| Tetrikhevi Hydroelectric Power Station | |
|---|---|
 The powerhouse of the Tetrikhevi HPP | |
  Location of Tetrikhevi Hydroelectric Power Station in Georgia | |
| Official name | Georgian:თეთრიხევის ჰესი |
| Country | Georgia |
| Location | Tetrikhevi,Tbilisi |
| Coordinates | 41°42′18″N44°55′58″E / 41.7049°N 44.9328°E /41.7049; 44.9328 |
| Purpose | Power, Irrigation |
| Status | Operational |
| Construction began | 1947 (1947) |
| Opening date | 1955 (1955) |
| Built by | "Gruzgidrostroy" trust |
| Designed by | "Gidroenergoproekt" institute (Tbilisi branch) |
| Owner(s) | Georgian Water and Power |
| Operator(s) | Georgian Water and Power |
| Dam and spillways | |
| Impounds | Upper Samgori Main Canal |
| Reservoir | |
| Creates | Sioni Reservoir (primary source) |
| Total capacity | 300×10 240,000 acre⋅ft(useful capacity)[1] |
| Catchment area | Iori River |
| Tetrikhevi HPP | |
| Commission date | 1955 (1955)[2] |
| Type | Conventional |
| Hydraulic head | 109.66 m (360 ft)[3] |
| Turbines | 2 × Hydro-units: •Francis turbines (F15-VM-140)[4] • Generators (VGS-260-70-12)[3] |
| Installed capacity | 13.6 MW[5][a] |
| Annual generation | 25–30 GWh |
| Part of theSamgori cascade. Serves as a training base for theGeorgian Technical University.[9]  Show zoomed in Show zoomed midway Show zoomed out | |
Tetrikhevi Hydroelectric Power Station (Georgian:თეთრიხევის ჰესი) is a hydroelectric power station in Georgia, the third and final stage of the Samgori cascade, located on the Upper Samgori Main Canal on the eastern outskirts of Tbilisi in thesettlement of Tetrikhevhesi[b]. It is a key element of the Samgori irrigation and energy system, created in the post-war years to irrigate arid lands and generate electricity. The station is also notable for its status as an active training and laboratory base for power engineering students from theGeorgian Technical University.
Construction of the station was carried out as part of the "people's construction" of the Samgori system starting in 1947; the Tetrikhevi HPP was put into permanent operation in 1955. In 1995, the station was privatized by its workforce, which enabled its rehabilitation and a significant increase in electricity generation. The current owner isGeorgian Water and Power.[2]
By design, it is a diversionary, canal-type HPP. The installed capacity of the station is 13.6 MW. The powerhouse contains two hydro-units withFrancis turbines, operating at a design head of approximately 110 meters.
A distinctive feature of the Tetrikhevi HPP's operation, like the entire cascade, is its seasonal regime: during the winter, the station generates peak electricity by transferring water from theSioni Reservoir to theTbilisi Reservoir, while in the summer, the stored water is used for irrigation.
The Tetrikhevi HPP is an integral part of the Samgori irrigation system, one of Georgia's largest land reclamation projects, implemented in the post-war years. The project's goal was to irrigate 70,000hectares of arid land in the Samgori Steppe east of Tbilisi, which historical accounts noted was "an ancient dream of the Georgian people." The Samgori Steppe is a hilly plain at an altitude of 300–1,100 m above sea level with an arid climate: the average maximum temperature reaches 28–31 °C (absolute maximum 40 °C), and the average annual precipitation is only 424 mm, making agriculture impossible without artificial irrigation. To address this, a comprehensive scheme was developed to utilize the flow of the mountain riverIori.[1]
The system is based on the interaction of two key hydraulic structures:
These two reservoirs are connected by the 41.6 km long Upper Samgori Main Canal. To draw water from the Iori River near the village of Paldo, headworks were built, including a low-head concrete dam and a three-chamber settling basin to remove sediment. The canal itself is a complex engineering structure, incorporating "almost all types of hydraulic structures: tunnels, galleries, aqueducts, siphons, and canal-bridges."[1] A cascade of three diversion HPPs with a total installed capacity of 31.4 MW was built along the natural elevation drops of the canal:
The uniqueness of the system lies in its seasonal operation. In winter, when there is no need for irrigation water, water is transferred from the Sioni Reservoir through the canal to the Tbilisi Reservoir, and the cascade's HPPs generate valuable regulating electricity. In summer, the water accumulated in the Tbilisi Reservoir is used to irrigate land via the Lower Samgori Canal. Before the construction of the Sioni Reservoir, the cascade generated 150 million kWh of seasonal (summer) energy. After the Sioni Reservoir was commissioned and the system shifted to a winter regime, generation reached 173 million kWh of regulating (winter) energy, significantly increasing its value to the power system.[1]
The decision to build the Upper Samgori irrigation system and its hydroelectric power stations was made by the Council of Ministers of the USSR in 1946. The technical design was developed by the Tbilisi branch of the "Gidroenergoproekt" institute and was completed by March 1947.[1]
The construction of the Samgori system was declared a "people's construction project," with the "Gruzgidrostroy" trust (formerly "Khramgesstroy") as the direct contractor. In 1950, builders from the trust arrived at a location described in the press as a "'white spot' in the waterless Samgori Steppe" and founded a settlement for future HPP workers. Thousands of workers, engineers, and employees from Tbilisi, as well as collective farmers from adjacent districts, participated in the construction of the canal, including the section near Tetrikhevi. Many of them learned new trades on-site: for example, collective farmers S. Karkozashvili and A. Khutsishvili from the Kaspi district became a carpenter and a concrete foreman, respectively, while K. Kutsniashvili from the village of Digomi became a skilledStakhanovite mechanic.[10][13] Thanks to the construction of the system, new settlements,Tetrikhevi andVaziani, were founded on the irrigated lands.[12]
