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HomeMy WebLinkAbout02-22 Glare Study Assessment Report GLARE ASSESSMENT REPORT REDBUD RUN PHOTOVOLTAIC SOLAR ARRAY Frederick County, Virginia Prepared For: ORIDEN POWER Jan 2022 ORIDN21002 Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 2 of 8 Executive Summary Oriden Power is proposing to develop a solar farm at a parcel located northeast of the intersection of Pine Road and Woods Mill Road in Frederick County, VA (the Project). The Project involves the construction of a fixed-tilt ground-mounted PV array, substation, and inverters. Given the proximity to the roadway, VaDOT has requested that a Glare Hazard Analysis be performed to determine any potential glare hazard impacts to the adjacent roadways. Pennoni was commissioned by Oriden Power to conduct this analysis for the specific locations of interest identified within the surrounding region. The analysis utilizes ForgeSolar tools—built with the Solar Glare Hazard Analysis Tool technology (SGHAT), licensed from Sandia National Laboratories—to assess when and where glare may occur and its approximate intensity. This report identifies the potential impact on sensitive receptors adjacent to the Project, in this case, the two roadways bordering the southwestern edges of the property. The model is based on the relative heights and directions of observation paths (route-receptors) as well as the configuration of each PV array (potential glare source). The analysis tools do not account for any weather conditions (clouds, fog, snow, etc.). Additionally, the analysis assumes an unobstructed sight path exists between each receptor and each potential source despite any possible obstructions (fences/structures/vegetation/etc.) that may actually be present. Therefore, prediction of glare impacts by the analysis tools and the results presented within this report will be conservative in this regard. Based on the modeling results, “yellow” glare (glare with a potential for after-image) is likely to occur at several sections along both Woods Mill Road and Pine Road during the early morning hours throughout the spring and summer months with some additional late afternoon glare occurring on sections of Pine Road through spring and summer as well. More comprehensive details of exact times and locations of predicted glare are included in Appendix A. Project Description The project area is comprised of a combination of woodland, open fields, and some minor streams and surface water features. The designated PV arrays are proposed in three major groups. These groups were modeled within the program and further subdivided for a more optimized analysis by the software. The arrays utilize racking fixed at a 30° tilt facing due south (180°). Woods Mill Road and Pine Road were identified as the main areas of interest for the purposes of this study. Pine Road runs in the East-West direction along the southern border of the site and Woods Mill Road runs north-south along the western border of the site. Each of these roads were modelled as route-receptors to evaluate the potential glare impacts along the length of each route. Woods Mill Road was modeled as a “one-way” route-receptor because an observer travelling in the southern direction along this path would be facing the northern (rear) side of the PV modules. The rear face of each module is angled sharply towards the ground and would not be subjected to the glare impacts as observed from the southern (front) side of the array. The northern array is greater than 500’ from the roadway and located in a densely vegetated woodland area behind wooded residential lots. Due to this the northern extents of Woods Mill Road were also excluded from this analysis at the direction of Oriden Power. No airports were Identified within a 2-mile radius of the project location, so flight paths and air traffic control towers (ATCTs) were omitted from this analysis. Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 3 of 8 Figure 1: Approximate project location. Glare Effects Glint, a momentary flash, and glare, a continuous source of bright light, are caused by significant contrast between a light source and background illuminance. Aside from causing discomfort to the viewer, glare can be a distraction and leave after-images in the viewer’s vision. Glare hazard is the human impact caused by exposure to reflected light. A PV array can contribute to glare hazard through:  Reflectivity of surfaces  Angle of incidence  Strength of light source  Receptors (viewers)  Distance PV modules are designed to absorb as much light as possible, but reflection can still occur at high angles of incidence. For a fixed tilt system, reflection decreases in the middle of the day as the sun casts light more directly onto the surface of each module and increases as the sun is rising or setting due to the increased angle of light projected toward the module surface. The ocular impact of glare is visualized with a Glare Hazard Plot of the scale of glare effects:  Low potential for after-image (green) o Glare is noticeable but will not cause significant adverse effects o e.g., sunlight reflection off a reflective surface such as a building window or car windshield  Potential for temporary after-image (yellow) o Significant effects may require mitigation o e.g., the effect after viewing a camera flash in a dim room  Potential for retinal burn (red) o Potential for permanent eye damage that will require mitigation o Typically, not possible for PV glare because PV modules do not focus reflected sunlight Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 4 of 8 Figure 2: Glare Hazard Plot, with impact of direct viewing of sun, for reference. Impact Assessment Solar Glare Hazard Analysis Tool This Glare Assessment uses the ForgeSolar GlareGauge comprehensive solar glare analysis tool. This tool was developed by Sandia National Laboratories, licensed to ForgeSolar, and is globally recognized as the industry standard assessment tool for assessing glare from solar developments. SGHAT incorporates the latitude, longitude, and elevation of the site in conjunction with proprietary algorithms to calculate the sun angle for each minute throughout the year. In combination with inputs of project-specific location, PV module orientation, and reflectivity, the potential glare magnitude and duration is modeled at each receptor as defined by the user. PV Array Configuration The base array configuration models a fixed-tilt racking system with rows of modules