As a potential means to transition away from fossil-fuel-based electricity generation methods and towards greater decarbonisation of its energy mix, independent system modeller Clyde Mallinson this week said South Africa needs to build energy storage solutions to bridge the gap between when renewable energy is produced and when it is not to meet daily and peak demand.

Speaking during a webinar on the system benefits of energy storage on October 27, he said South Africa’s peak hourly electricity demand was 34.1 GW, while its average hourly demand was 26.4 GW.

For reference, Mallinson pointed out that the state of California, in the US, had a peak hourly demand of 63 GW and an average hourly demand of 32.5 GW. Texas, also in the US, had a peak hourly demand of 81.5 GW, while its average hourly demand was 47.2 GW.

This, he alluded, meant that the difference between South Africa’s average and peak demand could more easily be met with storage systems that used surplus power generated during off-peak times as a means of bridging the supply and demand gap.

Mallinson added that South Africa had “exceptional” wind resources, to the extent that within a 24-hour period, there was never an instance in which there was no wind resource.

He also pointed out that, with solar photovoltaic (PV), besides at night, there was also never a period when there would be no solar resource to use, highlighting that South Africa had strong solar irradiance, even during times when it was severely overcast.

Therefore, he proposed an electricity system that produced 1.65 times more than what South Africa’s current generation capacity was, using mostly solar PV, supplemented by wind and backed up by storage solutions.

Ideally, this system would comprise 101 GW of solar PV, 40 GW of wind and 35 GW (312 GWh) of storage capacity, which would mean as much as 155 TWh of so-called “super power” was produced.

Super power, Mallinson explained was any surplus power produced during times of lower demand, which would be fed into storage systems to use during peak times.

This decarbonised electricity system would produce South Africa’s currently required 231 TWh of demand, resulting in 155 TWh of super power.

However, to get to this point would require an investment of about $71-billion.

Some of the different types of energy storage solutions that could be used include: conventional electrochemical and flow batteries; pumped-storage schemes; high-temperature thermal storage; super capacitors; compressed air, hydrogen and cryogenic storage; mechanical gravity storage and electric-vehicle-to-grid storage systems.