5th generation for heating and cooling grids integrate renewable electricity to boost the decarbonisation of European cities!

What is the future and potential for district heating grids in Europe? To make them more efficient, the D2Grids project is working on diversifying the sources of supply of renewable electricity by focusing on innovation. Mathilde Henry, Energy Project Manager at GreenFlex, presents the European D2Grids project: a unique concept so-called “5GDHC” to be developed in North-West Europe, which is experimented on five pilot sites, while working on the potential synergies with renewable electricity. 

What is the D2Grids project? Why was it started?  

The D2Grids project was born out of the observation that in Europe, the share of renewable energy used for heating and cooling is far too low in relation to our objectives for reducing greenhouse gas emissions. The consortium brings together twenty European partners. Its purpose is to spread and boost the deployment of 5th generation for heating and cooling grids, low-temperature grids that allow the exchange of energy between heat and cold consumers.
D2Grids is a project that extends across North-West Europe. The project started in 2019 and was supposed to last 4 years. It allows to define a technological standard for 5th generation of heating and cooling grids based on 5 main principles: 
1.    Closing the energy loop
2.    Using Low-graded sources for Low-grade demand
3.    Decentralised and demand-driven energy supply 
4.    An integrated approach of energy flows 
5.    Local sources as a priority
 
The objective was therefore to define a technological standard for the 5th generation of heating and cooling grids. Then, it has been required to define a business model for these networks and to demonstrate their technical and economic feasibility in different contexts, different countries and with different technical solutions. Five pilot sites located in France (Paris-Saclay), Germany (Bochum), the Netherlands (Brunssum), and the United Kingdom (Plymouth and Glasgow) are currently developing 5GDHC grids.  
One among the goals is to make this solution known to as many people as possible and to encourage new project developers to embark on a 5th generation heating and cooling grid.  
To help them, key network performance indicators have been defined by the D2Grids project for each of the 5 principles: discover these indicators!  

Why is it relevant to integrate renewable energies into heating networks?  

First, to reach our greenhouse gas emission reduction targets, we need to remember that we need to activate all possible levers: energy sobriety, energy efficiency and renewable energies.
If we focus on renewable energies, we can see that heating grids make it possible to pool the production of energy at a neighborhood scale when they are based on renewable or local recovery resources: biomass, geothermal energy, heat from a waste incinerator or from data centers.   
In fact, most heating networks are already supplied by renewable or recovered sources, up to 60% in France. But we can go even further, and we must do so, because gas still represents 30 to 35% of the energy supplied to these networks: we must think about other solutions to avoid this fossil fuel energy, particularly in the current context which encourages us to move towards energy sovereignty. 
How do we link these renewable energies to the heating networks?   
Using renewable energies by heating networks is already well known. But the difference with the 5th generation is that it conveys hot water at low temperature. This temperature is then raised or lowered at the last moment by a heat pump to the level required by the final consumer. 
This system makes it possible to use low-temperature renewable and recovery energies which are currently underused, but which have great potential: shallow geothermal energy, thalassothermal energy or even the recovery of waste heat from industries or data centers, which can be used to provide heat for individual homes or dwellings for example. In this way, we can keep resources with a high graded value for uses that require it, such as industry.  

Can you tell us more about the extension of the D2Grids project schedule?

One of the principles of 5GDHC is to have an integrated approach of all energy flows in the district in which the heat network is based. Indeed, heat pumps which allow the temperature to be adjusted at the last moment to the required level are powered by electricity. So, if everyone draws heat from the heating network at the same time, for example in the evening in winter, this will accentuate the peak consumption on the electricity network. Therefore, peak consumption on the electricity grid often means the need to use fossil fuels. 
 
To solve this problem, 5th generation heating networks will lower this consumption peak thanks to interruption of consumption in buildings or to thermal storage, for example. 
The extension of the D2Grids project goes even further: trying to produce for itself as much as possible of the electricity needed to operate the heat pumps. To do so, solar energy was chosen. It was the easiest solution to implement because the heating networks are often in dense areas, with roofs that can produce this solar energy. The goal is really to encourage heating network owners, especially local authorities, to interconnect the D2Grids best practices on the production, distribution, storage and management of local electrical renewable energy on 5th generation heating and cooling grids which we have been promoting for several years. 
The challenge is to show the technical solutions that exist and to study the possible governance models. We have adapted the financial model of the 5th generation grids to this self-generation of electricity, which makes it possible to highlight the interest for the project owner of no longer having to buy his electricity, or at least less than before.   
This extension of the D2Grids project planning means that the project will end one year later, at the end of 2023. The project is therefore running for a total of five years.  

There are five different sites that are piloting the D2Grids project, and the extension is only being implemented in three of them. How will it work?  

The pilot sites of Paris-Saclay, Brunssum in the Netherlands and Glasgow in the UK are the ones that have planned to demonstrate the relevance of this extension for 5th generation heating and cooling grids. It was decided according to planning feasibility, and opportunities to get European funds: the other sites [Bochum in Germany and Plymouth in the UK, editor's note] also have in mind to study the solar potential later.  
Glasgow and Paris are prioritising the implementation of photovoltaic panels, while Brunssum is looking at two different solutions:  

• Photovoltaics 
• Hybrid solar panels, which would produce both water and electricity. 

In addition, some of these pilot sites may be asked to install electricity storage solutions if this is deemed appropriate, but in France, for example, this is still a solution too expansive for the time being, even if electricity prices can change quickly.  
What is also interesting are the main differences in terms of governance.  

• In Brunssum and Glasgow, it will be the heat network manager who will invest in the installation or the heat network owner. 
• In Paris-Saclay, a social housing company, Seqens, had planned to install photovoltaic energy on the roofs of its buildings and chose to make use of it by selling it to the heating grid owner. In this example, we can see that the consumer is becoming part of the territory's energy strategy rather than simply being passive.

Better understand this governance!  

The D2Grids project will end in a year, how can it be inspiring for other sustainable city decision-makers?  

The D2Grids project shows that 5th generation networks are adapted to several contexts. Among the five demonstrators, we have various consumer profiles: residential neighborhoods, an eco-district on a university campus, a former industrial zone... All using different energy sources. It shows that we could implement 5th generation networks in various types of neighborhoods.
On the other hand, it is required to keep in mind the objective of limiting the consumption from the heat pumps in the operation of these networks. It is therefore necessary to lower the need for high temperatures as much as possible, and thus not to think only in terms of renewable energy, but also in terms of buildings energy efficiency. So, this 5th generation is replicable, but it is even more relevant for districts where the buildings are thermally efficient.
Therefore, we would like to study in a future project how to renovate the existing heating grids and transform them into 5th generation: renovate the buildings to make them suitable for this type of technology, change the infrastructure or the piping to allow this hot water to be brought in at a lower temperature than before. This is an opportunity for the future that we have not yet explored and that would be relevant.

What other improvements do you see for the future of heating grids?  

The aim of the D2Grids project is also to encourage local authorities adopting a complete and holistic view of energy consumption at a territorial scale. It is required to anticipate the impacts of coupling heat and cold and electricity flows for example while seeking to maximize the use of truly local resources by stopping working in a siloed (or decorrelated) manner on reducing needs (sobriety and efficiency) on the one hand and renewable energy on the other.
Finally, we are trying to find new ways of cooperation and involvement of the territory's users. An organisational, contractual and governance challenge will have to be addressed. We will have to involve consumers in the discussions so that they also become energy producers for the heating grid.

Read more on our website

paul.capgras[a]construction21.fr