The Montézic Power Station ( French: ''Centrale de Montézic'') is a

pumped-storage Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. A PSH system stores energy in the form of gravitational potent ...

power plant A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the electricity generation, generation of electric power. Power stations are generally connected to an electr ...

near the commune of Montézic in northern

Aveyron Aveyron (; ) is a Departments of France, department in the Regions of France, region of Occitania (administrative region), Occitania, Southern France. It was named after the river Aveyron (river), Aveyron. Its inhabitants are known as ''Aveyro ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. Its 910

megawatt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantification (science), quantify the rate of Work ...

capacity ranks it second among France's main pumped-storage facilities, and is the only one situated on the Central Massif. Montézic is a pure pumped-storage plant, which means that its upstream

reservoir A reservoir (; ) is an enlarged lake behind a dam, usually built to water storage, store fresh water, often doubling for hydroelectric power generation. Reservoirs are created by controlling a watercourse that drains an existing body of wa ...

receives little to no natural inflow of water. The station has a weekly time cycle.

History

The construction of the power station started in 1976 and it was commissioned in 1982. The following are some key dates from this period: In August 1976: the power station's access tunnel was bored, and betweenNovember 1977 and July 1978 Grading work for the plant, the connecting tunnels, and the dams was carried out. In July 1979 assembly of the turbine generators took place. In May 1981 the Etang Dam (''Barrage de l'Etang'') was completed, and from June to August the upper reservoir was filled. * October 1981: Completion of the Monnès Dam (''Barrage de Monnès''). * January 1982: Filling of the penstock tunnels. * April 1982: Commissioning of turbine assembly 1 * June 1982: Commissioning of turbine assembly 2 * October 1982: Commissioning of turbine assembly 3 * December 1982: Commissioning of turbine assembly 4

Operation

The power station was built by the

electric utility An electric utility, or a power company, is a company in the electric power industry (often a public utility) that engages in electricity generation and distribution of electricity for sale generally in a regulated market. Electric utilities are ...

company

Électricité de France Électricité de France SA (; ), commonly known as EDF, is a French multinational corporation, multinational electric utility company owned by the government of France. Headquartered in Paris, with €139.7 billion in sales in 2023, EDF ope ...

(EDF, Electricity of France), who operates it under a

concession agreement A concession or concession agreement is a grant of rights, land, property, or facility by a government, local authority, corporation, individual or other legal entity. Public services such as water supply may be operated as a concession. In the ...

Reservoirs

The power station receives water from an upper basin, the Montézic Reservoir, whose active capacity is . Two rock-fill

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface ...

s form the reservoir: * the Monnès Dam, long and high * the Etang Dam, long and high Under normal conditions, the Montézic Reservoir sits at a elevation and covers a surface area of . Due to the fluctuating water level, the reservoir is unsuitable for leisure activities. In order to remedy this problem, EDF created the Saint Gervais Lake (''Lac de Saint Gervais'') through the installment of another embankment, providing a stable body of water for the promotion of aquatic tourism. The lower basin was already in existence as a result of the Couesques Dam, a

arch dam An arch dam is a concrete dam that is curved upstream in plan. The arch dam is designed so that the force of the water against it, known as hydrostatic pressure, presses against the arch, causing the arch to straighten slightly and strengtheni ...

on the Truyère River built between 1945 and 1950. This reservoir holds a volume of . The Montézic power station utilizes a water volume of . If the four turbine generator assemblies are in pump mode, the Couesques Reservoir can be emptied in 40 hours. Both the turbine and pump modes are used on a regular basis.

Penstocks

The

penstocks A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydro turbines and sewerage systems. The term is of Scots origin, and was inherited from the earlier technology of mill ponds ...

are in

diameter In geometry, a diameter of a circle is any straight line segment that passes through the centre of the circle and whose endpoints lie on the circle. It can also be defined as the longest Chord (geometry), chord of the circle. Both definitions a ...

and in length. They carry water from the upper reservoir to the power station through the high-pressure tunnel. The water intake, located on the Liaussac Embankment (next to the Monnès Dam), has two

sluice gates A sluice ( ) is a water channel containing a sluice gate, a type of lock to manage the water flow and water level. There are various types of sluice gates, including flap sluice gates and fan gates. Different depths are calculated when design s ...

which allow the high-pressure tunnel to be closed off. Once the water has passed through the turbines, it is evacuated through the low-pressure tunnel towards the Couesques Reservoir.

Power station

The Montézic station lies under the earth, dug out of granite. It has all of the electrical and hydraulic equipment necessary for the operation of its four turbine-pump assemblies, which are each capable of generating 230 MW in turbine mode and 210 MW in pump mode, and permit the transfer of energy from the upper Montézic Reservoir to the lower Couesques Reservoir, and vice versa. The generator's 18 kV of power are raised to 400 kV by 250 MVA

transformer In electrical engineering, a transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple Electrical network, circuits. A varying current in any coil of the transformer produces ...

s and then sent on to the Ruyères Substation. The 22 MW static frequency converter (SFC) is used to launch the turbines in pump mode. It performs a progressive increase in speed (from 0 to 428

rpm Revolutions per minute (abbreviated rpm, RPM, rev/min, r/min, or r⋅min−1) is a unit of rotational speed (or rotational frequency) for rotating machines. One revolution per minute is equivalent to hertz. Standards ISO 80000-3:2019 def ...

) as well as the coupling of the pumps to the power grid. Made up of an array of thyristors, the converter enables a gradual start-up by varying the frequency and thus the speed of the machines. When the

synchronization Synchronization is the coordination of events to operate a system in unison. For example, the Conductor (music), conductor of an orchestra keeps the orchestra synchronized or ''in time''. Systems that operate with all parts in synchrony are sa ...

speed is reached, the turbine-pump assembly can be coupled to the grid. The start-up phase is performed dry, with no load. Each machine has a flow rate of in both directions. The pump-turbines are located below the maximum level of the Couesques Reservoir, which is below the minimum level. This placement is essential to prevent the creation of depressions or even cavities in the intake tunnel. As one of France's pumped storage facilities, known as STEP (''Station de transfer d'énergie par pompage''), Montézic plays a key role in the supply of the French

power grid ''Power Grid'' is the English-language version of the second edition of the multiplayer German-style board game ''Funkenschlag'', designed by Friedemann Friese and first released in 2004. ''Power Grid'' was released by Rio Grande Games. I ...

, as it provides a way to quickly restore electricity during a blackout.

References

External links

Hydrelect: Montézic Pumped-Storage Power Station, with images
(in French) {{DEFAULTSORT:Montezic Power Station Buildings and structures in Aveyron Dams in France Pumped-storage hydroelectric power stations in France Embankment dams