Retailer Energy Alliance Parking Lot Lighting Technology Procurement Webcast (Text Version)
Below is the text version of the Parking Lot Lighting Technology Procurement Opportunities Webcast, presented on May 23, 2008. Michael Myer from Pacific Northwest National Laboratory was the only presenter. This presentation provides an overview of the Retailer Energy Alliance (REA) Working Group activities in support of this project, light-emitting diode (LED) technology application in retail parking lots, and critical specification issues for the REA to address. You can also view the slides for this presentation (PDF 556 KB). Download Adobe Reader.
Michael Myer:
Hello. Welcome to the LED Outdoor Area Parking Lot Lighting Technology Procurement presenting. This is a Retailer Energy Alliance project presented by Pacific Northwest National Laboratory on behalf of the Department of Energy.
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Today we're gonna discuss a couple of features, one being the LED Parking Lot Working Group, and then we're gonna review LED technology application in parking lots, and critical specification issues that the REA will be trying to address in developing its specification.
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In 2008, the REA was established to help speed market introduction of solid state lighting luminaires into the marketplace. One of the first technologies that was identified was parking lot lighting. So the working group is designed to do a couple different things in the field, measurements, and demonstrations, as well as participating in laboratory measurements, and help maximize sales of selected products.
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This is a brief overview of the timeline and projected milestones of the REA working group. And so it established of April of 2008. The specification will be developed during the summer. Products will be selected between the summer and the fall, and field-testing and laboratory testing will occur. The specifications will be hopefully finished in October of 2008. And then a release of a request for a proposal in the late fall of 2008 for an evaluation of proposed and selected winners in the early winter of 2009.
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The image here is a comparison of high pressure sodium on the right, which is that orange colored lighting, and LED lighting on the left, which is the white lighting. This is a typical parking lot and it's a good comparison of the two different types of technology. In addition to the stark color differences, notice that over on right under the HPS lighting, there's a real definite hot spot, a very bright light, and then kind of a dark spot in between the fixtures.
Whereas, if you look over at the left image, you'll see that while it does get brighter in certain areas, it is not such a pronounced hot spot, as well as there's really less pronounced dark spots. And those are characteristics of LED lighting and HPS lighting.
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The typical decision process in lighting design is as follows. Now the list here is not entirely — well, it is chronological order. It actually gets repeated a couple of times through the different phases of design, between design development and construction documents, so it's not uncommon to go through this two to three iterations, even four times, depending on the size of the project, going from a high level to a specific level through the course of a project.
Lighting criteria tends to drive a lot of the decisions, though budget and specifications also factor in later on.
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Currently, most parking lots are lighted with metal halide; some use high pressure sodium, for retail. You tend to see roadways lighted with high pressure sodium unless it's metal halide.
Most parking lots use a pole with many heads or luminaires, and that's because a pole is the most expensive part of the lighting system because of the trenching and the construction that's involved to anchor the pole. So you try to minimize your number of poles and maximize your heads on a pole.
Most retailers are requiring more light than what the IES recommends. At minimum illuminance's an RP-20, and we'll discuss that a little bit later on. Typically, lighting can operate up to 12 hours or more per day through the night. And then there's some environmental issues with LED parking lot lighting that we'll address a little later on as well.
LEDs have really gained a lot of momentum in the last couple years. There've been some major technological advances which have allowed for that. But this is a comparison of what a new LED parking lot would be. The pole cost is always gonna be the same, or virtually the same, so you're gonna use a lot of luminaires with LEDs regardless if it's HPS or LED, actually. LEDs are gonna need to work for both retrofit and new construction designs.
As I showed earlier, the hot spots don't exist with LEDs as much, so this might allow illuminance recommendations to actually be able to shift a little bit. LEDs are gonna be good for some new energy code requirements, and LEDs have limited environmental issues.
