FIGURE 4.4 Sample LED replacement lamp for incandescent parabolic aluminized reflector lamps. Courtesy of OSRAM SYLVANIA and Paul Kevin Picone/PIC Corp.
FIGURE 4.5 Sample LED replacement lamp for linear T8 fluorescent lamp. Courtesy of Pacific Northwest National Laboratory.
The luminous efficacy of LED replacement products has improved over the past several years and is expected to continue, as illustrated in Figure 3.1 of Chapter 3. Figure 4.6 illustrates examples of performance data for replacement LED-integral lamps (A-lamp, PAR lamp, and linear lamps), reported in 2011. The efficacy values of these replacement lamps are in the range of 40 to 110 lumens per watt (lm/W). Several LED replacement A-19 and PAR lamps are showing very promising results in terms of efficacy.
A few LED replacements for 4-foot linear fluorescent tubes have performance similar to traditional fluorescent lamps, but for many of them the total light output is substantially lower, and the spatial distribution of light is far more concentrated than that of the conventional fluorescent lamps. The narrow spatial distribution and relatively low luminous flux mean that closer spacing of luminaires would be required to achieve the same lighting environment as produced by conventional fluorescent lamps.
There are many challenges for making reliable replacement A-19 lamp replacements. An LED replacement lamp for an incandescent A-lamp requires squeezing all the needed components, LEDs, driver, heat sink, etc., into a light-bulb sized package as shown in Figure 4.3. Heat dissipation is very challenging and could affect the reliability of the LED lamp. At the present time, in early 2012, it is difficult to make long-life, reliable, LED replacements for incandescent A-19 lamps greater than 75 W because of thermal management challenges. There are some high-power PAR replacement lamps that use active cooling in which a fan is employed to move air and remove heat by convection. However, active cooling usually is not desirable in lighting products because of additional failure modes and audible noise issues. Realizing these limitations, an industry group, Zhaga Consortium,3 is developing a standard for a better socket for replacement lamps with better heat dissipation characteristics, among other attributes. Even though the new socket may help lamps and luminaires in the future, it will not help replacement lamps for existing luminaires. Many of the LED A-19 replacement lamps currently in the market (early 2012) cannot be considered as true replacement for the following reasons:
• LED replacement lamps have a larger geometric shape than the incandescent lamp they are meant to replace and may not fit into a luminaire that was designed for incandescent A-19 lamp.
• The spatial beam distribution of the LED replacement lamps is not similar to that of the lamps they are designed to replace. For example, in a common table lamp, LED replacement lamps often will cast light in a more upward direction, leaving the tabletop surface below relatively dark.
• Although a wide variety of LED replacement lamp products are commercially available, their initial purchase price is much higher than that of competing lamp technologies. However, the “Lighting Facts” labels that appear on lamp packages provide consumers an estimate of annual operating costs, which allows rough calculation of payback times.
Retrofit luminaires are SSL products that fit into the spaces occupied by existing luminaires but require complete removal of the existing luminaire for installation. Common types of retrofit luminaires are those for recessed housings, 2Œ × 2Œ or 2Œ × 4Œ recessed troffers, high-bay luminaires, track
3 “Zhaga is a consortium, a cooperation between companies from the international lighting industry. The cooperation is governed by a consortium agreement that defines rules regarding confidentiality, intellectual property, and decision making. Zhaga enables interchangeability of LED light sources made by different manufacturers. This simplifies LED applications for general lighting” (Zhaga Consortium, 2012).