3 Low Temperature District Heating

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Future low temperature district heating design guidebook

Final Report of IEA DHC Annex TS1. Low Temperature District Heating for Future Energy Systems

Li, Hongwei; Svendsen, Svend ; Gudmundsson, Oddgeir; Kuosa, Maunu; Rämä, Miika ; Sipilä, Kari ; Blesl, Markus; Broydo, Michael; Stehle, Markus; Pesch, Ruben; Pietruschka, Dirk; Huther, Heiko; Grajcar, Maria ; Jentsch, Andrej; Kallert, Anna; Schmidt, Dietrich ; Nord, Natasa; Tereshchenko, Tymofii ; Park, Peter Byung-Sik ; Im, Yong Hoon; Liu, Jie; Dag, Süleyman; Wiltshire, Robin; Bevilacqua, Ciro

Publication date: 2017

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Citation (APA): Li, H., Svendsen, S., Gudmundsson, O., Kuosa, M., Rämä, M., Sipilä, K., ... Bevilacqua, C. (2017). Future low temperature district heating design guidebook: Final Report of IEA DHC Annex TS1. Low Temperature District Heating for Future Energy Systems. International Energy Agency.

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International Energy Agency Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power

Annex TS1 Low Temperature District Heating for Future Energy Systems

FINAL REPORT FUTURE LOW TEMPERATURE DISTRICT HEATING DESIGN GUIDEBOOK Edited by Dietrich Schmidt and Anna Kallert Cover Images (from left to right): © Rakentaja.fi / Jarno Kylmanen © Logstor A/S © Technical Univerity of Denmark © Danfoss A/S International Energy Agency Technology Collaboration Programme on District Heating and Cooling including Combined Heat and Power

FUTURE LOW TEMPERATURE DISTRICT HEATING DESIGN GUIDEBOOK

Final Report of IEA DHC Annex TS1 Low Temperature District Heating for Future Energy Systems

Edited by Dietrich Schmidt and Anna Kallert

Published by: AGFW-Project Company Frankfurt am Main, Germany Operating Agent

Dietrich Schmidt Fraunhofer Institute for Wind Energy and Energy System Technology IWES Königstor 59 DE-34119 Kassel Germany Phone: +49 561 804 1871 E-mail: [email protected]

All property rights, including copyright, are vested in Fraunhofer IWES (Germany), Operating Agent for the DHC Executive Committee, on behalf of the Contracting Parties of the Interna- tional Energy Agency Technology Collaboration Programme on District Heating & Cooling. In particular, no part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of Fraunhofer IWES.

Published by: AGFW-Project Company Stresemannallee 30 DE-60596 Frankfurt am Main Germany

Disclaimer Notice: This publication has been compiled with reasonable skill and care. However, neither Fraun- hofer IWES nor the DHC Contracting Parties (of the International Energy Agency Technolo- gy Collaboration Programme on District Heating & Cooling) make any representation as to the adequacy or accuracy of the information contained herein, or as to its suitability for any particular application, and accept no responsibility or liability arising out of the use of this publication. The information contained herein does not supersede the requirements given in any national codes, regulations or standards, and should not be regarded as a substitute for the need to obtain specific professional advice for any particular application.

ISBN 3-89999-070-6

Participating countries in IEA DHC: Canada, Denmark, Finland, Germany, Republic of Korea, Norway, Sweden, United Kingdom and the United States of America. Further information about the IEA DHC programme may be obtained from

www.iea-dhc.org

4 TABLE OF CONTENTS

Executive Summary 6 1 Preface 8 1.1 International Energy Agency 1.2 Technology Collaboration Programme on District Heating & Cooling (DHC) 1.3 The IEA DHC Annex TS1 1.4 Operating Agent: 2 Introduction 12 2.1 Background and motivation 2.2 Scope and objectives 2.3 Performance of low temperature district heating on a community scale 2.4 Main objective and layout of the report 3 Low Temperature District heating 16 3.1 What is low temperature district heating? 3.2 A sustainable and flexible approach to the energy supply of communities 3.3 An economically efficient low temperature heating energy supply 4 District heating and Cooling Technologies 17 4.1 Introduction 4.2 District Heating Pipes 4.3 Energy Efficient District Heating Network 4.4 Domestic hot water supply 4.5 Control of space heating 4.6 Integration of small scale decentralized heat sources 5 Interfaces and communities 35 5.1 Introduction 5.2 Predicting DH demand and future development 5.3 Distribution and development issues 5.4 Optimization, interaction, and energy measurement 5.5 Pricing and business models 6 Calculation Tools for District Heating Systems 42 6.1 Introduction 6.2 Description of Planning Tools for District Heating 6.3 Evaluation of Planning Tools for District Heating 6.4 Summarizing Evaluation of DH Planning Tools 6.5 Easy District Analysis (EDA) – A Simplified Tool 7 Application of Low Temperature District Heating to Community Case Studies 61 7.1 Introduction 7.2 Innovative community case studies 7.3 Summary and Conclusions from the Case Studies 8 Conclusions 78 References 81 List of Abbreviations 89 Appendix A: National Standards and guidelines on domestic hot water of IEA DHC participating countries 90 Appendix B: IEA DHC Annex TS1 Participants 93 Appendix C: Additional Information from IEA DHC Annex TS1 95 www.iea-dhc.org 5 EXECUTIVE SUMMARY The building sector is responsible for more than one third of the end energy consumption of societies in industrialized countries and produces the largest amount of greenhouse gas emissions (GHG) of all sectors. District heating can contribute significantly to a more efficient use of energy resources as well as better integration of renewable energy into the heating sector (e.g. geothermal heat, solar heat, heat from biomass combustion or waste incineration), and surplus heat (e.g. industrial waste heat). The more efficient use of all energy resources and the use of renewable energy are measures which lead to a reduced utilization of fossil energy, and thereby a reduction of GHG emissions to fulfill the set climate goals. Low temperature district heating is a heat supply technology for efficient, environmental friendly and cost effective community supply. In comparison to conventional district heating, the network supply temperature is reduced down to approximately 50 °C or even less. Within this context, low temperature district heating offers prospects for both the demand side (community building structure) and the generation side (properties of the networks as well as energy sources). Especially in connection with buildings that require only low supply temperatures for space heating, low temperature district heating offers new possibilities for greater energy efficiency and utilization of renewable energy sources, which lead to reduced consumption of fossil fuel based energy.

The IEA DHC Annex TS1 is a three year international research project which aims to identify holistic and innovative approaches to communal low temperature heat supply by using district heating. It is a framework that promotes the discussion of future but also existing heating networks with an international group of experts. The goal is to obtain a common development direction for the wide application of low temperature district heating systems in the near future.

As part of the project promising technologies for low temperature district heating application have been collected and identified to meet the goals of future renewable based community energy systems. Background materials and cutting edge knowledge on district heating pipe systems, network designs, hygienic domestic hot water preparation in low temperature supply schemes, space heating controls and the integration of small scale decentralized heat sources is provided in the report for designers as well as decision makers in the building and district energy sector.

The analysis of the future heat demand showed that the district heating would still be needed for most of the buildings in 2050, inducing that the low temperature district heating is a promising heat supply for the future and for many buildings. Considering that there is enough available heat from renewables and waste heat sources at the low temperature level, the low temperature district heating will be of high relevance in the future. For future development of the district heating and a high reliability of the low temperature district heating, statistical data and knowledge on the heat losses and how operation or temperature levels may contribute to the distribution losses are highly necessary.

For the identification of integral and innovative approaches to low temperature heat supply at municipal level, an overview of a number of existing evaluation methods is provided. The planning tools are assessed in seven categories: analytical approach, target group of users, level of detail, model type, demand categories, final energy consumption and used variables within the assessment. The evaluation of the collected tools has shown some promising approaches for low temperature district heating. However, none has been found to be fully appropriate for the objective of a simplified, holistic tool for the evaluation of low temperature district heating. By evaluating the selected planning tools for district heating schemes, requirements have been derived for the development of a simplified planning tool.

6 The so-called Easy District Analysis tool has been developed, based on the identified requirements for a simplified district heating planning tool. The intended target groups of the tool are urban planners and planners in utility companies. The tool is intended to be used in the pre-planning phase of a district energy system. The focus of the tool is on the evaluation of the impact of different grid temperatures and of different operation modes of district heating schemes. The assessment is based on the parameters primary energy consumption, carbon emissions and heat production costs.

In the description of different case studies innovative demonstration concepts as examples of success stories for communities interested in developing low temperature district heating systems are displayed. Demonstrated cases include the use of advanced technologies and the interaction between different components within the systems. Based on these experiences, principles and lessons learned in designing these systems are given. Measurement data from community projects are also used in validation of the models and tools developed. There were a total of eight case studies from Germany, Denmark, Finland, Norway and Great Britain. The district heating systems were of very different sizes, from smaller building groups to city wide systems. Taking into account the size of the supply area, the network lengths vary from 165 m to 140,000 m. The connected buildings were residential buildings of different sizes, and mostly low energy or passive houses. Sources of heat were solar collectors, heat pumps, combined-heat-and-power-plants, excess heat from industry or the systems were connected to a larger network close by with heat exchangers. The temperature levels recorded were typical for low-temperature systems, varying from 40 to 60 °C in supply and 25 to 40 °C in return. Savings and increased efficiencies were observed in every case studied.

The material collected and summarized in the presented guidebook show that low temperature district heating is a key enabling technology to increase the integration of renewable and waste energy for heating and cooling. More research and development work is needed to assess the practical and wider implementation of low temperature district heating schemes for various cases and locations. Especially ways to overcome the hindering reasons need to be identified. This supports more discussions to get low temperature heating systems built and in operation.

Low temperature district heating is one of the most cost efficient technology solutions to achieve 100 % renewable and GHG emission-free energy systems on a community level.

www.iea-dhc.org 7 1 PREFACE

1.1 International Energy Agency The International Energy Agency (IEA) was established in 1974 within the framework of the Organisation for Economic Co-operation and Development (OECD) to implement an international energy programme. A basic aim of the IEA is to foster co-operation among the twen- ty-four IEA participating countries and to increase energy security through energy conservation, development of alternative energy sources and energy research, development and demonstration (RD&D).

1.2 Technology Collaboration Programme on District Heating & Cooling (DHC) Established in 1983, the IEA Technology Collaboration Programme on District Heating & Cooling including Combined Heat and Power (IEA-DHC) brings countries together to research, innovate and grow district heating and cooling including CHP.

The IEA-DHC research programme addresses technical as well as policy issues aimed at low environmental impact. We select, manage and publish collaborative co-funded projects, collating and exchanging information on R&D projects between participating countries.

IEA-DHC programme control is vested in its Executive Committee, which comprises on official representatives from each participating country. The Executive committee maintains close links with Euroheat & Power and the International District Energy Association.

The Executive Committee closely cooperates with other IEA programmes. In particular the IEA-DHC is a member of the IEA’s Building Coordination Group, resulting in more knowledge sharing and planning of joint activities.

The world may be challenged by climate change, but countries can make district heating and cooling including CHP part of an integrated energy and environmental solution.

The IEA’s Technology Collaboration Programme on District Heating & Cooling has played a significant role in the DHC/CHP industry’s history and will play a vital role in its even brigh- ter future!

More information can be found at:

www.iea-dhc.org

8 To date, the following projects have been initiated by the IEA DHC Executive Committee (completed projects are identified by (*)):

1983-1987 / Annex I (*) 1987-1990 / Annex II (*) 1990-1993 / Annex III (*) 1993-1996 / Annex IV (*) 1996-1999 / Annex V (*) 1999-2002 / Annex VI (*) 2002-2005 / Annex VII (*) 2005-2008 / Annex VIII (*)

• New materials and constructions for improving the quality and lifetime of district heating pipes including joints - thermal, mechanical and environmental performance • Improved cogeneration and heat utilisation in DH networks • District heating distribution in areas with low heat demand density • Assessing the Actual Annual Energy Efficiency of Building-Scale Cooling Systems • Assessing the Actual Annual Energy Efficiency of Building-Scale Cooling Systems • Cost benefits and long term behaviour of a new all plastic piping system

2008-2011 / Annex IX (*) • The Potential for Increased Primary Energy Efficiency and Reduced CO2 Emissions by DHC • District Heating for Energy Efficient Building Areas • Interaction Between District Energy and Future Buildings that have Storage and Intermittent Surplus Energy • Distributed Solar Systems Interfaced to a District Heating System that has Seasonal Storage • Policies and barriers for District Heating and Cooling outside EU countries

2011-2014 / Annex X (*) • Improved maintenance strategies for district heating pipelines • Economic and Design Optimization in Integrating Renewable Energy and Waste Heat with Dis- rict Energy Systems • Towards Fourth Generation District Heating: Experiences with and Potential of Low Tempera- ture District Heating • Development of an Universal Calculation Model and Calculation Tool for Primary Energy Factors and CO2 Equivalents in District Heating and Cooling including CHP

2012-2016 / Annex TS1 • Low Temperature District heating for Future Energy Systems

2014-2017 / Annex XI • Transformation roadmap from high to low temperature district heating system • Plan4DE: Reducing greenhouse gas emissions and energy consumption by optimizing urban form for district energy • Smart use as the missing link in district energy development: a user-centred approach to system operation and management • Structured for success: Governance models and strategic decision making processes for de- ploying thermal grids

2017-2020 / Annex XII • Effects of Loads on Asset Management of the 4th Generation District Heating Networks • Methodology to evaluate and map the potential of waste heat from industry, service sector and sewage water by using internationally available open data • Integrated Cost-effective Large-scale Thermal Energy Storage for Smart District Heating and Cooling • Stepwise transition strategy and impact assessment for future district heating systems www.iea-dhc.org 9 1.3 The IEA DHC Annex TS1 DHC Annex TS1 was a three year international research project. The IEA DHC Annex TS1 aims to identify holistic and innovative approaches to communal low temperature heat supply by using district heating. It is a framework that promotes the discussion of future but also existing heating networks with an international group of experts. The goal is to obtain a common development direction for the wide application of low temperature district heating systems in the near future. District cooling can also be integrated into the activities but is not the focus. The gathered research which is going to be collected within this Annex should contribute to establishing DH as a significant factor for the development of 100 % renewable energy based communal energy systems in practice. By connecting the demand side (community/building stock) and the generation side (different energy sources which are suitable to be fed in the DH grids), this technology provides benefits and challenges at various levels. The activities are strongly targeted at DH technologies and the economic boundary conditions of this field of technology.

Figure 1-1 Structure of the IEA DHC Annex TS1

Further information about the project can be found on the internet under:

www.iea-dhc.org

1.4 Operating Agent: This international cooperation project has been coordinated by the operating agent

Dietrich Schmidt Fraunhofer Institute for Wind Energy and Energy System Technology (IWES) Königstor 59 DE-34119 Kassel Germany [email protected]

10 This Guidebook of DHC Annex TS1 is the result of a joint effort of many experts from various countries. We would like to gratefully acknowledge all those who have contributed to the project by taking part in the writing process and the numerous discussions. This coope- rative research work is funded by various national sources and from industry partner. The authors would like to thank for the given financial support. A list of the participants within Annex TS1 and their corresponding countries can be found in the Appendix B. All participants from all countries involved have contributed to the guidebook. However, the following annex participants have taken over the responsibility of writing the chapters:

Dietrich Schmidt Editor, operating agent and Subtask E coordinator, contributed to almost all chapters, especially chapters 1, 2, 3, 7 and 8

Anna Kallert Editor, contributed to almost all chapters, especially chapters 4, 5, 6 and appendix A

Markus Blesl Subtask A coordinator, especially chapter 6

Hongwei Li Contributed to almost all chapters, especially chapters 3, 4, 6 and 7.2

Svend Svendsen Subtask B coordinator, especially chapters 3, 4, 7.2 and 8

Natasa Nord Subtask C coordinator, especially chapters 6 and 7.2

Kari Sipilä Subtask D coordinator (2012-2015), especially chapter 7

Miika Rämä Subtask D coordinator (2016), especially chapter 7

Oddgeir Gudmundson Contributed to almost all chapters, especially 3, 4, 5 and 8

Maunu Kuosa especially chapters 4.3 and 4.5

Michael Broydo especially chapter 6

Markus Stehle especially chapter 6

Ruben Pesch especially chapter 7.2

Dirk Pietruschka especially chapter 7.2

Heiko Huther especially chapter 3 and 8

Andrej Jentsch especially chapter 1, 2, 3 and 8

Tymofii Tereshchenko especially chapter 6 and 7.2

Ciro Bevilacqua especially chapter 7.2

Gunnar Lennermo (guest) chapter 4.6

This report is a summary of the conducted work of DHC Annex TS1. The full and extended versions of the various detailed subtask reports are freely available on the internet (www.iea-dhc.org). www.iea-dhc.org 11 2 INTRODUCTION

2.1 Background and motivation the system. The components of the DH Sys- tem, such as the pipelines, the operational The building sector is responsible for more structures and the substations, are an inte- than one third of the end energy consump- gral part of the overall system optimization. tion of societies and produces the largest For overall system optimization it is therefo- amount of greenhouse gas emissions (GHG) re necessary to take into account the buil- of all sectors. This is due to the utilization of ding stock, the structure of the considered combustion processes of mainly fossil fuels community, energy infrastructure and the to satisfy the heating and cooling demand heat generation facilities for the assessment. (the cooling demand is usually satisfied by The IEA DHC Annex TS1 aims to identify use of electricity form combustion proces- holistic and innovative approaches to com- ses) of the building stock. District heating munal low temperature heat supply. It is a (DH) can contribute significantly to a more framework that promotes the discussion of efficient use of energy resources as well as future heating networks with an internatio- better integration of renewable energy into nal group of experts. The goal is to obtain the heating sector (e.g. geothermal heat, so- a common development direction for the lar heat, heat from biomass combustion or wide application of low temperature district waste incineration), and surplus heat (e.g. heating systems in the near future. District industrial waste heat). The more efficient cooling can also be integrated into the pro- use of all energy resources and the use of gram but is not the focus. The gathered re- renewable energy are measures which lead search which was collected within this An- to a reduced utilization of fossil energy, and nex should contribute to establishing DH thereby a reduction of GHG emissions. as a significant factor for the development Within this context, it is mandatory to con- of 100 % renewable energy based commu- sider the entire energy chain to achieve a nal energy systems in international research good overall system performance. This me- communities and in practice. In connec- ans evaluating all energy flows, from the ex- ting the demand side (community/building traction of primary energy, to the utilization stock) and the generation side (different of heat in buildings. This approach allows energy sources which are suitable to be fed achieving optimal solution for supplying heat in the DH grids), this technology provides to the building stock, independently on the benefits and challenges at various levels. energy efficiency of single components of

Secondary Energy Supply (≈ 80 %): CHP, surplus heat from industrial District heating system processes etc.

Primary Energy Supply (≈ 15 %): Heat delivered for Renewables like geothermal heat, low temperature solar heat and biomass heat demands

Primary Energy Supply (≈ 5 %): Fossil fuels for peak load and back-up demand

Heat losses (≈ 10 %)

Figure 2-1 Example of a district heating system which incorporates inputs from fossil and renewable energy sources, and utilizes surplus heat sources (acc. Frederiksen and Werner, 2013) 12 2.2 Scope and objectives grids is necessary. In this way, low temperature DH can become the least expensive The Annex TS1 is intended to provide solu- way of realizing the future of fossil free ener- tions for both expanding and rebuilding exis- gy systems in the heating sector. The new ting networks and new DH networks. It is approach to DH is to support the setup of strongly targeted at DH technologies and the sustainable structures and safe energy sys- economic boundary conditions of this field tems for future building stock. of technology. The area of application under In order to achieve the described objectives consideration is the usage of low tempera- challenges are identified. The development ture district heating technology on a com- of appropriate solutions helps to reduce fos- munity level. This requires a comprehensi- sil energy consumption and, thus, emissi- ve view of all process steps: From heat ge- ons. The improvement areas are new me- neration over distribution to consumption thodologies, concepts, and technologies in within the built environment. The approach the field of DH. This includes an improved includes taking energy (e.g. primary ener- integration of renewable and surplus heat as gy, end energy, etc.) and exergy into ac- well as the adaption of energy and exergy count. This allows an overall optimization of demand by taking interactions of buildings energy and exergy performance of new dis- and supply systems into account. trict heating systems and the assessment of conversion measures (from high tempera- Residential Heating or Renewable energy sources ture DH to low temperature DH) for existing buildings CHP plant DH systems. The main focus of DHC Annex TS1 is low temperature district heating for the application in space heating (SH) and domestic hot water (DHW) preparation. Since today it has been found that heating is by far more relevant for the building sector in areas where Waste heat from district energy is used, district cooling is not industry considered here (even so the future cooling Commercial demand is considered to be so big that the buildings cooling market might actually surpass the DH market). This helps to keep the focus Figure 2-2 Schematic district heating community supply system with multiple supply options. on the research initiative. The main objective of the DHC Annex TS1 Additionally, economic aspects must be ta- is to demonstrate and validate the potenti- ken into consideration. In this context, new al of low temperature district heating as one business cases and models could support of the most cost efficient technology soluti- the wider implementation of new and espe- on to achieve 100 % renewable and GHG cially innovative low temperature DH sys- emission-free energy systems on a commu- tems. Next to this technology, developments nity level. This is reached by providing tools, for reduced DH network costs are necessary. guidelines, recommendations, best-practi- It seems to be sensible to focus on the mo- ce examples and background material for tivation for investments into new networks designers and decision makers in the fields and the renovation of existing networks. of building, energy production/supply and It can be said that the focus of Annex TS1 politics. is based on the need of reducing resour- During the course of the Annex activities, ce consumption (including primary energy) the aim was to develop and improve means and GHG emissions through overall system for increasing the overall energy and exergy optimization in collecting the most recent efficiency of communities through the use knowledge in the DH sector in one place to of low temperature district heating. There- maximize the future development rate. fore, the compilation of existing know-how for developing new district heating concepts and for implementing the results in existing www.iea-dhc.org 13 2.3 Performance of low temperature systems are regarded as integrated compo- district heating on a community scale nents of an energy system. A number of issues need to be addressed in regard to mat- Low temperature district heating for future ching the demand created by space heating energy systems offers prospects for both the and domestic hot water on the building side demand side (community building struc- with the available energy from the supply ture) and the generation side (properties of side in order to develop advanced low tem- the networks as well as energy sources). Es- perature heating networks. pecially in connection with buildings that require only low supply temperatures for space heating, low temperature district heating of- 2.4 Main objective and layout of the fers new possibilities for greater energy ef- report ficiency and utilization of renewable energy This report is a summary of the results ob- sources, which lead to reduced consump- tained during the course of the Annex TS1 tion of fossil fuel based energy. work. It is oriented to the target groups of de- On the demand side, low temperature heat signers and decision makers in the building sources are commonly available and can and district energy sector as well as key per- serve as a basis for energy efficient space sons in the energy supply industry. The re- heating and domestic hot water (DHW) pre- port is intended to bring them closer to the paration. Even if the low temperature heat concept of low temperature district heating source has insufficient temperature level it by giving an overview on the main features can be integrated into the district heating and benefits of this way of supplying heat to system through temperature boosting, e.g. building stocks. Therefore, technical details the use of efficient large scale heat pumps, of the concept as well as the used techno- solar thermal collectors or biomass fired - logies are outlined and explained in a sim- combined heat and power plants. Generally, plified and applied manner. In addition, the the utilization of lower temperatures redu- main features of several low temperature ces transportation losses in pipelines and district heating schemes and case studies can increase the overall efficiency of the to- highlight the main benefits of this approach. tal energy chains used in district heating. To More details can be found in the more ex- achieve maximum efficiencies, not only the tended subtask report or in the material lis- district heating networks and energy con- ted in Appendix C which is freely available version need to be optimal, but also the de- under the homepage www.iea-dhc.org. This mand side must be designed for using the material is partly oriented to scientists and low temperature supplied by the network. researchers working in the field of innovati- For this reason, the implementation of so- ve district energy systems. lutions based on large shares of renewable In this context the main objective of the DHC energies may require an adaptation of the Annex TS1 is to demonstrate and validate technical and building infrastructure. The the potential of low temperature district hea- indoor temperature requirements in most ting as one of the most cost efficient tech- building types (residential and non-resi- nology solution to achieve 100 % renewable dential buildings) are generally low (below and GHG emission-free energy systems on 23 °C). With the right heating installation this a community level, as already stated in de- demand can be met with supply tempera- tail in chapter 2.2. So, the topics mentioned tures of between 35-40 °C. In the case of above are treated in the following chapters: the provision of domestic hot water, supply After a presentation of the general frame- temperatures in the range of 50 °C should work of the Annex TS1 activity within the principally be sufficient to avoid the risk of International Energy Agency (IEA) in chap- (legionella) bacterial growth. Both renewa- ter 1 and an introduction into this report in ble and surplus energy sources, which can chapter 2, chapter 3 gives a brief overview be harvested very efficiently at low tempe- of the general concept of low temperature rature levels, can fulfil this energy demand. district heating. Several technical features On the community scale, synergies are ma- as well as key benefits are highlighted the- ximized when buildings and building supply re. In chapter 4 needed key technology sets 14 are presented. District heating technologies thermore, the issue of pricing and business as piping systems or thermal grid design lay- models is covered. In chapter 6 an analysis out are presented as well as an introduc- of various tools and software models for the tion in advanced secondary side / building planning and design of district heating sys- technology is given. Various designs of sub- tems is presented. The tools are briefly de- stations, the connection to low temperature scribed and their properties are displayed. space heating systems and ways to prepare Built on this analysis the simplified Microsoft domestic hot water hygienically with a con- Excel based tool, the developed Easy District nection to a low temperature district heating Analysis (EDA), is described. Chapter 7 gi- scheme are explained. Chapter 5 highlights ves an insight into seven real live case stu- and summaries important topics for a rea- dies of the application of low temperature lization of district heating schemes as the district heating to community heat supply estimation of distribution losses or the de- from the participating countries. velopment of heat demand structures. Fur-

www.iea-dhc.org 15 3 LOW TEMPERATURE DISTRICT HEATING

3.1 What is low temperature district rated components of an energy supply so- heating? lution. That is why implementation of solutions based on large shares of renewab- Low temperature district heating is a heat le energies requires an adaptation of tech- supply technology for efficient, environmen- nical and building infrastructure. In cont- tal friendly and cost effective community rast to the current standard network design, supply. Traditionally district heating grids are the low temperature district heating concept operated at temperature levels up to 100 °C goes further in optimizing the overall system. (e.g. so-called 3rd Generation DH). In com- One of the key differences between the tra- parison with conventional district heating, in ditional approach and the low temperature low temperature district heating the network district heating approach is that an ener- supply temperature is reduced down to re- gy quality match is performed between the quired temperature levels of about 50 °C or end-user thermal comfort requirements and even less (4th Generation DH). Simultane- the energy supply options at the same time ously low temperature district heating cou- as the energy transportation infrastructure is pling with reduced network temperature designed. By going through the process the and well-designed district heating network most efficient and economical way to satisfy can reduce heat losses of the grid by up to the heat demand is identified. Furthermore, 75 % comparing to the current system de- by matching the energy quality of the sup- sign. To achieve maximum efficiencies, the ply to the demand the low temperature dis- district heating network, energy conversion trict heating opens up for further possibilities process and the end user installation within for achieving greenhouse gas (GHG) emissi- the supplied buildings need to be optimized on free supply systems based on waste heat to utilize lower network supply temperatu- and renewable energies only. res. When the building systems and district heating supply network are treated as one 3.3 An economically efficient low integrated system, synergies and economies of scale can be optimized on a community temperature heating energy supply scale. Low temperature district heating is an Specifying low network temperatures opens enabling technology to increase the integra- up for a heat source flexible approach to tion of renewable and waste energy sources the heating energy supply of communities for heating and cooling (e.g. from solar ther- and results in economically competitive so- mal collectors, biomass fired heating plants, lutions, because of the easy integration of combined heat and power systems or from different renewable or waste heating energy (large) heat pumps to use excess electrici- sources into the supply systems. From an ty from wind power plants). This contribu- economical point of view, relatively high pri- tes to meet national and local GHG reduc- ce stability can be expected due to the use tion targets. of locally available, renewable, or surplus heat energy sources. An additional advan- 3.2 A sustainable and flexible approach tage of this is a lower dependency on fos- to the energy supply of communities sil fuel supplies, which leads to increased energy supply security. The high overall sys- Low temperature district heating (LTDH) of- tem performance can be achieved by using fers a sustainable and flexible approach to innovative low temperature district heating the energy supply of communities. On the technologies which leads to reduced resour- buildings’ side a number of issues of mat- ce consumption as well as higher fuel effici- ching the demand need to be addressed encies and lower total costs for fuels. For to develop advanced low temperature hea- this reason, low temperature district heating networks. On community scale syner- ting is seen as an emerging innovative sys- gies are maximized, if buildings and buil- tem technology with high potential to repla- ding supply systems are regarded as integ- ce current technologies. 16 4 DISTRICT HEATING AND COOLING TECHNOLOGIES