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Why LEDs make sense for retail parking lots are as follows. Maintenance probably is the single larges driving factor. An HPS lamp has a life of anywhere from 20,000 to 36,000 hours. Metal halide is much lower. It's anywhere from 10,000 to 20,000 hours. And you're seeing LEDs somewhere in the neighborhood of 50,000 hours. And I put in the neighborhood 'cause there's a couple factors that you have to deal with, but that's a fair number that a lot of manufacturers are using right now.
And so you're seeing that in the terms of metal halide, LEDs are anywhere from two and a half to three to five times as long lasting. And if you don't have to send out a work crew and a bucket truck to replace all those lamps, that saves a lot of money in maintenance costs.
Then LEDs save energy. This is because the optics for an LED luminaire are much different than they for an HID luminaire, so you're gaining a lot of in optical efficiency and better luminaire design.
Again, because of optical efficiency, you can have better optics and not light outside your parking lot boundaries which makes the site a better neighbor, and that's really a benefit of LEDs. Because they're all individual point sources, the optics can be much better controlled from like HID which has to use one lamp and build all the optics around that one lamp.
Again, we're gonna continue on optics and notice the improved uniformity there. Because there are many different points of light in an LED, you don't really have that hot spot directly under the luminaire, and you can actually get a more uniform lighting appearance in the parking lot, which is very beneficial, which leads to better visibility and enhanced perception of safety.
Finally, everybody's really looking at the environment and how people can reduce their carbon footprint and become more green. And it's important to know that LEDs don't have any mercury in the product themselves, and whereas HID actually use mercury to start the lamp and it's integral to the lamp. And mercury's a big buzzword because it's a neurotoxin, and so it's important to know what products do and don't contain mercury.
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Design issues when lighting a parking lot really fall into these six major items: the appearance of color, illuminance detection — that's for safety — light pollution, glare, and so on. So those will be addressed when considering changing from standard HID technology to LED technology.
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Color Rendering Index is how accurately a source represents color. The graph over on the right shows what's called the spectral power distribution, and that's really the amount of energy and the different wavelengths of the visual spectrum. And so you can see that on the bottom left, you really have indigo almost ultraviolet at 350 nanometers, and as it moves to the right, it goes across the colors of the rainbow as we learned 'em, to 750 800, which is red, and essentially ultra infrared.
And the curves represent what's known as the spectral power distribution, and the SPD is the amount of energy across the wavelengths. So you can see that the line that's blue that starts off in the low left and goes to the upper right, that's incandescent, or it's actually halogen, and it's a very broad bold spectrum source. And so that's why incandescents make colors and people great is because it's really encompassing a majority of the spectrum and fair amount of energy in that spectrum.
Whereas, if you look at HPS, that's the more teal line, and it starts out low in the low wavelength and then it peaks around 550, and then peaks again around 580, and then peaks just below 600, and then kinda drops down. So it's more of a narrow spectrum and so its CRI tends to be in the neighborhood of 20 out of a scale of 1 to 100.
Metal halide is the red, and you notice there's a lot of humps and a couple of major peaks and stuff like that. So metal halide is a broader spectrum which allows it to have a higher CRI, in the neighborhood of 60 to 70. Ceramic metal halide can actually be upwards near 85.
Now notice how LEDs, they have the major spike at around 450, and then it drops a little bit, and it's a very large hump in the mid section which allow LEDs to have a very high CRI of greater than 70. So it's beneficial to have a broad-spectrum source to get greater CEI.
In a parking lot, it's important, so it helps you to differentiate between different types of color of cars as well as fabric in terms of what people are wearing in case you need to identify someone. And it just makes the place seem more pleasant the better the color is rendered, to be honest.
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Correlated color temperature is the appearance of the source. The graph on the right shows what's known as color space, and it shows that here's a line of really what things can be considered white, and you'll see that's the curve. High pressure sodium has a color temperature of around 2,200k, and that's that amber, that orange that everyone's familiar with, and it's actually still considered white. Whereas, metal halide is anywhere between 3,000 and 4,100 Kelvin. And then, again, notice that as the number moves from 3,000 to 4,100, you see that it's white and then it kinda gets a hint of blue.
