Methodology, assumptions, limitations, and references for each tool in the Taylor Scott Solar PV Toolset.
The Taylor Scott Solar PV Toolset is a set of free, browser-based utilities developed for use in solar photovoltaic design, feasibility analysis, and planning. The tools were initially created for my personal use and to fill gaps that I used every day. They should be considered to be in beta and I make no claim on the accuracy of their output. The tools are provided for use under the terms of service.
All tools run entirely in the browser. No data is sent to a server, no account is required, and no information is stored or tracked. Calculations are performed client-side using JavaScript.
Developed by Taylor Scott, solar PV consultant based in Ontario, Canada. Taylor Scott Solar Consulting provides engineering and technical advisory services for commercial and industrial PV projects across Canada.
Estimates annual energy losses from snow accumulation on rooftop photovoltaic arrays using two independent empirical and physics-based models.
Snow accumulation on PV modules reduces energy production by blocking incident irradiance. This tool quantifies that loss as a percentage of annual yield, broken down by month, using Canadian climate data and established loss estimation models. It is intended for use in yield reports, feasibility studies, and owner documentation where a defensible snow loss figure is required.
Two independent models are calculated in parallel, each producing a monthly and annual loss estimate:
Simulates snow cover on an hourly basis using ERA5 reanalysis data. Fresh snowfall events trigger full module coverage. Snow slides off at a rate proportional to incident irradiance, modulated by a sliding coefficient that differs for ground-mounted and roof-mounted systems. Coverage fraction drives fractional loss at each hour.
Default sliding coefficients: Ground = 6.0, Roof = 1.97 (from Marion et al., 2013). These can be overridden in the Array & Model Inputs tab.
A regression-based empirical model driven by monthly climate normals: total snowfall, average temperature, average humidity, and plane-of-array irradiance. Calibrated against measured field data and suitable where hourly data is unavailable or a simpler monthly summary is preferred.
Default constants: C₁ = 57,000 · C₂ = 0.50 · Pile angle = 40° (from Townsend et al., 2013).
| Source | Variables | Period |
|---|---|---|
| EC Climate Normals | Monthly snowfall, snow days, mean temperature, relative humidity — from the nearest Environment Canada climate station | 1981–2010 normals |
| ERA5 Reanalysis | Hourly GHI, DNI, DHI, temperature, snowfall — used for Marion hourly model and as fallback where EC data is unavailable | User-defined study period (5–10 years recommended) |
| User override | Any monthly climate value can be manually edited to reflect project-specific or locally measured data | — |
| Input | Description |
|---|---|
| Latitude / Longitude | Site coordinates in decimal degrees — used for EC station search and ERA5 data extraction |
| Study period | Start and end year for ERA5 hourly data (used in Marion model) |
| Module tilt | Array tilt angle from horizontal — affects irradiance on POA and snow sliding |
| Module azimuth | Array facing direction — used for ERA5 POA calculation |
| Mount type | Roof-mounted or ground-mounted — selects appropriate Marion sliding coefficient default |
| Row length | Module dimension along the slope — used in Townsend pile geometry calculation |
| Lower edge height | Height of panel lower edge above grade — drives Townsend ground-interference term |
Calculates the shadow profile geometry of a planar obstruction relative to a solar array and outputs AutoCAD-ready coordinate sets for use in design drawing packages.
Roof-mounted PV arrays frequently include setback zones around obstructions such as HVAC equipment, skylights, parapets, and roof penetrations. Accurately plotting the shaded footprint of each obstruction requires solar geometry calculations that are time-consuming to perform manually.
This tool calculates the shade block coordinate polygon for a given obstruction and outputs it as an AutoCAD polyline script, ready to paste into a drawing file. It is designed for use in roof layout drawings, permit packages, and shade analysis documentation.
The tool computes the sun's altitude and azimuth angles for each hour of the day at each date in the selected date range, for the specified site latitude and longitude. For each solar position, it calculates the shadow cast by the obstruction (defined by its width, depth, and height) onto the roof plane.
The outer boundary of all shadow positions across the specified date and time range forms the shade block polygon. This polygon is then expressed as Cartesian coordinates relative to the obstruction base, which can be placed in an AutoCAD drawing by running the generated script.
Solar position is calculated using standard astronomical algorithms (declination, hour angle, altitude, and azimuth). No terrain shading or diffuse irradiance modelling is included — the tool models direct-beam shadow geometry only.
| Input | Description |
|---|---|
| Latitude / Longitude | Site coordinates — used to compute local solar position throughout the day and year |
| Date range | Start and end dates for the shadow analysis — typically the design period (e.g., winter solstice to summer solstice) |
| Time range | Start and end hours of day — constrains which sun positions are included in the shadow envelope |
| Obstruction width | Lateral dimension of the obstruction, perpendicular to the primary shadow axis |
| Obstruction depth | Dimension of the obstruction in the direction facing the array |
| Obstruction height | Height of the top of the obstruction above the array plane — primary driver of shadow extent |
| Array tilt | Tilt of the receiving surface — affects the projected shadow geometry on a tilted plane |
| Array azimuth | Facing direction of the array — used to orient the output coordinate system |
These tools run entirely in the browser. No inputs, outputs, or usage data are transmitted to any server. There are no cookies, analytics, or user accounts.
Both tools offer downloadable outputs (CSV reports and AutoCAD scripts respectively). Downloaded files are generated locally in the browser and are not transmitted externally.
All results produced by these tools are estimates intended for preliminary analysis, planning, and documentation support. They are not certified engineering calculations and should not be relied upon as a substitute for professional engineering review, site-specific assessment, or verified design analysis. See the full engineering disclaimer.
The tools, their source code, calculation methods, and design are the property of Taylor Scott. Use is subject to the Terms of Use. Results may be used in professional work without restriction; reproduction or redistribution of the tool itself requires written permission.