Key Terms & Concepts — UPSC Mains
Duck Curve
"The steep evening ramp-up in electricity demand that occurs just as solar generation drops off at sunset, now the binding operational constraint on further solar-capacity growth."
The 'duck curve' describes the characteristic shape of a power grid's net-demand curve over a day on a system with substantial solar generation: demand dips sharply during daylight hours as solar output rises to meet it, then ramps up steeply in the evening as the sun sets and solar generation drops to zero precisely when residential and commercial demand peaks. Plotted over a 24-hour period, the resulting curve resembles a duck's silhouette, with the steep evening ramp forming the duck's 'neck'. The duck curve is significant because India's renewable-capacity story has, for a decade, been measured largely in installed-megawatt terms, a metric that overstates a solar project's real contribution to meeting demand, since solar output does not match the timing of peak demand. The steep evening ramp is now recognised as the binding operational constraint on further solar penetration in India, not solar capacity itself, since the grid must be able to rapidly bring non-solar generation or stored energy online each evening as solar output collapses. Mandating storage at the scheme-design stage, as India's 2026 PM Surya Sarovar Yojana does for floating solar (minimum two hours of storage per project), directly addresses the duck-curve problem by letting solar-generated energy be released during the evening ramp rather than only during daylight hours.
A growing GS3 energy/science-and-technology term as India's solar capacity scales; tests whether students understand grid firmness as distinct from installed capacity.
- 1 Describes the steep evening demand ramp as solar output drops to zero at sunset.
- 2 Named for the duck-shaped silhouette of the net-demand curve over 24 hours.
- 3 Reveals that installed solar capacity (MW) overstates real grid contribution, since output timing does not match demand timing.
- 4 Now the binding operational constraint on further solar penetration, not capacity itself.
- 5 Addressed through mandatory storage requirements attached to new solar schemes.
- 6 2026 example: PM Surya Sarovar Yojana mandates a minimum 2-hour storage requirement per floating-solar project.
The mandatory minimum two-hour storage requirement attached to every PM Surya Sarovar Yojana project is a direct response to the duck-curve problem, the steep evening ramp in demand that occurs precisely as solar output collapses at sunset.
