Canopy Lighting Technology: Don’t Be In the Dark

Nowhere in the petroleum equipment industry has lighting changed more than on the canopy. In the first of a two-part series, Meredith Anderson sheds some light on the evolution from incandescent to metal halide lamp technology.

Canopy lighting technology of 1999 is light years beyond its quaint ancestor that first appeared in “gasoline” stations around 1915. Today, canopy lighting serves the multi-dimentional needs of both customers and marketers. The best of canopy lighting:

• alerts customers that the service station is open, inviting them into a bright, sparkling world;
• helps them perform the tasks necessary to complete the fueling transaction safely;
• directs lighting on the dispenser face, site of transactions and marketing displays;
• fulfills customers’ need to feel safe and secure in a night-time environment;
• guides the way to the convenience store; and
• reinforces customer loyalty through accurate rendition of corporate colors.

Typically, the lighting that predominates in a canopy structure is that of the bright, downward light that illuminates refueling islands on the underside of the canopy. Indirect lighting from inside the canopy can create a glowing canopy fascia. Accent lighting on the canopy fascia also serves an aesthetic and marketing function. For the purposes of this series, only the bright lighting that highlights refueling islands will be referred to as canopy lighting.

The technology that underlies the design of both the lamp (“light bulb”) and luminaire—the complete lighting unit that houses all of the elements necessary to produce the light—is complex and has evolved over the course of the latter half of this century. Part One, this article, focuses upon the evolution of lamp technology; Part Two, focuses upon the revolution that has occurred within the luminaire.

Photo 1: Typical attached canopy with incandescent lighting. Photo taken in 1941 in Winston-Salem, NC. Courtesy of Wayne Henderson, Petroleum Collectibles Monthly

Photo 2: Unusual free-standing canopy with incandescent lighting. Photo taken in 1941, Harmony, NC. Courtesy of Wayne Henderson, Petroleum Collectibles Monthly

Photo 3: Kerr-McGee was one of the first major oil companies to specify canopies. This station opened in 1965 in Oklahoma City. Courtesy of Wayne Henderson, Petroleum Collectibles Monthly

In the beginning…
According to petroleum historian Wayne Henderson, the earliest canopy lighting from 1915 through 1935 utilized incandescent lamps that would incandesce (glow with heat) when a sufficient electric current passed through the filament. These lamps were often housed in gas pump globes hung upside-down around the canopy perimeter, actually an extension of the gas station’s eave (see Photos 1 and 2). Some attached canopies disappeared during the mid-1930s with the advent of the standardized design of new “service stations” and growing concerns for vehicle height.

Between 1955 and 1960, independent marketers introduced the forerunner of today’s free-standing canopies, modeled after canopies used in drive-in food operations. These canopies employed less expensive fluorescent lighting (see Photo 3). During this period, mercury vapor lamps also appeared. Both fluorescent and mercury vapor lamps had advantages over incandescent lighting, but had downsides as well.

“Mercury vapor lamps, widely used from roughly 1958 to the late 1960s, were an effective light source,” says lighting consultant Terry McGowan. “But mercury, with its greenish-blue cast, rendered reds a brownish color.” Color-correcting phosphors were later added to bring reds back into the picture. In addition, mercury vapor lamp performance deteriorated over time. “Mercury vapor lamps simply refused to burn out despite notable dimming,” explains lighting engineer Nancy Clanton, PE. “At some point, a mercury vapor lamp at the end of its lifespan would be down to five to 10 percent of its initial light output. You paid for the electricity, but got nothing for it.”

“Fluorescent lighting offered excellent lighting quality, but temperature sensitivity led to problems in service stations,” McGowan continues. “At low temperatures, lighting dimmed substantially. Some service stations actually had two sets of lamps—one for cold weather, the other for warm. Changing lamps twice a year was not only a nuisance, but involved the added expense for storage space.”

High pressure sodium (HPS) lamps appeared in 1965 and offered high efficacy, but also rendered colors poorly. “High-pressure sodium lamps generate as much as 125-140 lumens per watt,” says Doug Paulin, Product Manager for Ruud Lighting, “but produce a light rich in oranges and yellows, which distorts reds. Greens and blues are quite muted. This affects the rendering of corporate colors, but also, psychologically, is perceived by some people as ‘crime’ light because of their widespread use in street lighting.”

Metal halide lamps and canopies
Lamp engineers and designers continued to search for a canopy lighting source that would address efficiency of the light output and, with the growing emphasis on corporate colors, render colors effectively—a “white” light source.

