East European overhaul10 August 1998
Uprating and refurbishment of existing hydro power facilities in Eastern Europe appears to be taking precedence over new construction. Suzanne Moxon draws on the experience of several countries to explain why this is so
Energy market analysts report that the economy of Eastern Europe should offer potentially lucrative hydro market opportunities. Although estimates suggest that an additional 30-65,000MW of hydro capacity is available for development in Eastern Europe and West Asia, much of the new capacity scheduled to come on-line in this region over the forthcoming years will include uprating and refurbishment rather than the construction of new plant.
Europe’s water and dam industry is an ageing part of the power sector and, as the following examples from Eastern Europe show, the hydro industry is becoming increasingly focused on modernising its older facilities which are approaching the end of their operational life. Furthermore, refurbishment and uprating clearly offer several economic and environmental advantages over the construction of completely new hydro power facilities.
Built in 1910, Amerika is a 500kW hydro plant located on the Zwickauer Mulde river in Saxony, Germany (formerly the Democratic Republic). Initially the facility was used to drive a DC generator, providing electricity for machinery in the local cotton mill, but throughout the 1960s reliance on DC current waned as more electrical drives in the machinery industry were converted to AC current.
Jörg Steinbrunner, the present private owner of the facility, says, that the days of Amerika were numbered. ‘Towards the end of the 1960s,’ he explains, ‘the turbine was showing signs of wear and tear and in 1970 a general overhaul would have been necessary, including conversion to AC current. However at this time, power generated from local coal was substantially cheaper and it was decided that refurbishment of the plant would be uneconomic.’
Indeed, as Bernhard Wallmeyer from German company Wiegert & Bähr commented, modernising small hydro plants was not the policy in the Democratic Republic. Consequently, the hydro plant was shut down in 1970 and the cotton mill closed in the early 1990s.
In February 1996 Steinbrunner purchased the hydro facility for his own private steel business. The buildings of the old site made it easier to relocate his business, self-generated electricity could be used in the manufacturing process, while any surplus power could be fed into the public grid. Furthermore, the state of Saxony was, and still is, actively promoting renewable energy and the re-operation of hydro power plants, like Amerika, which have a capacity up to 500kW. State and federal grants are also available to assist with such projects.
Explaining why he decided to buy the old, disused plant Steinbrunner said that the ‘most important factor’ was the competitive advantage offered by the generation of electricity which could be used in his steel business. In addition, ‘excellent co-operation’ with the utility which runs the local Südsachsische Energieversorgung grid, resulted in signing a power agreement in February 1997 concerning the sale of a portion of the generated electricity.
Refurbishment work at Amerika started in April 1996. Quite extensive structural repairs were required before equipment could be installed and included:
•Rebuilding the weir which necessitated 1500m3 of concrete and 60t of steel.
•New penstock with three protective panels.
•Re-arrangement of the turbine house to accommodate a new Kaplan turbine.
•Renovation of the turbine building, including a new roof. The turbine hall, which is protected by a preservation order, had to be preserved.
New equipment was supplied by Wiegert & Bähr and included:
•A vertical 500kW Kaplan turbine with a runner diameter of 2400mm, manufactured by Wiegert & Bähr. A right-angled gearbox and synchronous generator were also supplied.
•Two weir gates (17.5m wide x 1.5m high).
•Hydraulic trashrack (11m wide by 4.2m high).
The Amerika plant started production in April 1997 and its reconstruction is described as being typical of many others in East Germany. Steinbrunner explains that of 300 hydro power plants in Saxony, after 1990 only about 70 were still operating.
Today, incentives offered by federal authorities, such as financial assistance, are promoting the use of renewable energy in the country. Indeed, the law governing the sale of power to the grid has led to a boost for all types of renewable energy, including hydro power.
Utilities now have to purchase electricity at a fixed rate, which Steinbrunner describes as a reasonable tariff, and is the main reason behind increasing private investment in small hydro plants. Currently about 150 hydro plants are linked into the grid. A further 200 plants are planned to be re-connected or are under construction.
The Meinsberg station on the river Tschopau in Saxony, Germany was built in 1920 and is owned by West Saxonian Energy AG (WESAG). Originally of a capacity of 2x480kW, the station was still in use while the Democratic Republic existed although, after German unification, it only had a 20kW capacity.
After careful consideration of economic factors, WESAG decided that the aged plant required extensive refurbishment and uprating. Work was carried out by German company wasserkraft-volk (WKV) in 1993, who describes the Meinsberg station as being of a unique design. It has a mixed flow Francis turbine system, where three twin open flume turbines are mounted on one shaft. A sophisticated arrangement of the turbines in siphon chambers enables part-load operation.
