Q$\mathrm{.}15.$ The wind speed at which wind turbine starts delivering shaft power is known as

Q$\mathrm{.}16.$ The radiation spectrum is close to that of a black body with a temperature of about ${?}^{0}K.$

Q$\mathrm{.}17.$ The rate at which direct solar radiation is incident upon a unit horizontal surface at any point on or above the surface is called

Q$\mathrm{.}18.$ In

MPPT technique, it periodically perturbs the operating point of the PV system $($voltage or current$)$ and observes the change in power output.

Q$\mathrm{.}19.$ is a biological process utilized by all green plants to synthesize their own nutrients.

Q$\mathrm{.}20.$ Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of