New generation district heating and cooling networks are based on the potential for integrating renewable energy sources and waste heat from various processes that are unexploited in conventional networks. This benefit minimizes primary energy use and emissions, enabling the provision of climate-neutral district heating and cooling. The option also provides social and health co-benefits for urban inhabitants while increasing resilience and energy security through supporting the elimination of fossil fuels. Economic co-benefits are based on innovation, including those for flexible operation schemes that can allow the system to utilise any excess electricity from fluctuating renewables based on solar and wind energy.  

Social Co-Benefits 

• Increase access to clean, affordable, and secure energy: Energy security issues arise from natural gas use in buildings for heating with increasing risks for energy poverty, especially with increases in prices. New generation district heating and cooling networks that can utilise renewable energy sources and waste heat can become a top priority for increasing access to clean, affordable and secure energy for all, delivering essential social co-benefits.  

• Security/protection for poor/vulnerable/marginalised populations: New generation district heating and cooling networks can be coupled with policies for social housing for vulnerable populations, addressing energy poverty. 

Health 

• Improved air quality: In Europe, 13% of settlements are below WHO air quality guidelines with other settlements having various performances in their interim targets for annual mean particulate matter [43]. The sources of air pollution are mixed, including buildings, transport, and industry. New generation district heating and cooling networks can contribute to improvements in air quality through replacing fossil fuel use for thermal energy.  

Economy 

• Business/technological innovation: New generation district heating and cooling networks involve opportunities for innovation in technologies that enable even more efficient networks, including in heat pumps and their integration. Collaborations between R&D and businesses can support these innovations with new job creation. In addition, substations industrialisation and controls require more advances to reduce initial and operational costs. 

Figure 3 provides a visual representation of similar co-benefits based on improved air quality and benefits for the local economy. There are also other societal benefits, such as effective climate mitigation. When large-scale heat pumps are operated flexibly, this supports the penetration of renewable energy by providing demand flexibility in the energy system.   

Figure 3. Visual representation of the possible co-benefits of heat pump driven district heating networks (from [44]) 

• Urban form, layout and climate: The concentration of thermal energy demands in urban areas is an enabler of new generation district heating and cooling networks. As indicated, 88% of the total population lives in areas with heat densities greater than 20 TJ/km2 and 78% of the total heat demand in buildings originate from dense urban areas [32]. In addition, the heat distribution cost of district heating reduces with urban density [32]. The diverse options for district heating and cooling networks need to be considered in the climatic context of the urban area. Overall, neighbourhood and district level energy planning is a prerequisite for the implementation of new generation district heating and cooling networks, especially given the aim of seeking synergies between heat sources and sinks that are available within the urban area [6]. More mature cities with established urban form and layout may require greater effort to implement new generation district heating and cooling networks. At the same time, existing infrastructure may be available for retrofitting and there may be emerging districts that can leapfrog directly into this technology. Better urban planning that leads to more compact and walkable urban areas can provide areas where district heating and cooling networks flourish for climate-neutrality while providing co-benefits, including better air quality [45]. 

• Technical aspects/infrastructure: If present, switching from 3G to the new generation district heating and cooling networks requires a design approach that re-considers the operation of heat pumps, thermal capacity, seasonal thermal energy storage and their dynamic interactions [29]. Existing city and local R&I infrastructure can be valuable assets and enablers in this process when well-orchestrated. Enabling digital and data infrastructures can support new business models for new generation district heating and cooling networks that support urban climate-neutrality. In networks where the network temperature is allowed to be free-floating, controls for differential pressure and supply temperature controls as in conventional district heating and cooling networks are not necessary. Advanced controls for the new generation network can involve digital support, including agent-based control for coordination [29]. 

• Policy and regulatory/legal framework:  

• Political will at local, regional and national levels, fuel switching to allow district heating and cooling to serve buildings, and better urban energy planning and zoning based on municipal heat plans are the most important factors to allow a faster heat transition in cities [46]. In the context of the 40 analysed cases of 5G district heating and cooling network examples in Europe, most of the cases are found to have arisen from demands within the communities and municipalities to become independent from fossil fuels and increase energy security [6]. Such motivations are closely aligned with the aim of climate-neutral cities. In addition, the collective will of local authorities, building investors, and local communities as a whole for switching to sustainable heating and cooling solutions is identified as a key enabler of this possible option. 

