High bay lights are designed for illuminating large interior spaces where the roof truss or ceiling height is greater than 6.1 m (20 ft) above the floor or work plane. The "bay" originally refers to an interior subspace which is formed by a skeletal framework designed for some types of industrial facilities. Yet, in the lighting industry, this term has expanded to include almost any interior space that has a large area to be lit. High bay facilities are generally designed for industrial production, warehousing and storage, indoor sports, big box retail, exhibition and convention. Hard-to-reach ceilings, expansive spaces, harsh operating conditions, and long running hours. These challenges place high demands on the robustness and efficiency of high bay luminaires.
High bay lighting applications are very diverse. Virtually all commercial, industrial, public, sports and recreational facilities with a high clearance between the floor and the ceiling require high bay lighting to provide adequate illuminance.
Lighting can significantly affect productivity and safety in manufacturing facilities. Types of work performed in these areas vary tremendously from production to machining but all need a lighted environment that allows various tasks to be completed at the desired speed with accuracy and safety. Manufacturing facilities represent the largest section of indoor or covered real estate in the industrial sector. A considerable number of these facilities are designed with a high ceiling clearance to accommodate the production requirement. Such production facilities include, but is not limited to, foundries, steel mills, casting and welding facilities, automotive production lines, aircraft assembly lines, machine factories, sheltered shipyards, and all workshops equipped with overhead cranes. In these industrial buildings, powerful illumination is only one of the challenges. Lighting equipment must be made tough enough to resist extreme temperatures, high humidity conditions, corrosive atmosphere, vibration from large machinery, and dirty power.
Warehouses and storage areas
Warehouse and storage facilities are found in many commercial, industrial, retail, and logistics environments. These facilities are designed to provide a proper environment for storing goods and materials as well as fulfilling highly diverse tasks such as logistics, inspection, packaging, shipping and receiving, light assembly, and desk work. Depending on the business service requirements and the products to be stored/handled, warehouses and storage facilities can be divided into different types, including open storage, high rise, fixed racking, mobile racking, cold storage, controlled humidity (CH), and special-designed facilities. Loading docks, which are covered shipping and receiving docks for trucks and vans, are also usually a part of warehouses, logistics centers and distribution facilities. Being utilitarian facilities, warehouses require sufficient illumination to facilitate the movement of goods at a high volume and/or high frequency. The never-ending pursuit of low occupancy costs per square foot results in a proliferation of warehouses with increased heights. Warehousing facilities tend to be taller than they were thirty years ago and ceiling heights in these facilities range from a minimum of 24 feet to as high as 80 feet. Aside from providing adequate illuminance for safety and navigation, warehouse lighting is more challenged to provide uniform illuminance on the vertical surfaces of stored goods from top to bottom and along the entire length of storage aisles as the majority of critical visual tasks occur in a vertical plane.
Sports and recreational facilities
While large arenas are usually mounted with floodlighting luminaires high around the court perimeter, indoor sports venues intended for Class III and IV play are provided with high bay lighting because of confined spatial conditions. Minimum mounting heights should be less than 6.7 meters (22 feet) for Class III and IV facilities. Gymnasiums, which are generally implemented as part of an educational facility, are illuminated by high hay lights. These indoor facilities play host to different sports and non-sporting activities, high bay lighting should meet the varied or particular requirements for each event. Other sports and recreational facilities with general illumination provided by overhead high bay fixtures include indoor basketball courts, hockey rinks, ice skating rinks, horseback riding arenas, indoor ski resorts, and indoor amusement parks, etc. The challenge in gymnasiums and indoor sports courts lies in achieving uniform, visually comfortable illumination with minimal fixture installations.
Convention centers and exhibit halls
These buildings feature virtually column-free, high bay, and long span spaces that require illumination from high lumen lighting systems. Lighting should be designed to provide a substantially uniform level of illuminance across the vast amount of interior floor spaces. As aesthetics are usually one of the basic design elements in modern convention centers and exhibition facilities, it is important for the architectural form of high bay luminaires to blend nicely with the surrounding architecture. High bay lighting should also be able to provide good color rendition of color-critical exhibits.
