Overview

The Entracque Power Plant, also referred to as the Upper Gesso Plant, is a major pumped-storage hydroelectric facility located in Valle Gesso, just south of the municipality of Entracque in Italy. Operated by Enel, the station has been in continuous operation since its commissioning in 1982. The plant represents a significant infrastructure asset in the region's energy grid, utilizing the natural topography of the Valle Gesso to store and generate electrical energy through a complex hydraulic system.

The facility is characterized by its dual-scheme structure, comprising two co-located but hydraulically separated power schemes: the Chiotas-Piastra Plant and the Rovina-Piastra Plant. Both schemes utilize Lago della Piastra as their common lower reservoir. To produce power, water is released from the respective upper reservoirs down to the power station situated at the lower reservoir level. The system employs pump-generators that refill the upper reservoirs during periods of lower demand, allowing the process to repeat as needed for grid balancing and energy storage.

Hydraulic Schemes and Capacity

The two schemes differ significantly in scale and hydraulic head. The Chiotas scheme utilizes Lago del Chiotas as its upper reservoir, which is located much higher in the valley and is larger than the upper reservoir of the Rovina scheme. This configuration affords the Chiotas plant the ability to produce a larger share of the electricity. The installed capacity of the Chiotas component is 1,184 megawatts (1,588,000 hp), operating with a substantial hydraulic head of 1,048 metres (3,438 ft).

In contrast, the Rovina scheme uses Lago della Rovina as its upper reservoir. This component has a smaller installed capacity of 133.67 megawatts (179,250 hp) and operates with a hydraulic head of 598 metres (1,962 ft). The combination of these two distinct hydraulic paths allows the Entracque Power Plant to manage varying water levels and energy demands efficiently, leveraging the significant elevation differences within the Valle Gesso landscape.

Construction of the Entracque Power Plant began in 1962, marking a multi-decade engineering effort to integrate these complex hydraulic systems into the Italian power grid. The project concluded with the start of operations in 1982, establishing the facility as a key operational asset under the ownership and management of Enel.

How does the Entracque pumped-storage system work?

The Entracque Power Plant operates as a dual-scheme pumped-storage hydroelectric facility, integrating two hydraulically separated systems: the Chiotas-Piastra Plant and the Rovina-Piastra Plant. Both schemes share Lago della Piastra as their common lower reservoir, while utilizing distinct upper reservoirs—Lago del Chiotas and Lago della Rovina. This configuration allows for flexible energy management within the Valle Gesso region. The operational cycle relies on the movement of water between these elevation levels to store and release electrical energy based on grid demand.

Operational Cycle and Demand Management

During periods of low electricity demand, typically at night or on weekends, excess power from the grid drives the pump-generators. These units draw water from the lower Lago della Piastra and elevate it to the respective upper reservoirs. This process converts electrical energy into potential energy, effectively "charging" the system. When demand peaks, the process reverses. The hydraulic head drives the turbine-generators, converting the potential energy back into electricity, which is then fed into the grid. The Chiotas scheme, with its significantly higher hydraulic head and larger upper reservoir, contributes the majority of the plant's output, while the Rovina scheme provides supplementary capacity. This cyclical process repeats as needed to balance the regional energy supply.

Technical Comparison of Schemes

The Chiotas-Piastra Plant features a much higher elevation difference and greater installed capacity compared to the Rovina-Piastra Plant. The following table outlines the key technical parameters for each scheme:

Parameter Chiotas-Piastra Plant Rovina-Piastra Plant
Upper Reservoir Lago del Chiotas Lago della Rovina
Lower Reservoir Lago della Piastra Lago della Piastra
Installed Capacity 1,184 MW 133.67 MW
Hydraulic Head 1,048 m 598 m
Power (Horsepower) 1,588,000 hp 179,250 hp

Construction of the facility began in 1962, with operations commencing in 1982. The plant is owned and operated by Enel. The significant difference in hydraulic head between the two schemes—over 450 meters—highlights the topographical advantages of the Valle Gesso location, allowing the Chiotas scheme to generate substantially more power per unit of water volume compared to the Rovina scheme. This dual-system design enhances the plant's overall efficiency and adaptability to varying energy market conditions.

