‘Eskom has to burn diesel to keep lights on’

Eskom still needs to use emergency reserves, including hydropower and diesel, to keep its open cycle gas turbines (OCGTS) running to avoid load-shedding because even with significant uptake of renewable energy, power shortages remain during morning and evening peak demand times.

This is according to independent energy specialist Ken Gafner, who said that although there is about 5 000 megawatts of renewable energy, such as solar photovoltaic rooftop systems and wind power relieving some stress on the national grid, this is not enough to solve South Africa’s energy crisis.

“There is obviously a significant amount of renewable energy coming on board in wind and solar, but unfortunately wind and solar don’t help you in the morning and evening peaks because they are not entirely dispatchable,” he said.

“Solar is just taking a bigger chunk out of the centre of the day and leaving the peaks as they are, and creating more and more of a problem for the utility because you can’t just ramp these power stations up and down.”

Gafner said an “ideal solution” to the problem would be for the Eskom generation fleet to perform better and to also source energy from independent power producers who could run liquified natural gas (LNG) powered plants to provide electricity, rather than relying only on burning diesel.

Although natural gas is a fossil fuel, it is cleaner and more cost-effective than diesel, and is regarded as a transition fuel towards a low carbon future.

“The country needs a very significant amount of peaking power. If you need three or four hours in the morning and evening, there is no easy way to do it, and batteries are certainly not going to be the solution on the scale that is needed,” Gafner said.

It takes about one litre of diesel to generate four kilowatt hours of electricity, but the huge cost of loadshedding to the economy far outweighs how much is spent on diesel to keep the lights on, he said. Gas is also a more reliable and stable fuel than renewables during peak hours.

“The cost per kilowatt hour is around R7 per kwh using diesel, which is a tenth or less than that lost to the economy for every kilowatt hour not delivered,” Gafner added.

The National Energy Regulator of South Africa (Nersa) similarly argued in its multi-year price determination for 2023-24 and 2024-25 that should the use of open cycle gas turbines be limited to a 1% load factor, the cost to the economy would be R236 827 million and R236.1 billion, respectively, compared to R16 852 million and R17 723 million spent on diesel generation.

“The cost to the economy far outweighs the cost of running diesel. This is not meant to encourage the unabated use of OCGTS but rather to give a perspective of the damage load-shedding has on the economy and the well-being of citizens,” Nersa said.

It costs about 75 cents per kwh to generate power using solar energy and between R1.30 and R1.50 per kwh using a new coal-fired plant, Gafner said, noting that renewables are not dispatchable (always on) power and require additional technology modifications to make them dispatchable, which comes at a cost.

In essence, a green non-dispatchable energy source is not the same as a dispatchable source, which includes gas, coal, nuclear and hydro technology.

“Generating electricity with diesel costs about four times as much as generating with coal,” Gafner said, adding that the government also needs to offer security of gas and energy supply to independent power producers bidding for plants to motivate investment.

In addition, the conversion of parts of Eskom’s ageing power plant fleet — most power stations are more than 30 years old and nearing end of life — to LNG gas-powered operations is also part of the solution as identified in the energy blueprint, the Integrated Resource Plan for the energy sector.

“If a plant has got six generation sets, you could decommission three sets and repower half of the plant with gas. This is a simple solution because power evacuation permitting and fuel logistics are in place.

“Equally important, when you are looking at shutting down a plant, is there is a whole town and surrounding area dependent on it. But if you replace the plant with gas you can keep staff employed on gas that were employed on the coal side,” he said.

Energy expert and former Eskom executive manager Vally Padayachee said open cycle gas turbines would form an essential part of the energy mix until the entity had established a reserve margin (commonly known as “headroom”) of 10% to 15% above peak demand of, for example, 33GWH in winter.

“Eskom’s leadership, including the new board, has improved maintenance and planned maintenance. I am of the opinion that you can still get good life, although not unlimited, out of these old power stations,” said Padayachee, who is also a former senior executive at City

Power Johannesburg. “In this crisis situation you have got to keep the coal-fired fleet going, even though some are limping along, because you can’t solve this problem by having renewables on the grid. We support renewables but they are nondispatchable technologies; they are not-always-on.”

Padayachee said the last time there was stage six load-shedding, in February, it was partly because there was no renewable energy on the grid.

“We had no sun shining and no wind blowing at the time, so we relied on the increased use of open cycle gas turbines. There must be a mix of technologies between renewables and non-renewables,” he said.

The improved load-shedding situation over the past month had been aided by solar photovoltaic energy and lower demand of 23GW to 25GW, but this would rise to 33GW in winter, he added.

Eskom still needed to use its emergency reserves of hydropower and open cycle gas turbines but this came at a cost, although the entity was burning less diesel now at a lower load factor than it was at this time last year.

“Eskom has been pushing open gas turbines to the hilt for the last two years. Although we went through significant load-shedding last year we were still using OCGTS, otherwise we would have gone beyond stage six,” Padayachee said.

“Our concern is that the OCGTS must not fail now. If they collapse we will go back to load-shedding at increased levels.”

Padayachee said another “critical risk that could come back and bite us” was that Eskom does not have a reserve margin, which is excess megawatts of 10% to 15% capacity above peak demand, according to global energy norms. This gives the system operator breathing room if units go off the grid for planned or unplanned maintenance.

“It should be 10 to 15% above 33GW in winter. In 2002 we had 20% reserve margins, we had that luxury. Until we get to a decent reserve margin we will have this risk because the grid is still unstable and erratic.”

Padayachee said that although Eskom has improved its energy availability factor (EAF) from about 50% to about 65%, there is still a lot to do to reach the 70% to 75% EAF a year goal to be out of the woods.

“Until we get to a decent reserve margin open cycle gas turbines will have to be in the energy mix. It is a balancing act. Do we get to stages four, five or six load-shedding and mess the economy further or do we keep the lights on? I am not saying it is the best way. We are between a rock and a hard place.”

‘Do we get to stages four, five or six load-shedding and mess the economy further or do we keep the lights on?’