The common choices for lighting include the following:
HID including metal halide and sodium vapor versions
Each of these types of lighting has found uses in many areas. However, the landscape is changing due to increasing awareness of environmental and cost issues. Increasing energy costs and global climate concerns have led the U.S. to mandate the phasing out of incandescent lighting in the near future. All of the other types of lighting with the exception of LED’s and halogens contain significant amounts of mercury and present potential health and environmental problems and will almost certainly eventually present legal issues as well. The recent linking of heavy metals, especially mercury, to the onset of both autism and Alzheimer’s disease is sure to eventually lead to numerous class action lawsuits by some enterprising law firms out to make some huge fees. A brief review of each type of lighting is presented below.
The history of the incandescent light bulb is long and glorious leading back to its invention by Thomas Edison. The bulb was the invention that allowed the glowing filament that produced light when an electric current was run through it to last. Without the bulb, the filament quickly broke and the light went out. By surrounding the filament with a vacuum contained in the bulb, the life of the light went up ultimately to about 900 hours of use. The constant failure of the filament necessitated designing lighting fixtures with removable bulbs, since the fixture was much more expensive than the bulb which was disposable and easily replaced. This legacy of designing disposable light sources separate from the fixture has continued today and is required for every light source technology but the LED.
Incandescent lighting has provided cheap bulbs with little negative environmental impact other than the high energy use associated with their operation. With the current emphasis on reducing energy use and our carbon footprint, incandescent lighting has fallen out of favor. Their high energy usage makes them the least efficient of the above mentioned energy sources, and the most costly to operate.
The fluorescent tube was a more energy efficient lighting invention dating back over 70 years. The fluorescent bulb contains mercury vapor which is excited to a plasma state by a charge of electricity emitted by the ballast. Once excited the ballast supplies the correct current to the fluorescent tube and light is emitted. As in incandescent design, the bulb would wear out before the fixture, and was designed to be removable. In the case of the fluorescent light, the ballast also wears out before the fixture and is also designed to be removable.
Fluorescent lighting is often left on intentionally by businesses to extend the life of the bulbs. Each bulb is only good for about 1000 on/off cycles. The labor cost of bulb and ballast replacement are often so great and disruptive that you will see entire office buildings with their lights on all night.
There are 3 types of ballasts, magnetic (cheap) and electronic (expensive) and induction. Fluorescents with magnetic ballasts are not dimmable and have an annoying hum and flicker often present. The newer and much more expensive electronic ballasts are dimmable by up to 30 % and reduce hum and flicker. The induction fluorescent ballast is the most expensive and uses a strong magnetic field ballast to ignite the fluorescent light. This extends the life and increases the efficiency of the bulb.
A major drawback of all fluorescent light is that they produce a large amount of harmful UV radiation. They also have poorly designed bulb contacts leading to common breakage of bulbs on installation and removal. This leads to mercury contamination and exposure which is almost never reported or properly cleaned up.
Another major drawback of fluorescent lighting is that all of the bulbs contain significant amounts of mercury (manufacturers usually say trace amounts of mercury). Almost all of this mercury ends up in landfills and enters the environment.
Compact Fluorescent (CFL)
The drive for energy efficiency and elimination of incandescent lighting as an option has led to the emergence of the CFL. The CFL is a direct screw in replacement for an incandescent light bulb. Fixtures do not need to be replaced to convert from incandescent to CFL. This has led to their widespread use. They are more energy efficient than incandescent bulbs, but are not dimmable and contain mercury just as the normal fluorescent bulbs. The electronic ballast is at the base of the light bulb, but can produce hum and flicker just like a normal fluorescent light. CFL’s also produces harmful UV radiation just like a fluorescent light.
The halogen lamp is basically an incandescent lamp on steroids. Its performance is better than incandescent and it emits a higher color temperature light than incandescent making it better for some focused high light applications. It has been used extensively for headlights in the automotive industry and in outdoor landscaping applications. It uses no mercury, so is better environmentally than many other light sources, but its efficiency while better than incandescent is poor.
Sodium vapor lights are primarily used as outdoor lights. They are easily identified by their yellowish color. They are very energy efficient for this application and are rated very well on a lumens per watt basis. However, the human eye does not see the sodium vapor light spectrum very well. When you drive under a sodium vapor street light, you can’t see very much at all. This is a great example of the consumer needing to know the difference between lumens and vision.
HID High Energy Discharge Lamps
High energy discharge lamps are very efficient light emitters as compared to incandescent lighting. Unfortunately they deteriorate rapidly in the first 100 hours of use to as little as 50 percent of initial output. The consumer therefore gets only half of the promised energy saving after100 hours. They continue to dim during the life of the product until they fail after 1-2 years depending on the use and location. Because the installation of new lights generally highlights the light loss of the other older still burning lights, and because of the high cost of bulb replacement of these lights (usually outdoors on elevated poles), it is common practice to replace all bulbs, even the ones still burning on a regular basis. This makes bulb replacement costs much more expensive than at first glance. This should be considered on all new HID installations.
HID lights also contain mercury and are a potential health issue indoors because of normal bulb breakage issues, and they are a disposal issue as are all lights containing mercury.
A major drawback of HID lighting is that they require an approximate 15 minute start up in warm weather. A longer warm up is required in cold weather and in very cold temperatures they may not start up at all.
HID lights are on/off control only. They are not dimmable, and are not able to interface fully with intelligent lighting controls on anything other than an on/off mode. There are many situations where dimming or additional on/off cycles would save a lot of energy. HID’s do not work well in these locations.
LED lighting has been around for over 20 years. The first LED lighting uses were for small indicator lights. This evolved over the years as individual LED’s became more powerful and reliable. They began to be used in more and more applications where individual LED’s would be grouped on PC boards to produce higher lumen products. Early LED lighting efforts were all dominated by bulb type products in applications requiring low lumen outputs.
Eventually, individual LED’s became more powerful, producing up to __lumens per LED. These were assembled on PC boards as well and began to tackle higher lumen applications. Many companies were formed to produce and sell this type of product and continue to sell these early versions of LED lighting today. They focus on the small specialty low lumen LED applications.
Since the introduction of the high lumen LED array in 2008, commercially viable high lumen output LED lighting has become a reality. Individual LED arrays are now available producing up to 15,000 lumens per array, over 20 times the light emitted by a 60 watt incandescent light bulb.
The use of phosphors allows the production of broad spectrum light at 2700 to 5000 degree Kelvin. Color temperature has been shown to be critical in lighting design. The human eye evolved exposed to sunlight (5000K), moonlight (4000K), and firelight (2700K).
Exposure to each of these color temperatures at different times of the day effects the human circadian rhythm which has been shown to effect everything from sleep habits, weight gain, mood, and mental disorders. Humans now spend a lot of time indoors in artificial light during the day. This needs to be 4-5K light. This same light in the evening would disrupt our sleeping habits.
For evening situations we need light at or below the 3K range. It is very important to keep these human factors in mind when designing lighting systems and to specify the appropriate color temperature in indoor environments.
The promise of LED lighting of energy efficient, long life, broad spectrum, environmentally friendly, economical, healthy light has been fulfilled. Constructing any new building with any other light source is a missed opportunity based only on a lack of accurate information.