Eskom’s two biggest coal-fired power stations – Medupi and Kusile – have a serious design flaw which has crippled their ability to generate power.

Recent reports found that the height of the power stations’ boilers is too low, which results in higher temperatures and damaged equipment.

The boilers are currently 130 metres tall but need to be 142.5 metres high to reduce operating temperature and allow the power stations to function at full capacity.

Eskom CEO Andre de Ruyter previously said the temperature of the exhaust steam was 128 degrees, which is damaging the equipment.

To determine how Eskom could have made this error in the design of its power plants, MyBroadband spoke to energy advisor Ted Blom.

Boiler height problem

Blom said that the Medupi power station was flawed when it was first conceived, thanks to Eskom selecting the wrong technology.

“Medupi was flawed from inception,” Blom said. He explained that the technology choice for the power station was not suited to the on-site coal, and a fluidised bed system would have been better suited for the application.

“The design teams were also not Eskom veterans who understand that South African coals are slower-burning than coal sourced from other sources and hence require either different boiler designs or different combustion patterns.”

“So the local coal is still burning in the combustion chamber when it starts going through the filters, instead of being fully combusted ash as per the design parameters,” he said.

Blom explained that this results in excessive heat in the exhaust chambers and damage to equipment due to increased temperatures.

“If the metallurgical analysis had been properly considered, the design team should have observed the combustion characteristics and modified the template design accordingly.”

“This should be standard practice in power station design and points to either gross negligence or gross incompetence,” he said.

What went wrong

Blom noted that this boiler design flaw is common on all power generation units at both Medupi and Kusile, calling for a serious amount of work to fix.

“Eskom’s previous risk mitigation strategy was to diversify suppliers of power stations in order to mitigate latent defects inherent in a particular suppliers plant,” Blom said.

“These defects worldwide typically only show up after commissioning – hence the need for the diversity rule in all well-run utilities.”

Diversified suppliers are important to reduce the company’s vulnerability to these types of errors.

“In 2008, Eskom’s Brian Dames deliberately overrode that rule and declared Eskom’s new ‘fleet strategy’ – where all future units would be supplied by the same suppliers,” Blom said.

“This was of ‘state capture’ in the early days where Chancellor House was involved in the Eskom supply chain.”

Owing to the added work required, De Ruyter has now said Medupi will be completed in 2021 and Kusile in 2022.

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