After the commercial success of the incandescent light there were still many who were working on other forms of electrical lighting. Until 1938, when General Electric enjoyed widespread commercial success with the fluorescent light, the incandescent bulb was the standard, and the only choice for electrical lighting for both residential and commercial lighting. The initial cost of fluorescent lighting was certainly higher than incandescent lighting but the energy savings and the available light output was more than enough to offset the original investment. Unlike the LED lighting we see today, despite the potential energy and lifetime cost savings of fluorescent lighting, there were some drawbacks that accompanied fluorescent technology, yet there were advancements never before possible with previous lighting technology.
A big part of the cost of fluorescent lamps is the ballast. It’s a necessary component as it controls the amount of current available to the lamp. Without the ballast to limit the current flow, the lamp would self-destruct in short order. Some large fluorescent lights do need a voltage that exceeds 120 volts AC and the ballasts for those lights act to step-up the voltage. In the past some fluorescent lighting was operated through DC supply but there are numerous undesirable issues that occur when DC current is used. The most notable negative issues that occur with AC supplied fluorescent lighting are two things which most folks are familiar with; flickering and buzzing. The flickering occurs at twice the frequency of the supply, i.e., 60 Hz AC causes 120 flickers per second and 100 per second with 50 Hz supply. Those rates are so high that the flicker is not visible, although it is known to cause headaches and eye strain. A rare but proven phenomenon involving the flicker is in causing a strobe affect which can make a rotating object, such as a saw blade, that is spinning at just the right speed, appear to be stationary. Occasionally fluorescent lamps will produce a flicker that is equal to the mains frequency of 50 or 60 Hz. This may occur during the last number of hours in the life of the lamp and though the flicker is more noticeable than standard flicker in a correctly operating lamp, the flicker is not as noticeable when looking directly at the light but is more notable in peripheral vision.
Even though the lower cost of fluorescent lighting over the expected lifetime was much improved compared to the incandescent lighting, the use of fluorescent lamps in residential lighting was generally limited to kitchens, basements, garages, workshops and similar working areas. Although quite expensive when first introduced, the introduction of the compact fluorescent bulb (CFL), which was brought about by the energy crisis in 1973, changed all that and increased the use of fluorescent lighting in regard to residential applications. That movement to the more efficient CFL’s was not as notable as the shift to LED lighting has been but it was a major step toward lighting which was more efficient than incandescent lighting in many ways.
The CFL bulbs, like the fluorescent tubes, changed the visible aspects of artificial lighting, as incandescent bulbs could be replaced with CFL bulbs which offered some selection of color temperature. There wasn’t the selection we now see with LED lighting but one could easily find the most common, warm white (2700-3000K) and the one a bit more difficult to find was cool white (~5000K). The CFL’s, though much more efficient than the incandescent bulbs they were intended to replace, were extremely expensive and some of the configurations were larger than the standard incandescent bulb. They had distinctive shapes; mostly they were of the twisted tube variety (sort of spring-shaped) but there were some which were U-shaped. Until later developments employed smaller, more efficient twisted tubes that allowed for a standard incandescent bulb shaped enclosure, the shapes did not work well with lamp shade hasps and untold numbers of fixtures which formerly used incandescent bulbs. They could be prone to the flicker and buzzing but by this time in the florescent lighting development those issues were pretty much solved – until the light was near the end of its lifecycle.
Weather can be a concern with fluorescent lighting since all standard fluorescent lights like to operate at about room temperature and the efficiency of fluorescents decreases as temperatures increase or decrease. In freezing weather, standard fluorescent lights might not even operate. There are special fluorescent lamps which are designed to operate in cold weather. Unless specifically engineered and designed for such, fluorescent lights are not dimmable as it is difficult to maintain the arc at lower voltage levels. A further drawback to fluorescent lights is in the disposal. All fluorescents contain mercury and phosphor and, although the quantities are pretty minute, the amounts definitely create an environmental issue that is not a problem with incandescent lights.
Fluorescent lighting allowed, for the first time, different color temperatures of light. Standard designations for color are, generally, WW for warm white (equating to approximately 3000K), EW for enhanced white (approximately 4000K), CW for cool white (approximately 5000K) and DW for daylight (approximately 6000K). There are other non-standard fluorescent lighting colors for such things as plant grow lights and blacklights. Blacklights are not only used for fun stuff but for deadly stuff (for bugs) in bug zappers, and in detecting traces of materials and substances which are invisible in regular light. Another specialty type of fluorescent light is used in tanning setups. The fluorescent light technology also produces germicidal lights. These lights contain no phosphor so, technically, the are just a gas-discharge light and not truly fluorescent, but without the technology that produces fluorescent lamps, these germicidal lamps would not exist in the form they do. UV light emitted by these type of light kills germs, will cause eye and skin damage, ionize oxygen to create ozone, and can be used to identify certain minerals by the color of their fluorescence. There are also special fluorescent lamps which are made for film and video use. They create a softer light than the traditional halogen light sources and are much cooler, in regard to operating temperature, as well. The film lights have specially designed ballasts which negate the potential video flickering and also have special color temperature ratings which approximate natural daylight.
Other gas-discharge lighting was also developed, although, unlike the fluorescent tubes and later CFL’s, these gas discharge lights, such as mercury vapor lamps, low pressure sodium, and xenon arc lamps are excellent for lighting large areas, such as parking lots, gymnasiums, stadiums, warehouses, streets and other large area lighting applications. Neon lighting is also a gas-discharge light and is used for things such as small as indicator lights and huge signs.
This blog is a multi-part writing which will touch on the evolution of artificial lighting and will be continued in the upcoming weeks. In the meantime, if you need help with your LED lighting projects, please feel free to call Polar Ray at 303-494-5773 and speak with a lighting consultant.