Big-box stores and shopping malls
Also known as a supercenter, superstore or megastore, a big-box store is a physically large, warehouse styled retail establishment with minimal architectural detailing. They're typically windowless, non-partitioned spaces in which the primary task plane is the vertical surface of the racks. It's especially important to provide adequate illuminance towards the bottom of the racks. High CRI light should be provided whenever possible.
Airport and rail terminals are facilities where passengers embark and disembark. Passenger terminals are usually designed as high bay structures and rely on direct illumination from high bay luminaires to conduct all tasks within the designated areas.
Airport hangars are located on airport grounds and serve as repair and maintenance facilities. These buildings have a scale similar to heavy industrial facilities as they need to be large enough to accommodate an airplane. The ceiling heights of airport hangars can reach as high as 100 feet. This challenges the luminaires' ability to deliver adequate task illuminance from a long distance.
Some high bay lights are specifically designed and certified for locations made hazardous by the presence of flammable vapors or gases, combustible dusts, or easily ignitable flying or fibers as defined by the NEC and IEC. These classified areas are typically found in paint manufacturing plants, pulp and paper mills, ammunition facilities, power generation plants, oil refineries, chemical plants, gas processing plants, grain processing and storage terminals.
Low bay areas
Sounds strange? In fact the application boundary between high bay and low bay luminaires is ambiguous. Lighting manufacturers usually offer high bay luminaires in a range of wattages, including those designed for low bay facilities such as grocery stores, mechanic shops and multi-storey industrial buildings. High bay and low bay luminaires are generally designed and constructed in the same way, except that the lumen package and optical design of low bay luminaires are tailored for low mounting heights. The light distribution pattern of low bay lights is optimized for a spacing-to-mounting ratio greater than 1.5. Low bay lights may also come with tighter glare control when a higher level of visual comfort is necessary.
Hose down areas
High bay lights can be constructed with hose-down capability for applications where luminaires are subject to routine high-pressure washdown with water and/or sanitation chemicals. This type of luminaires is typically found in food-processing facilities, cleanrooms, car washes, livestock or poultry buildings, and commercial kitchens.
The unique physical characteristics and operating conditions of industrial, commercial and sports facilities distinguish high bay lights from other types of indoor luminaires. Many issues enter into design and specification decisions for high bay lighting.
Energy efficiency is especially a priority in high bay applications due to the sheer number of luminaires required to cover the expansive space and relatively high wattages typically involved to deliver adequate illuminance from a high mounting height. With energy costs on the rise, an inefficient facility is at a competitive disadvantage when lighting becomes a drain on resources and fails to comply with ever-changing energy codes.
A tremendous opportunity remains to maximize energy savings by operating high bay lights with lighting controls. The ability of a light source to interact with lighting controls and energy management systems has gained increasing attention. The light source must have instant start/restrike and dimming capabilities so that its light output can be controlled in a very dynamic way in step with digital or analog control signals. As the industrial internet of things (IIoT) is ushering in a new era of lighting automation, controllability should be prioritized as one of the key capabilities of a lighting system.
The photometric performance of a luminaire is often overlooked by end users. However it can significantly impact the quality of illumination and the practical value of a luminaire. Photometric performance can be defined as the efficiency and effectiveness with which a luminaire delivers light to an intended target. High light source efficacies should not be equated with high luminaire efficacies. Legacy technologies can offer a relatively high source efficacy of up to 120 lm/W. However, the omnidirectional emission pattern of HID lamps will result in an optical loss as high as 30% when the light source is integrated into a lighting system.
