Page 58 - Energize January 2022

TECHNICAL

Information on the aggregate performance of the wind farms Consecutive low days
in South Africa, published on the Eskom data portal is very For the period 03h00 on 3 November 2021 to 13h00 on 5
2
revealing (Figure 9). The graph shows hourly average wind power November 2021 (three days), AWP was below 1200 MW reaching
production (AWP). a low of 24 MW.

Records for other periods over the past year show similar patterns.

This is not a criticism of wind, but a warning that planners will
have to take these occurrences into account. Proponents of wind
are fond of quoting average and maximum figures, but averages
are useless unless minimum values are included. The impact may
be slight when there is a substantial amount of thermal power to
back up the wind, but as wind penetration increases and thermal
power drops, the impact will become more significant, and more
backup power will be required. The most critical areas are those
Figure 9: Hourly average renewable energy production 2 where wind power drops during night-time hours and is the only
source of renewable energy, particularly during the early morning
Most reports on wind concentrate on average and maximum hours when any storage in the network would be at a low level.
values and neglect the lower power production levels. Some of Hopefully, now that WASA is available, the Department of Mineral
these featured in Figure 9 that are of concern are: Resources and Energy will take wind patterns into account in
future REIPPPP windows.
Extreme low points
On 4 November 2021 for the hour beginning 08h00, AWP was References
24 MW. As this is an hourly average the lowest production must 1. R Diab: “Wind atlas of South Africa”, DMEA, 1995.
have been less than this. For the period 07h00 to 09h00, AWP was 2. Eskom: https://www.eskom.co.za/dataportal/renewables-
below 50 MW. The graph also shows several other instances of performance/
AWP falling to low values when solar production was zero 3. SANEDI: “WASA 3 Virtual final seminar”
4. C Mushwana, et al: “Wind and solar PV resource aggregation
Low days study for South Africa”, CSIR, 2016. https://www.csir.co.za/
For the period 07h00 on 9 November 2021 to 08h00 on 10 study-shows-abundance-wind-and-solar-resources-south-africa
November 2021 (25 hrs), AWP was below 500 MW reaching a low
of 235 MW. Send your comments to rogerl@nowmedia.co.za

Wind turbines at sunset (SAWEP)

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