Types of lighting
There are a number of types of lighting such as:
- Incandescent (includes halogen)
- Gas Discharge (includes metal halide, fluorescent, others)
- High Intensity Discharge (HID)/metal halide (MH)
- Light-emitting diode (LED)
They vary in efficiency, operating hours, light quality, etc. We will briefly discuss each one in the following section.
Incandescent lighting (includes halogen)
Thomas Edison invented the incandescent light bulb nearly 120 years ago, and it still works pretty much as it did then. Inside a glass bulb (as shown below), electricity heats up a wire filament made of tungsten, causing it to glow and give off light. Of course, electrical heaters work in much the same way, and that's why about 95 percent of the energy produced by standard incandescent lights is heat, not light. As a result, standard incandescent bulbs are inefficient light sources that are only 5% efficient. The heat they produce can drive up your electricity bill in hot weather if your home or office is air-conditioned. While standard incandescent bulbs last usually between 750 to 1,000 hours before burning out, some long-life bulbs last up to 2,500 hours by using thicker filament. The trade off is that long-life bulbs are less energy efficient and produce less light per watt. One more thing, incandescent bulbs are excellent at rending color, CRI of incandescent is about 100.
There are two common types of incandescent lightbulbs:
- Standard incandescent lightbulbs - are the least efficient light source. New efficiency standards for lighting have resulted in phase-out of this traditional incandescent lightbulb by January 1, 2014.
- Energy-saving incandescent (or halogen) lightbulbs - A halogen lightbulb is a type of incandescent lightbulb with a capsule that holds a special halogen gas (such as iodine or bromine) mixed with inert gas around the heated filament to increase the efficacy of the incandescence (see diagram below). They are more energy efficient than standard incandescent bulbs but somewhat more costly. Halogen lightbulbs may also have a special inner coating that reflects heat back into the capsule to further improve efficacy by "recycling" the otherwise wasted heat. Together, the filling and coating recycle heat to keep the filament hot with less electricity
Halogens give off a crisp, very bright, white light, CRI is 98-100. They maintain their light output over time without fading with age, as incandescent do. The small size of halogen lamps permits their use in compact optical systems for projectors and illumination.Halogens are a little more expensive than standard incandescent lightbulbs, but are less expensive to operate because of their higher efficacy and longer life expectancy (1000 to 3000 hours). They are commonly used in reflector lamps such as indoor and outdoor flood or spot lighting, indoor recessed and track fixtures, and floor and desk lamps. All halogen bulbs are dimmable, but at the cost of a shorter life. Below are some common types of halogen lightbulbs.
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