With summer just around the corner, Vivian gets us using the Area Solar Radiation tool.

Solar radiation, also known as the solar resource or sunlight (New Zealand singer Lorde might call it solar power), is a general term for the electromagnetic radiation emitted by the sun.

Solar radiation is crucial for our survival as it provides heat, light, and energy necessary for all living organisms. Without solar radiation, Earth’s surface would be approximately 32°C colder. However, too much solar radiation could also be dangerous for us as it is associated with increased risks of various diseases.

Solar radiation can be captured and turned into useful forms of energy, such as electricity and heat, with the help of a variety of technologies.

Therefore, calculating an area’s available solar resource would be useful in many ways.

Area solar radiation tool:

Area solar radiation tool is a spatial analysis tool that derives incoming solar radiation from a raster surface.

This is what Area solar radiation tool looks like in ArcGIS Pro.

The input raster refers to an Input elevation surface raster, a DEM layer.

The rest of the inputs are optional and can be altered as required.

For example:

the “Latitude” is the latitude for the site area. If not altered manually, the mean latitude is automatically calculated if the input raster contains a spatial reference, otherwise, latitude will default to 45 degrees.

The sky size is the resolution or sky size for the viewshed, sky map, and sun map raster. The units are cells. The default creates a raster of 200 by 200 cells.

Time configuration Specifies the time period to use for the calculations.

z-factor is used to convert z units to x,y units, to correct calculations. It needs to be specified if data is not in a projected coordinate system with units of meters ( or other units used for x,y) as Z-units should be the same units as the x,y ground units for accurate results

By ticking the “Create outputs for each interval”, you are choosing to have a “breakdown” over the period. The output would contain multiple bands for each time interval during the duration of specified time (unlike the demonstration below with one raster output). For a Analysis with multiple days, the “breakdown” would use day interval, if the analysis is within a day, then hour interval.

below snip shows the output raster contains a band for each interval when “Create outputs for each interval” is ticked.

You can choose to view each of these bands on the map by selecting them on symbology of the layer.

when “Create outputs for each interval” is not ticked, the output raster only contains one band with insolation integrated for the entire duration of time.

The return value is the output global radiation raster that represents the global radiation calculated for each location of the input surface.

Demonstration: 

I have run the area solar radiation tool on a DEM layer on a small area in wellington. The process and result are as below.

This is the DEM layer on a small area in wellington, downloaded from koordinates.com.

For the analysis, the latitude is automatically calculated, the resolution is default. The start day of the analysis is the 5th day of 2021 which is 5/1/2021 and the end day is the 160th day of the year which is 9/6/2021. The time interval through the year used for calculation of sky sectors for the sun map is 14 days (biweekly, if “Create outputs for each interval” is ticked, it will contain multiple bands with biweekly “breakdown”) and Time interval through the day is 0.5 hours (default, will not be used as the analysis is long than 24 hours). However, The “Create outputs for each interval” is not ticked as we are not looking to calculate insolation integrated over the specified time period this time.

Please refer to the geoprocessing part from the snip to see my input of above information.

 

The output raster “AreaSol_DEM_1” has units of watt hours per square meter and represents the global radiation (total amount of incoming solar insolation, direct + diffuse) calculated for each surface.

The analysis shows that from 5/1/2021 to 9/6/2021, this small area in wellington has a total amount of approximately  from 144381- 559270 WH/m2  of incoming solar insolation across its surface.

Useful links 

Area solar radiation (spatial analyst). Area Solar Radiation (Spatial Analyst)-ArcGIS Pro. Retrieved from https://pro.arcgis.com/en/pro-app/latest/tool-reference/spatial-analyst/area-solar-radiation.htm.

Solar radiation basics. Retrieved from https://www.energy.gov/eere/solar/solar-radiation-basics.

Solar radiation & photosynthetically active radiation. Environmental Measurement Systems. (2021, January 22). Retrieved from https://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/

Linz Data Service. LINZ Data Service. (n.d.). Retrieved September 27, 2021, from https://data.linz.govt.nz/    (a good place to get your data for analysis)