Africa represents a vast region of potential hydro power, and although there are certain obstacles, the continent’s hydro presence is on the increase
IT IS widely known that in terms of hydro power, possibly the greatest unexploited potential and largest amount of planned capacity is in Africa. Compared to other regions in the world, hydro activities in Africa are still mainly spot and project specific driven as no country presently has the size of a constant ongoing market. To this day, one of the stumbling blocks in Africa is still political stability. Without a stable political system and a fitting legal framework investments and project realisations are solely dependent on Aid Programmes and cannot trigger a sustainable economic environment.
In Africa there is a permanently ongoing restructuring of the power sector. Certain countries have developed to a quite advanced level, for instance Uganda where the restructuring has been completed (private companies for generation and distribution) or Tanzania (see the article on p18-20). Other countries are taking a slower path like Zimbabwe or Nigeria, where restructuring is still in the discussion and planning stage.
In Egypt things are going a slightly different way with the development of both government and private projects. In general, encouraging reforms are taking place, but their progress is still relatively slow.
The development of the New Naga Hammadi power station on the Nile in upper Egypt, which is currently under construction, is one example of this. The US$470M project is being financed by the Egyptian Government, the German Kreditanstalt für Wiederaufbau (KfW) and the European Investment Bank (EIB). The original weir near the village of Naga Hammadi is located approximately 140km north of Luxor and was built between 1927 and 1930. It is no longer fulfiling its requirements due to increasing erosion in the riverbed and is therefore being replaced with a new weir approximately 3.5km further downstream. The purpose of the new weir, comprising an integrated navigation lock and hydro power station, is to ensure the irrigation of 235 x 103 ha of farmland as well as to produce energy for approximately 200,000 households. The dam will further serve as a new bridge over the Nile.
The development of the Naga Hammadi power station is being carried out by va-tech Hydro. The net head of the power plant will vary between 4 and 8m and the unit discharge from 175m3/sec up to a maximum of 417m3/sec. The maximum output of the turbines will be 76MW and the mean annual energy production will be 522GWh.
All electromechanical equipment for the project, including four Bulb turbines, 6.8m in diameter, and four Bulb generators with a continuous rated output of 19MVA each and a rated voltage of 11kV, is to be supplied by the Austrian company. The turbines with a speed of 71.4rpm will directly drive the generators. The company is also responsible for the supply of complete electrical equipment for the power station as well as a 220kV switchgear. The power plant and the navigation locks will be controlled and protected by the new Neptun system, which is a new integrated system especially developed by VA Tech for the control and protection of hydro power plants.
Civil works began in 2002 and commissioning of the power station is scheduled for the end of 2007. Model tests were successfully performed and approved in June 2003 and currently draft tubes are being manufactured and will be shipped on site in June this year. So far every aspect has been performed according to the project time schedule.
In Sudan, the government plans to implement new hydro projects to meet the growing demand for electricity. Currently Sudan has an installed electric generation capacity of 580MW, managed by the state owned National Electricity Corporation (NEC). It is composed almost equally of thermal (mainly oil) and hydro power. Hydroelectric power generation varies greatly over time, due to rainfall patterns. The main generating facility is the Roseires dam located on the Blue Nile river basin approximately 500km southeast of Khartoum. Roseires has an installed capacity of 280MW, but output varies greatly as water levels on the river rise and fall throughout the year. In 2001, NEC placed a contract with VA Tech Hydro for a new Hydromatrix power plant.
The Hydromatrix technology has been developed by VA Tech Hydro to meet the demand within the hydro power generation market to utilise banked up waters such as navigation and irrigation dams, intake towers, etc which previously couldn’t be developed in a feasible or an economically viable way using conventional turbine-generator solutions. The technology has been developed to enable customers to install hydro power generation with practically no environmental impact and at far more competitive costs. Construction and start-up schedules can be shortened by years, reducing interest costs during construction. Depending on the existing structure and other site conditions, larger projects (greater than 50MW) can be developed for a total turn-key project with less than US$1,250 per installed kW. Energy cost for projects under implementation and development are in the range of 25 to 35 cents per kWh.
Hydromatrix is applied by situating a number of relatively small units in a factory assembled ‘matrix’ (called module) that is easily integrated into existing dam or gate structures. The mechanical components of the turbines are based on technologies proven by over 700 axial flow turbine units installed around the world.
The scope of the NEC contract for the Hydromatrix power plant in Jebel Aulia consists of 80 turbine-generator-sets, which are installed in 40 modules by pairs. One module is equipped with two submerged, 380kW horizontal propeller turbines. Each turbine has an 1120mm diameter three-bladed runner precision cast of aluminium bronze. Generators are induction type. Additionally, the contract includes all mechanical and electrical auxiliaries. NEC will carry out local activities for the accomplishment of the contract. Since the Hydromatrix makes use of the existing dam structure, only very minor civil construction is needed.
A different solution
‘The simple Hydromatrix design [fixed guide apparatus and fixed runner vanes, oil-lubricated roller bearings and no external oil and cooling water supply] is far less maintenance-intensive and the cost of this solution is hence considerably less than the cost of a conventional pit solution,’ says Hydromatrix coordinator Harald Schmid. ‘There are no expected civil O&M costs, which is due to the Hydromatrix modules missing power house and no dredging and silt-removal requirements. Due its much lower overall investment costs compared to a conventional bulb or pit turbine solution, the Hydromatrix concept is a much more economically viable solution. Therefore the concept is extremely well suited for projects in the developing world.’
One example of this is the Jebel Aulia project in Sudan, which has seen the modules being integrated into the existing weir-structure without modifications of the already existing civil structures. The modules have been evenly distributed across the weir, thus stratifying the flow, avoiding uneven sedimentation and reducing downstream erosions on the White Nile.’
At Jebel Aulia 40 Hydromatrix units are currently in full operation. Within the next couple months the next modules will be installed and every two months 10 units will be put onto the grid. NEC has scheduled the entire plant to be on the grid by the end of 2005.
The outlook for South Africa and the southern African region still offers promising projects, but with South Africa running short in electricity from 2007 onwards, investments in South Africa or in the neighbouring region will have to come. Presently the low electricity rates in South Africa are delaying any investments; however, the coming years should see a positive trend emerge.
For more information, please contact: VA Tech Hydro, Penzinger Strasse 76, A-1141 Vienna, Austria Tel: +43 1 89 100 0 Fax: +43 1 89 100 196 www.vatech-hydro.com