Eskom says more stations vulnerable to wet coal

[miningmx.com] – SOUTH Africa’s power system remained vulnerable to supply shocks with an interruption of even 1,500MW able to raise the risk of renewed load-shedding, said Eskom CEO, Brian Dames.

“If anything goes wrong with about 1,500MW, you really put supply demand balance at risk,” said Dames, who added that the utility had restored some 3,000MW of power at Kendal power station which had been closed down in the early morning of March 6.

Astonishingly, even if a substantial part of the heavily delayed Medupi power station had been operating, load-shedding may still have occurred so signficant was the swing in available supply.

As it was, Eskom called on some 2,000MW in supply from BHP Billiton’s aluminium smelters, and was spared having to supply 400MW to the country’s platinum sector which is largely out on strike.

There was currently no programme for load-shedding while the emergency supply protocol had also been lifted at 10pm last night (March 6), some 14 hours after national load-shedding had been implemented – a necessary step in order to avoid a national blackout, Dames said.

The load-shedding of March 6 was precipitated by the supply of a batch of wet coal to Kendal from the open cast section of Khutula, a colliery owned by BHP Billiton Energy Coal South Africa (Becsa). The wet coal blocked the conveyors to the installation and forced Eskom to shut down four units.

The change-over in the shift at Kendal on the morning of March 6 saw the mine having to rely on wet open cast fines material as production from the underground section fell to 600 tonnes per hour of coal from the normal run-rate of about 2,200 tonnes/hour.

In addition, there was an unrelated interruption to generators at Majuba power station, said Dames. “So 3,320MW was lost by 5am. That was for us very deep in terms of whether we could make it up,’ said Dames. He said the decision to start rotational load-shedding then became unavoidable.

“We utilised all of our reserves such as open cycle gas turbines,’ said Dames. “By 8am, we had a shortfall of 3,000Mw that we could not make up. To manage the frequency in the national system – to prevent total collapse – we had to implement controlled load-shedding,’ he said.

Eskom first ordered so-called “Stage 3 load-shedding’ which calls for a 20% reduction in order to control demand and supply balance. This was later throttled back to a 10% cut which is “Stage 2’ load-shedding. In the event of Stage 1 load-shedding, users are asked to cut between 70MW and 100MW of power.

However, the prospect of continued rainfall across Mpumalanga and Gauteng province for at least another seven days raises the risk of further interruptions. Dames identified the Duvha and Tutuka coal mines as particularly vulnerable.

Some 900MW would also be lost by end-March as Eskom embarked on the maintenance of the Koeberg 2 nuclear station.

The risk of Kriel power station closing – potentially idling 2,000MW and 3,000MW of power because it had been operating outside regulatory emission conditions – was being tackled with South Africa’s environmental affairs department.

Commenting on the vulnerability of additional coal supplies, Dames identified Duvha because the coal it receives is from the Middleburg open-cast coal, owned by Becsa. Middelburg’s coal is also trucked rather than conveyed undercover.

“The Middleburg mine is an opencast mine; the largest in the southern hemisphere,’ said Dames. “We have to truck coal into Duvha and stockpile where it has been impacted, and will be until the latter part of March,’ he said.

Tutuka, supplied with coal by Anglo Thermal Coal’s New Denmark colliery, Komati, and Grootvlei were also identified as potentially vulnerable power stations. “Tutuka will take us longer to recover and that is related to the mine that supplies it where there is a problem. We are hoping it will catch up,’ said Dames.

Asked how long it would take for open coal stockpiles to dry out, Dames said there was no rule of thumb. “It depends on the drying time; it can be quick or take days. It also depended on the quality of coal.

LONG-TERM

Dames added a sobering note that the risk of emergency power protocols would be with South Africa for a few years yet, notwithstanding the possibility the first 800MW unit at Medupi was due to come on line in December.

“The system will remain tight until completed substantial part of build programme. Certainly over the next few years,’ he said. “You need substantial supply options on the table including a few units from Medupi and Kusile online and then from the IPPs [independent power producers],’ he said.

Dames added that Eskom had continued buying about 1,000MW from IPPs despite having run out of funds from December.

“All the medium-term contracts with IPPs did end. However, Eskom renewed them without all the regulatory approvals. They have been extended to May,’ said Dames who added this had been at risk to Eskom’s balance sheet because the recovery of the cost had not been approved by the public enterprises department.

“We did it at our own risk as we thought it was the prudent thing to do. We did inform regulator, but we don’t have the regulatory approval to recover those funds,’ he said.