LED lighting reduces energy consumption, extends equipment life, and significantly reduces maintenance requirements

By: Henry Yu Littelfuse Senior Technical Marketing Engineer

Light Emitting Diode (LED) technology is rapidly revolutionizing the electrical lighting industry due to its relatively high efficacy (higher lumens per watt), secondary optics (better lenses/reflectors), and greater heat dissipation compared to traditional incandescent lamps. Rapid advances in LED lighting technology and associated cost reductions have made LEDs a viable lighting solution for an increasing number of applications. Today’s LED lamps are more energy efficient than traditional incandescent lamps; since less energy is wasted as heat, they are 6 to 7 times more efficient than incandescent lamps, typically reducing energy consumption by more than 80%. Higher reliability and longer life are other important advantages offered by LED lamps. However, to meet expectations for higher reliability and longer life, these lamps must be properly protected from electrical hazards. If properly protected from overvoltage and other interference, LED lamps can last up to 25 times longer than traditional bulbs. LEDs
are used in a wide variety of applications due to their unique characteristics, including small size, ease of maintenance, resistance to breakage, and the ability to focus light in a single direction. LED lamps are widely used in road lighting, garage lighting, wall washers, traffic lighting, flood lighting, digital signage, tunnel lighting and street lighting.

About one-third of the energy savings achieved with LED lighting are the result of longer lifespans of LED fixtures. Reducing maintenance costs is critical to ensuring the long-term cost-effectiveness of LED fixtures.

Outdoor lighting that is not properly protected can fail at any time, even before it pays for itself through lower electricity bills. Given that government agencies and property owners pay up to 2 to 4 times the price of traditional lighting when replacing LED fixtures, they need to recoup their investment, which is impossible if LED lighting fixtures are damaged by power line voltage transients during their specified service life. Once LED lighting fails, it must be repaired by a contractor or the streetlight owner. Maintaining LED outdoor lighting is more expensive than the initial installation, so the longer the product lasts, the greater the chance of recovering the initial investment through energy savings.

To protect outdoor LED lighting from failure during their payback period of approximately five to seven years, they must have high durability and reliability. Transient surge events on the AC power lines, which can damage lighting fixtures, are a significant threat to outdoor LED lighting fixtures. No lighting fixture, conventional or otherwise, is free from problems. The causes of some of these problems, such as weather or line voltage spikes and fluctuations, are largely beyond the control of the installation owner or product manufacturer.

GATEWAY PROGRAM

The U.S. Department of Energy (DOE) GATEWAY Program has generated a number of important observations and results from the lighting evaluation projects it conducts. The program provides support for the evaluation and demonstration of high-performance solid-state lighting (SSL) products to obtain empirical data and experience with the field application of this advanced lighting technology. The DOE's GATEWAY program focuses on providing lighting users and professionals with an independent third-party source of data for use decisions; this data should be considered in conjunction with other information related to the specific site and application under trial. Each GATEWAY evaluation compares the SSL product to existing technologies used in the field. Depending on the available information and circumstances, SSL products may also be compared to other lighting technologies. Although products used in the GATEWAY program may have been pre-screened for performance, DOE does not endorse any commercial products or in any way guarantee that users will achieve the same results using these products.

DOE Study on LED Lifespan - Experiment on I-35 Bridge

The I-35W Bridge in Minneapolis remains one of the oldest outdoor LED installations in continuous operation in the U.S. DOE released a report on the long-term performance of the LED lighting system installed on this bridge in September 2008. The report is a welcome addition to the LED lighting literature, which would benefit from additional data on long-term field performance.

A recent DOE study on LED brightness degradation over time predicted a 30% lumen degradation over the life of an LED device. During the six-year test period, two of the 20 LED drivers tested failed. Outdoor LED lighting is subject to a variety of environmental overstresses, including wide temperature fluctuations, pollution and corrosion, rain and moisture, sunlight/UV radiation, wind and vibration, and power fluctuations. Transient voltages in power lines pose a significant threat to fixture reliability. Even without definitive evidence of LED driver failures in the field, the DOE report suggests that at least some LED driver failures are caused by inadequate surge protection.

As more field experience is gained, and the causes and effects of various other factors become better documented, the site-specific specification process must be adjusted accordingly. The suitability of luminaires to meet local conditions is one example. The luminaires on the I-35W Bridge were installed before specifiers had the benefit of knowledge gained through years of outdoor LED field experience. This meant that the installations may have experienced some otherwise preventable problems, such as measured reductions in luminaire power and optical output, or even the two LED drivers that left a record of failures. Without knowing the cause of these problems, it is impossible to say, for example, whether higher levels of surge protection could have been used to face local voltage transients and avoid such failures. Over time, more detailed specifications have emerged that not only meet the needs of specific sites, but also reduce or even eliminate the thorny issues that adversely affect lighting performance.

in conclusion

LED luminaires represent the early state of LED lighting technology, but they continue to demonstrate relatively reliable operation compared to traditional lighting fixtures. With approximately 20,000 hours of cumulative operation to date, if the lighting designer had chosen the traditional lighting route, the bridge would have required at least one complete luminaire replacement by now, as well as additional early failures, as is typical with any common bulb technology. The DOE's six-year testing and study of LED streetlights on the Minneapolis I-35W Bridge from 2008 to 2015 demonstrated that the use of LED luminaires consistently provides a higher return on investment. Higher levels of surge protection can further minimize LED driver power failures and enhance reliability. All outdoor LED lighting fixtures manufactured after 2015 must meet American National Standards Institute (ANSI) standards to obtain the maximum service life of LED luminaires.

About the Author

Henry Yu joined Littelfuse in 2011 and is currently a Senior Technical Marketing Engineer in the Electronics Business Unit. He is responsible for business development in target market segments, including LED lighting and cloud computing. He holds BSME and MSME degrees from National Taiwan University. He worked as a safety engineer at Underwriters Laboratories for five years. He can be reached at hyu@littelfuse.com.


Sidebar: Surge Protection Modules for Outdoor LED Lighting

Littelfuse's LSP thermally protected varistor modules are designed for outdoor and commercial LED lighting applications. Their built-in thermal disconnect feature provides additional protection against catastrophic failure and fire hazards even in extreme cases of MOV end-of-life or sustained overvoltage conditions. The LSP05 and LSP10 modules are replaceable devices. The series version has a special indication feature that turns the lighting off when the thermal disconnect feature is activated.