“Big Batteries” officially known as Battery Energy Storage Systems (BESS) are becoming the unsung heroes of the energy transition. Think of them as giant rechargeable power banks for the grid: they absorb excess energy and release it when it’s needed most.
As we tackle the enormous challenge of climate change, technologies such as BESS are playing an increasingly important role.
In this article, we’re addressing the common myths we hear and presenting the facts you need to know.
First of all – what is a Big Battery, also known as a BESS?
A BESS is a technology that uses a group of batteries to help stabilise the electricity grid by balancing energy supply and demand, storing surplus energy and delivering it when required.
As defined by ESKOM: “BESS, or Battery Energy Storage Systems, stores electricity in batteries for on-demand power supply.”
Myth #1: “BESS are only useful for solar and wind energy.”
While BESS are commonly paired with solar PV and wind projects, they also support grid stability, peak shaving, frequency regulation, and backup power for a wide range of energy sources. Because BESS do not rely on conventional rotating generators that require time to ramp up or ramp down, and instead use power‑electronic inverters, they can adapt their output almost instantaneously. This allows them to respond far more quickly to supply‑demand fluctuations than conventional coal‑fired or gas‑fired power stations.
For example, ENGIE is developing the large‑scale hybrid facility in South Africa known as OYA Energy, which integrates a 92MW/242MWh Battery Energy Storage System with wind and solar generation.
The surplus energy stored may come from solar PV during sunny periods, wind generation during windy conditions, or from conventional generation sources that cannot reduce their output further.
Although batteries are often associated with small‑scale or residential systems, utility‑scale BESS support the entire electricity system, regardless of the energy source involved.
Myth #2: “Batteries degrade too quickly to be worthwhile.”
Many people associate battery degradation with their personal devices, such as cellphones that lose capacity after a few years. However, the batteries used in large‑scale BESS operate under completely different conditions and management strategies.
Utility‑scale BESS include sophisticated battery‑management systems designed to monitor and optimise the performance of every cell. As a result, many systems come with warranties exceeding 10 years, and modern chemistries such as LFP (lithium iron phosphate) can even offer warranties of up to 20 years.
Manufacturers rigorously test their systems before deployment and provide detailed lifetime performance data to companies like ENGIE. While some gradual reduction in capacity over time is expected, this is accounted for during project design and the systems remain economically worthwhile to operate.
Myth #3: “BESS are too new and unproven.”
BESS technology is not experimental. It has been operating reliably around the world for well over a decade.
Countries such as South Korea, Germany, and the United States have deployed large‑scale BESS since the early 2010s, with continuous improvements in performance, cost, and system design. Each new installation contributes to a global learning curve, making modern systems more capable and more cost‑effective.
In South Africa, this proven performance is demonstrated by the operations of the OYA Energy Hybrid Facility. As one of the country’s pioneering hybrid projects combining wind, solar PV and BESS, OYA plays an essential role in strengthening South Africa’s power system and supporting grid reliability.
Conclusion
To ensure a smooth and resilient electricity transition in South Africa, it’s important to separate fact from fiction. Battery Energy Storage Systems are already demonstrating their value by supporting grid stability, improving resilience, and helping the national grid system work more efficiently. Ongoing advancements in technology, combined with projects like OYA, highlight the expanding role of BESS within South Africa’s energy mix.
