Page 54 - Energize October 2022

VIEWS AND OPINION

The plain man’s view on how to avoid load shedding

by Energesis

022 is reported to be the worst generation, to meet instantaneous demand. In our case there is sufficient generation
load shedding year ever for South capacity on the grid, but much of it is not available due to failure or planned
2Africa. This is reflected by the maintenance. The shortage is said to be as high as 6000 MW at times. Quite simply, what
change from the term load shedding to is needed to end load shedding is sufficient dispatchable power. Now any problem can
“rolling blackouts” in common parlance. be solved by throwing enough money at it, but our problem is finding a solution which
We are however not alone in this, as doesn’t cost too much.
other countries are also experiencing
energy shortages or the potential of Possible solutions
energy shortages. The eastern Australian 1) Bring existing fleet up to required performance standards -this would be first prize.
grid is in a chaotic situation that, facing 2) Provide additional dispatchable power sources. Adding variable energy sources
a record low temperature winter, is will not solve load shedding. Possible sources include additional coal- and gas-fired
likely to get worse. American utilities are generation, and hybrid renewable/storage systems. Adding renewables on their own
warning of power cuts during winter, will not relieve the power deficit in a reliable manner.
and Europe is in all sorts of trouble with 3) Add sufficient storage to allow the existing renewable fleet to become reliably
Russian gas and the coming winter. dispatchable.
Germany will apparently have to resort 4) Add more hybrid wind, solar and storage systems.
to energy rationing. Many countries are
reverting to fossil fuel generation to Solution 1 seems to be impossible in the short term. Solution 2 simply adds more
avoid power failures. generation plant which will stand idle when not used but could replace or displace
The latest round of load shedding older generation plant at a higher availability level. Solutions 3 and 4 seem the most
has resulted in numerous studies and promising as they add new clean capacity which can displace or replace older plant. The
suggestions appearing in the media, all problem with renewables though, is providing dispatchable power at a reasonable or
claiming to have solutions to the load affordable cost.
shedding problem. These range from
plans based on detailed studies, to Concerns
unsubstantiated demands, but all have The concern of the plain man is that adding extra capacity without an increase in demand
the common solution of increasing wind simply means that plant will eventually stand idle for long periods of time, adding to
and solar generation, as well as adding the cost of electricity. However, renewable energy has dispatch priority, and excess
storage into the generation equation. production can be absorbed by ramping down conventional plant or taking it out of
Suggested quantities range from a few service, which should allow more time for better maintenance.
thousand MW to over 10 000 MW of Many of the proposals were constructed using complex models and extensive wind
additional renewable energy provision, and solar databases, and the plain man has neither access to such things or the ability
and from a few thousand MWh to over to use them. There is however, access to a simple set of data, which is very relevant to
24 000 MWh for battery-based energy the recent load shed period, namely the hourly average power generation of all utility-
storage. Most suggest adding gas power scale renewables connected to the grid over the last two months. This set of real data,
to address the variability of solar and from real systems, installed at real sites, operating under real conditions, is conveniently
wind, while others suggest reverting available on Eskom’s data portal https://www.eskom.co.za/dataportal in both graphical
to coal or gas and avoiding renewables and tabular form.
altogether. The government has also The relevance of this data set is obvious if we consider that any new wind or solar
suggested a second SOE to compete with systems will probably be installed in the same areas and therefore should exhibit the
Eskom. One thing to note is that none of same generation patterns. Both wind and solar farms exhibit geographical diversity so
the suggestions carry any guarantee, not any levelling or smoothing due to this effect is already at play in the existing aggregated
even the most complex ones, and neither output. It is safe to assume then that any additional wind and solar would exhibit the
does this article. same performance as the existing fleet. For instance, doubling wind and solar capacity
would simply result in the same curves at twice the level.
What causes load shedding? The problem with many of the studies is that they are based on average values and
The answer is that there is plainly statistical probability models. It is not the average values which will the kill the system but
insufficient generation of electricity, the worst cases, which these studies often ignore. The plain man’s analysis will eschew
specifically dispatchable or firm this involved statistical analysis and modelling and rely simply on recorded fact, namely

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