Big problems with load limiting
Eskom’s current approach to load limiting will be too costly and take too long to significantly address South Africa’s power crisis.
That is according to former Eskom transmission senior manager Hein Vosloo, who was interviewed for his views about the alternative demand side management intervention.
Vosloo is the main representative of a group of 100 former Eskom engineers and technicians who have offered to assist the utility with improving its operations and combatting load-shedding.
In his discussion with RSG Monitor on Wednesday, 5 July 2023, Vosloo was not as optimistic as the 69% of polled RSG listeners who said they would prefer load limiting over load-shedding.
“If you have not experienced load limiting, but you have experienced load-shedding, then I can easily see why many people would prefer the former,” Vosloo said.
Eskom recently launched its first public pilot of load limiting in certain areas of Fourways, Johannesburg.
Instead of cutting off power during load-shedding, residents are asked to lower their load to 10 amps, or about 2.2kW.
That would require manually switching off power-hungry appliances like geysers, heaters, electric stoves, and washing machines.
In return, they can have their lights and less demanding appliances like TVs, computers, routers, and fridges switched on.
The approach requires that the customer have a smart meter so that consumption can be monitored in real-time.
Example of a smart meter
Vosloo said the first issue with this approach was the high cost of the smart meter.
According to Vosloo, a smart meter costs about R15,000, which would work out to R16 billion in total to cover all technically feasible households.
While customers would not necessarily pay for this unit themselves, the cost would nonetheless have to be carried by consumers in some way — likely taxes.
In addition, Vosloo argues it would take four to eight years to roll out smart meters across the country.
It is hoped and expected that South Africa’s generation shortfall will be fixed in a much shorter timespan, primarily thanks to several gigawatts of private power coming onto the grid.
Even if Eskom and other power distributors could manage a large-scale smart meter rollout, it only aims to reduce grid load by 1,500MW through the entire demand side management programme.
That is equivalent to about one and a half stages of load-shedding.
Vosloo said further logistical complications arise when considering that load limiting requires customers to be home to switch off their appliances and the large volume of SMS messages that need to be sent to customers if they exceed the 10-amp current limit.
Hein Vosloo, former Eskom transmission senior manager. Credit: Solidarity
Vosloo is in ongoing discussions with Eskom about more affordable and feasible options for demand-side management.
Instead of manual load limiting, Vosloo supports the idea proposed by Deloitte director and management consultant Dr Adriaan Davidse.
Davidse has gathered several international businesses under the Ubuntu Power Alliance to develop a small, cheap device that could automate load limiting.
The underlying technology has already been built and trialled in Germany.
Vosloo explained that the device monitors the grid frequency — an indicator of the balance between supply and demand — to determine when the load needs to be curbed.
“If the network is under pressure, the device can shut off some of your appliances for the appropriate period,” Vosloo said.
Vosloo said the major benefits of this system were that it was fully automated and the device cost around R1,000 to R1,500 — substantially cheaper than a smart meter.
By using the grid frequency, there is no need for the device to communicate with a control centre via the Internet.
The grid itself acts as the red flag for when load must be reduced to avoid a blackout.
In theory, instead of cutting power to specific areas over short periods — like with load-shedding — all customers would have their maximum power output curbed until the grid frequency stabilises.
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