District heating and cooling (DHC) offers an efficient and flexible, organizational and technical solution for the energy transition in the heating and cooling sector. It provides a broad platform and a major lever for the integration of all kinds of renewable energy sources (RES). Furthermore, it increases the overall efficiency of the energy system by enabling the use of combined heat and power and other hybrid technologies for coupling the energy sectors as well as the use of surplus heat from a variety of energy conversion or industrial processes. Due to its structure, DHC enables fast transition processes, including the introduction of high shares of RES.

The research of IEA DHC Annex TS5 has investigated and evaluated the state-of-the-art and best practices at international level for introducing RES into existing large urban DHC systems and thus transforming and decarbonizing their heat supply. The overall objective of Annex TS5 was to contribute to a faster and more cost-effective transformation and decarbonization of existing DHC systems in IEA DHC member countries.

Annex TS5 activities focussed on gathering and providing knowledge regarding RES technologies for DHC, their integration into DHC systems and overall DHC system transformation processes. The topics addressed and the results obtained by Annex TS5 shall be partial solutions and answers from the DHC R&D community regarding the DHC transformation challenges. These solutions should contribute to the abovementioned overall objective within the framework of this broad-based international IEA collaboration.

The Annex TS5 was a four-year international collaboration from 2021 to 2024 including international R&D and industry partners. The participating countries were Austria, Canada, China, Denmark, France, Germany, Italy, Irland, South Korea, Sweden, Switzerland and United Kingdom.

The ongoing transformation in European district heating systems fromthe usage of fossil-based technologies to non-fossil heat supplies issummarised by a collection of 70 possibilities linked to decarbonisation. These possibilities are exemplified by 284 implemented, planned, orproposed cases. The 70 possibilities for decarbonised district heatinginclude using heat, connecting customers, moving heat, storing heat, removing carbon dioxide, and supplying heat together with somefeatures for the entire value chain, to heat usage from heat generation orrecycling. This collection of 70 possibilities is neither complete nor doesit contain any recommendations for the possibilities or advocate forspecific possibilities.

The purpose of this project was to provide an extensive inventory ofdecarbonisation activities recently performed by district heating operators andother heat suppliers. These decarbonisation activities include the directsubstitution of heat obtained from the combustion of fossil fuels and indirectactions for obtaining more efficient district heating systems. These indirect actionsreduce costs and increase revenue, thereby improving the competitiveness ofdistrict heating. The time horizon, which is linked to the EU’s target for thereduction of greenhouse gas emissions by 55% compared to 1990 levels, is 2030. This inventory of early decarbonisation projects concerning district heatingsystems has revealed the following three key conclusions.

First, decarbonisation activities can be divided into substituting and supportingpossibilities. Substituting possibilities in heat supply include linear supply fromrenewables, heat recycling from processes that generate excess heat, and non-fossilways of meeting peak heat demands during very cold days. The linear heat supplyis based on geothermal heat, solar heat, and electricity supply. Heat recycling ispossible from various processes related to biorefineries, hydrogen supply, petrochemical plants, electricity distribution, district cooling, data centres, batteryfactories, food supply chains, and sewage waters. Heat storage can make heatdelivery more independent of heat supply and provide additional opportunities toreduce peak loads. Supporting possibilities mainly comprise activities forobtaining lower temperatures in heat distribution networks to increase profitabilitywhen using low-temperature heat sources. These activities are performed whenconnecting customers, moving heat, and using heat. Another supporting activity is the removal of biogenic carbon dioxide from the natural carbon cycle, although anappropriate international accounting system for its removal is still missing.

Second, the decarbonisation possibilities of district heating systems differ fromthose of traditional systems based on fossil fuels. The availability ofdecarbonisation possibilities for district heating depends on local conditions,whereas fossil fuels are transported from available global resources and are usedworldwide. Hereby, decarbonised district heating systems will not be as uniformas traditional systems based on fossil fuels. The local conditions lower the degrees of freedom for the implementation of substituting possibilities in existing buildingsand systems. Hence, it is important to adopt new methods for utilising the highestdegree of freedom possible in new buildings and systems.

Third, the common denominators for the 70 identified possibilities are degrees offreedom for decarbonisation, action plans for achieving lower heat distributiontemperatures, the use of heat pumps for upgrading low-temperature supplies tomeet high-temperature demands, smart digitalisation options, clear supplyresponsibilities, favourable institutional frameworks, and digital planning models. These seven common denominators are efficient tools for obtaining decarbonisedand more efficient district heating systems in the future. These redesigned and newsystems will be somewhat different than traditional systems, which have beenbased on a district heating technology that was originally elaborated for systemsbased on fossil fuels.

