9789144085302 by Smakprov Media AB

35 mm

Svend Frederiksen Sven Werner

Svend Frederiksen is professor of Thermal Energy Technology at the department of Energy Sciences at Lund University, Sweden. Sven Werner is professor of Energy Technology at the School of Business and Engineering at Halmstad University, Sweden.

District Heating and Cooling

|â&#x20AC;&#x201A; District Heating and Cooling

Moving heat and cold efficiently in urban areas is the main goal of district heating and cooling systems. By connecting suitable customer heat and cold demands with available heat and cold sources, the demands can be met with the use of fewer resources in comparison to conventional heat and cold supplies, such as boilers and air conditioners. This textbook contains chapters about the fundamental idea of district heating and cooling, energy markets, customer demands, load variations, supply, environmental impact, distribution, substations, system functioning, economics, planning, historical development, current and future use, organisation, and information sources concerning the flows of heat and cold in district heating and cooling systems. District heating and cooling is an interdisciplinary technology containing elements from many general technologies and methodologies, such as combustion, heat transfer, piping, marketing, billing, etc. This book provides basic introductory knowledge about aspects typical of district heating and cooling that is vital for a basic understanding of, or unique to, this niche technology. The book serves as a comprehensive textbook and reference for district heating engineers, university students of engineering, and employees at district heating companies in general. It also provides tangible and useful information for urban planners, economists, policymakers, and others interested in the topic.

District Heating and Cooling Svend Frederiksen Sven Werner

Art.No 36005

www.studentlitteratur.se

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Art. No 36005 ISBN 978-91-44-08530-2 First edition 1:1 © The authors, Svensk Fjärrvärme and Studentlitteratur 2013 www.studentlitteratur.se Studentlitteratur AB, Lund Cover design: Francisco Ortega Cover illustration: Marina Koven/shutterstock.com Printed by Exaktaprinting AB, Sweden 2013

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Content

Preface 9 Chapter 1

Introduction 13

1.1 1.2

Chapter contents 15 Terminology and nomenclature 18

Chapter 2

The fundamental idea of district heating 21 Study questions for Chapter 2 27

Chapter 3

Energy, heat, and cold markets 29

3.1 3.2 3.3

Energy markets 29 Heat markets 33 Cold markets 36 Study questions for Chapter 3 41

Chapter 4

Heat and cold demands 43

4.1 4.2 4.3 4.4 4.5 4.6

Space heating 43 Domestic hot water supply 54 Specific heat use in buildings 57 Industrial heat demands 60 Other heat demands 62 Cold demands 64 Study questions for chapter 4 66

Chapter 5

Heat and cold loads 67

5.1 5.2

Heat load definition 67 Aggregate heat loads before substations 68

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Content

5.3 5.3.1 5.3.2 5.3.3 5.4 5.5 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.6 5.6.1 5.6.2 5.6.3 5.7

Distribution heat losses 76 Heat loss calculations 76 Temperature drop in the respective directions of flow 81 Annual heat losses 82 Heat and cold loads in distribution networks 85 Aggregate heat loads after heat supply units 87 Seasonal heat load variations 87 Heat load weather dependence 90 Daily heat load variations 92 Heat load composition 94 Short-term heat load forecasting 95 Heat load parameters 96 Diversity 96 Capacity utilisation 97 Design heat load 104 Cold loads 106 Study questions and problems for chapter 5 111

Chapter 6

Heat and cold supply 113

6.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.4 6.4.1 6.4.2 6.4.3 6.4.4 6.4.5 6.4.6 6.4.7 6.4.8 6.4.9 6.4.10 6.4.11 6.4.12 6.5

A wide range of possible energy supply sources 113 Boilers and solid fuel combustion 120 Flue gas cleaning and flue gas condensation 136 Flue gas cleaning 136 Boiler efficiency and flue gas condensation 139 Combined flue gas cleaning and condensation 143 Combined heat and power 146 The CHP concept 147 Basic CHP idea illustrated by a gas turbine plant 149 Performance measures 152 Back pressure steam cycle CHP plant 155 High efficiency steam CHP plant 163 Extraction-condensing steam CHP plant 164 Theoretical Carnot cycle CHP plant 169 Combined cycle CHP plant 172 Small-scale CHP plant 174 Normalised power-to-heat diagram with efficiency measures 183 CHP versus small-scale heat pumps 184 Carbon capture and storage CHP 188 Waste incineration (Waste-to-Energy) 191

