LED High-Bay Lighting

An article I wrote for tED Magazine. Reprinted with permission.

In the construction of some facilities, a skeletal framework is used, which forms an interior subspace called a bay. The Illuminating Engineering Society categorizes these bay spaces as either high-bay (>25 ft. off the floor) or low-bay (<25 ft.). Some manufacturers define high-bay as being any luminaire mounting >15-20 ft.

These high-ceiling interior spaces are common in factories, warehouses, big box retail stores, gymnasiums and all-purpose rooms. Traditionally, they were lighted using metal halide lamps—compact, rugged sources offering high white light packages.

In the race to efficiency, pulse-start metal halide began to supplant probe-start, with energy regulations limiting availability of pulse-start luminaires in the new construction market. Fluorescent offered an even more efficient alternative, prompting excellent retrofit opportunities yielding energy cost savings as high as 50 percent. Now LED has achieved performance levels making them a major contender for this application.

“Energy management and maintenance costs continue to be a primary focus in high-bay lighting,” says Steve Johnson, Marketing Manager, Eaton. “These spaces require luminaires to deliver higher lumens, which can drive to increased energy and maintenance costs. A complete controls-based solution designed around LED with improved optical performance can significantly reduce these costs.”

Scott Roos, Vice President, Product Design, Juno Lighting Group, says LED high-bay luminaires have captured significant market share. Estimates are about half the market by dollar volume and 20 percent in terms of units in 2015. He adds that the current demand is on a trajectory of 25 percent growth per year.

“At that rate, it won’t be long before LED captures dominant market share both in terms of unit and dollar sales,” Roos says. “One-for-one retrofits are driving most of the market, and this will likely continue for the foreseeable future.”

Besides luminaires, another option is screw-in LED retrofit lamps that can replace HID lamps in existing luminaires. A recent Navigant Research report forecasts that global sales of LED high-bay luminaires and lamps will peak at almost $17 billion in 2017 and then decline to $15.9 billion in 2021.

LED offers several distinct advantages compared to both metal halide and fluorescent. Compared to metal halide, LED offers higher lumen maintenance, longer life and greater flexibility and ease with automatic controls. Based on mean lumens, luminaire efficacy can be more than double compared to probe-start luminaires and 40 percent higher than the most-efficient pulse-start luminaires.

This translates to energy savings as high as 70 percent against probe-start and 30-40 percent against pulse-start metal halide. These savings can be accelerated via installation with automatic lighting controls.

Compared with fluorescent, LED offers higher efficiency while being even friendlier with lighting controls. Luminaire efficacies can be up to 30 percent higher than the fluorescent competition, translating to energy savings ranging from 20 to 30 percent with a high-performing LED luminaire. Meanwhile, frequent switching imposed by occupancy sensors does not impose the same cost in service life for LED as it does with fluorescent. Dimming capability is often available out of the box as a standard driver feature.

Additionally, service life may be more than doubled, though extended-life linear fluorescents are available that provide comparable life to LED high-bay luminaires, albeit with frequent spot relamping as the installation ages. Another consideration is the life of the driver, which may fail before the LEDs reach their service life projection. Serviceable luminaires available that allow relatively simple driver replacement; replacement typically requires ensuring only an approved device is installed, and that it will be available.

A final advantage is advanced optical design available with LED luminaires, which can provide greater directionality and more precise beam control and uniformity. In new construction, for example, LED luminaires can be spaced farther apart, which can reduce the number of luminaires required to produce desired light levels.

“In both new and retrofit markets, the adoption of LED high bays will accelerate over the next few years as initial cost drops and efficacy improves,” says Marin Werr, Director, New Product Innovation, Hubbell Lighting. “But don’t think fluorescent is down for the count. While the growth curve for fluorescent appears to have reached a plateau, its low initial cost, the emergence of extended-life lamps, controllability and reasonable efficacy assure it will have a respectable market position for some time to come.”

Further to Werr’s point, this is still a get-what-you-pay-for period in LED technology. Good performance requires good engineering of the luminaire’s optical and thermal characteristics. Low cost may mean reduced performance, which requires distributors to ensure they qualify products and do so across all relevant criteria. This decisionmaking process starts with the application and may not always lead to LED.

“If electrical distributors have the opportunity to offer their customer one or the other, there are many considerations—especially what is important to the end-user,” says Kristin Fedoruk, Director, Energy Sales and Solutions, Juno Lighting Group. “Is it service life? Efficiency? Lumen output? Color? CRI?”

Lack of standardization is another growing pain in LED technology, requiring diligence and product selection based on the understanding the light source is often the luminaire, and the form factor and performance of that particular luminaire may be unique to that particular manufacturer.

For now, Werr says, there is significant diversity in form factors, with no standardization in sight yet. “LED high bays are round and square, big and small, lensed and open, aluminum and steel, using high-power and mid-power LEDs, heavy duty or light duty, wet location or classified,” he says. “This trend toward a surfeit of choices could continue for years until LED high bay finds its groove.”

Roos says there are three main types of LED high-bay luminaire designs:

• High-efficiency luminaires with TIR optics attached to each LED that precisely and efficiently distribute lumen output. While the most efficient, this type of luminaire may be overkill for one-for-one retrofit projects with fixed luminaire locations, as advanced optical performance cannot be fully leveraged.
• Rectangular LED luminaires that imitate the general design of linear fluorescent high-bays. These luminaires typically incorporate arrays of low-power LEDs to generate 30+ greater efficacy than their fluorescent counterparts, but with no advanced optical control to improve distribution and uniformity.
• Round LED luminaires that imitate traditional HID dome luminaires while providing greater efficacy. These luminaires often incorporate single or multiple high-wattage chip-on-board arrays, which may be used with a secondary glass optic. These rounded luminaires are more damage resistant when fitted with a wire guard, making them well suited to gymnasiums and similar applications. They also provide a traditional industrial luminaire aesthetic.

When selecting an LED high-bay luminaire, look for the basics and ensure the manufacturer can back up any claims related to efficiency and life. Other questions to ask include, how well designed is the luminaire for the application, particularly ambient temperatures? Will chemicals in the environment interact with the LEDs? Be sure to match the product to the application and its operating characteristics.

Roos concludes: “LED technology is already delivering superior results, and the technology will continue to improve and become more affordable. It is highly unlikely that we will go backwards, so it is wise to get on board and learn the new technology.”