Area Solar Radiation (Spatial Analyst)

Summary

Derives incoming solar radiation from a raster surface.

Learn more about how solar radiation is calculated

Usage

Syntax

AreaSolarRadiation (in_surface_raster, {latitude}, {sky_size}, {time_configuration}, {day_interval}, {hour_interval}, {each_interval}, {z_factor}, {slope_aspect_input_type}, {calculation_directions}, {zenith_divisions}, {azimuth_divisions}, {diffuse_model_type}, {diffuse_proportion}, {transmittivity}, {out_direct_radiation_raster}, {out_diffuse_radiation_raster}, {out_direct_duration_raster})
ParameterExplanationData Type
in_surface_raster

Input elevation surface raster.

Raster Layer
latitude
(Optional)

The latitude for the site area. The units are decimal degrees, with positive values for the northern hemisphere and negative for the southern.

For input surface rasters containing a spatial reference, the mean latitude is automatically calculated; otherwise, latitude will default to 45 degrees.

Double
sky_size
(Optional)

The resolution or sky size for the viewshed, sky map, and sun map grids. The units are cells.

The default creates a raster of 200 x 200 cells.

Long
time_configuration
(Optional)

Specifies the time configuration (period) used for calculating solar radiation.

The Time class objects are used to specify the time configuration.

The different types of time configurations available are TimeWithinDay, TimeMultiDays, TimeSpecialDays, and TimeWholeYear.

The following are the forms:

  • TimeWithinDay({day},{start_time},{end_time})
  • TimeMultiDays({year},{start_day},{end_day})
  • TimeSpecialDays()
  • TimeWholeYear({year})

The default time_configuration is TimeMultiDays with the start_day of 5 and end_day of 160, for the current Julian year.

Time configuration
day_interval
(Optional)

The time interval through the year (units: days) used for calculation of sky sectors for the sun map.

The default value is 14 (biweekly).

Long
hour_interval
(Optional)

Time interval through the day (units: hours) used for calculation of sky sectors for sun maps.

The default value is 0.5.

Double
each_interval
(Optional)

Specifies whether to calculate a single total insolation value for all locations or multiple values for the specified hour and day interval.

  • NOINTERVALA single total radiation value will be calculated for the entire time configuration. This is default.
  • INTERVALMultiple radiation values will be calculated for each time interval over the entire time configuration. The number of outputs will depend on the hour or day interval. For example, for a whole year with monthly intervals, the result will contain 12 output radiation values for each location.
Boolean
z_factor
(Optional)

The number of ground x,y units in one surface z unit.

The z-factor adjusts the units of measure for the z units when they are different from the x,y units of the input surface. The z-values of the input surface are multiplied by the z-factor when calculating the final output surface.

If the x,y units and z units are in the same units of measure, the z-factor is 1. This is the default.

If the x,y units and z units are in different units of measure, the z-factor must be set to the appropriate factor, or the results will be incorrect.

For example, if your z units are feet and your x,y units are meters, you would use a z-factor of 0.3048 to convert your z units from feet to meters (1 foot = 0.3048 meter).

Double
slope_aspect_input_type
(Optional)

How slope and aspect information are derived for analysis.

  • FROM_DEM The slope and aspect grids are calculated from the input surface raster. This is the default.
  • FLAT_SURFACE Constant values of zero are used for slope and aspect.
String
calculation_directions
(Optional)

The number of azimuth directions used when calculating the viewshed.

Valid values must be multiples of 8 (8, 16, 24, 32, and so on). The default value is 32 directions, which is adequate for complex topography.

Long
zenith_divisions
(Optional)

The number of divisions used to create sky sectors in the sky map.

The default is eight divisions (relative to zenith). Values must be greater than zero and less than half the sky size value.

Long
azimuth_divisions
(Optional)

The number of divisions used to create sky sectors in the sky map.

The default is eight divisions (relative to north). Valid values must be multiples of 8. Values must be greater than zero and less than 160.