The station was put into temporary operation in 1952 and into permanent operation in 1955.[2]
The Tetrikhevi HPP operated as part of the power system of the Georgian SSR. The initial automation project, approved in 1947, was eventually radically revised due to technological advancements, and all three stations of theSamgori cascade were fully automated.[1] In 2010–2011, major overhauls of the hydro-units were carried out at the station.[14]
In the 1990s, during a period of large-scale economic reforms in Georgia, the privatization of small HPPs began. This process was accompanied by disputes between the state-owned company "Sakenergo," which sought to maintain centralized control over the power system, and the Ministry of State Property Management, which saw privatization as a means of attracting investment. In this context, and pending recommendations from theWorld Bank on restructuring the industry, a temporary moratorium on the privatization of energy facilities was declared in the country.[15]
In March 1995, the Tetrikhevi HPP was privatized by its workforce through a direct sale.[16] At the time of privatization, the station was not operational, but after an investment of348,000 lari in rehabilitation, it was restarted. As a result, electricity generation increased significantly: from3.7 million kWh in 1995 to13.7 million kWh in 1996 and26 million kWh in 1997. The station employed 23 people.[7] The station later became the property ofGeorgian Water and Power.
Two verticalhydro-units are installed in the machine hall:[3]
The electricity generated by the generators at 6.3 kV is stepped up to 35 kV at an outdoorswitchyard. The switchyard is equipped withpower transformers T-1 (PDUF-15000/45) and T-2 (TMN-6300/35).Transformer T-2 is aTMN-6300/35 type oil-immersed power transformer,[20] manufactured in accordance withGOST 11920-85. The abbreviation TMN stands for "three-phase, oil-immersed, with on-load voltage regulation." Its main characteristics per the standard are:[21]
The switchyard is also equipped with C-35oil circuit breakers. The station is connected to the Georgian power grid via a double-circuit 35 kVpower line to the "Navtlughi" substation.[1][20]
The Tetrikhevi HPP, like the other stations in the cascade, plays an important role in Georgia's power system by generating electricity primarily during the winter, when there is a deficit of hydro resources. Simultaneously, it is a key link in the irrigation system, ensuring the transfer of water for agricultural lands in the summer. The station's electricity tariff in 1999 was 2.17 tetri/kWh.[22]
| Year | Generation, million kWh | Year | Generation, million kWh |
|---|---|---|---|
| 1995 | 3.77 | 2004 | 21.38 |
| 1996 | 13.68 | 2005 | 30.48 |
| 1997 | 29.06 | 2006 | 29.37 |
| 1998 | 22.56 | 2007 | 25.61 |
| 1999 | 13.27 | 2008 | 12.60 |
| 2000 | 13.36[23] | 2009 | 18.78 |
| 2001 | 18.07 | 2010 | 35.99 |
| 2002 | 23.19 | 2011 | 39.00 |
| 2003 | 29.10 | 2012 | 26.47 |
The Tetrikhevi HPP holds a status uncommon for most industrial facilities. By a decision of the "Sakenergo" Department, the station, along with its training and laboratory building, was transferred to the Faculty of Power Engineering of theGeorgian Technical University. At this operational HPP, power engineering students undergo industrial and pre-diploma internships and perform laboratory and practical work, making the station an important center for training engineering personnel for Georgia's energy sector.[9]
In the early years of operation, wave formation was observed in the long, high-velocity canals of the Satkhenisi and Tetrikhevi HPPs, causing significant turbulence in the stilling basins. The problem was solved by installing special damping devices. Later studies showed that to prevent waves, it would have been sufficient to change the canal bed profile from flat to concave, a solution that was successfully implemented at theTkibuli HPP.[1]
Due to the limited water supply through the Upper Samgori Canal (often not exceeding 7-8 m³/s) for agricultural needs, the Tetrikhevi HPP frequently operates with only one hydro-unit, which artificially limits its generation and prevents the full utilization of its installed capacity.[14]
As of 2014, the station employed 19 people, mostly from the local population, with an average salary of 600–700 lari.[14] In addition to the HPP, other enterprises were located in the settlement; for example, in 1996, the joint-stock company "Vertsi," which was engaged in primary wool processing, was based here.[24]
Since water from the Upper Samgori Canal flows into the Tbilisi Reservoir, which is a source of drinking water, the station pays attention to preventing pollution. There is an issue of household waste from the nearby Lilo landfill entering the canal, which requires action from the organization operating the canal.[14]
The 35 kV switchyard and oil storage area are equipped with systems to prevent transformer oil spills, including oil collectors and drainage systems that prevent petroleum products from entering the soil and groundwater.[20] The importance of these measures is underscored by the fact that the turbine oils used at the station are combustible liquids.[19] The station site is composed of Oligocene deposits (sandstones, argillites, clays) overlain by a layer of loam. The area is located in a seismic zone with an intensity of 8 on the MSK scale.[25]
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