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6.6 6.7 6.8 6.8.1 6.8.2 6.8.3 6.8.4 6.8.5 6.8.6 6.9 6.10 6.10.1 6.10.2 6.11 6.12 6.13 6.14 6.15 6.15.1 6.15.2 6.15.3

Heat recycling from industrial processes 195 Polygeneration 203 Geothermal district heating and cooling 204 Overview 204 Size of the geothermal resource 206 Ground source heat pumps, a definition issue 206 Geographical distribution and temperature levels 207 Geothermal district heating technology 209 Geothermal combined heat and power 210 Large-scale ambient cold sources 215 Large heat pumps and chillers 218 Vapour compression heat pumps and chillers 218 Absorption heat pumps and chillers 227 Solar district heating and cooling 235 Nuclear district heating 241 Electric boilers 243 Peak and backup heat generation 244 Heat and cold storage 249 Load shifting 250 Short-time heat storage technology and flowcharts 252 Short-time cold storage technology 256 Study questions and problems for Chapter 6 259

Chapter 7

Environmental impact and opportunities 261

7.1 7.2 7.3 7.4

Local and regional air quality 261 Benefits of district cooling 264 Climate change 265 Environmental opportunities – summing up 268 Study questions and problems for Chapter 7 269

Chapter 8

Heat and cold distribution technology 271

8.1 8.1.1 8.1.2 8.1.3 8.1.4 8.2 8.3 8.4

Historical development of heat distribution technology 271 First generation: Steam distribution 272 Second generation: Hot water distribution inside ducts 277 On the way to third-generation heat distribution technology 280 The third generation of heat distribution technology 283 Joints 288 Valves 289 Durability and methods of laying rigid pipes 295

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8.4.1 8.4.2 8.4.3 8.4.4 8.5 8.6 8.7 8.8 8.9 8.10 8.11 8.12

S tress-based design of carrier pipes of rigid, bonded pipe assemblies 295 Solid mechanics of restrained thermal expansion 299 Pipe-laying methods 303 Strain- and fatigue-based design of carrier pipes 307 Insulation foam and jacket pipes 314 Insulation sizing 322 Underground installation of rigid pipes 327 Flexible pipes 333 Overland pipes, pipes in tunnels, and pipes inside houses 339 Number of pipes in parallel 341 Cold carrier distribution 344 Water chemistry 351 Study questions and problems for chapter 8 357

Chapter 9

Substations 359

9.1 9.2 9.3 9.4 9.5 9.6 9.6.1 9.6.2 9.6.3 9.6.4 9.7 9.7.1 9.7.2 9.7.3 9.7.4 9.8 9.8.1 9.8.2 9.8.3 9.8.4 9.8.5 9.9 9.10

The substation concept 359 Desired temperature performance 363 Hydraulic separation 365 Examples of detailed layouts 370 Cascading 375 Selection of equipment 379 Heat exchangers 379 Valves and controls 381 Hot water storage tanks 385 Testing the equipment 389 Sizing of equipment 390 Overall considerations 390 Heat exchangers 393 Hot water storage tanks 398 Control valves 399 Adapting hydronic space heating systems 402 Energy saving measures 402 Elimination of recirculation and three-way valves 403 Problematic night set-backs 404 Optimised radiator flow rate and supply temperature 406 Single-pipe hydronic heating systems 408 District cooling substations 409 Metering in substations 416 Study questions and problems for Chapter 9 429

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Content Chapter 10 System functioning

431

10.1 10.1.1 10.1.2 10.1.3 10.1.4 10.1.5 10.2 10.3 10.3.1 10.3.2 10.3.3 10.3.4 10.3.5 10.4 10.5 10.6 10.6.1 10.6.2 10.6.3 10.6.4 10.6.5 10.6.6 10.6.7 10.7 10.8 10.8.1 10.8.2 10.8.3 10.9 10.9.1 10.9.2 10.9.3 10.10

Grid structures and maps 431 Heat density 431 Typical growth structures 433 Typical network structures 434 Developed network structure 436 Regional district heating systems 438 Heat and cold distribution 440 Flow distribution 440 Pressure drop 441 Pumping power 445 Pressure head gradients and pressurisation 447 Pressure surges 454 Carrier pipe sizing and choice of flow velocity 456 Temperature levels 462 Heat demand and load control 469 Grid control and four operating modes 472 Central maximum supply temperature control 474 Local minimum supply temperature control at the grid periphery 474 Central and local maximum pressure control 474 Central and local minimum pressure control 475 Four operating modes 475 System responses to altered demand conditions 477 Dynamic load responses 479 Heat supply from multiple sources 481 System monitoring 483 Short term planning 484 System supervision 485 Documentation and analyses 486 Reliability and availability issues 487 Reliability level 487 Operating problems 489 Maintenance 491 Development of system functioning 494 Study questions and problems for Chapter 10 497

