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How the City of Cape Town managed to avoid Stage 6 load...

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POWER CRISIS

How the City of Cape Town managed to avoid Stage 6 load shedding thanks to hydroelectric scheme

Cityscape of Adderley street, Cape Town at night. (Photo: Gallo Images / Misha Jordaan)

While the rest of South Africa is being hit with Stage 6 load shedding, the City of Cape Town has offered some relief to its residents through the use of the Steenbras hydroelectric scheme. We unpack why Cape Town residents are currently only experiencing Stage 4 blackouts and what challenges other municipalities face in doing the same.

Stage 6 load shedding, which was last implemented in December 2019, returned this week. It means that most South Africans will go for up to six hours a day without electricity as the national grid sheds 6,000MW in an effort to prevent complete collapse. This was triggered by “unlawful and unprotected labour action” that disrupted Eskom’s operations, the struggling power utility said on Tuesday. 

Read in Daily Maverick: Eskom strike appears to be over after unions call on workers to ‘normalise the situation’

But as South Africans brave the cold winter without power, Capetonians’ load shedding experience will be limited to Stage 4, thanks to the Steenbras Hydro Pump Station.   

How does the Steenbras Hydro Pump Station work? 

The 180MW Steenbras Hydro Pump Station (SHPS) is a pumped storage scheme, which consists of four turbines that are used to generate electricity.  

The City of Cape Town’s Mayoral Committee Member for Energy, Beverley van Reenen, explained that, during peak electricity demand, the pump station channels water from the upper Steenbras reservoir to the lower reservoir through the turbine generator, to create electricity.  

“When electricity usage is low — usually between 11pm and 7am — the turbines pump the water back to the upper Steenbras reservoir to be reused the next day. In this way, SHPS operates like a battery. The amount of electricity that it can generate in one day is limited by the capacity of the lower reservoir,” said Van Reenen. 

How the City of Cape Town managed to avoid Stage 6 load shedding, thanks to hydroelectric scheme
The Steenbras Hydro Pump Station on 12 October 2021. (Photo: Democratic Alliance)

She said that about two-thirds of the water used to generate power during the day is pumped back to the upper Steenbras reservoir at night, “to create more space for continual utilisation of the power station”. In this way, the scheme works akin to charging a cellphone battery at night for use the following day.  

“Currently, we use Eskom power to pump water back to the upper reservoir  in order to create space for generating the next day. It is also technically possible to accomplish this using other modes of supply if reasonably priced,” said Van Reenen. She added that the city was looking at storage facilities for independent generation additions. 

Cape Town is the only South African city to own and operate a large pumped hydroelectric scheme, said Van Reenen.  

“Regular maintenance and good management are imperative to ensure that this power station works well and can be used to offset high tariff and demand periods, as well as to protect city-supplied customers from stages of load shedding where possible,” she said.  

To ensure that the city is able to protect its customers from the current Stage 6 load shedding, it also garners energy from the gas turbines during the evening peaks (between 5pm and 8pm) to bolster the capacity of the Steenbras-generated reserves, Van Reenen explained.  

The Steenbras Hydro Pump Station. (Photo: Democratic Alliance)

How much protection does Steenbras offer? 

The City of Cape Town, by operating the Steenbras hydroelectric plant at full capacity, is currently able to offer city customers up to two stages of load shedding relief where it is possible — in other words, Stage 4 rather than Stage 6. 

“Depending on the reserves, the city can buffer its customers for the most part of the day by adding power, generated from the gas turbines during the peak times at night, especially when demand is great,” Van Reenen told Daily Maverick.

She added that, between January and May 2022, the city protected its customers through the use of the Steenbras Hydro Pump Station with one stage of load shedding, amounting to roughly 514 hours, or 21 days of protection. 

At this stage, the City of Cape Town is capping its customers at Stage 4 load shedding.   

“The City is looking at the scenarios for stages higher than Stage 6. However, the higher the stages, the greater the risk. If Eskom is on the verge of total collapse of its network, city mitigation efforts would likely not be enough,” Van Reenen said. 

Read in Daily Maverick: Pushing the limits: Why load shedding puts even more pressure on an ageing electrical system 

Is Cape Town the only municipality shielding its residents from heightened stages of load shedding?  

