District heating and cooling systems can aid in decarbonisation and the provision of efficient heating and cooling in Europe. However, whereas these systems have achieved high penetration rates in colder climates of Northern, Central and Eastern Europe, they remain marginal in milder climates of Southern Europe. In terms of network design, district heating and cooling systems can be configured in different ways. In so-called warm networks, the required temperature for all the consumers is attained city-wide, and in so-called cold systems, the necessary temperature is achieved at the consumers' premises by ancillary equipment. The most cost-effective heating and cooling solution for urban areas requires investigation. This research models and compares cold and warm district energy systems with other heating and cooling solutions through a comprehensive case study executed in the city of Bilbao, Spain. The city is characterised by a mild climate and a high population density which is characteristic of many Southern European cities. The results show that district energy systems are economically advantageous compared to other low-carbon solutions, such as air-source heat pumps. However, these systems are not able to outcompete natural gas under current cost and taxation levels. Warm networks provide a cheaper source of heat compared to cold networks, but both network types lead to similar expenditures for combined heating and cooling supply. This paper, presents the study context and its results, and is complemented by an exhaustive detailed methodology document and a separate supplementary material repository. © 2024 The Authors

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 paper is the second of three accounts which describes a Swedish study aiming to derive a first order assessment of the national potential for large-scale solar thermal heat production with pit thermal energy storage's (PTES) connected to existing district heating systems (DHS). Whereas the first paper presented project objectives, outset parameters, and an updated Swedish district heating database – and the third is planned to report on the final project results and conclusions – this paper focuses on the assembled study data and the associated selection criteria applied to these data categories under the objective to distinguish suitable (and non-suitable) land areas within cost-efficient heat transmission distances from the existing DHS. The approach centres around a principal spatial analysis with superposition of study data and elimination of non-suitable land areas according to the used selections criteria but also entails a wide periphery of related activities, such as literature reviews, gathering of technology preferences, meetings with sector experts, data management etc. Apart from technical specifications for solar heat production and seasonal storage, key data categories for the spatial analysis consist of geological data (e.g. soil types, soil depth, bedrock etc.), hydrological data (lakes, rivers, wells, soil moisture, ground water levels etc.), geographical data (elevation, built-up areas, administrative units etc.), and thematic data (energy statistics, building heat demands, district heat deliveries etc.). Selection criteria for the relevant data categories have been defined iteratively during e.g. expert consultancy, for example minimum soil depth, preferred soil types, maximum feasible transmission distance to existing DHS etc. By application of the selection criteria, raw input data are converted to processed data extracts to be used in the final analysis. Study data categories are illustrated and summarised (raw and processed) together with a listing and discussion of the used selection criteria.

This paper presents a novel approach to modeling the gradual reduction in heat demand and the evolving expansion of district heating (DH) grids for assessing the DH potential in EU member states (MS). It introduces new methodological elements for modeling the impact of connection rates below 100% on heat distribution costs in both dense and sparse areas. The projected heat demand in 2050 is derived from a decarbonization scenario published by the EU, which would lead to a reduction in demand from 3128 TWh in 2020 to 1709 TWh by 2050. The proposed approach yields information on economic DH areas, DH potential, and average heat distribution costs. The results confirm the need to expand DH grids to maintain supply levels in view of decreasing heat demand. The proportion of DH potential from the total demand in the EU-27 rises from 15% in 2020 to 31% in 2050. The analysis of DH areas shows that 39% of the DH potential is in areas with heat distribution costs above 35 EUR/MWh, but most MS have average heat distribution costs between 28 and 32 EUR/MWh. The study reveals that over 40% of the EU's heat demand is in regions with high potential for implementing DH.  © 2023 The Author(s)

Sweden was among the first countries to install solar thermal plants for district heating (DH) as early as in 1970s. However, in recent years, the focus on solar DH installations has shifted primarily to Denmark and Germany, with only one recent installation reported in Sweden. Nonetheless, due to changes in the overall heating market, the use of large-scale storage (both with and without solar heat) is becoming increasingly important. Despite significant advancements in adopting DH systems, the combination of solar DH with PTES is not well studied from Swedish context. The economic and geological prerequisites for the deployment of PTES remain largely unexplored. This paper explores the integration of large-scale solar thermal systems into DH networks in Sweden, particularly highlighting the feasibility and potential of pit thermal energy storage (PTES) systems. Through findings from a national project, this paper assesses the techno-economic-geological viability of PTES alongside solar thermal collectors, providing insights into the project’s methodological approach and initial findings.

This dataset consists of two seperate geopackages, which are both digitisations of isotherms in the 1000 meters and 2000 meters below ground maps, displayed in plates 2 and 3 of the 2002 Atlas of geothermal resources in Europe.

The solution of the undergoing climate and energy crises requires a radical transformation of the energy system, in which sustainability, no carbon emissions and energy efficiency ought to play a paramount role. 

This revolution should extend to all areas of the energy system, including the space heating and cooling sector, which accounts for a third of the European final energy demand and, in the European continent, it is still mostly supplied by fossil fuels.

District heating is a simple but powerful technology that can contribute to tackle this challenge. As a network infrastructure, it is characterised by the flexibility of the heat production, allowing the incorporation of a wide range of heat sources over time. Furthermore, it enables the recycling of heat that would otherwise be wasted and the use of local heat sources in a more cost-effective manner. Moreover, its coupling with the electricity sector can facilitate the increase of intermittent electric renewable energy sources. 

Nevertheless, at the moment, district heating only covers a tenth of the European space heating and cooling needs, albeit with significant differences among countries. In addition, the development of new district heating networks is capital intensive and can only be justified in those areas where the concentration of the heat demand is sufficiently high to deliver a lower cost to society than an individual alternative. 

