5th generation of heating and cooling networks: decarbonization mission for the supply of heating and cooling
Heating and air conditioning now represent more than 70% of emissions linked to the use of buildings in France. In 2018, more than one in two households mainly used fossil fuels for heating (41% natural gas, 13% fuel oil) . To reduce greenhouse gas emissions from these uses, the National Low Carbon Strategy (SNBC) aims to reduce the individual consumption of housing, and triple the number of those connected to heating networks by 2035. In this same emission reduction objective, the Multiannual Energy Program (PPE) aims for these networks to deliver on average 60% renewable or recovered energy (EnR&R) by 2035. These objectives are reinforced by the urgency to reduce dependence on Russian gas in times of geopolitical crisis.
Faced with these challenges, the 5th generation of heating and cooling networks, or 5GDHC , are an essential solution to meet France's climate objectives, in addition to an ambitious policy to reduce energy consumption. Indeed, these high-performance networks tending towards 100% renewable and recovered energy are particularly suited to low-consumption buildings.
A distribution of heat and cold to allow the exchange of energy between neighboring buildings
5th generation networks are based on simultaneous distribution of heat and cold between buildings in the same district . The 5GDHC differs from other generations of networks in particular by its low distribution temperature: this allows the use of renewable energies - as well as the recovery of waste heat - low temperature.
Valuing the potential for energy exchange between “consum’actors”
5th generation networks are closed loops that favor energy exchanges between neighboring buildings, before resorting to renewable energies. Indeed, heat pumps located as close as possible to buildings make it possible to recover the calories emitted by a cold consumer to provide heat to another building and vice versa. The buildings connected to the heating network are then “consum'actors” : they simultaneously consume and supply energy.
To make the most of these exchanges, 5th generation networks also use calorie storage. This can be done over short periods of time (a few hours to a few days) in small decentralized storage facilities, or over longer periods (between seasons) in large natural or industrial underground reservoirs (aquifer or old mine by example) or on the surface.
A concept that aims for the use of 100% ENR&R
As this solution is based on a temperate loop (<40°C), the energy sources needed to complete the energy exchanges between buildings do not need to provide high temperature, unlikefor many other uses. They thus make it possible to take advantage of renewable energy or low temperature recovery such as shallow geothermal energy, thalassothermal energy, or waste heat from data centers, industry, metro air vents or even sewers.
In addition, since these networks are based on heat pumps consuming electricity, they can also benefit from electricity of renewable origin , such as solar panels (photovoltaic or hybrid) to supply them, thus making it possible to couple the network electricity and the heat network.
Thus, 5th generation heating networks are an ideal way to take advantage of underutilized RE&R sources and therefore to increase the share of renewable energy in the French energy mix.
A solution to be integrated into the energy transition strategies of local authorities
5GDHC networks represent an ideal solution for national or local renewable energy deployment policies, and must be correlated with energy transition strategies integrating sobriety and energy efficiency in the territories. Indeed, these networks combine very well with ambitious thermal renovation programs, or even with the development of new high-performance districts . The distribution of energy from the source to the heat pumps can be done at a very low temperature, dividing the energy losses by 5, in comparison with traditional systems. In addition, the performance of these networks is optimized when the instantaneous energy needs are relatively low, and the emitters (radiators, underfloor heating) do not require too high an entry temperature.
These networks also have their place in the context of territorial planning aimed at the multiplicity of uses in the same district aimed at energy sobriety . The ability of 5th generation networks to simultaneously deliver heat and cold gives them flexibility and versatility: they can adapt to many different needs and types of buildings (housing, industry, R&D laboratories, offices, etc.) . This variety of uses is even to be favored to guarantee a balance of needs and allow the exchange of energy between more and more consumers of cold (laboratories, supermarkets, data centers) and heat (housing, offices, etc.) .
Finally, supplying heat pumps with local renewable electricity makes it possible to intelligently interconnect electrical and thermal flows and to have a complete and holistic view of energy consumption at the scale of a territory. Thus, combining the best practices of 5th generation heating and cooling networks with the best practices on the production, distribution, storage and management of local electrical renewable energy is an opportunity for territories to create energy communities. local areas in which the carbon intensity is reduced as much as possible,benefit from a guaranteed and sustainable quality of service, and a competitive economic model linked to profitable interconnections between producers and consumers.
In Paris-Saclay, one of the first 5th generation energy networks demonstrates the relevance of this solution
In France, the Paris-Saclay energy loop is one of the first 5th generation network demonstrators. This heat and cold exchange network is based on a temperate distribution loop (approximately 30°C) , which can be supplied by geothermal heat from the Albian aquifer, drawn from a depth of 700 m, and by fatal heat from certain scientific and research infrastructures located on the territory. The network therefore uses a significant amount of renewable and recovered energy.
This is one of the demonstrators of the European D2Grids project, which aims to deploy 5GDHC networks in North-West Europe by defining a standardized technological model and clarifying the associated business model in order to increase the interest of these projects among investors. Through these five pilot sites, located in Paris-Saclay, Bochum (Germany), Brunssum (Netherlands), Glasgow and Nottingham (United Kingdom), the D2Grids project aims to demonstrate its effectiveness and the performance of 5GDHC and to encourage its adoption.