• In the scope of regulatory measures that can become enablers, at the local level, Baden-Württemberg has made municipal heat planning for CO2-neutral heat supply compulsory [47]. Making connections to the district heating and cooling networks in zoned areas mandatory can be an effective regulatory option. Other examples also emphasize the role of municipal regulations for having buildings be connected to the local district heating and cooling network that can be compatible with climate-neutrality aims. A municipal regulation for connecting to the 5G district heating and cooling network takes place in Bulle, Switzerland and active cooling exploiting chillers in residential buildings are also not allowed in the country by law [6]. 

• Economic and social context: Based on a stakeholder survey, there is growing citizen awareness that district heating and cooling networks provide a key infrastructure for urban areas and need to be transformed into low-temperature networks with high shares of renewable and waste heat to support integrated renewable energy systems [46]. 

• Funding and financing: Access to EU/public funding is crucial to support new generation district heating and cooling networks. R&D projects and large-scale innovation procurement will support upscaling this option in Mission Cities. 

• Project governance and implementation modalities:  

• New business models and empowerment of prosumers, the mobilisation of collective knowledge and skills, public-private partnerships and experimentation/testing needs are among top priorities as enablers. These include capacity building in the local administration for urban energy planning that is combined with financial support, including grants and even equity financing for projects [46]. An overall opportunity is better urban energy planning and network optimisation that can become the focus of collaborations for implementing new generation district heating and cooling networks based on renewable and waste energy sources. 

• It is necessary for citizens to be empowered in the decision-making process around heating systems, for example through community representatives on heat supplier boardshttps://euc-word-edit.officeapps.live.com/we/wordeditorframe.aspx?ui=en-GB&rs=en-IE&wopisrc=https://eceuropaeu.sharepoint.com/teams/GRP-CNC/_vti_bin/wopi.ashx/files/848e609a11a14d0e8c174427828cd272&wdenableroaming=1&mscc=1&hid=594379A0-8093-5000-98EF-CBBE87CE516E&wdorigin=ItemsView&wdhostclicktime=1668628922522&jsapi=1&jsapiver=v1&newsession=1&corrid=8e947aaa-a9e0-4b85-93bf-b2a606d1c9c0&usid=8e947aaa-a9e0-4b85-93bf-b2a606d1c9c0&sftc=1&cac=1&mtf=1&sfp=1&instantedit=1&wopicomplete=1&wdredirectionreason=Unified_SingleFlush&rct=Medium&ctp=LeastProtected#_ftn1 [53]. Where district heating networks are operated by social housing organisations there are potentially more opportunities for direct resident engagement in decision-making [53]. Co-creation strategies for implementing low-carbon heating should be prioritised in order to create socially sustainable strategies. These strategies will then need to be embedded into policy development around heating systems.  

• A dedicated citizen engagement department in a municipality could advance the action behind initiating and managing a citizen engagement process in sustainable heating. Debates in this field should also focus on who benefits from these new technologies, if 3G/5G entails making use of renewable resources. 

Overall, low-temperature district heating is a cost-competitive heating option and in different contexts, can be the option with the lowest levelised cost of heat. For example, the levelised cost of heat for low-temperature district heating systems is estimated to be 65 MW EUR/MWh in Spain and 74 EUR/MWh in Germany whereas those for gas boilers that are the main competitors in these countries were higher at about 80-83 EUR/MWh [48]. The business models of district heating companies can affect the cost structure of connecting to the network with more opportunity for diffusing good practices. In this context, some of the recent EU projects have been developing cooperation structures and business models, including ReUseHeat and the Designing Smart and Resilient Cities for All (RUGGEDISED) in Horizon 2020. 5G district heating and cooling networks can be more expensive while the integration of inexpensive waste heat can provide advantages [2]. At the same time, both the costs and mitigation potential are context specific, also depending on enablers and barriers.  

In comparison to the strengths and opportunities that are important for understanding the pre-conditions and enabling conditions as indicated above, Table 3 also summarizes the weaknesses and threats of new generation district heating and cooling networks with a specific focus on 5G networks. Most of the weaknesses and threats relate to technical aspects. 

