Estimate solar power potential

Your nonprofit organization recently launched a pilot program to encourage the residents of the Glover Park neighborhood in Washington, D.C., to install solar panels on their roofs. The goal is for the solar panels to produce a large part of the electric power consumed by each household.

In this tutorial, you will use ArcGIS Pro to determine how much solar radiation each rooftop in the neighborhood receives throughout the year. Then you will estimate how much electric power each rooftop (and the neighborhood as a whole) could generate if every suitable building was equipped with solar panels.

This tutorial was last tested on November 16, 2023, using ArcGIS Pro 3.2. If you're using a different version of ArcGIS Pro, you may encounter different functionality and results.

Requirements

• User, Publisher, or Administrator role in an ArcGIS organization: ArcGIS Online (see options for software access) or ArcGIS Enterprise (learn more)
• ArcGIS Pro (see options for software access)
• ArcGIS Spatial Analyst extension

Explore the data

Before you begin your analysis of the solar power potential in Glover Park, you'll become familiar with the data and geography.

Open the project

First, you will download and open the default project data in ArcGIS Pro.

1. Download the Solar_in_Glover zip file.
2. Locate the downloaded file on your computer.

   Note:

   Depending on your web browser, you may have been prompted to choose the file's location before you began the download. Most browsers download to your computer's Downloads folder by default.

3. Right-click the file and extract it to a location you can easily find, such as your Documents folder.
4. Open the Solar_in_Glover folder.

   The folder contains several subfolders, an ArcGIS Pro project file (.aprx), an ArcGIS Toolbox (.tbx), and two ArcGIS Pro layer files (.lyrx).

5. If you have ArcGIS Pro installed on your machine, double-click the Solar_in_Glover project file. If prompted, sign in using your licensed ArcGIS account or ArcGIS Enterprise account.

   Note:

   If you don't have access to ArcGIS Pro or an ArcGIS organizational account, see options for software access.

   

   The project contains two layers. The DSM and the Building_Footprints layers. You'll first explore the DSM layer.

   The DSM layer, which is turned on by default, represents the neighborhood of Glover Park as a digital surface model (DSM). A DSM shows the elevation of the ground and the features on the ground, such as buildings and trees. This DSM is a raster layer, which depicts data in a grid where each cell contains a numeric value. It is symbolized so that darker gray cells have lower elevations and the lighter gray and white cells have higher elevations.

6. With the mouse wheel button, zoom in until you see the individual cells that compose the DSM raster.

   

   In this raster, each cell represents a surface of 0.5 by 0.5 meters (about 1.6 by 1.6 feet).

7. Click any cell.

   The cell's pop-up appears.

   

   A pop-up window appears. It contains a value that represents the elevation (in meters) of the selected raster cell. In the example, the highlighted cell has an elevation of about 89.9 meters (or 295 feet).

   By default, the DSM is symbolized so that darker cells have lower elevations and lighter cells have higher ones.

8. Close the pop-up. In the Contents pane, right-click DSM and choose Zoom To Layer.

   

   The map navigates back to the full extent of the Glover Park neighborhood.

Create a hillshade effect

Although patterns in the DSM suggest the locations of buildings and vegetation, you can better visualize the surface by creating a hillshade effect. A hillshade raster layer uses a realistic shading effect to depict elevation.

1. On the ribbon, click the Imagery tab. In the Analysis group, click the Raster Functions button.

   

   The Raster Functions pane appears.

   Note:

   Raster functions are tools that apply calculations directly to a raster's pixel values without requiring new data to be saved. As such, they are very efficient.

2. In the Raster Functions pane search box, type hillshade. In the list of results, under Surface, click Hillshade.

   

   The Hillshade tool opens.

3. For Raster, choose DSM. Accept all the other default values and click Create new layer.

   

   A new layer, named Hillshade_DSM, is added to the map. For optimum visual effect, you'll combine hillshade and DSM layer symbolization.

4. In the Contents pane, drag the DSM layer above the Hillshade_DSM layer.

   

   The DSM layer is set to 40 percent layer transparency. When it is drawn above the hillshade, both layers are visible.

   

5. Zoom in with the mouse wheel button until you can see the details of the landscape.

   

   The hillshade layer's realistic shading added a 3D effect. Buildings, trees, and other surface features are more distinguishable. You can also distinguish whether buildings have flat or gabled (sloped) roofs, which is important for rooftop solar panels.

