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Taming the Duck: Solutions for Renewables Integration

Ken Boyce
By Ken Boyce, PE Director, UL

As renewables are increasingly integrated into the energy infrastructure, we continue to gain deeper appreciations for both the benefits and challenges they present. The challenges, highlighted in the so-called “Duck curve” first identified in the solar-rich California market, show how disruptive solar power can be for grid stability.

As the sun comes up, power demand increases; however, so does production of electricity from solar panels. Solar production generally increases throughout the day, and large-scale solar assets can dramatically reduce the grid demand. This net result forms the duck’s belly. As daytime hours end, solar production wanes while commercial demand remains steady at the same time people increase their demand for electricity as they arrive home, all forming the duck’s neck. More solar power means a deeper belly and a steeper neck, constituting significant challenges for the grid in balancing and meeting rapidly increasing demand in the afternoon.

In some markets, the “duck” imagery is replaced by other frightening creatures. For example, in places such as Hawaii, higher solar penetration and higher residential power bases correspond to an even steeper and taller neck, leading to the “Nessie” curve named after the famous Scottish mythical beast. In developing countries, a “Shark” curve is sometimes used to describe the sharp increase in the early evening from load shedding of unmet, largely residential, loads. And Germany has faced the condition where the entire national demand was met for a time by renewables, which turned power prices negative—and while no animal name has been assigned to this phenomenon, it highlights the important need for grid balancing solutions.

Additional renewables deployment is good for many reasons. Finding ways to balance the grid and meet human needs remain essential for continued success. Fortunately, technological progressions are significantly supporting both objectives, helping to control both the depth of the duck’s belly and the slope and length of its neck by empowering energy consumers with more local control.

First, increased deployment of solar plus storage has positive benefits to mitigate these effects. Energy storage systems store electricity when it is being generated—for example, by solar arrays during the day—and allow it to be used when desired. Complementary effects of solar plus storage can be seen as we consider both reduced daytime solar grid overgeneration and reduced demand rates in the evening. This solution can be implemented in the form of a single energy storage system, for example in a home or commercial building, or in the form of a microgrid that uses more systemic control over a larger campus or community domain.

Solar production generally increases throughout the day, and large-scale solar assets can dramatically reduce the grid demand. This net result forms the duck’s belly.

Increasingly sophisticated grid technologies are also positively influencing this issue. Advanced technology inverters, sometimes called “smart inverters,” can react in predetermined ways to support grid health. As these more sophisticated inverters are deployed in California, Hawaii and other markets, we are seeing a more holistic approach to coordinated grid health across the population of distributed energy resource assets.

Building energy technologies continue to advance the ways that energy can be used in an efficient and coordinated manner. Buildings no longer need to be just loads, but are being transformed into grid collaborators. They can reduce demand when the grid is challenged and are able to accomplish that in ways not apparent to people within the buildings.

Implementing an intelligent energy future is critical for the global society. The important work being done to safely accomplish that in different global markets, by best leveraging advancing technologies, will let us tame the duck (and his friends).

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