Solar and wind power warning from the woman preventing Eskom grid collapse

The increased use of solar and wind power in South Africa could cause significantly increased instability in the country’s electricity transmission grid.

If not adapted appropriately, the risk of controlled power outages to avoid a total blackout becomes greater.

That is according to Isabel Fick, the general manager of Eskom’s National Transmission Company of South Africa (NTCSA) System Operator.

Fick gave this warning in a recent interview with Sunday newspaper Rapport.

Her comments echo those of the GO15, an association consisting of large power grid operators supplying over half the world’s electricity.

To understand how solar and wind generation could impact an electricity grid, it is important to know that a grid operates at a specific synchronised frequency. In South Africa, this frequency is 50 Hz.

The frequency is effectively like the grid’s heartbeat. If it goes out of sync, the grid’s health can deteriorate.

When the system’s supply and demand are balanced, the frequency will run at about 50 Hz in South Africa.

If demand outstrips supply, the frequency will drop below 50 Hz. If the opposite happens, it will jump over 50Hz.

A significant deviation either way could cause overloading of transmission infrastructure and eventually lead to a total blackout.

That is why Eskom must implement load-shedding when supply is insufficient to meet demand.

As the general manager of the System Operator, Fick’s primary mandate is to ensure Eskom has a balanced, reliable, and stable transmission system.

While Eskom’s coal-generating fleet has been performing much better than in the past and mostly ensured supply has been able to keep up with demand, the increased use of solar and wind power has created a problem with the timing in grid balancing.

Fick explained that the inertia or inherent delay in large coal power stations has played an important role in Eskom’s ability to maintain a stable grid frequency.

These stations have large turbines that take some time to stop turning after a unit is switched off or suffers an unexpected breakdown.

Solar and wind power plants do not operate with these types of turbines. When their output drops due to less irradiation or lower winds, the impact on the grid is nearly immediate.

That gives the NTCSA little time to react and increase supply from dispatchable generation sources like coal or nuclear power.

As the contribution of solar and wind to the overall supply mix increases, there is a higher likelihood of needing to implement short-controlled power outages to avoid the frequency going out of sync and causing a blackout.

The problem with private rooftop solar

Fick said that behind-the-meter rooftop solar power installations have had a particularly big impact on this front.

During the day, these customers mostly rely on their own generation, but as the sun sets, their output declines.

At the same time, the country’s overall electricity demand picks up during the peak evening consumption period.

“Between 16:00 and 19:00, Eskom’s electricity generation must increase by 4,000 to 5,000MW. That is a massive tempo,” she said.

“Coal power stations cannot pick up output so fast. If they go cold, it can take up to 72 hours to get them running.”

Eskom is already strategically limiting output from utility-scale solar and wind plans to avoid an oversupply of power during particular periods, primarily in the afternoons.

Another way to improve grid stability is to pair renewables with battery energy storage systems (BESS).

Eskom is in the process of rolling out 1,440MWh of distributed BESS across key sites in the Cape provinces and KwaZulu-Natal.

These will be coupled with 360MW of solar power generation and will avoid sudden losses in output.

Fick’s big responsibility

Fick has been at the head of the System Operator since September 2020.

For most of the four years since, the performance of Eskom’s generating fleet has been in decline, resulting in severe load-shedding.

As the division responsible for managing grid stability, the System Operator has been kept on its toes during this time.

Fick’s position requires that she be available 24/7 to respond quickly to any unexpected deviations in electricity supply and demand.

She is also responsible for interfacing with various government departments and examining key infrastructure and capacity expansion initiatives.

Fick previously told MyBroadband that she still considers her job to be exciting and rewarding despite the significant pressure that comes with it.

“The general public may not understand the positive difference when there is real agony and frustration during load-shedding, but my staff do,” said Fick.

“It is the most rewarding area to work in because when you go home, you know you’ve made a difference in people’s lives,” Fick said.