Highly regarded for their maintenance-free, energy-efficient operation, and environmental friendliness in a wide range of industrial applications, light-emitting diode (LED) lighting solutions are quickly becoming a sought-after alternative to high-intensity discharge (HID) and fluorescent lighting in cold storage applications. By their very nature of operational form and function, LEDs effectively overcome virtually all of the most vexing challenges surrounding cold storage lighting for both refrigeration and deep-freeze environments to provide an ultralong-life lighting solution with an ROI payback period of as little as two years.

The LED Advantage

A UK-based March Foods warehouse lit by high-pressure sodium (HPS) lighting on the left, and by Dialight Durosite LED High Bays on the right.
As a solid-state device, LEDs are, by design, more rugged and durable than HIDs and fluorescents to withstand even the harshest environments. With no filaments to fail, bulbs to change, or ballasts to burn out, the leading industrial LED lighting systems offer up to a decade of worry-free performance. This exceptionally long life virtually eliminates the trouble and cost of routine maintenance and the inherent disruption in workflow inside cold storage lockers. Plus, it ensures a safer working environment; there is no doubt that almost every facility has a few burned-out bulbs at any given time that can significantly reduce visibility. LEDs eliminate this safety risk with reliable operation for years.

Compared to traditional fittings, LEDs also deliver a substantial energy savings by virtue of their drastically reduced electricity consumption. For example, the Dialight 150-W LED High Bay operates at less than half the wattage of the typical 400-W HID unit it’s designed to replace, for a significant drop in energy use and cost. This not only saves money — to the tune of hundreds of thousands of dollars in some instances — but also plays well into corporate sustainability and environmental goals. And, because there are no bulbs to dispose of, nor any hazardous materials within to deal with, LEDs are much more environmentally friendly in this regard as well.

Cold Storage Bonus

Aside from the overall energy savings and related environmental advantages, the unique technology at work in LED fixtures makes these innovative fittings particularly well-suited to cold storage applications with a number of distinct advantages over typical conventional lighting.

LEDs offer superior performance in cold temperatures. In fact, unlike traditional fittings, LEDs actually deliver up to 20 percent more light output in cold temperatures. Where typical HID, fluorescent, or incandescent fixtures have issues with turning on, discoloration, or are completely non-operative, the cooler ambient temperature actually allows the LEDs to operate more efficiently.

No Warm-Up

Dialight’s Durosite High Bays installed in MedSafe’s Houston, TX warehouse.
LEDs start up instantly at full light output the moment they are switched on, eliminating the time-consuming warm-up period for most conventional fittings that is often exacerbated by cold temperatures. This instant-on capability not only improves safety and operational efficiency by restoring illumination in the wake of a power outage, for example, but it also means the lights can be turned off when not needed (many facilities leave conventional lights on 24/7 to eliminate the warm-up waiting period). For even greater ease-of-use and efficiency, LEDs can be equipped with motion/occupancy sensors to activate the lights only when needed for significant additional energy savings. And, unlike conventional fittings, the performance lifetime of most LED fittings is unaffected by frequent switching on and off.

Less Heat Output

From a heat emissions standpoint, LED fixtures produce a fraction of the heat emitted by conventional fittings, which dramatically reduces the strain on cooling systems, improving energy efficiency in this area as well. The most efficient LED fixtures feature advanced heatsink technology for builtin thermal management, rather than just relying on the ambient temperature in the cold locker to keep the fixture cool. This reduction in heat output lowers the risk of condensation buildup that can cause dangerous icicle formations. These are a significant problem with conventional fixtures, pose a safety threat to workers, and must be removed regularly. LEDs mitigate the risk and removal by eliminating the formation from the start.

Improved Air Circulation

The most innovative LED systems also offer a much smaller profile than traditional lighting fixtures, and as a result can improve airflow and temperature consistency. For example, Dialight LED High Bays are the smallest on the market with a form factor less than one-third the height of most conventional fittings, which eliminates turbulence and pockets of warm air. The low-profile design of today’s LED-based fixtures also allows the fittings to be mounted closer to the ceiling (using existing wiring) for even less interference with air flow.

With energy savings of up to 75 percent, and a potential ROI payback period of less than two years, LED lighting solutions alone offer powerful cost-saving incentives to make the switch to LEDs, particularly in areas where energy costs are already high. In addition, government agencies and utility providers in all 50 states now offer energy-saving rebate programs for industrial facilities that make the switch to LEDs to reduce energy consumption and greenhouse gas emissions. Factor in the extended life — up to ten years maintenance-free in some cases — and LED solutions offer a clear advantage over traditional lighting solutions in cold storage applications.

Not All LEDs Are Alike

While it’s clear that LEDs in general offer significant advantages over conventional lighting in cold storage applications, not all LED products are created equal. Distinct differences in the design of the three most critical components — optical control, thermal management, and electrical design — can mean the difference between a successful fixture and a failure.

When comparing products to fit any application — cold storage or otherwise — consider these factors:

Optical control: The best LED-based fixtures not only maximize the usable light and do so with a minimum number of fixtures, but they also offer directionally controlled lighting to strategically place the light where it is needed most and deliver the most benefit from each kWh consumed. In cold storage applications, optical control means eliminating the light wasted on the walls and the tops of racks when it’s really the workplane that needs to be illuminated.

While some manufacturers place bare LEDs directly onto a printed circuit board, the best optical designs are found in LED systems that combine a reflector-based system or total internal reflection (TIR) optics with strategically placed and angled LEDs to achieve the most uniform light appearance and ensure that the advertised lumens per watt are actually delivered where they’re needed.

Thermal management: While this is obviously a major concern in cold storage, heat management is one of the most critical factors in successful overall LED lighting design, as it directly impacts both efficiency and lifetime of the fixture. Improper thermal design will dramatically shorten the life of the fitting, essentially erasing the longevity benefits promised by LED technology. The most advanced LED fixtures not only successfully dissipate heat from the LEDs themselves through the heatsink, but also manage heat loss from the driver and minimize conducted heat reaching the driver.

Look for LED fixture manufacturers that can provide In-Situ Temperature Measurement Tests (ISTMT) from an accredited third-party lab. These tests reveal the junction temperature of the hottest LED on the fixture, which can be compared to the LED chip manufacturer’s LM-80 data to suggest how long the LEDs can last.

In addition to proper thermal design, LED fixture manufacturers offer a thermal overload protection feature will ensure that should the fixture get too hot, the unit will automatically reduce its output to compensate, dimming its own light before shutting down in an orderly fashion to prevent failure of the fixture.

Electrical design: Energy efficiency is one of the key areas where LEDs outshine conventional lighting in virtually any application. But, this benefit is highly dependent on the power efficiency of the fixture itself — the power supply must deliver enough current to generate the advertised lumens, but not so much as to overpower the system. Fixtures that make use of off-the-shelf power supplies are restricted to the pre-configured drive current — typically 350 or 700 milliamps. With no control over the components of an electrical system, many manufacturers overdrive the LEDs, causing them to burn brighter at first, but ultimately compromising fixture life. This results in less uniform light output over time and unplanned maintenance when the fixtures fail before their stated lifetime.

To overcome this obstacle, integrated, purpose-built power supplies allow the manufacturer to adjust the drive current to balance optimum light output with fixture life and deliver a more uniform light output over a longer span.

Manufacturers that successfully balance these three disciplines through a holistic systems approach to LED lighting fixture design can deliver far more advanced and predictable solutions.

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Lighting Technology Magazine

This article first appeared in the January, 2012 issue of Lighting Technology Magazine.

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