   Note:

   While you can symbolize the DSM layer with a more colorful color ramp, you'll keep the gray tones. Subdued tones form a good background that will let the other layers you'll produce in this tutorial be the center of attention.

6. In the Contents pane, right-click DSM and choose Zoom to Layer.

   Note:

   The hillshade layer that you created with a raster function is computed dynamically and not written on disk. So, if you remove it from the Contents pane, it will completely disappear, and you'll have to recreate it.

Explore building footprints

The project contains a layer called Building_Footprints that is turned off by default. Next, you will explore this layer.

1. In the Contents pane, check the Building_Footprints layer check box to turn it on.

   

   The layer contains outlines of every building in the Glover Park neighborhood. Unlike the DSM and hillshade layers, which are rasters, this is a vector layer, which displays spatial information in the form of polygons.

2. Zoom and pan throughout the map to explore the neighborhood.

   You can see that the neighborhood contains many types of buildings, from small single-family units to large commercial structures, as well as medium-sized multifamily units. Many areas also present a significant level of tree coverage, which can have an impact on solar power production.

3. Return to the full extent of the neighborhood.
4. On the Quick Access Toolbar, click the Save button to save the project.

   Note:

   A message may appear warning you that saving this project file with the current ArcGIS Pro version will prevent you from opening it again in an earlier version. If you see this message, click Yes to proceed.

   

In this module, you downloaded, opened, and explored the initial data for the project, which includes elevation data and building footprints. You also created a hillshade layer to better visualize the neighborhood's surfaces.

Map solar energy

Next, you'll create a raster layer that maps how much solar energy reaches rooftop surfaces in Glover Park over the course of a typical year. The more solar energy a roof surface receives, the more electric power could be generated if it were equipped with solar panels.

Create a solar radiation layer

To create the solar radiation layer, you'll use the Area Solar Radiation tool. This tool is part of the ArcGIS Spatial Analyst extension and takes a DSM as input. It calculates radiation based on a sophisticated model that takes into account the position of the sun throughout the year and at different times of day, obstacles that may block sunlight such as nearby trees or buildings, and the slope and orientation of the surface. You can read more about modeling solar radiation in the Modeling solar radiation help documentation.

The DSM provides the necessary information on obstacles, orientation, and slope. The output will be a raster layer where each cell value is the amount of solar radiation in watt-hours per square meter (Wh/m²) at that location.

Note:

The Area Solar Radiation tool is computationally intense and can take between 20 and 90 minutes to run. For the purposes of this exercise, you will have the option of running the tool yourself or using a solar radiation raster layer that has already been created and was provided with the project data. Regardless of your choice, you'll first learn how to select the right parameter values for the tool.

1. On the ribbon, on the Analysis tab, in the Geoprocessing group, click Tools.

   

   The Geoprocessing pane appears.

2. Search for and open the Area Solar Radiation tool.

   

3. In the Area Solar Radiation tool, for Input raster, choose DSM. For Output global radiation raster, change the output name to Solar_Rad_Whm2_my_own.

   Note:

   The name Solar_Rad_Whm2_my_own is to differentiate it from the ready-made layer Solar_Rad_Whm2 that you downloaded, and to make sure you don’t overwrite it.

   When the input raster is chosen, the Latitude parameter is automatically populated with the latitude of the DSM. This parameter helps determine the sun's position.

   

   By default, the tool runs using an interval of several days. You'll change the time interval to compute the solar radiation over the course of an entire year.

4. For Time configuration, choose Whole year. If necessary, for Year, type 2021 or the current year.

   By default, the tool computes the amount of solar radiation once every half hour for each day sampled. You will change the Hour interval to once every hour to reduce calculation time.

5. For Hour interval, type 1.

   

   By default, the tool checks 32 directions around each cell to find light-blocking obstacles. To reduce calculation time, you will change this value to 16.

6. Expand Topographic parameters. For Calculation directions, type 16.

   

   You'll also change the tool environments, setting the Building_Footprints layer as a mask, so that only areas within the building footprints will be processed, saving calculation time.

7. Click the Environments tab.

   

8. Under Raster Analysis, for Mask, choose Building_Footprints.

   

   As mentioned, the Area Solar Radiation tool is computationally intense. If you want to run the tool (it may take 20 to 90 minutes to run), click Run.