WKV says that today construction of a plant like Meinsberg would almost be unaffordable and the company stresses the importance of weighing up the ‘bottom line’ figure for the options of renovating or building a new hydro plant. However, as the existing plant could be renovated without any structural alterations it proved to be competitive with modern turbines in relation to efficiency and service life. WKV carried out the following work:
•New runners with computer calculated geometry to optimise efficiency and performance.
•New guide vanes designed to optimise efficiency.
•Fully automatic control of the turbines and generators to optimise annual output.
•New draught tubes with inner and outer two-component coating and flow-optimised lay out.
•Mechanical overhaul of the bearings and shafts.
•Dismantling of the whole turbine system with complete corrosion protection.
•Renewable flexible couplings.
As WKV acknowledges, the refurbished and uprated (2x540kW) plant, which was completed in February 1995, is considered to be ‘slow running’ in comparison with more modern machines but the frictional effects are reduced by a low number of machine revolutions. Consequently, the plant can expect another long service life. WKV believes that ‘under the circumstances the technically and economically most sensible solution was selected’.
Drava river, Slovenia
Eight hydro power plants, owned by Dravske Elektrarne Maribor (DEM), are located on the Slovenian section of the Drava river. With an annual output of 2500GWh the facilities meet approximately 25% of Slovenia’s total electricity demands and have completely exploited the energy generating potential of this section of the river. Operating as run-of-river/storage facilities (the eight plants’s reservoirs can hold 84Mm3 of water — equivalent to 2.6MkWh of power), when the reservoirs are full the power plants can offer energy reserves in case of failure in the Slovenian electricity supply system.
Exploitation of the Drava river’s power potential started before World War I when construction of the Fala plant commenced. Construction was completed in 1932 and, being the oldest plant, Fala was the first of the Drava chain to face uprating and refurbishment.
In 1977 an additional unit was added to the existing seven ones at Fala. Detailed recalculations of the maximum flow of the Drava river showed that 4500m3/sec should not be exceeded, its original spilling capacity was 5600m3/sec. To increase the installed turbine discharge an additional vertical Kaplan turbine was installed in one of the five spillways — decreasing spilling capacity to 4800m3/sec.
In 1991, the then 60-year-old power plant began showing signs of material fatigue. The seven original turbine generator sets were replaced with two new ones in a new machine house, and all hydromechanical equipment of the spillways and the turbine of unit eight were also refurbished. The benefits of such work led to an increase of 7MW in installed power (rated output of 46.6MW), extending the operational capability of the plant by an additional 40-50 years.
Aware that more of their hydro plants were ageing, DEM undertook a large uprating and refurbishment programme in September 1995 (see table above). This was to encompass the three oldest facilities on the river:
•Dravograd — built in 1943 and not unfamiliar with refurbishment. After heavy bombing in April 1945 the plant had to be reconstructed. Work started in December of the same year but was not completed until commissioning of the third unit in 1955.
•Vuzenica — built in 1953.
•Mariborski — built in 1948.
Due to the outdated and worn-out mechanical equipment in all three plants, which had been operating for more than 300,000hrs, and after different technical and economic investigations had been performed, DEM decided that uprating and refurbishment was the best course of action to take — especially considering the important role the plants play in Slovenia’s electricity supply system.
All three stations are of a pier type — Dravograd was the first to have been built in Europe. The reinforced dam structure consists of three turbine piers between four spillways. Each pier accommodates a vertical Kaplan turbine with a generator above it.
At Dravograd, Vuzenica and Mariborski, the refurbishment and uprating work will include:
•Refurbishment of HV switchyards.
•Rehabilitation and installation of new equipment in the existing regional control centre.
•Rehabilitation of tele-communications system.
•Rehabilitation of the entire civil structure of the plants, gate devices on the spillway sections and power houses, lifting and trash rack cleaning facilities, as well as hydromechanical equipment at the unit’s water flow inlets and outlets.
•Replacement of turbine units, all auxiliary systems of mechanical equipment, generators, low voltage power and control cables.
The procurement of the work is being financed by a loan from the EBRD. Local costs are being financed by DEM, with the total project cost estimated at DEM197M. Vili Vindis, the project manager, describes the scheme as ambitious but is satisfied with the greater efficiency which will be achieved. The power output of each refurbished plant will be increased by 30% and the total production of the Drava chain will be increased by 9%.
Ivan Martinic, the consulting project manager, commented on how the work is going. ‘The project is depending on strictly respected time schedules,’ he said. ‘The original schedule has unfortunately been delayed by 18 months due to difficulties encountered with the supply of turbines and other problems on site.
‘However,’ he added, ‘the increasing experience of our installation team throughout this time allows for improvements. The date set for completion of the refurbishment project is now February 2000.’
