Lighting

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Lighting is vital for a colony. A colony will have a limited number of windows, so artificial lighting may be required at all times. Plants in greenhouses will probably need to be lit artificially to supplement natural light. Rovers must have headlamps for driving at night or during dust storms.


Types of lighting

Incandescent

Most light bulbs on Earth were incandescent until recently. Due to their relatively low efficiency, incandescent lights are being phased out all over the world.[1] In most commercial installation incandescent light bulbs have been replaced by fluorescents, that are themselves being replaced by LEDs.

Incandescence is a term usually reserved for a solid that emits light as it is heated. In an incandescent light-bulb a metal filament (Usually tungsten, but carbon has also been used in the past,) is heated to around 3000C. A glass or quartz bulb is fitted around the filament and the air evacuated or replaced by an inert gas, because the filament would otherwise oxidize and burn.

Halogen

Halogen light are a variation on incandescent lights, where the filament can last longer due to chemical interactions between the tungsten element and the halogen gas in the bulb.

Fluorescent

Fluorescent lights use a phosphorous coating inside the lamp tube to transform the ultraviolet light emitted by an ionised plasma in the tube into visible light.

Light Emitting Diode (LED)

LED are energy efficient, and produce little heat compared to incandescent, fluorescent, and halogen lights. They use the light emitted from a semi conductor in visible wavelengths and combine red green and blue components to produce white light.[2]

LEDs in 2019 can produce about 220 lumens per watt, while incandescent light bulbs produce only about 14 lumens per watt and fluorescents 80 lumens per watt.[3]

Human response to light

Humans have two types of vision, color and low-light. Once the vision has adjusted to low light, the average human is able to function well in the light of the full moon, but without the ability to see in color.

Health

The proper wavelengths of light are needed by humans to produce Vitamin D. On Earth, about 15 minutes under the noon sun, 3 times a week, is enough to produce the required vitamin D.[4] On Mars, the exposure time would need to be longer. Most type of glass screen ultraviolet light, so exposure under glass would not produce vitamin D. Using ultraviolet light from artificial sources would product the same effect as the sun.

Certain lights, emulating natural sunlight, are used to treat Seasonal Affective Disorder.

Uses

Illumination

The primary use of lighting is illumination of a settlement. A well-lit environment is vital for the morale and safety of the residents. See table below for standard lighting levels.

Agriculture

Many plants require more sunlight than is available on the martian surface. Dust storms can also obscure the sun for months at a time. Artificial lighting is needed to at least augment the natural light.

Interior grow rooms use artificial light for plant production. This technology was developed for the production of Cannabis in closed environments but is applicable to all indoor grown plants. The most common power used for these installations is 300-600 W/m2, or about one quarter to one half the power of full sunlight.

Lighting levels

Common outdoor light levels[5]
Condition Illumination Power intensity
ftcd lux W/m2 (W/ft2)
Sunlight 10000 107 527 1300 (120)
Full daylight 1000 10 752 130 (12)
Overcast day 100 1 075 13-18 (1,3-1,8)
Very dark day 10 107
Twilight 1 10,8
Deep twilight 0,1 1,1
Full Moon 0,01 0,11
Quarter moon 0,001 0,011
Starlight 0,0001 0,0011
Overcast night 0,00001 0,00011

The table below provides recommended light levels from the IESNA Lighting Handbook and LPD levels from the IECC 2015

ROOM TYPE LIGHT LEVEL (FOOT CANDLES) LIGHT LEVEL (LUX) IECC 2015 LIGHTING POWER DENSITY

Watts/m2 (WATTS PER SF)

Bedroom - Dormitory 20-30 FC 200-300 lux 4 (0.38)
Cafeteria - Eating 20-30 FC 200-300 lux 7 (0.65)
Classroom - General 30-50 FC 300-500 lux 13 (1.24)
Conference Room 30-50 FC 300-500 lux 13 (1.23)
Corridor 5-10 FC 50-100 lux 7 (0.66)
Exhibit Space 30-50 FC 300-500 lux 16 (1.45)
Gymnasium - Exercise / Workout 20-30 FC 200-300 lux 7,8 (0.72)
Gymnasium - Sports / Games 30-50 FC 300-500 lux 13 (1.20)
Kitchen / Food Prep 30-75 FC 300-750 lux 13 (1.21)
Laboratory (Classroom) 50-75 FC 500-750 lux 16 (1.43)
Laboratory (Professional) 75-120 FC 750-1200 lux 19 (1.81)
Library - Stacks 20-50 FC 200-500 lux 18 (1.71)
Library - Reading / Studying 30-50 FC 300-500 lux 11 (1.06)
Loading Dock 10-30 FC 100-300 lux 5 (0.47)
Lobby - Office/General 20-30 FC 200-300 lux 10 (0.90)
Locker Room 10-30 FC 100-300 lux 8 (0.75)
Lounge / Breakroom 10-30 FC 100-300 lux 8 (0.73)
Mechanical / Electrical Room 20-50 FC 200-500 lux 10 (0.95)
Office - Open 30-50 FC 300-500 lux 11 (0.98)
Office - Private / Closed 30-50 FC 300-500 lux 12 (1.11)
Parking - Interior 5-10 FC 50-100 lux 2 (0.19)
Restroom / Toilet 10-30 FC 100-300 lux 11 (0.98)
Retail Sales 20-50 FC 200-500 lux 17 (1.59)
Stairway 5-10 FC 50-100 lux 8 (0.69)
Storage Room - General 5-20 FC 50-200 lux 7 (0.63)
Workshop 30-75 FC 300-750 lux 17 (1.59)

References