4.1 Introduction Today, the 4th generation DH (4GDH) is emerging as a new system to replace the Since the first commercial district heating existing 3rd generation DH system. 4GDH is (DH) system was introduced in 1877 in also named as low-temperature DH (LTDH). Lockport, New York, the evolution of DH has The benefits are both in heat distribution gone through three generations which are and heat generation. In the heat distribution, characterized by the type of transport me- it reduces the network heat loss, improves dia, applied equipment and the network quality match between heat supply and heat st temperature levels. The 1 generation DH demand and reduces thermal stress and system is steam-based system which inclu- risk of scalding. In the heat generation, lo- des a large diameter steam supply pipe and wer network supply and return temperature a small diameter condensing pipe to return helps improve CHP plant power to heat ra- nd condensed water. The 2 generation DH tio and recover waste heat through flue gas uses pressurized hot water as transporting condensation, achieves higher COP values media to supply temperature above 100 °C, (efficiencies) for heat pump, and enlarges pipes were insulated onsite and substations the utilization of low-temperature waste heat rd were built onsite. The 3 generation DH was and renewable energy. LTDH has been con- introduced in 1970s. It represents medium tinuously developed as the next generation network supply temperature between 80 °C DH and is ready to replace the current me- rd to 100 °C. The 3 generation DH is the do- dium temperature DH system. minant DH technology in Nordic countries. LTDH based on renewable energy can sub- rd The DH pipes in the 3 generation network stantially reduce total greenhouse gas emis- use pre-fabricated, pre-insulated metal sions and secure energy supply for future pipes directly buried in the ground and sub- development of society (Lund et.al 2014). stations became factory assembled and in- It has the ability to supply low-temperature sulated (Frederiksen and Werner, 2013). DH for space heating and domestic hot wa-

1st Generation: > 200 °C

200 Steam system, steam pipes Pressurized hotwater system Pre-insulated pipes Low energy demands [°C] in concrete ducts Heavy equipment Industrialized compact Smart grid (optimum Large „build on site“ stations substations (insulated) interaction of energy sources, Metering and monitoring distribution and consumption) 2-Way DH 150

2nd Generation: > 100 °C Energy e ciency

100

Temperature level Temperature 3rd Generation: 80 – 100 °C

4th Generation: < 60 (70) °C 50

1880 1930s 1970s 2010s Future Time Figure 4-1 Development of the district heating technology © Fraunhofer IWES www.iea-dhc.org 17 ter (DHW) for various types of buildings, to DH network heat loss is determined by mul- distribute heat with low heat losses and abi- tiple factors: geometrical condition (network lity to recycle heat from low-temperature dimension, length and ground conditions/ waste heat and renewable energy sources. properties), DH pipes (type of pipes, insu- From various research and development of lation materials/conditions) and DH operati- LTDH projects, it has been shown that it is on (heating load, temperature level, bypass both technically feasible and economically operation and other factors such as leaka- sound to change current high/medium tem- ges) (Li 2015). perature district heating system to LTDH for both new and existing building areas (Rosa 4.2.2 Types of DH Pipes Types et al. 2014). There are different types of pipes used in During the course of the IEA DHC Annex TS1 DH. Some of them are in the commercial project promising technologies and ideas for market like single pipe and twin pipe. The LTDH application have collected and iden- rest are developed for the purpose of con- tified to meet the goals of future renewable ceptual investigation which can be ideal for based community energy systems. Innova- some specific conditions like triple pipe and tive technologies and advanced system con- double pipe with different diameter of the cepts in LTDH are reported for heat gene- supply/return pipe. The commercial product ration, distribution and end user utilization. includes both rigid pipes and flexible pipes This special chapter aims to provide back- with small diameter. ground materials and cutting edge know- To reduce network heat loss, small pipe dia- ledge for designers and decision makers in meters and high performance pipe insulati- the building and district energy sector. on is recommended in the distribution network and service pipes. Figure 4-2 shows 4.2 District Heating Pipes a service pipe specifically designed for LTDH The heat loss in a DH system occurs in dif- projects (EFP 2007) as an example. It is an ferent places in the heat generation, distri- AluFlex pipe with 10mm inner pipe diame- bution and utilization, appearing in different ter. The service pipe in AluFlex is a sand- forms. This section describes the heat loss in wich construction which consists of an alu- the district heating network. The success of minum pipe coated in-between the outer PE LTDH largely relies on substantially reduced layer and inner PEX layer. distribution heat loss. In this chapter different types of pipes and insulation materials applied in LTDH are described and a general steady state heat loss equation for co-insulated pipes is introduced.

4.2.1 Influence factors for network heat loss The network heat losses account for a significant portion of annual operational cost and environmental impacts if the heat source is based on fossil fuel. The network heat loss is relevant in the following aspects: Figure 4-2 AluFlex Service Pipe (EFP 2017) and • The annual district heating network (Logstor 2017) heat loss influences the district heating economy. 4.2.3 Insulation Properties • The network heat loss influences the required bypass flow rate through the ther- Pipe insulation forms the most critical thermostatic bypass valve. mal resistance in the DH pipe heat trans- • Pipe heat loss is important in the net- fer. The higher the insulation level the less work dynamic performance. the network distribution heat loss becomes, thus improve the DH economy. The heat 18 transfer in an insulation material includes ween the supply and return pipes, which re- heat conduction through pores wall, heat duces the impact in case of malfunctioning conduction due to insulation gas collision, valves (Kuosa et al. 2013). and heat transfer between pores wall due to Figure 4-4 (a) shows the traditional and ring long wave radiation. network in an area of nine detached houses Traditionally insulation material like mineral (1-9, DH) and two apartment buildings (1-2, wool (λ ≈ 0.033-0.04 W/mK) was used for AB) (Laajalehto et al. 2014). The idea of the district heating pipe insulation, but after in- ring topology is to have an equal pipe length troduction of PUR insulation (λ ≈ 0.024 for every consumer as presented in Figure W/mK) it has been phased out gradually. Su- 4-4 (b). The supply line (red line) begins per-insulation, with thermal conductivity (λ) from the heat station (HS) and ends with the below 0.02 W/mK is in the experimental sta- last customer, as in the traditional network ge and is expected to be proven valuable for design. However, the return line (blue line) DH (Berge and Johansson 2012). Solutions begins from the first customer and ends at to improve insulation effect include apply- the heat station. In both the supply and re- ing diffusion barrier in DH pipes and apply turn lines, DH water circulates in the same asymmetrical insulation in twin pipe to re- direction. In ring networks twin pipes can- duce return pipe heat loss (Figure 4-3). not be used, which might lead to higher heat losses. But double pipe with different pipe diameter might be used in these networks. On the contrary, in a traditional DH network design, the return line begins from the last customer and proceeds back to the heat station.

Figure 4-3 Asymmetrical twin pipe 4.3 Energy Efficient District Heating Network

4.3.1 Ring Network In traditional DH network design, the pipe lengths between the heating plant and different consumers vary. The consumers close to the plant has larger available differential pressure, whereas the consumers away from the plant have smaller available dif- Figure 4-4 (a) Traditional district heating network design and (b) ring network design. The yellow lines are roads, the red line is the ferential pressure. In an uncontrolled pipe supply line, and the blue line is the return line. DH detached network, the pressure profile in the system house, and AB apartment building (Laajalehto et al. 2014). would lead to more water flow through the consumers close to the plant and insufficient water flow through the consumers loca- 4.3.2 General solutions to avoid bypass ted far away from the plant. To overcome flow in service pipes this, valves are installed in the network to When the network heating demand beco- increase the flow resistance until the requi- mes low, the required mass flow rate is re- red flow to fulfill consumer’s heat demand duced accordingly. A smaller mass flow rate is achieved. causes a larger water temperature drop One solution to reduce the valve throttling along the pipeline due to heat loss to the and potential hydraulic imbalance when the ground. In non-heating season, the DHW valves were malfunctioned is to apply a ring load is low and its demand is intermittent shape network topology. Unlike the traditi- with the total draw-off duration less than onal network, a topology based on ring net- 1 h/day. To keep high thermal comfort, by- work equalize the pressure differences bet- pass valves are installed at the DHW subs- www.iea-dhc.org 19 Idling controller bypassing the supply line recirculation pipe can be a separate DH pipe or one of the pipes in a co-insulated triple pipe. This solution is however likely to create DH supply 50 °C a need for a bypass flow in the street pipes. DHW nd 45 °C The 2 solution is based on the maximum cooling principle. After passing through the service pipe, the bypass water is directed DCW to the bathroom floor heating and cooled 10 °C DH return 25 °C down to 25 °C before it flows back to the return pipe. The benefit of this concept is Figure 4-5 Bypass from supply pipe to return pipe © Danfoss that it uses the bypass flow continuously in tation in order to keep the supply water tem- the floor heating and replaces an intermit- perature close to the set-point. The possi- tent flow due to a conventional floor heating ble bypass functions include bypass from control. In case there is no floor heating in the supply pipe to the return pipe, bypass the bathroom a towel heater may utilize the over the control valve or by applying set- bypass flow. Such an application is called back temperatures at the heat exchanger. ‘Comfort Bathroom (CB)’ concept. This solu- Figure 4-5 shows the bypass from the sup- tion is also securing a flow in the street pipes ply pipe to the return pipe. and therefore does not need a bypass flow When there is no draw-off, the DH supply in the street pipes. water is bypassed and flows back to the net- The 3rd solution is based on electrical sup- work return line without any cooling, it in- plementary energy. In large buildings with creases the network return temperature si- DHW circulation the need to keep the cir- gnificantly and subsequently increases the culation at a minimum of 50 °C results in network heat loss and decreases the ther- a high return temperature and requires a mal plant performance. This network perfor- district heating supply temperature of more mance degradation is particularly relevant than 55 °C. This can be avoided by use of for LTDH and DH supply to sparse areas. a heat pump that cools the district heating To keep low network return temperature, it supply from 50 °C to 20 °C and heats the should be avoided to having the DH supply circulation loop to 55 °C. Figure 4-8 shows water directly mixed with the return water. the schematic to use micro-heat pump to Several solutions have been suggested to compensate the heat loss in the DHW cir- eliminate the service pipe bypass. culation loop and keep the pipes temperature at 50 °C. The benefit of this concept

3 is that the district heating flow to the heat pump also secures the instantaneous DHW

DHW heating of the heat exchanger. This solution 1 does not require bypass in the street pipes. 2 Return 2 4.3.3 Network circulation to eliminate street bypass 3 1 SH Recirc. Supply The precondition to eliminate service pipe bypass with the solutions described in chapter 4.3.2 is that the temperature at the street pipe should be kept above the minimum street set-point temperature (for example Figure 4-6 Minimum cooling concept with a triple service pipe 50 °C). The street bypass is used to circulate (Dalla Rosa et al. 2011) DH water at the end of the street (normally is the location for the critical user) in order The 1st solution is based on the minimum to keep the minimum DH supply tempera- cooling principle. A recirculation flow in the ture along the whole distribution network. supply pipe warms up the service pipe and Similar to the service pipe bypass, the street then flows back to the supply pipe in the bypass water mixes with return water and street through a third recirculation pipe. The 20 Figure 4-7 Comfortable bathroom concept (Brand 2014) increases the network return temperature. to balance the flow in the network. With ca- One solution to avoid street bypass is to con- reful placement of connection pipes and ad- nect the branch shape network into the loop justment for the flow balance, the increa- network. Such network configuration allows sed power consumption of the pumping is DH supply water circulate along all street negligible comparing with the heat loss sa- pipes. The supply water flows back to the vings. The length of connecting pipes, how- plant instead of mixing with return water. ever, depends on the network topology thus All street pipes can be kept warm if the cir- needs specific analysis for each individu- culation water temperature at the plant is al network. set as the minimum street set-point temperature. The hydraulic implications for that setup would be that the pump at the plant drives the flow passing through the dense area first then the sparse area. It would get more resistance if flow in opposite direction. A case study to apply the network circulation to eliminate street bypass was performed for a DH system at Viborg, Denmark. Figure 4-9 and Figure 4-10 show the original network and the circulation. A detailed network simulation was performed with TERMIS (Schneider 2017). The simulation Figure 4-8 DHW system installing a central heat exchanger combined with heat pump (Yang 2016) results indicate that significant amount of energy saving can be achieved when the 4.4 Domestic hot water supply supply water is kept flowing through the entire network. The heat loss saving is achieved A well-designed and functioning DHW sys- with a cost of increased network differential tem should meet several criteria which in- pressure, pumping power, pipe length and clude consumer comfort, hygiene, energy adding local circulation pumps and valves efficiency and effective cooling of the supply www.iea-dhc.org 21 Figure 4-9 Original network and removed street pipes Figure 4-10 Circulation network (Lund et al. 2014, Brand 2013, Yang 2016 risk). The temperatures at the outlet side of and Bartram et al. 2007). central DHW preparation units with and without DHW-storage as well as at the tapping 4.4.1 European regulations and guide- point differ from country to country (Dalla lines for DHW preparation Rosa 2014). However most of the European countries follow the guideline EN 806 - Spe- In the context of drinking water installation cification for installations inside buildings the European regulations EN 806 (EN 806- conveying water for human consumption 1:2000 and EN 806-2:2005), and EN 1717 (EN 806-1:2000 and EN 806-2:2005) and (EN 1717:2011) formulate a minimum stan- CEN/TR 16355:2012 - Recommendations dard and represent the greatest common for prevention of Legionella growth in instal- denominator of European countries. The EN lations inside buildings conveying water for 806 provides recommendations for the pl- human consumption (CEN/TR 16355:2012 anning of drinking water installations and is and Allegra et. al. 2011). According to the- applicable for new installations, alterations se guidelines it is suggested that the water and repairs. temperature should not exceed more than The regulation EN 1717 (EN 1717:2011) is 25 °C for domestic cold water (DCW) and a guideline to protect drinking water from should not be less than 60 °C for domestic contamination in drinking water installati- hot water (DHW) 30 seconds after fully ope- ons and contains general requirements for ning of a sampling point. In addition to tem- safety equipment to prevent contamination perature levels more requirements for wa- of drinking water. The technical report CEN/ ter installations are also specified. It is de- TR 16355:2012 (Allegra et al. 2011) provi- termined that systems of heated water must des basic information about the conditions be designed in a way that the risk of scal- for Legionella growth in drinking water ins- ding is low (CEN/TR 16355:2012 and EN tallations in accordance with EN 806 (EN 806-2:2005). 806-2:2005) series up to the draw-off points Regarding the risk of scalding for kinder- and gives recommendations for preventing gartens, schools and senior citizen residen- the growth of Legionella in these installati- ces lower temperature levels are required. ons. Additional or country-specific regulati- Furthermore, the EN 806 contains require- ons are given in section Appendix A: Natio- ments for the distribution of DCW and DHW. nal Standards and guidelines on domestic Distribution of domestic cold water for low hot water of IEA DHC participating countries. sampling or rare use must not be installed In particular temperature levels are an im- at the end of a long line. Furthermore, the- portant issue regarding DHW preparation se pipes must not be laid close to pipes pro- based on LTDH due to hygienic reasons (e.g. viding hot water in one shaft or channel. In temperature interval of legionella growth 22 Table 4-1 Overview of small and large DHW systems (DVGW W551 2004): Storage Definition Building type volume Piping volume Other requirements Single and multifamily buildings no requirement no requirement* - small system Other buildings < 400 litres ≤ 3 litres - All buildings > 400 litres ≤ 3 litres - large system All buildings > 400 litres > 3 litres installation of a circulation All buildings < 400 litres > 3 litres installation of a circulation *Pipes from DHW unit to tapping point case of DHW distribution national or local re- power. Meanwhile, effective cooling leads gulations to prevent the growth of Legionel- to smaller network return temperature and la must be respected. In addition hot water smaller network heat loss. The heating plant systems should have the facility to increase thermal performance can be improved if the the temperature of the system at any point low temperature return water can be used to 70 °C for disinfections purposes. for flue gas condensation. As an example for the distinction between application in single and multi-family houses Common DHW units with storage tanks used in but also for commercial buildings the Ger- connection with DH man guideline (DVGW W551 2004) is used. Typical units with storage tanks which are The regulation considers storage tanks and connected to DH that can be found all over piping volume. Furthermore a distinction Europe are the DHW charging application between small and large systems with re- and the DHW cylinder application. gard to Legionella risk is made. Using a DHW charging application DHW The table above contains an overview of the is heated in a heat exchanger and let into requirement with regard to German guideli- a storage charging tank (see Figure 4-11). ne DVGW W551: To maintain the desired temperature during As can be seen from above and Table 4-1, idle time, the water temperature at certain these guidelines are aimed at traditional location above the bottom, typically 1/3 of DHW installations with large DHW volumes. the volume, is monitored and if the tempe- These regulations do not consider the new rature goes below a certain set point the wa- principles and very low DHW volumes ap- ter at the bottom of the storage tank is circu- plied in 4th generation district heating (Lund lated through the heat exchanger. This will et al. 2014). Typical DHW units with storage ensure that there will be sufficient amount tanks used in connection with DH are dis- of hot water available in the tank at the same cussed in chapter 4.4.2. time as adequate cooling of the DH supply is achieved. The storage charging tank is 4.4.2 Domestic hot water units especially suitable for special applications, e.g. commercial buildings where the peak DHW installations should be designed with load of DHW is high. focus on energy efficient devices. The factors which influence DHW system energy efficiency include district heating supply and return temperature, heat losses from heat exchanger, storage tank and pipes, and thermal bypass set-point. Effective cooling of the supply corresponds to large temperature drop in the consumer end. With improved DH water cooling, each unit of DH water brings more energy con- tent. This will reduce the plant pumping Figure 4-11 DHW charging application © Danfoss www.iea-dhc.org 23 This DHW preparation is normally used in DHW units for implementation in LTDH combination with heating. There are two types of DHW units used for Areas of use: LTDH: instantaneous heat exchanger unit • One-family houses (IHEU) and DH storage tank unit (DHSU). • Multi-family houses The heat exchanger of the IHEU physically • Commercial buildings separates the DHW and DH water. IHEU Typical markets: Central, South and Eastern produces DHW instantaneously when the Europe hot water tapping is on. The DH supply water Another option is using DHW cylinder appli- in the primary side passes through the heat cation (see Figure 4-12). DHW is heated in exchanger and is cooled by the cold water a cylinder by an internal heating coil. DHW from the secondary side. On the secondary cylinder application is typically applied in side, the cold water is heated up to the desi- decentralized boiler applications, it is not red temperature and supplied to the tapping recommended in connection with DH sys- point for consumer use. The application can tems due to generally high return tempe- supply an unlimited amount of hot water at ratures compared to storage charging ap- a constant temperature, which is prepared plications. This is not of a big concern in close to the tapping point when demanded decentralized boiler with small distribution and hence reduces the risk of legionella and network. In contradiction in large distributi- other bacterial growth. The total DHW instal- on networks, as DH, it is leading to big heat lation volume should be designed to be less losses. than 3 liters (DS/CEN/TR 16355 2012). Fi- gure 4-13 shows the schematic of the IHEU with dp-controller and thermostatic and proportional DHW controller.

Figure 4-12 DHW cylinder application, not recommended to be used in district heating systems © Danfoss This DHW preparation is normally used in combination with heating. It is not recommended in DH systems, especially not in Figure 4-13 Instantaneous heat exchanger unit (IHEU) LTDH. © Danfoss Areas of use: • One-family houses This DHW preparation is normally used in • Multi-family houses combination with heating. Typical markets: Germany, Italy, Austria and Areas of use: UK. • One-family houses Once the DHW capacity of the storage tank • Multi-family houses has been used, it needs time to be rechar- • Commercial buildings ged. In the event of DH interruption for short Typical markets: Almost all markets. periods of time, the storage charging tank In DHSU, the storage tank is installed on can supply the remaining capacity of DHW. the primary side and acts as a buffer to the However, large-volume storage tank increa- secondary side. DH is drawn from the top se the risk of bacterial growth and need ad- of the storage tank and exchanges heat ditional maintanance (Danfoss 2017). Fur- through the heat exchanger on the secon- thermore storage tanks have a large space dary side. As the storage tank in the prima- requirement and large heat losses. Due to ry side, it is feasible to supply low-tempe- these DHW storage tanks are not recom- rature to the DHSU. Figure 4-14 shows the mended in LTDH. schematic of DHSU. 24 Figure 4-14 District heating storage unit (DHSU) © Danfoss Both IHEU and DHSU can work at low-tem- gionella multiplication in a DHW system is perature without the risk of Legionella. Due influenced by the type of DHW installations to the storage tank buffer effect, DHSU can (configuration of the pipes of hot water sup- reduce the connection capacity and thus ply and recirculation, pipe dimension and apply smaller diameter service pipes at the pipe materials), age of the piping systems, cost of additional heat loss from the sto- scaling and presence of biofilm, etc. (Yang rage tank. On the other hand, IHEU has less 2016). standby heat loss and is more compact and In general, the Legionella treatment solu- less costly. tions include thermal treatment, chemical treatment, physical treatment and other al- 4.4.3 Legionella treatment solutions ternative methods. Such treatments aim at either killing the bacteria present in the wa- DHW is often supplied by DH with centra- ter or prevent the spread of Legionella by li- lized hot water production and long distri- miting the bacteria multiplication within a bution distance. LTDH reduces the network safety margin (Yang et. al. 2015). forward temperature to the threshold value of ensuring hygienic DHW supply. One of the key issues in LTDH is how to supply DHW at greatly reduced temperature without the risk of Legionella. To ensure safe supply, many countries regulate the minimum DHW supply temperature and recirculation temperature. A well-designed and functioning DHW system must fulfill the requirements for hygiene, thermal comfort and energy efficiency. The major con- cerns with DHW preparation are hygienic and health risks, where the health risks result from bacteria growth in the water (e.g. appearance and growth of Legionella pneu- Figure 4-15 Legionella bacteria growth/ decay rates mophila). In general the bacteria risk is pre- as a function of temperature sent when the DHW temperature is below (Frederiksen and Werner 2013) 50 °C, as shown in Figure 4-15. For all practical purposes 50 °C is high Thermal treatment Legionella bacteria can be killed rapidly at enough for human hygienic needs, e.g. dis- high temperatures. Thermal disinfection solving food fats in dishwashing. Legionel- through heat flushing is considered as a sys- la growth at 50 °C is confined. This tempe- tematic method which requires the whole pi- rature is also low enough to avoid scalding ping system to be treated at the same time. of human skin, which can occur at tempe- The temperature at the distal faucet should ratures above 65 °C (Frederiksen and Wer- be elevated to no less than 60 °C. Thermal ner 2013). Except the temperature, the Le- www.iea-dhc.org 25 Figure 4-16 Domestic hot water thermal clean system © Danfoss disinfection is normally used as an effici- dizing agents. Effective chemical treatment ent short-term treatment to control a Legi- requires precise control of dosage concen- onella outbreak. It can be combined with tration. After the treatment, the system is other treatment solutions (like chemical required to be thoroughly flushed to remo- treatment) for long term effect. Figure 4-16 ve corrosive and possibly toxic chemicals. shows the DHW thermal cleaning system. Ionization uses two different ionized metals In case of thermal disinfection to counter le- to disrupt the permeability of the bacteria’s gionella contamination WHO recommends a cell wall and subsequently denatures prote- heat shock at 70 °C for 30 min. which is to ins and cellularlysis. The most widely used be repeated at least twice during 72 hours electrodes are copper /silver. (Allegra et. al. 2011). For the hot water at The oxidizing disinfectants are mostly used the storage tank, the temperature should in chemical treatment solutions. It includes be lifted to 70-80 °C and kept at this tem- various types like chlorine, chlorine dioxide, perature level for 72 hours to eradicate the ozone, monochloramine and hydrogen per- bacteria in the tank (Campos et. al. 2003). oxide. Among these, chlorine is one of the most widely used oxidizing disinfectants in Chemical treatment different water systems. Chemical treatment rinses the piping system with chemical biocides to kill off legionella. Physical treatment It is widely used for bacteria disinfection in Physical treatment disinfects water without water system. Chemical treatments inclu- chemical addition and leaves no residuals de ionization, oxidizing agents and non-oxi- and odor after treatment. It includes membrane filtration and UV sterilization. UV Steri- lization cleans water with the ultraviolet light at a wavelength of 254 nm. The disinfection process works by damaging the bacteria DNA replication, similar to an open stream exposed under sunlight. The filtration membrane has fabric structure with a large amount of microscopic pores. The membrane retains bacteria, but allows vital mi- Figure 4-17 UV Sterilization (Walleniuswater 2017) nerals to go through. It has superior disin- 26 fection efficacy and is commonly used for physical treatment of nosocomial Legionel- losis in high-risk patient care. Figure 4-17 shows the UV sterilization method.