LEDs, they tend to be more white with a blue tint. I know a hint of blue and blue tint is somewhat semantics, but when you're around them, you'll experience it more the actual shifts. But it really just shows you that really you want something greater than 2,700k and something below 6,000. Anything above 6,000 really gets blue. Anything below 2,700 is really more amber and orange. This shows just the range of the available color temperatures.
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As I mentioned earlier, we are gonna discuss what the IES recommended. For those who don't know, the IESNA is the Illuminating Engineering Society of North America. It's an organization that sets recommended illuminances. They tend to minimum illuminances, or average illuminances. And they also set things such as contrast ratios or uniformity ratios 'cause that's important as well.
So RP-20 happens to be a recommended practice, which is what RP stands for, and 20 happens to be the number for parking lots. Currently, the last time this document was revised was in 1998, and they recommend .2 foot candles horizontally for basic places, and basic parking lots, and in parking lot where enhanced security is need, .5 candles.
Uniformity ratio is really important, especially outdoors. They recommend a 20 to 1, which is a minimum to maximum. So if your minimum was .2, your maximum could be 4 foot candles is what that chart is saying. And that's important because the greater the uniformity ratio is, your eye — it's known is what's called adaptation, and if your eye walks from a dark spot to a bright spot, your eye changes and that takes a little bit of time and it can be a little painful to your eye, kind of like going from the inside of a movie to the outside of a movie theater. That's adaptation, but it's important outside. You really don't wanna keep constantly changing in and out of adaptation as you walk through a parking lot if you're walking in and out of hot spots.
So this table just shows what the current recommendations are based on RP 20 1998. And, again, those are all minimum values.
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Parking lots are currently being lighted somewhere between two and five foot candles. This is from a query of retailers, as well as research of what common practices are. The minimum recommendations vary on needs, and the recommendations were based on conventional light sources. So that's really why you had that large uniformity ratio was that, as I said earlier, that an HID lamp, or luminaire, actually, is based on just the lamp which is very large, and you build your optics around that.
And it's really hard not to create a hot spot because it's a much larger source, and they had to allow for a large uniformity because of that. Whereas, with LEDs, you can get a much tighter uniformity because you're not designing on a very large source; you're designing around many little sources.
Whereas I said earlier, the IES recommends a 20 to 1 uniformity ratio, or for enhanced security, a 15 to 1 uniformity ratio, a 5 to 1, a 10-to 1, possibly even a 3 to 1 uniformity ratio might be a possible. Below a 3 to 1 it really is not important because visually your eye needs about a 3 to 1 ratio to detect the difference in illuminance. So 2 to 1 or 1 to 1 really you're stretching the need for anything for that because your eye physically can't actually see it. So it's really you're striving for something that really doesn't matter.
You also might be able to push for a recommended illuminance of .5 foot candles rather than 2 to 5 foot candles using LEDs, because again, you're getting this better uniformity. But again, that would be a minimum and a parking lot could easily exceed that. But that would be one recommendation.
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This is a comparison graphics of two simulated parking lots in lighting software. On the left you'll see a parking lot with metal halide, and on the right you're seeing it with LEDs. And you can see roughly the watt, which on the left is 455 for the metal halide, and then the LED, it's 218. There is probably somewhere in the neighborhood of a 50 percent savings for most LED designs against metal halide after you factor in a couple other things.
But what's more important here is that on the left you that, again, it's this hot spot, dark spot, hot spot. On the right you do get an enhanced area of brightness and then a soft gradation, and then, again, another enhanced area of brightness, but it is much less pronounced. The averages and uniformity issues values are below the graphics. So notice on the left it's an average of 3.5 foot candles, and a minimum of .9. So while the design was striving for a minimum of .9, the average was much higher because, again, the polar options. And notice that the max to min ratio is 10 to 10; allowed 20 to 1, so that could be even more exaggerated.
