Utility rebates for energy-efficient lighting products may be drying up, but lighting-retrofit incentives still spring eternal.
Ten years after the utility-rebate peak, today's lighting-products market presents a bounty of opportunities for lighting designers and electrical contractors. Lighting-product specifiers face ever-changing pricing structures, almost-daily technological advances, and the uncertainty of utility deregulation.
In recent years, fluorescent lamp/ballast combinations have moved front-and-center in sales-and in the regulatory ring. Manufacturers now package fluorescent lamps and ballasts to emphasize an optimized system.
Spurred by cost savings, utility rebates, and demand-side-management incentives, building owners retrofit existing fluorescent lighting systems with more energy-efficient ones. Utility rebates prompted many end-users to upgrade their lighting systems. Now, despite the reduction in utility incentives and energy rebates, retrofits continue to happen. And it is no longer necessary for energy users to wait-and-see if utility deregulation will lower rates enough before doing a lighting retrofit. Many retrofits can be financed in such a way that the energy savings more than pay for the cost of the new lighting system; in some cases building owners even experience a positive cash flow.
Electrical contractors can take heart from this news because proposing viable retrofits is one way to make money. The table on page 32 shows eight fluorescent retrofit lighting projects and includes specific savings and advantages, such as the additional benefits of higher quality lighting and lower cooling and maintenance costs. Three in the group do not involve a rebate program.
The result of any retrofit project should be what is called an energy-efficient quality-lighting installation. "Quality lighting" means making use of the best light source and the best performing/most aesthetically pleasing luminaire for the task. Note that the statement does not necessarily mean the most energy-efficient light source. This will be explained later.
Tried-and-true energy savers The following products have wide applications in retrofitting commercial/institutional structures: electronic and variable-output ballasts, and T-8 fluorescent lamps and compact fluorescent lamps.
Ballasts-Perhaps the most exciting development involves the increasing variety of light output and wattage options with electronic ballasts. Ballasts used to have only a single output, but now three other output categories can be specified.
1. Low-output ballasts have a ballast factor below 0.85 (85% of rated lamp output), which allows reductions in wattage and light output in overlit spaces.
2. High-output ballasts have a ballast factor above 1.0, which allows fewer lamps to be used per fixture to achieve desired light levels.
3. Dimming and 50%/100% switching ballasts allow the output to be adjusted to meet fixed or variable output requirements.
The first two categories are available at no additional cost, but switching and dimming ballasts carry additional cost premiums.
Also, remember that a single electronic ballast can run up to four lamps, which can lower overall system costs. Three- and four-lamp ballasts are more efficient than two-lamp ballasts, and they allow fewer ballasts to be used on a project where fixtures are tandem-wired to share ballasts. Advantages of electronic ballasts compared to traditional magnetic type include lower weight, less audible noise, reduced flicker, and longer life.
Electromagnetic-type ballasts have their proper applications also. They are nearly as efficient as electronic ballasts but cost less. For example, they are selected in hospitals and other spaces containing sensitive monitoring equipment that woulld be susceptible to any high frequency electromagnetic interference (EMI) and radio frequency interference (RFI) generated by electronic ballasts. The hybrid ballast design is a core and coil ballast with electronic circuitry to disconnect the cathode heater winding after the lamp ignites, thereby saving about 6 W per two-lamp ballast during operation.
T8 lamps-The combination of T-8 fluorescent lamps and electronic ballasts is recognized as the most efficient system today. In addition, the triphosphor coating of the T-8 lamp has much better color-rendering properties than the older halophosphors used in the T-12 lamps.
Compact fluorescent lamps (CFL)-CFL light sources are an economical substitute for lower wattage incandescent lamps in applications that do not need a precise beam pattern, but where long burning hours are required, such as corridors, stairwells, lobbies, and reception areas.
Available in a range from 5 W to about 50 W in various tube configurations, the CFLs offers efficacy advantages combined with high color rendering characteristics. More recent versions of the CFLs have a four-pin base, operate on rapid-start ballasts, and are dimmable. All of these characteristics are worth noting.
In trying to achieve appropriate light levels in a renovation, consider using reflectors if the existing fixtures are to be retrofit. Reflector material selection criteria include evaluating lighting performance, environmental considerations, cleaning requirements, and appearance factors.
A retrofit case history A typical small office suite provides an opportunity to show a good retrofit lighting design. This office consists of a reception room, a conference alcove, two offices and three desks (one is a Computer Aided Design workstation) for intensive computer-based tasks.
This office's general lighting was retrofitted with 2 by 4 fluorescent troffers, each with two T8 lamps that are shielded with a deep-cell parabolic louver. A two-level electronic ballast serves the lamps. These new troffers are located exactly where the old recessed troffers (using T12 lamps) were installed.
Parabolic louvers offer effective control of disability glare while being relatively efficient. Deep-cell parabolics, with louvers 3- to 4-inches deep, generally have the best glare control and most attractive appearance, but they have a slight sacrifice in fixture efficiency. Medium-depth parabolics, with louvers about 3-inches deep, compromise between efficiency and appearance. Shallow-cell louvers (2 inches or less) are too open and don't hide the lamps well.
Parabolic louvers come in several finishes, with the standard semispecular finish the most popular. This finish minimizes hot spots on the louver while offering enough surface brightness to make the fixture appear to be lit.
One drawback of a deep-cell parabolic louver is that light output from fixtures adjacent to a wall does not fall on the upper portion of the wall, thus creating a dark strip at the ceiling line around the room. One way to eliminate this strip is to specify a perimeter cove in the office area using the same 1-inch diameter T8 lamp.
A designer who wants to affirm a more elegant solution may choose to use the new T5 lamp for this perimeter lighting application. A T5 linear fluorescent lamp fits into fixtures up to 40% smaller than T8s. The nominal 2-, 3-, 4- and 5-ft lengths (actual dimensioning is metric) are ideal in valances, coves, and wall washers. With efficacies of up to 104 lumens per watt, the lamp has a 20,000-hour-rated life and a 97% lumen maintenance. At least two ballast manufacturers offer efficient electronic ballasts in one and two lamp configurations. The compactness of the ballasts even make stagger mounting possible in tight coves, eliminating socket shadows.
By adding this installation detail, personnel in the office can select any one of four different light levels: full output recessed lighting with perimeter lighting, full recessed lighting with no perimeter lighting, half output recessed lighting with perimeter lighting, and half output recessed lighting with no perimeter lighting.
Flexibility in lumen output can bolster a small office where efficient performance of each employee is especially important.
As an example of where the most efficient light source should not be selected, let's look at the use of a 90-W PAR38 halogen lamp vs. a 20-W screw-in CFL reflector lamp for display lighting in the reception area. The flood version of the 90PAR/H/FL has a center beam candlepower (cp) of 4500 cp vs. perhaps a center beam of 800 cp for a typical 20 W CFL.
To produce the same "punch" on a display, six CFLs would be needed to match the concentrated output of a single halogen PAR lamp. The CFL has a wide-beam spread, but a concentrated light beam is what is desired in this application. A designer or specifier could also think of using either an MR16 low-voltage halogen lamp or a low-wattage metal-halide PAR lamp, both of which provide a concentrated beam.