GRID CONSTRAINTS Energy storage can be a huge part of the solution to SA’s power crisis
Considering the devastating effects of prolonged load-shedding it is hardly a surprise that the government has declared a state of disaster.
What does surprise, though, is that energy storage (including utility scale batteries) receives relatively little attention in the array of solutions being considered, when it could play an important role in solving SA’s electricity crisis.
President Cyril Ramaphosa announced in 2022 that "improving the performance of Eskom’s existing fleet of power stations" topped the list of actions to solve the electricity crisis. The problem is that Eskom’s coal fleet has been in a state of decline for more than 15 years. Even the utility’s most recent system adequacy outlook report "expects a downward trend in plant performance to continue in the medium term".
Many of the units are nearing retirement age and will be shut down soon anyway, despite continued political support for coal.
The second action was to "accelerate the procurement of new generation capacity". Energy analysts widely agree that SA needs a huge rollout of renewable energy as the lowest-cost, least-carbon and fastest-to-build technology.
However, in December the crippling extent of grid constraints was laid bare when not a single onshore wind project in the Eastern or Western Cape was awarded against the 3,200MW allocation, because the grid was unable to support this new generation capacity. To take stock, fixing the coal fleet is not going to save the day and new power plants cannot be added as fast as required until we ease grid constraints. But energy storage can help this conundrum.
Energy storage can provide a wide range of services, but in a constrained power system, where Eskom is battling to balance supply and demand, a subset of these services is particularly important.
To begin with, grid-located energy storage can help make the best use of existing coal plants.
By storing excess energy at times of lowest demand, such as late at night, and discharging at peak demand times, the amount of power required from the generation fleet during peak time can be reduced. This functionality is nothing new — Eskom has been using pumped storage dams in this way since 1981.
What has improved dramatically in the past few years is the capability and cost competitiveness of batteries.
Eskom has recognised this, and its latest transmission development plan (TDP) of 2022 has tripled the allocation of batteries required by 2032 compared with TDP 2021. Construction at the first site of Eskom’s battery energy storage system project began in December.
Under near continuous load-shedding, when there may be no excess supply, energy storage can still function to "smooth out" load-shedding. Rather than stopping load-shedding at night, Eskom can continue to shed consumer load and use that supply to charge pumped storage dams. While this application may give more hours of load-shedding over a 24-hour period, it reduces the severity of load-shedding during the hours when consumers need electricity most.
For example, imposing stage 3 load-shedding all day in an area is less disruptive than stage 6 during office hours and nothing at night.
The City of Cape Town is often able to use the Steenbras pumped storage facility to reduce load-shedding stages relative to the rest of the country.
What’s more, energy storage can maximise the use of existing grid infrastructure. For example, a 100MW solar farm is allocated a grid connection that reflects its maximum possible output (100MW) for 24 hours a day, even though it does not use all of it during the day, and any of it at night. With smart and considered adjustment of the rules, more solar and energy storage could be built at this site without increasing the 100MW grid allocation. Here, the storage allows excess generation that the grid cannot accommodate at the time of production to be stored until the grid can handle it.
Moving on from optimising existing infrastructure, energy storage helps integrate new renewable energy facilities by allowing them to supply power at a wider range of times.
In some circumstances (such as congested municipal grids), energy storage could be a cheaper solution compared to grid upgrades.
To sum up, energy storage can help a struggling power system in several ways, providing increased resilience and flexibility. It is not something that is only required in a system with a high proportion of renewable energy.
While there are lots of energy storage technologies, batteries are leading the charge due to cost reductions, improved capabilities, high efficiency, fast response times, scalability, minimal location restrictions and multiple possible revenue streams.
Since developing grid-located storage cannot be done overnight, the government should also envisage short-term solutions. For instance, 2022’s action plan acknowledged the need for private investment in generation capacity and for businesses and households to produce their own power from solar photovoltaic (PV) systems. These actions can be performed fast, and in many ways are the most effective way to ease load-shedding in the short term. Once again, the batteries are critical — a solar PV system will only supply power during the day, but with a battery the consumer has a far longer time frame in which demand for Eskom supply is reduced.
As more consumers become less reliant on Eskom, the utility will be more likely to meet the remaining demand with its supply, and therefore reduce load-shedding.
In response to load-shedding, the wave of consumer battery installations is gathering speed. However, there is still much work to be done, particularly around the rules and tariffs for consumer feedback of power into the network.
Grid-located energy storage can assist the electricity system in many ways, but rollout is way behind schedule. The government planned to bring 513MW of energy storage online by 2022, but the request for proposals was only released earlier in March.
There are three clear actions the government can take to turn this around. First, update policies, legislation and regulations to create a more enabling environment for grid-located energy storage. Second, collaborate with Eskom and municipalities to develop optimal strategies for deployment. And third, engage with the energy storage industry on how best to support implementation.
Halsey is a policy adviser on the SA energy team at the International Institute for Sustainable Development.