Alternative solution Chemical and physical treatments are normally independent of temperature level and thus can be applied in LTDH. The limita- tions of their application are the initial cost for disinfectant production, precise monitoring and control systems, and risk of corrosive and possibly toxic chemical residuals. Apart from chemical and physical treatments, alternative solutions exist for LTDH application. Figure 4-18 Flat station in multi-story buildings (Thorsen 2010) For single family houses, the risk of Legio- be an electric heater in the storage tank, nella can be controlled through confining an electric heater after the DHW heat ex- the DHW volume in the secondary circuit. changer or a micro-heat pump combined The DHW volume from the substation to the with DH storage tank units. Such solutions tapping point is designed below 3 liters (see can also be applied in ultra-low temperature DVGW W551 2004). This way, the circulati- DH systems. Another thermal booster sys- on pipe is eliminated and DHW can be sup- tem is using electric tracing. Such a solu- plied safely at low-temperature. tion is normally applied in multi-story buil- Multi-story buildings are traditionally sup- dings or buildings with a large volume DHW plied from centralized heating units. The pipework to keep the supply pipe warm so DHW supply pipe is kept warm through a that the circulation pipe can be eliminated. circulation pipe to ensure consumers get Figure 4-19 shows the electric tracing de- warm water without excessive delay. The vice and its use in DHW supply pipes. The supply temperature is typically above 60 °C. circulation pipe can be eliminated through To supply LTDH to multi-story buildings, one use of an electric heat tracing device. of the effective solutions is to use flat sta- The electric cable is attached outside of tions. As shown in Figure 4-18, a flat station the DHW supply pipe to heat it. The elec- is a small substation installed at each indivi- tric energy consumption is self-regulated dual flat in the multi-story building to fulfill which is proportional to the temperature SH and DHW demand. Similar to the sing- difference between the cable and the hot le family house, the 3 liter rule can be sub- water. With an electric heat tracer, the total sequently applied to multi-story buildings. energy loss can be reduced by 40 % com- As described in 4.3.2, low-temperature paring with the system with circulation pipe DHW can be boosted on-site through au- (Yang et al. 2015). xiliary energy. The supplementary energy normally comes from electricity. It can

Figure 4-19 Electric heat tracing of domestic hot water pipe (Yang and Svendsen 2014) www.iea-dhc.org 27 DHW supply at ultra-low temperature the European countries more or less follow Beyond LTDH, it is possible to supply ultra- the European guidelines EN 806-1:2000, low temperature DH at temperatures below EN 806-2:2005 and EN 1717:2011 which 50 °C to meet the residential building hea- differentiate between small and large sys- ting requirement. Such an application has tems but do not consider the very small vo- the advantage to further reduce network lume (<3 liters) systems that are used in heat loss and increase waste heat utilizati- LTDH schemes. Recommended operating on. Cases are reported to use ultra-low tem- temperatures for large systems (e.g. mul- perature DH with different types of thermal ti-family house, hotels, etc.) are between boosters at the consumer substations (Yang 55 °C - 60 °C and temperatures in small et al. 2016). systems (e.g. single family house) should not be below 50 °C. Further DHW installations should be designed with focus on energy efficient devices. There are two types of DHW units used for LTDH: instantaneous heat exchanger unit (IHEU) and DH storage tank unit (DHSU). Both IHEU and DHSU can work at low-temperature without the risk of Legionella. IHEU has less standby heat loss and is more compact and less costly compared to other Figure 4-20 Schematic of electric micro tank system (Yang et al. 2016a) solutions as DHSU. On the other hand Due to the storage tank buffer effect, DHSU can Figure 4-20 shows the solution to use a small reduce the connection capacity and thus storage tank with electric auxiliary heater. apply a smaller diameter service pipe at the The micro tank with immersed electric hea- cost of additional heat loss from the storage ter is installed on the consumer side. The tank. One of the key issues in LTDH is how DHW is preheated by ULTDH through the to supply DHW at greatly reduced tempera- heat exchanger. Since the temperature of ture without the risk of Legionella. For that the preheated water is lower than the com- reason different legionella treatment soluti- fort requirement, one stream of the prehe- on have been described and compared. In ated DHW is further heated and stored in general, the Legionella treatment solutions the micro storage tank. To meet the requi- include thermal treatment, chemical treat- rement of Legionella prevention, the DHW ment, physical treatment and other alterna- in the tank is heated to 60 °C by the electric tive methods. Such treatments aim at eit- immersion heater. When DHW draw-off oc- her killing the bacteria present in the water curs, the DHW from the tank is mixed with or prevent the spread of Legionella by limi- the hot water heated by the heat exchanger. ting the bacteria multiplication within a safety margin. 4.4.4 Conclusion The low temperature district heating (LTDH) 4.5 Control of space heating concept aims at reducing the supply temperature, while still fulfilling comfort requi- 4.5.1 Supply temperature for LTDH rements for domestic hot water and space heating. A well-designed and functioning It has been proven that LTDH can meet space DHW system must fulfill the requirements heating (SH) demand for both low-energy for hygiene, thermal comfort and energy ef- buildings and existing buildings with floor ficiency. One of the major barriers to im- heating (see chapter 7 and Brand 2014). plementing LTDH is the increased Legio- For existing buildings with the existing ra- nella risk with supply temperatures close diators, LTDH can meet SH demand for a to 50 °C. A literature survey was conducted certain amount of time of the year, while the in order to identify DHW supply regulations supply temperature needs to be increased in IEA DHC participating countries. Most of during cold winter period. To ensure con-

28 sumer thermal comfort while saving energy be achieved but in cold periods higher tem- and reducing network return temperature, peratures have to be accepted. the hydronic system in the SH loop need to Therefore it is proposed to develop new be properly designed and functioning. type of smart thermostatic radiator valve with a return temperature sensor. Such a 4.5.2 Control of SH supply and return TRV could secure a low return temperature temperature even if the TRV is not used in an optimal way. For this smart TRV the allowable re- In general there are three connection prin- turn temperature need to be adapted ac- ciples for connecting the space heating in- cording to the outdoor temperature. Fur- stallation with the DH network, thermore, the radiators need to be designed to deliver low desired return tempera- a) indirect connected, tures at peak demand (they need to be big b) direct connected with mixing loop and enough) otherwise insufficient heat is deli- c) direct connected. vered to the room at cold outdoor temperature and peak demand. Figure 4-21 shows the indirect connected SH system (Thorsen and Gundmundsson 2012). Floor and wall heating control In case of floor heating installation, the maximum supply temperature requirements are Radiator space heating control typically around 40-45 °C, which causes no Although space heating control when apply- problem for the application of low tempera- ing LTDH is in general the same as when ap- ture DH. plying traditional DH, there are some points As with radiator controls, it is important to ap- that differentiate. Due to the reduced supply differential pressure controllers to achie- ply temperatures, it becomes very impor- ve the optimum operating conditions for the tant to achieve accurate control to limit the floor heating installation. The flow rate is -ty flow rate and achieve the design cooling of pically regulated by a room thermostat. the supply. To ensure minimum cooling of the supply re- To minimize the risk of overflow in radiators turn temperature limiters should be applied. thermostatic radiator valves (TRV), a pre- setting function should be used. The purpose of the thermostat function is to adjust the flow to achieve the desired room temperature. The purpose of the pre-setting is to limit the maximum flow through the valve at design condition. Properly set pre-set function will significantly increase the hydraulic balance in the heating loop. To ensure proper operating condition for the TRV’s, it is important to install a differenti- Figure 4-21 Indirect connected SH substation © Danfoss al pressure controller. The differential pressure controller will ensure a stable differen- 4.5.3 Mass flow control tial pressure at the correct level across the In a traditional DH system, in the secon- heating installation. dary side, i.e. the building heating system To limit the impact of wrong setting of the is operated using self-acting control valves TRV, a thermostatic return limiter can be in- and a circulation pump. The supply water stalled at the radiators. The purpose of the temperature on the secondary side is ad- return limiter is to ensure minimum cooling justed as a function of the outdoor tempe- of the supply. The function of the return li- rature to meet a certain heating demand. To miter is that it closes if the outlet from the keep the supply water temperature at the radiator is higher than the set point. Most of desired value, the primary side flow to the the year a return temperature of 25 °C can heat exchanger is controlled using a moto- www.iea-dhc.org 29 rized valve. Pressure and the supply tempe- mand are commonly used to control the rature in the whole DH network are genera- flow. For the pump control philosophy wa- ted and adjusted at a centralized location, ter flow on the primary side of the heating which is usually the heat production plant. heat exchanger is adjusted in order to have Actual customers’ pressure differences and a constant secondary side supply tempera- supply water temperatures depend on their ture, which is done by changing the rotation speed of the primary side pump. Idea of the new pumping system is not only to overcome pressure losses in the substation but also to function as weather compensators by ad- justing the secondary side temperature levels according to the outdoor temperatures.

4.6 Integration of small scale decentralized heat sources Figure 4-22 Mass flow concept. The secondary side and primary side pumps District heating systems have historically are controlled to receive equal flow rates and temperature consisted of large-scale conventional pro- differences for primary and secondary sides of the heating heat duction units owned by energy companies. exchanger. (Laajalehto et al. 2014) As the knowledge and awareness of environ- locations on the network. mental problems (e.g. climate change and The mass flow control concept refers to a air pollution) grows, there has however been system where both the primary and secon- a change in the approach (see chapter 3). dary side flows are adjusted with inverter- This has led to a demand for higher integra- controlled pumps instead of control valves in tion of renewable energy in our energy sup- ring networks (Kuosa et al. 2014). The flow ply and more resource efficient energy sys- adjustment is carried out by controlling the tems, as LTDH schemes (Lund et al. 2014; rotation speed of the pumps. When heat is Frederiksen and Werner 2013). not required in a building the speed of the There is a huge potential to supply district pump is about 10 Hz and the pressure los- heating systems with heat from small, dis- ses of the substation block the flow through tributed sources such as industrial surplus the substation. heat, solar thermal systems, crematories One possible philosophy of controlling the and cooling machines in offices, sport faci- pumps is presented in (Laajalehto et al. lities and grocery stores. The main advan- 2014) where secondary side pump is con- tage of LTDH is that especially waste or re- trolled in order to receive a constant return newable energy sources with low tempera- temperature from radiators. In modern sys- ture levels can be efficiently integrated into tems TRVs or other mechanics to individu- the schemes (see chapter 2). These sour- ally adapt the heat supply to the heat de- ces are utilised directly where ever possible. Heat pumps are used with high efficiencies to boost the temperature level if the temperature levels of the source are not sufficiently high for the supply. There is a growing in- terest in the integration of solar thermal collectors in the heat supply of district heating systems in the so-called solar district heating in a number of countries (Dalenback 2015, Schäfer and Mangold 2015, Rühling et al. 2015 or Lennermo et al. 2016). Ano- ther idea is that customers buying heat from the DH companies are also able to sell heat to the grid. Prosumer is a concept that is Figure 4-23 Examples of decentralized solar thermal systems with primary becoming more and more common in or- and secondary connection (Lennermo et al. 2016). der to describe a district heating customer 30 that both buys and sells district heat. Pro- heating grid heating grid heating grid sumers may be part in future smart energy heat systems (Brange et al. 2016 and Lenner- source mo et al. 2016). There are many questions that must be answered before a decentralized heat source can be used in a DH system. An important point to start with is to decide what kind of heat source shall be used and where to connect it to the grid. In big DH systems it is not a big technical problem to integrate a return/supply return/return supply/supply feed-in feed-in feed-in small heat source into the scheme as long as the feed-in temperature is sufficiently high Figure 4-24 Schematic representation of the three feed-in variants with for the supply. But if there are many feed-in pumps (upper row) or with an adjustable flow resistant (lower plants or one feed-in plant is large in compa- row) (Schäfer and Mangold 2015) rison to the DH system, the proper regulati- network and it does not influence the heat on and dimension becomes more important. extraction efficiency of other heat sources, and the supplied heat is provided at a di- 4.6.1 Connection variants for rect useable temperature level. This variant decentralized feed-in is feasible in most applications. There are mainly three possible/common variants for the feed-in of heat from decen- Extraction from the return line and feed-in into tralized sources into district heating grids. In the return line (R/R) the following they are listed and described In this variant, heat transfer medium is ex- with their particular advantages and disa- tracted from the return line of the district dvantages. A schematic representation of heating grid and supplied back into the re- the variants is shown in Figure 4-24. The turn line after the heating process. The li- combination of these variants and a transfer mits of the temperature rise are common- station is also possible (Schäfer and Man- ly set by the district heating operator (com- gold 2015). mon are 5 K to 15 K). The mass flow needs to be regulated according to the require- Extraction from the return line and feed-in into ments to the feed-in temperature. The pres- the supply line (R/S) sure difference at the feed-in point is rela- The heat transfer medium is extracted from tively low. The comparable simple regulati- the return line of the district heating grid, on of the mass flow can be done via a pump heated by the decentralized source and fed- or via an additional adjustable flow resistant in into the supply line. The necessary tem- in the return line of the district heating grid. perature difference is dependent on the The flow direction of the heat transfer me- operating conditions of the district heating dium needs to be known for the correct de- grid and on the specifications of the grid sign of the connection and the position of the operator. This will result in changing opera- pump. Grid operators try to avoid additional tional conditions. The mass flow in the trans- flow resistances in their grids since they re- fer station has to be adjusted according to sult in higher energy demand for the central the requirements to the feed-in tempera- supply pump for the grid. The use of pumps ture. The pressure difference at the feed-in in the decentralized feed-in connection is point can be high for this variant and could not possible for grids with changing flow di- result in pressures up to several bars depen- rections, e.g. in a small loop of the network. ding on the actual location in the grid. This The changing flow direction would mainly be may result in a high energy demand for the an issue in a small loop of the network. Be- mandatory feed-in pump. The grid opera- cause of the comparable low temperature tors commonly prefer this variant as the re- differences this variant is preferable for de- turn temperature in the grid is unchanged, centralized heat sources with high efficien- which avoids temperature strain on the pipe cies for lower temperatures, as solar ther- www.iea-dhc.org 31 mal plants and heat pumps. However, the First after a careful assessment of the abo- grid heat loss will increase and there might ve mentioned issues the utilization of an ad- be a negative impact on the central heat ditional heat source should be taken into supply/generator by this connection variant consideration. because of the raised return temperature. Solar thermal collectors Extraction from the supply line and feed-in into Depending on the collector type (flat pla- the supply line (S/S) te, vacuum tube, etc.) solar thermal sys- In this variant the supply line is used instead tems can produce the feed-in temperature of the return line, as mentioned above. The in a wider range. In general, higher requi- heat transfer medium is extracted from the red feed-in temperatures are causing lower supply line, heated and supplied back into efficiencies in the solar thermal system. To the supply line. The allowed temperature maximize the yield it is important that the di- increase is prescribed by the heating grid mensioning and regulation of the system gi- operator, similar to the R/R case 5-15K. Fur- ves as low as possible return temperature to thermore, additional heat losses will occur in the solar collectors. The heat power produc- the grid because of the increased tempera- tion from a solar thermal installation varies a ture level in the supply line. The compara- lot over the day, between days and over the ble simple regulation of the mass flow can year. Further, the heat output can vary a lot be done via an additional pump (information where the plant is situated. The additio- on about flow direction in the grid manda- nal use of thermal storage devices may in- tory) or via an adjustable flow resistance in crease the plant utilization through decou- the heating grid. The resulting high tempe- pling of the supply from the solar plant and rature level for the feed-in will cause lower the demand of the district heating system. yields for decentralized heat sources with To get the most out of solar thermal system high efficiencies for lower temperatures, as these heat plants are normally coupled with solar thermal plants and heat pumps. a large thermal storage, which can store the The last described variant, extraction from heat over one or more days and even bet- the supply line and feed-in into the return ween seasons. line (S/R) is seldom used and the last possible variant extraction and supplying to the Industrial waste heat recovery supply line (S/S) is commonly not used, but Industrial heat recovery is commonly used discussed in detail and mentioned in (Len- from big industrial plants in a number of nermo et al. 2016 and Lennermo 2016). countries. But it is hard to find examples of installations from smaller plants. 4.6.2 Decentralized (waste-) heat Normally, boundary conditions for the use of sources waste heat from these plants are very individual and must be treated as such. On the For the connection of a decentralized heat one hand, there are systems with fixed ex- source to a DH system some details need cess heat power production and an annu- to be considered. Few of the most impor- al operation for more than 8,000 hours. On tant points are: the other hand, there are systems with fluc- • Overall cost efficiency of the integration tuations in the heat output, e.g. following a as well as cost and environmental im- varying production. Lower required feed-in pact/benefits of the new heat source. temperatures are a general advantage since • Possible feed-in temperature. The stan- the amount of waste heat is larger for lower dard should be that the feed-in tempe- temperature levels and more industrial pro- rature is similar to the temperature set- cesses might be connected to the DH grid. point of other plants in the DH system. In case of very low waste heat temperatu- • Variation in heat power production. Pro- res heat pumps can be used to boost the duction time, when and how many hours temperature levels to the required feed-in a day, a week and over a whole year. temperature. • Possibilities to regulate the heat source are of advantage. 32 Waste heat utilization from compressor 2015) detailed information on decentralised machines, chillers feed-in is given. In the example of the city Compression chillers need to emit heat of Ludwigsburg/Germany (see also chapter from their condensers during operation. 7.2.2) a prosumer substation is applied in a This waste heat can be utilized in DH sys- local micro-net: During high solar yield the tems, especially when the chillers are wor- surplus heat generated in decentralized so- king continuously. Chillers operating conti- lar panels is transferred to the micro-net and nuously are used for example for cooling of vice versa when the solar heat is not suffici- data centers and supermarkets. In Viborg, ent (Hassine et al. 2015). Denmark, it is planned to utilize the waste Figure 4-25 shows the hydraulic integration heat from data center chillers (see chapter of the solar system for a typical substation 5.3.3) (Diget 2015) example of waste heat in Germany. The components of the subs- from cooling units in supermarkets can be tation are the buffer storage tank with DHW found for example in Høruphav in Denmark. preparation (middle/right) and a heat ex- (Thorsen et al. 2016) changer for grid connection. For simulation purpose the system is modified to become Geothermal heat a prosumer system, a solar thermal collec- The heat extracted by geothermal plants tor and two additional heat exchangers have (here we are referring to shallow geother- been added for feeding solar heat directly mal installations, it is from less than 100-me- into the buffer (first priority of the control) ter-deep boreholes) can have a wide tempe- or to inject the heat into the grid (when the rature range, in some cases the heat can be tank is fully charged). used directly and in other cases it may requi- For single-family houses (SFH), the smaller re to be raised with a heat pump. Geother- (right) DHW storage tank with a capacity of mal plants are typically designed for supply- 500 l is exchanged by an instantaneous heat ing base load since they generally have in- exchanger. Otherwise, the heat exchangers itial investment cost but low operating cost in the two systems are identical. The larger and can be operated all year round. DHW storage tank (left) is 825 l for SFH and 1,000-2,000 l for MFH. 4.6.3 Example of a district heating grid Figure 4-26 shows the simulation results of integrating decentralized solar operating the transfer station (SFH) in July. thermal plants The supply temperature at the network node (dark blue) varies between about 130 °C As mentioned above, one commonly used (heat injection of surplus energy to the net- decentralized heat generation technology work) and 65 °C as a nominal supply line is solar thermal collector. In (Hassine et al. temperature during normal operation. The-

Figure 4-25 Hydraulic connection of decentralized solar plant to existing substation (MFH) (Hassine et al. 2015) www.iea-dhc.org 33 se excessive fluctuations might have an impact on the pipe network. The sloping lapse of the supply line temperature can be explained by the consideration of thermal losses of the network during operation and standstill. It can be seen that the grid has not been used as a heat source for the entire week of July (default value for consumer/prosumer switch = 0 also for standstill). In the months of June, July and August, the amount of solar supplied heat to the grid (green bars) exceeds significantly the re- moval from the network, as shown in Figu- re 4-27. Figure 4-26 Thermal behavior of SFH prosumer substation for a week in July More details of this project can be found in (Hassine et al. 2015) (Hassine et al. 2015).

Figure 4-27 Details of energy or DH-network maximum collector outlet 130 °C (Hassine et al. 2015)

34 5 INTERFACES AND COMMUNITIES

5.1 Introduction In this chapter interfaces in the district heating systems context present different types of links between heat supply and demand of buildings by means of water-based systems. The technical and research field of the interfaces covers a broad range of issues as shown in Figure 5-1. The challenge of the improved interfaces in district heating systems may be explained via so-called hard and soft issues: • The hard issues cover the following topics: District heating network structures, Figure 5-1 Big picture of interfaces in district heating systems requirements for consumer substations and buildings, and connection princip- 5.2 Predicting DH demand and future les for distributed heat sources. development • The soft issues cover the following to- Energy efficiency in buildings has been an pics: technical and economical model- important topic since 1970 and has been ling of the distribution system, optimi- widely recognized as an option to decre- zation between demand and generati- ase energy use. For that purpose, diffe- on side, innovative control concepts and rent tools, methods, standards, and busi- energy measurement, transition of the ness models have been developed (Nord existing DH grid to the LTDH grid, and and Sjøthun 2014). The recast of the di- new pricing and business models. rective on the energy performance of buil- During the course of the project promising dings (EPBD) established the political tar- models, concepts, and technologies to meet get of nearly zero energy buildings (nZEB) the goals of future renewable based com- for all new buildings by January 2021 (EU- munity energy systems have been collec- Directive 2010/31). The topic of zero energy ted and identified. Some of the relevant buildings (ZEB) has been important in the technologies have been described in chap- last years (Kurnitski et al. 2011, Nielsen and ter 4, as new pipe technologies, substati- Möller 2012, Li et al. 2013, Marszal and Hei- on configurations, and renewable technolo- selberg 2011, Osmani and O‘Reilly 2009). gies. This section aims to provide an over- nZEB and ZEB have to be actively connec- view on the most relevant topics and issues ted to the energy systems to fulfill their re- related to the interfaces in the district hea- quirement. Regardless of the energy requi- ting community. rements for new buildings, most of today’s As possible to note from Figure 5-1, the in- buildings are existing buildings. Therefore, terfaces issue is highly relevant for a suc- energy planning and management of the cessful implementation of the LTDH and future integrated energy systems has to in- thereby enabling transition to the renewa- clude a variety of different buildings. Due to ble energy society and secure energy sup- different building purposes, occupant beha- ply for future development of society. By in- vior, and operation and maintenance, buil- troducing better interfaces between the de- ding energy use is a complex system with mand and supply, DH systems can be trans- emergent behavior (Guckenheimer and Otti- formed into a smart grid energy system on no 2008). Therefore, forecasting future buil- a district level. ding heating demand should be based on stochastic methods (Andersen et al. 2000) and combination of statistical and physical methods (Lü et al. 2015). www.iea-dhc.org 35 An analysis on development of the heating explained in (Ingebretsen 2014) and line- demand until 2050 was made based on ar models for the building stock develop- the Norwegian building statistics of the cur- ment shown in Figure 5-2, a projection of the rent residential building stock and forecasts heat demand development until 2050 was for the residential building development in obtained as shown in Figure 5-3. It should Norway found in (TheLowEnergyCommittee also be noted that in Figure 5-3, increase of 2009). The aim of the analysis was to show the building stock was not counted, which change in total heat demand due to ener- could change the total heat demand. In the gy efficiency in buildings and market pe- case of the building stock increase, the to- netration of the new houses. Based on the tal heat demand would be the same or hig- current statistics, there are 61.7 % of ol- her in the future regardless of the market der buildings, 35.1 % of intermediate buil- penetration of low energy and passive hou- dings, and 3.1 % of low energy buildings, ses. In addition, Figure 5-3 gives heat de- and 0.1 % of passive houses. Linear models mand in the case of ambitious and conser- for the building stock development were as- vative development of the building stock. A sumed based on (Li et. al. 2015), as shown change of ± 20 % deviation of the normal in Figure 5-2. The models assumed that the development, given in Figure 5-2, was int- growth rate for new buildings is 1.33 %/year, roduced to produce ambitious and conser- renovation rate is 1.5 %/year, and demoliti- vative development, respectively. on rate is 0.6 %/year (TheLowEnergyCom- From Figure 5-3 it may be concluded that mittee 2009). An imaginary area presenting even with the ambitious scenario for the resi- a residential building stock with a heat de- dential building development, the total heat mand of 80 MW was introduced. demand would decrease by about 18 % in By using the results on the heat demand, 2050 compared to the current heat demand. This means that the DH would still be needed for most of the buildings in 2050. Based on this, the LTDH is expected to be a promising heat technology for the future. In the analysis in Figure 5-2 and Figure 5-3, market penetration of nZEB was not included. However, a study shows that the excess heat from nZEBs can benefit DH systems by decreasing the production from the centralized units (Nielsen and Möller 2012). Re- search on the distribution and investment issues of the DH systems show that the most favorable conditions for the further development appear in large cities and that in the- Figure 5-2 Forecasting of the building stock development in Norway se areas there is low risk for reduced competitiveness due to reduced heat demand. Hence, reduced heat demands are not barrier for DH in the future (Persson and Wer- ner 2011). Regarding energy sources for the DH in the future, a thorough research on sustainable heat potentials at the Euro- pean level shows that there is enough available heat, but policy measures are necessary for realization of all the potentials (Pers- son et al. 2014).

Figure 5-3 Heat demand development for the residential building stock in Norway (Fossmo and Skrauvol 2016; Nord et al. 2016) 36 5.3 Distribution and development issues One of the main ideas of the LTDH is to enable easy integration of the renewable distributed energy sources. Renewable energy and waste heat sources together with heat storages may be organized as decentralized or distributed. Decentralized systems imply that heat supply is divided into several plants geographically decentralized, but centrally organized. The situation with distributed energy sources will appear when single buildings, industrial plants, and any other actors are enabled to deliver their renewable or waste heat to the DH system. Figure 5-4 Heat distribution losses as function of the linear heat density in To enable a well-functioning and renewab- Denmark for plants (Verenum 2014) le DH system with many actors, good knowledge on DH operation, component behaviour, and requirements for the grid connection are highly necessary. All these issues are important to identify in a correct way a cost and responsibility share in the system. The distribution of costs of heat losses should be treated in a simple way, since it is to be accepted that heat is lost in the distribution network and all consumer need to share that cost.