Den pågående omvandlingen av europeiska fjärrvärmesystem från användning av fossilbaserad teknik till icke-fossil värmeförsörjning sammanfattas med en utvald samling av 70 möjligheter kopplade till fossilfrihet. Dessa möjligheter exemplifieras med 284 genomförda, planerade eller föreslagna fall. De 70 möjligheterna för koldioxidfri fjärrvärme omfattar att använda värme, ansluta kunder, flytta värme, lagra värme, avskilja koldioxid och tillföra värme tillsammans med några aspekter för hela värdekedjan till värmeanvändning från värmeåtervinning eller värmegenerering. Uppsättningen av 70 möjligheter är varken komplett eller innehåller några rekommendationer för vilka möjligheter som bör användas. Syftet med detta projekt har varit att tillhandahålla en omfattande inventering av tidiga aktiviteter för att erhålla fossilfri fjärrvärme som nyligen utförts av fjärrvärmeföretag eller andra värmeaktörer. Dessa aktiviteter omfattar både direkt substitution av värme som tidigare erhållits från förbränning av fossila bränslen och stödjande indirekta åtgärder för att erhålla mer effektiva fjärrvärmesystem. Dessa stödjande åtgärder minskar kostnaderna eller ökar intäkterna som förbättrar fjärrvärmens konkurrenskraft. Tidshorisonten har varit 2030, kopplat till EU:s mål för minskning av växthusgasutsläppen med 55 % jämfört med 1990 års utsläpp. Denna inventering av tidiga projekt för fossilfri fjärrvärme har givit följande tre viktiga slutsatser. För det första, aktiviteter för fossilfri fjärrvärme kan delas in i ersättande och stödjande möjligheter. Ersättande möjligheter i värmeförsörjningen inkluderar linjär försörjning från förnybar energi, värmeåtervinning från processer som genererar restvärme och icke-fossila sätt att möta spetsbehov under mycket kalla dagar. Den linjära värmeförsörjningen baseras på geotermisk värme, solvärme och eltillförsel. Nya aktiviteter för värmeåtervinning är möjliga från många olika samhällsprocesser, såsom bioraffinaderier, vätgasförsörjning, petrokemiska anläggningar, eldistribution, fjärrkyla, datacenter, batterifabriker, livsmedelsförsörjning och avloppsvatten. Värmelager kan göra värmeleveransen mer oberoende av värmetillförseln, vilket också ger ytterligare möjligheter att minska spetsbelastningar. Stödjande möjligheter innehåller främst aktiviteter för att erhålla lägre temperaturer i värmedistributionsnät, vilket ökar lönsamheten vid användning av lågtempererade värmekällor. Dessa aktiviteter utförs när man använder värme, ansluter kunder och flyttar värme. En planerad stödaktivitet är också avskiljning av biogen koldioxid från det naturliga kolkretsloppet, även om ett lämpligt internationellt ersättningssystem för detta fortfarande saknas. För det andra, karaktären hos möjligheterna till fossilfritt skiljer sig från de traditionella erfarenheterna baserade på fossila bränslen. Tillgången på möjligheter till fossilfritt beror på lokala förhållanden, medan fossila bränslen transporterades från tillgängliga globala resurser, vilket gav full frihet att använda fossila bränslen var som helst i världen. Härigenom kommer fossilfria fjärrvärmesystem inte bli så 4likartade som traditionella fjärrvärmesystem var med fossila bränslen. De lokala förutsättningarna för fossilfri fjärrvärme ger något lägre frihetsgrader för implementering av ersättande möjligheter i befintliga byggnader eller system. Därför är det viktigt för framtiden att utnyttja den högre frihetsgrad som är möjlig i nya byggnader och system genom att använda nya metoder mm. För det tredje, de gemensamma nämnarna för de 70 identifierade möjligheterna är antal frihetsgrader för fossilfrihet, handlingsplaner för att erhålla lägre temperaturer i värmedistributionsnät, olika sätt att använda värmepumpar för att uppgradera låga framtemperaturer för att tillgodose högre temperaturbehov hos kunderna, möjliga smarta digitaliseringsalternativ, tydliga leveransansvar, gynnsamma institutionella ramar samt digitala planeringsverktyg. Dessa sju gemensamma nämnare är effektiva verktyg för att få mer effektiva fossilfria fjärrvärmesystem, eftersom den traditionella fjärrvärmetekniken en gång i tiden utformades för system baserade på användning av fossila bränslen. 

