Dry-cooled coal-fired power station
Medupi is a dry-cooled coal-fired power station under construction in Lephalale, South Africa. Formerly known as Project Alpha and Charlie, the plant’s construction began in August 2007. It is being developed by Eskom, South Africa’s state-owned power corporation, at an estimated cost of R122.5bn.
The power plant has six units that will together generate 4,800MW. The first unit (Unit6) was synchronised to the grid in March 2015 and commissioned in July. The plant will be the world’s biggest dry-cooled, coal-fired power station, as well as the world’s fourth biggest coal-fired power plant, when fully-operational.
The project came under criticism by the locals due to political issues. The ANC-led government came under scanner as it was alleged that the party had 25% stake in the project and would be earning a profit of R1bn from the project. The plant is expected to emit approximately 25 million tonnes of carbon a year and has been criticised worldwide on climate control issues. The project, however, was approved by the World Bank for Clean Development Mechanism funding.
The plant covers 883ha on a site previously used for sports and cattle grazing. The area is near Matimba power station and the plant will be similar to Matimba in terms of operation, design and size. Medupi’s main power plant and related infrastructure occupy nearly 700ha. The remaining land is used for ancillary services, including ashing facilities.
The plant is 130m high and 500m wide, whereas the stacks are nearly 200m high. No cooling towers are installed as direct cooling technology is adopted. Other facilities include a coal stockpile, an ash dump and transmission lines that connect the power plant to the national electricity grid.
The plant accommodates six boilers, each powered by an 800MW turbine. The units are installed with 390 switch gears.
Medupi’s boilers are expected to be more efficient and operate at higher temperatures and pressures than previous generation boilers. For cooling, combustion and reduction of pollution, the plant adopts a range of technologies. It is developed as a zero-liquid effluent discharge station that continuously monitors emissions. The plant sources coal from Exxaro’s Grootegeluk coal mine, a local coalfield at the north end of the site. Coal is delivered to the plant via a conveyor.
The plant is being constructed in a phased manner to meet the growing demand for electricity in South Africa. The first phase, which began in 2007, includes the construction of the first three units and also the site clearing through controlled blasting.
The project is financed through funds provided by the African Development Bank (AFDB). On 25 November 2009 AFDB approved an R20.7bn loan to source and install the boilers and turbo generators. The loan, thought to be the biggest AFDB-sanctioned loan in South Africa, was given directly with a sovereign guarantee from the South African Government.
In addition, the project received a loan of R27bn ($3.75bn) from the World Bank in April 2010. The loan tenure is 28.5 years with a seven-year grace period. The clauses in the loan emphasise that the project should adopt cleaner technologies.
The project’s two main contracts were awarded to Hitachi of Japan and Alstom (renamed ACTOM in 2009) in November 2007. Valued at R33.6bn, the contracts were the biggest commercial contracts ever awarded by Eskom. The R20bn boiler contract was awarded to Hitachi Power and joint venture partner Hitachi Power Europe.
Hitachi Power Europe also oversees the offshore works of the project, including plant design and engineering, as well as the supply of vital components and high-grade materials.
It is providing supervision during the building and commissioning phase. For construction work and pressure part manufacture, Hitachi Power partnered with DB Thermal and Murray & Roberts.
Alstom was awarded the contract to supply all medium-voltage switchgear for Medupi. The contract, valued at R275m, included 640 switch gear units of 280 x 12kV and 360 x 17.5kV.
An engineering and training simulator contract was awarded to RDE in June 2010 to facilitate the processes at every stage of construction, commissioning and operation. The simulator optimises the processes and quality management in addition to providing scope for operator training.
The main civilworks contract was awarded to Murray & Roberts, Concor, and Grinacker. A major contract to supply 14.6mt of coal a year was awarded to Exxaro Resources Grotegeluk coal mine line over a 40-year period.
Other contracts related to the structural steel, mechanical, electrical, instrumentation and piping of six air-cooled condenser (ACC) units were awarded to GEA Air Cooled Systems.
Medupi is part of Eskom’s capacity expansion programme that is designed to increase Eskom’s service offering to South Africa. Medupi’s peak generation capacity, expected to be reached in 2016, will increase Eskom’s overall capacity by more than 10%.
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