Energy Efficient Dairy Lighting
Table of Contents
Lighting plays a large role in dairy production performance. It is possible to reduce energy costs by making small changes to the lighting on your dairy operation. A well designed, energy efficient lighting system can mean higher lighting levels, better livestock performance and lower energy costs.
This Factsheet offers suggestions on how to change your lighting system to reduce energy costs by 15%-75%. It highlights different lighting systems such as incandescent, fluorescent, compact fluorescent, fluorescent tube lighting, high intensity discharge and Light Emitting Diode (LED). An example of the cost to change from an incandescent to a fluorescent light system is also included.
To know how to reduce energy costs it is important to understand the terms used to measure light.
When considering ways to reduce energy costs think about how to get the most light output per lamp size (lm/W). Typical lumen outputs are shown in Table 1 and Figure 1 along with other light system information.
Note: CRI means colour-rendering index. Fluorescent T12 (1.2 m or 4 ft) has not been included as they are not recommended. This is because: 1) they are not as energy efficient as T8 or T5; and 2) complete fixtures and replacement components will be unavailable over the next few years.
Figure 1. Lumens/watt of typical lights sources found on farms.
With today's relatively high light-level requirements in barns and with lights on for longer periods, the old Edison style incandescent lamps are only about 5% efficient at converting energy to light. The rest is wasted as heat energy. Incandescent lights also attract flies and other insects, and are quickly coated with dirt that further reduces the amount of light available. Figure 2 shows examples of incandescent lights and the dirt problem. Incandescent lights also have a relatively short-rated life compared to other lighting types (see Table 1). For example, a 100 W, 1,000 hr (standard rated lamp) could be expected to last 63 days at 16 hr/day. Installing 'long life' lamps with a rated life of 5,000 hr, the bulb would last 312 days, but the actual light output is reduced by about 25% over the regular 1,000-hr lamp.
Figure 2. Low cost incandescent systems have high maintenance and operating costs. Note the dirty build-up on a long-life lamp.
Fluorescent light should be the main light source in dairy production. Fluorescent light is very energy efficient compared to incandescent, has long life cycles (when correct fixtures are installed and adequate maintenance) and can provide good light quality for livestock.
A few reasons to switch to fluorescent lighting from incandescent are listed here.
There are 2 types of fluorescent systems used on farms: compact and tube fluorescents.
Compact fluorescent (CF) lighting systems provide good energy efficiency and can easily replace incandescent fixtures. There are 2 main types: electronic ballast and electromagnetic. (See Figure 3.)
To see which size CF to install, determine the lumen output of the current incandescent lights and then match this value with the CF lumen output. See Table 2.
Figure 3. Compact fluorescent in a moisture resistant fixture. (Source: Agviro, Inc.)
To date there has only been limited success with dimming compact fluorescents, however future research will likely solve the reliability issue. Only CF systems labelled "dimmable" can be used when dimming. CF lights are a very good choice in dairy barns when low levels of light are required. However, if dimming is required, a mix of incandescent with CFs may be a good solution. (See Figure 5)
When considering retrofitting a lighting system bear in mind that CF lamps have shorter equipment life and higher replacement costs compared to T8 (standard 4 ft) fluorescent tube systems. See the section below on fluorescent tube lighting for details.
Fluorescent Tube Lighting
Fluorescent tubes come in a variety of lengths and diameters. Typically farms use 4-foot lengths (1.2m). Tube diameter is measured in eighths of an inch. T12s (1.5 in.) - the old standard- are being replaced by T8 (1 in.) and T5 (0.6 in.) systems (see Figure 4). (These are the standard industry sizes.)
Figure 4. Fluorescent tube lighting sizing.
Figure 5. Incandescent and compact fluorescent in dairy barn.
For barns where the ceiling height is less than 3.7 m (12 ft) the new recommendation is the T8 fluorescent fixture with electromagnetic ballast, mounted in weatherproof fibreglass or plastic housing with a continuous gasket between the lens and fixture. Also it is important to ensure the fixture uses 8 clips to hold the lens on so there is less chance of barn air getting into the fixture. These units are typically:
Figure 6. T8 fluorescent lights in dairy barn.
T8 fluorescents are an ideal energy efficient alternative to incandescent, compact fluorescent and T12 fluorescent systems. T5 fluorescent tube systems are shorter than T12 or T8. They produce more light, have better colour rendition (more true light), a higher efficiency and more dimming options available. They maintain their light level better than T12 and most T8 systems. They provide 95% of their original light output after 40% (8,000 hr) of their average life. T5 lamps are not recommended for use in vapour-tight fixtures due to heat build up; therefore, their use on farms will be limited to clean, dry environments. However future research will likely solve the over heating and reliability issue of T5.
Dimmable fluorescent tube lights are currently being tested in several commercial turkey grower facilities in Ontario. The advantage of a dimming system is the ability to simulate dawn and dusk periods by slowly raising and/or lowering light levels.
Photocells controllers can be used with fluorescent lights in barns with windows and curtains. The photocell controller can dim or turn off lights near sidewalls during the day when natural light levels are sufficient. This process is called Day Lighting and can save even more energy and money.
Where barn ceilings are more than 3.7 m-high (12 ft-high), for example, dairy free stall barns and machinery sheds, consider more efficient high intensity discharge (HID) fixtures, including metal halide (MH) and high pressure sodium (HPS). They are easy to install and maintain and require fewer fixtures to provide the same level of light. See Figure 7 and Figure 8.
