After modeling your site, it is helpful to leverage an irradiance map in order to determine the roof faces with the highest solar potential. Aurora's irradiance maps provide you with shade readings to identify shady roof areas that can negatively impact overall system performance.
Key Terms
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Irradiance: the power per unit area received from the sun in the form of electromagnetic radiation. Aurora measures this in kWh/m2/yr.
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Solar access: defined as the incident solar energy given shading, divided by the incident solar energy if there is no shading. In simpler terms, the solar access percentage refers to the percent of irradiance that is hitting the roof.
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Tilt and orientation factor (TOF): represented as a percentage and is calculated by dividing the solar insolation of the actual tilt and orientation by the solar insolation at the optimum tilt and orientation
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Total solar resource fraction (TSRF): the ratio of insolation available accounting for both shading and Tilt and Orientation Factor (TOF), compared to the total insolation available at a given location at the optimum tilt and orientation and with no shading.
Using irradiance
Once you have modeled your site, you can run an irradiance map:
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Click the irradiance button in the top toolbar (or press i). Aurora's servers will then simulate the sun's path for every daylight hour of the year and calculate the irradiance and solar access percentage across all roofs on your site.
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Once the map is generated, hovering over it provides insulation (in kWh) and shade readings (solar access, TOF, and TSRF in %) in the top, right corner of your screen. The color scale of the map indicates the locations with the highest solar potential, guiding your design. Yellow corresponds to higher solar potential while red corresponds to lower solar potential.
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For annual shade readings, move your mouse across the site. Expand the irradiance menu in the top, right corner to view monthly values.