5.3.1 Heat losses and pipe reliability issues Reliable distribution system is highly neces- Figure 5-5 DH heat losses for separate plants in Denmark sary to realize the ideas of the LTDH and stay (Dansk Fjernvarme 2017) competitive on the energy market. Therefo- re, knowledge on the heat losses and pipe reliability is highly necessary. It is difficult to identify high quality data on heat losses in the DH systems for different plants. Some pipe producers provide small calculation programs to calculate heat losses in pipes. However, pipe producers are able to provide information about the heat loss coefficient of their pipes. The heat loss coefficient can then be used to estimate the heat loss under various operating conditions. A methodology for the pipe network cost Figure 5-6 DH heat losses on national level in Norway models including pipe heat losses and heat (Statistics Norway 2017) density has been suggested in (Kristjans- son and Bøhm 2008). Statistical data on tries and DH companies register their histo- the heat losses provided from the bran- rical and operational data in different ways. ch organizations and on the national level Usually, heat distribution losses as a func- does not give a good indication how operation of linear heat density, as in Figure 5-4, tion and temperature levels may contribu- may be found. te to the distribution losses. Different coun- www.iea-dhc.org 37 As expected the general conclusions from the available data on the heat losses in the DH is that smaller DH plants and low linear heat density tend to have higher heat losses in percentage, see Figure 5-4 and Fi- gure 5-5. Difficulties in collecting data on heat losses in the DH system may be noted in Figure 5-5. Someone may question some of the values in Figure 5-5, because some plant had heat loss of 94 %. However, such data points may be due to typing fail Figure 5-7 Percentage of DH distribution heat losses in Germany by years in the database or wrong calculation. This (AGFW 2014) conclusion indicates that a better monito- By using annual statistical data from Da- ring of the DH network and smart thermal nish DH plants, it was possible to give re- grids are highly necessary for the LTDH and lationship between the heat losses and de- transition to the renewable society. A general livered heat, as in Figure 5-5. It should be overview on the German national heat los- noted that varying pipe sizes, piping princip- ses indicated that the heat losses have been les and pipe insulations applied in different in the range of 13 to 14 %, see Figure 5-7. networks are not considered in these data. Regarding pipe reliability of the DH network, On the contrary, in Norway it is not possib- a thorough review identifies and classifies le to find so detail data on distribution heat the most relevant factors leading to pipe de- losses as in Denmark. The annual data on terioration as shown in Table 5-1 (Teresh- the national level may be found in Norway chenko and Nord 2016). A good database as shown in Figure 5-6. Similar data were should include well organized data shown in found for Germany, see Figure 5-7. Table 5-1. Implementation of new IT-technologies should enable this.

5.3.2 Integration of renewable energy Table 5-1 Summary and comparison of the characteristics for connection sources of local heat sources To enable transition to the renewable energy Environmental Operational Physical factors factors factors society and secure energy supply for future development of society, integration of distri- Pipe age and material Pipe bedding Internal pressure buted energy systems is highly necessary. This will induce a new actor at the DH mar- Pipe wall thickness Trench backfill Leakage ket called “prosumer” (Brange et al. 2016) that may be treated as third party access. Pipe vintage Soil type Water quality A prosumer is a customer that both produces and consumes heat from the DH sys- Pipe diameter Groundwater Flow velocity tem. This concept offers great opportunities for successful utilization of solar heat into Type of joints Climate Backflow potential the DH and supports the transition to smart thermal grid. The concept of “prosumer” is already known from application in power Thrust restraint Pipe location Operational and sector (Schleicher-Tappeser 2012 and Men- maintenance niti et al. 2013). In the DH context, this will Pipe lining and Disturbances practices coating imply that customers may have possibility to Stray electrical deliver excess heat from distributed renewa- Dissimilar metals currents ble energies (e.g. solar heat, heat pumps, and waste heat) to the DH network. There Pipe installation Seismic activity are different approaches for the prosumer connections, depending on the DH network Pipe manufacture temperature level, delivered heat tempera-

38 ture level, and building requirements, see necessary to analyze pipe sizes before int- chapter 4.6 Prosumer may deliver their heat roducing prosumers and size the pipes for into the supply or return line. The concept of heat production instead of just heat use. In- exporting excess heat from the cooling ma- troduction of the prosumers will may cause chines (CM) to the DH network is shown in a bidirectional flow in the DH pipe network Figure 5-8. as it is actually very common in DH systems Under the case a) in Figure 5-8 it is assumed with pooled heat sources. Further the prosu- that the DH network and buildings need hig- mers may create own pressure cones resul- her temperature and therefore a heat pump ting in high differential pressures for some (HP) is necessary to increase the tempera- of the consumers close to the prosumers. ture of the prosumer heat to the required In general distributed heat sources / prosu- temperature level. In the case b) in Figure mers will reduce the overall pressure diffe- 5-8, the excess heat is directly exported to rence in the system. To enable higher heat the DH grid, while buildings may have pos- share from the prosumers, it might be ad- sibility to increasing the temperature level, vantage to allow lower initial pressure diffe- by including an electric boiler for heating rence from the main plant. The initial pres- the tap water. sure at the plant is generally controlled ac- With increasing the number of prosumers in cording to the differential pressure at the cri- the DH system, a transformation of today’s tical user. However, this differential pressu- DH network into a smart thermal grid is high- re requirement from the critical user should ly necessary. The introduction of prosumers be considered. (Lennermo 2016 and Brand to the DH will affect both the DH network et al. 2014). Therefore, new control strate- and the customers. gies for the differential pressures are high- When prosumer are introduced into a DH ly important to enable proper operation of scheme, network operators should consider the whole DH system with the prosumers. lower DH temperatures because of: 1) lower temperature requirement for utiliza- 5.3.3 Successful examples of integration tion of renewable and waste heat and of excess heat 2) renewables produce heat with higher ef- Nowadays datacentres need lots of cooling, ficiency at lower temperature level. This can while condensers of the cooling plants may only be done taking the minimal tempera- provide heat for useful purpose. Integration ture requirements of the connected buil- of the excess heat may be done in the sup- dings into account. ply or in the return line of the DH system. Heat production from the prosumers to the Viborg DH in Denmark is an example where DH network will influence pressure levels in the surplus heat from a new Apple computer the DH network. When the prosumers pro- center will be rejected to the DH system (Di- duce at their maximum, the water veloci- get 2015), see Figure 5-9. To provide heat ty in the pipes will increase. Therefore, it is for the DH system, heat pumps are imple-

Figure 5-8 Examples of waste heat integration into DH – a) with heat pump for higher temperature level and b) low temperature DH network (Brange et al. 2016) www.iea-dhc.org 39 mented, thus providing directly supply water for the DH system of approximately 50 °C. Viborg DH-company had a long-term plan for decreasing the DH temperature and distribution losses, see Figure 5-10 (Diget 2015 and Viborg Fjernvarme 2011) This has been done based on considerations to optimize the network operation and because of realizing a better business case via reducing the temperature in the network. Opening of Apple data center fitted very well into the strategy of Viborg DH. Customers with the high temperature requirements will be grou- ped and provided with an additional heat pump for increasing the temperature level. In Trondheim, Norway, excess heat from cooling the datacenter at the university campus is utilized by connecting in the return line, see Figure 5-11. The reason for this was currently high temperature level requi- Figure 5-9 Example of waste heat based DH in Viborg in Denmark rement from the existing buildings at the (Diget 2015) campus. To enable integration of the excess heat, the university campus separated from the main connection to Trondheim DH by using heat exchangers and establishing own DH ring. In that way, it was possible to control the supply and return water temperature in the university DH ring and utilize excess heat from the datacenter. Proper control was enabled easily because university is property owner and has own maintenance service with a powerful building energy monitoring system for the entire campus. Currently, the Figure 5-10 Planned decrease in the DH distribution heat losses in Viborg excess heat may provide the base heat load DH to enable utilization of excess heat from the datacenter in the range of 1 to 1.2 MW the entire year. (Viborg Fjernvarme 2011) 5.4 Optimization, interaction, and energy measurement To enable low supply temperature in the DH system, it is highly important to decrease as much as possible the return temperature. Importance of the low return is pointed out in Section 5.3 for the purpose of integration of the renewables and excess heat. An approximate calculation shows that the economic value of reduced return temperature can vary from 0.05 to 0.5 EUR/MWh°C (Fre- deriksen and Werner 2013). A big problem in achieving low return temperature is poor substation control. Different faults induce Figure 5-11 Use of excess heat at NTNU in Trondheim, Norway problems with high return temperature in (NTNU Property owner 2012) the consumer substations, see Figure 5-12. Control and set points are causing most of 40 the issues in achieving the low return temperature. Therefore, fault detection and di- agnosis (FDD) of the consumer substations is highly important in achieving low return and consequently low supply temperature in the DH system. Wireless and smart metering technologies may provide lots of data on the substation performance and the DH network. By transforming these data into information, it is possible to improve the overall system operation and optimize the overall system perfor- Figure 5-12 Amount of fails in the consumer substations mance considering together DH companies (Frederiksen and Werner 2013) and consumers. Better data utilization may using renewable energies for heating. An ex- create new business development and build ample of solar heating plant is in Marstal on new business models tying utilities, ener- island Aerö, Denmark. The 33,400 m² so- gy companies, and consumers tighter to- lar collectors combined with the 75,000 m³ gether. New business models may be rele- thermal storage provide 55 % of the annu- vant for the DH companies and new actors al heat demand. The district heating com- on the market. For the DH companies, this pany is citizen-owned. In Gothenburg, Swe- may imply that they can take over operation den, owners of the DH connected buildings and maintenance of the consumer substa- installed large solar collectors. In this case, tions and operate them in the optimal way the solar heat is first used in the buildings. for the DH plant and costumers. In addition, When the solar heat production exceeds the new companies transforming data into use- heat demand of the building, it is exported ful information by using the newest IT-tech- to the main DH network. The DH network is nologies and advanced control may be de- kind of storage for the solar heat. In this ex- veloped. An example for such company is ample, where the building owners installed NODA in Sweden. This company is dealing the solar collector, a problem with delive- with big data applications for energy heating ring less heat then expected has been noti- systems (Noda 2017). ced. In Austria, Energy Service Companies (ESCO) own and operate the solar heating 5.5 Pricing and business models system. This means that ESCO is the third District heating pricing is a core element party company (Dalenback 2015). in reforming the heating market, because Based on the available data on the solar heat the heat price and price for the heat ex- production, it seems that the price and busi- port will influence decision on energy sour- ness models in Denmark resulted in a very ce and an active customer role. Existing DH high share of the solar heat into the DH sys- pricing methods, such as the cost-plus pri- tem. In addition, the Danish DH solar sys- cing method and the conventional marginal- tems are rather big plants than many small cost pricing method, cannot simultaneously plants. In this model where the solar heat provide both high efficiency and sufficient plant is owned by the DH companies, pro- investment cost return (Zhang et al. 2013). per operation is directly provided enabling The cost-plus pricing method is often used desired temperature levels and operation. in regulated DH markets. The marginal-cost pricing method is commonly utilized in de- regulated markets (Li et al. 2015). Regarding excess and solar heat delivery to the DH system, several price and business models have been developed. In Denmark, DH operators are mostly organized in coope- ratives. Their goal is not profit maximization, but to achieve a long-term favorable price www.iea-dhc.org 41 6 CALCULATION TOOLS FOR DISTRICT HEATING SYSTEMS

6.1 Introduction outlined and developed: Easy District Ana- lysis (EDA). EDA is a simplified DH plan- During the course of the work within Annex ning tool for urban planners for the energe- TS1 a methodology for assessing and analy- tic, ecological and economic analysis as well zing procedures for the optimization of local as the evaluation of urban districts. energy systems with focus on DH has been In the following the results of the survey on identified and adapted. Furthermore, a sim- local and DHC models are described and plified planning tool for DH is developed and evaluated. The developed Easy District Ana- advanced tools for design and performance lysis (EDA) tool is then presented and ap- analysis of local energy systems, which are plied to a case study of an urban district con- based on DH, are further developed. sisting of 140 multi-family houses. The presentation of tools in this chapter is part of the German contribution to the An- nex and a summary of the full report (Blesl 6.2 Description of Planning Tools for and Stehle 2017). District Heating For the evaluation of existing local and DHC Based on the survey results on local and models, a classification form was created to- DHC models, twelve planning tools for DH gether with Annex TS1 participants to con- are briefly described in the following. As a duct a survey on planning tools for DH. The first step, the analyzed planning tools are di- used classification categories are summa- vided according to their analytical approach: rized in Table 6-1. energy system models, thermodynamic mo- Input from Annex participants (in total twel- dels and others (see Table 6-2). ve planning tools) could be gathered and Energy system models describe energy flows evaluated to formulate requirements for the from primary energy over transformation, development of a simplified DH planning transport and distribution to final energy and tool and to further develop an existing ad- useful energy. They are therefore suitable vanced tool (TIMES Local). Based on this, for an integral approach on low temperature a new simplified planning for DH has been DH. However, heat distribution and different temperature levels are often not modelled in Table 6-1 Classification categories for the evaluation of planning tools for energy system models in detail. district heating Thermodynamic models are therefore also in- Analytical Approach Demand Categories cluded in the survey on local and DHC mo- Energy System Model Households dels in order to consider heat grids along with their hydraulic and thermodynamic charac- Thermodynamic Model Commercial teristics as well as different supply tempera- Industry ture levels of renewable energies (e.g. solar Target Audience Transportation thermal, geothermal, heat pumps) to feed Municipal Authorities into the heat grid. Models that neither described an energy Professional Planners Final Energy Consumption system nor thermodynamic characteristics Internal Use, R&D Electricity were classified asothers . Heat Level of Detail Transport 6.2.1 Energy System Models Geographical Scope In the following five energy system models Time Horizon Variables are briefly presented (including two models that also contain thermodynamic as- Costs pects): Model Type Energy EnergyPLAN, KOPTI, TIMES Local, LowEx- Simulation Model Exergy CAT and SIMUL_E.Net. Optimization Model Temperature

42 Table 6-2 Overview of planning tools from the survey on local and DH models Energy System Models EnergyPLAN KOPTI LowEx-CAT SIMUL_E.NET TIMES Local Termodynamic Models HeatNET LowEx-CAT NET Local SIMUL_E.NET spHeat Termis Others District ECA EME Forecast Exergy Pass Online EnergyPLAN at the Institute of Energy Economics and EnergyPLAN, developed at Aalborg Univer- Rational Energy Use (IER) at the University sity in 2000, is a simulation and optimizati- of Stuttgart in 2010. The focus lies on the on model to run a regional to national future heating market to optimize a local energy energy system in which the sectors power, system with the target of minimizing the to- heat and transport are linked via e.g. power tal system costs under defined constraints to heat or e-mobility. To integrate intermit- (e.g. CO2-reduction). TIMES Local enables tent renewable energy, the model is run in the energetic, ecological and economic ana- an hourly resolution with a time horizon of lysis of the heat and power supply of a city one year. The energy system (installed ca- taking into account the settlement and buil- pacities, energy demand) needs to be set ding structure of urban districts and its heat up by the user. The usage of technologies supply structure and alternatives. After the is optimized with the goal of minimum costs initial used technologies, the development or minimum fuel use. An example for model of energy demand, energy prices, etc. are application is a heating and cooling strategy set, the model decides which technologies for Europe in 2014 (Connolly 2014). are used to achieve a cost minimum solution. The model’s time horizon can be set up KOPTI to several decades on an hourly basis. An KOPTI (Kokonais OPTImointimalli, engl. example for model application is the Ger- overall optimization model) is an optimiza- man research project ‘EnEff: Stadt Ludwigs- tion model that was developed at VTT Tech- burg-Grünbühl/Sonnenberg’ in 2013 (Blesl nical Research Centre of Finland in 2003. It 2014a). Further details on TIMES Local are optimizes the run of a local energy system presented in (Blesl and Stehle 2017). with the focus on the DHC system (e.g. CHP, storages) including the power system under LowEx-CAT the goal of minimum costs of electricity, heat LowEx-CAT, Low Exergy – Cluster Analysis and cooling. Market heat and electricity pri- Tool, is a TRNSYS-based simulation mo- ces are considered in order to sell utilizati- del (Kallert 2017). The focus of the model on options to the market (Koreneff 2014b). is the integration of low temperature tech- KOPTI has been applied to ‘estimate the va- nologies (e.g. solar collectors, heat pumps) lue of distributed generation for the diffe- to supply districts by DH grids (considering rent power system actors’ (Koreneff 2014b). grid temperature, design and optimization of the grid distribution). The time horizon TIMES Local ranges from season to less than five years TIMES Local, based on the TIMES (which on an hourly basis. After the design of the was developed within a working group of the district energy system is set up, the operati- Energy Technology Systems Analysis Pro- on of an energy system is optimized by mi- gram (ETSAP) of the International Energy nimizing the degradation of exergy (exergy Agency in the 1990s) model generator, is efficiency). This enables the analysis of the an optimization model, that was developed energy and exergy impact of different ener- www.iea-dhc.org 43 gy strategies (Kallert and Schneider 2014). 2014). The model was applied for network The model is applied to several generic case calculation(s) in Finnish DH-systems, e.g. studies (e.g. Kallert 2017). Further descrip- Hyvinkää building exhibition area case, see tions of LowEx-CAT can be found in (Blesl chapter 7.2.1. and (Rämä 2014). and Stehle 2017). NET Local SIMUL_E.NET NET Local is a static temperature simulati- SIMUL_E.NET is a simulation model based on model for DHC grids that has been deve- on Simulink (MathWorks 2017) for new con- loped since 2012. It analyzes the influence cepts of DHC grids. It focuses on bi-literal of heat demand on different temperature heat trade between consumers and sup- levels of representative buildings or consu- pliers or between prosumers in a small grid mers on the grid temperature and possib- with several connected buildings. Although le supply types. This involves the evaluati- SIMUL_E.NET focuses on bi-lateral energy on of return line supply. Moreover, the tem- trades on the DHC network, it also considers perature change along the district heating supply technologies and is therefore also lis- grid with a regional resolution is taken into ted under energy system models. To realize consideration. The impact of different tech- these bi-lateral heat trades different variants nology options, such as solar heat integra- of Energy Management System (EMS) algo- tion, can also be considered. The calcula- rithms are analyzed (Im 2014). Aside the tion is carried out for one single demand grid and demand of buildings, supply and point with the output of the DHC grid tem- storage technologies are considered. Moreo- perature for feed line and return line in diffe- ver, different pipe configurations or tempera- rent supply regions. Model results are used ture levels can be taken into account to im- to verify optimization results of TIMES Local prove the efficiency of the grid. The model’s (see 6.2.1). Examples of model application time horizon is one year with an hourly re- are ‘Ludwigsburg Grünbühl’/Germany and solution. References for model use do not ‘Stuttgart West’/Germany (Blesl 2014b). exist so far. spHeat 6.2.2 Thermodynamic Models spHeat is a quasi-dynamic heat grid model that was developed in 2012. It performs In the following four heat grid models are a ‘hydraulic and thermal simulation of net- described briefly: works with multiple loop topologies’ focu- HeatNET, NET Local, spHeat and Termis. sing ‘on the impact of the spatial/geogra- phic load distribution on the performance HeatNET of the network’ (Hassine 2014). The time HeatNET, has been developed by the VTT horizon ranges from single design point to Technical Research Centre of Finland since one year on an hourly basis. The model’s 2005, is a district heating network simulati- outputs are pressure and temperature pro- on model with a dynamic temperature cal- files along the grid. Aside structural impro- culation. Time step and length of a simula- vement potentials spHeat can ‘analyze diffe- tion can be defined by the user, the most rent solar thermal energy supply strategies’ common simulation being a period of one (Hassine 2014). spHeat was used for case year with a time step of one hour. As input studies such as ‘Scharnhauser Park Ostfil- the user enters network related data (e.g. dern’ and ‘Sonnenberg Ludwigsburg’, both structure, pipe size, feed temperatures, and in Germany. More details on spHeat can be capacities) and defines the heat demand for found in (Blesl and Stehle 2017). heating and domestic hot water, as well as a set of consumer specific information such as e.g. heat exchanger parameters. The simu- Termis Termis is a heat grid model that was develo- lation of a district cooling network can also ped by Schneider Electric (Schneider Elec- be performed by HeatNET. The model deter- tric 2014) in 1988. It is able to perform both mines flows, heat losses and temperatures simulation and optimization of heat grids and pressures around the network (Rämä 44 both in planning and operation stage. How- EME Forecast ever, heat generation technologies such as Developed in 2002, EME Forecast is a heu- CHP are not considered. The time horizon ristic time series model to forecast electricity ranges from single design point to one year and heat loads on an hourly basis. The time with a time resolution from 10 to 60 minu- horizon can be adapted from single design tes or one year with twelve typical discrete point to ten years. It is used by VTT and a loads. Termis does also use real-time data Finnish power supplier. The approach is to (SCADA) to optimize grid parameters. The assume that a behavior of a variable in fu- model output is among other things the ‘pro- ture (e.g. DH load) can be derived from his- cess state of the network and network com- toric data. Therefore, the model needs both ponents’ (i.e. power, pressure, flow, tempe- history and forecast values of a variable that rature) (Outgaard 2014). Termis is not only the DH load is dependent of (such as the used by e.g. Danish consulting companies outside temperature) and history values of for design analysis or real time operation and the DH load itself. The forecasted hourly DH optimization, but also for projects in France, load is received by performing a heuristic Spain, USA, Poland, Serbia, China, etc. time series approach combined with a dynamic regression analysis (Koreneff 2014a). 6.2.3 Others A reference for model use is the end-user load forecasts by Koreneff in 2010. Aside from energy system and thermodynamic models, other analytical approaches Exergy Pass Online were considered in the following three mo- Exergy Pass Online, developed from 2012- dels: Firstly, District ECA is described as a 2015, is a tool for the exergy-based as- district energy concept tool for the assess- sessment of the resource consumption of ment of the energy potential and efficiency. buildings. Secondly, a heuristic time series model to The model enables the comparison of buil- forecast heat and electricity loads is regar- dings ‘to find the optimal combination of hea- ded: EME Forecast. Finally, a tool for the ex- ting, cooling, insulation standard and electri- ergy analysis of the resource consumption cal appliances’ in order to reduce resource of buildings: Exergy Pass Online. consumption and GHG emissions (Jentsch 2015). After specification of the building’s District ECA energy demand and selection of the supply District Energy Concept Adviser is a static technologies, the model’s output is a prede- and myopic simulation model that was defined result report (exergy pass) on resource veloped as part of the German EnEff:Stadt consumption (exergy), energy, GHG emissi- research activity in 2012 (Fraunhofer IBP ons and costs. In contrast to energy passes, 2014, ANNEX 51 2014). It is used by urban the exergy pass takes energy quality (Energy planners during the first stage of district con- quality can be described as the usefulness cepts. After the specification of the buildings of energy. Its unit is the maximum share of and the energy supply, the final energy con- energy that can be converted into electrici- sumption and CO emissions are calculated. 2 ty (Exergieausweis 2015)) into considerati- This allows comparing different energy con- on and uses exergy as an assessment para- cepts such as local district heating or the meter for the evaluation of energy systems use of gas condensing boilers. The regar- in the building sector. The exergy pass (only ded time horizon is one year with the same a German version available) will be used in time resolution. Moreover, District ECA ena- the EU project SUSMILK (Jentsch 2015). bles comparisons in energy use of a district with the national average and provides examples for energy efficient districts. Examp- les for model applications can be found in the German programme ‘EnEff: Stadt’, e.g. Stuttgart-Burgholzhof, Munich-Lilienstraße, Karlsruhe-Rintheim (Fraunhofer IBP 2014). www.iea-dhc.org 45 6.3 Evaluation of Planning Tools for 6.3.2 Evaluation and Comparison of District Heating Planning Tools for District Heating Based on the descriptions of local and DHC The classification results of the twelve ana- models in the last section, an evaluation of lyzed planning tools are summarized in Ta- them is carried out to identify integral and ble 6-3. Each tool is assessed in the abo- innovative approaches for low temperature ve-named seven categories (e.g. analytical heat supply at local level. This chapter con- approach), whereby green boxes in Table cludes with the requirements for the deve- 6-3 mean ‘true’, yellow boxes ‘partly true’ lopment of a simplified tool for DH, which and grey boxes ‘false’. For example, Dis- is presented in next chapter. trict ECA is suitable for the target audience of municipal authorities. In contrast, boxes 6.3.1 Methodology in grey mean that a model is not suitable, e.g. TIMES Local does not address to mu- To evaluate the survey results on local and nicipal authorities. DHC models, the gathered input is filtered The classification results, as shown inTab - and classified in seven categories (and some le 6-3 can also be used for a more accura- in subcategories): te application of the planning tools for DH. • analytical approach, In the following each category is evaluated • target audience, with regard to the analyzed planning tools. • level of detail (geographical scope, time horizon), Analytical Approach • model type (simulation, optimization), The analytical approach differentiates bet- • demand sectors, ween energy system models, thermodyna- • final energy consumption and mic models and other models. Energy sys- • solution variables. tem models cover the energy supply chain Each of these categories includes distin- from primary energy to useful energy, whe- guishing features which apply (green box), reas thermodynamic models focus on heat partly apply (yellow box) or do not apply networks. Models that did not fit in this clas- (grey box) to the analyzed model (see Ta- sification were classified as others. As ener- ble 6-3). gy system models were classified: Energy- The category analytical approach distingu- PLAN, KOPTI, TIMES Local, LowEx-CAT ishes between energy system model, thermo- and SIMUL_E.NET. The latter two can also dynamic model and other. Target audience be described as thermodynamic models. includes municipal authorities, professional Thermodynamic only models are HeatNET, planners and research & development / in- NET Local, spHeat and Termis. Classified as ternal use. The level of detail is split into other were District ECA, EME Forecast and the subcategories geographical scope (from Exergy Pass Online. DHC supplied area to region) and time horizon (single design point, <= 1 year, > 1 Target Audience year). The model type is classified insimu - The target audience can be divided into mu- lation, investment/design optimization and nicipal authorities, professional planners operation optimization. Whereas demand and internal use, R&D. The following models sectors were divided into households, com- address among others municipal authorities mercial, industry and transportation, final and can thus be described as rather user- energy consumption was allocated to elec- friendly tools: EnergyPLAN, Termis, District tricity, heat and transport. As solution va- ECA, EME Forecast, Exergy Pass Online. riables costs, energy, exergy and tempera- Anyway, most tools require at least trained ture were used. users, especially tools used by researchers or professional planners.

46 Table 6-3 Evaluation of twelve planning tools on the basis of classification categories (green = true, yellow = partly true, grey = false).

