Kelag implements a 4-stage cascade in Kosovo
With the completion of the few remaining tasks, the Carinthian energy provider KELAG was recently able to draw a line under a very challenging power plant project in the Republic of Kosovo.
After acquiring an existing small-scale power plant in the community of Deçan back in 2009, two downstream plants and one upstream plant were constructed in addition to this in the years that followed. All four power plants, which were equipped with the very latest technology, are now in operation. In a standard year, the cascade generates roughly 105 GWh of clean electricity which is largely paid for via the state feed-in regime. The new power plant chain thus makes a significant contribution to increasing the stability of the network and the security of the supply of power.
The community of Deçan is located in the west of Kosovo, not far from the borders with Montenegro and Albania. The small town, which is situated at an altitude of around 550 metres above sea level, enjoys international renown which it owes primarily to the monastery of the same name that is located in a narrow mountain valley roughly two kilometres west of the town. Deçan Monastery is a Serbian-Orthodox monastery dating from the Middle Ages – one of the last remaining in Kosovo. It is regarded not only as a place of pilgrimage and a sight that is famous internationally, but is also home to the only fully preserved medieval fresco murals showing Byzantine art. During the Kosovo War in 1999, the monastery provided Serbs, Roma but also Kosovo-Albanians who were fleeing the war with a roof over their heads. During these difficult times, the complex was spared destruction not least owing to the dedicated protection that was offered by KFOR troops. The monastery was declared a World Heritage Site by UNESCO in 2004, and the close protection provided by the KFOR units is maintained to the present day.
New life for power plant that was destroyed
Around 10 km away from the monastery, there has for decades been a state-owned, small hydropower plant which is situated on the banks of the Rivers Deçan and Lumbardh. However, the small power plant, which was built in 1957, was less fortunate than the monastery. It was partially destroyed in the chaos of war and stood idle for a number of years. New prospects for the plant only opened up in 2003 when a Kosovar living in America offered to repair and restore the power plant using US funding. As a consequence, the entire plant was revitalised, the turbines were restored and a new generator from the company Koncar was installed. Lumbardhi power plant (today known as Lumbardhi 1), which has a bottleneck output of 8.3 MW, began operating again in 2005. But three years later it was up for sale; the investor had begun looking for a buyer that was willing to take over the plant. He found great interest from KELAG, which was very quick to identify the great potential of this river course. KELAG bought the small power plant in 2009 and then immediately set about planning a cascade comprising three further power plants along the waterway. “For this purpose, we teamed up with a partner from Austria that had been active in Kosovo for many years, has good contacts and is very familiar with the general legal conditions and local conventions. It acquired 10 per cent of the shares in the power plant company,” recounts qualified engineer Ingo Preiss, Managing Director of Kelag International and the man responsible for the whole project.
But the signs were not all that favourable. Before the first spade was put in the ground, it was necessary to overcome the hurdles of the official state procedures and successfully negotiate with the monastery. “In Kosovo, nobody had confidence that we would be able to reach agreement with the monastery. Ultimately, the monastery complex’s status as a World Heritage Site means that it is subject to strict safeguards, and a defined protection zone exists around the monastery. We were therefore aware that it would not be easy to gain the consent of the monastery. Another factor was that at this time Kosovo was still heavily under the influence of international agencies, and there were no norms and standards governing a power plant project of this type. We essentially set a precedent,” reflects Ingo Preiss, pointing out that ultimately the negotiations with the monastery proved to be less complicated than the official approval process. The environmental and natural conservation procedures in particular turned out to be very difficult. The project manager from Carinthia views the Environmental Impact Assessment that needed to be passed successfully to be similar to the type of EIA procedure that is known in Austria. In total, all the official procedures and pre-negotiations were set to stretch out over three years before the first diggers could move in.
Good conditions for a cascade
The Carinthian energy provider is involved in Kosovo not least because of the favourable hydrological conditions in the region. The surrounding mountains extend up to 2,500 m above sea level. They present the first barrier for moist flows of air from the Mediterranean at which precipitation falls regularly. In winter, the snow in the mountains can easily pile up to four or five metres high. The snow thaw therefore lasts a long time, usually right into June. However, in summer there can occasionally also be dry periods. The plan for the cascade then envisaged constructing two plants downstream and one plant upstream of the existing Lumbardhi 1 power plant. The latter has three stream catchments and therefore three tributaries which discharge into a 25 million m3 equalising reservoir. Overall the cleverly designed tributary system consists of around 12 km of concrete channels, three smaller tunnels and the steep drop – so the penstock leading to the power plant. The first new plant to be implemented beneath Lumbardhi power plant was Belaje power plant with a bottleneck output of 8.2 MW, then the bottom stage was constructed in the form of Deçan power plant. It reaches 9.81 MW. Finally, the last project to be constructed was the upstream Lumbardhi 2 power plant. With an output of 6.2 MW, this is the smallest power plant in terms of performance.