Yes. Cape Town is the only municipality with a hydroelectric pump scheme that can be switched on to mitigate the energy shortage, said Chris Yelland, energy analyst and MD at EE Business Intelligence. 

“A coal power station, like in Johannesburg’s Kelvin Power Station (the City of Johannesburg gets about 10% of its power from the station), you can’t switch on 200MW at the flick of a switch. You have to start up a boiler, fire up the boiler and get the water boiling at the right temperature, the steam pressure up. So it takes an hour or two hours to even just ramp up; by that time the load shedding is over. So Kelvin is absolutely useless for actually being able to, on command, switch power on and off. It can’t do it,” Yelland said.  

He said it would be difficult for other municipalities to have a hydroelectric operation like Cape Town’s, as hydroelectric schemes require specific geographic conditions such as mountainous areas. 

Democtatic Alliance leader John Steenhuisen visits the Steenbras Hydro Pump Station on 12 October 2021. (Photo: Democratic Alliance)

Could other municipalities buy from independent power producers (IPPs) to shield their residents from load shedding?  

In 2019, the City of Cape Town took the government to court in an effort to get the state to allow the municipality to procure power from IPPs. The case was dismissed. About a year later, President Cyril Ramaphosa said in his 2020 State of the Nation Address, that municipalities in good standing could start procuring energy from IPPs.  

Yelland said the City of Cape Town has now put out tenders for IPP energy. The City of eThekwini is seeking to procure 400MW of electricity from IPPs, while the City of Johannesburg announced last year that it planned to wean off the Eskom grid by adding an extra 500MW alternative energy mix consisting of gas and solar. 

Read in Daily Maverick: ‘Give me 18 to 36 months’, says Joburg mayor Mpho Phalatse to residents buckling under endless blackouts 

What challenges could municipalities face in procuring energy from IPPs to limit load shedding? 

Yelland said metros are worried about the energy crisis and aren’t necessarily looking to move off the Eskom grid completely, but rather to supplement Eskom electricity with reliable and renewable energy. However, this may be more difficult for smaller metros or those that have not had clean audits.  

Daily Maverick previously reported that only 41 of 257 municipalities, or 16%, had clean audits, with the rest of SA’s municipalities reported to not be making significant strides towards achieving a clean audit. 

Read in Daily Maverick: The good, the bad and the shocking: A visual gauge of the financial state of South Africa’s municipalities 

“The municipalities are all concerned, certainly the big metros. The smaller metros, quite honestly, don’t have the balance sheets and resources; they’re not creditworthy enough to enter into a power purchase agreement with an IPP. You do need to be creditworthy. I mean, the guy who spends billions of rands building an IPP plant wants to know that the company is going to buy this and that they’re creditworthy to the extent that they’ll get paid for the electricity at the end of the month,” Yelland said. DM/OBP

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  • Under current circumstances, I would like to know if the many residents that have solar power systems could make a small but valuable contribution to the grid. One of my pet hates are the new Smart Meters that prevent residents storing excess electricity in the grid. This electricity would give residents a credit and at the same time the grid would have the use of it. But no…? Laws that were ignored in the interests of those busy looting at every opportunity are still disregarded or have been thwarted. Municipalities make a lot of money out of electricity and have a vested interest in smart meters and controlling prices to their advantage. But who is benefiting when so many are corrupt?

    • Helen, if you want to see insanity in action have a look at my factory complex. We generate more MWh per day than we consume. Not so when grid is off. Then, our solar has to be off. So we have this madness that without loadshredding I would have contributed excess to the grid, but because of loadshredding I burnt R9000 worth of diesel. Definition of madness.

  • This (relief from extent of loadshredding) is pure nonsense! Pumped storage is CONSUMPTIVE, not generative and it consumes 240MWh to fill after providing 180MWh. The system is tiny, shifting less than 10% of the city peak demand. CPT has absolutely no own generation, it fills that 240MWh with energy while the entire country is being shred. If they were refilling with own generation they would have half an argument. At best a pumped storage can provide relief for one two hour loadshredding event worth. Then it is empty and refilling places that much extra demand on the whole system. Getting relief over days of continous loadshredding is insane. I have battery storage that (1) is much more efficient (2) I fill from solar power. Nobody comes around giving me relief from loadshredding.