9. If instead, you prefer to use the raster layer that was already created, on the ribbon, on the View tab, in the Windows group, click Catalog Pane. In the Catalog pane, expand Databases and Solar_in_Glover.gdb. Right-click Solar_Rad_Whm2 and choose Add To Current Map.

   

   Note:

   Depending on whether you create the layer yourself or add the existing layer to the map, the layer symbology may differ. Later in the tutorial, you will change the layer's symbology, so its current variation does not matter.

   

10. Save the project.

Convert the units of measurement

The solar radiation raster uses watt-hours per square meter as its unit of measurement. According to the legend in the Contents pane, some cells have values of over 1 million (expressed with the notation e+06). To reduce the size of these values and make them easier to read, you'll convert the raster layer to kilowatt-hours per square meter (kWh/m²).

You won't need the Building_Footprints layer for the next steps, so you'll turn it off.

1. In the Contents pane, uncheck Building_Footprints to turn it off.

   

2. In the Geoprocessing pane, click the Back button to go back to the search functionality (you may need to click it twice).

   

3. Search for and open Raster Calculator (Spatial Analysis Tool).

   There are 1,000 watts in a kilowatt, so to convert the units of measurement, you need to create an expression that divides existing cell values by 1,000.

4. In the Raster Calculator tool, for Map Algebra expression, type (or build) the following expression:

   "Solar_Rad_Whm2" / 1000

   Note:

   If you created your own solar radiation raster layer, the name of the layer in the expression will be Solar_Rad_Whm2_my_own instead of Solar_Rad_Whm2.

   

5. For Output raster, change the output name to Solar_Rad.
6. Click Run.

   The new raster layer is created and added to the map. It is similar to the original solar radiation layer, but the values are 1,000 times smaller.

   You no longer need the original solar radiation layer, so you will remove it.

7. In the Contents pane, right-click Solar_Rad_Whm2 (or Solar_Rad_Whm2_my_own) and choose Remove.

   

Symbolize the solar radiation layer

Next, you will symbolize the Solar_Rad layer. For your analysis, you'll use uniform symbology for all solar radiation raster layers to ensure that they can be compared visually. You will apply a layer file with predefined symbology to the layer. This layer file was included with the project data you downloaded.

1. In the Contents pane, click the Solar_Rad color ramp.

   

   The Symbology pane appears.

2. In the Symbology pane, click the options button and choose Import from layer file.

   

3. In the Import Symbology window, expand Folders and Solar_in_Glover. Double-click Solar_Rad.lyrx.

   The layer file is applied to the layer. The new symbology appears on the map.

   

4. Close the Symbology pane.
5. Zoom in to better see the rooftop surfaces.

   

   Red and orange colors indicate higher amounts of solar radiation, while yellow and blue tones indicate lower amounts. (The cells that are outside the Building_Footprints polygons have not been computed. They have a value of NoData and are not displayed.)

   North-facing roof slopes have blue and yellow tones, as they tend to receive less solar energy than south-facing ones. Additionally, roofs blocked by trees or other buildings sometimes receive very little solar energy.

6. Zoom out to return to the full extent of the neighborhood. Save the project.

In this module, you mapped the annual solar energy received on Glover Park rooftops. First, you created a solar radiation raster layer. Then, you converted the units of measurement and symbolized the layer for visualization purposes. Next, you'll identify rooftops suitable for solar panels.

Identify suitable rooftops

To identify suitable rooftops for solar panels, you will consider three criteria:

• Suitable rooftops should have a slope of 45 degrees or less, as steep slopes tend to receive less sunlight. To determine rooftop slope, you must create a slope raster layer.
• Suitable rooftops should receive at least 800 kWh/m² of solar radiation. You can assess this criterion using your solar radiation raster layer.
• Suitable rooftops should not face north, as north-facing rooftops in the northern hemisphere receive less sunlight. To determine rooftop orientation, you must create an aspect raster layer.

Create a slope layer

First, you will use the Surface Parameters tool to create a slope raster layer based on your DSM.

1. If necessary, open the Geoprocessing pane. If the Geoprocessing pane is already open, click the Back button.
2. In the Geoprocessing pane, search for and open the Surface Parameters (Spatial Analyst Tools) tool, and enter the following parameters:
   • For Input surface raster, choose DSM.
   • For Output raster, type Slope_DSM.
   • For Input analysis mask, keep DSM.
   • Confirm that Parameter type is set to Slope.