It is worth noting that a high optical efficiency doesn't necessarily translate into effective use of the light collected by the optical system. The optical design for HID luminaires, for example, causes a concentrated distribution of illuminance directly below the luminaire and a much low density of low illuminance around high intensity "hot spot". Non-uniform distribution of illuminance may distort visual perception of moving objects, which can be a hazard factor or affect task performance. Poor uniformity commands continuous eye adaptation between two significantly different luminance levels physically adjacent to each other when multiple luminaires are installed to illuminate an area. The need to perform high frequency visual adaptation between different vision states can cause eye fatigue. Maintaining uniformity between adjacent areas of luminaires with a high uniformity ratio may be wasteful of energy and increase cost because a higher fixture density is required to compensate for the poor uniformity.
The importance of longevity should run parallel with energy efficiency and photometric performance as the maintenance and relamping costs associated with high bay lighting are very high. The reliability of a luminaire will be determined by all its constitutive parts and their survivability under environmental and operational stresses. A long lifespan light source is critical to the long service life of a lighting system. Yet the design and engineering of the platform where the light source runs on should be paid extra attention to. High bay lights for industrial applications need to operate reliably in hostile environments where there can be presence of extreme temperatures, moisture, vibration, impact, dust, dirt and corrosive elements.
Conventional high bay systems employ metal halide, linear fluorescent, compact fluorescent (CFL), or induction fluorescent lamps as the light source. What make these technologies obsolete are their low luminous efficacy, use of hazardous mercury, and limited lifespans (with the exception of induction lamps). Among these light sources, metal halide had been favored in high bay applications for its ability to operate at a high wattage of up to 1,000 watts and a comparatively high source efficacy. While lower wattage metal halide bulbs may last as long as 20,000 hours, higher power bulbs typically have a life expectancy drastically reduced to several thousand hours. Another concern is long startup and hot restrike times. In particular the long restrike interval can be a serious issue for facilities that require uninterrupted lighting. Poor startup and restrike performance, along with the restrictive dimming capability, makes metal halide lamps outmoded in the era of digital lighting. While envelope failure (bulb explosion) is not common, it is of major safety concern since the hot quartz from a broken bulb may ignite flammable gases or vapors, combustible dust, ignitable fibers or flying that can be present in industrial environments. As previously noted, metal halide high bay lights have a frustrating illuminance uniformity since HID bulbs are high-intensity nearpoint sources. This is a serious application disadvantage when it comes to indoor lighting. On the other hand, fluorescent systems produce diffuse lighting that delivers a better uniformity. However they're limited to mid-bay and low bay installations due to their low system lumen output.
Solid State Lighting
A light emitting diode (LED) is a semiconductor device that generates light through the recombination of electronic carriers (electrons and holes). This operating principle differentiates LEDs from traditional light source and lends LED high bay systems many advantages over traditional lighting solutions: high power conversion efficiency, excellent controllability, high photometric performance, spectral versatility, long lifespan, solid state durability, and compact size.
The industrial sector has been the most steadfast advocate of energy efficient lighting, which is the most breathtaking part of LED lighting technology. LEDs provide more than twice the luminous efficacy (lumens per watt) of metal halide lights. The energy efficiency advantage of LED lighting is exhibited not only in its high efficiency energy conversion from electrical power to optical power, but also in its superior photometric performance and ability to be seamlessly integrated into various lighting control strategies. The direct nature of LEDs results in highly controllable optical systems. The miniature packages are typically assembled in arrays to form a large light emitting surface (LES), which allows extremely uniform illuminance and tight control of light when the LEDs are mated with tailor-made secondary optics. High illuminance uniformity and precise lumen delivery translate to maximal utilization of light emitted by the light source and contribute to comfortable visibility. Maximized luminaire spacing as a result of high uniformity illumination produces an economical installation. The energy efficiency potential is not fully exploited until lighting controls are used to operate the LED luminaires. Up to 50% of energy consumption can be saved when lighting is automated based on time-based triggers, threshold-based events or a combination of the two.