Very busy roads
The first construction works at Belaje power plant began after the snow thaw in 2013. The plant was able to start operating at the end of 2015. “The dry conditions in summer very much benefited the construction process, which meant we were able to make very good progress with the works. And yet executing the construction works was still the biggest challenge of the project,” says Ingo Preiss, referring to the fact that the pipe laying works, which were awarded to local companies, were particularly difficult owing to the large pipe dimensions of up to DN 2200. The pipeline runs largely in the road along the valley but in summer this road is very busy with tourist traffic – and it had to be kept open in all circumstances. Bypass routes were therefore created to prevent gridlock. A similar situation arose in the autumn when lots of wood is chopped down in the neighbouring forests and the route for the timber trucks had to be kept clear at all times. “This was no easy task,” as Ingo Preiss concedes. The fact that the checkpoints with the prescribed checks did not really make the situation any easier is obvious.
11 kilometres of GRP pipe
When it came to the type of pipe, the choice was not that difficult for the operators. They put all their fatih in GRP pipes, with roughly 11 km being laid in total for the three power plants. Whereas pipes from a Turkish manufacturer were used for Belaje and Deçan power plants, the operators opted for the grades of the GRP Flowtite pipe from Amiblu for Lumbardhi 2 power plant, which was the last to be constructed. The latter proved an excellent choice not just in terms of their handling during laying, but also during operation thanks to their exceptionally smooth inner surface. The team that laid the pipes had plenty to contend with from a technical point of view. There were no fewer than eight river crossings to design. “For Lumbardhi 2 power plant four culverts were built, three were constructed for Belaje power plant, and one was required for Deçan power plant. The companies that were commissioned to do the work came up with very good solutions to these technical challenges,” says Jörg Friedrich, the construction project manager from Kelag.
Challenges at Deçan PP
As part of implementing the first stage - for Deçan power plant - which was constructed between 2014 and 2016, an existing drinking water network was also replaced at the same time. This turned out to be complex and costly because the supply of drinking water to the small town of Deçan had to be maintained throughout. “Delivering the Deçan power plant generally presented us with a number of challenges. In this context, the considerable depth of construction should primarily be mentioned. As the two Francis turbines have a negative suction head due to the drop – so the machine shaft is located below the tailwater level, the powerhouse had to be designed to be correspondingly low. So low that the level of the bottom of the machine hall is roughly 10 m below ground level. The excavation depth at the site of the powerhouse was up to 14 m, and the rear section of the building was incorporated into the steep slope behind it,” reports Jörg Friedrich. To support the excavation pit, a bored pile wall with 128 reinforced concrete pillars with a length of up to 17 m was constructed all the way round. According to Friedrich, the water drainage in the construction pit was just as complicated and costly.
Know-how from Austria
As with the previous projects in the Balkans, all of the planning work was done by the competence centre of the power plant department of KELAG itself, which was ultimately also responsible for supervising the construction work. In addition, with the technical trades in particular, the expertise of Austrian companies was used. The electromechanical equipment at the two downstream plants - Belaje and Deçan - was provided by the company Kössler from Lower Austria, which delivered two Francis turbines to Kosovo to be installed in each of the two power plants. To handle the seasonal fluctuation in the amount of water available in the best way possible, the turbines were chosen with a size ratio of from one third to two thirds. Whereas Belaje power plant achieves a bottleneck output of 8.2 MW with a drop of 123 m, Deçan power plant achieves a power output of 9.81 MW with a drop of 176 m.
