JONATHAN DEBASC: The importance of peaking power plants

Peaking power plants play a critical role in stabilising the SA electricity grid by effectively managing fluctuating power demands and preventing the complete collapse of the grid. When there is an unexpected surge in electricity demand, peaking plants provide supplemental power to the grid.

Eskom operates 14 peaking power stations that can deliver 5.9GW of power. Additionally, contracted third parties such as Engie can deliver peaking power capacity when needed. For instance, Engie’s Avon and Dedisa peaking power plants are the country’s first large privately owned power generating plants. Located outside Durban and in Gqeberha, respectively, these two plants together deliver more than 1GW of power, effectively saving the country a full stage of load-shedding.

Both Avon and Dedisa are particularly versatile, being flexible generation plants capable of running on both diesel and gas. A 15-year power purchase agreement with Eskom positions them as the premier privately owned power generating plants in the country. Initially it was intended that Avon and Dedisa would run for two hours a day when required. However, given the complexities of maintaining the grid and other external factors, these plants run over the expected requirements to meet demand. For example, in March they operated for up to 10 hours a day.

When Eskom issues a request for power both of these plants are readily available and reliable enough to meet their intended power supply targets. We take proactive measures to ensure that our facilities are primed and ready to support Eskom in dealing with the ongoing power outages. It may sound simple, but it does not happen without overcoming a few challenges. For example, diesel is more expensive than any other fuel and is used as a last resort. The logistics involved in getting an adequate supply of diesel to the plants can also be challenging.

We share a commitment with many other companies to achieve net-zero emissions and have a strong preference for using gas over diesel in our peaking power plants. However, due to the current availability and logistical challenges of gas in our country, we must continue using diesel for now. Our plants have been engineered for flexibility, allowing for an easy transition to gas as soon as it becomes more accessible and the existing challenges are alleviated.

With the government’s plan to build a liquefied petroleum gas (LPG) terminal at Richards Bay it is expected that the first gas fleet will arrive in the country by 2028. Avon and Dedisa can then be converted to gas operations in less than six months.

Beyond reliance on peaking power stations, battery storage systems also offer flexibility to the grid. The only “fuel” that is needed for batteries is the input power required to charge them. In SA it is relatively simple to find this extra power by harnessing the abundant solar and wind resources we have available. However, their limited storage capacity means they can be depleted quickly, requiring excess capacity for recharging.

With a mature system operator such as Eskom it is possible to make space on the grid for these battery plants. The rapid public procurement of energy storage through the recent Battery Energy Storage Independent Power Producers Procurement Programme showcased both the government and Eskom’s appreciation of batteries as an important part of the energy mix.

Eskom follows a carefully structured order when it comes to managing power supply. It starts with renewables and then the base load power, which is coal. From there the peaking power plants are activated to manage demand spikes during peak usage times. This peaking power happens in a phased approach where Eskom’s 14 peaking power plants are used first, followed by Engie’s two backup plants.

All of this points to a positive future for the grid in SA. Yes, things are taking time, but the transition to always-available power will come sooner than people think. For now, peaking power plants fulfil an important role in ensuring a stable and reliable supply of power to the grid. These plants make a significant contribution to mitigating the risk of load-shedding while helping drive economic growth.

• Debasc is MD of flexible generation for Africa at Engie.