Chapter 11

Economics and planning 499

11.1 11.1.1

Cash flow based profitability analysis 501 Present value and the Net Present Value decision rule 502

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11.1.2 11.1.3 11.1.4 11.2 11.3 11.4 11.5 11.6 11.7 11.8 11.9

I nvestment periods and hurdle rates in district heating 504 Profitability in existing operations 505 Valuation of incremental investments 506 Allocation of synergy benefits 506 Heat supply optimisation 513 Distribution costs 518 Extension planning 525 Price models 529 Heat supply costs versus local energy efficiency measures 533 Economy-of-size 536 District cooling 537 Study questions and problems for chapter 11 538

Chapter 12 District heating and cooling development

12.1 12.2 12.3 12.3.1 12.3.2 12.3.3

District heating 541 District cooling 547 Future district heating and cooling 552 Structure definition 553 Identification 558 Adaptation 559 Study questions and problems for chapter 12 560

Chapter 13 Organisation

13.1 13.2 13.3

561

Legislation 561 Market rules 562 Ownership 566 Study questions and problems for Chapter 13 568

Chapter 14 Information sources

14.1 14.2 14.3 14.4 14.5 14.6 14.7

541

569

Textbooks 569 Handbooks 570 Journals 571 Conferences 573 Statistics 573 Trade associations 576 Research programs 576

Index 579

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Preface

Despite its existence for more than a century and despite its many valuable merits, district heating and cooling is still a niche technology in a global context. No doubt, this has contributed to the fact that the body of literature on the subject is not very large compared to what has been written on other energy technologies. Textbooks and handbooks have only been written in national languages such as Russian, Polish, Finnish, German, Danish, and Swedish, because of high penetration rates of district heating in these language areas. Very few books have been published in English, since district heating and cooling is a minor technology in both USA and United Kingdom. To our knowledge, there is no work, especially not in the English language, which addresses the subject in the comprehensive, international, and updated way we now have tried to do. This book has been developed from the experience we have gained during our work with education, research, development, management, and consulting for more than 30 years. Our first district heating textbook was published in Swedish in 1993. When writing this second edition in both English and Swedish, we have tried to consider much valuable feedback and many comments throughout the years from students, engineers, managers, and researchers. We have also obtained valuable input concerning revision from our own use of the first edition in university and external lectures. We have a rather broad range of readers in mind. Our main target groups are district heating engineers, university students of engineering, and employees at district heating companies in general. We will be happy if urban planners, economists, policymakers and others interested in the topic find that this book provides tangible and useful information about district heating and cooling. Especially the introductory Chapters 1–3 and the concluding chapters 11–13 do not require detailed previous knowledge of a technical nature. Readers who study the whole text are assumed to possess some knowledge of basic engineering subjects, thermodynamics in particular.

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Preface

Those who are already district heating and cooling specialists will surely find parts of the text elementary. But it is our experience that even among such professionals there is often a lack of a full understanding of all aspects of the subject. Where district heating and cooling has been taught at universities, it has often been within the context of a specific HVAC or power plant curriculum, rather than in a comprehensive way considering district heating and cooling in its own right. District heating and cooling is an interdisciplinary technology containing elements from many general technologies and methodologies as combustion, heat transfer, piping, marketing, billing etc. Our mission has been to provide basic introductory knowledge about aspects typical of district heating and cooling, which is very vital for a basic understanding of, or very unique for, this niche technology. In providing primarily basic knowledge, we sometimes omit detailed and specialised knowledge because of the limited number of pages at our disposal. In order to satisfy the most interested and advanced readers, we end every section with a combined reference and literature list containing articles, reports, and books about the subject treated in the section. Thus, the book becomes also a structured subject oriented guide to the existing district heating and cooling literature. These lists are sorted by age for giving information to a reader about the division between old and new literature. Our own district heating and cooling knowledge has been gained from Scandinavian practices with which we ourselves have been working. For the first edition, we had an ambition of broadening the context to include experience from other nations. We follow up on this ambition in this second edition primarily by trying to attain a European, and sometimes a global, perspective. However, many examples inevitably still refer to Scandinavian experiences. We hope that non-Scandinavian readers, who work in other national contexts, will accept and appreciate these exemplifications. Where differing national engineering practices do exist, and where engineers working professionally within the subject hold differing views, we have tried to take care to present these differing views in a balanced and fair way. Sometimes divergence will even help highlight important issues. District cooling was briefly mentioned in the first edition. We have now extended the book’s content with essential district cooling information. But we have not included a separate district cooling chapter in the book. Instead, because of the great similarities between district cooling and district heating, and since most equations and methods are the same, we have integrated district cooling into each chapter. Sometimes, the only difference is the temperature of the water circulating in the pipes. 10