Different links in the chain
Around a third smaller than Deçan power plant is the upstream Lumbardhi 2 power plant, whose construction began after the snow thaw in the spring of 2017. It is also the power plant at the highest altitude – the water catchment was created around 1,400 m above sea level. “The 2017 construction season was very much defined by a dry period, which had a very beneficial effect on the progress of the construction work. We were able to complete trial operation back in December 2017 and transfer the plant to normal operation,” recounts Ingo Preiss. In contrast to the other power plants in the cascade, Lumbardhi 2 power plant was equipped with a single turbine, specifically with a 6-nozzle Pelton turbine. The operators once again placed their trust in the know-how of an experienced Austrian hydropower specialist: The company Geppert from Hall in Tyrol supplied the modern turbine with a vertical axis that drives a generator via a directly coupled shaft. The 3-phase synchronous generator supplied by TES rotates at 600 rpm and is designed for a rated apparent power of 7,350 kVA and a voltage of 6,300 V. Drawn cup bearings were used due to the high demands from the radial forces of the Pelton turbine. To achieve a maximum output, a special rotor technology with an efficiency level of 98.25% (cos phi 1/100 load) was chosen. The generator was given a robust design and can withstand a short circuit with two and three phases. With this equipment, the upstream Lumbardhi 2 plant is able to produce a bottleneck output of 6.2 MW. As favourable as the weather conditions were for the construction works, the transportation of the machines as far as the powerhouse would prove to be a difficult task. It was necessary to transport them to their intended location along a 14 km long gravel road, which in places was very steep and featured some extremely tight bends. “To withstand the weight of the laden vehicle, we had to temporarily support the four bridges along the route using steel girders. Once it arrived at Deçan power plant, the generator weighing several tonnes was transferred onto a short vehicle using a 100t mobile crane, which is generally not easy to get hold of in Kosovo. Finally, a chain excavator had to support the 800 hp tractor unit to overcome the final incline before reaching the Lumbardhi II powerhouse. This was a real achievement!”
Improvement in the grid situation
An important point in the overall cascade project involved the grid connection. “The existing Lumbardhi power plant was connected to a 12 km long, old 30 kV overhead transmission line. The capacity would not have been sufficient for the entire cascade. The connection to the 110 kV grid was thus essential – even though this was not straightforward. Although a 110 kV transformer station is located nearby, the integration with the 110 kV switch panel and in particular the required coordination with the grid operator were extremely complicated,” says Dietmar Holzer, project manager for the entire grid connection, in summary. To make the connection to the grid, a 40 MVA transformer was installed and 6 km of power cables were laid from the bottom Deçan power plant up to the transformer station. The new grid situation in the valley, which is difficult to access, has resulted in significant improvements in respect of the stability of the grid and therefore the reliability of the power supply. Ultimately, grid outages and shutdowns, which often lasted for more than five hours, were a frequent occurrence. Blowdowns and heavy snowfall were the main causes of them. Thanks to the connection to the 110 kV grid, the number of outages has been reduced considerably.
Monitoring from Klagenfurt
For regular operation of the new cascade, KELAG employs a team of ten local workers who oversee ongoing operation of the plants. However, all four power plants are essentially designed to be operated fully automatically. For this purpose, the process and control technology was designed as an essential part of the overall concept and put out to tender separately. In the case of the cascade power plant series in Kosovo, a thorough, Simatic-based control technology system was developed and implemented, and this provides KELAG with professional, comprehensive access to the plant from its base in Klagenfurt. For this purpose, fibre-optic cables were also laid throughout for the new plants. “Monitoring the entire cascade is very important to us. Especially in summer when conditions are dry, at least a certain amount of hydropeaking using the balancing reservoir of Lumbardhi 1 power plant is possible. In such cases, the facility is shut down for roughly ten hours so that it can then be run through for six to seven hours again. But there are of course also times in summer when we automatically maintain gauge-controlled operation. However, you have to admit that in general the main periods of power generation are during the snow thaw,” says the project manager.
105 GWh of green electricity per year
In retrospect, Ingo Preiss can reflect positively on the extremely complicated project in Kosovo. Not least owing to the great experience of power plant projects that KELAG International now boasts in the Balkans, the project was delivered highly professionally – even if not everything was quite so straightforward. Ingo Preiss says: “All deliveries to Kosovo were generally made without any problems. But it should of course not be forgotten that spare parts and small pieces of equipment are almost impossible to obtain in the region, and everything that is imported must also have duty paid on it.” It was only a few weeks ago that KELAG completed the final remaining tasks and improvement works so that the project can now be considered to be completed. For the region bordering Montenegro and Albania, the power plant today represents an important improvement to the electrical infrastructure. In a standard year, the new cascade supplies 105 GWh of clean electricity to the grid. The successful conclusion of the power plant project confirms KELAG’s commitment to Kosovo, a country that offers plenty of further potential for other power plant facilities.