Table 3. Strengths, Weaknesses, Opportunities and Threats of 5G District Heating and Cooling Networks (adapted from [6]) 

• Urban form, layout and climate: Established urban form and layout may require greater effort to implement new generation district heating and cooling networks and important verifications are required for any existing networks. Any natural gas boiler infrastructure at the building level can become obsolete while addressing this carbon lock-in.   

• Technical aspects/infrastructure: As indicated in Table 3, capital expenditures for substations, requirements for domestic hot water tank installations, the diameter of the pipelines in the distribution networks, higher pumping costs per unit of energy, and electricity costs for the heat pumps can take place among the features that require additional attention. Depending on the choices in the new generation district heating and cooling network, all or only some of these features may be relevant. Seasonal thermal energy storage will require appropriate geophysical space(s).  

• Economic and social context:  

• The investment cost can be the main barrier for new generation district heating and cooling networks. In contrast, new business models for the network operator and consumer engagement can be designed to overcome this barrier. New business models that involve the supply and maintenance of the user substation are also being related to Energy-as-a-Service (EaaS) business models [6]. Lower price structures that provide alternatives to "no-more-than-otherwise" principle for new generation district heating and cooling networks based on renewable energy and waste heat are emerging [6]. Rather than being a barrier, these alternatives can also boost customer confidence in the option that does not have to be referenced to natural gas prices. 

• Citizens not having any voice or contribution in decision making or even co-ownership can make citizens less aware or appreciative of the benefits that new generation district heating and cooling networks can provide, possibly resulting in constraints or even barriers for implementation. In contrast, citizens’ participation in decision making processes can be even more important than any co-ownership frameworks, if considered [6]. As a result, citizen engagement is important for new generation district heating and cooling networks. 

• Policy and regulatory/legal framework:  

• Heat marketability and management issues to enable a shift from traditional distribution and trading structures to more interactive structures with multiple actors, including prosumers and the providers of waste heat, can remain to be addressed if new business models are absent outside of the pilot cases. In addition, the absence of municipal regulations for connecting to the district heating and cooling network can leave an underutilized potential where innovations in the policy domain can help support this technology. 

• Funding and financing: Lack of funding and financing can be prevalent barriers for multiple options, including new generation district heating and cooling networks. Related risks can be minimised with innovative financing models. 

• Project governance and implementation modalities:  

• New generation district heating and cooling networks require coordinated action on the supply and demand sides, including with urban planning. Large-scale projects can involve greater complexity while phased approaches may be appropriate within project governance and delivery of results.      

• New generation district heating and cooling networks also require expertise in conducting citizen engagement processes to stimulate citizens’ interest in the implementation of sustainable heating solutions and to enable citizens to make informed decisions [54,55]. 

• Aspects related to the operation of the network: New generation district heating and cooling networks are based on synergies between local sources of thermal energy, end-users, and their interaction. Alongside synergies, there can be relatively higher risks in connecting and managing multiple producers. To avoid potential adverse impacts during operation, more elaborated contracts for heating and cooling plus services can be useful.   

• Technical aspects related to network components: After implementation and during the operational phase of low-temperature district heating and cooling networks, fouling in heat exchangers can take place over time. This can decrease heat exchanger efficiency, causing return temperatures in the network to be higher than expected [52]. In contrast, return temperatures also play a key role in allowing low-temperature networks to reach their full potential. Maintenance of relevant components can ensure that highest efficiencies possible are achieved. 

• Behavioural aspects related to user preferences: Indoor set-point temperatures at the side of end-users are often determined by preferences based on behavioural aspects rather than by design [52]. This can affect the complete impacts expected from the network, particularly energy savings, and can be best addressed when the technological infrastructure is combined with awareness and nudges to support energy-conscious lifestyles. 

• Other operational aspects that require attention: Operational costs are context specific – a new generation district heating and cooling network that is implemented in one location will not have exactly the same operational costs as that in another location. Yet there are measures that can be taken to reduce these costs, such as reducing the temperature demands for upgrading the circulating thermal energy through booster heat pumps. This can be useful in reducing higher electricity costs in substations compared to conventional networks.  