“In the early 1960s, GE Lighting patented a metal halide (MH) lamp, which reached the commercial marketplace about 1965,” recalls McGowan. “Metal halide lamps were not only twice as efficient as mercury vapor lamps, but represented a whiter light. Our mission at the GE Lighting Institute was to develop applications for this new light. From the beginning, we worked with oil companies, service station owners, specifiers and architects on prototype designs.”

MH lamps, along with fluorescent, neon, mercury vapor, low-pressure sodium (LPS) and HPS lamps, are categorized as electric-discharge lamps. In contrast to an incandescent lamp, “an electric-discharge lamp contains an arc tube that sets up an electrical discharge—sometimes described as a controlled bolt of lighting—that interacts with metals and gases inside the arc tube to convert electricity to light. This process in a metal halide lamp is about four times more efficient than an incandescent lamp,” says Terry McGowan.

MH lamps are descendents of mercury vapor lamps in which sodium and rare earth metals, such as thallium, indium, scandium and dysprosium, in the form of halide salts, usually iodides, are added to the arc stream. The chemical “stew” broadens the color spectrum of the lamp. Mercury vapor, HPS and MH lamps can also be generally classified as high-intensity discharge (HID) lamps. “The metal halide is nearly a point source—very small, very compact, but very bright.” says Nancy Clanton.

Early versions of metal halide lamps—The earliest or traditional MH lamps contained an outer glass envelope (or jacket) and the arc tube inside, which included (1) a mixture of metal halides and argon gas, and 2) three electrodes, one of which was termed a starter probe (see Diagram 1A). The two primary electrodes, positioned on opposite ends of the arc tube, provided the pathway for the arc stream. The starter probe, located at the lamp end closest to the electrical source, provided the “kick start” to initiate the main arc after power was turned on.

The process of manufacturing the arc tube of a traditional MH lamp begins with a cylinder of quartz heated to a high temperature. “A machine holds the tungsten electrodes in place on the end of the quartz tubes. A stamping die then pinch seals the ends,” says Doug Paulin. “Any air trapped in the arc tube is pumped out to prevent oxidization in the presence of an electrical arc and replaced with an inert gas, such as argon, at a pressure of one atmosphere.”

When a lamp is turned on, the voltage across the starting electrode and the primary electrode next to it creates a small electric spark. The spark, in turn, ionizes a small amount of the arc tube chemicals, which establishes the main arc between the two primary electrodes.

From this point, the lamp warms up to full brightness in five to eight minutes. “The heat of the arc allows the metal halide atoms to dissociate into metal ions and iodides,” says Bill Ryan, Group Product Manager for Phillips Lighting. “The elements produce specific wavelengths that, when taken in combination, produced high color-rendering ‘white’ light.”

Problems—Though an improvement over other “white” light sources, (e.g., mercury vapor), earlier versions of the MH lamp presented problems that eroded overall performance:

• Heat loss in the arc tube, reducing the efficiency of the ionization process—“The metal halide arc performs more efficiently when temperatures within all areas of the arc tube maintain a uniform level of high heat,” says Doug Paulin. “Contributing to heat loss in the arc tube was the size of the pinch seals on the ends, causing heat radiation from the tube ends.”
• Tungsten evaporation and wearing of the electrodes within the arc tube—“With traditional starting of high wattage metal halide lamps, there was significant evaporation of tunsten off the electrodes,” says Bob Ponzini, Applications Manager, OSRAM Sylvania of North America. “The tungsten can end up on the inner wall of the quartz, slowly blackening it. As a result, light output would drop as the blackening increased.”
• Undesirable color variations as the lamps aged and sodium migrated through the quartz—“This unexpected change of color to green, pink and blue hues produced a rainbow effect in the canopy lighting, creating the perception that the lamp was faulty,” says Terry McGowan. “This effect was magnified with the indirect lighting used on the underside of the canopy to illuminate the opaque canopy cover.”
• Prolonged warm-up phase before operation began (five to eight minutes) and prolonged restrike or re-lighting phase (10-20 minutes) after interruption of power.
• Devitrification (causing the quartz to become crystalline and brittle) of the quartz. “An electrical charge built up in the starter probe when it was not producing a spark as the main arc passed between the two electrodes, contributing to quartz erosion,” says Doug Paulin. “In some instances, the arc tube would actually explode.”

