LightingDesign
Lighting Design
To reduce energy consumption all lighting except in the engine room should be DCDirect current, fitted with dimmer switches where appropriate. The engine room can have dual DC and ACAlternating current fluorescent lighting. The latter will make it easier to work in the engine room when connected to shore power, especially if the DC system must be disconnected. The long tube length of fluorescents will give more even illumination than other types of lighting. However, the DC lighting should give sufficient illumination for work at sea.
All of the light types discussed below are available in low-voltage DC. Dimmer switches can be used with most tungsten and halogen lights but only certain types of fluorescent. Make sure the dimmer switch is compatible with the light and its wattage. In a marine environment, use double-pin ungrounded lamps for all types.
Lighting must satisfy several criteria:
- Illumination (light output)
- Colour (biological and visual comfort)
- Energy efficiency (amount of light output for a given energy input)
- Application (ambient, accent, task and utility)
It’sSecond tempting to start by discussing the application of lights, because this is like not running out of hot water or never having the toilet plug. You don’t want to spend cruising hours pissed off because you can’t read comfortably (or whatever). But to make the best choices for different applications, we have to take the long road through the technology of lighting. Illumination and colour are the main aspects of lighting.
Illumination
Illumination is measured in lumens. The SI measurement of illumination is lux, or one lumen per square metre (about 1/10 foot-candle). AAmpere (amp), SI unit of electrical current lumen is the amount of light falling on a surface. A foot-candle is one lumen distributed over one square foot.
The illumination required for casual reading is 200-550 lumens/sq metre. The standard for office desks is 500 lumens. Some general guidelines are given in the below table. These are generally in excess of ABYC standards but you should check when you build.
| Area | Lumens/sq metre | Lumens/sq foot (rounded up) |
|---|---|---|
| Heads/Companionways | 200-500 | 19-47 |
| Berths | 550-1100 | 52-103 |
| Galley & Dinette | 108-1100 | 10-103 |
| Salon | 108-1100 | 10-103 |
| Workshop | 550-1100 | 52-103 |
| Engine Room | 1100-2100 | 103-197 |
Colour
The colour of light falling on an object affects our perception of the colour of the object (a very complex subject in itself). The colour of a light is expressed as the correlated colour temperature (CCTCorrelated colour temperature) or the Colour Rendering Index (CRIColour Rendering Index).
CCT is measured in degrees Kelvin. CRI is measured on a scale of 0-100, where a light source with 100 CRI is best at producing vibrant colour in objects. A higher CRI rating typically denotes a higher quality lamp. A CRI of 84 or better gives very little shift in an object's colour. Incandescents have an index of 95-100, and tri-phosphor fluorescent runs 84-88.
The main colour spectrum of a lamp determines how it makes us feel in an interior space. Colour spectrum is related to a lamp’s temperature. Colour temperature can be soft and comfortable for relaxing or sharp and precise for work environments. The higher the temperature, the cooler the colour of the lamp. For example, a colour temperature of 3000K is warm while 4100K is cool. Indoor lighting is typically 2700K Outdoor lighting is 6500K.
Daylight
Blue light is important during the day. Essentially we are blue-light detectors when it comes to keeping our internal clock well adjusted. This is especially important in the winter when blue-light levels might not be sharp enough to maintain our 24-hour clock.
Light of around 555 nanometres is accepted as the most efficient level of light for daytime vision. But recent research has shown that we also have biological receptors for non-visual response peaking in the blue wavelength range of 446-477 nanometres, a range abundant in clear daylight. Researchers at Brown University in 2002 discovered that non-visual ganglion cells in the eye detect sky-blue light to set our internal clock.
Daylight has an abundance of wavelengths at 446-477 and in the 555 nanometre range, satisfying both perceptual and biological demands. The challenge is to develop lighting solutions that will perform like daylight.
The choice of colour is controversial, in part because many colours we perceive are not interpolated but are ‘invented’ by the brain. The theory is that some colours enhance low-light vision provided by the cones in the eye. The eye also has rods, used for normal intensity light. Originally, it was believed that the cones, occupying a narrow slice in the centre of the retina, were red sensitive, so using red lighting would enhance night vision. But the cones are blue-green (507 nmNanometer) sensitive; although the fovea, an even more narrow slice at the centre of the cones is very red sensitive.
Night Vision
Night vision also has constraints: your night eye can't see colours or details, or directly ahead, or differentiate objects that don't move.