    • Good for you with your self reliance but as a resident of Cape Town I do not regard as “pure nonsense” the fact that Cape Town residents who are supplied via the City ‘suffer’ one or two lower stages than Eskom customers elsewhere.
      Mind you it helps to have elected a party to govern us which takes its responsibilities seriously.

    • Sounds like sour grapes to me. And load “shredding”, really? Once is a joke, twice is corny, after that give it a rest, dude.

  • While Steenbras was built long before the DA came into power, well done on them for making sure it is well maintained! No doubt it would be falling over regularly if the ANC were in charge of it!

  • Viva Cape Town! Viva DA! OK, we are lucky to have the mountains and a thinking party in the hot seat. Other cities will have to make do with solar or other alternatives.

    My advice is act now, on the municipal level AND on your personal level, get a SolarPV system!

  • Two points to note – firstly, the City of Cape Town does not supply all residents with electricity, there are many who are on Eskom directly, and who don’t benefit from the Steenbras scheme. Secondly, the Steenbras scheme was built decades ago and funded by national government. Its nothing new and it isn’t a DA achievement. Perhaps their achievement is to have kept it running.

    • Yeah never mind that the DA didn’t build it, if there’s a chance to take the credit they will.

      Having said that, if it had been left up to the ANC it would have fallen into disrepair laong ago.

  • The article should mention that ESKOM has two pumped hydro stations (Ingula and Drakensberg) that are 20 times bigger than Steenbras. They have helped to limit loadshedding at national level.

    In the early 2000s, ESKOM proposed to build another large PS station in Limpopo but this (together with other generating projects) was blocked by national government. There are a number of other sites in SA where similar stations could be built which would provide far cheaper long duration storage than Lithium batteries. And storage is essential in electricity systems that have large proportions of wind and solar renewables.

    Australia has recognised this and, ironically, a lead contractor in the consortium building its big Snowy 2 pumped storage project is Clough, subsidiary of South African listed construction company Murray and Roberts.

    So maybe it’s time to bring our expertise home?!

  • Does anyone know if there is an opportunity to build a parallel pump storage scheme adjacent to the existing one? By opportunity I mean is there geographical space, not money or political will or any other somesuch. If there is, when will it be started?

    • We don’t even have enough money or political will to build a dam to supply _water_ for the chronically short W Cape though. So whether or not there’s enough space to build another pumped storage scheme is a moot point.

  • For an explanation of how wrong this reduced stage thing is: CPT demand is about 2000MW – yes it varies during day. Under stage 6 they must give up about 8h. That means they must drop total demand by 666MW in ANY hour of loadshredding stage 6. (the 666 drops according to how many hours what stage). If CPT entered loadshredding with a full dam, that 180MW would help them for 16 MINUTES of only the first hour of loadshredding. Then it is gone, exactly how my battery is empty when it’s empty. Refilling my battery after my area’s time slot does not help the national shortage UNLESS we fill my battery with solar. Filling from grid merely moves my demand from my areas allotted shredding period to another period. So if I was a 200kW user then after my loadshredding slot I become a 250kW user for the next four hours. Achieves zero assistance at grid level! What is happening here is even worse : instead of shredding 8 hours under stage 6, the city shreds 6 hours under a claimed stage 4 so now they reduce by 500MW (fewer areas at a time or less often) instead of 666MW – basically that is like pretending they run perpetually full Steenbras. :/

  • Johannesburg and surrounds are ideally situated to instal pumped storage, not because of geography but because of the mining legacy of the area.
    It would not be a difficult thing to use pumped storage using the underground works of abandoned mines as reservoirs, with at least two options appearing obvious. Firstly shallow mines can be used as storage reservoirs and deep mines as receivers with the generators installed between the two. Secondly any of the mines could be used if surface reservoirs are to either be built or to be used from existing pans, dams or surface storage structures. These concepts could be rolled out in either small, medium or large scale pumped storage. This would also serve to assist the smoothing of power generated through solar plant, where this could then be stored for high demand times.
    The problem of acidified water is the largest single challenge to this but as this is a problem which has to be addressed in any case the solution could be offset against power generated.

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