Literature 
 

The first reference provides a comparison of 4G a nd 5G networks followed by other references in the solution factsheet: 

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Other Useful Resources 

Smart Cities Marketplace < https://smart-cities-marketplace.ec.europa.eu/>  

Quantified impacts that are available from case studies are context specific, often depending on the existing status quo, alternative solutions, and the scale of implementation. As a result, the impacts depend on a number of factors, including the energy sources that are being replaced with the new generation district heating and cooling network, the number of buildings that are connected to the network, the utilisation of renewable energy and any sources of waste heat, the temporality of the waste heat sources, the use of electricity for heat pumps, demand flexibility, the coefficient of performance of the heat pumps, and ultimately, the coverage of the network within the thermal energy needs of the urban area. As a solution that can connect multiple measures on the supply and demand sides, new generation district heating and cooling networks are typically integrated with multiple other measures (see the last section on “Typically Integrated With”) and the impacts can be realised together with the collective contributions of these solutions. With this consideration, Table 2 provides exemplary impacts for energy savings and renewables in the context of different cases.  

Table 2. Exemplary impacts for energy savings and renewable energy compiled from the Smart Cities Marketplace  

It will be important for climate-neutral cities to plan for similar impacts, including primary energy savings, renewable energy generation, and the amount of energy generated from low-grade heat sources that is triggered by the project.  

Planning 

• Integrated land use and urban planning: Is critical to ensure that new generation district heating and cooling networks benefit from the concentration of population, heat demand densities, and sources in urban areas. 

• Institutional cooperation: Enabling new generation district heating and cooling networks inherently requires institutional cooperation for integrated urban planning, including urban energy planning. In addition, institutional cooperation is important to support the creation of a skilled workforce, producing metrics and benchmarks to support performance, and incentivising early stage design exploration, including users and smaller pipe sizing [11]. These aspects are also seen essential for diffusing new generation district heating and cooling networks.  

• Informative/ Awareness raising instruments such as co-creation labs to engage citizens upfront before decisions are taken. 

Educational/capacity building 

• Energy communities: New generation district heating and cooling networks can be important enablers of energy communities. Greater awareness and capacity building is essential for implementation, especially if lacking. Social awareness on energy communities based on semantic network analysis and text mining from online sources do indicate that there can be important gaps in communicating relevant concepts in more laggard contexts [49]. 

Financial/fiscal 

• Incentives/disincentives: Incentives for actors that participate in supplying waste heat to a new generation district heating and cooling network can be provided with the framework of new business models. Disincentives can be relevant for actors that are not connected to the network or those with technologies with carbon lock-in. 

• Public Private Partnerships: Are often relevant for new generation district heating and cooling networks that also accept the integration of waste heat into the network from various sources, including data centers as well as supermarkets. For example, open district heating schemes [50] have involved public private partnerships.   

Regulatory 

• Building codes/standards: On the demand side, efficient buildings that are supported by appropriate building codes and standards will require less thermal energy from district heating and cooling networks. There can be a balance between saving and supplying heat depending on context according to energy planning [51]. Overall, end users with good levels of thermal efficiency will support more viable and economical networks [11]. In addition, important reductions in heat distribution losses take place by lowering the supply temperature in the network, e.g. by up to 25% from 80°C to 55°C based on the transition to a low-temperature district heating and cooling network in Trondheim that involved building areas consisting of passive houses and low-energy buildings [52]. 

• Land use planning regulation: Zoning can be a very crucial instrument for district heating and cooling networks in general and new generation networks in particular. Regulations can be utilised to require buildings within district heating and cooling network zones to be connected to the network, increasing the realised mitigation potential. 

Technical 

• Scenario-based analysis (mobility & energy - one model): New generation district heating and cooling networks can provide an important asset for the energy transition. Scenario-based analyses can support energy planning. 

• Geospatial information (incl. Satellite): Tools that are based on geospatial information are highly relevant to support urban energy planning within integrated urban planning. There are available geospatial information, such as for 52,000+ heat supply districts across Europe based on the Pan-European Thermal Atlas (Peta) [29].  

Projects/Case Study Examples 

 
Over 60 projects on lower temperature district heating and cooling are overviewed in [5]. In addition, a total of 40 cases in Europe, mostly pilot projects, are surveyed in [6] with a focus on 5G district heating and cooling networks. The examples that are provided below involve overarching information that is representative of the main developments in this area. Case studies relating to communities with low-grade or low-exergy demands were compared in the context of Annex 64 [30].  