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Preface

In our writing, we have adhered to a tradition of how to write an academic textbook rather than a practical handbook or manual. The practical engineer may be disappointed that we do not always present hands-on advice about which options to choose, but we hope that all readers will be provided with added insight, in addition to being informed. Normative practical advices and instructions can be found, for instance, in national standards or guidelines issued by various national district heating and cooling associations. An overall ambition of the book is that it should contribute to a more general appreciation of the benefits and the potential of district heating and cooling, so that this technology can more fully play a role in solving pressing environmental problems and in promoting the security of energy supplies in a world that is not always stable. Svend Frederiksen was the principal author of Chapter 6–9 and we shared the responsibility for Chapter 10, while Sven Werner had the main responsibility for the remaining chapters. Finally in this preface, we want to acknowledge all the support we have received while writing this textbook. First, we acknowledge the financial support from the Swedish District Heating Association with Erik Larsson as project coordinator. Without this valuable contribution, this second edition of the textbook would have been neither written nor printed. Second, we appreciate supporting contributions in Section 11.1 from Anders Sandoff at Gothenburg University by providing the whole section, in Chapter 9 and Section 10.8 from Janusz Wollerstrand at Lund University, in Chapters 4 and 5 from Daniel Nilsson with European contour maps, in Chapter 12 from Urban Persson at Halmstad University with maps showing the locations of European district heating and cooling systems, and from Henrik Gadd and Mei Gong at Halmstad University for many study questions and exercise examples. Third, valuable feedback came from an international reference group (Robin Wiltshire, Chris Snoek, Lars Gullev, Kari Sipilä, and Martin Achmus), from a Swedish reference group (Pekka Kuljunlahti, Patrik Holmström, Thomas Lummi, and Conny Håkansson), and from a number of persons whom we specifically wish to mention: Tord Torisson and Marcus Thern (Chapter 6); Sture Andersson, Jan Eriksson, Tommy Gudmundson, Peter Randløv, and Ingo Weidlich (Chapter 8); and Bo Frank and Robert Eklund (Chapter 9). Fourth, we thank Anders Östlund and Lars-Inge Persson at Öresundskraft for permission to use heat and cold load profiles from the Öresundskraft district heating and cooling systems. Fifth, we thank the following persons for permission to use their diagrams in the book: Sabine Froning at Euroheat & Power for use of diagrams from Ecoheatcool and Ecoheat4EU (two IEE projects), Gunnar Peters at Borås Energy & Environment for sharing some

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Preface

of their performance indicators, Leif Breitholtz at FVB Sweden for sharing insights from their consulting services, and Dick Magnusson at Linköping University for use of his nice network growth map for Stockholm. Sixth, we would like to thank Lennart Thörnqvist, Patrick Lauenburg, Christopher Paitazoglou, and Janusz Wollerstrand for providing general feedback and performing proof-reading, as well as many of the participants of the August 2012 international PhD course about district heating and cooling for finding several typing errors in the proof edition. Seventh, we appreciate the valuable advice from Jens Fredholm and other staff at Studentlitteratur. We naturally take full moral responsibility for any errors that may occur in the text. We do not, however, take any legal responsibility for any consequences of such errors, omissions, or the like. Thus, the book is intended for general information only. On a number of occasions we make reference to standards and other literature that the reader who is in need of practical ‘hands-on’ advice may consult. A number of additional persons gave also feedback and advice. Among them are representatives of utility companies and manufacturers to whose products reference is made in the text. Holte (Denmark) and Steninge (Sweden) in December 2012. Svend Frederiksen Professor at Lund University

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Sven Werner Professor at Halmstad University

