Frequently Asked Questions
No - independent research by a national laboratory determined that photovoltaic modules can reflect more than 60% of incoming sunlight at certain times of day. The reflectivity of a material is not constant - it depends on the material's properties and other optical parameters, including the angle of incoming light.
For example, the claim that PV arrays only reflect 5% of light assumes that the modules directly face the sun. Panels lying flat can actually reflect 10x as much at times near sunrise and sunset.
For a deeper dive into the details of solar PV glare, see the Help page.
ForgeSolar is a licensed implementation of analysis software designed by a national laboratory to quantify and understand potential solar glare hazards for pilots, motorists, and other observers.
The PV module profile determines the reflectance curve and slope error of the modules during analysis. Modules that are more textured or that have anti-reflective coatings may have reduced reflectivity but a higher slope error, indicating more diffuse reflections and beam spread. This can result in more overall minutes of glare predicted. In some cases this expanded glare may display lower potential for a temporary after-image.
This behavior can be visualized with the glare hazard plot below. A more textured module may have reduced reflectivity, yielding lower retinal irradiance on the y-axis. This decrease can cause "yellow" glare to become "green" as its retinal irradiance decreases. However, the textured module may also have a higher slope error. This may result in a larger glare spot size, corresponding to an increase in the subtended source angle represented by the x-axis.
See the Help page for more details on PV parameters.
Analysis results may exhibit some variance between runs due to the analytical simulation method modeling outgoing glare conical emanations. Since it's inception, the SGHAT/ForgeSolar methodology has utilized an analytical approach which balances speed with accuracy, to deliver qualitative results in a timely fashion. If a more rigorous outcome is required, such as quantitative minute-by-minute (or sub-minute) resolution, a custom ray-tracing methodology should be used.
The Version 2 methodology enhancements included in the 2021A update substantially reduce this variance in most cases.
The PV component is designed to simulate PV module reflections. The Vertical Surface component can be used to simulate reflections from a vertical surface, such as a glass building.
The PV component can approximate other materials as a workaround because the underlying methodology uses an analytical approach and does not rigorously simulate the geometry of PV modules, including blocking and shading. The total reflectivity and slope error can be altered to mimic reflection and scattering from different materials. For example, a metal roof could be modeled with a slope error around 100 mrad. Solar reflectance values based on the material and surface finish could be determined from external sources.
A realistic comparison of yellow glare is the direct viewing of a brief camera flash. The camera flash "sticks" in one's vision temporarily. Similarly, yellow glare is defined as a source with potential to cause a temporary after-image. Conversely, green glare has low potential to cause an after-image.
Regarding analysis of bifacial panels, which produce solar power from both sides of the panel: if the sun is within 90-deg of the underside panel normal vector (i.e. sunlight directly hits underside) then the panels may cause glare. ForgeSolar does not currently evaluate modules with a tilt beyond 90-deg from flat. If the bifacial panel underside only captures diffuse light and cannot "see" the sun directly then it would not need to be analyzed regarding the SGHAT/ForgeSolar methodology.
This typically occurs when a site configuration is saved in the editor after the analysis has been submitted. An unmodified site configuration should not be saved after submitting an analysis. Results are saved automatically. Furthermore, the system deletes any existing results when a site configuration is saved, to ensure that a modified site configuration is not retained alongside stale results.
The general workflow when editing a site is: edit site > save > analyze.
Subscriptions & Licensing
The 2021A Update changed the subscription and licensing structure. Whereas prior licenses determined monthly analysis usage, the new structure is project-based, with higher tiers providing project credits.
The Professional subscription provides 1 Basic project credit each monthly period. If this project tier is insufficient for your needs, consider upgrading to an Enterprise subscription to receive 1 Advanced project credit in future billing periods.
To upgrade an existing Basic project to Advanced, purchase a Project Upgrade add-on.
Basic projects can be upgraded to Advanced by purchasing a Project Upgrade Add-on. A subscription upgrade is not required. To upgrade a Basic project or Basic project credit, follow these steps:
- If starting with a Basic project credit, first use it to
create a Basic project.
(Project parameters like system size can be adjusted later.)
- Navigate to the Add-on Purchase page.
- Select Project Tier Upgrade from the Select Add-on field.
- Select the name of the Basic project that you want to upgrade from the Project receiving Add-on input.
- Complete the transaction
Once the transaction is complete, the project will be upgrade to Advanced. You can then modify project settings, like system size, to match the Advanced project parameters.
The Data Access tier provides read-only access to existing analysis data. This tier is typically used by existing users who don't need to conduct analyses and only need to review or access past work.
The Professional and Enterprise tiers provide analysis tool access and project credits. The Pricing page and Help page have more info on the available tiers and project types. Subscriptions can be upgraded on the Account page.
Invoicing is available for subscriptions billed on a quarterly or annual billing cycle. Monthly subscriptions must be purchased on the website via card.
New projects can be created with project credits. Credits are provided to Professional and Enterprise users each billing period. Additional project credits can also be purchased as add-ons.
ForgeSolar includes GlareGauge, the leading solar glare analysis tool used globally every day. ForgeSolar is based on the Solar Glare Hazard Analysis Tool ("SGHAT") licensed from Sandia National Laboratories. Our tools meet the FAA standards for glare analysis.