On the right, the minimum was 1.2, and the average was 2.8. So those values were a little closer, but noticed that the min to max ratio was 4.3, so it's a much more uniform appearing parking lot.
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The next issue is illuminance, which we've been discussing on the IES RP 20, but this is more what's happening how with illuminance. The Model Lighting Ordinance is a series of recommendations for municipalities to adopt, to write a lighting ordinance for outdoor lighting. It was developed in conjunction with the IESNA, and the International Dark Sky Association. And as I said, it's typical code language. But they're actually recommending not a static minimum illuminance. They're actually subdividing it. And so if you're out in a very rural area, you need less light compared to downtown Los Angeles where you're gonna need much more light because of the already surrounding illuminance.
The uniformity is a bigger issue than illuminance. We tend to think of, "Oh, I need this much light." But in reality, you wanna have less drastic ranges in uniformity. Security cameras can work in low light. The bane of all security cameras as are is extreme contrast. It causes cameras problems.
The illuminances need to be driven by the retailers. Since the IES is releasing only a minimum, the retailers tend to request much higher illuminance levels. And so any changes in practice really need to be driven by the retailers instead of the ones setting those values.
The next thing we need to address in terms of illuminance is the different visual state to the eye. A lot of LED manufacturers — or a fair amount, actually — are pushing the other types of visual states. Photopic vision is what most people are used to. It's a nice way of saying it's daytime vision. This occurs in very high light levels and it's attuned to longer wavelengths. So things that are in the larger end of the spectrum, such as ambers, reds, yellows, tend to excite the photopic visual system better than something in the bluer range.
In extremely low light situations, under a starry sky or just barely moon lit sky, you're in what's known as scotopic vision. And there, your rods are only acting and you really can't see color and the periphery of your eyes are working. And really, this dates back to early times where you needed to sense an animal or something because you had virtually no vision. But it's attuned to shorter wavelengths, so your blues, your violets, even slightly your greens really have much more energy. But for the most part, scotopic vision doesn't occur in parking lots because you're out of that starry night condition.
So really what needs to be addressed is what's known as mesopic vision, which is kind of a combination of photopic and scotopic. It's using both your rods and cones. The problem with solely focusing on mesopic vision is that the formal definition of this function and how this curve works in your eye has not been accepted by international and US bodies of science, so they're still trying to actually fine tune the science of it.
In the end right now, it's recommended to focus on just photopic values because that's how everything is being reported in terms of catalogues, and that's how most meters work right now. In the future, this might slightly change, but this is the current state of the science of lighting.
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Selection your lumen package is really how you deliver your illuminance. Metal halide and HPS, every time you change a lamp size and go up into a larger lamp, you jump in about a 50 to 70 watt increment, which corresponds to about 300 to 500 more lumens, which is fine except it doesn't allow you to fine tune. You may not want that 500 more lumens or that 400 more lumens. You really only need 200 more lumens, and that's kind of a down side. You're kinda stuck with what your options are.
Whereas, LEDs, are much more flexible. These tend to be made of arrays, contain 10 to 30 LEDs. And so if you need just a little more light, you can just put in another array and get a little more light and that prevents really over or under lighting.
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The next thing to factor in is that over time, a light source is just gonna produce less light. That works for most light sources. Specifically, this is a graph of HID sources output over time. Notice that in the beginning, everyone seems to be putting out 100 percent, but quickly hull star metal halide after only about 2,000 to 3,000 hours, quickly declines, and then it levels out.
And if you look at CMH, it's more of a continual constant degradation. And HPS is similar, but the degradation slope is less drastic.
LEDs were not shown on this graph because the exact function that factors how you determine the output over time is still being developed by the IESNA, but it would be a falter curve, really is what it is, is that very slowly over time it will decrease, but that's just an example of how it's gonna work.
