The cost for SSL luminaires needs to be reduced for them to be readily accepted. As noted in Chapter 2, it took a combination of technical advances to improve quality and incentive programs to overcome the initial reluctance to adopt CFLs, and their initial cost is still an inhibiting factor.
Both initial and replacement costs are major considerations, particularly for SSL luminaires. Many SSL components are integral with the luminaire, making component replacement difficult if not impossible. Instead of replacing a lamp, the entire luminaire would need to be replaced should one of these integral components fail. Progressive manufacturers now construct luminaires for easy component replacement, including such features as removable optical cartridges and quick connects to drivers. Also, driver lives are dependent on operating temperature but, nonetheless, are increasing to match the life of the SSL luminaire (Figure 5.3).
While cost is still a significant barrier to more rapid introduction of SSLs, the expectation is that with the current rate of progress, they will become a cost-effective option in the near future (Bland, 2011).
Lighting controls can include dimming, occupancy controls, and color control. Current SSLs do not always gracefully mesh with existing installations. One great challenge for designers is selecting compatible drivers for the SSL luminaires. This is also related to dimming compatibility issues. Different drivers have unique operating currents and operational characteristics. If a driver is not compatible, luminaires can flicker, have shorter lives, or not operate at all. Most quality manufacturers now supply the drivers with their luminaires, which avoids confusion.
Drivers must also be compatible with new and existing control systems. Currently, some integrated drivers have power quality problems such as high THD of the line current and low PF. A designer must obtain the list of compatible drivers from the control manufacturer—a method of selection that is awkward, adds design time, and adds difficulty when SSL equipment is substituted for standard fixtures. A NEMA standard for controls, drivers, and SSL compatibility could streamline this process.
Heat management is a huge challenge with SSL applications (see Chapter 4). Luminaires must dissipate heat adequately to maintain life and light output expectations. For SSLs, mounting details can add heat management complexity. For instance, operating temperatures can rise if SSL luminaires are mounted in a confined space, adjacent to insulation, in high temperature environments, or where the heat otherwise cannot be dissipated. An example would be a recessed downlight adjacent to insulation in a nonconditioned area. Another example would be one in which MR16 lamps are installed in open air luminaires where the only heat sink is the socket connection. As operating temperatures increase, life and light output decrease. Non-LED luminaires have an easier chance of dissipating heat compared to LED lamps, where the heat sink is limited to the socket size and cooling fins around the lamp. OLED luminaires do not have as significant heat management issues as LED (refer to Chapter 3) at room temperatures and below, which facilitates installations in more varied environments.
FIGURE 5.3 LED driver life of Philips “Xitanium” driver versus case temperature. SOURCE: Philips Lighting North America (2012).