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Polity
Article by: Tracy Hancock
Published: 25 Aug 2011
Increased summer demand a challenge for Eskom’s maintenance season
State-owned power utility Eskom reported on Thursday that planned outage requirements for its summer maintenance season would exceed the available capacity, resulting in the use of costly liquid-fuel open-cycle gas turbines. This would increase reliance on demand side management.

At Eskom’s third state of the system quarterly briefing of the year, Eskom CEO Brian Dames said this year’s summer electricity demand was generally higher than that previously experienced.

He explained that planned plant outages were ranked according to scope and risk, to prioritise the available capacity.

“Therefore, lower risk outages for inspections and interim repairs have to make way for high-risk, high-pressure pipe-work replacements, low-pressure turbine blade inspections and major refurbishment outages,” explained Dames.

Meanwhile, all deferred outages would be monitored for increased risk until they could be accommodated.

He said Eskom had the capacity to meet the increased demand, but needed adequate reserves during the maintenance period. South Africa’s reserve margin improved from 14.9% last year to 16.8% this year. However, on its own, the reserve margin did not provide any indication of the capacity available for maintenance.

Some maintenance was undertaken during winter, owing to a lower than expected growth in demand of 1.4%. Initially, Eskom estimated a 2% growth in electricity demand, compared with last winter.

To date, the peak demand for the year, including non-Eskom generation, was 37 064 MW at the end of May. This was marginally higher than the 36 970 MW peak in 2010, but lower than Eskom’s forecast of 37 500 MW for this winter.

Electricity demand decreased by 113 GWh during the first quarter, owing to strikes in the metals and mining industries, relatively brief winter cold snaps and weaker than expected economic activity. Large power users also reacted to Eskom’s higher winter tariffs, decreasing their electricity consumption. The peak winter tariff was 3.5 times higher than the summer peak tariff, while the average winter tariff was 2.5 times higher than the average summer tariff.

From July 24 to August 1, Chamber of Mines coal mining members faced strike action, which caused 1.8 days of coal stock to be lost.

Minister of Public Enterprises Malusi Gigaba said the coal miner’s strike and its potential impact on Eskom’s fuel stocks was of concern. Stockpiles dropped from a 38-day supply before the strike, to 36 days by the end of the strike.

“Eskom is busy rebuilding its stockpiles to enter the rainy season with some confidence of fuel adequacy,” he said.

The utility hoped to grow its stockpiles to ensure a 40-day supply by the third quarter.

As a result of the mining strike’s impact, Eskom aimed to increase the amount of coal sourced during this financial year, to maintain stock days at the projected levels, from an initial four-million tons of additional coal to an additional five-million tons of coal.

Further, coal-related production losses were reduced by 26% for the first five months of the year compared with last year.

Dames said that no national load shedding was experienced this winter; however, local distribution interruptions took place in certain regions. Severe weather conditions, such as snowstorms and heavy winds, caused short supply interruptions in parts of KwaZulu-Natal and the Eastern Cape, with the utility’s Majuba power station, between Volksrust and Amersfoort, in Mpumalanga, being cut off by snowfall.

A further challenge faced this winter came in the form of local outages caused mainly by overloading and illegal connections in densely urbanised areas; however, the strategy to combat illegal connections and electricity theft was showing results, he stated.