You can’t manage the weather
Observations support this; the sun can hide behind clouds and wind tends to veer between blustery and still in seconds.
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In practice, solar supplies electricity 30% of the time and wind supplies it 50% of the time. But the demand for power fluctuates so grids are built to handle fluctuation. Building solar and wind farms across a wide area also solves this problem — it might be still in Port Elizabeth, but down the road in Jeffreys Bay, the wind will be howling.
Renewables require a 1-1 back-up
The argument is that, because you can’t manage the weather, renewables need back-up from conventional plants, which means you need to build as much capacity from those as from renewable plants, rendering them pointless. But that is only in a world without smart thinking.
Demand-side programmes, which South Africa has become good at since the 2008 power crisis, can shift energy use to when renewables tend to supply the most electricity. Storage, such as the Ingula scheme, can also save up energy for when it is needed and plants are not being used. Concentrated solar plants also come with their own storage, putting the sun’s energy into molten salt.
Connecting renewables to the grid is too expensive
South Africa’s wind tends to be along the coast, and its optimum solar deep in the Northern Cape. That means an expensive network of pylons has to be built to bring that electricity to cities and factories.
But technological developments mean renewables can be built in less than ideal areas so they can be put up where they are needed.
Renewables destabilise the power system
This is because older wind and solar plants provide electricity in a less stable way than conventional plants, creating fluctuations in electricity supply.
But technology has evolved, creating plants that change their frequency and control their output. These are more expensive. In South Africa, the bidding process has resulted in only the cheapest technology being chosen for wind and solar plants.