Because our night vision functions differently than our day vision, the objective of night lighting is to preserve night vision. Night vision deteriorates when the eye is subject to intense light. This destroys the essential chemical rhodopsin, which can take 45 minutes for 80%percent recovery. So night lights should be designed for low intensity, no matter their colour, and you should avoid looking directly at bright lights.
For night vision in the pilothouse, switch lighting between daytime white and night-time green or turquoise instead of the traditional red. Turquoise may be better for men with red/green deficiency.
Red (630 nm) is an internationally recognized attention colour traditionally favoured for its excellent ability to preserve night vision. However, red erases red lines that indicate hazards or danger on aeronautical and military maps and charts.
Today most pilots and the military have switched to other colours for night vision protection. Green is now the established colour. It is used in the 2004 Daimler-Chrysler 300C. Green is also great for retaining night vision, and it is easier on the eyes.
However, there appears to be a slow transition to blue. The military is using blue over red increasingly. Blue eliminates many colours on maps and charts, changing everything to shades of a bluish-grey. Blue is also a great reading light. It imposes less eye strain than incandescent, especially for aging eyes. However, blue affects your circadian rhythm and makes it hard to fall asleep.
Turquoise (495 nm) appears slightly brighter than blue. Turquoise is an excellent alternative to red for night vision preservation.
Current literature on night vision recommends:
- Blue-green (507 nm) for the fastest dark adaptation recovery
- Deep red (around 700 nm) at very low intensity for maximum detail
- White at low intensity if you need to see colours
Energy Efficiency
Energy efficiency is the amount of light output generated per watt of input energy consumed. This is important because it directly affects the size of our electrical system. The main choices in types of light in order of efficiency are:
- LEDs post-2007
- Fluorescent
- Halogen
- Incandescent
- LEDs pre-2007
All of these types are available in low-voltage DC. Xenon lights are also available in 24 VVolt marine types but are not considered here because of the danger when they break.
LEDLight emitting diode
LEDs have had a very high profile in the energy market for some time. But until recently they did very poorly in energy efficiency. Fluorescents were best, producing about 30-100 lumens per watt, while halogens produced 10-18, and incandescents 8-15.
Before 2007, LEDs used less than 10% of the energy of an incandescent lamp, but did not produce as much light output per watt of energy consumed. To disguise this, some vendors rated LED efficiency as the amount of light output generated per watt of total output energy instead of the input energy.
However, ongoing research has dramatically improved the efficiency of LEDs; although this is only starting to appear in production versions. LED efficiency improved dramatically in 2006. Nichia Corporation of Japan demonstrated white LED prototypes with an efficiency of 113 lumens per watt. The industry target is 100 lumens per watt, which is better than fluorescent tubes. The Nichia work was partly funded by the UK Department of Trade & Industry. (White LEDs are actually blue in wavelengths of 450 nm – 470 nm.)In addition, LEDs produce no discernible heat and are more robust than fluorescents and incandescents. They have become the lighting of choice for many marine applications.
LEDs have a long life (100,000 hours) and low heat output. They give off a soft natural light in white, red, green or blue. White or blue are used for reading, e.ggram., a reading spot lamp. Red, green or blue are used for night vision.
In a low voltage DC system, their driving system is simple and cheap compared to a fluorescent, which requires an oscillating ballast circuit. LEDs use a simple voltage-dropping resistor. They are tough and resistant to shock and vibration. They are safe near explosive gases and liquids. In a marine installation, use a dual-pin ungrounded LED. Until recently LEDs were rated in millicandela (mcd), as measured at the light source, not lumens. This made direct comparisons with other light types fuzzy. (One lumen is approximately 79.5 mcd [7].)
Now that LEDs are more competitive, manufacturers are also rating them in lumens. Prior to breakthroughs in the efficiency of LEDs, fluorescent lamps were the clear winners in energy efficiency. They last about 34,000 hours and have low heat output.
Fluorescents
Fluorescents have electrodes at both ends of a tube coated inside with phosphor. Inside the tube, a gas contains argon and mercury vapour. A stream of electrons flows through the gas from one electrode to another. This excites the mercury atoms, giving off ultraviolet photons. In turn these excite the phosphor, giving off visible light.
