One of Bulgaria’s key energy facilities – PAVETS “Chaira” will remain out of order for a long time. The pumped-storage plant near the village of Sestrimo – the largest of its kind in all of South-Eastern Europe – was a large producer of electricity and could be an invaluable balancer of the national electricity system. But in the spring of 2022, it suffered a serious accident and has been closed ever since. To this day, it is a mystery what exactly happened, with even talk of sabotage. The damages are obviously very severe and difficult to remove, as the official energy minister Rosen Hristov explained that BGN 2 billion may be needed.
Analyzes and investigations into the causes of the accident and the damage caused by it began already after the fatal accident, when during the trial start-up after a planned repair, the plant suddenly shook with a rumble and was immediately stopped.
It is now clear that one of the four hydro units is unsalvageable.
“The final report from the Swiss engineering company AFRY Switzerland, which is investigating the cause of the accident, is expected in the middle of the month,” reported Economic.bg. In front of the publication, NEK executive director Martin Georgiev explained that the fourth hydro unit, which crashed during the tests in 2022, cannot be restored and its turbine part will have to be replaced. For this purpose, a tender procedure will be announced by the end of the year. However, the repairs and installation work of the new components will take a long time, and according to the head of NEK, the fourth unit will be operational “after 2025.”
The other units, for which the necessary repairs are of a smaller scope, will be restored by Toshiba, the manufacturer of the equipment, and the ABB-Voith consortium (which in 2019 was commissioned to rehabilitate the entire plant, but instead ended up with an emergency trial situation and forced shutdown in March 2022)
It turns out that the severe accident in “Chaira” caused unprecedented damage. “The case is complicated, it is not part of the standard services, there is no ready-made solution and experience. Currently, NEK is conducting negotiations with the companies for the restoration of the plant and for the selection of technical solutions,” explained Martin Georgiev to Economic.bg.
According to him, there is hope that the repairs of two of the units will be completed within the next year, and for the third unit, “commissioning” was possible in 2025.
Why is it so important?
Information published on the NEK website answers this question:
PAVETS “Chaira” is the largest underground plant on the Balkan Peninsula, located in the Rila mountain, below the “Belmeken” dam.
It is the second stage of the construction of the “Cascade” Belmeken-Sestrimo” hydro complex and PAVETS “Chaira”. The plant has installed 4 reversible Toshiba units with nominal capacities of 216 MW – in turbine mode and 186.2 MW – in pump mode Units I and II have been in operation since April 1995, and the other two since August 1999.
PAVET “Chaira” provides an additional opportunity to optimize the operating mode of the basic production capacities in the NPP and TPP and improves important technical qualities of the electricity system:
flexibility in managing normal regimes on a daily and weekly basis; maneuverability when replacing large generating capacities that have been accidentally lost.
Plans
In order to increase the energy efficiency of the complex, it is planned to build the “Yadenitsa” hydro node, consisting of the “Yadenitsa” dam and a reversible pressure tunnel with a length of 6.73 km, connecting the “Yadenitsa” dam to the lower leveler of the PAVETS “Chaira”. This will make it possible to increase the time of continuous operation of PAVETS “Chaira” in generator mode at full power from 8.5 to 22 hours.
How it works
In conventional hydroelectric plants, the water passes through the turbine to produce electricity and continues on its way. At PAVEC there are two reservoirs with a difference in the height at which they are located. During the hours when the power system is loaded and energy production is needed, the water from the upper reservoir passes through the turbines and drives them, producing electricity, but does not flow out like in the dams, but is collected in the lower reservoir. During hours when the power system is not loaded and electricity is cheap (for example, at night or during other times of low consumption), special pumps return the water to the upper dam. This enables the same water to be reused when demand is high.
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2023-11-13 23:21:42
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