These drawbacks, in combination with other factors, created the need for substantive changes in MH technology in the US and led to the “pulse start” technology.

Photo 4: Ballast components—(left to right) transformer, ignitor, and capacitor. Courtesy of Advance Transformer Co

Engineering “pulse start” beginnings
As with most inventions, changes that revolutionized MH lamps evolved from previous technology. “The Europeans had developed a metal halide lamp which operated without a starter probe within the arc tube (see Diagram 1B). This lamp had demonstrated good lumen maintenance,” explains Bill Ryan. “However, the chemistry within the arc tube differed and the ignitor used to deliver the 1200 volt pulse was insufficient for use with US lamps.”

By 1985, OSRAM Sylvania introduced a 100 watt pulse start MH lamp. A technological leap occured when higher wattage MH pulse start lamps were developed in response to specifications created by Robert (Bob) Ready, CEO, and his team at LSI Lighting. “His goal was to create a total lighting system that would address the specific needs within the petroleum service station industry and canopy environment. Bob Ready had a vision that ultimately, bottom line, saved the service station companies and owners money,” says Bill Ryan. To accomplish this, Ready gathered leading lamp manufacturers, designers, engineers and ballast manufacturers. Within this group context, Ready specified what type of systems improvements were needed (also to be described in Part Two). Though a number of improvements were made within the lamp, a giant leap in system performance was provided by ballast manufacturers.

A boost from the ballast
The ballast that has evolved within the pulse start system contains several components: the transformer (“core and coil”); the ignitor; and the capacitor (see Photo 4). “The ballast serves two functions,” explains Terry McGowan. “One function is to start the lamp under any temperature or voltage condition that would likely be expected. The second function is to regulate the light output of that lamp, as it warms up and over time, because lamps do change electrically as they age.”

One of the improvements within the ballast system was built upon past developments used to start HPS lamps. “In the 1960s, the ballast industry had created an ignitor that could deliver an electric pulse or spark of 3,000 volts in the HPS arc tube,” says Pete Perkins, VP of Product Management, Advance Transformer Company. “Advance Transformer then worked with lamp manufacturers decades later to develop a suitable ignitor with a 3,500 volt pulse needed to start the new MH lamps.

“Replacing the internal starting probe with an ignitor allowed a separation of ballast starting and operating functions. The ignitor starts the lamp, and the ballast’s ‘core and coil’ (transformer) operates the lamp, allowing for optimization of both lamp and ballast performance. With this arrangement, we were then able to lower the crest factor of the ballast (see Diagram 2), reducing the stress on the lamp electrodes and resultant tungsten migration. We were also able to lower the ballast losses, which reduced the operating temperature of the ballast and surrounding components; thus, extending ballast life.”

Graph 1

Graph 2

Graph 3

Graph 4

The graphs above depict improvements of pulse-start metal halide lamp performance over probe-start metal halide lamp performance. Courtesy of Advance Transformer Co.

Light manufacturers leap forward
The pulse start technology is now used by all major manufacturers of MH lamps. It immediately created solutions to existing problems that had reduced lumen maintenance and created barriers to lamp performance; synergistic changes followed.

The ignitor pulse created by ballast changes helped reduce tungsten blackening of the arc tube. “We were able to have a fill pressure in the arc tube three times greater than traditional metal halide lamps. This, in turn, prevented the tungsten deposition associated with shorter lamp life,” says Jim LaPointe, HID Product Group Manager, OSRAM Sylvania. The ignitor pulse also reduced the length of time needed to start and restart the lamp.

The shape of the arc tube was re-designed by some of the manufacturers. “We shape the arc tube to the curvature of the arc for thermal management using an isothermal (uniform temperature) design for optimal operation,” says Jerry Flauto, Senior Products Specialist, GE Lighting Institute. “Also, the reduction in size of the pinch seals serves to reduce heat loss in the arc tube.”

Precision production of the arc tube also helped to ensure optimal functioning with components within the lamp. “For example, if the electrodes are not placed into the arc tube at the precise point, then you end up with variations in the operating current of the arc tube that will affect the performance and temperature,” adds Jim LaPointe. For this reason, many of the lamp manufacturers point to vertical integration (ownership of all component producers) as an advantage in maintaining quality control of components of the lamp.

