This 2D model computes the panel's cross-section directly with ray geometry, rather than reusing a closed-form 3D scene. The front and rear faces of a tilted plate each have an exact view factor to an unobstructed, infinite ground plane — a standard result from radiative heat-transfer theory:
Front view factor (ideal): F_f = (1 − cosβ) / 2
Rear view factor (ideal): F_r,ideal = (1 + cosβ) / 2
Incidence angle (exact): cosθᵢ = max(0, sin(β + elev))
Real arrays aren't isolated over infinite ground, though — the next row's own low support rail partially blocks the rear face's view of distant ground. This simulator ray-traces that directly: it sweeps ~4000 sample directions across the rear hemisphere from the panel's hinge point and tests each one geometrically against a modeled rail (height 0.15 m, 1.2 m behind the array) to see whether it clears the rail before reaching the ground. The fraction that gets through is the occlusion clearance:
for each sample angle φ in the rear hemisphere:
ray = hinge point + t·(cosφ, sinφ)
if ray reaches ground before the rail's x position → clear (near field)
else check ray height at the rail's x position vs rail height → clear or blocked
occlusion = (# clear rays) / (# total rear-hemisphere rays)
F_r = F_r,ideal · occlusion
This replaces an empirical height-correction curve with a genuine visibility computation: a taller mount lets more sample rays clear the rail before they reach the ground, so the effective rear view factor rises smoothly toward its ideal geometric value as height increases — grounded in ray/obstacle intersection rather than a fitted exponential.
Front and rear irradiance then follow directly: E_f = GHI·(cosθᵢ + ρ·F_f), E_r = GHI·ρ·F_r, with rear power scaled by the bifaciality factor φ (the rear cell's lower quantum efficiency relative to the front).
- Ground material — sets albedo ρ. Snow and light gravel reflect far more light than asphalt or grass.
- Mounting height — raises the vantage point above the neighboring row's rail, letting more of the rear hemisphere's rays clear it.
- Tilt angle — sets both the ideal view factors and which hemisphere of directions counts as "rear".
- Sun elevation — sets the incidence angle on the front face via the exact θᵢ formula above, and (through GHI) the overall light level.
The lower chart plots front, rear and total power against sun elevation for the current geometry, with a marker at the slider's current value — the same computation run continuously across the whole elevation range.