Invented by A.E. Becquerel of France in 1857, today’s fluorescents are available in full spectrum types with quiet electronic ballasts replacing noisy magnetic ones [5]. Cycling rates have been increased to reduce flicker. Because of the mercury, be careful not to break fluorescents, and dispose of them in an environmentally safe way. The USA Environmental Protection Agency publishes guidelines on what to do if a bulb breaks [57]. Also, don’t use fluorescents in places where you would be at risk if a tube broke. Use LEDs instead.
Cold Cathode Fluorescents
Cold cathode fluorescents (CCFCold cathode fluorescent) are similar in construction to neon tubes and have up to 25,000 hours of service life. They are readily dimmable. Look for models that are listed for marine, RVRecreational vehicle UL, CSA and CE (Europe), and meet the Ignition Proof test requirements of the United States Coast Guard, as stated in Title 33 CFR 183.410. CCFs are more efficient than other fluorescents but the tri-phosphor fluorescents have the most pleasing colour.
Compact Fluorescent
Compact fluorescent lights (CFLCompact fluorescent light) are more robust than tubes. They use only a small amount of mercury, typically less than 5 mgMilligram per bulb.
Halogen
Halogens are a type of incandescent having higher efficiency. The tungsten filament in all incandescent types is very thin, offering high resistance. When a current passes through the filament it glows, giving off light and (mostly) heat.
Halogens last between 2000-6000 hours and give off enormous heat. They are hot enough to be used in stovetops as burners. They use 20% less energy than incandescent for the same output.
Halogens are enclosed inside a small quartz lamp containing halogen gas, which increases the light output. Halogens, like most incandescents, have a very natural light. The halogen gas allows the filament to be run much hotter, giving off more light per watt. It also combines with the tungsten in the filament, giving it a longer life by re-depositing vaporized tungsten.
Incandescent
Standard incandescents are very inefficient. About 90% of the energy given off is in the form of wasted heat. They yield about 13 lumens/watt and have a life of 750-1000 hours.
Sir Joseph Swann invented them in the 1870s; although most Americans credit Thomas Edison. Watch for improved versions using deposited carbon nanotube filaments by 2009. This may not matter since many governments are banning tungsten bulbs. Australia is targeting 2010, the USA 2012-2014.
Application
Finally, we come to application, how we use these light types. The main applications are:
- Ambient
- Accent
- Task
- Utility
Ambient Lighting
Ambient lighting provides a soft general level of light in a room. Accent lighting focuses directional light on architecture, artwork or reading. Task lighting illuminates a work area like the galley or a tool bench. Usually it is directed directly on to a work surface. Utility lighting is used to flood an area with light, e.g., in the engine room.
In each type of application, you should not be aware of the lamp, in the same way you are not aware of the stud wall in a house. The purpose is to make you aware of the objects the lamp illuminates. If you must go there, ensure the lamp is designed in its own right as an object dDay’art.
For general ambient lighting throughout, ceiling mounted, dimmable, low-voltage tri-phosphor or cold-cathode fluorescents will give the best results. Select tri-phosphor or cold-cathode depending on how you feel about natural colour. Put dimmer switches everywhere except in companionways and the engine room.
Accent Lighting
For accent lighting, use small low-voltage LEDs or halogens with dimmers. Don’t use halogens in the berths, galley and dinette where close proximity makes their heat uncomfortable. Because of their very high heat output, ensure halogens are in proper enclosures and at least six inches away from objects.
Task Lighting
In the galley, put fluorescent lighting under the cupboards, hidden behind a valence, to provide task lighting on a separate switch. Don’t use a dimmer here.
In the engine room, have a separate circuit for AC fluorescents for use with shore power. Provide outlets for both DC and AC trouble lights.
In the berths, galley and dinette use low-voltage white or blue LEDs as spot or reading lights. Their cooler temperature will make enclosed spaces more comfortable. For courtesy lighting in corridors and companionways, use blue LEDs.
Utility Lighting
For utility lighting such as external spotlights, use halogen. Dual-head emergency lights, with battery backup, are available in all light types. But on balance use the newer LEDs for emergency lights. Dual-head (dual lamp) provides redundancy.
In the pilothouse, use blue-green (507 nm) or turquoise (495 nm) LEDs for night vision. Eight percent of males are red-green deficient [8], and will be groping blindly with low-level red or green night vision lights. (Women have an extra strong response to red-orange.) Even a higher percentage may have temporary alterations in perception of blue under varying conditions. Most people over 45 suffer from reduced light transmission into the eye.
