Offshore wind farms could produce 8-times more electricity than South Africa needs

A study by researchers at Stellenbosch University has found that offshore wind farms along South Africa’s coast could produce up to eight times the current electricity demand in the country.
The research – which was conducted by Gordon Rae and Gareth Erfort and recently published in the Journal of Energy in Southern Africa – set out to establish the Offshore Wind Energy (OWE) resources available to South Africa.
Terrestrial wind farms in the country currently provide around 2,119MW of the total 45,178MW of installed Eskom capacity – around 4% of the total generating capability.
Using data on wind speeds at sea collected by an ever-increasing number of earth-observation satellites, the researchers found that offshore wind turbines could be an essential part of South Africa’s future renewable energy mix.
“Based on the findings of this study, it is clear that OWE has significant potential to play a fundamental role in South Africa’s future power security and decarbonisation strategies,” the research paper said.
One notable piece of data used by the research was the ERA5 climate reanalysis dataset developed by the Copernicus Climate Change Service, which includes data showing the monthly average wind speeds around the globe from January 1988 to January 2018.
This map showed moderate to high wind speeds of above 7 m/s along a strip that circumvents a southern section of the globe, which happens to include South Africa’s coast.
Research has shown that wind speeds of more than 7 m/s make offshore wind energy development economically feasible.
This makes the area a highly viable location for wind farms capable of producing high amounts of electricity.
Turbine array
The researchers constructed models for possible energy output using arrays that would consist of 100 Vestas-V164 8W turbines arranged in rows of 10 x 10 with 10-rotor diameter spacing.
According to their calculations, this density would allow for the generation of 2.974MW/km2, or 2.397 MW/km2 once wind losses were accounted for.
The researchers then used this setup to offer two main scenarios for the rollout of wind turbines – one where the sites would be located in shallow waters with a depth of around 50 metres, and another in much deeper waters where the depth would be 1,000 metres.
In the shallow water scenario, the wind farms could produce around 44.52TWh per year, capable of providing 14.9% of the national electricity demand and powering 4 million households.
While this is already a significant contribution given the current wind energy capacity in South Africa, the scenario becomes far more attractive for deeper sea installations.
With the deep water scenario, an annual generation of 2,387.08TWh can be provided, which could power around 218 million households. This is about eight times the yearly electricity demand as measured by Eskom.
Two additional scenarios included the consideration of a restrictive policy that only permits installation up to 10km away from the coastline, according to the policy implemented by mature European OWE markets.
The table below shows the calculated annual energy production of the proposed installations under the four scenarios.
1 – Shallow water | 2 – Deep water | 1a – Shallow water | 2a | |
---|---|---|---|---|
No wind speed constraints | ||||
Power – before losses (GW) | 11.22 | 360.61 | 2.75 | 342.51 |
Power – after losses (GW) | 9.04 | 290.64 | 2.22 | 276.07 |
AEP (TWh/annum) | 67.13 | 2,520.00 | 19.42 | 2,414.13 |
With wind speed constraints (7 m/s at 100m above sea level) | ||||
Power – before losses (GW) | 7.28 | 340.12 | 2.18 | 328.94 |
Power – after losses (GW) | 5.87 | 274.14 | 1.76 | 265.25 |
Final AEP (TWh/annum) | 44.52 | 2,387.08 | 15.42 | 2,321.54 |
Ideal locations
The study further proposed three optimal locations for wind farm installations, based on a combination of metrics including capacity factors, ocean bathymetry, distance from the existing Eskom transmission grid, and distance to commercial harbours.
The researchers concluded that Durban and Richard’s Bay in KwaZulu-Natal, and Struisbaai in the Western Cape would be ideal spots for OWE development.
The exact locations of the wind farms would be as follows:
- Richards Bay – Within the 10 km coastline buffer and approximately 15 km offshore south of Richard Bay.
- Durban – Within the 10 km buffer and approximately 25 km offshore of KwaDukuza.
- Struisbaai – Within the 10 km buffer zone and approximately 15 km offshore.