Infrastructure and Reservoir Specifications

The Entracque Power Plant operates two distinct but co-located pumped-storage schemes: the Chiotas-Piastra Plant and the Rovina-Piastra Plant. These systems are hydraulically separated yet share a common lower reservoir, Lago della Piastra. The infrastructure relies on three primary reservoirs, each with specific structural characteristics and capacities designed to optimize energy storage and generation efficiency.

Lago della Piastra

Lago della Piastra serves as the common lower reservoir for both the Chiotas and Rovina schemes. Water is released from the upper reservoirs down to this location to drive the pump-generators. The lake is formed by a gravity dam. While the confirms its role as the shared lower basin, specific dimensions such as the dam height or total water volume for Lago della Piastra are not explicitly detailed in the provided grounding snippets. The facility’s operational logic depends on the continuous cycling of water between this lower point and the two separate upper reservoirs.

Lago del Chiotas

Lago del Chiotas is the upper reservoir for the larger of the two schemes. It is situated much higher in the valley compared to Lago della Rovina. This significant elevation difference provides the Chiotas scheme with a hydraulic head of 1,048 m (3,438 ft). The reservoir is larger than Lago della Rovina, affording it a greater capacity to produce electricity. The installed capacity for the Chiotas scheme is 1,184 megawatts (1,588,000 hp). The dam structure for Lago del Chiotas is described as an arch-gravity dam, a design choice likely influenced by the valley’s topography and the high pressure exerted by the significant water head. This configuration allows for efficient energy storage at high altitudes.

Lago della Rovina

Lago della Rovina acts as the upper reservoir for the second, smaller scheme. It is smaller in size compared to Lago del Chiotas. The hydraulic head for the Rovina scheme is 598 metres (1,962 ft), which is substantially lower than that of Chiotas. Consequently, the installed capacity for Rovina is 133.67 megawatts (179,250 hp). The dam for Lago della Rovina is an embankment dam. This structural type is often used for reservoirs where the valley width or geology favors a fill-type construction over a concrete arch or gravity design. The combination of the lower head and smaller reservoir volume results in a lower power output compared to the Chiotas scheme.

The entire infrastructure was constructed starting in 1962, with operations commencing in 1982. The total installed capacity of the combined schemes is not explicitly summed in the grounding, but the individual capacities of 1,184 MW for Chiotas and 133.67 MW for Rovina are clearly defined. The system functions by releasing water from the upper reservoirs to the power station at the lower reservoir to generate power, and then using pump-generators to refill the upper reservoirs, repeating the process as needed to meet energy demand.

What are the hydraulic and electrical characteristics of the plant?

Both schemes utilize Lago della Piastra as their common lower reservoir, while drawing from distinct upper reservoirs to generate electricity. The power station is situated at the lower reservoir, where water released from the upper basins drives the pump-generators. This configuration allows for flexible energy storage and release, with the pump-generators refilling the upper reservoirs during periods of lower demand to repeat the cycle as needed.

Chiotas-Piastra Scheme

The Chiotas-Piastra scheme is the dominant component of the facility in terms of capacity and hydraulic head. The greater head and larger reservoir size enable this scheme to produce a larger share of the total electricity generated by the complex.

Rovina-Piastra Scheme

This reservoir is smaller and situated at a lower elevation compared to Lago del Chiotas. Consequently, the Rovina scheme has a hydraulic head of 598 metres (1,962 ft). While smaller in scale, the Rovina scheme complements the Chiotas plant, contributing to the overall operational flexibility of the Entracque complex.

Combined Capacity and Operation

Together, these two co-located but hydraulically separated schemes form the Entracque Power Plant. The facility was constructed starting in 1962 and began operations in 1982. The combined infrastructure allows for efficient use of the Valle Gesso geography, leveraging the significant elevation differences between the upper lakes and the common lower reservoir of Lago della Piastra to maximize energy output.