   The other parameters, which determine how a slope is measured and calculated, do not need to be changed.

   

3. Click Run.

   The tool runs and the new raster layer is added to the map.

   

   Each cell in this layer contains a slope value ranging from 0 to 90 degrees. The lighter colors represent steeper slopes while darker colors represent milder slopes.

Create an aspect layer

To determine the rooftop orientation, you will create an aspect raster layer using the Surface Parameters tool.

1. In the Surface Parameters tool pane, enter the following parameters:
   • For Input surface raster, keep DSM.
   • For Output raster, type Aspect_DSM.
   • For Input analysis mask, keep DSM.
   • For Parameter type, choose Aspect.

   You do not need to change the method by which the tool will calculate aspect.

   

2. Click Run.

   The tool runs and the new raster is added to the map.

   

   Each cell contains a value expressing orientation in degrees, with 0 representing absolute north and 180 representing absolute south.

Remove areas with high slopes

Next, you will use your raster layers to find areas that meet the criteria for solar panels. First, you'll remove areas from your solar radiation raster layer that have a slope steeper than 45 degrees.

All of your raster layers use the same cell grid. Because of this, you can compare the values in the solar radiation and slope layers. You will create an expression in the Con tool that checks whether each slope value is less than or equal to 45.

If a cell's slope is steeper than 45 degrees, its value will be changed to NoData in the output layer. Otherwise, the cell will be given its corresponding solar radiation value. The result will be a solar radiation raster layer that does not include slopes steeper than 45 degrees.

1. In the Geoprocessing pane, click the Back button. Search for Con and open Con (Spatial Analyst Tools).
2. In the Con tool pane, for Input conditional raster, choose Slope_DSM.
3. Under Expression, build the expression Where VALUE is less than or equal to 45.

   

   This expression will be applied to every cell in the slope raster. If a cell has a value less than or equal to 45, that cell is considered true. If not, the cell is considered false.

   Next, you will choose the raster layer that will provide the output cell values for cells found to be true. Ultimately, you want to compute the solar radiation potential of the rooftops, so you'll have the output layer use solar radiation cell values.

4. For Input true raster or constant value, choose Solar_Rad.

   For the cell values found to be false, you have the option to choose a raster layer or set a constant value. However, you'll leave this parameter empty so that false cells are given the NoData value.

5. For Output raster, change the output name to Solar_Rad_S (S stands for Slope).

   

6. Click Run.

   The tool runs and the new raster is added to the map. Before you explore the new layer, you'll change its symbology to match your Solar_Rad raster layer.

7. In the Contents pane, click the Solar_Rad_S color ramp.

   The Symbology pane appears.

8. In the Symbology pane, click the options button and choose Import from layer file.
9. In the Import symbology window, open the Folders and Solar_in_Glover folders. Double-click Solar_Rad.lyrx.

   The new symbology is added to the layer. You'll now use the Swipe tool to compare how Solar_Rad_S and Solar_Rad differ.

10. Close the Symbology pane.
11. In the Contents pane, uncheck the Aspect_DSM and Slope_DSM layers to turn them off.
12. Ensure that the Solar_Rad and Solar_Rad_S layers are turned on. Click Solar_Rad to select it.
13. On the ribbon, on the Raster Layer tab, in the Compare group, click Swipe.

    

14. Zoom in to view buildings in more detail. Drag the Swipe pointer from top to bottom to peel off the Solar_Rad layer and see what areas have been removed in the Solar_Rad_S layer.

    

    The removed rooftops areas are those that had slopes above 45 degrees.

    Note:

    While swiping, to explore more areas, you can zoom out and zoom back in with the mouse wheel button. To pan, you can press the C key while dragging.

15. Return to the full extent of the neighborhood.
16. Save the project.

Remove areas with low solar radiation

Next, you will consider the second criterion for suitable rooftops. Rooftop surfaces should receive at least 800 kWh/m² in solar radiation, if solar panels are to be installed. You will use the Con tool on the Solar_Rad_S layer to remove any remaining areas with low solar radiation.

The Geoprocessing pane is already open to the Con tool.