Photo 5: The family of 175 watt PulseArc™ lamps (clockwise from top): an ED (elliptical dimpled) 23.5 lamp with a mogul (large) base, coated to reduce glare; a clear ED 23.5 with a mogul base; and the smaller coated BD17 lamp with a medium base. Courtesy of GE Lighting

Photo 6: A clear 400 watt Metal Arc® pulse start lamp (left) and coated 320 watt Metal Arc® pulse start lamp. Courtesy of OSRAM Sylvania Inc

Photo 7: Two examples of the ICETRON®, an inductively coupled electrodeless fluorescent lamp, rated with a lamp life of 100,000 hours. Courtesy of OSRAM Sylvania Inc.

Precision production also affected color stability. “By reducing temperature differences within the arc tube, color shift was reduced and lumen output was increased because chemicals remained in the arc stream,” says Pete Perkins.

The chemical composition within lamps also changed. “With the addition of the element, cesium, we gained improvements in illumination and suppressed undesirable chemical reactions,” says Bill Ryan. “We also improved the way we ‘dosed’ lamps; the salts are of the highest purity you can imagine.”

One of the changes Ready had requested was a vertical orientation (“base up”), as opposed to the traditional horizontal orientation, in which the lamp would operate. This allowed the light from the lamp to be displayed as a vertical surface below the bottom of the canopy within an optic lens, adding to its visibility to motorists from a distance. The vertical orientation also made changing lamps from the ground possible. This saved on maintenance manpower and cost. Furthermore, changing the orientation of the lamp improved arc performance by eliminating the bowing (“upside down smile”) of the arc that would occur as the result of gravity and convection (heat transfer by circulation) currents formed when heat is generated within the arc tube.

Ready also requested that the lamp’s outer envelope be reduced in size (see Photo 5). Most manufacturers re-engineered lamps to substantially reduce the size of the outer envelope of the lamp, literally lopping off inches from both the diameter and length.

In short, the recent technological leap forward in MH technology has been phenomenal, resulting in more lumens per watt, better lumen maintenance, greater color stability and longer life (see comparisons in Graphs 1-4.)

Photo 8: Pulse start metal halide lamps used in a Mobil canopy. Courtesy of OSRAM Sylvania Inc

The immediate future for canopy lighting
The Light Research Center at Rensselaer Polytechnic Institute in Troy, New York, is the world’s largest lighting research facility within a university setting. “We interact with industry through partners that sponsor the program,” says Professor Russell Leslie, AIA, FIES, LC. “Many manufacturers have inventions and come to us for guidance. A lighting designer, an engineer, a vision scientist and a physicist may sit down with them to determine the applications.

“We study human response to light, safety and health, and help define what products are needed. Government officials come to us to help guide them on policy and codes. The utilities come to us. We also conduct product testing. In our Lighting Futures newsletter, funded by the EPA, we look at what’s coming down the line to prepare people, who are trying to anticipate changes happening in the future.

“Relative to canopy lighting, the metal halide lamp represents the near term future. It already has good color, though some advances are anticipated in color stability as well as efficiency. We may see some advances in both the ballast and arc tube in the lamp design and how they operate together and integrate their functions.”

The future is now
Some of the lighting sources available today are not currently used as canopy lighting in the US because the desired canopy lighting levels are higher here than in other countries. What separates these products from the marketplace is that magic combination of engineering genius, technology and time.

We end Part One with mention of ceramic MH lamps, the electrodeless fluorescent lamps and light-emitting polymers (LEPs) as examples of technologies that may yet shine on canopies in the US in future decades. Part Two will also explore examples of lighting technologies, such as LEDs and fiber optics.

Many canopies today utilize 320 watt to 400 watt pulse start MH lamps that can produce as many as 36,000 to 44,000 lumens respectively (an initial efficacy of 110 lumens per watt) and a lamp life of 20,000 to 30,000 hours. In contrast, the highest wattage ceramic MH lamps produce 15,000 lumens (an initial efficacy of 100 lumens per watt) and a lamp life of 9,000 to 15,000 hours. The electrodeless fluorescent lamps are currently limited to 150 watts with the highest lumen output around 12,000 lumens (an efficacy of 80 lumens per watt), but with a whopping 100,000 hours lamp life!

“The lighting industry has been looking for a step change, and we believe that ceramic metal halide technology offers a key,” says Bill Ryan. “Ceramic metal halide lamps are made from aluminum oxide, which is: 1) impervious to sodium and, thus, prevents its migration out of the arc tube; and 2) translucent so that light can pass through it. The use of ceramics increases the efficiency of the salts in the arc tube at higher temperatures. Also, ceramics allow for more precise control over the process of forming the arc tube. By changing the composition of the metals—the dysprosium, thallium—we now have color rendition that has improved from 65 to 85 on the Color Rendition Index.”

