Solar Exposure Flashcards
The ratio of total-reflected to incident electromagnetic radiation. It is a unitless measure indicative of a surface’s diffuse reflectivity.
Albedo
The density of light hitting the surface; amount of radiation per unit area.
Incidence
The angle formed between sun and the earth’s surface.
Sun angle
Takes local topography into account in regard to the angle formed between the sun and the earth’s surface.
Ground-sun angle
The angle between the Sun’s rays and an imaginary line perpendicular to the collector’s surface. An angle of 0 means the Sun’s rays are perpendicular to the collector surface.
Solar Incidence Angle
Solar gain: solar energy absorbed by a surface.
Maximum solar gain for a given intensity of sunlight is achieved when the incidence angle is 0, that is when the suns rays are perpendicular to the surface. This is because the cross section of light is not spread out, and also because surfaces reflect more light when light rays are not perpendicular to the surface.
Solar Heating
- Orientation towards solar radiation
- Measured in N, S, E, W and 4 sub increments
- Useful when combined with slope data
Aspect of Slope
Measure of a surface’s ability to reject solar heat, as shown by a small temperature rise. It is a combination of surface reflectivity and the ability of a warm or hot material to shed heat in the form of infrared radiation.
Materials with the highest Rating are the coolest choices for surfacing materials. Due to the definition, particularly hot materials can even take a slightly negative value, and particularly cool materials can even exceed 100.
Solar Reflective Index (SRI)
Cities and urban areas are 3 to 8 degrees warmer than surrounding areas due to the heat island effect. This temperature difference is attributed to buildings and pavements that have taken the place of trees and vegetation. Trees and vegetation give off water (transpiration) that evaporated and cools their surfaces and surrounding air.
Urban Heat Island Effect
