Thinus receives funding from Eskom for small research projects through the Tertiary Education Support Programme (TESP). He is affiliated with Stellenbosch University and holds shares in two energy-related university spinouts, namely Bridgiot and GreenX Engineering. His research is predominantly sponsored by MTN South Africa through https://mtn n.ac /
Arnold Rix receives funding from Eskom for small research projects through the Tertiary Education Support Programme (TESP). He is affiliated with Stellenbosch University and supported by Scatec as an industry partner.
South Africans are facing another round of power cuts despite promises from South Africa''s power utility, Eskom, that it would keep the lights on. Unexpected breakdowns and scheduled maintenance at various generation plants have been blamed for reduced generation capacity. These have compromised the stability of the national power grid. Since this affects everyone in the country, The Conversation Africa invited Thinus Booysen and Arnold Rix to explain what the power grid is and what keeps it stable – or not.
The grid is made up of three building blocks: generation, transmission and distribution.
Generation consists of power stations (or plants) that generate electricity. Examples of these are the newly built Kusile and Medupi power stations. South Africa has a generation capacity of approximately 58 GW – enough to power 26 million kettles concurrently – mostly made up of Eskom''s coal-burning power plants. Eskom''s share of this is a generation capacity of 44 GW, of which 38 GW is from coal-powered stations.
Transmission comprises the 28,000 km of high voltage lines that transport electricity at high voltage levels (such as 400 kV or 765 kV) to cities and towns.
There, it branches out to 325,000 km of lower-voltage lines that distribute electricity to homes and businesses. In comparison, New Zealand has 150,000 km for a tenth of South Africa''s population and the UK has over 800,000 km.
The transmission lines and distribution lines therefore connect the generation plants and users in a network that collectively form the grid, which operates at a synchronised alternating current frequency of 50Hz.
All generating plants, including coal-burning plants, solar farms, wind farms and hydro-electric plants, are synchronised and interconnected in this way. All turbines running in power plants must run in unison, and all renewable sources must fall in line.
The electricity in a house''s plugs is also synchronised to the grid. This includes plugs (and light sockets) all over the country and beyond South Africa''s borders in countries that it sells electricity to.
Like a heartbeat, this 50 Hz oscillation keeps the grid alive. It allows electrical power to flow from the numerous generation plants and spread throughout the country to the places where it is needed.
Unfortunately, due to the backlog of maintenance of older Eskom plants and mismanagement during the development of newer plants, the generation capacity of Eskom often dwindles. With an average plant age of 40 years, breakdowns and maintenance have amounted to as much as a 20 GW loss in generation capacity.
Read more: South Africa''s electricity supply: what''s tripping the switch
Demand management includes efficiency interventions such as replacing electric water heaters (geysers) with solar thermal water heaters, replacing lights with energy-efficient versions, or more direct approaches like turning off all water heaters with ripple control.
Unfortunately, increasing supply is a time-consuming and capital intensive process. It takes years and billions of rand to build a new coal-burning power plant. Also, coal is the reason South Africa is one of the worst emitters per capita in the world. Installing renewable generation plants, such as solar or wind, is easier, faster and less expensive per energy unit. The challenge is that renewable energy is weather dependent and therefore the generation unpredictable.
When the amount of power being used (demand) starts to exceed the amount of power generated (supply), the frequency of the grid starts to fall slightly, as the turbines struggle to keep up. This is similar to your blood pressure dropping when you start to exercise. Your heart, the generator in your body, quickly starts to increase the rate at which it supplies blood to stabilise your blood pressure and supply oxygen where it is required. If your heart can''t keep up you black out as a protection mechanism to give your heart a chance to catch up and restore functionality in your body.
If the electrical demand starts to outstrip supply, the generators'' speed will drop below 50 Hz and the built in protection will disconnect the generator to keep it turning. This means that there''s less generation connected to the grid, so more generators will disconnect. Eventually all the generators disconnect one by one as their supply cannot meet demand.
A cascading event like this would happen quickly (seconds), leaving the network with no generation.
To avoid a collapse of the grid, Eskom, which controls the grid frequency from a National Control Centre in Johannesburg, has put in place a severe form of demand management for situations in which demand starts to outstrip supply. It imposes a series of planned power cuts – called load shedding – to reduce demand. If the situation is extremely bad it institutes Stage 4 load shedding, which means 4GW of the total demand is cut on a rolling schedule.
It hasn''t happened in South Africa yet because of Eskom''s well-coordinated and responsive demand management – and good fortune.
Such a collapse of the grid would require generation plants being brought back online in synchronisation with the 50Hz, which means they have to be ramped up and added one by one. The reconnection of all the generators after a blackout would probably take two weeks or more, leaving large parts of the country and some neighbouring countries without electricity for days or more as plants, and limited critical demand, are gradually turned on.
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To replace fossil fuels (coal, natural gas, oil, etc.) in the global energy mix, decarbonized electricity is the only solution. Alongside nuclear power, which is available in certain countries, new capacities in renewable energies (solar, wind, hydropower, etc.) must be deployed rapidly and extensively.
In Africa, where electrification remains limited, the challenge is even more formidable. Despite its immense renewable energy potential, the continent currently contributes minimally to the global electricity mix. In 2019, only 2% of new capacity came from Africa, even though its energy demand is expected to double by 2040.
To address this, the local production of essential equipment and innovation are undoubtedly key to accelerating Africa’s energy transition and maximizing its potential. These advances will enable the development and modernization of electrical networks, making them stronger and more efficient.
Modernizing the electrical grid is essential to the energy transition. Electricity accounts for 25% of global energy, and it took 100 years to build the grid that achieved this level. We must accomplish the same in 20 years, as electricity will account for 50% of energy by 2050. This poses two main challenges: the first is expanding and modernizing the grid by building new cables, and the second is fostering innovation.
Africa faces a significant industrial challenge.
According to the International Renewable Energy Agency (IRENA), electricity is expected to reach 50% of final global energy consumption by 2050. Renewable energy (solar, wind, and hydropower) is anticipated to account for 80% of new capacity by 2040.
Like other regions, Africa must innovate to achieve its energy transition, yet it must first expand its local industry. Doing so will enable the establishment of new ecosystems vital for this transition (creation of specialized companies, partnerships, skill-building, development of new trades, etc.). The International Energy Agency (IEA) notes, for example, that although Africa has the world''s largest solar resources, it currently holds just 1% of installed solar capacity.
To electrify Africa and accelerate renewable energy production, networks must increase their power capacity, requiring the development of innovative cables. Superconducting cables, for example, can transport large amounts of energy to urban areas while minimizing costs and interference with other networks (due to cable shielding). Their high capacities and efficiency represent a major technological leap compared to traditional copper and aluminum cables. Medium-voltage cables are also essential to Africa’s transition, supplying electricity to industrial plants, hospitals, schools, and shopping centers.
Africa''s existing networks, like those worldwide, are often decades old. This can create challenges in terms of maintenance, resilience to climate events, and fire risk. Older infrastructure can also complicate the integration of new renewable capacities. To extend their lifespan and improve reliability, networks must be modernized or even transformed, requiring collaboration with energy producers and network operators who play a vital role in maintaining infrastructure.
Projects must adopt environmental standards to reduce greenhouse gas emissions and minimize the ecological impact of the energy transition. This necessitates collaboration with qualified companies (in circular economy practices, eco-design, etc.) and the establishment of stringent project criteria, including environmental standards in calls for tenders.
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