INFORM (Strategies for a better environment)

INFORM (Strategies for a better environment) has a great article on High Bay Lighting systems. The original post can be found here:


What are the benefits of high-output T5s and induction fluorescents?

Switching from HID lamps to HO T5 fluorescent lamps is now a common strategy for increasing energy efficiency in warehouses and other high-bay lighting situations. Both HO T5s and induction fluorescents:

Are capable of instant-on and instant re-strike.
Can be used with energy-saving occupancy sensors
Can be adjusted through dimming (with a dimmable ballast).
Have lower average mercury content than metal halide HID lamps.

Do high-output T5 and induction fluorescents perform as well as metal halide HID lamps in high-bay applications?

Yes. Several attributes are used to compare lamp performance:

Rated life is the average amount of time a lamp will function before failing.
The color rendering index (CRI) indicates how accurately a light source renders colors. A CRI of 100 is equivalent to sunlight. Lower CRIs indicate poorer color rendering.

A lumen is a measure of light flow. The higher the lumens, the more light is produced by the lamps in the fixture.

The lumen maintenance is a function of the rated life, showing the percentage of original lumens present after a certain percentage of the rated life has passed. Lumens decrease over the life of most lamps, so a lamp that maintains its lumen output for a longer period is more desirable.

The color temperature describes the appearance of the light in terms of the red and blue tones. Light that we perceive as redder or warmer has a lower color temperature, light that we perceive as bluer has a higher color temperature. While the color temperature of fluorescent and induction fluorescent lamps is stable over the life of the lamp, metal halide lamps tend to shift color over their lifetime.

Are both high-output T5 linear fluorescent and induction fluorescent lamps appropriate for all high-bay applications?

No. Fluorescent induction systems are the best choice for very cold conditions because they retain their efficiency at extremes of temperature. Because of their exceedingly long life, they also make sense in applications where it is difficult or costly to change a spent lamp. T5s, however, are more energy-efficient at moderate temperatures (25°C to 35°C) than induction lamps, so for locations that do not experience temperature extremes and where labor costs to change a spent lamp are not significant, HO T5s may be preferable.

Which high-bay lighting systems are more energy-efficient?

When calculating energy efficiency, it is important to consider the number of lamps contained in equivalent systems, as well as the number of watts per lamp. For instance, in the example in the table below, four HO T5 lamps or two induction fluorescent lamps are required to produce approximately the same amount of light as one metal halide HID lamp. The higher the lumens per watt, the less electricity is needed to produce equivalent light. The fewer the kilowatt-hours per year used by a lighting system, the less electricity a facility uses and pays for.

Which lamps are less expensive to purchase and run?

Comparative purchase prices can vary widely depending on volume purchased and location. Based on a small survey, metal halide systems are less expensive to purchase than either of the fluorescent systems, costing approximately 25 percent less ($150) than an equivalent four-lamp T5 system ($200). An equivalent two-lamp induction system costs about four times an equivalent T5 system ($800). 6

"Payback time" is the period that elapses before an initial investment is recouped, in this case through savings in electricity, lamp replacement, and maintenance/disposal costs. Payback time varies based on the size of the lighting project, the electricity rate, the particular fixtures selected, and other variables. The Los Angeles Department of Water and Power has a payback calculator at http://www.ladwp.com/energyadvisor/PA_46.html where you can input your variables.

A variety of case studies have reported payback times of 1.8 to 29.9 years for HO T5 high-bay replacement projects. 7 One case study reported a five- to eight-year payback period for an induction fluorescent high-bay relighting project. 8

Recommendations

Facility owners, managers, and architects specifying high-bay lighting applications should choose the most energy-efficient system with the lowest mercury content appropriate for their construction and remodeling projects.

Retrofit projects should be analyzed carefully for payback and benefits such as improved color rendering.

Before purchasing a lighting system, buyers should consult a lighting professional who can analyze the entire project for energy efficiency, lighting level, and appropriate color rendering. Tell your chosen professional that your organization would like to specify low-mercury alternatives wherever possible.

Facilities should recycle all mercury-containing products, including all HID lamps, T5s, and induction fluorescents.

For more information:


For more information:
T5 Fluorescent High-Bay Lighting Systems -- http://www.smud.org/education/cat/cat_pdf/T5.pdf
Induction Lighting Systems -- http://www.smud.org/education/cat/cat_pdf/Induction%20Lighting.pdf
Induction Lamps Installations at Kowloon Bay Indoor Games Hall -- http://www.emsd.gov.hk/emsd/e_download/pee/Induction%20lamps%20at%20kbigh.pdf
Lighting: HID Versus Fluorescent for High-Bay Lighting -- http://www.ladwp.com/energyadvisor/PA_46.html