Duck Curve is coming for solar power in SA – Gadget

In South Africa, the conventional wisdom is that the pace of residential solar installations has saved the electricity grid from collapsing. But there is a counterargument: Solar has distorted the demand curve so much that it has created new, costly challenges.

This mystery is explained by a phenomenon called the “duck curve.” First identified in California, it is a graph illustrating the effect of solar generation on electrical load.

Solar energy peaks around noon, due to abundant sunlight, which leads to a huge drop in demand for electricity from the grid. This drop in the demand curve creates the “belly” of the duck.

When the sun sets and solar production ceases, there is a sudden increase in demand for electricity from the grid. This lifting of the curve creates the duck’s “neck.”

This, in turn, means utilities must quickly increase their use of other energy sources.

“It’s a natural occurrence in any high-penetration solar market,” says Jon Kornik, CEO of “smart energy” company Plentify, which makes electricity management hardware and software. “All this rooftop solar is meeting daily demand and, in a place like California, exporting excess energy to the grid.

“They have grown to such a scale that the amount of solar energy exported to the grid covers daily demand. While this may sound good, it is detrimental to usability. Their task is to maintain the balance between the demand and supply of electricity during the day. They do this by using various combinations of energy generation. At the bottom they have baseload generation, usually the cheapest generation, but also very slow on and off – usually a few weeks.

“In South Africa, with our coal-fired power stations, you can’t just turn these guys on and off. They take weeks to get up and running and then you have mid-range generation and then you have peak generation, which is quicker to get up and running but is very expensive, like gas turbines that run on diesel.”

“As the duck curve gets deeper and deeper, it starts to eat into the underlying supply. You have to rely more on peak power, especially when the afternoon ramp gets steeper.”

The result: the cost of generating power for utilities becomes more expensive as it relies less on low-cost generation.

“Consumers see electricity rates going up and think rates are going up while solar is going down, so ‘fuck it, I’ll go off the grid.’ They install solar power, making the problem worse for the supplier and everyone else still connected to the system.

“This is fueling what is known in the industry as the utility death spiral that many utilities have been subjected to.”

Kornik cites data on average monthly electricity consumption for different income groups in Cape Town, which shows that the highest-income households have seen demand fall sharply year on year.

“This should terrify utilities because they are the most valuable customers who buy the most electricity and generate the greatest margin, which in turn is used to subsidize basic electricity for people on the other side of the spectrum.”

What is particularly frightening, Kornik says, is that the Cape Town data he cites shows a shift from 2018 to 2019, before the solar revolution began.

There is an antidote. This is called load management and inspired the founding of Plentify.

“If storage can be coordinated, it can be another resource for the grid. This is what California has started to do really effectively. As a result, the duck curve is now starting to flatten.”

Load management combines “load reduction, peak demand management, and robust load building.”

The end result: demand is shifted from costly peak hours to the middle of the day.

*Arthur Goldstuck is CEO of World Wide Worx and Editor-in-Chief of Gadget.co.za. Follow him on social media at @art2gee.