Metal halide fixtures can be operated on either a regular or pulse start ballast. A pulse start ballast will save about 12.5% or 50 W on a 400 W metal halide fixture.
Figure 7. Metal halide fixtures.
Figure 8. High pressure sodium fixtures (the light is yellow.) (Source: Agviro, Inc.)
Light Emitting Diode or LED systems are not yet used in livestock and poultry production facilities. Research is required to ensure this technology will fit with agricultural applications. Energy efficiency of LED lamps can be very high (50 lumens/W) and life is much longer (up to 100,000 hr) than other light systems. If the technology can be adapted for barn environments, it is expected that LED lighting systems will provide large on-farm energy savings in the future.
LEDs come in various forms - spot, linear or strip (see Figure 9) and monochromatic colours. They can be dimmed.
Figure 9. LED strip lighting. (Source: GVA Lighting Inc.)
The advantages of LEDs include:
Other considerations for energy efficient lighting systems include the use of timers, programmed to turn lights on/off to meet daily livestock needs and motion sensors in personnel areas such as hallways and entranceways.
Recent innovations include:
Incandescent lights operating for extended periods of time can be replaced with more energy efficient types of light systems. The type of system will depend on a number of factors including:
Some energy efficient lighting systems, such as compact fluorescent and tube fluorescent, either do not start or operate poorly in cold temperatures unless cold start ballasts are installed.
Lights that operate daily for long durations, year-round will have faster paybacks than lights that are only turned on briefly. The quicker the payback, the more appealing a lighting system will be for most farm owners and managers.
An easy way to switch to a more energy efficient lighting system is to replace incandescent bulbs with compact fluorescent (CF) lamps and ballasts of equivalent light output. The compact fluorescent system can be screwed into the existing socket. No rewiring is involved. The average cost of a CF is $4‑$15 per light depending on the wattage. A CF has a rated life of 10,000 hr. Other energy efficient lighting systems require more effort. Installing fluorescent tubes or HID systems requires rewiring and a lighting design to ensure that the area is evenly lit at the right light intensity.
CFs come in a range of power ratings, from 5-28 W in screw-in versions and up to 55 W in hardwired models. As a rough guide, a 3:1 ratio, incandescent to CF wattage, provides the same light output.
Incandescent lamps may be economical where lights are only turned on occasionally, such as in storage rooms.
HID lamps have some advantages over CFs, including higher output and less sensitivity to starting and operating temperatures. However, they take a long time to warm up and relight if shut off; they offer fewer colour temperature choices, provide poorer colour rendering, and some units flicker at a frequency of 120 Hz. The newest metal halide lamps being introduced may solve some of these problems. HID systems are well suited to areas such as free stall or loose housing barns and some parlours with high ceiling heights.
The minimum light intensities required for various tasks or in different work areas of a dairy operation are listed in Table 3.
During winter, cows respond to the shorter daylight hours by reducing feed consumption. When they eat less food, they produce less milk. Long-day lighting (16‑18 hr. of daylight) increases milk production by simulating summer conditions. Studies show that long-day lighting can boost milk production from 5%‑16%.
Photocells can be used with most light systems. They are well suited for use in free stall, loose housing, tie stall and parlour areas. Photocells provide even greater benefits when working on a dimmable light system (such as some tube fluorescents). Photocells can sense the amount of light present in a space. They send the light level information back to a controller, which has been programmed to maintain the light at a given level (in lux or foot-candles). When natural light levels fall below this preset limit, the controller sends a signal to the lighting system and the lights turn on. The lights may come on at full brightness if a dimming controller does not operate them or they might come on just enough to maintain the light level at the preset limit with a dimming controller. When a dimming controller is used, the lights will become brighter and brighter as the amount of natural daylight declines until the preset limit is reached.
In areas requiring high-pressure washing, waterproof fixtures are necessary to prevent moisture from getting into the fixture.
Table 3 below summarizes the light intensity recommended at each section of dairy farm to optimize production from cows, to minimize cost, and maximize energy efficiency.
(Source: ASAE, 1993; NFEC, 1993; MWPS, 1992; Leech and Person, 1993)
The cost to install and operate an incandescent light system in a dairy barn with 10-100 W long life lamps in each of 3 rows was compared to the cost of a fluorescent single tube system. See Table 4 below. The calculations assume an energy cost of $0.0953/kWh (March 2005 rate) and that the lights are typically running an average of 18 hr per day. Each 100 W long-life incandescent lamp will provide just over 1,200 lumens. This system would cost about $450 to install and $1,918 annually to operate. Installing 20, 4-ft single tube, T8 fluorescent fixtures would provide an increased light level (by as much as 44%). This T8 system would cost $2,400 to install and only $511/yr to operate. So over a 2-yr period you could save more than $800 by switching to a T8 fluorescent lighting system from an incandescent one.
For a retrofit, with 100% of the capital to be paid with savings, the simple payback is 1.7 years. For a new facility, where the original cost for the incandescent system is deducted from the total fluorescent capital cost, the payback is an even faster: 1.4 years.
Over the long run, lighting on dairy farms has the potential to save energy for the farmer. One simple way to reduce energy costs by 75% is to switch from incandescent lighting to fluorescent T8 lighting. Using dimmers can also reduce energy costs. By making these changes, along with other improvements, your dairy operation lighting system will be more energy efficient. This can lead to improved farm productivity and increased revenue, while lowering energy costs.
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