LED lighting—compare and consider for your farm
Published in Dairy Star August 11, 2012
Proper lighting is important for optimum cow performance and providing a safe and pleasant work environment. Cows and heifers need adequate light levels and hours of light to generate appropriate hormonal responses stimulated by daily daylight and dark cycles for optimal growth, milk production and movement as they walk between feed mangers, waterers, freestalls and the milking center. Managers, veterinarians and workers need sufficient light for observing cows, doing cow care tasks and assessing cow cleanliness before milking. Uniform lighting that minimizes shadows and dark entrances will minimize cows stopping or slowing down to investigate as they enter dark areas.
Important light characteristics when designing lighting systems and selecting lamps and luminaries include: light intensity or illumination level, which is measured in terms of foot-candles; color rendition index, which describe a light's ability to render the true color of an object; energy efficiency, which is described as luminaire efficacy in terms of lumens per kilowatt of electricity; uniformity, useful life and initial cost. When talking about lighting, “lamps” refer to bulbs; “luminaries” refer to complete fixtures including lamps, electronics and housing.
New light emitting diode (LED) luminaries are available and being used by dairy producers to provide light in milking centers and freestall barns. LED lighting technologies and products are rapidly changing and evolving. One potential problem during rapid change is variable product quality, performance and energy efficacy. High quality LED products meet or exceed the performance of fluorescent and metal halide luminaries but poor quality LED products will have poor performance.
When comparing lighting energy efficiency, it is important to be clear on what is included. Lamp or bulb efficiency is different than luminaire efficacy. Luminaire efficacy includes all the energy used by the entire light fixture, bulb, ballast and other electronics required. New standard testing procedures (LM-79 and LM-80) were developed by the Illuminating Engineering Society of North America (IESNA) to measure the performance characteristics of LED luminaries. LM-79 describes procedures for testing electrical and photometric performance solid state lighting products. LM-80 describes procedures for measuring the amount of light outputted over time. LED energy efficiency is called luminaire efficacy and gives the lumens outputted per watt of electrical energy used (lm/W). So when considering LED luminaries and comparing them to other lighting options (ex., fluorescent, metal halide or high pressure sodium), make sure that you are comparing luminaire efficacies.
The U.S. Department of Energy has also created the LED Lighting Facts® program to manage consumer and decision maker expectations of LED lighting products and prevent exaggerated performance claims. Lighting products with the LED Lighting Facts® label were tested according to industry specifications and the results are accurately presented in the lighting facts label. For more information about LED Lighting Facts®, visit the program website at www.lightingfacts.com.
The Lighting Facts website has a product list of LED luminaries with the LED Lighting Facts® label. Unfortunately lamps commonly used by dairy producers are not listed. Only 35 high-bay and low-bay LED luminaries were listed when this was written and only a few were designed for use in wet and dusty environments. Of the products listed, luminaire efficacy ranged from 53 to 103 lm/W and averaged 84 lm/W. The color rendition index values ranged from 65 to 85 and averaged 71 on a 0 to 100 scale. LED lamp lifetimes are not listed but a review of specification sheets of several LED luminaries indicates that lifetimes are around 60,000 to 70,000 hours.
Good quality LED luminaries are very energy efficient, have long useful lives, operate well in cold temperatures and are essentially instant-on devices. They are also easily integrated with electronic controls like timers, dimmers and occupancy sensors.
The main disadvantage of LED luminaries is the initial costs of the devices. They commonly cost 2 to 3 times more than comparable fluorescent or metal halide lamps. However, with long useful lives (60,000 hours or more) that reduce replacement lamp cost and labor costs to replace lamps, and the higher efficacy, good quality LED luminaries can be more economical over the life of the LEDs.
Dairy barns and milking centers are damp and dusty so lights installed should be watertight and constructed of corrosion resistant materials. Lamps with polycarbonate lenses and an ingress protection rating of IP-65 rating will be dust proof and able to withstand water jets. Lights installed and wiring used should meet National Electric Code (NEC) requirements and applicable state electrical codes.
Work with reputable suppliers and make sure that energy and cost comparisons are done on a luminaire basis if LED products are being considered. When comparing LED luminaries not listed in the LED Lighting Facts® program, ask for and compare their LM-79 reports and compare warranties to make sure that you are getting high quality LED luminaries.
Table 1. Representative performance characteristics for lighting technologies
|Product||Luminous Efficacy (lm/W)||Light Output (lm)||Watts (W)||Color Rendition Index (0 to 100)||Useful Life (hours)|
|LED Tube wet location||77||3,042||40||80||60,000|
|High Watt HID (Lamp & ballast)||111||37,800||341||90||20,000|
|Low Watt HID (Lamp & ballast)||97||7,300||75||90||12,000|