BIPV Facade Trade-off: Solar Fins vs. Daylight

Facade Geometry

Fin tilt angle 35°

Sun elevation 45°

BIPV Glass

Visible light transmittance (VLT) 20%

Glass tint hue 190°

Live Readouts

Power density

0 W/m²

Daily yield

0 kWh/m²/day

Interior daylight transmitted

Incidence angle on fin (cos θ)

0.00

How it works

Each facade fin is a semi-transparent photovoltaic glass panel. Two physical effects fight each other as the glass gets clearer:

P = G0·sin(elev) · cosθ · η_cell·(1 − VLT) · A
θ = angle between sun ray and fin normal
VLT = fraction of visible light the glass lets through

Fin tilt — rotates the panel normal, changing the incidence angle θ between the fin and the sun. cosθ = 0 means the fin is edge-on to the sun (no power, but also no shading of the window behind it); cosθ = 1 means the fin faces the sun directly.
Sun elevation — models the time-of-day sun path. Available irradiance is approximated as G0·sin(elevation), so a low sun near the horizon delivers far less power even at a favourable incidence angle.
VLT (visible light transmittance) — the fraction of light that passes straight through the BIPV glass to light the room instead of being absorbed by the embedded cells. Raising VLT directly lowers electrical efficiency η_eff = η_cell·(1 − VLT): the panel cannot be maximally transparent and maximally opaque-absorbing at the same time. This is the real "beauty vs. energy" trade-off architects face when specifying tinted solar glass — a clearer, more daylit facade always generates less power per square metre.
Tint hue — a cosmetic dichroic-coating colour (real BIPV glass ships in bronze, blue, gold and graphite); it does not change the physics here, only the building's appearance, which is exactly the point of the trade-off.

The two presets show the extremes: steep, dark, sun-facing fins maximise generation; near-flat, highly transparent fins maximise how much daylight reaches the interior.

PV facade fins Sun position

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