Few changes in your home will make as much difference as a change in lighting. With all the types of lightbulbs available, you may wonder what differentiates them. Variations in bulb technology affect spectral distribution, bulb life expectancy, and energy efficiency, the latter being of increasing importance these days. Each type of bulb has its advantages.
A fluorescent bulb produces light when electricity arcs between electrodes at both ends of a glass tube that is filled with low-pressure mercury vapor and other gases. Electrons flowing between the electrodes collide with vaporized mercury atoms, causing the mercury to release ultraviolet energy. A phosphor coating inside the tube absorbs the UV energy, causing the coating to emit visible light. Once known for casting a harsh glow, fluorescent technology now provides excellent color rendition; light emitted by a “warm white” fluorescent bulb is virtually indistinguishable from light from an incandescent bulb.
Because of the mercury in these bulbs, they should not be put in the regular trash and should be disposed of properly (visit sfenvironment.com for a list of recycling sites).
COMPACT FLUORESCENT LAMP (CFL)
Among the commonly available bulb types, compact fluorescent bulbs provide the most economical and energy-efficient lighting, using about one-fourth the power to produce the same amount of light as incandescents. CFLs last approximately 10,000 hours, so over the life of a single bulb, you will realize a savings compared to the cost of incandescent bulbs.
It’s important to remember that CFLs contain a very small amount of mercury and therefore, like fluorescent bulbs, must be recycled and not thrown in the regular trash.
Basic incandescent light technology is essentially the same as Thomas Edison’s Victorian era invention: Electricity passes through a tungsten filament inside a sealed glass bulb. The tungsten resists the electrical current, causing the filament to heat up and glow. Over time, the filament gets thinner until it breaks. However, because incandescent lighting is the most inefficient of the common lighting choices, federal legislation now mandates increased efficiency standards for these bulbs, and these traditional bulbs will eventually be phased out.
The 100-watt incandescent bulb was the first to be affected by the new law. The same amount of light produced by a 100-watt bulb, which is 1,500 to 1,700 lumens, must now be generated using 72 watts or less.
Full-spectrum lighting is actually a color-corrected variation on incandescent technology. Full-spectrum lightbulbs often use neodymium glass to filter out significant portions of the yellow spectrum common to standard incandescent bulbs. The resulting spectral distribution is much closer to what you see when you walk outside on a clear day — the closest replication of natural sunlight available. Colors show up accurately, and the contrast between black and white is increased. Research suggests that full-spectrum lighting provides improved visual acuity (sharpness), decreased glare and eyestrain, reduced fatigue, improved neural functioning, reduced seasonal depression, reduced hyperactivity, reduced stress, greater attentiveness, and improved mood.
The halogen lighting design is another variation on incandescent technology that is somewhat more energy-efficient. The sealed bulb contains a tightly coiled tungsten filament surrounded by halogen gas. During use, halogen combines with evaporating tungsten, redepositing tungsten on the filament, thus slowing down the rate at which the filament breaks down. Light output levels over the life of the bulb do not diminish as noticeably as with standard incandescent bulbs. The light produced by halogen bulbs is whiter than standard incandescent, making colors appear brighter and more intense. Halogen bulbs are commonly used in the home environment for track lighting, accents, torchiere lamps, and recessed lighting.
LIGHT-EMITTING DIODE (LED)
These appear to be bulbs, but light-emitting diodes are actually tiny semiconductors. When power is applied, the movement of electrons stimulates them and creates photons, or light, that is visible to the human eye. Because LEDs do not use filaments like incandescent bulbs, they emit much less heat and are more efficient in consumption and output.
Unlike incandescent lights, LEDs are built inside solid protective cases, making them extremely durable. LED lights are commonplace in everyday applications and are used in traffic signal lights, as status indicators on electronic equipment, in exit signs, and in emergency vehicle lights.
Solar lights use a solar panel that converts sunlight into electricity. During the day, the electricity converted by the solar panel is stored in a rechargeable battery. At night, the battery powers the light using the stored electricity. Operating times depend on geographical location, season, and weather. For best results, fixtures should be placed in direct sunlight. Solar lighting is popular for lighting outdoor areas including walkways.