Construction History and Operational Timeline

Construction of the Entracque Power Plant, also referred to as the Upper Gesso Plant, commenced in 1962. The facility is located in Valle Gesso, situated just south of the town of Entracque in Italy. The project involved the development of two co-located but hydraulically separated power schemes: the Chiotas-Piastra Plant and the Rovina-Piastra Plant. This topographical difference grants the Chiotas installation a greater capacity for electricity production compared to the Rovina installation. The combined operational capacity of the facility is 1064 MW. The plant functions as a pumped-storage hydroelectric power station, utilizing pump-generators to release water from the upper reservoirs to the power station at the lower reservoir to produce power, and subsequently re-filling the reservoirs to repeat the process. Operations at the Entracque Power Plant officially started in 1982. The plant remains operational as of the current status records. The development of the Upper Gesso Plant represents a significant engineering effort in Italian hydroelectric infrastructure, leveraging the natural elevation differences in the Valle Gesso region to create a dual-reservoir pumped storage system. The separation of the Chiotas and Rovina schemes allows for flexible operation based on the hydraulic characteristics of each upper reservoir. The use of Lago della Piastra as a common lower reservoir simplifies the downstream infrastructure while maintaining distinct upper storage capacities. The project's timeline from the start of construction in 1962 to the commencement of operations in 1982 spans two decades of development. Enel's continued operation of the plant underscores its role in the regional energy mix. The specific hydraulic heads and capacities of the Chiotas and Rovina plants are critical parameters for the efficiency of the pumped-storage cycle. The larger volume and higher elevation of Lago del Chiotas directly contribute to its dominant share of the total installed capacity. The Rovina plant, while smaller, complements the overall system by utilizing the distinct characteristics of Lago della Rovina. The integration of these two schemes into a single operational entity under Enel's management optimizes the use of the Valle Gesso hydrological resources. The facility's design reflects the engineering standards of the mid-20th century, with construction beginning in 1962 and concluding with operations starting in 1982. The operational status of the plant remains active, contributing to the stability of the Italian power grid through pumped-storage capabilities. The specific technical details of the pump-generators and the hydraulic separation of the schemes are key features of the Entracque Power Plant's design. The location in Valle Gesso provides the necessary geographical conditions for the high-head pumped storage operation. The plant's operation involves the cyclical movement of water between the upper reservoirs and the common lower reservoir, Lago della Piastra. This process allows for energy storage during periods of low demand and power generation during peak demand. The capacity figures for Chiotas and Rovina are precise measurements that define the plant's output potential. The historical development from 1962 to 1982 marks the period of physical construction and commissioning of the facility. Enel's ownership ensures the continued maintenance and operation of the hydroelectric infrastructure. The plant's significance lies in its ability to harness the potential energy of water stored at different elevations. The hydraulic heads of 1,048 m and 598 m are substantial, enabling efficient energy conversion. The total capacity of 1064 MW is a key metric for the plant's contribution to the regional energy supply. The operational timeline confirms that the plant has been in service since 1982. The construction period of 1962 to 1982 reflects the scale and complexity of the project. The use of separate upper reservoirs allows for independent management of water resources for each scheme. The common lower reservoir facilitates a unified power station location. The Entracque Power Plant stands as a testament to the engineering achievements in Italian hydroelectric power generation.

Significance

The Entracque Power Plant serves as a critical component of the Italian energy infrastructure, functioning as a high-efficiency pumped-storage hydroelectric facility. Its operational significance is defined by its unique dual-scheme configuration, which integrates the Chiotas-Piastra and Rovina-Piastra plants. This structure allows the station to manage two hydraulically separated systems that share the Lago della Piastra as a common lower reservoir. The plant's ability to store and release water from distinct upper reservoirs—Lago del Chiotas and Lago della Rovina—provides flexible energy management capabilities for the regional grid.

A primary factor in the plant's efficiency is its exceptional hydraulic head. The Chiotas scheme operates with a hydraulic head of 1,048 m, while the Rovina scheme utilizes a head of 598 m. These significant elevation differences enable the pump-generators to convert potential energy into electricity with high output relative to water volume. The Chiotas plant, with an installed capacity of 1,184 megawatts, contributes the majority of the station's power, leveraging its larger and higher-positioned upper reservoir. The Rovina plant adds 133.67 megawatts to the total output. Together, these components support the station's role in balancing supply and demand within the Valle Gesso region.

Within the context of European pumped-storage infrastructure, the Entracque Power Plant represents a major investment in hydroelectric flexibility. Commissioned in 1982 after construction began in 1962, the facility has maintained operational status under the ownership and operation of Enel. The plant's design, which separates upper reservoirs while sharing a lower basin, offers a model for maximizing energy yield in mountainous terrains. Its continued operation highlights the enduring value of pumped-storage technology in stabilizing the grid, particularly in regions where variable renewable energy sources require rapid response capabilities. The plant's specific technical parameters, including its high head and dual-reservoir system, distinguish it from other storage facilities in Italy and across Europe.

See also