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The notorious "duck" curve is no obstacle to solar energy grid integration, thanks to some fancy footwork by the US Department of Energy's National Renewable Energy Laboratory.

Clean Power

US Lab Combats “Duck” Curve, Touts Solar Energy Grid Integration

The notorious “duck” curve is no obstacle to solar energy grid integration, thanks to some fancy footwork by the US Department of Energy’s National Renewable Energy Laboratory.

solar energy grid integration duck curve

It seems that nothing went President* Trump’s way last week, and that includes his messaging in support of coal miners. Despite Trump’s oft-repeated expressions of love for “clean” coal, his own National Renewable Energy Laboratory somehow decided that last week would be a good time to remind the public that more solar energy is coming soon to a grid near you.

What About “Clean” Coal?

The solar energy announcement came on February 26, barely one month after Trump officially stated that “we have ended the war on beautiful, clean coal.”

Coincidentally, last week also brought some bad news for “clean coal” fans, in the form of an investigative article in The Guardian alleging a coverup of cost-overruns at the notorious $7.5 billion Kemper “clean coal” plant in Mississippi.

Those problems predate the Trump administration (Kemper was supposed to be former President Obama’s “clean coal” showcase), but now Trump is left holding the bag.

Kemper gave up on “clean coal” and switched to gas during Trump’s first term, following the ill-fated FutureGen carbon capture project into the dustbin of clean coal history.

Meanwhile, the Petra Nova CCS project in Texas is functional but does not appear to represent a commercially viable solution.

So, clean coal is all dressed up with nowhere to go. Analysts are already predicting that the aging, rapidly dwindling fleet of US coal power plants will continue to shrink in 2018, and this spring the US coal industry is set to lose a coal mine as well.

CleanTechnica was among those convinced all along that clean coal is a hoax, which makes last week’s happy talk about solar energy all the more significant.

NREL Goes (Solar) Duck Hunting, Bags A Big One

Taxpayers and ratepayers could be on the hook for the Kemper debacle, but on the plus side, the US public has been chipping in for solar grid integration research, and it looks like all that hard work is about to pay off.

Last week’s solar announcement from NREL involves conquering the infamous solar “duck” curve.

The duck curve was long thought to be a serious obstacle to solar grid integration. Here’s NREL with the explainer:

“… On days characterized by the duck shape—in particular, during sunny spring afternoons when demand is low and solar generation is high—system operators could actually have to turn off, or curtail, some of the solar power, because conventional plants can’t be stopped and started quickly enough to accommodate it. That could mean higher costs—and ultimately limit PV’s environmental benefits.”

Ouch! The credit for identifying the duck curve challenge goes to NREL, because back in 2008 researchers at the lab first noticed the phenomenon while studying how to plan for large-scale solar grid integration. They didn’t call it a duck back then, but if it walks like a duck and quacks like a duck, then you know the rest.

→ Regarding duck curves, we have to recommend this CleanTechnica piece from a deep duck expert: What About Florida? Energy Efficiency, Solar Energy, & Regulatory Backwardness In The Sunshine State — Part 7: Using Efficiency, Solar, & Storage To Hunt The “Duck Curve”

NREL also gets a pat on the back for recognizing the potential of solar energy in the nation’s electricity supply before it was a thing. Back in 2008 grid integration basically meant wind energy, because solar costs were prohibitively high. Here’s NREL again:

“… NREL analysts saw the potential for dramatic solar cost reductions, and believed it was important to examine the implications of achieving such cost reductions on deployment and systems operation.”

Those predictions certainly bore fruit in terms of plunging solar costs. By 2013 grid analysts and other stakeholders were tackling the duck curve with gusto. As solar costs dropped the pressure was on for NREL to deliver even better solutions, and that resulted in a landmark 2015 paper enabling more solar grid integration through two pathways:

“The first is to ‘fatten’ the duck, growing its belly by increasing the flexibility of the power system—which means changing operational practices to enable more frequent power plant cycling, starts and stops, and so on. The second is to ‘flatten’ the duck, shrinking its belly by shifting supply and demand so solar can meet parts of the load that wouldn’t normally be provided in the middle of the day.”

Reassuringly, NREL adds that the technology for “flattening the duck” is already at hand and is being deployed in the US, namely energy storage and demand response.

Right Back At You, Coal Fans

NREL leaves the public with this message:

“So fear not: the duck curve doesn’t spell doom for variable renewables.”


“… thanks to more than 10 years of forward-looking grid integration analyses from NREL, grid planners and operators have access to a wealth of data, analysis, and tools to help get their proverbial ducks in row to manage it.”

Dozens of cities, counties, and one entire state — Hawaii — are already committed to 100% clean power.

The growing community choice aggregation movement is giving energy consumers more power to push for solar energy and other renewables on the grid, and that may help things along.

Meanwhile, we’re not hearing much about communities clamoring for more coal power. If you hear anything different, drop us a note in the comment thread.

Follow me on Twitter.

*As of this writing.

Photo credit: Susanne Nilsson via, creative commons license.

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Written By

Tina specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Views expressed are her own. Follow her on Twitter @TinaMCasey and Google+.


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