LETTER: Two ways to deal with variable power

South Africans are learning that just increasing electricity generation will not “solve” our power crisis. It is as important to deliver that electricity where and when it is needed.

Isabel Fick, Eskom’s general manager of systems operation, is therefore spot on when she highlights the challenges of variable supply and demand (“Eskom coal fleet now ‘more variable’ than renewables”, September 14).

While the present challenge is the unreliability of Eskom’s coal-fired stations, variable renewables are already aggravating the problem. After load-shedding, domestic solar systems draw heavily on grid power to recharge their batteries — often adding to the system load at the worst possible time.

There are two solutions. First, domestic users must pay higher time-of-use and capacity tariffs for the privilege of using the public supply as an occasional top-up. On a longer timescale, SA will need more grid-scale storage to deal with increased variability.

We have been spending billions of dollars importing lithium batteries to back up solar panels. But these offer just a few hours of storage. Meanwhile, Eskom’s pumped storage stations, which can supply about 2,800MW for almost 20 hours, are providing vital stability to the system. And they are far cheaper per megawatt hour of energy stored.

Last week in an SA Academy of Engineering seminar we highlighted the need for more attention to be given to electricity storage. Specifically, we recommended that urgent action be taken to restart Eskom’s Tubatse pumped storage project in Limpopo.

This would provide more and cheaper grid-scale storage than lithium imports. It would offer supply security for an increasingly renewable-heavy grid during periods of still, cloudy weather while providing other grid services such as black-start capabilities. As important, it would provide jobs and development opportunities in one of the poorest parts of the country.

It is the kind of transformational project that could take SA forward into a more sustainable future. But building it will take longer than simply importing batteries from abroad. We need to start sooner rather than later.

Mike Muller 
Johannesburg

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