What the Heck is a "Duck Curve"?

What the Heck is a "Duck Curve"?

Good question, and one that we expect to hear more frequently asked in the near future.  According to Greentech Media, CAISO, California’s grid operator, first referred to the "Duck Curve" in 2013 in a report about the state's changing energy balance. The report included a net load graph with curves resembling the profile of a duck floating in the water. Net load low point was midday and represented by the duck's body, but then curved upward, similar to the neck of a duck, in late afternoon and evening as energy demand increased and solar supply decreased.

In short, California's data brought to light that changes in load-supply balance are becoming more significant. But what's causing the drop and rise? Indicators point to utility-scale solar installations.

And what about "Nessie"?

An even steeper curve is Hawaii's "Nessie Curve", which resembles the silhouette of the Loch Ness Monster. In Hawaii, 10 percent of energy comes from rooftop solar. As explained by John Trotti in Forester Daily News, "Lorraine Akiba, Commissioner with the Hawaii PUC, described what her state’s utility planners term, the Loch Ness Curve produced by grid disruptions resulting from the island state’s increasing solar PV generation that on occasion drives systemwide energy supply to a greater value than its demand (underwater) during peak solar times of the day."

So, where the Duck's net low load point stays "above water" during peak solar times, Nessie's does not. And, Nessie has a much steeper curve upward later in the day.

Here is a "big picture" explanation: Solar only generates power when the sun is shining. It is challenging for utilities to incorporate this power into the grid and they prefer the steady base load power from coal and natural gas plants. 

One solution to creating better balance? Energy storage. Hawaii is already installing grid-scale battery systems. There are several new companies and existing companies in a race to develop improved batteries, to drive the prices down, and to improve the integration into the grid. North Carolina alone has 84 companies involved in battery storage or component manufacturing according to Charlotte Business Journal and Area Development reported that Alevo is expanding their battery manufacturing facility in that state. Additionally, the German manufacturer of batteries for commercial and residential energy storage, Sonnen GmbH, is setting up a manufacturing facility in Atlanta (Bloomberg).

Should there be more government support for energy storage research and development? Let us know what you think.