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Current designs with HIDs luminaires use standard distribution. A Type III, this is symmetric and oblong. It tends to light just the roadway. It's idea for roadways. Type IV, this more asymmetric and it tends to push all of the light directly in front of the luminaire. It's good for perimeters. It's got some applications in parking lots; it depends.
Type V is a typical one for parking lots as well because it's circular or square. So if you put it in a parking lot on an island, you can light everything around it. You really need to optimize your distributions for your exact parking lot, but these are the typical distributions. It's important to know this. It's that some LED early manufacturers were deviating from these distributions. But for the most part, most manufacturers now are still designing to these distributions 'cause they're tried and true and kinda work.
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A rule of thumb for locating your pole for HID luminaires is this 2x 4x rule, which says roughly your mounting height is the distance from the pavement to the luminaire. And you don't want your pole to be any more than roughly two times that height from the edge of the area to be lighted, and you don't want your poles to be four times that distance apart.
Again your poles are the most expensive part of your equipment. The trenching and the concrete and the poles really drive the cost. Typical designs of poles are located in the center with many heads, and you try to limit your perimeter poles, again because of cost.
LED parking lots should be able to reuse most of the pole locations or retrofits. New construction might allow for some of this to change, so we'll see.
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This is a good demonstration of this 2x 4x rule as demonstrated. You can see that the mounting height is the distance from the pavement to the luminaire. And then you see that you don't really want 'em to be two times away, and you want your poles to be no more than four times apart, and that provides good coverage.
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Continuing on with mounting height. HID lamps are pretty much similar across different manufacturers, so rules of thumbs have been developed. Typical mounting height for a metal halide lamp is 20 to 30 feet. For HPS it tends to be 18 to 25 for 250 watt, and 25 to 35 for the 400 watt.
As you see, the higher the mounting height, less poles. And somewhat higher the mounting height, the more power's needed. However, there's a caveat. You can actually use less energy on a site by using less poles. Even though you're using higher wattage lamps, you're still using fewer watts aggregately.
LED parking lot lighting. Pretty much what you do — and this is the same way you do it with HID — is that you figure out what your illuminance level should be, and then you just reverse engineer to figure out what the amount of lumens you need. We anticipate roughly right now for most parking lots that you should be able to do it between 22 feet and 30 feet mounting heights. It's probably gonna go up to 42, even 50 feet. Again, it's gonna depend on the product. But this is just current quick calculations that we've done just to estimate what the mounting heights roughly should be.
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Environmental concerns with HID luminaires. As I mentioned earlier, HID lamps contain mercury. Polycarbonate is a nasty product. It's a good product, but actually in the process of making is what's the nasty part. It involves a fair amount of chlorine and that's just kind of bad. Lead can be on the solder of electronics of the ballast, and that's important to deal with.
LED luminaires, as I said earlier, are mercury free. The lens can be polycarbonate. They're not always polycarbonate. It's just something to think about. And again, the lead can be in the solder for the electronics. But many manufacturers for most electronics now are making lead free solder. So it's just something to think about.
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Other environmental concerns with HID parking lot lighting. Currently, HID is the best in class right now for lighting a parking lot, but it's still inefficient. As I mentioned earlier, there's about 20 percent light loss just from the lamp never gets to leave the fixture because of the optics. The ballasts are only 80 to 90 percent efficient, so there's some other work that could happen there. And these inefficiencies lead to more greenhouse gasses.
In contrast, LED parking lot lighting, as I mentioned earlier, are more optically efficient and drivers, which is similar to ballast, but not the same. They tend to be in the higher end of efficiency. And less power and energy, leads to better energy efficiency, and those lead to less greenhouse gas emissions.
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This slide reviews energy codes. Standard 90 is the ASHRAE IES recommended energy code. The current version is 2007. Two thousand ten will be released in 2010. Title 24 is California's energy code. The current version is 2005 with 2008 to be released I believe at the end of this year.