Exergy Energy TIMES LowEx- SIMUL_ Heat NET District EME Classification Categories KOPTI spHeat Termis Pass PLAN Local CAT E.NET NET Local ECA Forecast Online

l Energy System Model h a c c a t i o y r l Thermodynamic Model a p n p A A Other

Municipal Authorities e t c e n g e i r Professional Planners d a u T A Internal Use, R & D

Region e p o City S c

l a c i

h District l i p t a r a e g o

D Street e f o G

e DHC Supplied Area v e L n

o Single Design Point z r i o H

<= 1 Year Exergy e Energy TIMES LowEx- SIMUL_ Heat NET District EME m

Classificai tion Categories KOPTI spHeat Termis Pass

T PLAN Local CAT E.NET NET Local ECA Forecast > 1 Year Online

Simulation Model

e p y T

e Investment/Design

d Optimization o

M Model Operation

s DHC, DHC e

i Households r Electr. Sector o g

t e Commercial a C

d Industry n a m

e Transportation D

n y o

g Electricity r t i e p m E n

u Heat l s a n n i o F

C Transport

Costs s e l Energy b a i r Exergy V a

Temperature Level of Detail: Geographical Scope thermodynamic models HeatNET, NET Lo- The geographical scope ranges from DHC cal, spHeat, Termis, as well as District ECA, supplied area, street, district, city to a whole EME Forecast and Exergy Pass Online. region. Some tools are flexible in the geogra- phic scope (e.g. TIMES Local, Termis, EME Level of Detail: Time Horizon Forecast). Basically, most tools can cover a For the time horizon a distinction is made city level or parts of it (aside from Energy- between single design point (no time ho- PLAN that only models region and bigger). rizon), ≤ 1 year, > 1 year. A time horizon A DHC supplied area can be taken into ac- of up to one year can be modelled by any count by most of the tools: the energy sys- of the analyzed planning tools (except for tem models KOPTI and TIMES Local and the NET Local). Longer time horizons are co- www.iea-dhc.org 47 vered in TIMES Local (few decades), Lo- up heaters for DHW preparation, electricity wEx-CAT (less than five years), Termis (more generation is not taken into account). The than ten years) and EME Forecast (up to ten transport sector is of minor importance for years). A few tools model all three catego- district heating and thus only considered in ries of time horizon: Termis and EME Fore- one tool (EnergyPLAN). cast. Both NET Local and Exergy Pass On- line consider a single design point. Variables The analyzed solution variables are costs, Model Type energy, exergy and temperature. If they The models were classified in simulation are sorted by their frequency, the following and optimization, whereas optimization is ranking results: energy (almost in all of the further divided into investment/design opti- tools), costs (half of the tools), temperature mization and operation optimization. Simu- (five) and exergy (only in two). This ran- lation is part of any of the selected planning king indicates the relevance of the particu- tools. Even though TIMES Local is primari- lar variable for local and DHC modelers. If ly an optimization tool, it can also perform grid models are not considered, it shows simulations if there are no degrees of free- that different temperature levels (e.g. low dom (such as investment decisions). Howe- temperature DH) are rarely modelled yet in ver, optimization is only performed by some system analytical approaches (apart from of the considered tools. Investment/design LowEx-CAT). optimization is both modelled in the energy system model TIMES Local and in the Overall evaluation heat grid model Termis. Operation optimi- The evaluation of the analyzed local and zation is performed by EnergyPLAN, KOP- DHC planning tools has shown some pro- TI, LowEx-CAT and Termis. To some degree mising approaches for low temperature TIMES Local also optimizes the operation of DH. For example, LowEx-CAT combines an an energy system, as the operational plan- energy system approach with a heat net- ning is optimized within investment/design work approach to display exergy efficiency. optimization. However, technology detail is limited to five technologies. Demand Categories To conclude, there was no planning tool The demand categories comprise found to be appropriate for the objective households, commercial, industry and of a simplified, integrated tool for low tem- transportation. The analyzed planning tools perature DH to enable analyses and com- focus mainly on two demand categories: parisons of different heat supply options in Households and commercial. Industry is terms of energy, ecology and costs. Based only taken into account by EnergyPLAN, on the evaluation results, a simplified plan- Termis and District ECA (with some limita- ning tool for DH is developed and presen- tions KOPTI and HeatNET that do cover the ted in chapter 6.5. DHC sector, not further specifying if indus- Further evaluation results of existing local try is included). Transportation plays a mi- and DHC models can be found in (Blesl and nor role, as it is only included in one of twel- Stehle 2017). ve planning tools (EnergyPLAN). 6.4 Summarizing Evaluation of DH Final Energy Consumption Planning Tools Final energy consumption is divided into electricity, heat and transport. As planning For the identification of integral and innovati- tools for district heating are assessed, any ve approaches to low temperature heat sup- of the investigated tools focuses on respec- ply at municipal level, an overview of exis- tively includes the heat sector. Electricity is ting approaches is provided here. considered to some degree in any of the se- Initially, a classification form for local and lected energy system models (e.g. although DHC models was developed and distribu- LowEx-CAT considers electricity using back- ted to tool developers. After obtaining the completed classification forms from the 48 Annex TS1 participants, the planning tools tion of an energy system); TIMES Local (in- were assessed in seven categories: analyti- vestment/design optimization of an energy cal approach (energy system model, ther- system); and Termis (operation and invest- modynamic model, other), target group of ment/design optimization of a heat grid). users (municipal authorities, professional As for the demand categories the focus lies planners, R&D), level of detail (geographi- on households and commercial buildings. cal scope, time horizon), model type (simu- Only some tools include the industry sec- lation, optimization), demand categories tor (EnergyPLAN, Termis and District ECA) (households, commercial, industry, trans- and only one does the transportation sector portation), final energy consumption (elec- (EnergyPLAN). tricity, heat, transport) and used variables For an integrated approach of DH energy (costs, energy, exergy, temperature). systems including CHP, the heat and pow- The planning tools were divided according to er sector need to be considered. However, their analytical approach into energy system as planning tools for DH focus on the heat and thermodynamic models. Energy sys- sector, the power sector plays a minor role tem models cover the whole energy supply or is not modeled at all. Transportation is chain from primary energy sources to useful usually not considered. energy. However, they usually do not consi- Even though costs are the essential varia- der the thermodynamics of district heating ble to assess investments (e.g. into new or (e.g. interactions on thermodynamic level of existing grids), an economic approach is processes with requirements of predefined only applied by about half of the selected temperature levels). Thermodynamic mo- planning tools for DH: EnergyPLAN, KOP- dels are thus required. There are also pl- TI, TIMES Local, SIMUL_E.NET, Exergy Pass anning tools that did not fit into the catego- Online, (meanwhile LowEx-CAT) and Termis ries stated above. These were classified as as the only grid model. ‘others’ (e.g. EME Forecast). The integration of renewable energy sources For the target group of municipal authorities into the energy system is another important planning tools, such as District ECA and Ex- aspect of low temperature DH. Both Ener- ergy Pass Online, come into consideration, gyPLAN and LowEx-CAT focus on this as- as they are described as user-friendly and pect. However, EnergyPLAN does not con- do not require trained users, unlike most sider heat grids or urban districts - in cont- other tools do. rast to LowEx-CAT. Regarding the geographical scale, it is not For the evaluation of low temperature DH, only important at which level of detail a pl- the variable temperature is needed. Apart anning tool can be applied for, but also to from the heat grid models only LowEx-CAT know its range of scales. From the analy- is able to include the temperature in simu- zed tools three tools can model all different lations. LowEx-CAT, classified as both an scales from a whole region over city, district energy system and thermodynamic model, and street (neighborhood) to a DHC sup- seems to be a suitable tool for the evalua- plied area (e.g. TIMES Local, Termis, EME tion of low temperature DH. However, the Forecast). Apart from streets, this also ac- level of detail is limited to five technologies counts for KOPTI and HeatNET. and costs were not taken into account (at Another aspects of detail are the modelled the time of the evaluation, but are mean- time horizon and the time resolution. Most while considered). of the considered tools cover a time hori- The building stock as well as the develop- zon of one year and less with an hourly rement of urban districts is not considered by solution. Longer time horizons are modeled most of the selected planning tools. A pro- in TIMES Local (few decades), LowEx-CAT mising approach is followed by District ECA, (less than five years), Termis (more than ten as it includes buildings along with their cha- years) and EME Forecast (up to ten years). racteristics and energy demand as well as Simulation is part of any of the selected pl- the supply at a district level. However, per- anning tools. However, optimization is only forming future scenarios is not possible, as performed by five tools: EnergyPLAN, KOP- well as modeling heat grids or entire ener- TI, LowEx-CAT (all three operation optimiza- gy systems. www.iea-dhc.org 49 To conclude, the evaluation has shown (Germany) in cooperation with Annex some promising approaches for low TS 1 participants. It enables the easy temperature DH. However, there was analysis of districts in terms of energy

none found to be appropriate for the consumption, CO2 emissions and costs objective of a simplified, holistic tool for of different DH supply options. low-ex DH. The development of the simplified tool By evaluating the selected planning EDA involved several steps. Starting tools for DH schemes, requirements with an evaluation of existing planning can be derived for the development of tools for district heating to derive requi- a simplified planning tool. rements for a simplified tool (see chap- A simplified tool should be simplified ter 6.3), the methodical approach for in terms of user-friendliness, but not the EDA-Tool was developed, imple- mandatory in the complexity of calcu- mented into Excel VBA, and applied to lation. Due to the intermittent availabili- a case study. ty of solar energy, the analysis and evaluation of solar integration into heating 6.5.1 Description and Methodical grids along with thermal storage requi- Approach res a high temporal resolution to cover Easy District Analysis (EDA) is a simpli- the use of DH technologies. Aside the fied tool for urban planners and utilities technical consideration, also economic for the energetic, ecological and econo- conditions need to be covered by a sim- mic analysis as well as the evaluation plified tool in high temporal resolution. of districts with regard to low tempera- For example, revenues for cogeneration ture heating to enable comparisons with from electricity feed vary due to hour- other heat supply options. ly changing electricity prices. Thus, for EDA is a simplified tool rather in terms of economic optimization algorithms have the required amount of input data than to be developed to find the optimal use in terms of the complexity of calculation. of technologies depending on econo- This means with little information on a mic conditions. Aside the comparison district energy system that is being ana- of technical and economic operation of lyzed, an annual load profile is genera- DH systems, different temperature le- ted in hourly resolution (taking simulta- vels of standard and low temperature neity of demand into account) to enable DH need to be analyzed with regard to the integration of intermittent renewa- the impact on carbon emissions and ble energy (e.g. solar thermal) into the costs. district heating system and to consider All in all, the simplified tool should ena- storage options. As a simplified tool EDA ble the analysis and evaluation of diffe- addresses mainly to urban planners, it rent DH supply variants (e.g. solar in- is intended to be used in the pre-plan- tegration), temperatures (standard DH ning phase of a district energy system. vs. low temperature), operation modes The approach of EDA for the analysis (technical vs. economic operation) on and evaluation of energy supply options the use of technologies and the related for districts is sketched in Figure 6-2 impact on carbon emissions and costs. . Basically, the tool covers the urban Such a simplified planning tool is pre- energy system from supply side (ener- sented in the next section. gy carriers, technologies) over distribution (heat grid) to demand side (annual 6.5 Easy District Analysis (EDA) – demand). As input the user selects sup- A Simplified Tool ply technologies (e.g. CHP plus peak The EDA tool (Easy District Analysis) is boiler) and energy carriers (e.g. natu- an excel-based simulation tool that has ral gas), grid parameters (e.g. supply been developed by the IER (Institute and return temperature) as well as the of Energy Economics and Rational Use considered district (e.g. 100 multi-fami- of Energy) at the University of Stuttgart ly houses). EDA calculates then a load 50 Figure 6-1 Start tab of the Excel VBA –based tool Easy District Analysis (EDA)

Figure 6-2 Approach for a simplified tool to evaluate energy supply options for districts: Easy District Analysis (EDA) profile (space heat, domestic hot water), op- The structure of the EDA tool can be divided timizes the use of technologies in technical into input that follows the DH supply chain or economic terms and enables the evalua- (supply, distribution, demand) and into out- tion and comparison of different district heat put as the tool results (load curve, use of supply options in terms of primary energy, technologies, evaluation & comparison) (see final energy, CO2 emissions and costs. Figure 6-2 ). www.iea-dhc.org 51 Supply mer side (e.g. thermal storage inside buil- Four different DH supply options can be dings) are not part of EDA. However, dif- compared. The basic option is a DH sys- ferent technologies of heat transfer on the tem of cogeneration with boiler. These tech- demand side, such as low temperature ra- nologies can be compared for technical and diators, can be considered by different ef- economic operation. Furthermore, this ba- ficiencies of the heat distribution inside the sic DH system can be complemented by DH buildings. After the inputs are set, the EDA storage to decouple heat demand tempo- tool provides mainly three outputs: annu- rally from the supply side and to enable the al load curve in hourly resolution, the opti- use of cogeneration depending on electricity mized use of technologies, and the evaluati- prices. To decarbonize DH supply, solar in- on and comparison of different district heat tegration with thermal storage can be taken supply variants. into account, whereby solar thermal energy is supplied by a ground-mounted solar Load Curve collector field. The supply tasks of techno- Based on the annual demand data, a load logies in EDA include both space heat and curve in hourly resolution is generated. As domestic hot water (DHW). demand of multiple consumers shows a cer- For all technologies technical (e.g. efficien- tain degree of simultaneity, a shift algorithm cy), economic (e.g. fuel price, specific costs based on a Gaussian distribution was deve-

per kW) and ecological (e.g. CO2 emissions) loped to consider equalizing effects on the parameters can be set. The design of the load profile (see more on load profiles in CHP plant is calculated on preset full load chapter 6.5.2). hours or on the share of CHP heat on DH supply, and on the load profile of the pre- Use of Technologies sent district. Based on the generated load profile and set input parameters (e.g. full load hours), the Distribution design of the cogeneration plant with boiler For the distribution of the supplied heat, dif- is calculated. The design of other technolo- ferent temperature levels for the supply and gies, such as a ground-mounted solar coll- return line can be chosen, e.g. from stan- ector field and respectively or district heating dard DH (90 °C/60 °C) to low temperature storage, can be preset or based on design DH (50 °C/35 °C), to analyze the impacts criteria (e.g. solar fraction or m³, kWh). The

on resource consumption and CO2 emissi- DH storage can be used as short-term sto- ons. The efficiency of supply technologies rage (e.g. daily storage of CHP heat to pro- is dependent on the chosen supply and re- fit from high electricity prices at the EPEX turn temperature. SPOT (European Power Exchange for power spot trading)) or long-term storage (e.g. Demand seasonal storage of solar energy) depending Space heat and domestic hot water (DHW) on the design of the storage. are taken into account for the analysis of The use of these technology capacities can district heating supply. The calculation of be optimized technically and economically. space heat demand is based on the num- Technical optimization means minimizing ber and net floor area of different building ty- primary energy consumption by maximi- pes (single-family, multi-family houses, non- zing the use of efficient technologies such residential buildings) and associated speci- as CHP. Economic optimization means to fic space heat demands per m² which can run a heat supply system in a cost mini- be differentiated according to construction mal mode by considering the revenues from years. DHW demand is estimated by num- CHP electricity, which depend on changing ber of inhabitants or number of residential electricity prices. units and specific DHW demands per person/unit. There is no distinction for diffe- Evaluation & Comparison rent temperature level requirements of DHW Different DH supply technologies (e.g. and space heat. Technologies on the consu- CHP with peak boiler) and operation mo-

52 Figure 6-3 Input parameters for CHP plant, boiler and the grid can be set in the EDA-Tool des (technical operation, economic opera- tricity feed). As a result technical operation tion) for a given demand can be evaluated leads to minimal carbon emissions and eco- and compared in terms of the use of tech- nomic operation to minimal operation costs. nologies and related primary energy con- In case of economic operation (4) of solar sumption, carbon emissions and costs. As DH with storage, solar energy is given pri- technology parameters can be set by the ority over cogeneration, although marginal user both an existing and new DH system costs of cogeneration might sometimes be can be evaluated. lower (e.g. during high electricity prices). The EDA tool enables the analysis of four Aside the evaluation and comparison of dif- different supply options: ferent DH supply options and operation mo- 1. Technical operation of cogeneration with des in terms of primary energy consump- boiler (TechOp) tion, carbon emissions or heat production 2. Economic operation of cogeneration costs, the effect of solar integration on the with boiler (EconOp) use of DH technologies (e.g. cogeneration, 3. Economic operation complemented by boiler) can also be assessed. DH storage (EconOp+Storage) 4. Economic operation with solar integration and DH storage (EconOp+Storage+Solar) Technical operation (1) and economic operation (2-4) differ in the goal of optimizing the use of technologies: Whereas technical operation involves minimizing primary energy consumption by maximizing the use of efficient technologies (e.g. cogeneration), economic operation means to operate the technologies at marginal costs (which depend on e.g. the revenues from CHP elec- www.iea-dhc.org 53 6.5.2 Load Profile Generator the number of flats (for multi-family houses) is also taken into account (see formulas The methodical approach for the generati- (6-1) - (6-3)): on of load profiles differs for residential and non-residential buildings. In the following (6-1) the generation of load profile for residenti-

al buildings is described (for the descripti- 1

on of load profiles for non-residential buil- 365 dings see (Blesl and Stehle 2017). (6-2)

Residential Buildings 365 The EDA tool distinguishes between two (6-3) types of residential buildings: single-fami- with ly and multi-family houses. As energy de- Q : Space heating demand [kWh] mand of buildings fluctuates depending on Heat QTWW: Domestic hot water demand [kWh] the season of a year (summer, winter, tran- W : Electricity demand [kWh] sition), weather (sunny, cloudy) and consu- Electr FTypical Day: Energy demand factor of a mer pattern (workdays, Sundays) ten diffe- typical day [-] rent typical days are defined as shown in NPers: Number of persons (single-family Table 6-4. house) Typical days represent typical load profiles N : Number of flats (multi-family house) of space heat, domestic hot water and elec- Flat tricity demand of single-family and multi-fa- To arrange these typical days chronologi- mily houses, whereby 15 climate zones in cally within a year, weather data on cloud Germany are differentiated. The energy de- coverage and ambient temperature are used mand (space heat, domestic hot water, elec- from test reference years (TRY) provided tricity) of a typical day is basically calculated by the German Weather Service (DWD). An with the annual demand and with an energy hourly resolution is obtained when the de- demand factor for the typical day, which is mand of a typical day is multiplied by a nor- given by the VDI guideline 4655 (VDI 4655 malized hourly value, which is given by the 2008) for the different buildings types and VDI guideline 4655 depending on climate climate zones in Germany. For domestic region and building type. hot water and electricity demand the num- By means of this information an annual ber of persons (for single-family houses) or load profile is generated in an hourly reso- Table 6-4 Classification of typical days (according to VDI 4655)

Workday [W] Sunday [S] (based on calendar) (based on calendar)

Season Fine [H] Cloudy [B] Fine [H] Cloudy [B] (Average cloud Average cloud (Average cloud (Average cloud amount <5/8) amount >=5/8) amount <5/8) amount >=5/8)

Summer [S] SWX SSX Taverage >15 °C)

Transition [Ü] ÜWH ÜWB ÜSH ÜSB Taverage =5 °C...16 °C

Winter [W] WWH WWB WSH WSB (Taverage <5 °C)

54 lution for one building. As demand of mul- taneity of demand of multiple consumers tiple consumers does not happen in simul- into account. taneity, load profiles cannot be simply added up. Simultaneity factors that consider 6.5.3 Optimization of the Use of Heat the simultaneity of demand for space heat, Supply Technologies domestic hot water and electricity are there- The optimization of the operation of different fore considered. DH technologies can be performed by the 0 … 1 (6-4) EDA tool in two ways: technical and econo- ∑ mic optimization. Technical operation means to maximize the with ∑ use of efficient technologies (such as coge- gf: Simultaneity Factor neration) in order to minimize primary ener- P(t ): Maximum requested performance max gy consumption, although this might invol- within a year ve higher operation costs. P : Performance, if all consumers would C Economic optimization leads to cost-mini- demand the maximum performance mal operation of DH technologies, although simultaneously this might involve higher primary energy consumption and greenhouse gas emissi- As simultaneity factors relate on the maxi- ons. The hourly cost-effective mode of ope- mum requested performance [kW] within ration depends on fuel costs (that are assu- a year (see formula (6-4)), they provide no med to remain unchanged within a year), detail on the hourly distribution of demand varying efficiencies (dependent on supply [kWh] of multiple consumers. Therefore, a temperature levels) and varying revenues shift algorithm was developed to consider from power production. For example, in Ger- equalizing effects on the load profile (see many according to the combined heat and formula (6-5)). Based on a Gaussian proba- power law 2016 (KWKG 2016) electricity fed bility distribution, the demand of one hour into the grid produced by CHP plants grea- is shifted to other hours (from minus twel- ter than 100 kW need to be traded direct- ve to plus twelve) assuming that a shift of el ly (e.g. on the power exchange EPEX SPOT few hours is more likely than a shift of seve- (European Power Exchange for power spot ral hours. The variance of the Gaussian dis- trading)). Therefore, operation costs of co- tribution was derived from the simultaneity generation depend on the varying electrici- factor, depending on the number and kind of ty prices. Moreover, cogeneration electricity consumers. The shift algorithm can be seen receives financial support, unless the elec- in formula (6-5), whereby gf is a weighting h tricity prices are negative. For negative elec- factor for the load shift from minus twelve to tricity prices (e.g. during periods of high re- plus twelve hours (see formula (6-5). newable power generation), the operation of

(6-5) a CHP unit can become less economic than the single operation of a boiler (see Figure 6-4). This might be more often the case in The weighting factor gf can be described h the future, as negative electricity prices at as follows: the European Power Exchange (EPEX) are (6-6) expected to become more frequent. A flow chart inFigure 6-5 describes the de- with √ cisions that the EDA tool has to undergo in N : Number of single-family SFH,MFH,NRB order to identify the cost minimum operati- houses, multi-family houses, on of a DH system (CHP and boiler). Three non-residential buildings decisions are made along the program se- h: Shift in hours quence: Electricity price negative or not σ2: Variance (green), heat load higher than thermal output of the CHP unit or not (blue) and costs As a result an annual load profile for diffe- of CHP and peak boiler greater than costs rent kinds of demands and buildings is ge- of boiler only or not (orange). nerated in hourly resolution taking simul- www.iea-dhc.org 55 Figure 6-4 Economic operation – use of technologies depending on the occurrence of negative electricity prices (green line, right axis) For negative electricity prices the operati- 6.5.4 Application of EDA in a Case Study on costs of the CHP plant are higher than In the present case study a district heating the boiler operation costs. Thus, the boiler (DH) system of a cogeneration plant and only supplies heat to the grid. If the elec- a boiler is considered to supply about 140 tricity price is not negative, the next bran- multi-family houses based on the data de- ch asks if the heat load of the grid is grea- scription of (Pietruschka et al. 2016). Two ter than the maximum thermal output of the aspects are analyzed: grid temperatures CHP unit. If not, the CHP unit is not ope- (standard DH vs. low temperature DH) and rated under full load, which influences the the operation mode (technical vs. economic cost calculation. This involves e.g. revenu- operation) of a DH system. es from CHP bonus, grid usage costs, ener- The aim is to find out what impact has a de- gy tax and fuel price. If the operation costs crease of grid temperatures and the opera- of a “CHP+Boiler” system are greater than tion mode on carbon emissions, the use of the “Boiler only” system, the heat supply is technologies and costs of the DH system. then only operated by the boiler.

Figure 6-5 Flow chart in case of economic optimization 56 The motivation for low temperature DH is TechOp vs. EconOp that a reduction of temperatures compa- A comparison of relative CO2 emissions bet- red to standard DH involves higher effici- ween standard DH (left) and low tempera- encies along the district energy system re- ture DH (right) is shown in Figure 6-6. The sulting in falling primary energy consumpti- reference for this calculation is the case of on and carbon emissions. Low temperature standard DH in technical operation mode. can be used, because high temperature le- Carbon emissions are allocated according to vels are often not required for the supply of the exergy method (left column) and to the space heating and domestic hot water. For power bonus method (right column). instance, radiators only need temperatures Technical operation (TechOp) and economic between 55 °C and 90 °C, panel heating operation (EconOp) play a different role in between 35 °C and 45 °C and floor heating carbon emissions. Due to the economic si- systems between 25 °C and 35 °C. Moreo- tuation (e.g. declining electricity baseload ver, low temperature DH allows the easy in- prices for electricity feed from cogeneration) tegration of renewable energy and opens up the CO2 reduction potential of DH is not ex- new potentials of low energy supply (such ploited to the possible extent. However, the as solar thermal and geothermal energy or economic operation mode can perform bet- waste energy). ter in carbon emissions if grid temperatures For the present case study of an urban dis- are decreased. Compared to technical ope- trict of 140 multi-family houses two scena- ration of standard DH, low temperature DH rios are analyzed in the following: in economic operation can even save up to

1. It is distinguished between technical 13 % of CO2 emissions. Thus, low tempe- (TechOp) and economic operation (Eco- rature DH can contribute to climate protec- nOp) of DH to analyze the impact of eco- tion even under economic conditions. The nomic conditions on carbon emissions. comparison also shows for TechOp a possi- 2. The impact of solar integration on the ble carbon reduction potential of low tem- use of DH technologies, carbon emissi- perature DH of up to 15 % for the present ons and costs (EconOp+Storage+Solar) case study. is analyzed compared to (TechOp). These values apply to operation optimizati- Furthermore, for both scenarios a distinction on under consideration of the German CHP is made between standard DH and low tem- bonus. However, as the German CHP bonus perature DH. They are both operated with is limited to 30,000 full load hours, it can flexible supply temperatures that depend on be expected that carbon emissions of eco- the ambient temperature: nomic operation will then rise significantly. • Standard DH: supply from 90 °C to 70 °C / return from 60 °C to 55 °C TechOp vs. EconOp+Storage+Solar • Low temperature DH: supply from 60 °C The independency of DH supply from the to 50 °C / return from 45 °C to 35 °C used energy source enables the use of cli- The operation optimization of the use of tech- mate-friendly technologies, such as solar nologies is performed for German baseload thermal energy. The integration of solar ther- electricity prices in 2015 and for the Ger- mal energy into the DH system causes feed- man CHP bonus (KWKG 2016). Although back on the use of the DH supply technolo- full-costs analysis takes temporal develop- gies. Two DH systems are compared in the ment of prices (e.g. the expiration of CHP following: cogeneration plant with boiler in bonus after 30,000 full load hours) into ac- technical operation (TechOp) and cogene- count, the operation optimization is limited ration plant with boiler along with solar in- to the economic conditions of the year 2015 tegration and thermal storage in economic (German CHP bonus, German electricity ba- operation (EconOp+Storage+Solar). The co- seload prices, etc.). generation plant is designed on 5,000 full A listing of all assumptions and inputs as load hours for the case of technical operati- well as further scenarios can be found in on. The collector surface is set at 10,000 m² (Blesl and Stehle 2017). (corresponds to solar fraction of round 30 % in case of standard DH). For the design of www.iea-dhc.org 57 Figure 6-6 CO2 emissions for standard DH (left) and low temperature DH (right) compared to standard DH for technical operation (consideration of CHP bonus) depending on the allocation method. the DH storage 3.5 m³ per m² solar collec- 9 % of carbon emissions compared to tech- tor are assumed resulting in a total capaci- nical operation. ty of 35,000 m³. Still the capacity might not Compared to standard DH, decarbonizati- be enough to store all of the provided solar on involves fewer costs (+ 26 % instead of energy (e.g. for standard DH: about 9 % of + 38 %) with low temperature DH. The re- solar energy cannot be used; low tempera- duction of carbon emissions is standing out ture DH: 26 %). with round 30 % compared to round 10 % Figure 6-7 shows the impact of solar integ- of solar integration for standard DH. Due to ration on the use of the cogeneration plant. lower temperatures solar yield from the coll- In case of standard DH the share of coge- ector field is increased by 45 % from 370 neration on DH supply drops from 66 % to kWh/m² (standard DH) to about 540 kWh/ 40 % respectively the full load hours decli- m² (low temperature DH). This is not only ne from 5,000 to 3,000. For low tempera- explained by lower collector heat losses, but ture DH the declines are even higher: the also by an increasing period of solar thermal full load hours are nearly halving from 5,000 feed (+ 32 % hours of solar feed) as lower to 2,600. However, the share of solar energy grid supply temperatures are easier achie- increases to 35 % for low temperature DH ved. Moreover, low temperature DH increa- instead of 27 % for standard DH. To decoup- ses the solar fraction of DH supply. Due to le demand and solar availability, most of so- higher efficiencies of solar collectors, sto- lar energy is stored in the seasonal storage. rage capacities in m³ need to be designed The effect of the shift in the use of techno- larger per m² collector surface or vice ver- logies on carbon emissions and costs of DH sa, for a given storage capacity less collec- needs to be analyzed. A lower usage of coge- tor surface is required. Thus, above presen- neration results in fewer revenues from elec- ted cost benefits would be higher, if the de- tricity feed. On the other hand, fuel costs are sign of the collector field would be adjusted decreased as solar radiation is free of char- to reduce solar excess heat (that cannot be ge. As solar energy mostly replaces coge- further stored). neration, carbon savings are not as high as In conclusion, the case study has shown

expected. In reality, CO2 savings are higher that low temperature DH can be a key ap- as boilers are not only used for peak load, proach to decarbonize DH supply. The trend but also for low loads in summer. for rising carbon emissions of CHP DH sup- The quantitative effects of solar integration ply (due to economic conditions) can be into the DH system for the present case stu- countered by low temperature DH even in

dy are shown in Figure 6-8. In case of stan- economic operation, as less CO2 emissions dard DH solar integration with storage invol- are released compared to standard DH in

ves higher costs (+ 38 %), but saves up to technical, CO2-optimal operation (in case of 58 Figure 6-7 Use of technologies for DH supply in case of standard DH (left) and low temperature DH (right) and number of full load hours of the cogeneration plant (dashed line)