Electrodeless fluorescent lamps (see Photo 7) are currently used for canopy lighting in Europe, though initial system cost still remains relatively high. “Our inductively coupled electrodeless fluorescent lamp is used in applications that are difficult to maintain and difficult to reach,” says Jim LaPointe. “It’s nice to have a lamp that you don’t have to worry about for 15 years. And, by September 2000, we will offer an ICETRON® with a 20,000 lumen output.”

In a decade, the canopy lighting alternatives could multiply. “If we stretch our research and development time frame to 10 years, LEPs or light emitting polymers may allow an entire canopy to glow or emit light uniformly at the level that you want,” suggests Professor Leslie. “This technology is defined and discussed in the last issue of Lighting Futures, which can now be accessed through the Light Research Center’s website:” www.lrc.rpi.edu/Futures/LF-LEDs/index.html.

From the lamp to the luminaire
The technological gains from lamp technology are only one part of the canopy lighting revolution. In PE&T’s next issue, Part Two will highlight this progress in luminaire technology—developments that make sense and cents for service station owners.

Our Thanks

Our thanks to the following people who contributed generously of their time and knowledge to make this article possible:

Nancy Clanton, PE, IALD¹, LC²
Clanton & Associates; Boulder, CO
Chairperson, IESNA³
Outdoor Environmental Committee
Board of Directors, International
Dark-Sky Association
Board of Directors, IALD¹

Jerry Flauto Senior Products Specialist
General Electric Lighting Institute
Cleveland, OH
Member, IESNA³ Progress Committee

Wayne Hendersen
Petroleum Historian
Petroleum Collectibles Monthly
LaGrange, OH

Jim LaPointe
HID Product Group Manager
OSRAM Sylvania of North America
Beverly, MA

Professor Russell Leslie, AIA, FIES⁴, LC²
Associate Director, Light Research Center
Rensselaer Polytechnic Institute
Troy, NY

Terry McGowan, FIES4, LC²
Lighting Consultant
Lighting Ideas, Inc.
Cleveland, OH [formerly Manager, General Electric Lighting Institute]

Douglas Paulin, LC²
Product Manager
Ruud Lighting, a Division of ADLT
Racine, WI
Vice President-Design & Applications
1998-2000, IESNA³

Pete Perkins
Vice President of Product Management
Advance Transformer Co.
Rosemont, IL

Bob Ponzini
HID Applications Manager
OSRAM Sylvania of North American.
Beverly, MA

Bill Ryan Group Product Manager for HID
Phillips Lighting of North America
Somerset, NJ

¹International Assn of Lighting Designers
²Lighting Certified
³Illumination Engineering Society of North America
⁴Fellow, Illuminating Engineering Society

Glossar

Coming to (lighting) terms - a glossary To appreciate the advances in lamp technology, several terms are defined:

ballast:
a device used with an electric-discharge lamp to provide the necessary power conditions (voltage, current and waveform) for starting and operating.

¹color rendering index (CRI):
a measure of the degree of color appearance shift that objects undergo when illuminated by the light source as compared with those same objects when illuminated by a reference source of comparable color temperature (or how accurately colors look compared with sunlight).

color stability:
how well a lamp maintains its color over time. color temperature—“warmth” or “coolness” of color.

crest factor:
the ratio of the height to the width of the sine wave, which represents the wave form of alternating electrical current as it alternates between 120 volts and a minus 120 volts 60 times per second (see Diagram 2).

efficacy:
the light output of the lamp (not including the effect of the fixture) measured in lumens per watt.

envelope:
outer glass that surrounds and encloses the arc tube.

lamp:
generic term for an electrical source of light.

lamp life:
a statistical figure of the length of time it takes for half of a quantity of lamps to burn out.

¹lumen:
the Systeme International (SI) unit of luminous flux (the totality of the light leaving the light source).

lumen maintenance factor:
the ratio of average illuminance in service to initial illuminance.

¹luminaire:
a complete lighting unit consisting of a lamp and ballasting together with the parts designed to distribute the light, to position and protect the lamps and to connect the lamps to the power supply.

Information drawn from interviews and ¹IESNA Lighting Ready Reference (RR-96 Third Edition); 1996.

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