This map shows IDNR agricultural lease lands. Large solar arrays may be developed on some these sites. The colors of the dots indicate the preliminary technical and economic feasibility, through the Site Solar Index. The best sites are shown as “Promising” (blue), followed by “Fair” (gray), and then “Poor” (red).
Site Solar Index is based on three criteria: the suitability score, the parcel size, and tree coverage.
● The suitability score is on a scale of 1-5 and accounts for suitability criteria including: competing land uses, land slope, direction of slope, elevation, solar radiation, distance to transmission lines, proximity to dense population, tree coverage, and road density. Suitability score ratings: Promising (>2.75); Fair (2.5-2.75); Poor (<2.5). Click on (Link) to see the reference suitability maps.
● The parcel size determines the upper limit of land available solar. Larger systems have better pricing due to economies of scale. Parcel size ratings: Promising (>30 acres); Fair (10-30 acres); Poor (<10 acres). Parcel size ratings are adjusted to account for acreage within the 100-year floodplain.
● Tree coverage affects feasibility of solar system installation. Tree coverage ratings: Promising (<30% canopy); Fair (30%-50% canopy); Poor (>50% canopy).
System size and cost is determined by how large of a system the land parcel will allow.
Further considerations. Once a site is selected for further study, important “ground truth” factors to verify include:
● Infrastructure. . Large solar systems must connect to the electric grid. Check for high voltage electrical distribution or transmission lines within 1.5 miles of the site. Materials and machinery must be delivered to the site. Check for highway proximity, adequacy of local roads and site access.
● Land. Does the parcel have significant slope or tree coverage? The suitability scoring includes slope and tree coverage, but the algorithm might not account for localized site conditions.
These maps were produced using a variety of metrics to determine a rating system useful for large scale arrays that are larger than 20 acres. The background color displays the ratings of individual dots that are 30x30m each. The points show the average rating of the IDNR AG Lease parcels with provided boundary data. More saturated point colors indicate higher suitability ratings. Ratings are not absolute and there may be localized field conditions that may make a site better or worse than the rating may indicate.
● Further considerations. Once a site is selected for further study, it is important to “ground truth” a site to verify suitability and refine the sizing estimate. Here are a few factors to consider:
● Land cover. Steep slopes and significant tree coverage can impact feasibility. Ditches and areas with standing water are unsuitable.
● Electrical connection. To support a large array, proximity to grid would be beneficial so that the array can be connected.
● Utility delivery provider. Each utility provider has different rules for solar that may affect system sizing and connection complexity and cost.