21 Dec · Winter · 12:00
6 s/day · 14-day jumps
Solar time, not local clock time.
Tracks the geometric Sun for maximum direct-beam alignment. Electricity output is not estimated.
GHI estimates light on an unshaded horizontal surface, not at X. Sunrise/set assume a level horizon and standard refraction. Haurwitz model ↗
SOLAR ANALYSIS
Where the sun path enters the filled outline, X is shaded.
Click the map to set the date and time. 15-minute steps.
Calculating annual shade…
BUILDING GEOMETRY
Roof-point angles define the obstruction on the sun-path chart.
—
Chart/table azimuth: S = 0°, east −, west +. Scene bearing: clockwise from N. Distances are horizontal.
HOW IT WORKS
Choose a location, move the date and solar-time sliders, or press Play. Both views update together. Expand Building geometry to change the neighbour.
Click the scene to use arrow keys: pan in 3D, Plan or Elevation; hold Shift to orbit. In Look around, drag or use arrows to turn the camera. Scroll to zoom. The compass’s fixed pointer marks your viewing direction. Follow the sun tracks the Sun; Fit scene restores the building view.
The sun-path chart shows the neighbour’s front wall as seen from X. A geometric solar ray inside that outline is blocked. “Clear” means the neighbour does not block X; it does not guarantee light on the building’s facade.
The solar panel tracks on two axes. Tilt = 90° − Sun altitude; facing follows the Sun’s bearing. Incidence is 0° when tracking: rays hit its front face perpendicularly. At night it parks flat; directly overhead, any bearing works.
Dates use 2025, a 365-day reference year. NOAA/Meeus equations calculate declination at 12:00 UTC for each date, then hold it fixed during that solar day. Solar noon is 12:00 by definition. Civil time zones and equation-of-time conversion are outside this model.
Building rays, angles and the globe’s cyan boundary use the geometric Sun centre. Sunrise/set use a centre altitude of −0.833°, allowing for the solar disk and standard refraction on a level horizon. This makes the sunrise-to-sunset day slightly longer than the globe’s geometric day. Actual rise/set varies with atmosphere and terrain, especially near the poles.
Haurwitz estimates clear-sky global horizontal irradiance (GHI) using refraction-corrected elevation. It excludes clouds and local atmospheric/site inputs; it is not measured irradiance or light on X.
Only the neighbour’s front rectangle obstructs the numerical ray. Building depth, scenery and self-shadow are outside that test. Sky colors, clouds, vegetation and GPU shadows are illustrative. The subtle dawn/dusk palettes do not predict weather. Annual shading uses 15-minute samples; daily intervals have about one-minute resolution.
Panel alignment maximizes the geometric direct-beam projection on an ideal, freely moving two-axis tracker. It does not optimize diffuse light, avoid site shadows or predict electricity. Refraction, weather, panel efficiency, temperature, motor limits and wind-stow controls are outside the panel model. Flat parking is a demonstration choice.
a: height of X; b: perpendicular wall separation; c: neighbour height; d: B–A; e: B–D; f: B–C. C lies due south; centre orientation is atan(f/b). Chart/table azimuth starts at south, west positive. Scene bearing starts at north, clockwise. Sun bearing is undefined at a pole or directly overhead. At a pole, the compass and ground directions use a chosen reference meridian, marked REF.
Geometry reference: Soteris A. Kalogirou, Solar Energy Engineering: Processes and Systems, 1st edition, Academic Press, 2009. Sections 2.2.2–2.2.3 and Example 2.8, pp. 68–72.
NOAA solar calculations · pvlib / Haurwitz irradiance · NASA seasons · NOAA sky colors
Panel geometry: pvlib’s angle of incidence and direct-beam projection.
Earth texture: NASA Earth Observatory, Blue Marble: Next Generation, August 2004. Built with Three.js. Building study inspired by an AASTU Renewable Energy Engineering exercise.
A PLACE ON EARTH
Search for a place, or click the map to place your pin.
Latitude sets the sun path. Longitude positions you on Earth.