What term describes the ability of a surface to emit stored energy?

The term that describes the ability of a surface to emit stored energy is emissivity. Emissivity is a measure of how effectively a surface can emit thermal radiation compared to an ideal black body, which has an emissivity of 1. This property is crucial in understanding heat transfer and thermal management in various applications, including building design, where materials' ability to radiate heat can influence indoor temperatures and energy efficiency.

In contrast to emissivity, reflectivity pertains to how much incident radiation a surface reflects rather than emits. Thermal emittance is a related concept but specifically refers to the actual quantity of thermal energy emitted by a surface at a given temperature. The Solar Reflectance Index (SRI) is a measure that integrates both reflectivity and emissivity to indicate how a surface responds to solar radiation; it doesn't directly address the emission of stored energy alone.