And as I indicated, what this is, is that for the different lighting zones, one, two, three, and four – and as I mentioned earlier, the IES is recommending different illuminances for these different zones – one being extremely rural, Zone 4 being urban, Zone 3 being more suburban, etcetera. Zone 2 is more residential. Because they're recommending lower illuminances for each of those different zones, the energy codes are then requiring different power densities for those parking lots.
So how this works is, in Zone 4, you'd be allowed .13 watts per square foot. Based on the size of your parking lot, you sum all of the input watts, and it needs to be less .13 watts per square foot.
Title 24, as we understand it, is converting from watts per square foot to lumens per square foot. I don't believe that'll be in the 2008 iteration of the code, but I don't know that for sure. But it's just a possible change. It's actually, as I understand it, based on the watts per square foot. You multiply watts times luminance per watt, and that's how you develop the number, but I don't know enough about the exact specific.
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Moving beyond energy into light pollution, which is somewhat energy, but more environmental, and the things to think about when lighting a parking lot are light pollution, which includes light trespass, skyglow, and glare. The old remedies — and this worked all outdoor lighting technology — were terms called full cutoff, semi cutoff, and non cutoff. These were IESNA destinations of the different distributions. And they mainly try to do two things at once, limit skyglow and glare at the same time. And the IES has now adopted a newer system which is known as the Lighting Classification System. And there's really easy way to remember it which is BUG, which is backlight, uplight, and glare.
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This figure really shows you the difference. So your B zone is your backlight, your light trespass. On a perimeter pole, this would be really important. In a pole in the center of the island, it would not be important because you'd want symmetrical distribution. But it's important to know that backlight addresses your light trespass and what those areas are.
U is the uplight zone. So this is really addressing skyglow. And the G is the glare zone, and that's what makes parking lots uncomfortable when walking through them is the glare from the fixtures.
The IES is getting to release values of how to evaluate this new classification system.
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Again, this is a quick recap of those different zones and things to think about for each of those zones.
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Lighting curfew is an energy and somewhat environmental thing that some codes are now addressing. Essentially at some point in time, the parking lot either reduces the amount light or turns off certain fixtures, and this is, as I said earlier, to save energy, but as well as to prevent skyglow. Some codes and ordinances already require a curfew; more are expected.
There's different ways to accomplish a curfew with an HID luminaire. You can switch every other fixture, but that can be problematic because it can leave dark spots in a parking lot. You can dim with an electronic ballast, but that's not as desirable because dimming with an electronic ballast, the efficiency with the way the ballasts work does not track linearly. And so as it dims, the product actually becomes less efficient. And so while you're saving energy, you're not saving as much energy as you expected to save. Also, metal halide lamps have been problematic in certain types of dimming.
You can use a secondary capacitor for bi level operation, and that has similar problems to dimming. The California Lighting Technology Center is actually developing a bi level sensor to do something similar to this with HID luminaires. However, LEDs work much different. You can easily dim an LED luminaire and avoid a lot of the problems that I just addressed with the curfew in HID luminaires.
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Moving beyond the environmental conditions to how the luminaire is going to operate in the said environment, the first thing that affect all luminaires, regardless of the source, are water and dirt. UL is Underwriter Laboratory, and they used to have was known as a wet location. And still exists, but it's somewhat the old standard and it's limited in definition. Whereas, a lot of manufacturers are now moving to what's known ingress protection. It's a newer standard. And IP rating of 65 is recommended. The numbers vary, though. But this is just a value that's recommended.
The first number refers to solid objects. Six means that it's totally protected against dirt, which is the absolute highest number in the first category. The second category refers to how the object is sealed against water. Five, as I said, the number refers to liquids. A five means it's protected from water jets. A value of 68 is the highest IP rating that exists, which means that the objects can be submersed for a serious period of time and still operate.
