SEDAC recently conducted a feasibility study to determine where the Illinois Department of Natural Resources could develop solar on their state lands. As part of this analysis, we developed a method to rapidly pre-screen lands for solar energy generation potential that we applied to IDNR lands. This tool can be used for other agencies or organizations that are seeking to develop large-scale solar projects on land holdings.

After reviewing the literature on solar suitability and consulting with solar developers, we identified a set of suitability criteria and assigned weights to these criteria. Criteria included solar radiation, slope percentage, aspect, elevation, land use, population density, accessibility to road networks, distance to transmission lines, and crop productivity.

SEDAC analyzed 166 million points, each representing a 30m by 30m cell in Illinois. First, we eliminated points in 100-year flood plains, bodies of water, or in protected natural lands. All remaining points received a score of 1 to 5 for each of the 9 criteria (higher scores indicated greater suitability). The individual attribute scores were combined into a combined suitability score for each point (also from 1 to 5). The combined suitability scores for each point across the state ranged from a low of 1.08 to a high of 4.185.

The figures below, from Illinois IDNR site maps, provide examples of how the tool can be used. In the maps on top, the black areas indicate excluded points: bodies of water, areas in the 100-year floodplain, and protected areas.  Green areas indicate points with higher solar suitability scores, and yellow and red areas indicate points with lower solar suitability scores. The maps on the bottom show an aerial view of the same sites. With this tool, we were able to identify plots of land (outlined in blue) that were large enough and suitable enough for community or utility-scale solar arrays.

While this tool is useful to quickly screen for site suitability, we found that it was important to work with stakeholders and "ground truth" our results to make sure that the high suitability sites generated by the tool were appropriate for solar development. Stakeholders are often aware of other factors that can influence the suitability of specific sites.

This tool is likely to be useful for many state agencies or large land owners who are seeking a way to rapidly screen large land holdings for solar development suitability. Contact us if you'd like to know more.