Power cuts make no sense


The Citizen (KZN) - - Front Page - Hil­ton Tar­rant works at YFM Hil­ton Tar­rant

At­tempts to pause load shedding dur­ing peak traf­fic in­tro­duces un­nec­es­sary risk.

As the pos­si­bly of per­ma­nent round of stage 2 load shedding kicked in at the end of Jan­uary, Eskom at­tempted to en­sure that there would be no load shedding dur­ing the morn­ing peak (6-9am).

At the time, it said this was “an ef­fort to min­imise the im­pact on traf­fic”. In the first week of Fe­bru­ary, it also at­tempted to en­sure that load shedding would be ar­ti­fi­cially halted from 4-6pm to “ease traf­fic con­ges­tion”.

Eskom said: “Sus­pend­ing load­shed­ding dur­ing the peak traf­fic hours is a pi­lot pro­gramme aimed at achiev­ing an ap­pro­pri­ate load shedding phi­los­o­phy for the coun­try. As this is not pos­si­ble every day, it will be con­firmed each day, de­pen­dent on the risk based on the avail­able ca­pac­ity and emer­gency re­serves on the day.”

Aside from the inanity of de­scrib­ing this as an “ap­pro­pri­ate load shedding phi­los­o­phy”, there are sev­eral prob­lems with this short-lived plan.

First off, load shedding is a func­tion of the short­fall be­tween de­mand and avail­able sup­ply.

Given stub­bornly high plant break­downs, the in­abil­ity to forgo planned main­te­nance any longer, as well as higher-than-av­er­age de­mand, Eskom is sim­ply not able to meet cur­rent de­mand.

Emer­gency re­serves – pumped stor­age schemes and (diesel-pow­ered) open cy­cle gas tur­bines (OCGTs) – are be­ing used to keep the lights on, while main­tain­ing an ap­pro­pri­ate op­er­at­ing mar­gin.

Eskom can­not use every megawatt of sup­ply it has at a given point in time in case units trip.

Fol­low­ing a strat­egy where it ar­ti­fi­cially halts load shedding dur­ing peak traf­fic hours cre­ates a hugely prob­lem­atic pub­lic mis­con­cep­tion that Eskom can con­trol load shedding.

Just days into Eskom’s “pi­lot pro­gramme”, it was un­able to “pause” load shedding due to a short­age of gen­er­at­ing ca­pac­ity.

The peak time pe­ri­ods for traf­fic also con­flict di­rectly with metro, municipal and Eskom-di­rect sched­ules across the coun­try.

Some run four-hour blocks, oth­ers two-hour ones. Most start and end on even hours (4pm, for ex­am­ple), but some start and end on odd hours. This means the “pauses” di­rectly con­flict with lots of municipal sched­ules.

Also, how does a mu­nic­i­pal­ity or metro plan to im­ple­ment – or not im­ple­ment – load shedding based on no­ti­fi­ca­tions from Eskom that ar­rive at 10pm the pre­vi­ous night or later?

Oper­a­tionally, try­ing to halt load shedding for two, three or five hours a day in­tro­duces a mas­sive and un­nec­es­sary risk.

It can­not mag­i­cally gen­er­ate the as­sumed 2 000MW short­fall at 6am or at 4pm. There is a grad­ual build-up of ca­pac­ity, es­pe­cially when it comes to coal baseload plants. Only emer­gency plants (pumped stor­age and OCGTs) can pro­vide power rel­a­tively in­stantly, and Eskom needs to try and keep this prover­bial pow­der dry.

There is zero in­tel­li­gence to load shedding sched­ules, save for the City of Cape Town’s de­ci­sion to not load-shed in the City Bowl.

Rather, we rely on dog­matic Ex­cel spread­sheets that stack blocks in a sys­tem­atic pat­tern across the days of the month. This is an “at­tempt” to make load shedding “fair”.

To min­imise the im­pact of the near-per­ma­nent load shedding that will be re­quired over the next 12 to 18 months, it needs to be en­tirely pre­dictable.

Met­ros and mu­nic­i­pal­i­ties around the coun­try need to know ex­actly what to ex­pect, and when.

Pic­ture: Bloomberg

PROB­LEM­ATIC. Eskom’s plan to ar­ti­fi­cially halt load shedding dur­ing peak traf­fic hours cre­ates the mis­con­cep­tion that it can con­trol load shedding.

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