The Parly 2 co-ownership, bringing together 15,000 residents and nearly 300 buildings in Chesnay-Rocquencourt (Yvelines), will use geothermal energy as the main source of energy for its heating and domestic hot water.
At Chesnay-Rocquencourt, in Yvelines, the Parly 2 co-ownership has just taken a major step in its energy transition. This large-scale residential complex has initiated the conversion of its heating system to deep geothermal energywith the ambition of reducing its dependence on fossil fuels and better controlling the energy costs borne by its co-owners.
Parly 2, a “town in the countryside” at the gates of Paris
Born in the early 1960s, in the midst of a period of economic growth, the Parly 2 project is the result of an innovative real estate vision carried by the developer Robert de Balkany, his partner Jean-Louis Solal, a pioneering figure in shopping centers in Europe, and thearchitect Claude Balik. Their ambition: create, a few kilometers from Paris and at the gates of Versailles, a new residential model inspired by American achievementscombining housing, shops, leisure and services within the same complex. The project then took shape over nearly 100 hectares of land then occupied by the Poupinet sisters’ nurseries. The latter accept the sale of the land on the condition that the operation integrates religious, cultural and community facilities, a requirement which will help shape the identity of the future district.
Thought like a real “town in the countryside”, Parly 2the program provides for an unprecedented ensemble for the time, structured around a large regional shopping center and completed by a drugstore, cinemas, a hotel, sports facilities, green spaces and several thousand housing units. The first buildings were delivered from 1968, at the same time as the main amenities of the district – the apartments were distinguished by a particularly high level of comfort, with fully equipped kitchens and bathrooms, a rarity at the time. The program’s final residency was completed ten years later, in 1978.
Initially called “Paris 2”, the project will ultimately have to change its name following opposition from the City of Paris. © Parly 2
The complex today constitutes the largest condominium in Europe and represents more than half of the population of Chesnay-Rocquencourt. It brings together 278 buildings divided into 36 residences, or around 7,500 homes, to which are added a regional shopping center, several local shopping centers as well as a vast common heritage including eight swimming pools, seven tennis courts, playgrounds, etc. © Le Parisien
An energy transformation on the scale of an extraordinary co-ownership
Located in the immediate vicinity of Westfield Parly shopping center, the Parly 2 condominium today claims a national first with the commissioning of a geothermal system intended to supply your entire heating network. Until now, heating and domestic hot water needs were mainly covered by gas. A choice that has become increasingly costly given the tensions observed on the energy markets in recent years. “We will no longer have to endure fluctuations in the price of gas which have had a major impact on co-owners’ charges in recent years, particularly with the war in Ukraine.“, explains Patrice de Clinchamps, member of the main union council, to AFP.
Beyond the economic stability sought, this development must also allow co-ownership to benefit from a more favorable tax framework associated with renewable energiesin a context where environmental regulations are gradually strengthening.
A geothermal resource exploited at a depth of 1,500 meters
The device is based on theexploitation of the Dogger aquifer, one of the main geothermal resources of the Paris basin. The water is collected approximately 1,500 meters underground, where it reaches a natural temperature of 62°C. Once brought to the surface, this heat is recovered in a central boiler room before being distributed through a private network of nearly 20 kilometers. This supplies not only the accommodation, but also numerous community facilities on the estate, including swimming pools, tennis courts, playgrounds and even a church.
In accordance with the principle of deep geothermal energythe extracted water is then returned to its natural environment thanks to a second drilling dedicated to reinjection. This process makes it possible to sustainably preserve the resource while limiting the environmental impact of the installation. This technology remains underdeveloped on a national scale: today, geothermal energy represents around 1% of heat consumption in France. However, the government intends to accelerate its deployment in the coming years and is aiming for significant increase in geothermal heat production by 2035.
An investment of nearly 50 million euros
The thinking around this project dates back to 2016. After several years of technical and economic studies, the co-owners validated the principle of energy conversion in 2022. The co-ownership dedicated nearly 12 million euros to the modernization of its thermal installations. For its part, Engie, which ensures both the technical implementation of the project and the operation of the heating network, invested around 35 million euros for the construction of the boreholes, the geothermal power plant and distribution infrastructure.
However, gas has not completely disappeared from the energy mix of Parly 2. It will continue to cover nearly 30% of the site’s needs in order to meet winter consumption peaks. “Designing a geothermal installation capable of covering 100% of needs, including the few coldest days of the year, would have been technically possible but too expensive“, specifies the co-ownership in a press release.