Temperature is a big factor in environmental conditions. Heat can damage LEDs, but good luminaire design can handled the heat. Parking lot lighting is gonna mostly occur at night – or it should occur at night – and problem in more colder temperatures than during the day, which actually benefit LEDs 'cause they perform better in cold temperatures, so it's an advantage.
HID, for the most part, handles heat and cold okay.
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Maintenance, as I mentioned earlier, is a driving factor in parking lots because it's expensive to send out a work crew with multiple people to use a bucket truck to get up there and re lamp and do whatever they need to do to the luminaire. Typical luminaire warranty for unexpected failure is about five years, and an acceptable LED luminaire warranty should also be around five years. Anything below that, it's not worth it and you just require a five year warranty.
And then there's what's known as expected device failure, such as a lamp. As I mentioned earlier, metal halide lamps are gonna fail 10,000 to 20,000 hours, HPS somewhere between 18,000 and 36,000; it depends on the type of lamp.
LED luminaires are much different. They're gonna last for around 50,000 hours, which leads to big maintenance savings. LEDs need to treat end of life slightly different, and that's something that'll addressed in the specification.
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Price is a serious driving factor for most projects. Initial outdoor HID luminaire price ranges, you can see on the left, which your typical shoebox. That ranges anywhere from $300.00 to $650.00, and that's for the head, not the pole and everything else. And so you can get to something more serious, which is known as an architectural style fixture, which is kinda sleeker, kinda fun. It probably has really good optics in it using a multi segmented reflector or some other type of well designed optics. And that's somewhere between $800.00 and $1,000.00. Then lamp is anywhere from $20.00 to $50.00. So HID luminaires are not cheap.
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The initial price for LED luminaires varies. They can be anywhere from as low as $750.00 to as high as $2,000.00. Now this is just a quick sampling of the price of existing LED products. The prices vary widely. The DOE projects the price reductions over the next five years, and it also varies by quality. You probably can find something out there for less than 750. If you find something for around $200.00, I would be circumspect of the quality of it. If it costs $3,000.00 you might be a little questionable of what you're buying there as well.
The biggest difference, unlike HID with LEDs is that the difference between a 400 watt metal halide lamp and a 1,000 watt metal halide lamp is virtually nothing. It's really maybe $5.00 $10.00. The luminaire is actually gonna cost the exact same amount because they design the luminaire around the more expensive fixture.
LED luminaires for every array that you put in there, the price will go up. So the more light you need, the more expensive the luminaire will be. It's somewhat of a linear relationship, and that's very different than HID in luminaires.
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— which us into the life cycle cost analysis. So LED luminaires use less energy, which means you pay the lower utility bills. They're going to lead to better maintenance, which reduces cost. And then there is possible incentives from utilities and EEPS for either saving energy or power.
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So we've now reviewed the design criteria and design decisions for parking lot lighting design. This is now moving into things to think about for the LED parking lot specification.
So the first thing to think about is illuminance. It drives a lot of the decisions. What is the minimum illuminance desired? What's the desired max-to min ratio or uniformity ratio? Consider different specifications for environmental zones. Maybe if you're out in rural Vermont, you don't want to have the same specification for downtown Atlanta.
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The next thing to consider is color because it does affect the feelings of safety and just how colors are perceived in a parking lot. Require a CRI greater than 75. That's pretty standard for most LEDs now, so there's nothing new there.
You should allow for a deviation of roughly 500k, or Kelvin, in the CCT. Closer is a slower deviation assigned, but it's understandable that there's gonna be some deviation in color temperature, and so retailers should select their color temperature preferences, something probably above 4,000 'cause that would be similar to what they're using now with metal halide. Probably something, though, lower than 8,000. There are LED products on the market that are greater than 8,000, but they can be seen as actually too bright, or even glary.
A great example of this is new headlights. Older headlights were based on halogen and they're more yellow, and they have no new HID headlights and they tend to have to have blue tint to 'em, and a lot of people complain that they're brighter and glarier.