Sava river, Slovenia
Moste hydroelectric power station is located on the Sava river in Slovenia. Built in 1952 it is one of the oldest power systems on this stretch of water. Savske Elektrarne Ljubljana (SEL), owner of the plant, had been noticing for some time that structures in the Moste system were ‘demonstrating serious signs of obsoleteness’ and were almost at the end of their operational life. As Andrej Kryzanowski from SEL commented: ‘After almost 50 years of operation the basic equipment is still in a good condition, however, due to its age, adequate safety and reliability of operation could not be guaranteed any more.’
Studies showed that straightforward refurbishment and uprating of the existing power system were not feasible. These problems were highlighted:
•The headrace and tailrace systems were under-dimensioned so that the existing three generator sets at full discharge did not generate any more power than is possible with the two generator sets.
•The tailrace system was in bad repair.
•Stability problems were being experienced in the powerhouse. The whole area of the Sava river is underlain by a tertiary overconsolidated marly grey clay, which is well-known for being problematic to hydrotechnical structures. The powerhouse consists of three floors and due to high slope stresses, a horizontal crack appeared in the governor floor along the ceiling. Despite repairs being carried out in 1978 and 1994, it became obvious that ‘the complete area of the powerhouse is in a kind of movement’. As Kryzanowski and Dusan Somrak, from IBE Consulting Engineers, explained: ‘Due to the deformations of the individual floors of the powerhouse and of the twisting phenomena of the whole structure, the centring of the existing generator sets is impossible. With the next slightly larger movement of the powerhouse, such as a moderate earthquake which is impossible to foresee, the operation of the power plant would be jeopardised.’
Taking these factors into consideration, an alternative to uprating and refurbishing the existing Moste system was established. A new Moste II HPP will be constructed utilising the existing dam and storage reservoir, but with the construction of the following new structures: a headrace tunnel, a new intake structure, surge tank and powerhouse with two turbine-generator sets. The new powerhouse will be sited away from the present area experiencing land movement.
Due to the increased discharge (28m3/sec to 70m3/sec) from Moste II HPP, an additional compensating basin will be needed downstream of the plant, with the construction of a third powerhouse (Moste III HPP). The compensating basin will also provide positive environmental benefits as it will prevent erosion which has been occurring in the downstream watercourse during operation of the old Moste HPP.
The construction of the 42MW Moste II and 5MW Moste III plants will uprate the power output of the Sava river substantially. The present average production of energy is 57GWh, which is mostly basic energy from the 16MW Moste I HPP. The expected annual production of the new system is 98GWh, with 63GWh being peak energy.
Construction is due to start at Moste HPP in 1999, with completion scheduled for the middle of 2003. All necessary studies, the basic design and documentation have been prepared.
As the above examples have shown, many East European hydro power plants are rapidly ageing, making uprating and refurbishment common in this region. Shifting political sands in some countries, such as Germany, have also led to redistributed resources and policy changes which are encouraging private investment in such schemes. All of these factors have succeeded in placing greater emphasis on the importance of revitalising some of Eastern Europe’s hydro power heritage.
|Some Eastern European URHP in brief|
|Albania: Planning is underway for the refurbishment and repair of five hydro power plants which form part of the Drin river cascade. These are: Fierza (500MW), Vau & Dejes (250MW), Ulza (25MW), Shkopeti (24MW) and Selita (5MW). Cech Republic: The Czech Electricity Company is planning the refurbishment of one unit at the Dalesice pumped storage plant (4x112.5MW). The work will be carried out in 1999. Germany: Czech company CKD Blansko has been uprating and refurbishing VEAG’s six-unit pumped storage plant Markersbach in Saxony, East Germany. After 80-100,000 operating hours over a period of 15 years, the guide vane bushing was showing signs of wear and tear. CKD Blankso Engineering carried out analysis and model tests in 1991-2. In 1993 CKD Blankso started the repair work on the first unit (laser hardening of the guide vane stems and modifications to the guide and thrust bearings). Work on the sixth and last unit finished in 1998 with increased efficiency and operating range in the plant being reported. Hungary: Rehabilitation can be expected in the near future on the river Hernád in northeastern Hungary. Three hydro plants, Kesznyéten, Gibárt and Felsó-Dobsza are reported to be ageing and require repair work to prevent unsafe operation. Latvia: Refurbishment at the Kegums hydro power plant on the Daugava river has been started by the state electricity company, Latvenergo. Further repair work will take place at Plavinas station. Work is scheduled to be completed by the year 2001. (See IWP&DC September 1997, pp32&34). Poland: Repair work has been taking place at the Dychow dam in south Poland. Built by the Germans before World War II, the structure experienced a ‘small failure’ on the outer part in April 1997. Reasons for this were not clear, although it is thought to be connected to the dynamic load of traffic on the dam road. (The road should not be used by traffic but is a popular short cut for large lorries). Jet grouting was carried out by the Polish division of German company Keller Grundbau. The reservoir had to be emptied during the work and problems were encountered as no original plans existed for the dam.|