The economics of lighting is determined by luminous efficacy, optical efficiency, power consumption, first cost, and service life. LED technology provides a viable solution to addressing the first three variables, but leaves the industry struggling in the painful trade-off between the first cost and service life. Although the rated service life of LEDs is projected to be from 50,000 to as much as 200,000 hours, this doesn't imply that LED luminaires will logically last that long. LEDs are current driven, self-heating light sources. Their intercorrelated electrical and thermal characteristics add complexity to system design. In order for the LEDs to perform optimally over their rated life, tight load regulation and effective thermal management are two critical specifications that should be prioritized in the design and engineering of LED luminaires. As a result, the use of high capacity heat sinking devices and high performance driver circuitry considerably drive up the cost of high wattage LED lighting systems.
An economical high bay lighting system is one which, when the first cost, operating cost, maintenance cost, lifespan, and system performance are all considered, provides the greatest practical benefits for the least total cost. Despite the high product cost, high efficiency operation over the long lifespan of a properly engineered LED luminaires creates a return on investment (ROI) that is significantly higher than legacy systems. Unfortunately, not all people interpret "economical" this way. It's very common that quality is overlooked and the primary criterion for product selection is low price. Consequently, the market is flooded with cheap and crappy products of which the reliability, light quality, efficiency, and even safety are oftentimes compromised. Typically, these products use non-EMC plastic LED packages, bare-bones driver circuits based on linear power regulation or simple switching regulation, and inadequately engineered thermal management systems.
Types of High Bay LED lights
High bay LED lights are designed in various forms to serve different application scenarios or to deliver specific features. There're primarily three types of designs: round, linear and modular.
Round high bay lights have evolved from traditional style luminaires, which feature a cylindrical heat sink, a top-mount electrical box and a large aluminum reflector, to low profile luminaires in a sleek, aesthetically pleasing style. This type of luminaires are commonly known as UFO high bay lights simply because their shape looks like a disc. UFO high bay lights were by no means designed just to achieve a sleek architectural look. It's the board-style design of LED module that makes the low profile heat sink design a necessity. The disc-shaped heat sink provides an increased surface area for accommodating an LED module with a large LES that facilitates more uniform distribution of light. Maximized thermal distribution area allows the waste heat generated from the LED array to spread quickly across the heat sink. The heat sink, which simultaneously functions as the luminaire housing, is constructed of die cast or cold-forged aluminum. The LED module is an assembly of LEDs which are mounted on a metal core printed circuit board (MCPCB). A lens array is indexed to the circuit board to regulate luminous flux from LEDs when a controlled beam spread is desired. The ability to control light emitted by LEDs with miniature compound lenses allows high bay luminaires to eliminate the bulky aluminum reflector. The LED driver is located in a separate aluminum enclosure or a thermally independent compartment.
Linear high bay LED lights consist of two categories: traditional style LED luminaires that follow the footprint of traditional two-to-eight lamp T5/T8 fluorescent fixtures, and highly integrated linear LED fixtures with a heavy duty housing and more rugged construction. Traditional style linear LED high bays come with a housing constructed from extruded aluminum or die-formed, cold-rolled steel. The light assembly consists of a number of lumen maintenance trays which mount linear LED strip modules and direct light at the desired beam angle to accommodate facility needs. Integrated linear LED fixtures are in most cases designed for racked/aisle environments, although high bay open area applications are also well served by this type of fixtures. These fixtures have an extruded aluminum housing that provides mechanical strength and heat sinking. The linear light assembly is comprised of one of more LED modules, depending on the fixture length. The LED module has an array of LEDs mounted on a rectangular circuit board. Light produced by the LEDs is regulated by a one-piece lens array. The LED drivers of linear high bay lights are mounted to a gear compartment which is integrally constructed with the housing but is thermally isolated from the light assembly.
Modular high bay LED lights provide scalability in light output, versatility in light distribution, continuity and flexibility in lighting design. These fixtures are assemblies of modular LED engines and externally mounted drivers. A modular LED engine is a self-contained LED system that is thermally managed, environmentally protected and optically regulated. However, the power supply is not built into the system, instead it's powered by drivers located in a backmount gear box. The housing/ heat sink is made of either die cast aluminum or extruded aluminum. The LED assembly is constructed the same way as that of UFO or integrated linear high bay luminaires.