As I mentioned earlier, the spectral power distribution is the way the light source produces power across the visual spectrum. Certain lower wavelengths actually affect glare. So you don't wanna go too high in terms of color temperature because it can actually become somewhat of glare.
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The next thing to talk about is pole location, what the current pole spacing is for the retail site location. What's the ratio retrofit to new construction applications? If there's a lot of retrofit, it might be recommended to use the current pole spacing. If it's a lot of new construction, it might make sense to deviate from the standard pole spacing to a new pole spacing based on a newer luminaire design.
And that goes similarly with luminaire mounting highs. How high are the existing luminaires mounted? How tall are the pole? 'Cause that'll affect whether or not you can place a luminaire higher than the current location.
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What are the desired energy savings? What's the current parking lot power density or current lamp wattage in typical spacing? 'Cause that'll pretty much tell you what the power density looks like. Is 20 percent or more energy desired to be saved? Twenty percent was just a value we picked out. Some people might want to save 50 percent or 40 percent energy against what they're currently doing – or more. It's just more of a conversation starter value.
Is the retailer interested in non power energy savings? And non power energy saving is something like a lighting curfew or where you turn off the lights at midnight or dim them all down except for two when the space is not occupied, something similar to occupancy sensors where the lights might go down to 30 percent output when no one's there, and then somehow a devices triggers 'em to turn on to full output when someone drives in to the parking lot or someone approaches the pole. Those are non power energy saving devices. It something to consider when the specification for this project is being developed.
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The next thing to consider is light pollution. You should restrict your uplight because it's skyglow. And in addition to it preventing people from seeing the night sky and creating that fun haze as you drive into a town, it's really, by definition, wasted energy because there's no value in lighting directly above the luminaire. You're trying to light the roadway surface or a building surrounding it or something else. So anything that's going above the luminaire is pure wasted energy and light.
You should also restrict your lumen output in the very high zones 'cause that's glare. And it's good to be a good neighbor, and so restricting your backlight is important as well.
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Next to consider is luminaire performance, and this is where the specification is actually delving into of LM 79, which the IES test procedure for solid state devices. It requires different type of photometry, which is how you test luminaires. It sets the operating temperature of the luminaire. Because as I mentioned earlier, LEDs perform different at different temperatures, so it sets the standard.
DOE assisted in the development of the standard, so it's an industry and it actually was just recently accepted by the IES.
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The next thing to consider in your specification is the rate of life, which is more of a quality control. As mentioned earlier, LEDs, I said they had a different depreciation curve. They're not gonna burn out. Where an incandescent is just gonna fail one day, an HPS is going to kind of work and then all of a sudden it's gonna what's known as cycle, which means to turn on and off, and then one day it'll just stop.
So the LED approaches its end of life is being developed by the IES, and the document there is Washington as LM 80. And the specification already is considering different things about how to rate life.
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Next steps with the program is that retailers should consider what illuminance they want and their uniformity requirements, again, their desired energy savings and more information about their luminaire layout.
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And the immediate next steps, things to think about, are to remember that the current number of LED manufacturers is somewhat small. Recently, Lightfair was held in Las Vegas. This is a big tradeshow by lighting manufacturers where a number of manufacturers announce new products. There were a handful of LED parking lot luminaires that were announced at that time. And so what that means is that previously price was being affected by the limited number of products out there. But now with more products entering the market, price should go down as well as availability should go up.
The REA Supplier Summit was held in early June in Denver where retailers met with manufacturers and they said what they needed and what products that they wanted that didn't currently exist. And LED parking lots were addressed there.
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So at this point, this I what the LED parking lot specification project is currently at. There's currently ongoing meetings, and I would direct you to refer to Linda Sandahl of Pacific Northwest National Laboratories if you'd like to participate in any of the next steps for the discussion of the specification, or if you have any questions.
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