High-Bay Lighting

High-bay lighting—defined as indoor lighting in spaces with ceilings higher than 25 feet—is used in a variety of applications, including big-box stores, school gymnasiums, sports venues, warehouses, and manufacturing facilities. High-intensity discharge (HID) and fluorescent lighting still dominate the high-bay market, but light-emitting diodes (LEDs) are making inroads. LEDs can be cost-effective because long operating hours lead to higher energy and maintenance savings, and high-bay environments often provide opportunities to control light levels based on occupancy and daylight harvesting—which LEDs can do very well. Although earlier LED products didn’t provide enough light for most high-bay applications, some of the latest products can replace up to 1,000-watt metal halide (MH) luminaires.

What are the options?
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As with many lighting options, the lamp type you choose and the addition of controls can help save energy dollars.

Lamps

In a facility that’s lit with old probe-start MH lamps, installing newer, pulse-start lamps can gain you savings, but fluorescent lamps or LEDs can raise the savings even higher.

HID lamps (high-pressure sodium and metal halide) were the mainstays of high-bay lighting for many years, but in about 2000, advances in the performance and color quality of fluorescent lighting made high-intensity fluorescent (HIF) lamps the most efficient, cost-effective choice in many cases. Compared to HID lighting, fluorescent lighting (predominantly T5 high output and high-performance T8 lamps) offers many pluses, including higher efficiency, longer life, lower lumen depreciation rates, better dimming options, faster start-up and restrike times, better color rendition, and less glare, but they are also more sensitive to temperature variations. On the HID side, higher-wattage ceramic metal halide (CMH) lamps and compatible higher-wattage electronic ballasts have made CMH a competitive choice in some applications.

Induction lamps, a type of fluorescent lamp that uses radio-frequency energy rather than an electric arc to excite phosphors and produce light, are also a viable option. Induction lights offer very long life but are less efficient than LEDs and high-performance fluorescents. In addition, lamp-life ratings for LEDs and some fluorescents are approaching those of induction lamps.

Despite their higher initial costs, LEDs are starting to make inroads into high-bay applications. Compared to fluorescents, LEDs offer comparable or higher efficacy (and the technology is still rapidly improving), longer life, similar color quality, more controllability, and more flexibility with light-distribution patterns. The most promising early applications for LEDs were in cold storage because LEDs perform better in cold conditions than other lamp types. Since then, LED products have become more efficient, and with less heat to dissipate and better techniques for handling the heat that LEDs do create, high-bay applications have expanded to more general warehousing applications.

Controls

A large high-bay site might have the lights on across the whole facility, even if only a small portion is occupied at any given time. In these cases, the ability to turn lights on when they’re needed and off when they’re not can have a substantial impact on consumption. Occupancy sensors and timers can capture these savings, but they need to be combined with lighting systems that are effective when controlled. HID light sources have long start-up and restrike times and so can’t be shut off based on occupancy, but they can be dimmed to about 50 percent of initial power. Fluorescent lighting is a better choice for controllability due to its faster startup time, but frequent on-off switching can reduce its life span. LEDs are the most amenable to control—they react instantly and suffer no degradation of life with frequent switching—but they are more costly.

For some facilities, skylights and daylighting controls—which modulate electric light levels based on available daylight—can also be big energy-savers. In addition, lighting control systems can automatically turn lights on and off based on a preset schedule, rather than relying on personnel to remember to turn lights off.

How to make the best choice
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LEDs have the potential for the highest efficiency and lowest life-cycle costs of the high-bay lighting alternatives (Table 1). But LED performance varies widely among products and light sources must be evaluated for each application.

Table 1: Comparing high-bay light sources
Light-emitting diode (LED) luminaires are still more expensive than conventional luminaires, but savings in energy use and maintenance can more than make up the difference in life-cycle savings. However, because LED cost and performance vary widely, be sure to evaluate the technology with the correct data for your specific application.

Consider these attributes when evaluating LEDs for high-bay use:

  • LEDs offer longer life than HIDs and most fluorescent products, plus similar color quality, more controllability, and the potential for better light-distribution patterns. So, for example, you can waste less light illuminating the tops of storage racks and provide more-even light distribution. That capability means that you can meet required light levels with fewer total lumens.
  • LEDs do well with on/off occupancy sensors because their life is not shortened by frequent cycling as it is for fluorescent lamps. And unlike HID lighting, LEDs don’t have a long warmup or restrike time.
  • Generally, LEDs do well with dimming—it can often improve LED efficiency and increase lamp life. Fluorescent lamps lose efficiency when dimmed, and MH lights are subject to significant color shifting when dimmed below about 50 percent of full output. Some LED products may also suffer from color shifting when dimmed.
  • Many high-bay LED fixtures feature a horizontal top surface that’s susceptible to dirt accumulation, which can reduce the fixture’s ability to keep the lamps cool. Fixtures with vertical fins are less prone to clogging from dirt accumulation.
  • Because LED performance improves in colder conditions, the most promising early high-bay installations of LEDs were in cold-storage facilities. Since then, LED products have become more efficient, and high-bay installations have expanded to more general warehousing applications—but be sure to compare a fixture’s rated temperature to the expected ambient conditions.
  • LEDs emit little infrared or ultraviolet radiation, so materials like food or fabrics may have a longer shelf life. Additionally, LEDs contain no mercury, which is a plus in a food-handling environment and could reduce end-of-life disposal costs.

For a list of LED high-bay products that have been certified to meet certain minimum requirements, see the DesignLights Consortium’s (DLC’s) Qualified Products List (QPL). To be on the list, a product must meet requirements that cover a number of criteria, including efficacy; lumen maintenance, which determines lamp life; minimum light output; minimum fixture warranty; light distribution; color rendering index (CRI); and color temperature (see the DLC’s Technical Requirements Table for the specifics in each application type that the list covers). The requirements are generally set to equal or exceed the performance of the best of the incumbent fluorescent or HID products.

What’s on the horizon?
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LED lighting will continue to improve in performance and decrease in cost and should become cost-effective in a growing range of applications. For example, one study found that prices for LED high-bay fixtures fell 30 to 50 percent from 2012 to 2013. A growing number of products also incorporate wireless networked sensors and controls that help to reduce energy use and perform proactive maintenance.

Who are the manufacturers?
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Numerous manufacturers offer high-bay fixtures for a variety of light sources. Here are just a few:

Neither this list nor any mention of a specific vendor or product constitutes an endorsement or recommendation by E Source, nor does any content in the Business Energy Advisor constitute an endorsement or recommendation, explicit or otherwise, of your service provider’s various technology-related programs.
Content last reviewed: 
05/13/2014
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