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Radiation
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Introduction#
Radiation analyses are a pair of two different metrics that relate to the irradiance received at a point from the sky. The point in time irradiance measures the irradiance received from a localized sky at a specific point in time while the cumulative radiation analysis measures the received amount of radiation from a localized sky during a specific time period.
Radiation analyses can assist in many parts of a design process, like evaluating shading systems to reduce risk of overheating or optimise the location and orientation of solar panels to increase efficiency.
Set Up#
The radiation analyses use shading masks and a sky to evaluate the different metrics.
Shading Masks#
Shading masks are used in all radiation metrics as they describe the relationship between the sky and the positions that should be evaluated. A shading mask is created by mapping the light paths from an analysis point to the sky patches described in a hemisphere, taking geometry and materials into account in the process.
Info
It is essential to set the path depth to a 0-1 interval in the shading mask analysis when only direct radiation should be considered. This ensures that only irradiance directly from the sky is counted, excluding any bounces.
Warning
The hemisphere for the shading masks has to match the hemisphere for the sky.
Sky Instance#
The sky instance is used for point in time irradiance and represents localised sky conditions based on weather data at a specific point in time. The sky subdivision is defined using a hemisphere.
Sky Series#
The sky series is used to calculate cumulative radiation and represents localised sky conditions based on weather data over a time period. The time period and the frequency at which it is sampled is defined using a time pattern. The sky subdivision is defined using a hemisphere.
Point In Time Irradiance#
The point in time irradiance analysis measures the amount of irradiance that is received from the sky, at a position, at a specific point in time. It can be useful when evaluating irradiance levels using localised sky conditions to review risk of overheating.
To calculate the irradiance each shading mask is multiplied by the sky instance for the specific location and point in time. This produces an irradiance value in W/m2 for each position in the analysis.
Cumulative Radiation#
The cumulative radiation analysis measures the amount of radiation that is received from a sky series, at a position, over the time period specified in the sky series. It can be useful when evaluating total amount of received radiation or average received radiation using localised sky conditions to measure performance of solar panels or energy consumption needed to cool a building.
To calculate the radiation each shading mask is multiplied by the cumulative data in the sky series for the specific location and time period. This produces a radiation value in kWh/m2 for each position in the analysis.
