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New geothermal heating plant started operation in Paris, France

Screenshot of news on the new Villejuif geothermal heat plant in Paris, France
Alexander Richter 20 May 2017

A new large-scale geothermal heating plant has been innaugurated in Villejuif in the greater capital area of Paris, France. With a production of 220 GWh/ year it is one if not the largest geothermal district heating system in Europe.

Having started operation already in January this year, a new geothermal power plant in Villejuif, in the greater Paris area has now officially been launched last week.

The new Chevilly-L’Haÿ-Villejuif geothermal heat plant, the largest in Europe, is a model of renewable and economical energy. The plant will change a lot for the community, as it will help decrease the price of a MWh of heat service in the network of Chevilly-L’Haÿ-Villejuif to EUR 47 ($52)  instead of the EUR75 ($82) average paid so far.

In the Ile-de-France, an aquifer deposit, contained in the Dogger limestones, conveniently has water resources whose temperature rises between 56 and 85 degrees Celsius to about 2 km under our feet. To take advantage of this natural heat, wells are dug to pump it and create a hot water circuit. Within the Chevilly-L’Haÿ-Villejuif network, which now includes a power station in each city, there are two wells per heat plant, one for collecting water and the other for returning to the circuit. If the deposit is 1,850 meters deep, the wells are 2.1 km because they have been drilled at an angle.

This first geothermal water circuit is salty (about 7 g per liter) because it is historically sea water, retained since the Middle Jurassic period (170 million years ago) between two layers clay. In order to heat the hot water network serving collective facilities and habitats, this first network is connected with a second freshwater network via an exchanger whose principle is to bring the two waters into contact without mixing them, By making them circulate on both sides of titanium plates. In the Chevilly-Larue geothermal heat plant, for example, the exchangers, which present themselves as a large box, each contain 350 titanium plates with a thickness of 1 mm. ”  Unfolded, they would cover the surface of a soccer field,” so the manager of the plant.

After giving heat to the fresh water system that will serve the city, the geothermal water returns to the ground by the second well.

200 delivery points in the network

The freshwater system heated by geothermal water then travels through the city and distributes its heat to different distribution points, to smaller networks which then distribute directly collective dwellings and equipment. The exchangers between freshwater networks are made with stainless steel plates. In total, the network has 350 exchangers and 200 delivery points. Depending on the heating requirements, the required temperature level differs. The network is thus calculated to serve first the sites that need a high heat then those who need less heat (very well insulated buildings, underfloor heating …) to optimize as much as possible the transfers of heat up to ” So that the water does not return to the central unit to be reheated again. In the distribution network,

Cogeneration in winter Chevilly and L’Hay

While geothermal water comes out at 60-70 degrees Celsius, warmer water is needed in the winter to serve homes in heating. In order to increase its temperature further, it is necessary to add heat to it. To do this, a cogeneration system was set up in Chevilly and L’Haÿ. (Cogeneration consists of the production of two different forms of energy in a single power station). Specifically, a gas turbine is coupled to a heat recovery unit fed by exhaust gases. On one side are pipes heated by the gases which will complete heating the water. On the other hand, electricity is sold to EDF. ”  We only need heat, but it can be obtained at low prices by producing electricity that is automatically sold to EDF, ” explains Michel Andres.

A heat pump in Villejuif

In Villejuif, the new plant has an even more ecological and economical device to produce additional heat. It is a heat pump that recovers the residual heat from the mains water system that returns to the power plant to be reheated by geothermal water. The water that arrives at the end of the circuit is indeed still a little warm, around 40 degrees. The heat pump makes it possible to recover about twenty degrees of this residual heat to re-inject it in the water of beginning of circuit, already warmed by the geothermal water, in order to raise its temperature up to 80-90 degrees.

The new Villejuif heat plant is also equipped with an emergency gas boiler that contributes directly to the geothermal network of the city. It is from this boiler room booster that the three high chimneys.

In the suburb of Villejuif, the new heat plant nestled in the colours of the neighborhoods, recovering from the millstone to cover the walls of the building visible from the street, offering a vegetated roof in rising wave to adapt to The building that pushed behind, and resumed its copper colour codes, just like chimneys. In order to welcome the public who will visit the site but also the neighborhoods meetings, an exhibition room was built next to the central, accessible directly from the street. In front, the parterre of land will be used by the neighbouring school to create vegetable gardens.

The biggest difficulty in the construction of this heat plant was the underground part, which first found on its way a whole bunch of bones from the former grave of the adjoining cemetery and that had to be moved , Then the gaping holes left by the old gypsum quarries. ”  We realized that we had a veritable Gruyère-cheers below our feet, we had to fill with concrete,” recalls Michel Andres.

EUR 30 million investment

In terms of investment, the new plant cost EUR 30 million ($33 million), financed at 30% by self-financing, 20% by subsidies and 50% by loans.

In parallel with the construction of this new heat plant, the wells of the two other plants, which were thirty years old, also had the right to revamp, with a new lining to protect them from corrosion. It was chosen from fiberglass rather than steel. ”  On the one hand this material does not suffer from corrosion, on the other hand it is smoother and inert to fluids, which allowed us to maintain the same flow rate despite the reduction in the diameter of the well connected to the re-lining. With steel, we would have lost 25% throughput, “says the plant manager.

32 years of history

The history of this local geothermal network began in the 1980s, with an operational commissioning in 1985. At the time, it was an inter-communal project between Chevilly-Larue and L’Haÿ-les- Roses. An inter-municipal syndicate is created, the SyGeo, which invests in the two power stations and delegates its operation to an SEM (semi-mixed economy company), Semhach. Since 2004, the network has expanded to Villejuif, first with the two existing power stations, and then with the third one. In 2014, at the end of the first delegation agreement between Sygeo and Semhach, SEM was transformed into a local public investment company (SPL), which now belongs to the three municipalities, with 25% each, and to Sygeo for The last quarter. This transformation has avoided the requirement to tender to renew the delegation. Semhach employs 20 people and is currently chaired by Chevilly Mayor Stéphanie Daumin.

The largest network in Europe, with 220 GWh of annual production

Today, the Chevilly-L’Haÿ-Villejuif network serves 30,000 dwelling equivalents and produces 220 gigawatt-hour per year. It serves both multi-family dwellings, schools, two hospitals (Paul Guiraud in Villejuif and the Pneumology Center in Chevilly), swimming pools, companies such as L’Oréal … and is positioned as the largest network Geothermal energy in Europe. As the new power plant rises, production could ultimately rise to 300 GWh per year, encompassing complete new neighborhoods, starting with the ZAC Campus Grand Parc.

Soon 70% of energy from geothermal energy

Overall, the energy from the three cities’ networks comes from 60% of geothermal energy, 30% from cogeneration and 10% from gas-fired boilers. With the new power station, geothermal energy will increase to 70%, cogeneration will decrease to 25% and the supply of gas boilers to 5%

In the Val-de-Marne, about twenty geothermal power plants are currently in operation, producing about 1000 gigawatt-hours per year. In Ile-de-France, geothermal energy accounts for about 1% of energy production, but it is the first renewable energy source.

Visit the heat plant

The Villejuif heat plant was inaugurated on 15 May and will allow visits by the public. More information and bookings 

Source: Citoyens