Long
diffuse_model_type
(Optional)

Type of diffuse radiation model.

  • UNIFORM_SKY Uniform diffuse model. The incoming diffuse radiation is the same from all sky directions. This is the default.
  • STANDARD_OVERCAST_SKY Standard overcast diffuse model. The incoming diffuse radiation flux varies with zenith angle.
String
diffuse_proportion
(Optional)

The proportion of global normal radiation flux that is diffuse. Values range from 0 to 1.

This value should be set according to atmospheric conditions. The default value is 0.3 for generally clear sky conditions.

Double
transmittivity
(Optional)

The fraction of radiation that passes through the atmosphere (averaged over all wavelengths). Values range from 0 (no transmission) to 1 (all transmission).

The default is 0.5 for a generally clear sky.

Double
out_direct_radiation_raster
(Optional)

The output raster representing the direct incoming solar radiation for each location.

The output has units of watt hours per square meter (WH/m2).

Raster Dataset
out_diffuse_radiation_raster
(Optional)

The output raster representing the diffuse incoming solar radiation for each location.

The output has units of watt hours per square meter (WH/m2).

Raster Dataset
out_direct_duration_raster
(Optional)

The output raster representing the duration of direct incoming solar radiation.

The output has units of hours.

Raster Dataset

Return Value

NameExplanationData Type
out_global_radiation_raster

The output raster representing the global radiation or total amount of incoming solar insolation (direct + diffuse) calculated for each location of the input surface.

The output has units of watt hours per square meter (WH/m2).

Raster

Code Sample

AreaSolarRadiation example 1 (Python window)

The following Python Window script demonstrates how to use the AreaSolarRadiation tool.

import arcpy
from arcpy.sa import *
from arcpy import env
env.workspace = "C:/sapyexamples/data"
outGlobalRadiation = AreaSolarRadiation("dem30", "", "400", TimeMultipleDays(2008,91,152))
outGlobalRadiation.save("C:/sapyexamples/output/glob_rad")
AreaSolarRadiation example 2 (stand-alone script)

Calculate the amount of incoming solar radiation over a geographic area.

# Name: AreaSolarRadiation_example02.py
# Description: Derives incoming solar radiation from a raster surface. 
#              Outputs a global radiation raster and optional direct, diffuse and direct duration rasters
#              for a specified time period. (April to July).
#              
# Requirements: Spatial Analyst Extension
# Author: ESRI

# Import system modules
import arcpy
from arcpy import env
from arcpy.sa import *

# Set environment settings
env.workspace = "C:/sapyexamples/output"

# Check out the ArcGIS Spatial Analyst extension license
arcpy.CheckOutExtension("Spatial")

# Set local variables
inRaster = "C:/sapyexamples/data/solar_dem"
latitude = 35.75
skySize = 400
timeConfig = TimeMultipleDays(2008, 91, 212)
dayInterval = 14
hourInterval = 0.5
zFactor = 0.3048
calcDirections = 32
zenithDivisions = 16
azimuthDivisions = 16
diffuseProp = 0.7
transmittivity = 0.4
outDirectRad = ""
outDiffuseRad = ""
outDirectDur = Raster("C:/sapyexamples/output/dir_dur")


# Execute AreaSolarRadiation
outGlobalRad = AreaSolarRadiation(inRaster, latitude, skySize, timeConfig,
   dayInterval, hourInterval, "NOINTERVAL", zFactor, "FLAT_SURFACE",
   calcDirections, zenithDivisions, azimuthDivisions, "UNIFORM_SKY",
   diffuseProp, transmittivity, outDirectRad, outDiffuseRad, outDirectDur)

# Save the output 
outGlobalRad.save("C:/sapyexamples/output/glob_rad")

Environments

Related Topics

Licensing Information

ArcView: Requires Spatial Analyst
ArcEditor: Requires Spatial Analyst
ArcInfo: Requires Spatial Analyst

6/29/2011