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Thursday, September 10, 2015


Tehnical excursion

Friday, September 11,2015 - THE PUMPING HPP AVČE



In the past Slovenia, regarding the electric energy supply and the provision of power producing capacities, adjusted more or less to the politics of the former joint Yugoslav electric energy system. Slovenia, after the attainment of independence and the in part interrupted transmission and selling connections, the rather inconvenient structure of the production capacities revealed itself, which, under the conditions of the open market, reflect the huge gap between the electric energy prices at the time of peak periods during the day and at the time of low consumption and high electric energy prices at the abrupt breakdowns of huger production units. The consequence of the disadvantageous structure of the electric energy production are also the nocturnal surpluses of electric energy, which are being sold abroad at low prices.

SituationThe above described situations in the Slovene electric energy system represent the possibility for a construction of a pumped – storage hydro power plant, which at times of low electric energy prices (at night, atSituation

weekends) would pump the water into the accumulation basin, and at times of high electric energy prices (the peak periods on weekdays) the thus accumulated water would be used for the production of electric energy.

The project of the Pumped – Storage Hydro Power Plant Avče does fulfil all the conditions for the assurance of the cited demands. In addition it represents, due to the morfological, hydrological and geological conditions of the location/site and at the simultaneous exploitation of the already existing infrastructure in the surroundings/environment, also an advantageous investment in comparison to the other current investments in the Slovene electric energy production sector. It will have a positive impact on the operation of the chain of power plants of the Soške elektrarne company and on the operation of the power plants in the Holding Slovenske elektrarne Group.



Upper basin

Upper storage reservoir layoutTh e Upper Accumulation Basin is located respectively constructed in the north of Kanalski Vrh, in the basin formed by nature on the undulating Banjšice Upper storage reservoir layout Plateau, which reaches different heights, the maximum, however, is of about 600 m a.s.l.. In the foreseen area the natural ground gives the impression of an elongated depression respectively a shorter valley. The morphology of the ground enables the installment of the basin with the volume of about 2,170,000 m3. Due to the fact that the valley is not entirely closed, it was necessary to build two additional waterproof lateral dikes, which assure the designed volume of the accumulation. These are built from the material which was excavated on the surface of the basin (limy sandstone and limy breccia). The waterproofness of the basin is assured by an asphalt-concreted planking.

Lower basin

The Lower Accumulation Basin of the Pumped - Storage HPP Avče is the already existing basin of the Ajba accumulation. There exists a free volume between the accumulation heigths 104.50 m and 106.00 m, which is dependent on the optimum operation of the chain of power plants of the HPP Doblar and the HPP Plave. The available volume amounts to 416,000 m3, if necessary it is possible to add some water for the pumping necessities out of the accumulation Podselo of the Hydro Power Plant Doblar.

Pipeline and high-pressure tunnel

Facility cross-sectionThe pipeline and the high-pressure tunnel connect the Upper accumulation with the Power house of the power plant. It runs over the steep slope above the accumulation Ajba, overgrown with young trees forming a forest.

Facility cross-section

The total length of the pipeline and the high-pressure tunnel is up to 2216 m. In front of the power house there is the pipeline concreted in the vertical shaft and in part into the inclined tunnel. The high-pressure pipeline is at least 2.6 m and maximum 3.3 m in diameter.


Power house

The power house is located on the terrace on the left shore of the Soča River at the lower basin – the Ajba accumulation at the outfall of the Avšček stream. From the Ajba dam it is only about 2300 m away. The very power house is shaft-like. The power-house shaft circular cross-section is 18 m in internal diameter and 80 m deep. Into the shaft a reversible aggregate (turbine – pump) with power of 185 MW in the turbine programme is installed. The aggregate with the nominal discharge in the pumping programme from 26 m³/s to 32 m³/s, in the turbine programme, however 40 m³/s, is carried out with a variable speed with the nominal value of 600 revolutions per minute and the possibility of the speed variation from –2 up to +4 % of the nominal speed. The aggregate with the variable speed enables a higher adaptability to the conditions in the electric energy system and that is by regulating the frequency in the network or by changing the power in the pumping programme at huger changes of the fall. Above the shaft the building of the power house is built together with an assembly room. The ground plan of the power house building measures 60 x 35 m and the maximum height of the power house building reaches 20 m. The facility is fitted out also with a bridge crane with a load capacity of 300 t. Next to the power house there are set up transformers and the remaining auxiliary premises. The building of the power house is designed in compliance with the local architecture.

Power house layout:

Power house layout






Power house layout at 120.00° level:

Power house layout at 120.00° level

Power house bulding:


Power house bulding



Network connection

The Pumped - Storage HPP Avče is connected to the existing 110 kV network of the northern Littoral mesh, foreseen for the reconstruction on the section of the HPP Doblar – transformator station - RTP Gorica in form of a dual-current power line. The Pumped - Storage HPP Avče is loop-in into that network over a double dual-current approx. 2 km long 110 kV power line and the 200 MVA network transformer.

Technical data of the Pumping HPP Avče

Maximum full drop: Hb = 521.00 m
Effective water volume: Vk = 2,170,000 m³
Rated discharge (turbine regime): Qi = 40 m³/s
Rated discharge (pumping regime): Q = 34 m³/s
Installed turbine power: Pi = 185 MW
Installed pumping power: P = 180 MW
Annual electric energy production: El = 426 GWh
Annual energy consumption for the pumping: E = 553 GWh









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