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ECONOMIC REPORT OF THE PRESIDENT

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Box 7-4: Supporting Increased Penetration of Variable<br />

Energy with Smart Markets and Storage<br />

The two most rapidly growing renewable energy technologies,<br />

wind and solar, come with unique operating characteristics. The variable<br />

nature of their production profile creates new challenges for management<br />

of the electric grid, as compared to traditional generating resources<br />

with a more dispatchable output profile. For example, when considering<br />

the timing of output from wind and solar, the net electricity load, which<br />

is the demand for electricity less wind and solar generation, can exhibit<br />

a “duck curve”—where the low net load in the middle of the day ramps<br />

up quickly as the sun sets before trailing off as demand ebbs later at<br />

night—looking much like the neck, head, and bill of a duck. The figure<br />

below plots this curve for an illustrative spring day in California. We see<br />

that current levels of variable energy resource (VER) penetration begin<br />

to create this duck shape, increasingly so for future years, when VERs are<br />

projected to increase.<br />

Gigawatts<br />

28<br />

Figure 7-i<br />

Net Load for March 31<br />

24<br />

20<br />

16<br />

2016 Actual<br />

2012<br />

12<br />

8<br />

2017 Forecast<br />

Est.<br />

2020 Forecast<br />

Est.<br />

4<br />

0<br />

0 2 4 6 8 10 12 14 16 18 20 22<br />

Hour of the Day<br />

Source: CAISO.<br />

In addition to the unique net load profile created by variable<br />

renewable resources, wind and solar output exhibits more idiosyncratic<br />

variation as compared to traditional resources, a feature that also creates<br />

additional grid management needs.<br />

480 | Chapter 7

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