Therefore, it is crucial to assess the potential of district heating and to identify the target areas for in-depth investigations. This necessity demands easy and straightforward tools, which can provide a first order approximation of the construction cost of new networks. 

One of these tools is the capital cost model developed by Persson & Werner, which is based on, among others, the effective width parameter. This is an indicator of the required trench length in an area supplied by district heating and has been related to the building density. 

This work has contributed to the understanding of the effective width parameter in a wide range of building densities, taking advantage of one of the largest district heating networks in Denmark, and provided new equations that relate it to various indicators of building density. 

Furthermore, the average pipe diameter of district heating pipes has been linked to another crucial parameter in district heating technology, the linear heat density, extending prior work conducted by Persson and Werner. 

In addition, Persson and Werner's model and the newly found empirical expressions have been validated in various Danish district heating networks, showing that the model provides relatively accurate results on an aggregate level and large areas but dismally fails in low-extension areas. 

Finally, the model has been applied to the European Union showing that district heating networks could potentially supply a third of the heat demand in 2050.

Lösningen av de pågående klimat- och energikriserna kräver en radikal omvandling av energisystemet, där hållbarhet, inga koldioxidutsläpp och energieffektivitet bör spela en avgörande roll.

Denna revolution bör sträcka sig till alla delar av energisystemet, inklusive sektorn för uppvärmning och kylning av byggnader, som står för en tredjedel av Europas slutliga energibehov och på den europeiska kontinenten fortfarande till största delen försörjs av fossila bränslen.

Fjärrvärme är en enkel men kraftfull teknik som kan bidra till denna utmaning. Som nätverksinfrastruktur kännetecknas den av flexibilitet i värmeproduktionen, vilket möjliggör inkorporering av ett brett utbud av värmekällor över tid. Dessutom möjliggör det återvinning av värme som annars skulle gå till spillo och användning av lokala värmekällor på ett mer kostnadseffektivt sätt. Dessutom kan dess koppling till elsektorn underlätta ökningen av intermittenta elektriska förnybara energikällor.

Detta till trots täcker fjärrvärme för närvarande bara en tiondel av det europeiska behovet av uppvärmning och kylning av byggnader, om än med betydande skillnader mellan länderna. Utbyggnaden av nya fjärrvärmenät är dessutom kapitalkrävande och kan endast motiveras i de områden där koncentrationen av värmebehovet är tillräckligt hög för att ge en lägre kostnad för samhället än ett individuellt alternativ.

Därför är det avgörande att bedöma potentialen för fjärrvärme och att identifiera målområdena för fördjupade utredningar. Denna nödvändighet kräver enkla och okomplicerade verktyg, som kan ge en första ordningens uppskattning av investeringskostnader för nya nätverk.

Ett av dessa verktyg är kapitalkostnadsmodellen utvecklad av Persson & Werner, som bygger på bland annat parametern effektiv bredd. Detta är en indikator på den erforderliga dikeslängden i ett område som försörjs av fjärrvärme och har relaterats till byggnadstätheten.

Detta arbete har bidragit till förståelsen av effektiv bredd-parametern i ett vitt spektrum av byggnadstätheter, vars studium drar fördel av ett av de största fjärrvärmenäten i Danmark, och har gett nya ekvationer som relaterar den till olika indikatorer på byggnadstäthet.

Vidare har den genomsnittliga rördiametern för fjärrvärmerör kopplats till en annan avgörande parameter inom fjärrvärmetekniken, den linjära värmedensiteten, vilket utökar tidigare arbete utfört av Persson och Werner.

Dessutom har Persson och Werners modell och de nyfunna empiriska uttrycken validerats i olika danska fjärrvärmenät, vilket visar att modellen ger relativt exakta resultat på aggregerad nivå och stora ytor men mindre så i lågutbyggnadsområden.

Slutligen har modellen tillämpats på EU som visar att fjärrvärmenät potentiellt kan tillgodose en tredjedel av värmebehovet år 2050.

With the adoption of the EU Climate Law in 2021, the EU has set itself a binding target to achieve climate neutrality by 2050 and to reduce greenhouse gas emissions by 55 percent compared to 1990 levels by 2030. To support the increased ambition, the EU Commission adopted proposals for revising the key directives and regulations addressing energy efficiency, renewable energies and greenhouse gas emissions in the Fit for 55 package.

The heating and cooling (H&C) sector plays a key role for reaching the EU energy and climate targets. H&C accounts for about 50 percent of the final energy consumption in the EU, and the sector is largely based on fossil fuels. In 2021, the share of renewable energies in H&C reached 23%. The decarbonisation of heating and cooling is addressed across several directives and regulations at EU level.

The aim of this study is to support the analytical basis for the development and implementation of policies to ensure a seamless pathway to the full decarbonisation of the heating and cooling sector by 2050 in buildings and industry.

District heating is one of the technologies that can contribute to the decarbonisation of the European heat sector. Nonetheless, these infrastructures only deliver about a tenth of the heat demands in the continent. Therefore, it is essential to assess the expansion potential of these systems and to identify which areas should be target for further investigations, which calls for easy-to-use and straightforward methods such as Persson & Werner's network capital cost model. Pivotal parameters of the model are the effective width, a metric of trench length by land area, alongside the average pipe diameter and the linear heat density. This study has carried out an in-depth analysis of these crucial parameters with respect to both distribution and service pipes in a large Danish district heating network, which has allowed to explore the behaviour of effective width in a broad range of building densities and derive new equations for both effective width and average pipe diameter. The model has subsequently been validated in another large network in Denmark and several minor districts in the same country, showing the accuracy of the model on an aggregated level. © 2023 Elsevier Ltd.