The Duck Curve and Solar Energy

The duck curve is said to be solar energy’s greatest challenge. What exactly is it and how does it have an impact on energy prices? Via Vox:

It may seem counterintuitive, but the people who operate the power grid don’t really think of solar power as conventional supply. They can’t control or “dispatch” it on their own schedule. It comes and goes with the sun; they must accommodate it. So from the grid operator’s point of view, more solar (or wind) power looks like a reduction in demand for their dispatchable power.

Total load minus renewable energy is known as “net load.” That’s the target utilities have to hit with their dispatchable resources.

As more and more solar PV is integrated into the grid, it starts dramatically suppressing net load during midday, when the sun is out. The net load curve sags in the middle of the day (like a belly) and then swoops back up when the sun goes down (like a neck).

It’s just like that first load curve I showed you — a peak in the morning, a peak in the evening — only in between, there’s an enormous sag that gets bigger as more solar is added.

At the time, the California Independent Service Operator (CAISO, the operator of the California energy grid) was noticing the same thing. The realized that high levels of solar penetration start generating a net load curve that looks … well, like a duck. Thus, the “duck curve.”

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