This report presents a review of methodologies and approaches used to assess renewable energy potentials and their integration into existing district heating systems. The main purpose is to identify, characterise, analyse, and describe known and suggested methodologies by which such integrations may be achieved, and to provide a coherent assembly and overview which may be of value and benefit for actors associated to district heating and cooling sectors around the world.

The presentation elaborates in part on a conceptual analysis by means of a matrix design, which introduces a set of dimensions and type categories to facilitate characterisation and classification, and in part on aggregate descriptions of concrete approaches accompanied by corresponding references and case study examples for further reading and detail. The input data for the analysis was assembled mainly from the Web of Science Core Collection, from which a world extract of almost seven thousand scientific publications was acquired for the period 1986 to 2023. From this full extract, a subset of 260 publications was selected for full text (manual) review by adaption and application of a systematic literature review filtering process.

Worldwide, district heating research (predominantly communicated by means of the “journal article” document type) has earned significantly increased interest during the last decade, despite an apparent peak in the total number of scientific publications in 2021. Still, review research specifically addressing methodologies for assessing the potential of renewable energy sources in district heating supply, as performed here, has been relatively limited. A key finding from this work is that dedicated research on the topic, while attracting interest globally with notable contributions from several countries in the Middle East and Asia, as well as from North America, is currently spearheaded by European Union (EU27) member states.

In line with growing global concerns regarding environmental and social issues, supply chaincorporations are improving their environmental and social performances. The optimal design of a closedloop supply network must conceive various aspects, leading to a multi-objective problem. This study developsa mixed-integer linear programming model to provide an integrated supply network with a particular focuson sustainability. Besides cost efficiency, energy consumption, and job creation are incorporated asadditional objective functions. This article uniquely introduces the training of supply chain employees as partof the developed model to address social responsibility. The Non-Dominated Sorting Genetic Algorithm-II(NSGA-II) and Multiple Objective Particle Swarm Optimization (MOPSO) are employed to solve the multiobjective problem. The numerical examples for cost and energy values are based on real data. The resultsdemonstrate the significant effect of returned product recovery on cost reduction in the network and changesin energy consumption at different levels. NSGA-II and MOPSO yield a set of optimal solutions that increasethe flexibility of decision-makers. Indeed, a set of Pareto solutions reveals a conflict between the objectivefunctions and allows the network to be highly effective in decision-making under different conditions andpolicies. 

This factsheet presents three examples of excess heat from, what is here labelled, “alternative” sources and processes which should be possible to recover in existing DH systems. The presentation is by no means exhaustive, since there are several other sources and processes emerging today as alternatives for such utilisation in contemporary networks. The overview is, however, indicative in relation to the expected increase in electrification of the future energy system in general, and the consequent increased opportunities in the sector coupling between future power, gas, and thermal infrastructures. The three presented alternative sources are excess heat from H2 production (and use), excess heat from battery manufacturing, and, more generally, excess heat from so called “Power-to-X" (PtX) technologies.

The possibility of the modal shift to public transport and active mobility while considering transport electrification and fuel efficiency improvement has yet to be adequately investigated. This paper explores transition pathways toward an environmentally sustainable road passenger transportation system in the province of British Columbia (BC), Canada. MESSAGE, as a bottom-up energy systems optimization model, is used to find the cost-optimal fuel and technology mix in the transport and power sector. Multiple scenarios mainly assess the influence of modal shift and electric vehicle (EV) diffusion on greenhouse gas emissions by 2050. Besides, the effects of scenarios on the power sector configuration are examined. The results show that BC would not achieve the 80% emissions reduction target in the Climate Change Accountability Act unless by a radical expansion of transport electrification. The target could be met by a minimum diffusion of 70% EVs in the total car stock as well as 35% public transport contribution in total passenger kilometers. The findings also indicate that fully electrified light-duty vehicles coupled with active transport would lead to almost a zero-emission level. Nevertheless, 100% electrification would impose an extra 5.6 TWh burden on the power supply system relative to the business-as-usual scenario. © 2023 The Authors. Published by Elsevier Ltd