running in the east-west direction and the array surface facing south with a 30° tilt. The model assumes modules with smooth glass and an anti-reflective coating. The height to the midpoint of the array was modeled at 64” above grade per Oriden Power. The array segments are pictured in Figure 3 below and detailed in the ForgeSolar Glare Analysis Results (Appendix A). The SGHAT model considers the relative elevation of each point a user identifies when building an array shape. The program converts each array shape into a single plane with an average slope based on the elevations of the user defined points. This plane is then evaluated as a footprint filled with infinitesimally small modules reflecting sunlight in the trajectory of the tilt and orientation. Essentially, all space within a defined array shape is evaluated as a potential glare source. Additionally, ForgeSolar does not rigorously represent the detailed geometry of a system; detailed features such as gaps between modules and rows, or variations in height of the PV array and support structures may impact actual glare results. In addition, any potential shading on the array from nearby structures, terrain features, vegetation, etc. (including array inter-row shading) are not considered in the analysis. All of these factors will result in more conservative glare predictions. Observation Points The observation locations chosen for assessment were based on the two roadways adjacent to the project site (as previously identified). These roads were modeled as a continuous pathway (route-receptor) and are evaluated along their entire length with respect to the impact of glare from the arrays. The route-receptor height was modelled to be 3’-6” above the surface of the ground as indicated in the AASHTO GreenBook (7th Ed. 2018) to reflect the average eye height of drivers in passenger vehicles. Route- receptors and the overall array configuration (as modeled in the design software) is depicted in Figure 3. Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 5 of 8 Figure 3: Overall site plan as modelled. PV array areas (dark blue) and route-receptors (light blue). Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 6 of 8 Glare Assessment According to the results of the analysis, Portions of both Woods Mill Road and Pine Road are likely to receive periods of exposure to “green” and “yellow” glare impacts with the latter having a higher potential to produce after-images within the observer’s vision. Woods Mill Road: results indicate varying periods of green and yellow glare in the morning ranging between the hours of: 5:45AM – 7:30AM from mid-April to mid-August. Pine Road: results indicate varying periods of green and yellow glare in the morning ranging between the hours of: 5:45AM – 7:30AM from mid-April to late August, and in the afternoon ranging between the hours of: 5:00PM – 6:30PM from early April to mid-September. A summary of the total annual glare for each array is tabulated in Figure 4 below. Additionally, an example of the annual predicted glare occurrence and duration is also available for Southern Array “South PV 4” as shown in Figure 5 for reference. More detailed information for each analyzed array is available in Appendix A. Figure 4: Summary of results: Annual predicted glare totals for each array Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 7 of 8 Figure 5: Annual predicted glare occurrence and duration graphs for array “South PV 4” In addition to the SGHAT tool, Forge Solar also offers the ability to perform PV array optimizations via their “GlaReduce” tool. This feature is used to iteratively test alternate configurations of the PV array based on a range of user defined tilts and orientations. Due to subscription limitations within the ForgeSolar software license (Enterprise tier),only a limited number of GlaReduce simulations are possible for a given project. Therefore, GlaReduce was performed on just a sample of the modeled arrays. This evaluation was conducted to determine if altering the physical module geometry would have a significant impact to the yellow glare, with the ultimate goal of eliminating yellow glare entirely. The evaluation yielded mixed results with respect to a consistent resolution for reducing yellow glare. For example, within the southern group of subarrays, some arrays showed no possibility to eliminate yellow glare regardless of the configuration inputs, while others showed some elimination of yellow glare, but only at the extreme extents of the available configuration range. To further complicate matters, any subtle modifications to the configuration of a PV array will have some level of production impacts for the system. Utilizing an extreme modification of an arrays tilt or orientation to reduce glare would likely have a proportionately large impact on its overall production. However, PV system production (and any potential impacts) are beyond the scope of this report. Two samples of the GlaReduce results can be seen below in Figure 6. Glare Assessment Report Redbud Run Photovoltaic Solar Array ORIDN21002 8 of 8 Figure 6: GlaReduce Results for arrays “South PV 4” and “South PV 3” respectively Conclusion Utilizing the ForgeSolar SGHAT tools, the resulting glare assessment has identified periods of glare with potential for temporary after-image effects for both Woods Mill Road and Pine Road. The glare is predicted to occur during the early morning and/or late afternoon hours mostly through spring and summer months. While these results show significant glare potential, ForgeSolar acknowledges that there are several aspects and conditions of the modeling program that are known to produce a conservative result. Nonetheless, it is beneficial to understand the possible implications of glare as well as the ability to predict when, where, and how long the impacts may occur. ForgeSolar does offer limited alternatives for reducing glare (via changes to the physical orientation of the PV modules), however, it appears that for this particular analysis, any proposed alternatives may yield inconsistent results between each of the modeled subarrays. Additionally, these alternatives may entail radical changes to the overall system configuration. Though the software cannot make any other specific recommendations to reduce glare from the perspective of the receptors (such as physical barriers or screening). The results may be useful to guide development of glare reduction strategies and locations to obscure view of the PV system from the receptors.