When an electric grid includes significant amount of solar energy (more than 100% of circuit minimum daytime load), it becomes more challenging for local utilities to stably match supply and demand for electricity. The term Nessie Curve or "Duck curve" refers to the shape of the curve of grid demand over the course of a day, which resembles the Loch Ness Monster. Solar energy is produced almost entirely during the midday and electricity demand typically peaks in the late afternoon or early evening. This leads to both a small "hump" of on-grid demand in the morning, and a much larger peak in the evening. This in turn creates a problem for local utilities, who must quickly ramp-up electricity production when solar energy generation decreases later in the day at the same time that demand is typically increasing.
Solutions
The problem of supply and demand mismatch is not new. One potential solution is to optimize photo-voltaic solar systems to produce later in the day. Currently, most systems face southward (in the northern hemisphere) in order to maximize insolation over the course of the year. However, if panels were faced westward they would produce more electricity as the sun is setting (and demand is highest). Otherwise, another possible solution is for energy produced earlier in the day to be stored (either through batteries, reverse hydroelectric water pumping, or some other method).