1. In the Con tool pane, for Input conditional raster, choose Solar_Rad_S.
2. Under Expression, click Remove Clause to remove the previous expression.

   

3. Click Add Clause and form a new expression that reads Where VALUE is greater than or equal to 800.
4. For Input true raster or constant value, choose Solar_Rad_S. For Output raster, change the output name to Solar_Rad_S_HS (HS stands for High Solar).

   

5. Click Run.

   The new raster layer is added to the map. You'll symbolize it the same way you symbolized the other solar radiation layers.

6. In the Contents pane, click the Solar_Rad_S_HS color ramp.
7. In the Symbology pane, click the options button and choose Import from layer file. In the Import Symbology window, browse to Solar_in_Glover and double-click Solar_Rad.lyrx.

   The symbology is applied to the layer.

8. Close the Symbology pane.
9. In the Contents pane, turn off the Solar_Rad layer.
10. Click the Solar_Rad_S layer to select it.
11. With the Swipe tool, inspect how the Solar_Rad_S and Solar_Rad_S_HS differ.

    

    More unsuitable areas have been removed. These areas received low solar radiation, making them undesirable for solar panels.

12. Return to the full extent of the neighborhood. Save the project.

Remove areas that face north

The third criterion for suitable rooftops is that roof surfaces should not face north. In the northern hemisphere, surfaces facing north are likely to receive less solar radiation than surfaces facing other directions. (In the southern hemisphere, south-facing surfaces receive the least solar radiation.)

Many north-facing roof surfaces were already removed when you removed areas with low solar radiation, but some remain. Based on the Aspect_DSM legend, slopes that face north have a value less than 22.5 degrees or more than 337.5 degrees. Additionally, you want to keep slopes that are almost flat, regardless of their aspect. If a roof is flat, its aspect does not matter for solar panels. You will consider that slopes of 10 degrees or less are flat or almost flat.

To fulfill both conditions, you'll use both Aspect_DSM and Slope_DSM. You'll run the Con tool twice, first to determine areas with low slopes and then to determine areas that face north.

1. Confirm that the Geoprocessing pane is still open to the Con tool. For Input conditional raster, choose Slope_DSM.
2. Remove the expression and add the new expression Where VALUE is less than or equal to 10.
3. For Input true raster or constant value, choose Solar_Rad_S_HS. For Output raster, change the output name to Solar_Rad_Low_Slope.

   

4. Click Run.

   The new raster layer is added to the map. You will run the Con tool a second time to determine north-facing surfaces.

5. In the Con tool pane, for Input condition raster, choose Aspect_DSM.

   North-facing slopes are slopes that have a value less than 22.5 or more than 337.5. Your expression will require two clauses to fulfill both of these conditions.

6. Remove the expression and add the new expression Where VALUE is greater than 22.5.
7. Click Add Clause. Create the expression And VALUE is less than 337.5.

   Together, these clauses cover all surfaces that do not face north.

   You will continue to use Solar_Rad_S_HS as the true raster, but you'll add the Solar_Rad_Low_Slope layer as the false raster. That way, false cells (those that face north) will be replaced by values from the low slope layer. The output layer will contain both areas that do not face north and areas with a low slope.

8. Continue entering the following in the Con tool pane:
   • For Input true raster or constant value, confirm that Solar_Rad_S_HS is selected.
   • For Input false raster or constant value, choose Solar_Rad_Low_Slope.
   • For Output raster, type Solar_Rad_S_HS_NN (NN stands for No North).

   

9. Click Run.

   The new raster layer is added to the map. You will symbolize it the same way you have symbolized the other solar radiation layers.

10. In the Contents pane, click the Solar_Rad_S_HS_NN color ramp. In the Symbology pane, click the options button and choose Import from layer file.
11. Browse to the Solar_in_Glover folder and double-click Solar_Rad.lyrx.

    The symbology is added to the raster layer.

12. Close the Symbology pane.
13. In the Contents pane, turn off the Solar_Rad_Low_Slope and Solar_Rad_S layers. Select the Solar_Rad_S_HS layer.

    

14. With the Swipe tool, inspect how the Solar_Rad_S_HS and Solar_Rad_S_HS_NN differ.

    

    Because many north-facing surfaces were removed previously when you removed areas with low solar radiation, the change between these layers is not so dramatic. However, some areas did get removed, and the Solar_Rad_S_HS_NN layer contains only roof surfaces suitable for solar panels.

