Introduction
Between October 2007 and February 2008 South Africa
suffered major supply interruptions, as load shedding had to be
implemented to manage the energy shortage.
Load shedding is carried out by Eskom, together with redistributors
(municipalities), when the demand for power on the national grid
exceeds the available generation capacity. Failure to manage this
would result in the possibility of massive power blackouts across
the nation. To avoid this, Eskom monitors the demand for power
and sheds (shuts down) sections of the grid to reduce the load
and ensure network stability.
Electricity cannot be stored to act as a buffer against any
unforeseen events. An adequate reserve margin1 acts as a buffer
against such circumstances. With the decline in the reserve
margin the only option available is to reduce the load through
load shedding and reduced demand by customers.
1A cushion of spare capacity that can be used when planned maintenance is necessary and when the system is impacted by unexpected technical faults that demand unplanned maintenance, such as poor coal quality, sudden peaks in demand, or “acts of God”, such as extreme weather conditions. Reserve margin is measured as a percentage of maximum generating capacity.
Why the energy shortage?
From 1996 to 2004, both the private sector and government
felt that Eskom should not build new capacity, although they
were warned that a decision was required by 2000. Government
wanted to bring independent power producers into the market.
Eskom’s low prices, however, dissuaded independent power
producers from investing in the power-generation sector. We
were only given the go-ahead to start building new plant in
October 2004. Taking into account the long lead times to build
new stations, there was not sufficient time to build new power
stations to ensure adequate generation capacity in the short
term.
As a result, Eskom’s reserve margin has decreased to about 8%,
well below the accepted norm of 15%1. When generator units
are taken out of service for planned maintenance2, the lower
reserve margin means that the remaining generator units need
to run harder to meet the demand for electricity. This makes the
units more vulnerable to faults caused by accelerated wear and
tear. As a result, we experienced an increase in technical faults
during this period.
The situation was worsened by a reduction in the quality of the
coal received, which necessitated the burning of increased volumes
of coal for the same output of electricity. The unusually heavy
rains during January and February 2008 also caused production
delays at the collieries. In addition wet coal, which turns to sludge,
created coal handling problems both at the collieries and the
power stations. As a result of these coal problems, a number of
power stations were unable to operate at full production.
Government and Eskom have apologised for these events. We
acknowledge that load shedding is very disruptive and we are
extremely concerned about its impact on our customers. Many
difficult lessons have been learnt.
1 Nersa has recommended a reserve margin of 19%.
2 Planned maintenance is mostly scheduled in the summer months, as
electricity demand is traditionally lower in summer than in winter.
Managing demand
Eskom has the challenge of optimally balancing the supply of, and
demand for, electricity to ensure a more reliable supply of energy
for all consumers.
The solution is to improve the operational performance of our
power stations and at the same time find sustainable short-,
medium- and long-term solutions to the current situation.
A number of initiatives have been implemented such as the
construction of two open-cycle gas turbine power stations
and the recommissioning of three mothballed coal-fired power
stations, and further alternatives are being developed to address
the challenges. Another supply-side solution is co-generation. In
the short term the primary focus is on demand-side initiatives to
reduce the demand for electricity, which unfortunately currently
includes load shedding.
Eskom is confident that it can address the challenges, but
this is only achievable with the support and assistance of
all stakeholders. It is, however, important that emergency
load shedding and other demand reduction initiatives
should be implemented in a transparent manner to fairly
share the load and responsibility among all consumers.
We have developed a set of guiding principles to assist
with the optimal planning and effective execution of
national load shedding:
- maintaining network stability
- integrated national approach to the crisis
- minimising the safety risk
- minimum disruption to our customers and the
community:
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