individual heating system components. Obviously, analysing boilers, boiler components heating system components and their mutual relations, it is more practical to directly include the analysis of their technical product features and their best available technologies. As such this report also provides vital information on the Best Available Technology for boiler and system components and on the product specific data needed for the Definition of the Base-Case. Subsequently this Task 4 Report not only reports on the activities mentioned in Task 4 of the contract, but it also contains detailed information for the requested deliverables of Task 5.1 and Task 6.1 & 6.2. As a part of the activities following under these three subtasks are already performed in this Task 4, the remaining activities for these subtasks will mainly focus on a logical chategorization and representation of data. In addition task 6.1 and 6.2 will give a further analysis on the BAT-options that are not described in this task report, being heatpumps and solar systems and on costs. The boilersystem and heating system components that are analysed and described in this Task 4 are respresented with the following figure.
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission 2
Figure 1-2. Graphic representation of the Heating System boiler and its components and the overall heating system with Boiler System Room Distribution Emitter its components. Temperature System System Burners Control System Heat exchangers
Boiler Controls
The data and knowledge coming from the analysis of these indivual components are used for a System Analysis of the overall Heating System Efficiency on the basis of which a mathematical model is developed.
1.3 Report structure This preliminary Task 4 draft report contains 11 chapters. After this introductory chapter, the next chapters process the following topics: Chapter 2 gives an introduction of the mass- and energy balance of the boiler and describes in a general way the interactions of the boiler with the other boiler components. This Chapter is a basis for a more extended discussion of the system analysis in chapter 10. Chapter 3 discusses the emissions from oil- and gas-fired combustion processes, their nature, impact and current design measures. This Chapter is a basis for a more extended discussion of the burner technology in Chapter 4. Chapters 4 (burners) and 5 (heat exchangers) describe the state of the art in vital components and contain information that can be used when the boiler design options are discussed (task 6). Apart from the energy losses of the boiler and its components, the heating system as a whole will have additional losses through suboptimal boiler controls, losses caused by the room temperature controls system, losses in the heat distribution system and losses caused by emitters. The chapters dealing with these heating system components clearly show, that the boiler influences the heat losses caused by these components. In other words, the boiler and its controls can help minimising the energy losses of the heating system. The nature of these system losses will therefore be further explained in the following chapters. Chapter 6 deals with boiler controls and explains the basic principles and the developments related to power input control, fuel air ratio control, pump control and feed temperature control. It is explained that proper feed temperature control can only be achieved in combination with adequate room temperature control systems. In the next chapter 7 a technical analysis is given on the room temperature control systems that are predominantly used. Estimates are given on the energy losses related to the various room temperature control systems, as well as options for further improvement. Chapter 8 describes the nature and magnitude of the heat distribution losses, and explains how boiler controls could contribute in minimising these losses. Chapter (9) describes what the influences are of the emitter system on energy losses, on feed temperature control and on generator efficiency. In Chapter 10 a compact technical analysis is given on heat pump boiler generator systems, based on public available information that could be gathered and studied within the constaints of this Ecodesign study.
Eco-design Boilers, Task 4, Final 30 September 2007 | VHK for European Commission 3
The final chapter 11 contains the System Analysis of the overall Heating System Efficiency on the basis of which the ECOBOILER mathematical model is developed. This work is mainly documented as an Excel file and in the Annexes: ANNEX A: Documentation of the Excel file for the ECOBOILER model ANNEX B: Intermediate model review by boiler experts and iTG ANNEX C: Notes for the separate boiler model ANNEX D: Reference material ANNEX E: Emissions according toGEMIS 4.2 ANNEX F: List of references
Eco-design Boilers, Task 4, Final | 30 September 2007 | VHK for European Commission 4
2 BASIC ENERGY AND MASS BALANCE
2.1 Introduction In most energy policy studies on heating appliances, the combustion process and the detailed energy- and mass balance of central heating boilers are not explained. The scientific background is not very easy and in general it is not needed for readers in the policy field to go beyond the level of the CH boiler being a ‘black-box’ with a certain efficiency level according to a product test standard. Yet, this approach has also led to a number of notions, myths and half-truths regarding boiler efficiency and emissions in practice which can only be understood (and partially denied) when looking inside the black-box. For this reason we have made an attempt, as part of the system analysis, to provide some guidance for policy makers regarding the basics of the energy and mass balance with a boiler. We have taken methane, the main component of natural gas but also a fuel with a relatively simple structure, as an illustration of a fuel, although references to other fuels also occur. The mass- and energy values should be seen as illustrations, although also here we add results from research that is based on tests with actual boilers. Starting of with the global chemical reaction which mainly produces carbon dioxide and water vapour (paragraph 2.2), this chapter looks at the Mass balance (paragraph 2.3), including Stoichiometric volume balance (the ‘ideal’ theoretical volume balance) Air factor/ lambda (excess air) Humidity of combustion air