Figure 6-8 CO2 emissions (green) and costs (red) for standard DH (left) and low temperature DH (right) compared to standard DH for technical operation CHP bonus). Furthermore, low temperature lies on the evaluation of the impact of diffe- DH with solar integration does not only in- rent grid temperatures (e.g. standard DH vs. crease carbon savings (e.g. due to increa- low temperature DH) and of different ope- sed solar yield and solar fraction), but also ration modes (technical vs. economic ope- decreases costs of solar DH compared to ration) on the use of DH technologies, pri- standard DH. However, solar DH still invol- mary energy consumption, carbon emissi- ves - despite free of charge solar energy - ons and heat production costs. additional costs compared to TechOp for the To enable the easy district analysis, a load present case study. curve of space heat and domestic hot water is generated. The design of the cogene- 6.5.5 Conclusion and Outlook ration plant and boiler is based on the load curve and preset full load hours. Solar coll- The Easy District Analysis (EDA) tool was de- ector surface can be designed on e.g. so- veloped on the basis of requirements for a lar fraction. After the capacities of technolo- simplified DH planning tool that were deri- gies are calculated, the use of different DH ved from a survey on local and DHC models. supply options can be compared in terms The target groups of EDA are urban plan- of technical and economic operation. Tech- ners and utilities, and it is intended to be nical operation leads to minimum carbon used in the pre-planning phase of a district emissions, whereas economic operation energy system. The focus of the EDA tool www.iea-dhc.org 59 means the hourly cost-effective operation ting and building standard situation along of DH technologies based on fuel costs and with costs for change of energy carrier could varying revenues from electricity feed. Eco- be considered. Going beyond the simplified nomic conditions, such as the development consideration of technologies in terms of an- of the electricity baseload price, hinder the nuities, competing DH and non-DH techno- realization of the carbon mitigation potential logies could be compared from the actor’s of CHP DH supply to its full extent. perspective. On the one hand, the invest- A case study applied to a district with 140 ment decisions need to be disaggregated multi-family houses has shown that low tem- to different actors (instead of one aggrega- perature DH can play a key role in the decar- ted homo oeconomicus actor). On the other bonization of DH supply. On the one hand, hand, preferences of actors for attributes the trend of rising carbon emissions in CHP of technologies could be considered with DH supply due to economic conditions can a multi-attribute utility analysis approach. be countered by low temperature DH (with Based on technical and socio-economic cri- CHP bonus). With higher efficiencies for low teria, districts could then be analyzed on temperature DH, carbon emissions are up their suitability to be changed to low tem- to 13 % fewer for economic operation com- perature DH. Thus, a comprehensive compared to standard DH in technical operation parison could be drawn between districts (with CHP bonus). On the other hand, com- to identify qualified districts to start with the pared to standard DH, low temperature DH transformation to low temperature DH. Mo- can boost solar DH in terms of yield and so- reover, actor-specific measures could be lar fraction significantly and thus, increase identified to support the implementation of the carbon mitigation potential of solar-po- low temperature DH. wered DH. Moreover, heat production costs are reduced considerably by low temperature DH compared to standard DH. The future development of the EDA tool can cover several aspects. Although EDA performs a full-cost analysis over a chosen time horizon, operation optimization of the use of DH technologies is limited to the conditions of the base year so far (e.g. electricity prices, CHP bonus). Thus, the temporal development of economic parameters could be also included for the operation optimization (e.g. to evaluate the shift of the use of technologies, after the end of 30,000 full load hours with CHP bonus or to evaluate future falling electricity baseload prices). The EDA tool could also be extended by further renewable technologies (e.g. geothermal energy, industrial waste heat) and power-to-heat technologies (e.g. heating element, heat pump), in order to find out how these multiple energy sources can be combined to best use their potentials within the context of technical, economic and ecological aspects. Mo- reover, issues on self-consumption vs. feed of cogeneration electricity of a district could also be taken into account. Aside DH, district cooling (DC) could be implemented in the EDA tool to consider cooling demand. To identify suitable districts for the realization of low temperature DH, the initial hea- 60 7 APPLICATION OF LOW TEMPERATURE DISTRICT HEATING TO COMMUNITY CASE STUDIES

7.1 Introduction view of the studied system, technical description of the technologies used and the The main topics for the description of case main results and outcome. In addition, studies in this chapter are the identification, many also include information of the rela- demonstration and collection of innovative ted project and the involved stakeholders, community level energy concepts. Advan- measurement data monitoring and utilizati- ced technologies and the interaction bet- on as well as methods used. ween components within a system are demonstrated. Based on the evaluation of the th 7.2.1 Low temperature energy efficient collected examples of 4 generation dis- district heating in Slough (UK) trict heating (4GDH), the tools developed (see chapter 6) and the implementation of The Greenwatt Way scheme and Slough combined dynamic analyses of DH techno- (United Kingdom) is a research project ai- logies (chapter 4) and other relevant factors ming to understand the actual consumption for the market implementation (chapter 5) of heat and electricity usage within an ener- show the potential of the approach for dis- gy efficient environment. The development trict heating systems. Within this chapter al- comprises of a mixture of two and three bed- ready realised low temperature community room family homes and one-bedroom flats. energy system concepts as well as planned The houses, compliant with the Code 6 of or designed systems are identified and pre- the Code for Sustainable Homes - CSH (The sented. Based on the experiences, design Code for Sustainable Homes is the UK na- guidelines are derived. Also, validation of the tional standard for the sustainable design models and tools developed within the An- and construction of new homes. A star sys- nex (chapter 6) using measured data from tem, 1 to 6 stars, is used to rate the perfor- these community projects is carried out. mance of a new homes in terms of ener- Main work items in the project are: gy efficiency as well as choice of materials, • Application of advanced system con- water conservation and ecology), are pro- cepts including solutions for the dis- vided with heat from a range of renewable tribution, local generation and energy heat technologies via a mini District Heating storage (DH) system whilst integrated solar photo- • Use of innovative control concepts voltaics (PV) tiles on the roof provide rene- and strategies for a demand controlled wable electricity. Figure 7-1 illustrates the supply included neighbourhood. • Collection of realised community projects The development consists of two 1-bedroom • Validation procedure of community de- flats, a terrace of three 2-bedroom houses, a sign and planning tools. terrace of three 3-bedroom houses and two The report describes eight demonstration 3-bedroom detached houses with an over- activities in total within Europe, each repor- all heated area of 845 m². ted within a single sub-chapter. The case Each home is fitted with one substation with examples are from United Kingdom (UK), direct connection for space heating and an Germany, Finland, Denmark and Norway. instantaneous heat exchanger for DHW. Lo- More details about the cases can be found cated in the living space of each home, one in the full case studies report (Rämä and radiator supplies heat together with and a Sipilä 2016). towel rail in the bathroom. Radiators are designed for temperatures of 55/35 °C. The 7.2 Innovative community case studies homes also feature a Mechanical Ventilati- on Heat Recovery System (MVHR) that al- For the description of cases each of the follows reaching the Heat Loss Parameter of lowing sub-chapter includes a general over- 0.8 W/m²K required by CSH. The heat re- www.iea-dhc.org 61 Figure 7-1 Visualization of the included neighborhood Greenwatt Way. covery system is supplied by the radiator pumps, the air source heat pumps and the circuit and allows further cooling of return biomass boiler can work independently and temperature. This setup with radiators con- each of them is able to meet the full heating nected in series with heat exchangers of demand of the development. the ventilation system was effective at brin- The thermal storage allows the plant to run ging the district heating return temperature with greater flexibility and efficiency e.g by down. allowing the solar thermal to charge the sto- The scheme is designed to operate at a con- rage when the solar irradiation is high. The stant temperature of 55 °C; domestic hot stratifying thermal storage features multiple water is supplied at 43 °C via the instanta- connections to allow staged heating by heat neous heat exchangers. The energy centre pumps i.e. water first heated up to 45 °C includes the following energy sources: by the first heat pump cycle and then up to • 20 m² of solar thermal panels 55 °C by the second heat pump cycle. The • 2 x 17 kW ground source heat pump mini district heating network is built with a each with 7 boreholes mixture of Logstor steel pipes and Aluflex • 2 x 20 kW air source heat pump pre-insulated twin pipes. The main pipeline • 30 kW biomass boiler is 98 m long with diameters ranging from • 8000 l thermal storage 50 mm to 32 mm. Connection pipes are Each technology, solar thermal excluded, 67 m in length with a diameter of 25 mm has been sized to meet the overall requi- (twin steel pipes for flats and information rement of the site. The ground source heat centre) and 26 mm (twin Aluflex pipes for houses). The network layout is visualised in Figure 7-2. The annual heat consumption of the dwellings is 35.7 MWh. The heat supplied by the energy centre amounts to 49.6 MWh/ year, indicating heat losses of 28 %. The demonstration was implemented between December 2009 (construction was started) and September 2010 (development occup- ied). The monitoring period was a year from 4/2011.

Figure 7-2 Layout of the district heating network. 62 Table 7-1 Summary table for the main indicators for 7.2.2 Energy efficient district heating Greenwatt Way system. network in Ludwigsburg (Germany) Overall length of the pipe- The German Renewable Energies Heat Act line trench 165 m (EEWärmeG) states that the share of rene- Heat consumption 35.7 MWh/year wable energy in heat generation in Germa- ny is to be increased to 14 % by 2020. The expansion of district heating systems is seen Heat delivered from ener- 49.6 MWh/year gy centre as an important element in achieving this goal. District heating enables easy integrati- Average heat losses 28 % on of renewable energy sources and results in higher efficiencies in energy conversion. Linear heat density 0.319 MWh/m The use of combined heat and power in heating grids is an additional option. Howe- Average temperatures (sup- ver, existing district heating networks are of- ply and return) during the 51.7/31.7 °C heating season ten not sufficiently optimised. Systems suf- fer from high heat losses, high return tem- Average temperatures (supply and return) outside the 50.5/38.5 °C peratures and high electrical consumption heating season in pumping. Deviations between predicted and measured temperatures, pressures and mass flows are very common. Reasonable Main activities within the project were: planning and operation of the systems can • Post occupancy evaluation potentially increase their energy efficiency. • Modelling and monitoring of the energy The economics involved drive many heating performance of the energy centre, dis- system operators to be hesitant over com- trict heating and domestic heat and po- bining renewable options with existing cen- wer demand tralised heat production. • Evaluation of the MVHR Decentralised heat supply for small or isola- • Monitoring of PV generation ted areas or so-called micro-grids in many • Monitoring of water usage cases are preferable to an uneconomical ex- • Evaluation of hot fill washing machine pansion of existing district heating networks. and dishwasher In these systems, decentralised solar hea- Lead organisation, the developer and the ting can help saving costs during summer owner for the system was SSE, the research periods when energy demands are very low partners being National House Building (only DHW) (see also 7.2.4). So it may be Council (NHBC), Building Research Estab- more cost efficient to utilise decentralised lishment (BRE) and University of Reading. heat supply than to operate centralised heat The total budget for the demo was £3.65 generation in partial load. million. The demonstration system received The main objectives of the project are to de- support in the form of feed-in tariff for the velop a simulation environment for efficient large PV arrays on each house, but no sup- integration of decentralised renewable heat port for the heating system itself. sources in existing or planned heating grids. The main deliverables for the project were: Applicable results are to be implemented on • Evaluation of energy consumption in ne- a real heating network in the Sonnenberg arly zero carbon houses district of Ludwigsburg. • Evaluation of users interaction with ne- Sonnenberg has a new district heating grid arly zero carbon house systems supplied by a gas CHP plant combined with • Demonstration of construction tech- a geothermal heat pump. Both are located niques deployed to build nearly zero in an old heating plant now refurbished and carbon houses reopened. The municipal energy supplier, Stadtwerke Ludwigsburg-Kornwestheim GmbH, installed and will operate the planned new district heating. All purchase con- tracts for the Sonnenberg building sites in- www.iea-dhc.org 63 clude a clause making the connection to the The main results of the project are: district heating network compulsory. • Development of a substation for active

The gas CHP unit has a capacity of 350 KWth consumers allowing bidirectional heat and the geothermal heat pump a capaci- transfer to and from the district heating

ty of 200 KWth. The buildings are equipped network with a substation and decentralised heat sto- • Testing facilities for validation of nume- rage tanks. rical simulation models Also, smart metering with a centralised con- • Simulation based optimisation of net- trol unit is installed in the buildings. The new work control distribution system’s design includes an op- • Creation and validation of an overall net- tional low exergy expansion with tempera- work model of city quarter Sonnenberg ture levels (40/25 °C). The design tempera- Including numerical models for heat ge- tures of the main network are 70/40 °C and neration units, distribution network and thus, significantly higher. detailed consumer models 30 % of the new Sonnenberg district, supplied by the LowEx subnet (blue area) is pl- 7.2.3 Residential area with geothermal anned in to achieve the low energy or pas- heating & cooling in Wüstenrot sive house standard. Thus, the planned grid (Germany) extension can be operated by the return line A strategy for making Wüstenrot (Germany) of the existing grid. The layout of the distri- a plus energy community by 2020 was de- bution network is presented in Figure 7-3. veloped within the EnVisaGe project. This The project focuses on heat demand evalu- means that the community’s yearly energy ation by studying the operation of the grid. production would be more than the actual Special attention is paid to the management energy consumed within the community. As of heat supply and storage tanks’ charging one important step towards that goal, a plus strategies. Detailed grid simulations help to energy residential district with 24 mostly sin- optimise system operation. gle-family houses was built. Stuttgart University of Applied Sciences To achieve the plus energy standard for all (HFT Stuttgart/Germany) acted as the pro- buildings, a high energy standard - almost ject lead while the implementation was car- passive house standard - was demanded by ried out by Stadtwerke Ludwigsburg-Korn- regulation. All buildings are equipped with westheim GmbH, which also owns the sys- large PV systems. The heating energy of the tem. The demonstration project was started buildings is delivered by decentralised heat on 1st January 2012 and was concluded on pumps. The heat pumps are connected to a 31st August 2014. central geothermal system. Thus, they can achieve a high coefficient of performance. This system consists of a cold water district heating network, delivering low temperature heat to the heat pumps. The novel agro- thermal collector is used as a low temperature heat source for the network. The concept of the system is to activate agricultural fields as geothermal collectors. This is done by deep ploughing the tubes 2 m below the ground surface, interspaced at a distance of 1 m. The process is pictured in Figure 7-4. The agro-thermal collectors can also be used for direct cooling of the buildings du- Figure 7-3 Overview of the existing and planned district heating network in ring summertime. This is in addition to using Ludwigsburg the cold water network for heating during the winter period. Furthermore, the system offers the possibility to combine heat sinks (heat pumps) and

64 Figure 7-4 Thermal activation of the agricultural field in Wüstenrot © HFT Stuttgart heat sources (e.g. re-cooling of compressi- • Development and testing of intelligent on chillers) for highly efficient energy use. load and storage management to incre- In the demonstration system, this combined ase own-consumption of PV electricity utilisation is being demonstrated and ana- • Offer electricity sinks to the municipality’s lysed by integrating the re-cooling of a su- distribution grid by connecting the virtu- permarket cooling device. This supermar- al power plant ket is located near the plus energy district. • Development and implementation of an A special technology for this is being deve- innovative and secure cloud based solu- loped by the company Doppelacker, which tion for data collection and transfer is based in Berlin, Germany. • Development of an intelligent load ma- The overall objectives of the project were to: nagement system Demonstrate the efficiency and economic The objectives were met by following viability of cold water heating/cooling grids deliverables: with agro-thermal collectors • System installation of the agro-thermal • Show the efficiency of the connected collector decentralised heat pumps and of direct • Connection of 16 buildings to the cold cooling applications in the buildings water heating grid • Demonstrate the combined perfor- • Monitoring data of at least 6-8 buildings mance of the system with heat sinks for one year (in progress) (heat pumps) and heat sources con- • Monitoring data of the agro-thermal coll- nected (re-cooling of the super market ector fields and cold heating grid (in cooling device) progress)

Figure 7-5 Connections between buildings and the energy system in Wüstenrot www.iea-dhc.org 65 • Simulation model for the agro-thermal collector (to be further validated during the monitoring phase) • Development and implementation of an intelligent load and storage management. The project duration is from July 2012 to June 2017. A project extension for monitoring is planned for a runtime of 3 more years, which will be followed by a long-term monitoring phase.

7.2.4 Geo-solar local heat supply for residential area in Kassel (Germany) Figure 7-6 Preliminary urban planning concept for the new housing estate ”Zum Feld- The case system area „Zum Feldlager“ is lager” © Architektur+Städtebau Bankert, located in Kassel in the center of Germany. Linker & Hupfeld Currently the area is undeveloped land on ture district heating and domestic hot wa- which a new housing development is plan- ter supply. ned. The area is surrounded by existing buil- The new housing estate will be characte- dings and there is a water protection area rized by a very compact construction and nearby. The new housing estate “Zum Feld- south oriented buildings; 1-2 storey de- lager” is located in an urban ventilation path. tached and semi-detached houses in the For that reason, combustion of oil or wood north, two-storey terraced houses in the (with possible fine particles) should be avo- centre and large three-storey apartment ided. Due to the location of the area, a con- buildings in the south. All buildings have nection to the existing district heating net- specific heat demand of 45 kWh/m²·a and a work of Kassel is not feasible because of lo- specific domestic hot water (DHW) demand gistical and economic reasons. As a result, of 730 kWh/person·a. Thus, the demand is a local district heating concept is implemen- significantly below the maximum energy de- ted. The concept involves the use of rene- mand for new buildings (<50 kWh/m²·a for wable energy sources (RES) such as geo- heating) according to the current valid Ger- thermal and solar energy for low tempera- man energy saving ordinance EnEV 2014 (EnEV 2014). Table 7-2 Assumptions for the buildings and climatic boundary conditions according to the first planning The system consists of a centralized heat pump powered by borehole heat exchangers Total number of buildings 127 (BHE) installed in a geothermal probe field. Depending on the supply variant, the soil Single-family houses (SFH) 46 acts as source in winter or as thermal sto- Semi-detached houses (SDH) 32 rage in summer time. For the regeneration of the soil unglazed solar collectors (swimming Terraced houses (TH) 37 pool absorbers as the low-cost option) are intended. The district heating grid is fed by Multi-family houses (MFH) 12 the centralized heat pump. It is conceivab- Dwelling units 154 le to use the district heating during heating period for provide (low temperature) heat. Persons per dwelling unit 4 The centralized ground coupled heat pump Climatic conditions 2010 feeds the district grid at a temperature level of about 40 °C. The heat for space heating is Orientation of buildings south supplied directly by the district heating net- SFH, SDH and TH = gable roof, work through the use of heat exchangers. Roof shape MFH = flat roof For preparation of domestic hot water different variants are possible and foreseen. In Heat emission system surface heating case of separated domestic hot water pre- 66 De-central units (DH service station, solar thermal systems)

Heating Grid 40 °C

Gas Grid Central Heat Pump Electricity Grid Solar system

Domestic hot water Floor heating

Ground regeneration Heat storage Sub station Ground Heat Exchanger / Boreholes

District heating

Figure 7-7 Arrangement and schema of the solar-ground storage systems © Fraunhofer IWES paration thermal solar panels (e.g. flat-pla- • Development of industrial management te collectors) or an electric heating element and control strategies of district heating could be used. The solar panels could be system (winter and summer case) installed on the roof or on carports. Ano- • Dimensioning of components ther variant for domestic hot water prepa- • Measurement and evaluation concept ration is usage the heat of the district heating grid, also in combination of solar panels 7.2.5 Future district heating solution for and heating elements. The required tempe- residential district in Hyvinkää ratures lift is significantly lower. (Finland) The advantages of this supply variant are District heating has been an integral part slightly higher heat losses. Furthermore, of the Finnish energy system for decades. space heat could be directly used from grid Its development started in 1950’s and cur- (substation required). No decentralized heat rently sits on a market share of 48 % within pumps must be installed and thus the in- the heating sector. In the major cities, the vestments costs are lower. market share is over 90 %. Finnish district The research effort in the project was car- heating systems are characterised by high ried out by Fraunhofer IBP/IWES and Uni- efficiencies and high share of CHP based versity of Kassel (Department of Geotechni- production (up to 75 %) in heat supply. In cal Engineering & Department of Solar and terms of distribution, the insulations stan- System Engineering). The owner of the de- dards used in Finnish district heating pipes monstration system was City of Kassel and are high compared to most other developed the operator was the utility company Städ- district heating countries (Heikkinen et al. tische Werke AG in Kassel. German District 2014 and Klobut et al. 2014). Heating Working Group (AGFW) was also in- The district heating system in Hyvinkää buil- volved in the project. The project started in ding fair area (Figure 7-8) is used a case stu- 11/2015 and is to be concluded in 8/2017. dy for low temperature district heating and In late 2016, the decision has been made for incorporating solar heating into buildings not to realize the project approach as de- within a district heating area. Another point scribed here because of time constraints. of view was to highlight the significance of The total investment costs were estimated planning by showing the effects lower than to be 3.7 million EUR (demonstration) and predicted connection rate. Currently, at the 1.0 million EUR (research, measurements). time of the study the connection rate within The main activities for the project were: the area was 47 %. Other dwellings have • Soil reconnaissance chosen different heating solutions; boilers, • Development of thermal simulation mo- collectors, heat pumps or a combination of del of entire housing estate www.iea-dhc.org 67 these. Most of the buildings have underf- con nection rate) and planned (100 %) sys- loor heating for internal heat distribution, tem layout are presented in Figure 7-9. but some have radiators or ventilation based Modelling of heat demand was carried out heating systems. using IDA Indoor Climate and Energy simulation tool (space heating) and Apros Pro- cess Simulation Software (domestic hot water). The existing 47 % connection rate case had a heat demand (including heat losses) of 630 MWh and a linear heat density of 0.4 MWh/m (consumption per trench length). The planned system (100 % connection rate) had 1,371 MWh of heat demand and a linear heat density of 0.74 MWh/m. In parallel with the simulation work, life cycle costs (LCC) analysis was carried out. Ac- cording to results, the district heating solution in a single family passive house, com- plying with the 2020’s energy efficiency requirements, is a little more competitive Figure 7-8 Overview of the Hyvinkää building fair area compared to the solution using ground heat © Arkkitehtitoimisto Turtiainen Oy pump. Life cycle assessment (LCA) showed that the carbon footprint of a small district heated house can be reduced by building more energy-efficient house than current standards require. Additionally, approx. 50 % of greenhouse gas emissions can be avoided during the life cycle of 25 years, by increasing the share of renewable fuels in the district heat production. Utilisation of heating and electricity generated from municipal waste will reduce the building‘s carbon footprint. The study was part of a larger project called Figure 7-9 Network structure for 47 % connection rate (left) and 100 % “Future district heating solutions for resi- connection rate systems. dential districts” (Klobut at. al. 2014) with following objectives: The studied area is part of the larger Hy- • To develop adequate district heating so- vinkää district heating system (Rämä et. al. lutions for residential low energy districts 2014). The connection to the main system • To compare alternative solutions by life- is implemented using heat exchangers. As cycle assessment (cost and emissions) a result, the distribution temperatures in • To evaluate the potential of utilising mu- the area are lower than in the main system; nicipal and construction waste for dis- constant supply temperatures of 85 °C and trict heating energy generation 75 °C are used during winter and summer • To investigate how nearly zero-energy time, respectively. As an additional simulati- buildings (in terms of the Energy Perfor- on effort, the operation with a constant sup- mance of Buildings Directive) affect the ply temperature of 65 °C was studied as well. dynamics of local DH-network The distribution network in the area has a The lead organisation of the project was utili- total length of 1,223 m or 1,675 m for 47 % ty Hyvinkään Lämpövoima (owner of the dis- and 100 % connection rate cases. It con- trict heating network) and the other partici- sists of pipes in sizes from DN40 to DN200 pating and funding organisations were Fin- with service pipes being either DN15 or nish Funding Agency for Technology and In- DN32 depending on the consumer. The net- novation, City of Hyvinkää and Finnish Ener- work structures for both the existing (47 % gy as well as energy utilities Ekokem Ltd, Jy- 68 väskylän Energia, Helsingin Energia, Por- voon Energia and Riihimäen Kaukolämpö. VTT Technical Research Centre of Finland was responsible for the research carried out in the project. Demonstration site was owned by the Hyvinkään Lämpövoima. The project started in 10/2011 and was concluded in 12/2013.