This report presents the updated and final results from the work performed in Task 1.2 of the ReUseHeat project to assess the accessible EU28 urban waste heat recovery potential from seven unconventional waste heat sources: data centres, metro stations, food production facilities, food retail stores, residential sector buildings, service sector buildings, and waste water treatment plants. The report focusses on recent data and model updates for the EU28 in total (EU27 plus the United Kingdom), as well as for the project demonstration sites, while less focus is directed towards the original methods and approaches developed for these models; all of which have been described in previous accounts. In terms of data updates, monitoring data from demonstration site operations and public responses to our online project questionnaire on real-world urban waste heat recovery initiatives, are presented and evaluated in overview summary. Regarding model updates, the assessments of urban waste heat potentials from data centres and metro stations have been refreshed by use of new underlying input data, by the configuration of existing and the addition of new model parameters, as well as by reference to later year energy statistics. For the modelling of the total EU28 potential, utilising a dataset for the geographical representation of current urban district heating areas more detailed than the previous one, renders by spatial analytics, under the same “inside or within 2 kilometres of urban district heating areas” default setting as used before, an updated and more accurate assessment of the distances and the vicinity by which low-grade urban waste heat sources are located relative current demand locations. We maintain in this report also our application of the two concepts “available” waste heat and “accessible” waste heat, which, in combination with spatial constraints, are used to distinguish between resource potentials and utilisation potentials. For the total count of activities elaborated in this update (70,862 unique point-source activities compared to the original 70,771), the total available waste heat potential is assessed at some 1849 petajoule per year (~514 terawatt-hours), compared to the original 1842 petajoule per year. At the default spatial constraint setting, the final available waste heat potential is estimated at ~800 petajoule per year (~222 terawatt-hours) from a thus reduced subset of 22,756 unique point-source locations (960 petajoule per year from 27,703 unique facilities in the original), which here corresponds to a final accessible EU28 waste heat utilisation potential anticipated at 1173 petajoule (~326 terawatt-hours) annually (previous assessment at 1410 petajoule annually). For improved dissemination and exploitation of project results, a new web map; the European Waste Heat Map, has been developed and made available at the ReUseHeat project web page where point source data from this work may be viewed and shared. © The Authors.

This report is the second out of three consecutive accounts of a coherent methodological framework developed in the EU Horizon 2020 project Decarb City Pipes 2050 to define heating and cooling decarbonisation design approaches for cities based on urban typologies. The first and third accounts are, respectively, the deliverable reports D2.5 (Decarbonisation design-approaches based on urban typologies) and D2.7 (Recommendations for cities' H/C supplies & demands in 2050). The framework has been developed by identifying possible thematic synergies between the objectives of the concerned deliverables, by combining different method elements, and by organising a collaborative work strategy among the involved project partners. This report presents, in overview and detail, the input data synonymously used within the framework for the determination of urban typologies, for the modelling and mapping of heating and cooling outlooks for 2050, for the quantification of a cross-city synthesis, as well as for formulating recommendations for cities´ heating and cooling demands and supplies in 2050. The study focusses on the urban areas of seven European project cities (Bilbao (ES), Bratislava (SK), Dublin (IE), Munich (DE), Rotterdam (NL), Vienna (AT), Winterthur (CH)), for which EU-scoped, publicly available input data, to the extent possible, has been gathered according to ten structuring criteria parameters. Heating and cooling outlooks for 2050 are established for each project city based on the used input data and illustrated in the form of tables, graphs, and maps, and constitute the first element of a quantitative cross-city synthesis (city comparison). The second element (city ranking) is facilitated by application of a multi-criteria decision model, which here consists of combining the Analytical Hierarchy Process method (AHP) and the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS).

This report identifies different typology-based approaches and methods for decarbonising the energy sector of cities. Respectively, typologies were evaluated, and design approaches were developed. In a first step, already existing typologies were evaluated, including a study by the Technical University of Darmstadt and examples from the City of Vienna. In a next step, conceivable structuring criteria and decarbonisation approaches from existing work within the DCP project were identified and summarised. These include structuring criteria such as heat demand density, renewable energy sources or types of refurbishment activities. On this basis, a new typology was developed. Five highly weighted criteria could be derived from the results of the expert survey, including structural energy efficiency, coverage of district heating, potential for renewable sources, potential for waste heat and heat demand density. These criteria formed the basis for the development of the novel typology. The first typology represents areas with high compatibility with highly weighted criteria, the third typology represents areas with comparably low compatibility, while the second typology is associated in between. Based on the developed typology, six design approaches were presented in this report. One short-term and one long-term approach for each typology include recommendations as well as concrete measures for strategic decision-making.