Keeping Sasol’s carbon reductions on track

Sustainability assured 2011Most of South Africa’s electricity is generated by large coal-fired power plants and this results in substantial emissions of carbon dioxide – considered a major contributor to global warming. In July 2011, Sasol New Energy (SNE) Holdings contracted Wärtsilä to provide a 180 MW facility. This plant will become the African continent’s largest to be based exclusively on gas-fired engines.

SNE is a business division of alternative fuels and chemicals company Sasol, and was established in 2010 to explore technologies that could be integrated into Sasol’s core processes to reduce greenhouse gas emissions and meet the company’s long-term targets for energy efficiency. Sasol has an industrial facility in Sasolburg, near Johannesburg, which currently relies on a company-owned coal-fired plant to meet part of its electricity and steam requirements.

In line with its carbon reduction strategy, Sasol began introducing the use of gas for power generation by installing two gas turbines at another of the company’s facilities located at Secunda. Another gas-fired plant, this time based on gas engines, is now being built at Sasolburg to replace the existing coal-fired power plant. Industrial customers in the region are keen to establish reliable supply due to persistent problems involving interruptions to the existing grid supply, and Wärtsilä’s gas-fired engines were therefore seen as a potent solution.

Explaining the thinking behind the new project, Henri Loubser, Managing Director, SNE, says, “Expansion of the Sasolburg facility means that new power plant technology can be used to meet increased demand for electricity, while also replacing our old generating equipment with more efficient units. It will also enable us to reduce our reliance on drawing power from Eskom. On average, the carbon footprint of Eskom’s electricity is almost 1,000 kg/MWh. Using gas-engine technology will allow us to reduce that figure by more than 40%.” Completion of the project will mean a cut of approximately one million tonnes to Sasolburg’s annual carbon emissions.

Another key environmental factor is that the new plant operates with a closed circuit cooling system, thus consuming absolutely no water. This is of signal importance in a region where water is scarce.

The plant follows Wärtsilä’s new power plant design philosophy – building architecture and interiors that improve functionality and safety. The powerhouse is divided into three sections and each set of six engines is connected to a medium-voltage room. Radiators are located on the roof for improved cooling, minimising the building's footprint. High-voltage equipment is located in a separate building. The efficiency of the Wärtsilä gas engines to be deployed is also noteworthy, as the Sasolburg plant is located at an altitude of 1,700 m, yet the deployed gas engines can operate well even in these conditions.

The Sasolburg plant is being built as a turnkey contract in which Wärtsilä is carrying out all engineering, civil works and building construction, as well as supplying all the power generating equipment and performing the electrical and mechanical installation work. Civil engineering operations have already begun and the first engines will arrive at the site next May. Handover of the completed plant is scheduled to take place in December 2012.

The Sasolburg plant is a pioneering project and similar ventures are expected to follow. The new facility is clear evidence that technologies which do not involve coal offer good business opportunities in power generation.

For Wärtsilä, the project’s significance extends much further than being the company’s first power plant in South Africa. “Our ability to execute a complete turnkey contract with both schedule and performance guarantees was key,” says Arnaud Gouet, Business Development Manager at Wärtsilä. “The ability to help the customer in arranging project financing and provide ongoing maintenance and support is likely to prove attractive in future project negotiations.”

Commenting on Wärtsilä’s offering and the company’s all-round capabilities, Loubser says, “Wärtsilä has very good and competitive technology – powerful engines which operate at high levels of efficiency and a good track record. Our relationship has been very professional – a really positive experience.”

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