7.2.6 Low-temperature district heating in Sønderby (Denmark) The project is a full scale demonstration in Sønderby, Taastrup, in Denmark (Figure 7-10). The heated area includes 75 single family houses built from 1997-1998 with under floor heating systems. The demonstration aims to show that low temperature district heating (LTDH) works in existing buildings and identify solutions to minimise the Figure 7-10 Full scale demonstration of low-temperature district heating, high heat losses. Sønderby, Denmark. (Energistyrelsen 2014) In the project, the old district heating (DH) ficient plastic DH pipes. Branch pipes are system was replaced with new DH pipes and AluFlex flexible pipe with insulation class se- consumer substations. Through renovation, ries 3. The larger pipes are insulation class the temperature in the network is reduced series 2. The area is supplied from adjacent from average 80 °C to average 55 °C. The medium temperature DH network. Low tem- demonstration project shows that there is a perature is achieved with a mixing shunt and great energy saving potential by providing a booster pump. All 75 houses are replaced LTDH for existing buildings with underfloor with new instantaneous heat exchangers. heating as space heating system. The heat exchanger is specially designed The demonstration area includes 75 sing- for the low temperature difference and the le family houses built from 1997-98 with li- high flow on the primary side, which is ob- ving space ranging from 110 to 212 m², ty- tained by low-temperature operation with pically 2-5 people in each house. The hou- a flow temperature down to 50 °C. All 75 ses have floor heating in all rooms which houses are equipped with remote reading of make it possible for LTDH supply. The hea- power meters (Kamstrup MULTICAL® 601 ting degree day is 2,977. with top module). The supply temperature to The annual heat consumption in the buil- the low temperature network has averaged dings is in the range of 5 to 23 MWh/year 55 °C. The return temperature has annu- per house (not include heat loss in the grid). ally been about 40 °C, resulting in an over- Average consumption is about 13 MWh all cooling of about 15 °C. (based on consumption during the heating The main design parameters are: seasons 2004/2005 - 2009/2010). The hou- • Network maximum level of pressure: ses originally had hot water tanks for dome- 10 bar stic hot water (DHW) supply (110 l or 150 l). • Maximum velocity in pipes: 2.0 m/s Before the project, the network supply tem- • Peak load design outdoor temperature perature varied between 65-107 °C, with the -12 °C lowest supply temperature in summer. The • Thermostatic bypass set point 50 °C average supply temperature is 80 °C. The • Heat loss coefficient (U-value) based on annual grid heat losses accounted for 38- the supply/return temperature 55/25 °C 44 % (average ≈ 41 %) of the heat supplied and ground temperature 8 °C. from the central heat exchanger. • Minimum differential pressure: 0.3 bar Through the project, high efficient twin DH • Taastrup DH plant supply pressure pipes are installed to replace old very inef- 3.4 bar www.iea-dhc.org 69 • Taastrup DH plant return pressure The full-scale demonstration project inclu- 2.6 bar ded a new supply concept. The low-tempe- • Comparing with old DH system, the new rature network is supplied with return water DH system has the following features: from the medium temperature network from • Low network supply/return temperature the neighbouring Taastrup DH. This supply • Energy efficient and smaller dimensi- temperature is averaged at 48 °C and the on DH pipes supplied energy covers about 80 % of the • Mixing shunt and booster pump for low- total supply. Its remaining supply is covered temperature supply with warmer water from the supply line from • New low-temperature instantaneous the neighbouring network. The advantage of heat exchanger the concept is that the supply capacity of These features result network heat loss re- an existing district heating network can be ducing from 4 % to 13-14 %. increased without requiring any further in- The low-temperature is supplied with a mi- vestment costs. Moreover, it provides a lo- xing shunt which regulates the temperature wer return temperature in the overall DH for the low-temperature network. The prima- network, which reduces the heat loss and ry heat source comes from the return line can provide higher efficiency in heat gene- of the medium temperature DH network. ration plant. The supply concept requires When the temperature in the return line is that there is an adjacent area with a suffici- not sufficient, water from supply line of the ent flow in the return line and a relatively medium temperature DH network will mix high return temperature. with return water to achieve the desired sup- In the project, it was found that the average ply temperature. The system therefore con- network supply temperature is 55 °C and re- sists of three pipes: two supply pipes and turn temperature is around 40 °C, which re- one return pipe. sults an overall cooling of about 15 °C. The In the full scale demonstration project, the less cooling is deemed to have given a gre- old inefficient DH pipes were replaced with ater need for pumping energy, but this is better insulated AluFlex pipes and the old still a small percentage compared to the to- water storage tank substations were re- tal savings in losses in networks. There are placed with low-temperature instantane- several explanations for the higher return ous heat exchanger substations. The hea- temperature, but the main reason is just too ted area is supplied through a mixing shunt great a bypass flow in some user installations and a booster pump. In the project, detailed caused by defective or incorrectly set con- measurements and data collection were trol valves. It is also considered that many performed. These measurement data are consumers do not close for „summer valve“ processed and analysed for the period Ja- in their water heater. The problem with that nuary 1st, 2012 to July 1st, 2013. consumers do not get closed summer val- The demonstration project showed that it ve may in future projects may be handled is feasible to supply LTDH to existing area with electronic, supplemented with a return with floor heating as space heating. The re- temperature limiter on space heating heat sults show that it is possible to supply DH exchangers. consumers with a flow temperature of 50 - Project lead was by COWI A/S and other par- 53 °C, which is sufficient to cover the space ticipating organisations Danfoss A/S, Logs- heating demand, and to permit the produc- tor A/S and Kamstrup A/S. The owner of tion of domestic hot water in a secure man- the demonstration site was Taastrup District ner. Comparing with old medium tempera- Heating. ture DH system which has average grid heat loss approximately 41 %, the new system reduces the heat loss down to 13 – 14 %. The energy efficient goal in the project has been met. The reduction in heat loss is a result of lower temperature in the DH network, and then heating pipes with better insulation properties. 70 7.2.7 Sea water heat recovery and heat pumps in Ulstein (Norway) In Ulstein (Norway), “Fjord” district heating is based on utilisation recovered heat from the sea and decentralized heat pumps. The recovered heat in low temperature is distributed to substations. Both heating and cooling is distributed using the same pipe network without any insulation. Low water temperature results in low heat losses and low operation cost. The local energy substation can be used for one or few buildings. The solution is suitable for locations on the coast. In Ulstein project, the sea water temperature was measured to be from 4 °C to 9 °C during the year at the depth of 42 m. In to- Figure 7-11 Pipelines for supplying water used as a heat source for heat tal about 15 energy substations will be con- pumps in a district heating system in Ulstein nected to the system. © Øyvind Amdam, Ulstein municipality In the beginning, 20 % of the customers are works. Furthermore, the company has de- included in the district heating system. After monstrated a process that district heating five years, the connection rate will be up to companies can follow when working towards 60 % and after 10 years 100 % of the ca- a low-temperature operation profile. During pacity will be utilized. Additional capacity of the process the network heat losses in Mid- 20 % as reserve is assumed to be utilized delfart have been lowered by almost 25 % within 20 years. The total heat supply deli- and the economic benefits where estimated vered by the district heating system will be to approximately 5.5 million DKK/year (0.7 higher than 10 MW within five years. Inclu- million EUR/year). Thereby, the case project ding the reserve capacity the plant should demonstrates that it is possible to obtain lar- deliver about 20 GWh heating and 5 GWh ge energy savings by optimizing the district cooling. It was assumed that the heating and heating temperatures in existing networks. cooling price will be about 0.7 NOK/kWh Middelfart district heating supplies heat (1 NOK ≈ 0.113 EUR). through two district heating networks, one The total investment within the first 10 years in the city of Middelfart and one in the smal- will be about 75 million NOK and 85 million ler nearby village Nørre Aaby. In Middelfart NOK within 20 years. the district heating network consists of approximately 139 km of pipe and supplies 7.2.8 Lower temperatures for existing heat to approximately 5000 customers. Cus- systems in Middelfart (Denmark) tomers cover a large range of different buil- The district heating company in the Danish dings but consist mainly of small customers city Middelfart has been supplying heat to such as single-family houses and few larger their consumers since 1963. During the customers such as schools. The building past 7 years, the company has been wor- mass in the city ranges from old buildings king hard to lower the temperatures in the to modern low-energy buildings. Middelf- district heating network, that now delivers art district heating is a distribution compa- heat to approximately 5000 customers. This ny, which means that they do not produce has resulted in a case project where sup- the heat, but buy it from a local heat supply and return temperatures have been lo- plier. The heat mainly consists of surplus wered from an average of 80.6 °C / 47.6 °C heat from an oil refinery, CHP production, in 2009 to an average of 64.6 °C / 40.0 °C and heat from a waste incineration plant. in 2015. The district heating company has The annual heat consumption in the city taken part in the development and test of is approximately 480,000 GJ per year. Key software tools that can help in reducing the numbers for Middelfart district heating are return temperature in district heating net- seen below and the heating network in Mid- www.iea-dhc.org 71 Figure 7-12 Illustration of the district heating network in Middelfart © Illustration Middelfart District Heating. delfart is illustrated in Figure 7-12. advice for the customers on how to improve Apart from development of software solu- their heating installation. This is both a be- tions in Termis (Schneider Electric 2017), nefit to the customers, who receive additio- the project also aimed to collect experien- nal service from the heating company, and ces on the practical work with Return Tem- for the company, as the return temperatu- perature Optimisation (RTO). The develo- res are continuously lowered in the network, ped software was installed amongst others when old inefficient installations are repla- at Middelfart district heating and the district ced. The service was provided by an emplo- heating company planned a process to lo- yee that continuously monitors the operation wer the district heating temperatures. This of the district heating network on the basis process required a new vision of the servi- of the new tools for data collection and Re- ces provided by the district heating compa- turn Temperature Optimisation. ny and a large amount of customer commu- When the return temperature is lowered, the nication. Whereas the district heating sys- price of the district heating becomes more tems are commonly considered to cover only favourable as heat losses are lowered, and heat production and distribution, Middelfart production efficiency is increased. In order district heating expanded their service to in- to motivate the customers to improve their clude customer installations inside the buil- heating installations and provide a more fair dings, as the operation of the district hea- distribution of the actual heat price on each ting substations were continuously monito- consumer, the district heating company in- red by the district heating company. The dis- troduced a return temperature tariff in their trict heating company was provided with an pricing structure. This tariff provides custo- overview of customers that need to make a mers with a low return temperature with a long term effort to lower a high return tem- financial bonus while customers with a high perature, or customers that experience a return temperature pay an extra cost accor- malfunction in their installation leading to a ding to the costs imposed on the district hea- sudden increase in the return temperature. ting company due to higher heat losses and If a substation is seen to provide a high re- lower heat production efficiency. The district turn temperature, the district heating com- heating company made a large effort to ad- pany offers a service check and provides vertise the new service provided and inform

72 about the new return temperature tariff that The main results of the project were: was implemented. The experiences from the • Development of system for collection project therefore include successful imple- and use of smart meter data from dis- mentation of a new district heating strategy trict heating substations where customer substations are included in • Development of extension for the real- the service area of the district heating com- time district heating operation software panies and customers pay, not only for their Termis, to include a module for return heating consumption, but also for the actu- temperature optimisation al cost they impose on the heating system. • Demonstration of the use of smart dis- Temperature optimisation provides a lar- trict heating meters and software for re- ge number of benefits for the district hea- turn temperature optimisation in existing ting company. First of all, the heat loss from district heating systems the pipe network is reduced when network • Practical experiences from the process temperatures are reduced. Reduction in re- of optimizing return temperatures in dis- turn temperature furthermore ensures more trict heating networks energy efficient heat production from hea- Project lead responsibility was on COWI A/S ting plants with flue gas condensation or and Middelfart District Heating had the ow- heating plants based on for example solar nership of the demonstration. Solution de- heating. Additional benefits include the fact velopers were Schneider Electric Denmark that when the return temperature is lowe- A/S (Termis) and MeterWare. Other parti- red, the same amount of heat can be deli- cipating organisation was Fjernvarmens vered at a smaller mass flow rate. Therefore, Udviklingscenter. pumping energy can be reduced and net- The project was started in 2009 and tem- work capacity increased. This can be very perature optimisation is continuously carried beneficial in district heating systems whe- out. Part of the demonstration was carried re the capacity limit has been reached, or out through a research and development where expansions are planned in the near project in 6/2013 – 12/2014. future. The benefits can be summarised as: • Lower heat loss from pipes 7.3 Summary and Conclusions from the • More efficient heat production Case Studies • Lower power consumption for pumping • Increased capacity in the district hea- Core objective for the description of case ting network studies was to identify and collect innova- The demonstration project has successful- tive demonstration concepts as examples ly shown how temperature optimisation can of success stories for communities interes- be implemented in existing district heating ted in developing low temperature district systems, and that it can lead to large ener- heating systems. Demonstrated cases in- gy efficiency improvements. The project de- clude use of advanced technologies and monstrates the possibility of including cus- interaction between different components tomer installations in the optimisation of the within the systems. Based on these expe- district heating system, by monitoring the riences, principles and lessons learned in operation of customer substations, provi- designing these systems are given. Measu- ding service checks for customer installa- rement data from community projects are tions, and implementing a return tempera- also used in validation of the models and ture tariff that motivates consumers to im- tools developed. prove heating system installations. Ultimate- There were a total of eight case studies ly the project provides software and process from Germany, Denmark, Finland, Norway tools that can help existing district heating and Great Britain. The district heating sys- companies to lower the temperatures in the tems were of very different sizes, from mini- networks. ature to city wide systems. Network lengths were from 165 m to 140,000 m. The connected buildings were detached, terraced and block houses, and mostly low energy or passive houses. Sources of heat were solar www.iea-dhc.org 73 collectors, heat pumps, CHP plants, excess area, supplied by a miniature district heating heat from industry or the systems were con- system with a trench length of 165 m. Heat nected to a larger network close by with heat supply consist of 20 m² solar thermal collec- exchangers. The temperature levels recor- tors, two 17 kW ground source heat pumps ded were typical for low-temperature sys- with 14 boreholes, two 20 kW air source tems, varying from 40 to 60 °C in supply and heat pumps and a 30 kW biomass boiler as 25 to 40 °C in return. Savings and increa- well as a 8 m³ thermal storage tank. The to- sed efficiencies were observed in every case tal capacity of the controllable heat sources studied. The Table 7-3 summarises the case is 105 kW with added capacity from solar systems by listing yearly heat demands and thermal collectors and the storage unit. The distribution temperatures as well as giving a heat pumps can work in series so that at first short description of each concept studied. stage water is heated up to 45 °C and at the second stage up to 55 °C. Each house is fit- Greenwatt Way in Slough (UK) has a sys- ted with a substation with direct connection tem of 10 dwellings with 845 m² heated floor for space heating and with a heat exchanger

Table 7-3 Summary of the case study systems. Case Heat demand Temperatures Short description system Slough 49.6 MWh/year 52/32 °C Miniature district heating system with 10 dwellings and solar collectors, (UK) ground and air source heat pumps, biomass boiler and a heat storage as heat supply options.

Ludwigs- 825 MWh/year 40/25 °C Storage and heat supply capability in consumer substations, two-way con- burg nection to a local low temperature district heating system. CHP unit and (Germany) ground source heat pumps as the centralised heat supply options.

Wustenrot 376 MWh/year 40/30 °C Decentralised heat pumps for each consumer, utilising heat from collector (Germany) pipes buried in agricultural fields. All dwellings are passive houses with PV systems on roof-tops. Cold water network can also be used for cooling and rejection of excess heat. Kassel 1,827 MWh/year 40/30 °C Low temperature district heating system for 127 buildings with heat supply (Germany) consisting of solar collectors, a centralised ground heat pump with boreholes that can be utilised also as seasonal heat storage. Use of electric heating elements or solar collectors for DHW production is studied. Hyvinkää 630/1,371 MWh/ 65/35 °C Building fair area with local district heating system consisting of 40 con- (Finland) year sumers. Solutions for combining distributed solar collector systems and district heating, the effect of connection rate and low distribution temperatures are studied. Sønderby 975 MWh/year 55/40 °C Complete renovation of pipe system for a part of a larger district heating sys- (Denmark) tem. Reduced distribution temperatures and return flow in the core network used as the main heat supply. Heat losses reduced approximately by 66 %.

Ulstein 20,000 MWh/year 4-9 °C Cold district heating system using sea water as the heat source for de- (Norway) centralised heat pumps at the consumer buildings. Can also be utilised as free cooling.

Middelfart 118,000 MWh/ 64.6/40 °C Demonstration of process for lowering the supply and return temperatures (Denmark) year systematically across a large scale system of 5000 consumers and 139 km of pipes. Issues with individual consumers mostly corrected by normal service operations. In addition to lower supply temperatures, the return temperatures could be lowered as well, reducing the effect of normally increased flow rates. Tools developed for dynamic simulation of temperature levels within the network. 74 for domestic hot water. Radiators are dimen- bes being 0.5 to 1.0 m. The cold water net- sioned for 55/35 °C temperatures. Dome- work can be also used for direct cooling of stic hot water is supplied at 43 °C. Exhaust the buildings in summer time. The system air heat recovery systems are connected also offers a possibility to use the network to the radiators. The houses are equipped as a heat sink for the heat pumps and can with solar panels benefitting from a feed-in utilise heat sources like condensing heat of tariff. The total budget of the pilot project cooling systems and other sources for highly was £3.65 million. The project was started efficient use of energy. In the demonstration in 2009 and measurements were carried system this concept was demonstrated and out from 4/2011 to 3/2012. The measured analysed by integration of a cooling system supply of heat was 49.6 MWh and heat de- in a nearby supermarket. Six to eight buil- mand 35.7 MWh indicating 28 % heat los- dings were monitored as a first step, exten- ses within the system. The average cooling ded later to 10 to 15 buildings. Total dura- in the system was 20 °C during and 12 °C tion of the monitoring activity was planned outside the heating season. Relative month- to be 3-4 years. Monitoring period started in ly heat losses were 60 % at highest in sum- 3/2014 with the main targets being the de- mer and 20 % at lowest in winter. monstration of efficiency, economic viabili- An energy efficient district heating system ty and system and building energy manage- in Sonnenberg district of Ludwigsburg (Ger- ment as well as the operation of cold water many) was studied as a case system. Target network and agro-thermal collectors. The of the project was to develop a simulation simulated heat demand for a single house environment for studying integration of dis- was 20.35 MWh and electricity consump- tributed renewable heat sources in existing tion 4.1 MWh. Measured heat demand for and new systems. The focus was in demand ten months was 27.2 MWh and electrici- side management of the system, building ty demand 5.4 MWh. The heat pump COP level heat supply and storage and substati- was 4.8 in average with variation between on level solutions enabling heat trade within 2.5 to 6.5. The project ran from 11/2012 the district heating system (two-way district to 6/2016. heating). Partial results of this project will The case study “Zum Feldlager” in Kas- be implemented on a real heating network sel (Germany) is a low temperature district in the Sonnenberg district. A new low tem- heating system supplying heat for 127 buil- perature (40/25 °C) extension to the exis- dings by utilising solar collectors, a centra- ting (70/40 °C) district heating network has lised ground heat pump with boreholes uti- been established. The heat supply consists lised also as seasonal heat storage. Heat of a 350 kW gas CHP plant and a 200 kW storage is loaded by unglazed solar collec- geothermal heat pump. The project started tors (swimming pool absorbers as the low- in 1/2012 and ended in 3/2015. cost option). The buildings are south-fa- The Wüstenrot (Germany) case study repre- cing, specific heat demand being 45 kWh/ sents a plus energy community. It consists m²·a and domestic hot water demand 730 of 24 mostly single family houses, built al- kWh/person·a. Resulting total heat demand most according to local passive house stan- is less than 50 kWh/m²·a. The supply tem- dard. All buildings have large solar panel perature in the district heating network is systems on the roof-tops and battery sto- 40 °C. Connection for the space heating is rages. The heat demand of the buildings is implemented using heat exchangers, but for supplied by decentralised heat pumps and the preparation of domestic hot water the- heat storages, which in turn are connec- re are different options; thermal solar coll- ted to a centralised geothermal system. This ectors (e.g. flat-plate collectors) or an elec- system consists of a cold water district hea- tric heating element complementing district ting network delivering low temperature wa- heating. Aim is to find an optimal balance ter from a novel agro-thermal collector to the between the economy, use of electric hea- heat pumps within the buildings. The con- ting, available solar output and distributi- cept includes activation of agricultural fields on heat losses in the network. The project as geothermal collectors by ploughing tubes was started 11/2015 and ended 8/2017. In in 2 m depth, the distance between the tu- late 2016, the decision has been made not www.iea-dhc.org 75 to realize this project approach because of annual heat consumption of the buildings time constraints. Total investment is estima- (based on heating seasons 2004/2005 - ted to 3.7 Million EUR, including a 1.0 Mil- 2009/2010) was in range of 5 - 23 MWh/ lion EUR for research. house. In the demonstration project, the old A district heating system in Hyvinkää (Fin- inefficient pipes within the network were re- land) building fair (2013) area was a case placed by better insulated pipes and the old study for investigating low temperature dis- water storage tank substations were repla- trict heating. The building fair area consists ced with heat exchanger substations. The of 40 consumers within an area of 17 ha. In low-temperature network in the area uses the implemented system, about half of them return pipeline in the medium-temperature are connected to district heating system, the network from the neighboring Taastrup dis- rest having a building specific heating sys- trict heating network as heat supply. Mea- tem; e.g. combination of solar PV and coll- surement data was processed and analyzed ectors or a heat pump. Heat distribution sys- for a period between 1/2012 and 7/2013. tem in the houses can be floor heating, ra- The supply temperature averaged at 48 °C diators and ventilation based heating. Diffe- with heat from the return pipeline covering rent options for connecting detached hou- about 80 % of the total heat supply. The re- ses to the district heating system were ana- maining heat was supplied by warmer wa- lyzed. Houses with solar collectors and a ter from the feed pipeline in the neighboring district heating connection were studied as network. The results showed that it is possi- well. Results of simulations showed that the ble to provide consumers a supply tempe- majority of the solar energy is used for the rature of 50 - 53 °C, which is sufficient for domestic hot water, covering about half of its space heating and domestic hot water sup- annual heating needs. Solar energy availab- ply. Heat losses in the old medium tempera- le for space heating is negligible. Simulati- ture system were approximately 41 % while ons of different district heating network con- in the new system reached heat losses of figurations showed the impact of connection 13 – 14 %. The reduction was due to lower rate. For 100 % connection rate case and supply temperature and better insulation in adequate network structure, the yearly rela- pipelines. The average supply temperature tive heat losses were at a reasonable 10 % was 55 °C and return temperature is around level. The low (47 %) connection rate case 40 °C, which results an overall cooling of resulted in 20 % heat losses. Temperature about 15 °C. The reduced cooling resulted variation and drop within the network espe- in greater need for pumping, but in costs cially outside heating season was observed this was comparably small in total savings as a peculiarity for a low heat demand dis- due reduced heat losses. There are sever- trict heating system. By-pass arrangements al explanations for the higher return tempe- were used to stabilize the flow and temperatures, but the main reasons are too high ratures at the cost of increased heat losses, bypass flow in some substations caused by but service pipes still experienced a signi- defective or incorrectly set control valves. ficant temperature drop. Low temperature One advantage of the concept is the incre- variation for distribution resulted in lower ased available capacity for the existing dis- heat losses, but approximately doubled con- trict heating system without any investment sumption of electricity in pumping. on production. The demonstration project in Sønderby In Ulstein (Norway) fjord district heating is (Denmark) was a full scale renovation of a based on utilisation of the “free” heat from part of an existing district heating system the sea by using decentralized heat pumps. enabling a change from traditional distri- A common heat exchanger is utilized to take bution temperatures to a low temperature the heat from the sea. The sea heat with low system. The area included 75 single fami- temperature is then distributed to energy ly houses with the living area of 110 to 212 substations. Both heating and cooling are m² each, built in 1997-1998 with under- distributed by using the same pipe network floor heating systems. The houses originally without insulation. The local energy subs- had hot water tanks for domestic hot wa- tation could be used for one or few buil- ter supply (110 l or 150 l in volume). The dings. This solution with utilisation of sea 76 heat and decentralized heat pumps is sui- been reduced by 25 % and the economic table for places located at coast. The total benefits were estimated to be approximate- heat supply delivered by the district heating ly 5.5 million DKK (0.7 million EUR). The system will be higher than 10 MW within five economic savings obtained from the tem- years. Including the reserve capacity, the perature reduction consist of savings due plant should deliver about 20 GWh heating to lower heat loss and savings from a re- and 5 GWh cooling. turn temperature tariff that is paid to the lo- Middelfart (Denmark) district heating com- cal heat supplier. The savings have been pany has succeeded in lowering supply and estimated to be in the size of 110,000 DKK/ return temperatures in their system from an year per °C (14,650 EUR/year per °C) due average of 80.6/47.6 °C to 64.6 /40.0 °C to heat loss reduction and 380,000 DKK/ during 2015. The district heating network year per °C (50,650 EUR/year per °C) due to in question is 139 km long in pipe length the tariff to the heat supplier. The demons- and services approximately 5000 custo- tration project has successfully shown how mers. The heat supply consists of surplus temperature optimisation can be implemen- heat from an oil refinery, a CHP plant and ted in existing district heating systems, and a waste incineration plant. The annual heat that it can lead to a significant energy effici- consumption is approximately 480,000 GJ. ency improvement. The project demonstra- The district heating company has taken part tes the possibility of including customer in- in the development and testing of software stallations in the optimisation of the district tools that have helped in reducing the also heating system by monitoring the operation return temperature in district heating net- of customer substations, providing service work. Furthermore, the company has de- checks for customer installations, and im- monstrated a process that district heating plementing a return temperature tariff that companies can follow when aiming for a low- motivates consumers to improve their own temperature distribution. During the process internal heat distribution systems. the network heat losses in Middelfart have

