RICHARD HALSEY: Revised electricity infrastructure plan must admit benefits of energy storage

As the government concludes a much-delayed revision of the Integrated Resource Plan (IRP) for electricity infrastructure there is one technology that can offer multiple benefits to SA’s struggling power system and shouldn’t be underrepresented in the new proposal — energy storage.

Strategically located energy storage can help optimise the use of the existing transmission grid. While this is just one of many benefits it can provide, it is an important one for the government to factor in when deciding how much storage capacity to procure at the national level.

Electricity supply is not just about generating enough energy, but also about transporting it across the grid to where it is needed. The grid has limits to how much electricity can be supplied within an area at any time, and current grid constraints are now widely recognised as a bottleneck in implementing solutions to the electricity crisis.

For example, the greater Cape region has excellent wind and solar resources for renewable energy power plants but extremely limited capacity to connect new power plants to the grid before 2027. Energy storage can help with these grid constraints.

For a solar plant with a maximum output of 50MW Eskom will allocate 50MW of grid capacity 24 hours a day. On a cloudless day the output from the solar panels will increase from sunrise to reach maximum output at about midday, then reduce until sunset. This means the 50MW of grid capacity will be fully used for a short period each day.

Adding ample energy storage means additional solar capacity can be built and fully used by storing surplus power generated during the day to be used later in the day when solar generation drops. This stored electricity can then be discharged in the evening and at night as required, resulting in much more electricity being supplied within the existing grid allocation over the same duration, compared to before the storage was added.

While pumped hydro is an established form of energy storage in SA, its extended construction times — five to eight years — are too long to address short-term grid constraints, and it can only be built in locations with suitable geography and water supply. In contrast, batteries are improving in capability, becoming more cost effective, and can be quickly deployed in most locations.

In many cases batteries could be added long before grid capacity would be expanded, making battery storage a viable way to squeeze more out of the existing grid while the network is expanded over time. This is part of the reason Eskom’s latest Transmission Development Plan (TDP) 2022 has increased its recommendation for batteries compared to previous years. Eskom now suggests 4.4GW batteries by 2027 and 5.75GW by 2030.

Though Eskom maintains and manages the grid, it is the department of mineral resources & energy that is responsible for calculating the amount of energy storage to procure nationally. Its IRP is still the official electricity infrastructure development blueprint, and the current IRP from 2019 allocates much less battery capacity to 2030 than the Eskom TDP 2022. The risk is that if the updated IRP 2023 remains a power system model to balance supply and demand, without factoring in grid benefits, it will fall short of installing enough battery storage capacity at a national level for maximum system benefit.

Some independent power system models for SA indicate even more battery capacity by 2030 than the Eskom TDP 2022, without even considering grid benefits. Either way the message is clear that SA needs substantially more battery capacity than is now included in the IRP 2019.

There are further important considerations to optimise battery deployment, including location, type, chemistry and duration — that is, how long they can supply their maximum power output. There is also a need to look at how to further develop local battery supply chains to increase local content and manufacturing in the longer term. In these areas several academic, industry and independent actors are already working on analysis and solutions, but often in parallel to government and state-owned entity work, meaning these insights and ideas may not be incorporated into national plans.

To develop best the IRP 2023 and an overall energy storage strategy for SA there should be a collective effort from the department, Eskom, the electricity minister and multiple other energy stakeholders to pool their skills and wisdom. This collaboration is required for the optimal utilisation of battery storage and other technologies to ease the electricity crisis as soon as possible.

• Halsey is a policy adviser on the SA energy team at the International Institute for Sustainable Development.