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3 Energy, heat, and cold markets

efficiencies in thermal power plants would reduce considerably the energy supply for electricity generation and the associated carbon dioxide emissions. For final consumption, 10.2 EJ of electricity and 2.4 EJ of heat (mainly district heat) were delivered. These quantities correspond to 20% and 5%, respectively, of the total final energy consumption of 51.2 EJ. The third stacked bar contains the estimated final end use of heat for various purposes, electricity for power and lighting, and, finally, the mechanical power required for overcoming friction, changing speeds or altitudes, and meeting air resistance in transportation. Heat from fuels and district heating amounted to about 17 EJ, while electricity use was 10.0 EJ, because some electricity was used for transportation purposes. However, electricity for heat use is not transferred to the heat part of the end use since reliable statistics are lacking. However, according to (Bertoldi 2007), the total electricity for heat use can be estimated at about 1.4 EJ in buildings alone. Also, in this third stacked bar, the heat losses were huge (17.1 EJ) from high-temperature industrial processes, heat generation in local boilers, and conversion losses from all vehicle engines. The fourth stacked bar shows the conceivable and possible situation if all end use is cut equally by 30% through the implementation of energy efficiency measures. The new, third, heat loss portion at the top of the stacked bar represents all the heat losses that are associated with this 30% end use reduction. This new heat loss portion is considerably larger than the actual 30% end use reduction itself, since the total heat loss reduction also includes the central and local conversion losses associated with the 30% end use reduction. The total final energy consumption from the second stacked bar in Figure 3.2. is divided into four main sectors (industry, transport, others, and non-energy) in Figure 3.3. The other sectors include the agricultural, residential, public, and commercial sectors (omitting the industry, transport, and energy sectors). The non-energy use includes oils for lubrication and the entire input to the petrochemical industry for various plastics. The energy demand in the transport sector is beyond the scope of the present textbook, although major heating and cooling demands appear in this sector. Most of the transportation heating demands in cold countries are met by retrieving conversion heat losses from engines (similar to combined heat and power). Some minor heat demands during non-operation are met directly by using electricity or fuels in car and engine heaters. All transportation cooling demands are met by extra fuel supplies to engines feeding small mechanical chillers. In theory, it would be possible to generate cold in small absorption chillers using the high-temperature engine conversion heat losses.

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3 Energy, heat, and cold markets EJ 80 70

Heat losses, central conversion (energy sector)

60 50 40

Heat losses, central conversion (energy sector)

Heat losses, end use inefficiency

Heat losses, local conversion (consumers)

Heat losses, central conversion (energy sector) Heat losses, local conversion (consumers)

Combustible renewables and waste Solar/wind/other Geothermal Hydro Nuclear Natural gas Petroleum products Coal and coal products Non-Energy Use

Transportation

Electricity Heat

0 A. Total Primary Energy Supply (IEA statistics)

B. Total Final Consumption (IEA statistics)

C. Total End Use (estimated)

D. Total Efficient End Use (estimated with 30% inefficiency)

Figure 3.2 The energy balance in four steps for the European Union during 2007. Data source: IEA 2009, complemented with author’s own estimations.

EJ 25 Combustible renewables and waste

Solar/wind/other Geothermal

Natural gas 10

Petroleum products Coal and coal products

Electricity 0

Heat Total Industry Sector

Total Transport Sector

Total Other Sectors

Non-Energy Use

Figure 3.3 The final consumption of energy in the European Union during 2007 divided into four different end use purposes. Data source: IEA 2009, complemented with author’s own estimations.

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3 Energy, heat, and cold markets

The major conclusion from this simple energy balance analysis is that the huge total heat losses correspond to more than half of the total primary energy supply. A future European energy system must reduce these losses in order to increase overall energy efficiency, reduce carbon dioxide emissions, and increase the security of supply. The heat sector in general and the district heat sector in particular could contribute to meeting these objectives by using existing heat losses in the energy system to satisfy local heat demands of the European heat market. Literature Bertoldi P & Atanasiu B, Electricity Consumption and Efficiency Trends in the Enlarged European Union. European Commission – Joint Research Centre, Institute for Environment and Sustainability. Report EUR 22752. Ispra 2007. IEA, Energy Balances for OECD and Non-OECD Countries. International Energy Agency, Paris 2009. Werner S, The European Heat Market. Ecoheatcool project, WP1 report. Brussels 2005. Available at www.euroheat.org/ecoheatcool

3.2 Heat

markets

Heat demands appear mainly in the industrial, residential, service, and agricultural sectors. These heat demands have various causes in each sector. In the industrial sector, heat is an essential component in many manufacturing processes. Heat makes it possible to produce glass, steel, paper, etc. But this heat must have a high temperature in order to fulfil its purpose in industrial processes. Industry also requires heat for drying products and providing their premises with comfortable indoor temperatures. These examples show that industry also has medium and low temperature demands. In the residential and service sectors, heat is used for maintaining a comfortable indoor temperature during cold seasons (space heating). Heat is also needed in the residential sector for preparation of domestic hot water, used mainly for sanitary purposes. In the agricultural sector, heat is required for drying agricultural crops and for some space heating of animal accomodations. Normally, the heat required for meeting the heat demands is obtained by using fuels in nearby boilers. Therefore, heat markets are closely related to fuel markets. Hence, district heat is delivered to heat customers in competition with fuel for use in their own boilers. It is possible to quantify country and sector heat markets by aggregating the amounts of heat obtained from fuels burned in boilers with the amounts of district heat and electricity used for heating. However, we do not have a fully developed heat market with

