Artificial Lighting – Exam Review Notes

Definition

  • Artificial lighting: illumination produced by electricity or fuel combustion.

Goals & Main Functions

  • Provide adequate, comfortable light for tasks, movement, and aesthetic display.
  • Equipment should be efficient, unobtrusive, and cost-/energy-effective.

Advantages / Disadvantages (General)

  • Advantages: easy on/off, dimmable, 24-h use, flexible design, varied colours.
  • Disadvantages: higher capital/energy cost, maintenance, potential colour confusion.

Lamp Properties

  • Luminous efficacy lm/W=luminous fluxpower\text{lm/W}=\frac{\text{luminous flux}}{\text{power}}.
  • Life: output depreciates; group relamp on schedule.
  • Colour temperature: referenced to “black-body”; expressed in K\text{K}.
  • Colour rendering: ability to reveal true surface colours vs. reference (daylight).

Lamp Selection – Key Criteria

  • Required illuminance & space use.
  • Supply voltage stability; ambient T & humidity; HVAC impact.
  • Colour rendition & temperature, life, cost, efficacy/depreciation.
  • Control needs & energy-saving devices.

Main Lamp Categories

• Incandescent (thermal)
• Discharge (low/high pressure, fluorescent, HID, sodium, mercury, metal-halide)
• Halogen
• LED (solid-state)

Incandescent

  • Tungsten filament ≈2200∘!C\approx2200^{\circ}!\text{C}; straight, c, cc (most efficient).
  • Pros: low cost, instant start, good colour, simple dimming.
  • Cons: low efficacy (≈8–20 lm/W8–20\,\text{lm/W}), short life, heat gain, voltage sensitive.

Fluorescent

  • Low-pressure mercury + phosphor → UV → visible.
  • Components: hot/cold cathodes, inert gas (Ar), Hg vapour, phosphor.
  • Efficacy 40–85 lm/W40–85\,\text{lm/W} (incl. ballast); life 6,000–15,000 h6{,}000–15{,}000\,\text{h}.
  • Needs ballast; high-frequency operation boosts efficacy.
  • Pros: energy-efficient, long life, low running cost.
  • Con: higher initial cost.

High-Intensity Discharge (HID)

  • Compact, point-like, 50–100 lm/W50–100\,\text{lm/W}; needs warm-up & ballast.
  • Types: metal-halide, high-pressure sodium, mercury.

LED

  • Solid-state; rapidly improving; ideal for signalling, colour effects, exit signs.

Lighting Control Methods

  • Timers, daylight sensors, occupancy sensors, local switching.

Luminaires

  • Device housing lamp, wiring, support. Fixtures are fixed luminaires.
  • Distribution categories (CIE):
    • Direct (0–10 % up)
    • Semi-Direct (10–40 % up)
    • General Diffuse (40–60 % both)
    • Direct-Indirect (≈50 %/50 %)
    • Semi-Indirect (60–90 % up)
    • Indirect (90–100 % up)
  • Light Output Ratio LOR=luminaire outputlamp output\text{LOR}=\frac{\text{luminaire output}}{\text{lamp output}} with DLOR+ULOR=LOR\text{DLOR}+\text{ULOR}=\text{LOR}.
  • Common styles: recessed, ceiling-mounted, track-mounted, wall, portable, pendant.

Lighting Effects on Space Perception

  • Spaciousness: bright, uniform ceilings/walls.
  • Visual clarity: bright horizontals, controlled shadows.
  • Relaxation: warm, non-uniform wall lighting.
  • Privacy: low, non-uniform lighting; brighter background.

PSALI (Permanent Supplementary Artificial Lighting of Interiors)

  • Integrates daylight with continuous artificial supplement.
  • Benefits: deeper floor plates, energy & heat loss reduction.
  • Design factors:
    • Gradient of illuminance rising toward windows.
    • Lamp colour 4000–6500 K4000–6500\,\text{K} to match daylight.
    • Photo-electric switching/dimming.

Daylight–Electric Coordination Guidelines

  • Plan electric lighting concurrently with daylight strategy (task/ambient).
  • Use high-reflectance surfaces; align fixture rows with windows.
  • Hardware: 32 W32\,\text{W} T8 tri-phosphor lamps + dimming ballasts; avoid HID dimming.
  • Visual comfort: target VCP ≥80%80\% for VDT work; ambient ≤300 lx300\,\text{lx} with task lights.
  • Mitigate window glare by brightening rear walls/ceilings.