    Note:

    For actual solar panel installation, it would be necessary to look at each rooftop in more detail, but for the purpose of your analysis, this approximation is sufficient.

15. When you are done exploring, on the ribbon, on the Map tab, in the Navigate group, click Explore deactivate the Swipe tool.

    

16. In the Contents pane, turn off Solar_Rad_S_HS.

    For clarity, you'll rename the Solar_Rad_S_HS_NN layer.

17. In the Contents pane, click Solar_Rad_S_HS_NN twice to edit it, type Suitable_Cells, and press Enter.

    

18. Return to the full extent of the neighborhood. Save the project.

In this module, you started from the initial solar radiation raster and removed all areas that are unsuitable for solar panels. You now have a suitable surface raster that you'll use to continue your analysis.

Calculate power per building

Your map shows how much solar radiation each suitable raster cell receives. In this module, you'll aggregate that data to determine how much solar radiation each building receives in a typical year. Then, you'll convert the solar radiation to electric power production potential and examine the results.

Aggregate cells by building

First, for every building, you'll calculate the area covered by its suitable cells (in m²) and their average solar radiation (in kWh/m²). You'll do that using the Zonal Statistics as Table tool.

1. In the Contents pane, turn off the DSM and Hillshade_DSM layers. Turn on the Building_Footprints layer.

   

   The Zonal Statistics as Table tool will look within each building footprint polygon and aggregate the suitable cells it contains.

2. If necessary, on the ribbon, on the Analysis tab, click Tools to open the Geoprocessing pane. If necessary, in the Geoprocessing pane, click the Back button.
3. Search for and open the Zonal Statistics as Table (Spatial Analyst Tools) tool.
4. In the Zonal Statistics as Table tool pane, choose the following parameter values:
   • For Input raster or feature zone data, choose Building_Footprints
   • For Zone field, confirm that Building_ID is chosen.
   • For Input value raster, choose Suitable_Cells.
   • For Output table, type Solar_Rad_Table.
   • For Statistics type, choose Mean.

   The Building_ID field is a unique identifier for each building footprint. Using this field as the zone field will ensure that each building footprint is clearly identified.

   You can choose to calculate several types of statistics. You'll calculate the Mean to determine the average solar radiation per square meter for each building.

   

5. Click Run.

   The tool runs and the new table is added to the bottom of the Contents pane, under Standalone Tables.

   Tip:

   Your Contents pane contains many layers, so you may need to scroll down to see the table.

6. In the Contents pane, right-click Solar_Rad_Table and choose Open.

   

   The table opens.

7. Review the content of the table.

   

   • Each row represents a building, uniquely identified by its Building_ID.
   • COUNT gives the number of suitable cells for that building.
   • AREA gives the area covered by suitable cells (in m²).
   • MEAN gives the average solar radiation (in kWh/m²) that these cells receive.

   Because this table is stand-alone, it is not connected to the spatial data on your map. You'll join the fields of interest, AREA and MEAN, to the Building_Footprints layer using the Join Field tool. The matching field for this join will be Building_ID.

8. Close the table.
9. In the Geoprocessing pane, click the Back button. Search for and open Join Field.
10. In the Join Field tool pane, choose the following values:
    • For Input Table, choose Building_Footprints.
    • For Input Field, choose Building_ID.
    • For Join Table, choose Solar_Rad_Table.
    • For Join Field, choose Building_ID.
    • For Transfer Fields, choose AREA.
    • For the second Transfer Fields drop-down list that appears, choose MEAN.

    

11. Click Run.

    After a few moments, the process is completed.

12. In the Contents pane, right-click Building_Footprints and choose Attribute Table.

    The AREA and MEAN fields have been added to the end of the table.

13. Close the table.

Find suitable buildings

Now that you know the size of the suitable area on each building rooftop, you will apply one last criterion to determine solar panel suitability. You will consider that if a building has less than 30 square meters of suitable roof surface, it is generally not suitable for solar panel installation, as it is not worth the installation investment. You'll select buildings that have enough suitable roof surface using the Select Layer By Attributes tool.

1. On the ribbon, on the Map tab, in the Selection group, click Select By Attributes.

   

2. In the Select By Attributes window, for Input Rows, confirm that Building_Footprints is chosen. For Selection type, confirm that New selection is chosen.
3. For Expression, create the expression Where AREA is greater than or equal to 30.