www.iea-dhc.org 77 8 CONCLUSIONS Low temperature district heating is a heat rature district heating for space heating and supply technology for efficient, environmen- domestic hot water for various types of buil- tal friendly and cost effective community dings, to distribute heat with low heat los- supply. In comparison to conventional dis- ses and ability to recycle heat from low tem- trict heating, the network supply tempera- perature waste heat and renewable energy ture is reduced down to approximately 50 °C sources. From various research and deve- or even less. To achieve maximum efficien- lopment of low temperature district heating cies, the energy conversion process, the dis- projects, it has been shown that it is both trict heating network and the end user ins- technically feasible and economically sound tallation within the supplied buildings need to change current high/medium tempera- to be optimized to utilize lower network sup- ture district heating system to low tempera- ply temperatures. Therefore, the focus of ture district heating for both new and exis- the DHC Annex TS1 is on low temperature ting building areas. district heating for the application in space As part of the IEA DHC Annex TS1 project heating and domestic hot water preparation. promising technologies and ideas for low The main objective of the DHC Annex TS1 temperature district heating application is to demonstrate and validate the potential have been collected and identified to meet of low temperature district heating as one of the goals of future renewable based com- the most cost efficient technology solution munity energy systems. Innovative techno- for heating energy supply to achieve 100 % logies and advanced system concepts in low renewable and GHG emission-free energy temperature district heating are reported for systems on a community level. This objecti- heat generation, distribution and end user ve is obtained by the development and coll- utilization. In a special technology chapter ection of assessment tools as well as pro- (chapter 4) background materials and cut- viding guidelines, recommendations, best- ting edge knowledge on district heating pipe practice examples and background materi- systems, network designs, hygienic dome- al for designers and decision makers in the stic hot water preparation in low tempera- fields of building, energy production/sup- ture supply schemes, space heating cont- ply and politics. rols and the integration of small scale decen- The benefits of low temperature district hea- tralized heat sources is provided for desig- ting are both in heat distribution and heat ners as well as decision makers in the buil- generation. In the heat distribution, the heat ding and district energy sector. losses, the thermal stress and the risk of To meet the goals of future renewable based scalding are reduced and the quality match community energy systems improved inter- between heat supply and heat demand is faces in district heating need to be estab- improved. In the heat generation, lower sup- lished and may be explained via hard and ply and return temperature helps to improve soft issues in chapter 5. Here, energy pl- the power to heat ratio in combined heat and anning of the future integrated energy sys- power plant and recover waste heat through tems is identified as a complex problem. The flue gas condensation. Low supply tempera- analysis of the future heat demand showed tures help to achieve higher efficiencies for that the district heating would still be nee- heat pumps, and enlarge the utilization of ded for most of the buildings in 2050, indu- low-temperature waste heat and renewab- cing that the low temperature district hea- le energy. Low temperature district heating ting would be a promising heat supply for has been continuously developed and is rea- the future and for many buildings. Consi- dy to replace the currently used district hea- dering that there is enough available heat ting systems. from renewables and waste heat sources at Low temperature district heating based on the low temperature level, the low tempera- renewable energy can substantially reduce ture district heating will be of high relevan- total greenhouse gas emissions and secure ce in the future. For future development of energy supply for future development of so- the district heating and a high reliability of ciety. It has the ability to supply low tempe- the low temperature district heating, stati- 78 stical data and knowledge on the heat los- The Easy District Analysis (EDA) tool was ses and how operation and temperature le- developed, based on the identified requi- vels may contribute to the distribution los- rements for a simplified district heating pl- ses are highly necessary. For example, only anning tool. The intended target groups of companies that have a long-term plan to in- the tool are urban planners and planners clude renewable energy sources have good in utility companies. The tool is intended to databases and documentation on heat los- be used in the pre-planning phase of a dis- ses and temperature levels. trict energy system. The focus of the tool The integration of distributed energy sys- is on the evaluation of the impact of diffe- tems will be realized by a new actor at the rent grid temperatures (e.g. standard district district heating market called “prosumer”. A heating vs. low temperature district heating) prosumer is a customer that both produces and of different operation modes (technical and consumes heat from the district heating vs. economic operation) of district heating system. An increasing number of the prosu- technologies. The assessment is based on mers will require a transformation of today’s the parameters primary energy consumpti- district heating network into smart grid. New on, carbon emissions and heat production and intelligent control strategies for the ma- costs. nagement of the different temperature levels The practical application of the tool is shown and differential pressures in the network are in the assessment of a case study with an of greatest importance to enable the suc- existing housing stock. Based on the iden- cessful connection of the prosumers into the tification of the initial heating systems and district heating system. Therefore, intelligent building standards as well as the costs for a data management may create new business change of energy carriers, suitable areas for models for both the district heating compa- a possible realization of low temperature dis- nies and the information technology sector. trict heating schemes can be determined. For the identification of integral and innovati- This assessment includes technical and so- ve approaches to low temperature heat sup- cio-economic criteria from different groups ply at municipal level, an overview of exis- of actors and actor-specific measures could ting evaluation methods is provided in chap- be identified to support the implementation ter 6. Initially, a classification form for lo- of low temperature district heating. cal and district heating models was develo- Core objective for the description of case ped and distributed to tool developers. Af- studies in chapter 7 was to identify and to ter obtaining the completed classification collect innovative demonstration concepts forms from the Annex participants, the pl- as examples of success stories for commu- anning tools were assessed in seven cate- nities interested in developing low tempe- gories: analytical approach (energy system rature district heating systems. Demonstra- model, thermodynamic model, other), tar- ted cases include the use of advanced tech- get group of users (municipal authorities, nologies and the interaction between diffe- professional planners, R&D), level of detail rent components within the systems. Based (geographical scope, time horizon), model on these experiences, principles and less- type (simulation, optimization), demand ca- ons learned in designing these systems are tegories (households, commercial, indust- given. Measurement data from communi- ry, transportation), final energy consumpti- ty projects are also used in validation of the on (electricity, heat, transport) and used va- models and tools developed. riables (costs, energy, exergy, temperature). There were a total of eight case studies The evaluation has shown some promising from Germany, Denmark, Finland, Nor- approaches for low temperature district hea- way and Great Britain. The district heating ting. However, there was none found to be systems were of very different sizes, from fully appropriate for the objective of a sim- smaller building groups to city wide sys- plified, holistic tool for low temperature dis- tems. Taking into account the size of the trict heating. By evaluating the selected pl- supply area, the network lengths vary from anning tools for district heating schemes, re- 165 m to 140,000 m. The connected buil- quirements can be derived for the develop- dings were residential buildings of diffe- ment of a simplified planning tool. rent sizes, and mostly low energy or passi- www.iea-dhc.org 79 ve houses. Sources of heat were solar collec- 40 °C in return. Savings and increased effici- tors, heat pumps, CHP plants, excess heat encies were observed in every case studied. from industry or the systems were connec- The material collected and summarized in ted to a larger network close by with heat ex- this guidebook show that low temperature changers. The temperature levels recorded district heating is a key enabling technolo- were typical for low-temperature systems, gy to increase the integration of renewable varying from 40 to 60 °C in supply and 25 to and waste energy for heating and cooling.

Low temperature district heating is one of the most cost efficient technology solutions to achieve 100 % renewable and GHG emission-free energy systems on a community level.

80 REFERENCES

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86 Schneider Electric (2014). Termis – District Thorsen, J.E. and Gudmundsson, O. (2012). Energy Management, internal description. District heating application handbook: Ma- Rueil-Malmaison, France. king applications future proof all our knowledge – is now yours. 1st Edition. Danfoss Schneider Electric (2017). Homepage: soft- District Energy Application Centre. Danfoss ware.schneider-electric.com/products/ter- A/S, Nordborg, Denmark. mis. Accessed on August 11, 2017. Thorsen, J.E., Gudmundsson, O., Brand, SIA 385/1 (2011). Anlagen für Trinkwarm- M. and Funder-Kristensen, T. (2016). Uti- wasser in Gebäuden – Grundlagen und An- lizing Excess Heat from a Supermarket Re- forderungen, Switzerland. frigeration System in a District Heating Grid. Sipilä, K., Rämä, M., Zinko, H., Ottosson, U., Euro Heat & Power, Issue III/2016, EW Me- Williams, J., Aguiló-Rullán, A. and Bøhm, B. dien und Kongresse GmbH, Frankfurt/M., (2011). District heating for energy efficient Germany. building areas, IEA DHC Annex IX, Report VDI 4655 (2008). Reference load profiles of 8DHC-11-02. 2011. single-family and multi-family houses for the Statistics Norway (2017). Homepage of Sta- use of CHP systems, May 2008. tistics Norway. www.ssb.no. Accessed on Verenum (2014). Status Report on District August 31, 2017. Heating Systems in IEA Countries. Verenum Tamminen, E., Kekkonen, V. and Wistbacka, Ingenieurbüro für Verfahrens-, Energie- und M. (1994). Optimization of the operation of a Umwelttechnik, Zürich, Switzerland. heat storage connected to a heat and power Viborg Fjernvarme (2011). Strategi for tem- production system. CALORSTOCK'94. 6th peraturniveauet i Viborg Fjernvarmes led- International Conference on Thermal Ener- ningsnet 2011-2025. Viborg Fjernvarme, Vi- gy Storage. Espoo, 22 - 25 August 1994. borg, Denmark In: Proceedings. M.T. Kangas & P.D. Lund (eds.). Helsinki University of Technology, VROM (2000). Ministerie van Volkshuisves- Department of Technical Physics. Finland. ting, Ruimtelijke Ordening en Milieubehe- er: Modelbeheersplan legionellapreventie in Tereshchenko, T. and Nord, N. (2016). Im- Leidingwater. Den Haag, The Netherlands. portance of Increased Knowledge on Relia- bility of District Heating Pipes. In: Procedia Wallenius (2017). Homepage of Wallenius Engineering, Vol. 146. pp. 415-423. Water AB, Sweden. www.walleniuswater. com. Accessed on August 14, 2017. TheLowEnergyCommittee (2009). Efficien- cy improvement, Homepage of the Norwe- Yang, X. (2016). Supply of domestic hot Wa- gian Ministry of Petroleum and Energy, ht- ter at comfortable temperatures by low-tem- tps://www.regjeringen.no/globalassets/up- perature district heating without risk of Legi- load/OED/Rapporter/OED_Energieffekti- onella. PhD Thesis. Department of Civil En- visering_Lavopp.pdfhttps://www.regjerin- gineering, DTU-Technical University of Den- gen.no/globalassets/upload/OED/Rappor- mark, Lyngby, Denmark. ter/OED_Energieffektivisering_Lavopp.pdf . Accessed on August 21, 2017. Yang, X., Li, H. and Svendsen, S. (2015). Alternative solutions for inhibiting Legionel- Thorsen, J.E. (2010). Analysis on flat stati- la in domestic hot water systems based on on concept (preparing DHW decentralized low temperature district heating. In: Building in flats), Proceedings of the 12th Internatio- Services Engineering Research and Techno- nal Symposium on District Heating and Coo- logy, Vol. 9, pp. 141-151. ling, Tallinn, Estonia. Yang, X., Li, H. and Svendsen, S. (2016). Evaluations of different domestic hot water preparing methods with ultra-low-temperature district heating. In: Energy, Vol. 109, pp. 248-259. www.iea-dhc.org 87 Yang, X., Li, H. and Svendsen, S. (2016a). Zhang, J., Ge, B. and Xu, H. (2013). An Energy, economy and exergy evaluations equivalent marginal cost-pricing model for for supplying domestic hot water from low- the district heating market. In: Energy Poli- temperature district heating in Denmark. In: cy, Vol. 63, pp. 1224-1232. Energy Conversion and Management, Vol. 122, pp. 142-152. Zinko, H., Bøhm, B., Kristjansson, H., Ot- toson, U., Rämä, M. and Sipilä, K. (2008). Yang, X. and Svendsen, S. (2014). New so- District heating distribution in areas with low lution for supplying domestic hot water. 3rd heat demand density, IEA DHC Annex VIII. annual conference on 4th generation District Heating. Aalborg University, Denmark. YM (2007). National Building Code of Fin- land D1: Water supply and sewerage equipment of properties, regulations and guidelines, Ministry of the Environment – YM, Finland.

88 LIST OF ABBREVIATIONS

4GDH 4th Generation District Heating BHE Borehole Heat Exchanger CB Comfortable Bathroom Concept CHP Combined Heat and Power COP Coefficient of Performance CSH Code for Sustainable Home in UK DH District Heating DHC District Heating and Cooling DHSU District Heating Storage Unit DHW Domestic Hot Water DWC Domestic Water Cold DWH Domestic Water Hot EDA Easy District Analysis – Tool GHG Green House Gas IEA International Energy Agency IHEU Instantaneous Heat Exchanger Unit LCA Life Cycle Assessment LCC Life Cycle Cost Analysis LTDH Low Temperature District Heating MFH Multi-Family House OECD Organization for Economic Cooperation and Development PV Photovoltaic RES Renewable Energy Source RTO Return Temperature Optimization SDH Semi-Detached House SFH Single Family House SH Space Heating TCP Technology Collaboration Platform TH Terraced House TRV Thermostatic Radiator Valve www.iea-dhc.org 89 APPENDIX A: NATIONAL STANDARDS AND GUIDELINES ON DOMESTIC HOT WATER OF IEA DHC PARTICIPATING COUNTRIES One of the main issues and challenges of low temperature district heating supply regarding hygienic aspects of domestic hot water DHW supply are temperature levels below 60 °C and sizes of the system of more than 3 litres (Brand 2013, Yang 2016 and Bartram et al. 2007). The required temperature levels for safe and hygienically unexceptionable DHW supply vary from to country. Against this background an analysis of regulations and guidelines of the member countries participating in the project "IEA DHC Annex TS1" in the program “District Heating and Cooling” (DHC) of the International Energy Agency are analyzed and documented. An overview of the regulations and guidelines is given below.

Member Description Standardisation Country Denmark The national regulation DS 439 (DS 439 2009) states that the DS439:2009 Code of practi- DHW system should be designed to be capable of preparing ce for domestic hot water DHW at 60 °C and maintain at least 50 °C in all the distribu- supply installation tion lines. During peak load a minimum temperature level of 45 °C is sufficient. In contrast to EN 806 (EN 806-1:2000 and EN 806-2:2005) there is no differentiation in small and large systems. In traditional DHW systems, mostly due to large system volume of e.g. storages, it has to be ensured that the return temperature from the DHW recirculation is 50 °C in order to prevent the risk of Legionella. As a consequence, the current DH minimum supply temperature is above 60 °C. Finland The temperature level in the entire DHW system has to be at National Building Code of least at 55 ° C. In case of peak load, this temperature may drop Finland D1: Water supply for maximal ten seconds. Due to the risk of scalding the maxi- and sewerage equipment of mum permitted temperature level of DHW is 65 °C. In case of properties, regulations and DH supply it is recommended that substations have to be de- guidelines signed so that the DHW from the heat exchangers (HE) is hig- (YM 2007) her than 58 °C. In case of DHW commonly instantaneous HEs are used. As a result the current DH minimum supply temperature is above 60 °C. Germany The regulation is valid for all new systems with a storage size DVGW-Arbeitsblatt W551 - > 400 litres and a hydraulic loops > 3 litres, if they are not Technische Maßnahmen zur installed in a single- or two-family houses. There should be at Minderung des Legionellen- least 60 °C at the water outlet of the boiler. The temperature wachstums in Neuanlagen difference inside the pipe network is supposed to amount 5 °C (DVGW W551 2004) maximum, circulation included. Pipes over several floors with a water volume > 3 litres should be equipped with an additional circulation pipe or self-regulating trace heating. The circulation or electrical trace heating must not be interrupted for longer than 8 hours per day. In case of DHW preparation using DH a hot water temperature of more than 60 °C has to be maintained in order to avoid contamination of the hot water system with legionella.

90 Member Description Standardisation Country Great Britain The temperature level of the DHW systems including the sto- HSG274 Legionnaires’ di- rage may not drop below 60 °C. At the tapping point a tempe- sease: Technical guidance rature level 50 °C of DHW should be reached within one mi- Part 2 (HSE 2014) nute, in buildings with high hygienic standards at 55 °C. Si- gnificant higher temperatures should be avoided because of the risk of scalding. In case of a DHW supply using instantaneous heat exchangers, the required temperatures and time specifications do not have to be fulfilled. In case of using instantaneous heat exchangers it has to be ensured, that installation is directly connected to the DHW supply. The volume between pipe and heat exchanger should be less than one lit- re and the volume between heat exchanger and tapping point should less than 1.5 litres. The maximum permissible temperature level of DCW is 20 °C. Korea The required temperatures varies depending on the case of Technical Guidelines (Se- application: oul Housing & Communities Inlet temperature (heat generator) Corporation) (ISH 2017) Central heating 120-180 °C (ΔT: 40 K) District/local heating supply Seoul Housing & Communities Corporation: 115-60 °C (ΔT: 55 K) Korea District heating Corporation: SH 115-50 °C (ΔT: 65 K) Required temperature level of the DHW inside the storage Central heating 60-50 °C (ΔT: 10 K) Local heating 60-50 °C (ΔT: 10 K) District/local heating supply Seoul Housing & Communities Corporation: 60-45 °C (ΔT: 15 K) Korea District heating Corporation: SH 60-45 °C (ΔT: 15 K) Norway The DHW system must be designed so that the temperature at Prevention of Legionel- any tap point in the system reaches at least 60 °C within one la – guidelines, 3. edition, minute after opening a tap. The return temperature in DHW sys- chapter 7. National Institu- tems with continuous water circulation must not be less than te of Public Health (Petter- 60 °C. Due to hygienic reasons the whole DHW system must sen 2015) be flushed regularly with water at a temperature of at least 70 °C. The temperature in DHW storages must be at least 70 °C. The same conditions must be fulfilled for DHW connected to district heating systems. Sweden Installations for domestic hot water should be designed so that 6: BFS 2015:3 BBR 22 - a water temperature of less than 50 °C can be achieved af- Section 621 (BFS 2011:6) ter the tap. To reduce the risk of scalding, the temperature of the hot tap water is limited to 60 °C after the tap. If there is a special risk of accidents the temperature of the hot tap water has to lower than 38 °C. Devices for control of DHW should be designed so that the risk of injury from the confusion of domestic hot and cold tap water is limited. The heat-up of the DCW system must be avoided.

Next to the detailed analysis of the regulations and guidelines of the IEA DHC Annex TS1 member countries, the regulations of further DHC member countries are reviewed. In Cana- da, electrical heat generators have a factory default settings of 60 °C. In the US the requirement of warm water is at about 5,000 kWh per apartment and year which is nearly twice as the demand in Germany. This is mainly due to the reason that dishwasher and other sectors in industry and households are directly supplied with warm water. The operating temperature of condensing boilers is at 48 °C which is also suggested by the government (Dal- la Rosa et al. 2014). The general recommendation of the “ASHRAE Guideline 12-2000” (ASHRAE 2000) also used in Canada and the USA is a system temperature of 55 °C. In the Netherlands, the “Modelbeheersplan legionellapreventie in Leidingwater” obliges that the temperature of drinking warm water systems must not drop below 60 °C (VROM 2000). In www.iea-dhc.org 91 France, the temperature at the tapping point for personal hygiene should not exceed 50 °C, as it is regulated in “Arrête du 30 novembre 2005 modifiant l’arrêté du 23 juin 1978 - Ins- tallations for the distribution of domestic hot Water“ (JORF 2005). At other tapping points, temperatures up to 60 °C are allowed. In addition to that, it is distinguished in small and large plants analogically to the German regulation. For large-scaled plants, there are further specifications: the temperature at the generator outlet must not drop below 55 °C and there has to be a periodical thermal flush. In the Switzerland the national norm SIA 385 (SIA 385 2011) states that the outlet temperature of the water heaters should be 60 °C, the temperature level of warm kept pipes (circulation and warm keeping system till access into the water heater) is 55 °C and at the tapping point at least 50 °C. Systems with temperatures lower than 60 °C, e.g. fresh water stations, are possible, but they have to be heated up to 60 °C for one hour once a day (disinfection) (SIA 385 2011). The analysis of the different regulations shows that regulations of the different countries are dealing mostly with traditional DWI with mostly high volumes for drinking water supply. The technical methods for the supply of drinking water, described as part of the regulations and guidelines, consider especially hygienic aspects due to a minimisation of health risks. Al- ternative and energy efficient methods are not or only insufficiently regarded.

92 APPENDIX B: IEA DHC ANNEX TS1 PARTICIPANTS Denmark: Hongwei Li Germany: Markus Stehle Department of Civil Engineering Institute of Energy Economics and the Ra- Technical University of Denmark tional Use of Energy (IER) Phone: +45 4525 5025 University of Stuttgart E-mail: [email protected] Phone: +49 711 685- 87831 E-mail: [email protected] Denmark: Svend Svendsen Department of Civil Engineering Germany: Ruben Pesch Technical University of Denmark Centre for Sustainable Energy Technology Phone: +45 2261 1854 University of Applied Sciences Stutt- E-mail: [email protected] gart Phone: +49 711 8926 2981 Denmark: Oddgeir Gudmundsson E-mail: [email protected] Danfoss A/S Phone: +45 2944 1563 Germany: Dirk Pietruschka E-mail: [email protected] Centre for Sustainable Energy Technology University of Applied Sciences Stutt- Finland: Maunu Kuosa gart Aalto University Phone: +49 711 8926 2674 Phone: +358 50 538 1394 E-mail: [email protected] E-mail: [email protected] Germany: Heiko Huther Finland: Miika Rämä AGFW | Energy Efficiency Association for VTT Technical Research Centre of Fin- Heating, Cooling and CHP land Phone: +49 69 6304 206 Phone: +358 40 592 4000 E-mail: [email protected] E-mail: [email protected] Germany: Maria Grajcar Finland: Kari Sipilä AGFW | Energy Efficiency Association for VTT Technical Research Centre of Fin- Heating, Cooling and CHP land Phone: +49 69 6304 281 Phone: +358 20 722 6550 E-mail: [email protected] E-mail: [email protected] Germany: Andrej Jentsch Germany: Markus Blesl AGFW | Energy Efficiency Association for Institute of Energy Economics and the Ra- Heating, Cooling and CHP tional Use of Energy (IER) Phone: +49 251 149 1260 University of Stuttgart E-mail: [email protected] Phone: +49 711 685 87865 E-mail: [email protected] Germany: Anna Kallert Fraunhofer Institute for Wind Energy and Germany: Michael Broydo Energy System Technology (IWES) Institute of Energy Economics and the Ra- Phone: +49 561 804 1876 tional Use of Energy (IER) E-mail: [email protected] University of Stuttgart Phone: +49 711 685-87859 Germany: Dietrich Schmidt E-mail: [email protected]. Fraunhofer Institute for Wind Energy and de Energy System Technology (IWES) Phone: +49 561 804 1871 E-mail: [email protected]. de www.iea-dhc.org 93 Norway: Natasa Nord Republic of Korea: Jie Liu Department of Energy and Process Engi- Energy Network Lab. neering Korea Institute of Energy Research Norwegian University of Science and (KIER) Technology (NTNU) Phone: +82 10 9316 7160 Phone: +47 735 933 38 E-mail: [email protected] E-mail: [email protected] Sweden: Süleyman Dag Norway: Tymofii Tereshchenko Uponor AB Department of Energy and Process Engi- Phone: +46 223 38 001 neering E-mail: [email protected] Norwegian University of Science and Technology (NTNU) United Kingdom: Robin Wiltshire Phone: +47 735 983 81 BRE Building Research Establishment E-mail: [email protected] Phone: +44 782 542 8427 E-mail: [email protected] Republic of Korea: Peter Byung-Sik Park Energy Network Lab. United Kingdom: Ciro Bevilacqua Korea Institute of Energy Research BRE Building Research Establishment (KIER) Phone: +44 782 542 8427 Phone: +82 42 860 3323 E-mail: [email protected] E-mail: [email protected]

Republic of Korea: Yong Hoon Im Energy Network Lab. Korea Institute of Energy Research (KIER) Phone: +82 42 860 3327 E-mail: [email protected]

94 APPENDIX C: ADDITIONAL INFORMATION FROM IEA DHC ANNEX TS1 All additional information is available via the homepage of IEA DHC: www.iea-dhc.org

Flyer The flyer gives an overview of the activities of the DHC Annex TS1 working group and a short introduction into the benefits and challenges of low temperature district heating schemes.

DHC Annex TS1 Guidebook A printable .pdf version of the “Future Low Temperature District Heating Design Guidebook”, the final report of this project, is available for those who prefer to get a good and consis- tent overview about the perspectives of low temperature district heating and its application.

Case Study Brochure The brochure “Successful Implementation of Innovative Energy Systems in Communities – with Low Temperature District Heating and Renewable Energy Sources” gives an overview of the identified case studies with short descriptions of the implemented technologies and the boundary conditions as well as local conditions.

Tool The EDA tool (Easy District Analysis) is an excel-based simulation tool that has been developed by the IER (Institute of Energy Economics and Rational Use of Energy) at the Uni- versity of Stuttgart (Germany) in cooperation with Annex TS 1 participants. It enables the easy analysis of districts in terms of energy consumption, CO2 emissions and costs of different DH supply options. More information is available directly from the Annex participants from IER Stuttgart.

Detailed Subtask Reports From two subtasks (compare Figure 1-1 on pageSeite 10) special and more detailed reports have been published. These are: • Subtask report A: Methods and Planning Tools • Subtask report D: Case studies and demonstrations The reports are freely available and can be found on the named homepage.

Material from Workshops: A number of workshops have been organized by the Annex TS1 participants to enhance the exchange with other experts. The proceedings from these workshops are available from the indicated homepage:

• Industry and R&D workshop on “Energy Efficiency and Hygiene in Drinking Water Installations” Norwegian University of Science and Technology, Trondheim, Norway May 20, 2015

• Industry and R&D workshop on “Transition of Existing District Heating Grids to Low Temperature Grids” Danfoss A/S Headquarters, Nordborg, Denmark September 23, 2015

www.iea-dhc.org 95 • Industry and R&D workshop on “Realization of Innovative Low Temperature District Heating Systems in Communities” Frankfurt Fair and German Heat & Power Association, Frankfurt, Germany April 21, 2016

Conference Sessions: Two special sessions on the topics of Annex TS1 have been arranged by the working group. More detailed material of the sessions is available from the Operating Agent:

• Technical Session of Annex TS1 on “Fossil Free Building Stock Realized Based on Low Temperature District Heating!” at CLIMA 12th REHVA World Congress, Aalborg, Denmark May 24, 2016

• Special Session of Annex TS1 on “Low Temperature District Heating for Future Energy Systems” at 15th International Symposium on DHC 2016, Seoul, Korea September 06, 2016

Published articles A large number of conference articles and journal papers have been published by the An- nex TS1 participants. A list of references is available via the homepage.

Technical presentations A series of technical presentations were prepared for the biannual IEA DHC Executive Com- mittee (ExCo) meetings during the working time of Annex TS1 and are available from the Operating Agent.

THE LOW TEMPERATURE DISTRICT HEATING RESEARCH PROGRAM The IEA DHC Annex TS1 aims to identify holistic and innovative approaches to communal low temperature heat supply by using district heating. It is a framework that promotes the discussion of future but also existing heating networks with an international group of experts. The goal is to obtain a common development direction for the wide application of low temperature district heating systems in the near future. District cooling can also be integrated into the activities but is not the focus. The gathered research which is going to be collected within this Annex should contribute to establishing DH as a significant factor for the development of 100 % renewable energy based communal energy systems in practice. By connecting the demand side (community/building stock) and the generation side (different energy sources which are suitable to be fed in the DH grids), this technology provides benefits and challenges at various levels. The activities are strongly targeted at DH technologies and the economic boundary conditions of this field of technology.

MORE INFORMATION ABOUT THE PROGRAM: Up to date information about the participants and the progress of the research program is available on the web page: www.iea-dhc.org

Contact and coordinator of the program: Fraunhofer Institute for Wind Energy and Energy System Technology IWES Dr. Dietrich Schmidt Königstor 59 34119 Kassel Germany [email protected] Tel.: +49 561 804 1871 Fax.: +49 561 804 3187

The participating countries are: - Denmark - Finland - Germany - Norway - South Korea - United Kingdom

ISBN 3-89999-070-6 This brochure is a product of the IEA DHC Annex TS1 working group and has not been submitted for approval 2017.12 of the DHC executive committee. IEA DHC is there for not responsible for the contents of this publication.