Approximately 4 flood lighting projectors (each 215 W) are needed to illuminate the building frontage with the desired illuminance.
The Required Luminous Flux:
Area to be illuminated (A) = 50m × 15m = 750 m²
Desired illumination (E) = 100 lux
Coefficient of utilization (CU) = 0.5
Depreciation factor (DF) = 1.5
Waste light factor (WLF) = 1.2
Luminous flux (Φ) = E × A × CU × DF × WLF
= 100 lux × 750 m² × 0.5 × 1.5 × 1.2
= 56250 lm
The Required Projector Power:
Choose a suitable projector type with known lumen output per watt (Llm/W).
Let's assume Llm/W = 75.
Projector power (P) = Φ / Llm/W
= 56250 lm / 75 Llm/W
= 750 W
Determine Number of Projectors:
Divide the total required power by the individual projector power.
Number of projectors (N) = Total power / Projector power
= 750 W / 215 W (assuming a commercially available 215 W projector)
≈ 3.48 ≈ 4
Sketching the Projectors:
Projectors should be positioned at 25 meters away from the building facade.
Maintain equal spacing between projectors to ensure even coverage.
Projectors should have adjustable tilt and pan angles for fine-tuning the light distribution.
Question:-
A building frontage 50m × 15m is to be illuminated by flood lighting projectors situated 25 meters away. If the illumination is 100 lux, coefficient of utilization 0.5, depreciation factor 1.5, waste light factor 1.2, estimate the number and size of projectors. Sketch the projectors recommended indicating the usual adjustments provided.