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Light Distribution Pattern Analysis: Outdoor Led Lighting

Light Distribution Pattern Analysis: Outdoor Led Lighting



A second and perhaps equally important aspect of energy efficiency inside a parking garage is to specify appropriate light distribution patterns within the space. This is done both by outlining the areas that really need lighting and also considering the amount of lighting desired in those regions. A lighting-certified professional uses special equipment to quantify this information and will significantly simplify the process and will help you to choose and install the right lights for your particular situation. The two things you want to avoid are going overkill on your lighting and underachieving when it comes to the desired quality. You want to strike a balance by achieving the desired light levels while not being wasteful with your energy resources.  

Lighting distribution is also a particularly interesting issue when it comes to LED lighting because of the way the technology works. LEDs are a semiconductor and one of the significant technological advances with LED lighting, in particular, is the fact that emissions are directional (as opposed to omnidirectional). More specifically, LEDs naturally emit light for only 180 degrees while all other lighting puts out emissions for 360 degrees around the bulb. Consider a parking garage for a moment and recognize that a ceiling-mounted bulb that emits light at 360 degrees is putting half of the energy consumed directly into the ceiling. Although some of this light can be reflected, much of it is wasted right off the bat. This is a significant contributor to the energy efficiency rates that can be achieved with LEDs relative to traditional bulbs. Add to this a prudent analysis where you specify the light levels and distribution patterns for your particular space and you’re well on your way to big savings. Top it off with a smart, adaptive lighting strategy that utilizes sensors to operate lights only in the areas they are needed, during the times they are required and at the desired intensity. Chances are good that your bottom line is going to noticeably improve – particularly for large facilities with significant energy footprints.

Street Lighting:

Colour Temperature:

One major consideration for street lights worth particular emphasis is the quality difference between LEDs and traditional solutions like high-pressure sodium (HPS), low-pressure sodium (LPS), and metal halide lamps. For example, the most noticeable difference between sodium vapor lamps and LEDs is the orange color associated with HPS/LPS lamps as compared to the higher color temperature white glow from LEDs. For a full discussion of this and other differences between LEDs and HPS/LPS lamps, you can read here.



A second major consideration for street lighting (particularly in residential areas) are the energy efficiency improvements that can be made through adaptive dimming. While dimming is available with most bulbs, there are significant advantages to LEDs as compared to traditional outdoor lighting solutions like metal halide and High-Pressure Sodium (Note: HPS lights are the most common type of street light lamp). Additionally, it is very rare to see traditional HID lighting with the option to dim at all.


The advantage to dimming lights is that you reduce the energy demand and increase flexibility for spaces with variable lighting requirements. This is generally true no matter which type of lighting you use. That said, how much improvement varies significantly depending on the particular lighting technology under question. Consider the difference between LEDs and metal halide lights. According to the Rensselaer Polytechnic Institute, “When HID lamps are dimmed, the reduction in light output is greater than the reduction in system input power. Thus, the efficacy decreases as the lamp is dimmed.” That is, metal halide lights consume more energy per unit of light output the lower power they are operated at. 


This is very much like driving your vehicle in a city on the highway. Cars are more efficient per mile on the highway than they are in stop-and-go traffic. That said, this characteristic is very different from LEDs. According to the U.S. Department of Energy, “LED dimming performance is determined by driver capability and compatibility with the dimming equipment.” They go on to explain that LEDs are non-linear lighting devices when it comes to current which means that a small change in voltage can result in a large current change. They typically rely on maintaining an average and constant current level which in many cases tends to increase luminous efficacy as the current drops. This translates essentially to say “LEDs get more efficient [not less like metal halide HID bulbs] as they are dimmed.” You can read the DOE presentation here.

Further advantages include the fact that current LED lights do not shift color when they are dimmed. This is different than traditional bulbs like incandescent that tend towards a warmer color temperature as they are dimmed. Essentially what this means is that the light quality will remain constant when using LEDs that are dimmed. The only thing that will change is the quantity of light which is exactly what is desired from intentionally dimming your bulbs.

Building Exterior, Landscape, and Decorative Lighting:

Lifespan Extension:

One of the previously unstated benefits of a low-intensity operating environment (a dimmed light) is that the useful lifespan of the individual bulbs is likely to improve. The more time an LED light is operated at a low current, the longer the lifespan is likely to be. Normal expectations surrounding operating lifespan assume the bulbs are operated at 100% power and typically estimated useful lifespans between 50,000 and 100,000 hours or more. The fact that these remarkable numbers can be improved even further by operating the bulbs at low currents puts LEDs in a lighting class all by themselves.


Security Improvements:

Another advantage of adaptive lighting solutions like motion sensors is that they act as a deterrent to potential crime. Lighting levels that are dependent on occupancy both startle intruders and serve as an indicator for security patrols looking after a property. LEDs with a white light improve the visibility for patrols and may improve the effectiveness of security personnel to respond relative to their ability with a monochromatic yellow backdrop.


Features such as motion sensors and time-sensitive light level programming can be integrated into all kinds of outdoor lights (parking lot lighting, street lighting, building facade lighting, pathway lighting etc). The typical themes that make it effective include minimal obstructions such as trees, moderate height for pole-mounted sensors (20-30 feet or less) such that they are still in close proximity to objects moving on the ground, and low to medium traffic in the targeted areas (such that it actually makes sense to dim or even turn off lights at different times). For large projects, these sensors are often synchronized and/or connected using radio frequencies. With the advent of smart devices, this kind of network can now be managed both on-site and via remote internet access. Lighting schedules and alerts can be adjusted to meet the needs of a particular facility based on emerging information and/or changes inactivity.


Conclusion: Energy savings and maintenance savings vary depending on the project particulars but generally fall around 60-70%. You can read a plethora of LED conversion case studies here or send us a message to get more specific information related to your particular need. We recommend working with an experienced lighting contractor to select the appropriate lights and the appropriate adaptive controls. Experienced distributors and project managers can help you save money and successfully plan the specifics of your project.

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