Increasing the share of renewable power in SA’s energy mix to 85% by 2050 would provide a “least-cost energy mix” for the country, according to the latest study that challenges the arguments of those who push for more coal or nuclear power.
Energy modelling work by David Rodda and Adam Balusik, both researchers and lecturers at the University of Witwatersrand, shows that a system dominated by nuclear energy could make electricity prices about 60% higher than a predominantly renewables energy mix.
Installing 100GW of wind and 62GW of solar energy to replace coal power would result in a least-cost energy mix of R1.01 per kilowatt hour (kWh). A primarily nuclear mix with 27GW of nuclear energy would cost R1.67/kWh.
These findings were presented by Rodda and Balusik at the Actuarial Society of SA’s recent public interest seminar. They reveal a clear choice for SA’s energy future, demonstrating that a renewable energy-led system is the best option for the country in terms of cost, reliability and environmental impact. They question the assumptions of those who advocate for more coal or nuclear power, saying taking such a policy stance would lock SA into a high-carbon, high-cost and high-risk energy future.
The researchers modelled the cost implications and supply dynamics of different technology options for SA’s energy mix by 2050. The modelling also considered the emissions and water use implications of different energy mix scenarios.
According to Rodda, 84% of SA’s energy mix is supplied by coal-fired power stations. If the country maintained the same mix the cost of electricity, at today’s prices, would amount to about R1.50/kWh.
“We need to choose a mix that can provide sufficient electricity throughout the day. The choice of energy mix also must take into account environmental sustainability and protect citizens from high inflation in electricity costs,” said Rodda.
Assuming demand of 380TWh a year, compared with current demand of about 220TWh, and assuming pre-Russia/Ukraine war energy commodity prices, they found that not only could a renewables-led system provide sufficient electricity to meet minimum demand but this would also be the cheapest option.
The one scenario, modelled on the trends suggested in the Integrated Resource Plan 2019, in which they assume renewables will account for 70% of the energy mix by 2050 — and given actual performance of installed coal and renewable capacity — shows a levelised cost of electricity of about R1.52/kWh. This includes the system being supported with about 24% of electricity supplied by generation from gas- or diesel-powered plants.
The least-cost mix, delivering electricity at a levelised cost of electricity of R1/kWh would require about 100GW of wind, which would have to be installed at a rate of 3.5GW per year, and 62GW of solar photovoltaic, which would need to be installed at 2GW per year.
Renewable sources will then contribute 85% of the total energy mix. To ensure steady supply during times when there is too little wind and sunshine, this scenario includes 44GW of gas or diesel generation capacity to provide peaking support.
However, by replacing some of the gas or diesel power with about 20GW of battery storage, the cost could be brought down to 98c/kWh.
At peak performance times, as much as 150TWh would need to be curtailed from renewable generation plants and this energy could then be used to manufacture green hydrogen, said Rodda.
The study echoes the recommendations of the presidential climate commission (PCC), which calls for a rapid and ambitious expansion of renewable energy sources to address the energy crisis and to align with global efforts to combat climate change. The PCC has recommended that SA should add 50GW-60GW of renewables by 2030.
The PCC said that all the models it reviewed to draft proposals for the revised IRP show that a least-cost energy model would be made up of investment in variable renewable energy sources (wind and solar), storage (batteries and pumped hydro) and peaking support. None of the models build new coal or nuclear.
Rodda and Balusik’s model shows that an energy mix dominated by nuclear would be the most expensive option. This scenario assumed adding about 27GW of nuclear power, 29GW of wind and 18GW of solar power alongside existing coal-fired generation capacity. The cost of such a mix would be about R1.67/kWh.
The department of mineral resources & energy announced recently that it plans to issue a request for proposals for 2,500MW worth of new nuclear energy projects. This will be in addition to the 1,800MW Eskom hopes to secure by extending the life of Koeberg nuclear power station in Cape Town by 20 years.
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