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3 Energy, heat, and cold markets

established actors supplying price information, heat contracts, and financial instruments such as is the case with the international fuel and electricity markets. Therefore, the term ‘heat market’ is used as a label for describing the magnitude of heat demands in various community sectors. It is in this market that the suppliers of district heating must look for their customers. The conditions of the heat market must be met by district heating providers if they want to develop their heating businesses. The composition of the EU27 heat market for the residential and service sectors during 2008 is estimated in Figure 3.4 by omitting conversion losses and non-heat use from the third stacked bar in Figure 3.3. This heat market is currently dominated by fossil fuels, which make up two-thirds of it. Examples of the development of market shares of various heat supplies in national heat markets for buildings are given in Figure 3.5 for Sweden, in Figure 3.6 for Finland, and in Figure 3.7 for Denmark. The various typical heat supplies presented are somewhat different for the three countries due to the availability of statistical input. The three examples show how the market shares for district heating have grown considerably during recent decades. This growth has mainly replaced the use of fossil fuels in local boilers for heating. The three figures show also that these countries have managed to obtain market shares of around 50% and far beyond the EU27 average market share of 12% presented in Figure 3.4.

EU27 during 2008, Origin of heat supply for heat demands in residential and service sector buildings Total heat supply was 11.5 EJ, not including indirect heat supply from all indoor electricity use Coal and Coal Products 3%

Heat 12% Electricity 12%

Petroleum Products 19%

Combustible Renewables 9% Solar/Wind/Other 0% Geothermal 0%

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Natural Gas 45%

Figure 3.4 Composition of the origin of the heat supply to residential and service sector buildings in EU27 during 2008 with each part expressed as heat after energy conversion. Heat denotes mainly heat from district heating systems. Total heat supply was 11.5 EJ, not including indirect heat supply from all indoor electricity use. Data sources: IEA energy balances for 2008 complemented with some external estimation.

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3 Energy, heat, and cold markets Market share (%), Sweden 90 Fuel oil boilers

80 70

District heating 60 50 40

Others, such as firewood and natural gas boilers

Electric heating, including input electricity for heat pumps

30 20 10 0 1955

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

Figure 3.5 Market shares in accordance with net heat demands (except for local heat pumps) for various heat supplies to the Swedish residential and service sectors since 1960. Data source: Statistics Sweden and some older sources.

Market share (%), Finland 90 80

Biomass boilers

Fossil fuel boilers

60 District heating

50 40 30 20 10 0 1955

Electric heating 1960

1965

1970

1975

1980

1985

Heat pumps 1990

1995

2000

2005

2010

2015

Figure 3.6 Market shares in accordance with net heat demands for various heat supplies to the Finnish residential and service sectors since 1960. Data source: Statistics Finland.

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3 Energy, heat, and cold markets Market share (%), Denmark 90 80 70 60 District heating

50 40 30

Fossil fuel boilers 20

Renewables

10 0 1955

Electric heating 1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

2010

2015

Figure 3.7 Market shares in accordance with net heat demands for various heat supplies to the Danish residential and service sectors since 1960. Data source: Danish energy balances from Energistyrelsen at www.ens.dk.

District heating systems occur in urban areas for mainly to cover lowtemperature heat demands in buildings. It is essential to understand the nature of these heat demands when planning and operating district heating systems. Therefore, this will be the topic in the next chapter. 3.3 Cold

markets

Cold can be defined as a heat quantity to be removed to create a temperature lower than the ambiant temperature. Hence, cold is generated and supplied for various uses by heat removal in order to reduce the temperature of an object to a required temperature. The global cold market contains several different areas requiring cold supply • Space cooling: For creating comfortable indoor climates for people in

buildings, cars, buses, trains, airplanes, mines etc (also known as air conditioning). • Food supply chain: For preserving food quality from supply to consumption by cold stores, refrigerated transports, refrigerators, and freezers. 36

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3 Energy, heat, and cold markets

• Industrial processes: For securing the product quality in computer

centres, breweries, dairies, vineries etc.

• Other special uses: Soil freezing in civil engineering, creating ice in

ice rinks, obtaining liquid methane for LNG transports, cryogenic uses below 120K, etc.

