The heating and cooling grid of the Paris-Saclay science and technology cluster, delivered in 2019, is one of the pilot sites of the European D2Grids project. This so-called "fifth-generation" heating and cooling grid (5GDHC) should make it possible to meet many of the challenges of the energy transition: energy autonomy, consumption of renewable and local energy, grids decarbonation, etc. It covers an area of 28 municipalities in the south-west of the Île-de-France region.
The social housing company SEQENS recently joined D2Grids project to bring a collective self-consumption photovoltaic production, the part of which not consumed by its buildings will be sold to the grid. The buildings concerned will be connected to the Paris-Saclay heating and cooling grid by 2024. Mawya Rahal, energy project manager at the EPA Paris-Saclay, and Lucas Lazzarini, energy engineer at SEQENS, told us more about this operation.
Can you present the Paris-Saclay heating and cooling grid?
Mawya Rahal: To fully understand this network, we need to look at the context of the operation. Indeed, it is part of the of Paris-Saclay urban planning, as a response to an Operation of National Interest (OIN). The objective is to develop the scientific and technological cluster of Paris-Saclay thanks to an urban ambitious strategy of sustainable development and social responsibility, supported by the EPA Paris-Saclay. This implies the implementation of an efficient and virtuous energy supply to meet the needs of existing buildings and those under construction.
We therefore wanted to set up the most virtuous system possible, based on renewable energies: the fifth generation for heating and cooling grids. This grid is based on a low-temperature energy loop, supplied with geothermal energy thanks to wells capturing the calories from the Albien Aquifer at a depth of 700m. It is supplemented by a gas back-up which takes over during peaks in consumption, particularly in winter. We are currently looking to develop other sources of renewable energy to avoid gas.
In 2016, we connected the first buildings on the Paris-Saclay plateau to the heating grid. In the long term, we want to connect about 2 million square meters of floor space, or 50 megawatts of heating and cooling capacity. Today, we have about 646,000 m² of connected housing, along with schools and public buildings.
Why did EPA Paris-Saclay join the European D2Grids project?
Mawya Rahal: EPA Paris-Saclay joined D2Grids in 2019, when the grid was delivered. The purpose was to accelerate our work and strengthen our ambitions. For example, we set up an advanced thermal demand management demonstrator, which we would not necessarily have done without D2Grids. In addition, this European project offers the opportunity to exchange with many other partners, to meet with energy players, to share feedbacks, etc. It is therefore a great asset for the development of our heating and cooling network.
The social housing company SEQENS joined the network when the D2Grids project was extended. Why did you make this choice?
Lucas Lazzarini: In June 2020, SEQENS won the contract to build three lots in the Moulon ZAC in the town of Gif-sur-Yvette, comprising 181 social housing units, which will be supplied with heating and hot water for sanitary use, by the heating grid. One of the key requirements was the implementation of photovoltaic panels on 30% of the roofs (this objective concerns the entire Paris-Saclay site). We chose to dedicate photovoltaic production to the common areas of our buildings as a priority. However, during the studies, we noted that there was excess production at certain times. In consultation with our AMO Greenflex and the EPA Paris-Saclay, we identified the possibility of selling the electricity not consumed by our buildings for the needs of the ZAC's heating and cooling grid.
D2Grids allowed us to benefit from additional support on a rather complex subject. This project implies new ways of working for our teams, especially at the administrative and legal levels. D2Grids facilitated the process as well as the feedbacks. The project would not have had the same ambition without D2Grids.
What has the cooperation between SEQENS and EPA Paris-Saclay enabled for the development of the heating and cooling network?
Lucas Lazzarini: There is a real mutual interest about energy prices. Thanks to our cooperation, our tenants will save money on the electricity charges for the common areas. We set up a rate for the sale of the surplus energy that is also interesting for us, allowing us to amortize our installation, and competitive for the heating and cooling network. In addition, the prices set are stable, which is particularly advantageous in the current context of soaring energy prices and allows us to plan for the long term.
Mawya Rahal: I can confirm that our cooperation makes it possible to plan more serenely the generalization of photovoltaic deployment on the roofs of the campus buildings, as well as the self-consumption of the electricity produced. It is part of a more global strategy for the deployment of photovoltaic energy on the entire site, as part of our positive energy territory approach. The work we are doing with SEQENS on the three lots concerned is therefore an experiment for this future deployment. We are currently in the inventory phase: we are observing what can be done, the energy potential, etc. In addition, our cooperation allows us to work together on an appropriate legal and administrative arrangement for self-consumption.
You have chosen collective self-consumption as the legal arrangement. Why did you make this choice? Can it be applied to other operations of the same type?
Lucas Lazzarini: The type of arrangement chosen here is collective self-consumption. Unlike individual self-consumption, there are several users of the electricity produced: the common parts of the SEQENS buildings, as well as the heating and cooling network equipment. Generally, SEQENS favors either the total resale of its production to EDF, or individual self-consumption with resale of the surplus to EDF. This avoids certain administrative and legal complexities and avoids the uncertainty of actual electricity production. Collective self-consumption presents complexities in defining the distribution of the production and the invoicing modalities. However, being in a large-scale project allows more time to deal with them and to carry out a real production study.
The experimentation carried out here is intended to be reproduced. As a major player in social housing in Ile-de-France, SEQENS wishes to develop solutions in order to decarbonise its housing stock. We will therefore be able to draw inspiration internally from our work on the Paris-Saclay heating and cooling grid. In addition, we will be able to share legal and administrative instructions for any other owner, social landlord or not, wishing to develop photovoltaic production on the roof. The first feedbacks, focused on the administrative challenges, should arrive by the end of 2022. The technical feedbacks will be delivered after the end of the D2Grids project.