   

4. Click OK.

   The selection is applied. Many buildings are selected but some are not.

5. At the bottom of the map, view the exact Selected Features number.

   

   Note:

   Your number of buildings selected may be slightly different than on the example image.

6. Zoom in to view buildings in more detail.

   

   Many buildings that were not selected are particularly small (such as garden sheds). Others are larger but lack suitable surfaces for solar panels, possibly due to shade produced by nearby trees or other buildings.

7. Zoom out to return to the full extent of the neighborhood.

   You'll export the selected buildings into a new feature class.

8. In the Contents pane, right-click Building_Footprints, point to Data, and choose Export Features.
9. In the Export Features window, for Input Features, confirm that Building_Footprints is selected. For Output Feature Class, type Suitable_Buildings.

   

10. Click OK.

    The feature class is created and added to the map. You no longer need the original building footprints layer or the solar radiation stand-alone table, so you'll remove them.

11. In the Contents pane, right-click Building_Footprints and choose Remove. Similarly, remove Solar_Rad_Table.
12. Save the project.

You now have a map of all the suitable buildings, and for each building, the suitable area they contain and their mean solar radiation per square meter.

Create a field for solar radiation

Next, you'll create a field in the Suitable_Buildings attribute table. This field will contain the total amount of solar radiation received per year by each building's usable area. You'll calculate this field by multiplying each building's suitable area by its average solar radiation per square meter. To avoid the numbers becoming too large, you'll also convert the solar radiation from kilowatt-hours to megawatt-hours by dividing by 1,000. The corresponding formula will be: (Area * Mean) / 1000.

1. In the Contents pane, right-click Suitable_Buildings and choose Attribute Table.
2. On the ribbon of the attribute table, click the Add Field button.

   

   The Fields view appears. In this view, you can edit existing fields or add new ones.

3. On the bottom row of the Fields view, for Field Name, type Usable_SR_MWh. For Data Type, choose Double.

   

   Note:

   The Double data type is meant to store decimal numbers.

   You'll have the field round all values to 2 decimal places.

4. For Number Format, double-click the empty cell and click the Determine display formatting for numeric and data field types button.

   

   The Number Format window appears.

5. In the Number Format window, for Category, choose Numeric. Under Rounding, for Decimal places, type 2.

   

6. Click OK.
7. On the ribbon, on the Fields tab, in the Manage Edits group, click Save.

   

   The field is saved and added to the attribute table.

8. Click the Suitable_Buildings tab to go back to the attribute table.

   

   Currently, the values of the new field, Usable_SR_MWh, are all null.

   

   You'll calculate values for the field based on the values in the AREA and MEAN fields.

9. In the attribute table, right-click the Usable_SR_MWh column name and choose Calculate Field.

   

   In the Calculate Field tool, you'll create an expression with the formula delineated above.

10. In the Calculate Field window, for Usable_SR_MWh =, create or copy and paste the following expression:

    (!AREA! * !MEAN!) / 1000

    

11. Click OK.

    The tool runs and the field is calculated.

    

    The results are expressed in megawatt-hours.

12. Close the Fields view. Save the project.

    You now have an estimate of how much solar radiation every building receives each year on surfaces suitable for solar panels.

Convert solar radiation to power

Next, you will convert the usable solar radiation values to electric power production potential. The amount of power that solar panels can produce depends not only on solar radiation, but also the solar panels' efficiency and the installation's performance ratio.

The United States Environmental Protection Agency (EPA) provides a conservative best estimate of 16 percent efficiency and 86 percent performance ratio. These values mean that the solar panels are capable of converting 16 percent of incoming solar energy into electricity, and then 86 percent of that electricity is preserved as it goes through the installation.

To determine electric power production potential, you'll create a field and calculate it by multiplying your usable solar radiation values by the efficiency and performance ratio values. The corresponding formula will be: Usable_SR_MWh * 0.16 * 0.86.

1. In the attribute table, click the Add Field button.
2. In the Fields view, for the new field's Field Name text box, type Elec_Prod_MWh. For Data Type, choose Double.
3. For Number Format, double-click the empty cell and click the Determine display formatting for numeric and data field types button.
4. In the Number Format window, for Category, choose Numeric. Under Rounding, for Decimal places, type 2.
5. Click OK.
6. On the ribbon, on the Fields tab, in the Manage Edits group, click Save.
7. Click the Suitable_Buildings tab to go back to the attribute table.