District cooling is normally used for meeting space cooling demands in buildings by heat removal. Hence, this section will mainly focus on space cooling conditions and markets. The corresponding cold demands in buildings are featured in Section 4.6, while cold loads associated with district cooling will be presented in Section 5.7. The purpose of space cooling is to remove heat in order to maintain a comfortable indoor temperature during warm seasons. This purpose can be met in each room by individual cooling devices (RAC – room air conditioners), by central cooling (CAC – central air conditioning) in a building, or by district cooling. Individual cooling means that the cold is generated locally in each room, while central cooling denotes a system where the cold is generated in one or more places within a building. When district cooling is used, the cold is generated centrally for many buildings and the cold is distributed to the customer buildings through a pipe network. Individual cooling devices are normally purchased at a rather low cost, but have higher operating costs, since their energy efficiencies are low. Central cooling includes an internal distribution system inside a building, giving a somewhat higher initial investment cost. But the operating cost for central cooling is lower than for individual cooling, since the energy efficiencies are higher. At a particular volume of cold demand, the overall cost for central cooling becomes lower than for individual cooling. The same relationship is applicable when central and district cooling are compared, with district cooling having the higher investment costs and lower operating costs. So, if a small proportion of the floor space in a building requires cold supply, individual cooling is recommended. But if the whole building requires cold supply and the building is situated in a dense downtown or commercial area, district cooling is usually a viable option. The lower energy efficiency for individual and central cooling has an impact on the current primary energy supply and carbon dioxide emissions (Grignon-Massé 2011) and on the future viability of district cooling (Thornton et al. 2008). Internationally, the USA and Japan are examples of countries with a very high use of space cooling, as presented in Figure 3.16. The cooling saturation rates are currently approaching 90%. The figure also reveals that central cooling

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3 Energy, heat, and cold markets USA & Japan: Cooling saturation rates (%) 100 90 80 70

USA Residential, Total cooling USA Residential, Central cooling USA Commercial, Total cooling USA Commercial, District cooling Japan Residential, Room AC

60 50 40 30 20 10 0 1950

1960

1970

1980

1990

2000

2010

2020

Figure 3.8 Cooling saturation rates for buildings in the USA and Japan expressed as proportion of all households or total commercial floor space having access to some space cooling. Sources: EIA 2011, USCB 2011 and Japan Statistics 2011.

China & Japan: Cooling saturation rates (RAC Units per 100 households) 250 Japan, All Households 200

150

100 China, Urban Households 50 China, Rural Households 0 1985

1990

1995

2000

2005

2010

Figure 3.9 Cooling saturation rates for urban and rural households in China and all households in Japan expressed as the number of residential air conditioners installed per 100 households. Sources: China Statistics 2011 and Japan Statistics 2011.

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is dominant in comparison to individual cooling in US residential buildings, but that the opposite was the case when air conditioning was introduced and expanded rapidly during the 1960s and 1970s. Thus, short-term investments in individual cooling were important in order to meet the initial cooling demands. But, for repeated long-term investments in new cooling devices or in new buildings, more energy-efficient central cooling is appreciated and chosen. The frequent use of air conditioning in the USA has really supported development of the southern Sun Belt states during the second half of the twentieth century. This history behind the expansion of air conditioning is told by (Cooper 1998) and (Ackermann 2002). However, this massive use of air conditioning in the USA has changed social behaviour, resulting in more hours spent indoors and a reduction of outdoor activities. An excellent critical analysis of the role that air conditioning plays in contemporary American life is provided by (Cox 2010). China is currently the largest national air conditioning equipment market in the world. During 2010, the total turnover of equipment sales reached 21 billion US$, representing 27% of the world market. According to Figure 3.9, the annual growth rates for urban households have been very high during the last 10–15 years. Chinese urban areas have now about half of the Japanese saturation rate for individual cooling devices in residential buildings. In Europe, the cooling saturation rates are much lower than in the USA and Japan, mostly because of a milder summer climate in western and northern Europe, but also from the lack of a tradition of using air conditioning. In 1990, only 5% of the French service sector buildings were equipped with air conditioning. The corresponding figure for the English and Welsh service sector buildings was 6% in 1994. (Dalin et al. 2005) estimated the cooling saturation rates for EU15 to be 27% for service sector buildings and 5% for residential buildings during 2000, giving a total annual cooling demand of 470–540 PJ. But the annual growth rates are now very high also in Europe, especially in the Mediterranean countries. The annual sales of individual cooling devices in Europe increased from 1.6 to 3.5 million units between 1996 and 2005, according to (Grignon-Massé et al. 2011). One explanation for this growth has been the European summer heat wave of 2003, which resulted in the deaths of many people from the extremely hot weather. An estimation made by (Adnot et al. 2003) foresaw an increase of 120% in space cooling use by floor area in Europe between 2000 and 2020. More use of space cooling in Europe will substantially increase national electricity demands during summer. It is already very common that electricity design loads in downtown or commercial areas appear, also in Northern