At Paris-Saclay, the loop (Figure 1) supplies each district of the Paris-Saclay urban campus with heat pumps which produce heat and cold simultaneously while recovering the renewable energy from the temperate loop as well as the heat from recovery linked to cold consumption. Heat and cold produced in this way are distributed to the various buildings in the district via decentralized networks. This decentralized architecture is an essential characteristic of 5th generation networks : it allows heat exchanges between the cooling needs of certain buildings on the one hand and the heating needs on the other.
Strong untapped potential for the deployment of 5th generation networks in France
One of the objectives of the D2Grids project, in addition to the demonstrators under development, is to study the possibilities of deploying these networks throughout the Interreg North-West Europe zone and to convince new decision-makers. Three metropolises in France were selected for an opportunity study of 5GDHC networks: Orléans Métropole (OM),the metropolis of Greater Paris (MGP), and the Eurometropolis of Strasbourg (EMS) (see Figure 2).
These three cities have set themselves ambitious goals in terms of reducing energy consumption, using renewable energies and reducing greenhouse gases in their Territorial or Metropolitan Climate Air Energy plans.
Thus, within the framework of its PCAET, the metropolis of Orléans aims to reduce overall energy consumption by 12%, to increase the share of renewable energy production by 50% and to reduce carbon emissions by 17%. GHG by 2025. Among the stated objectives for increasing the share of renewable energy production, Orléans Métropole plans to extend the existing biomass heating network for collective use, connect 22,000 homes to geothermal energy ( around a hundred buildings connected in 2012) and 15,000 solar thermal homes (i.e. 37,000 m² of panels compared to only 500 m² in 2012) as well as the reuse of waste heat from industrial sites for heating purposes. A study was carried out by the BRGM to determine how geothermal energy could be deployed in metropolitan France, in particular surface geothermal energy on shallow aquifers (Beauce limestone) or on heat exchangers, taking into account energy needs in surface and urbanization plan. The results of this study made it possible to define potential areas for the deployment of 5GDHC networks based on the areas to be urbanized (residential sectors and economic activity sectors).
By 2050, the Greater Paris Metropolis is planning a 100% low-carbon building stock and an energy mix made up of 60% renewable and recovered energies, 30% of which must be produced locally. In this context, a project bringing together MGP, APUR and BRGM proposes a global approach to establish a master plan for renewable energies, including the identification of potential resources and energy demand, the development of urban planning and technical and operational constraints for the deployment of renewable energies. Regarding the mobilization of underground resources, the MGP wishes to be able to develop shallow geothermal projects in the favorable sectors of its territory, given the considerable resources available in order to meet the objectives of the PCAEM. The results of the ongoing study will serve as a basis for defining potential areas for the deployment of 5GDHC networks.
Finally, the Eurometropolis of Strasbourg stimulated a reflection on its territory around an air-energy-climate strategy, which served as a basis for the construction of its PCAET. The 2030 climate plan aims to reduce overall energy consumption by 30% (55% in 2050), to achieve 40% (100% in 2050) of renewable energy production in final energy consumption and to reduce GHG emissions by 40% (90% in 2050). As such, the aquiferRhine alluvial represents an easily accessible renewable local energy source with great potential. Thus this source of renewable energy associated with a high energy density with the objectives of the Eurometropolis to create 3000 new residential buildings and to renovate 5000 old residential buildings per year make it a good candidate to evaluate the possibility of development of the 5GDHC.
Networks whose deployment is encouraged by recent regulatory changes
Thus, in France, many territories would be conducive to continuing the dynamic launched by the French precursors such as the Etablissement Public d'Aménagement de Paris Saclay, like the three cities mentioned above, in a context of regulatory changes encouraging solutions combining energy efficiency and low-carbon energies. The deployment of 5th generation networks will facilitate the adaptation over time of heating and cooling delivery services to buildings renovated under new regulations such as the Climate and Resilience Law. In addition, RE2020 sets a serious objective of reducing the carbon footprint of heating and cooling networks (passing the connection obligation threshold from 14kgCO2/m2/year today to 8kgCO2/m2/year in 2025 and 6.5 kg.CO2/m²/year in 2028), which can only be achieved through a decentralization of production which will allow the use of more renewable sources. 5th generation heating networks are therefore great tools to integrate into the energy policies of communities or developers, encouraged by the legislative framework.
Article signed: Nicolas Eyraud, EPA-Paris-Saclay, Mathilde Henry, Greenflex and Virginie Hamm BRGM and published initially published in the Dossier ENR of Construction21.
This new version has been updated by GreenFlex and D2GRIDS.
 National Low Carbon Strategy 2
 Ministry of Ecological Transition and Territorial Cohesion. Housing key figures 2022
 5GDHC: 5th generation district heating and cooling
 For more details, see the Cerema "Heating networks and RE2020" sheet
 Find out in detail in this article how 5th generation heating and cooling networks are particularly suited to RE2020
More information about D2Grids: www.5GDHC.eu