   The new field is added to the attribute table. Its values are null. Next, you'll calculate the field values.

8. In the attribute table, right-click the Elec_Prod_MWh column name and choose Calculate Field.
9. In the Calculate Field window, for Elec_Prod_MWh =, create or copy and paste the following expression:

   !Usable_SR_MWh! * 0.16 * 0.86

   

10. Click OK.

    The tool runs and the field is calculated.

    

11. Close the attribute table and the Fields view.
12. Save the project.

Symbolize the data

Your analysis is complete. Before you explore the results, you'll symbolize the layer based on the field you created. You will also add a basemap for context.

1. In the Contents pane, click the symbol for the Suitable_Buildings layer.

   The Symbology pane appears.

2. If necessary, on the Symbology pane, click the Back button to go to the Primary symbology tab.
3. In the Primary symbology tab, click the options button and choose Import symbology.

   

   The Geoprocessing pane appears, displaying the Apply Symbology From Layer tool.

4. In the Apply Symbology From Layer tool, for Symbology Layer, click the Browse button.

   

5. In the Symbology Layer window, browse to the Solar_in_Glover folder and double-click Suitable_Buildings.lyrx.
6. Leave the other parameters unchanged and click Run.

   The layer symbology is updated.

7. In the Contents pane, turn off all the layers except Suitable_Buildings.

   Tip:

   To turn off all layers, hold Ctrl and click one of the layer boxes.

8. On the ribbon, on the Map tab, in the Layer group, click Basemap. Choose Dark Gray Canvas.

   

   The basemap is added to the map.

   

9. Explore the final map.

   Larger buildings tend to have higher electric power production potential than single-unit dwellings. This pattern makes sense because larger buildings have larger roof surfaces. However, larger buildings also have higher electric power needs.

   In 2021, the average household in the United States consumes 12.154 MWh per year. Could many households in the Glover Park neighborhood cover most or all their electric power needs with solar panels?

   You can also check the total amount of power that could be produced by the neighborhood.

10. In the Contents pane, right-click Suitable_Buildings and choose Attribute Table.
11. In the attribute table, right-click the Elec_Prod_MWh column name and choose Visualize Statistics.

    

    A chart opens, showing the distribution of the field values as a bar chart, as well as a Chart Properties pane. The pane contains statistics, including the sum of electric power production potential for all buildings.

12. In the Chart Properties pane, under Statistics, identify the Sum row.

    

    Note:

    Your statistics may differ slightly from the example image.

    The entire neighborhood has the potential to produce over 20,000 MWh.

13. Close the Chart Properties pane, the chart, and the attribute table. Save the project.

In this tutorial, you accomplished your goal and determined the solar power potential of the Glover Park neighborhood in Washington, D.C. To do so, you used a DSM to create a solar radiation raster layer, as well as slope and aspect raster layers. Then, you identified suitable rooftops for solar panels and calculated how much power these rooftops could generate.

Your results represent a yearly average estimate. However, solar-based electric power production varies according to the season, as day length and hours of sunlight change. You could also perform this tutorial's workflow for specific days of the year, such as the winter and summer solstices and the fall and spring equinoxes, to determine the highest, lowest, and medium solar power production values.

You can replicate this workflow for any community, as long as you have building footprints and a DSM. Many communities provide open GIS data. The data for this tutorial was acquired from the Open Data DC website.

You can find more tutorials such as this on the Introduction to Imagery & Remote Sensing page.

Acknowledgements

• The Building_Footprints dataset was derived from the Building Footprints dataset on Open Data DC. The data is owned by the City of Washington, DC, and is shared under a CC BY 4.0 license. The original dataset has been reduced to a subset.
• The DSM dataset was derived from the District of Columbia - Classified Point Cloud LiDAR dataset. The data is owned by the City of Washington, DC, and is in the public domain. See the Washington, DC terms of use.
• The Solar_Rad_Whm2, Solar_Rad.lyrx, and Suitable_Buildings.lryx datasets were created by the author, Delphine Khanna.
• Gallery image by Pujanak on Wikimedia Commons.