Environmental Conditions

Configure weather data, soiling, spectral adjustments, and horizon shading for your prediction

The Environmental Conditions Page allows you to configure the weather and environmental parameters that influence solar resource modeling in your prediction. This includes selecting weather data, defining soiling and spectral loss profiles, setting design temperatures, and importing horizon scene data.

Overview

The Environmental Conditions page is organized into four main sections:

1. Selected Weather File — Displays the currently selected weather file with key metadata (GHI, DHI, average temperature, P-Level) and allows you to change the selection.
2. Environmental Model Controls — Configure the algorithmic models used for air mass calculation, albedo sourcing, soiling losses, and spectral shift adjustments.
3. Monthly Parameters — Define month-by-month values for albedo, soiling loss, and spectral loss when using monthly override modes.
4. Plant Design Temperature & Horizon Scene — Set temperature design points for voltage calculations and import far-field horizon shading data.

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User Inputs

#	Input	Type	Units	Description	Related Documentation
1	Change Selection	Button	—	Opens the weather file selection dialog to choose a different weather file for the prediction. Weather files contain hourly or sub-hourly irradiance, temperature, wind speed, and other meteorological data.	Weather Library, Weather File
2	Air Mass	Dropdown	—	Selects the air mass calculation model. Options: Bird-Hulstrom or Kasten-Sandia. Air mass quantifies the optical path length through the atmosphere and affects transposition, decomposition, and spectral calculations.	Air Mass Model
3	Use Weather File Albedo	Toggle	—	When ON, albedo values are read from the weather file (if available). When OFF, user-defined monthly albedo values from the Monthly Parameters table are used.	Bifacial Irradiance
4	Soiling	Dropdown	—	Selects the soiling loss model. Options: None (no soiling), Monthly Override (user-defined monthly values), or Weather (time-series values from weather file).	Soiling
5	Spectral	Dropdown	—	Selects the spectral shift adjustment model. Options: None, Monthly Override, 1-Param Pwat or Sandia, 2-Param Pwat and AM (Spectral 2). Spectral adjustments account for module performance variations due to atmospheric conditions.	Spectral Shift Adjustment
6	Albedo	Table Column	—	Monthly ground reflectance values (0 to 1). Typical values: 0.2 for grass/soil, 0.6+ for snow. Used in bifacial rear-side irradiance calculations and ground-reflected irradiance.	Bifacial Irradiance
7	Soiling Loss (%)	Table Column	%	Monthly soiling loss percentages (0 to 100%). Represents irradiance reduction due to dust, dirt, and particulate accumulation on module surfaces. Only editable when Soiling model is set to Monthly Override.	Soiling
8	Annual Override	Button	—	Opens a dialog to set a single annual value that will be applied to all 12 months for albedo and/or soiling loss. Useful for simplified modeling scenarios.	—
9	Import NSRDB	Button	—	Imports albedo and/or other environmental data from the National Solar Radiation Database (NSRDB) based on the project location.	—
10	Show Soiling Import	Button	—	Opens the soiling import interface to load soiling loss data from external sources or soiling models.	Soiling
11	Override Recommendations	Button	—	Opens a dialog to manually override the ASHRAE-derived plant design temperatures. Design temperatures are used for module voltage calculations at temperature extremes.	—
12	Show Horizon Scene Import	Button	—	Opens the horizon scene import interface to define far-field obstructions (mountains, trees, buildings) that block direct beam irradiance at low sun angles.	Horizon Shading

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Saving Changes

Click Save + Close Section in the top-right corner to save your environmental conditions configuration and return to the prediction overview. Click Cancel to discard changes.