Duck curve

The duck curve is a graph of power production over the course of a day that shows the timing imbalance between peak demand and solar power generation. Used in utility-scale electricity generation, the term was coined in 2012 by the California Independent System Operator. In some energy markets, daily peak demand occurs after sunset, when solar power is no longer available. In locations where a substantial amount of solar electric capacity has been installed, the amount of power that must be generated from sources other than solar or wind displays a rapid increase around sunset and peaks in the mid-evening hours, producing a graph that resembles the silhouette of a duck. In Hawaii, significant adoption of solar generation has led to the more pronounced curve known as the Nessie curve. Without any form of energy storage, after times of high solar generation, power companies must rapidly increase other forms of power generation around the time of sunset to compensate for the loss of solar generation, a major concern for grid operators where there is rapid growth of photovoltaics. Storage such as dammed hydropower can fix these issues if it can be implemented. Short term use batteries, at a large enough scale of use, can help to flatten the duck curve and prevent generator use fluctuation and can help to maintain voltage profile. Methods for coping with the rapid increase in demand at sunset reflected in the duck curve, which becomes more serious as the penetration of solar generation grows, include: Installing more dispatchable generation Orienting some solar collectors toward the west to maximize generation near sunset. Energy storage including: Pumped-storage hydroelectricity Battery storage power stations These can be colocated with solar power plants that are designed with DC capacity above their AC rating, or at other suitable sites, including old fossil fuel plants so as to utilize their existing transmission infrastructure (e.g. the Moss Landing Power Plant).