 
Heat Roadmap Europe (HRE) and sEEnergies: These projects developed data, tools, and methods to quantify the impact of more efficient strategies for the heating sector on the demand and supply sides, targeting policymakers, industry, and researchers at local, national, and EU levels. The Pan-European Thermal Atlas (Peta) that quantifies heat demand densities has been guiding the heating sector, providing easily accessible spatial information, currently through Peta version 5.2, also see Figure 2 [29]. This atlas can be used to support heat supply strategies in more than 52,000 heat supply districts across Europe having residential and service sector heat demand densities at 20 TJ/km2 and above [31]. In Europe, 88% of the total population lives in areas with heat densities greater than 20 TJ/km2 and 78% of the total heat demand in buildings originate from dense urban areas [32]. Based on the results, district heating distribution network efficiencies are found to range from 82% in areas with heat densities of 50 TJ/km2 to 98% in modern networks in highly dense urban centres [31].      
 
REnewable Low TEmperature District (RELaTED): Developed an innovative concept of ultra-low temperature district heating networks [33]. The concept reduced the operation temperature with heat delivery at 40-45°C, integrated low-grade industrial heat sources, allowed larger shares of renewable energy sources and distributed heat sources, including reject heat from cooling equipment, and supported heat load reductions in buildings toward Near Zero Energy Buildings. One of the enabling technologies has been district heating-connected reversible heat pumps to integrate temperature levels in buildings to ultra-low temperature districts, also allowing for the reuse of reject heat from cooling applications [34], and a triple function substation for prosumers [35].  Demonstration sites: Tartu, Vinge, Iurreta, and Belgrade. 

COOL DH: Demonstrates high efficient district heating networks and solutions for demand, distribution and supply. For demand, this includes local integration of renewable energy sources at the substation level, such as photovoltaic-thermal panels that can supplement the district heating network. It also includes solutions for avoiding the risk of Legionella in domestic hot water. In aspects of distribution, hydraulic optimisation of the connection lines minimizes energy losses while also lowering the pumping energy and operation pressure. This includes pipe insulation, pipe technology/sizing as well as network length optimisations that can minimize heat losses to about 10%. On the supply side, seasonal energy storage is also demonstrated (e.g. heat storage of 70.000 m³ in Høje Taastrup) [36]. Demonstration sites: Lund and Høje-Taastrup  

 
Smart and Inclusive Solutions for a Better Life in Urban Districts (SMARTERTogether): The project involved next generation district heating and renewable energy supply for low energy districts with about 14.6 MW of newly installed renewable capacity in the districts [37]. Lighthouse cities and demonstration sites: Lyon, Munich, and Vienna. 
 

Fifth generation, low temperature, high exergy district heating and cooling networks (FLEXYNETS): Uses reversible heat pumps to exchange heat between connected end-users and a district heating and cooling network at ambient or neutral temperature levels at about 15-20°C [38]. In traditional layouts, substations are placed mostly at each building that is connected to the network and are owned either by the district heating company or by the customer. In contrast, substations with reversible heat pumps can have more interactions with the thermal network. The distributed, reversible heat pumps at user substations also have high coefficients of performance (COP) due to the operating temperatures [39]. 
 

ATELIER: Focuses on innovative, very low temperature district heating and cooling systems for positive energy districts with mixed residential and commercial uses. As a key horizontal aspect during the process, citizens are placed at the centre of the energy transition with ~9,000 residents, local initiatives as well as energy communities being included in the decision-making phases and related activities [40]. The Lighthouse cities are Amsterdam and Bilbao with follower cities of Bratislava, Budapest, Copenhagen, Krakow, Matosinhos and Riga that are interacting in the same smart cities project. 
   
Among the many other examples as overviewed in [5], MAKING-CITY is another example that formulates integrated strategies for urban energy system transformation. Within these strategies, district heating and cooling networks are supporting the energy exchange in positive energy districts [41]. Notably, it is important to emphasize the role of these networks in integrating the supply and demand sides, including renewable energy, urban planning, and electrification.   

Cross-Cutting Informative Websites/Tools 

Pan-European Thermal Atlas (Peta) <https://www.seenergies.eu/peta5/>