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Europe, during summer. Earlier, these design loads appeared during winters because of greater lighting needs and some electric space heating. District cooling is mostly used in downtown or commercial areas and delivers cold almost exclusively to service sector (commercial) buildings. Among US commercial buildings, district cooling had a market share of 4% in 2003. The corresponding figure for all EU15 buildings was almost 2% in 2000, according to (Dalin et al. 2005). In Sweden, the service sector market share of district cooling was 8% during 2006, giving a high relative market share of almost 60% for all cooling demands, according to (Andreasson el al. 2009). In Paris, the Climespace district cooling company delivers district cold to 5 million m2, giving them an 8% market share for all 60 million m2 of service sector buildings in the city. The corresponding market share for the Stockholm district cooling system is about 25%. Literature Cooper G, Air-Conditioning America – Engineers and the Controlled Environment 1900–1960. John Hopkins University Press, Baltimore 1998. Adnot J et al, Energy Efficiency of Room Air-conditioners (EERAC). SAVE Contract 4.1031/D/97.026. Paris 1999. Ackermann ME, Cool Comfort – America’s romance with air-conditioning. Smithsonian Books, Washington DC 2002. Adnot J et al, Energy Efficiency and Certification of Central Air Conditioners (EECCAC). SAVE project 4.1031/P/00–009/2000. Volume 1–3. Final report. Paris 2003. Santamouris M et al, Cooling the Cities. Les Presses, Ecole des Mines. Paris 2004. Dalin P, Nilsson J & Rubenhag A, The European cold market. Work Package 2 of the Ecoheatcool project. Brussels 2005. Available at www.euroheat.org/ ecoheatcool Larsen J, Setting the Record Straight: More than 52,000 Europeans Died from Heat in summer 2003. Earth Policy Institute, July 2006. Available at www.earth-policy.org/plan_b_updates/2006/update56 Thornton R, Miller R, Robinson A, Gillespie K, Assessing the actual energy efficiency of building scale cooling systems. IEA-DHC implementing agreement report 8DHC-08–04. 2008 Andreasson M, Borgström M, Werner S, Värmeanvändning i flerbostadshus och lokaler (Heat use in Swedish multi-dwelling houses and in Swedish service sector buildings). Fjärrsyn report 2009:4. Stockholm 2009.

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Cox S, Losing Our Cool – uncomfortable truths about our air-conditioned world (and finding new ways to get through the summer). New Press, New York 2010. BSRIA, World air conditioning on the road to success. Press release no 21–11. Bracknell 2011. Grignon-Massé L, Rivière P, Adnot J, Strategies for reducing the environmental impacts of room air conditioners in Europe. Energy Policy 39(2011), 2152–2164. USCB, American Housing Survey. Extracts for various years between 1960 and 2009. US Census Bureau. Available at www.census.gov and downloaded during 2011. EIA, Commercial Building Energy Consumption Survey. Extracts for various years between 1986 and 2003. US Department of Energy, Energy Information Administration. Available at www.eia.gov/emeu/cbecs/contents.html and downloaded during 2011. China Statistics, China Statistical Yearbook. Extracts for various years between 1990 and 2009 concerning relative saturation of air conditioners in urban and rural household. Available at www.stats.gov.cn/english/ and downloaded during 2011. Japan Statistics, National Survey of Family Income and Expenditure: Major Durable Goods Data. Extracts for various years between 1989 and 2009. Available at www.stat.go.jp/english/index.htm and downloaded during 2011.

Study questions for Chapter 3 1 What are the four basic parts of an energy system? 2 The primary energy supply is the energy input to the energy system. Where and in which form does the whole energy output leave the energy system? Your answer should agree with the first law of thermodynamics. 3 Where in the energy system can we find the highest relative heat losses? 4 Which are the three most important customer segments for district heating? 5 What were the market shares for district heating in 2008 in the heat market for residential and service sector buildings in Denmark, Finland, Sweden, and EU27? 6 What is the main purpose of air conditioning?

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35 mm

Svend Frederiksen Sven Werner

District Heating and Cooling

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District Heating and Cooling Svend Frederiksen Sven Werner

Art.No 36005

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