GIS Constraint Guide for Renewable Energy
Updated: Oct 2, 2021
Mapping available land for energy development is critical for land use planning efforts. An expanding urban sprawl and predicting future development is essential to promote sustainability. Utilizing ESRI ArcGIS, we can accurately access constraints such as topography, floodplains, tree cover and distance to power. An accurate GIS system also allows for updated imagery and countywide parcel data. This article will talk about acquiring constraint data for solar development and accurately assessing the impact of the data.
As you would expect, ideal topography for solar development is flat land. Obviously, that is not possible 100% of the time. According to Solar Power World, “Solar sites in the Northeast, mountain states or hilly regions can undergo civil engineering to make level ground for mounting. Yet, grading land can alter rain runoff patterns on the site, possibly displacing native species and raising project costs.” (Article Link)
Later in the article, it is stated that less than 20% grade is ideal for solar development. States such as Florida and Georgia have ideal topography for solar development. However, the same development can be immensely more difficult in eastern states like North Carolina, Maryland, Virginia, and Kentucky.
The industry standard for accessing topographic maps and data is the USGS (usgs.gov). Elevation data is produced and distributed by a program called “3D Elevation Program” (3DEP). Most of the current topo data is derived from lidar point clouds and meets accuracy and spacing specifications. 1-meter DEM’s are available for a majority of the United States and will be expanding through 3DEP.
Below is a developmental area outside Charleston, West Virginia. By utilizing the USGS Topo Map Service in ArcGIS Online, we can get a pretty good picture of the topography layout in this area. The first step in our solar development process is to access a site with less than 20% gradient. The data from USGS will help us immensely in this process.
The next piece of constraint data is hydrography data. Similar to the topography data, hydrography and watershed boundaries are a natural constraint that must be monitored before development. Once again, the USGS is a valuable source for this data. According to their website, “The USGS National Geospatial Program manages the National Hydrography Dataset (NHD), Watershed Boundary Dataset (WBD), and NHDPlus High Resolution (NHDPlus HR). These geospatial datasets represent the surface water of the United States for mapping and modeling applications.” (Link)
The NHDPlus HR program is particularly enticing for solar developers. Their goal is to produce a nation-wide dataset that simulates stream flows which in return provides waterflow estimates, flood predictions, and the evaluation of landscape on aquatic habitats. “NHDPlus
HR will also provide the hydrography base for the National Water Model, which simulates streamflow volume and velocity over the entire continental United States to help forecasters predict when and where flooding can be expected.” (PDF)
The percentage of tree cover on a given parcel is important to the existing habitat. Some states do allow for timber harvesting to clear space for solar development, however it is usually a last resort for many developers. Other than having "boots on the ground", the best visual for determining tree cover is aerial imagery. A popular form of aerial imagery today is drone imagery. However, drone imagery is cost prohibitive for many firms. The next best source is satellite imagery.
Historically, satellite imagery has been available via a pricey subscription or piecing it together through various state/county sites. Today, however, satellite imagery is complimentary through programs like Google Earth or ESRI ArcGIS Online. ArcGIS Online
allows you to bring all your GIS constraints into one platform and view basemaps such as imagery, topography and transportation.
Distance to Power
The final, and most difficult data to obtain, is distance to power sources. In my opinion, the
best open source data for nationwide power is the Homeland Infrastructure Foundation Level-Data. The open-source data can be found here:
https://gii.dhs.gov/hifld/content/hifld-data-catalog. However, the data can also be found through ESRI's Living Atlas in ArcGIS Online.
The data in ArcGIS Online that I use most commonly in solar energy projects is titled "Electric Power Transmission Lines" and the description says, "Lines are operated at relatively high voltages varying from 69 kV up to 765 kV, and are capable of transmitting large quantities of electricity over long distances. Underground transmission lines are included where sources were available." Its important to keep in mind, most AGOL data can also be exported to ArcGIS Pro or to various formats like shapefile or Google Earth KML.
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