Why Use LED Lights at Martinsville?

This Wednesday is the first night race under the LEDs at Martinsville. Let’s look at their system and see why they decided to become the first major motorsports facility with a LED lighting.

Illumenating Tracks

In 1998, Musco Lighting revolutionized NASCAR by enabling night racing at Daytona. Racetracks are a huge challenge when it comes to lighting because of safety considerations.

Lights must allow drivers and spectators to see and meet the technical demands of television broadcasting, all while minimizing glare.  To light Daytona’s Superstretch, Musco had to develop a lamp that was more than 100 times brighter than the high-beam headlights of a passenger car at the time.

Lumens are a unit that describes how the human eye perceives light brightness. Our eyes don’t detect all wavelengths of light equally. To give you an idea of how big a lumen is, a typical 60-W incandescent light bulb provides around 800 lumens of brightness. I say “around” because the amount of light depends on the brand, the quality of the bulb and whether it’s clear or frosted.

The front of a non-LED lightbulb box: The important number is the lumens, not the wattage.

Musco’s Daytona lighting system used 1932 metal-halide light fixtures and 150 miles of wire to provide 350 million lumens of light. The system used 3.5 million watts of power per hour.

To give you an idea of what they were dealing with, take a look at the giant light bulb in the picture below. A parabolic metal shell polished to a mirror-like finish envelopes a huge (I estimate 18,000 lumens or so) light. The mirror focused light onto the track so none of those 18,000 lumens are wasted.

The size of the metal-halide lights at Daytona

Martinsville, at a half-mile, is far from the challenge of Daytona, but because it is one of the few NASCAR tracks without lighting, it presents a unique opportunity to utilize all the technological advances made in the last 18 years.

And there have been a lot of them!

Incandescent Light

Incandescent means “emitting light as a result of being heated.” The filament — the material that glows — is the part that breaks and forces you to replace it. You can see from the chart below that it took a long time to develop a commercially viable incandescent light bulb.

A chart showing a brief history of the light bulb

Incandescent bulbs are cheap; readily available in myriad shapes, sizes and wattages; easy to install; and easy to dispose of.

But they are horrendously inefficient.

Only around 3% of the electricity that goes into an incandescent light bulb comes out in the form of light. The rest turns into heat.

Efficiency: Metal Halide Lights Win

The best measure of efficiency is how many lumens (brightness) you get per watt of power. The chart below compares common lighting types

A chart showing the efficiency of different types of lighting

Incandescents are the least efficient lights, getting around 14 lumens per watt. Compare that to White LED bulbs, which range from 40 to 100 lumens for each watt of power. That’s an efficiency improvement of anywhere from 100% to 680%.

Metal halide bulbs can be even more efficient than LEDs. At the time Daytona — and most of the other race tracks — were installing lighting, metal halides were the best possible choices.

Why LEDs?

Metal halide lights offer many attractive features, but LEDs have become a better and better choice over time.

Lifetime and Light Output

  1. The average lifetime of an incandescent bulb is 1000 hours. The bulb maintains the same level of brightness throughout all but the very last moments of its lifetime.
  2. LED lights last around 25,000 hours and maintain the same brightness through that very long lifetime.
  3. Metal Halide lamps have a lifetime around 15,000 hours, but their  brightness drops off significantly as they age. Halfway or two-third through their lifetime, they are likely to be only 50% as bright as they were when first installed. Metal halide lamps have to be replaced more frequently than LED lamps.

Cost

LED bulbs are significantly more expensive than other types of bulbs, but if the bulb lasts 25 times longer and costs less to power, you save money with LEDs.

LED lights have a higher initial cost of installation, but lower costs in the long run. You also save the cost of having to hire people and bucket trucks to change light bulbs.

Evolution

LED lights are still making great strides in efficiency and features. Once you install a type of lighting at a track, it’s not like you can just switch out the bulbs to change. Don’t expect any big changes in incandescent light bulbs (or metal halide) anytime soon.

Ease of Use

Metal halides take awhile to come on, whereas LED lights are pretty immediately on/off. Because LEDs are basically computer chips, manufacturers build diagnostics into the lights, so the lights provide feedback. That may not be important if we’re talking about the bulb in your desk lamp, but when it’s in a structure a couple dozen feet above the track, you’d sort of like some advance notice that it’s got a problem.

What’s a “LED”?

Because white LED lights bright enough to light a racetrack are a very, very recent invention.

LED stands for Light-Emitting Diode: a tiny (< 1 mm2) electronic device that converts electricity to light. A diode is a device in which electricity flows differently when it goes in one direction than in the other.

Some semiconductors can emit light through a process called electroluminescence when a current passes through a diode made of that material. Electroluminescence was discovered in 1907 and the first LED made in 1927 in Russia.

These devices weren’t very useful. They emitted light in the infrared — a wavelength of light larger than our eyes detect and not much of it. The first visible-light LED wasn’t created until 1962. It was red, very weak and very expensive. You had to use special lenses to make the light bright enough to see.  It was really only useful as indicators, then as seven-segment packages that were used for…

One of the first commercial uses of red LEDs was in calculators

TI used a special plastic lens to make the numbers readable, but you still couldn’t see the darn display if it was at all bright.

It took ten more years to create yellow LEDs, and even more years before green LEDs followed. It was not until 1994 that blue LEDs bright enough to use for anything were created. The Nobel prize in 2014 went to the scientists who created blue LEDs. (The guy who figured out red LEDs, by the way, was not recognized by the Nobel committee. And he was also not happy about it.

Why were blue LEDs so monumental? Because you can’t make white light without colors.

The Challenge of White LEDs

There are three ways to make white light using LEDs. The graphic below is from the Department of Energy and explains them. We’re interested in the middle one: color mixing

A graphic showing how white light can be created using different methods

Color Mixing

If you mix red, green and blue paint, you get black; however, if you mix red, green and blue light, you get white light. In the first case, you are looking at reflected light. The different pigments absorb all the light, so you see dark. In the second case, you are looking directly at the light, so you see white.

Most LED displays work on this principle. Each ‘dot of light’ is made up of separate green, red and blue LEDs. This is the type of display you’ll find at Texas Motor Speedway, Charlotte Motor Speedway and the Cowboys Stadium. Changing the relative brightnesses of the three LEDs changes the color you see.

Martinsville’s System

Martinsville is installing the Eaton Ephesus Stadium Pro 750 Series, which has been installed at the University of Phoenix Stadium in Arizona and Williams Field at Duke University. Each of the Eaton lights (shown below) contains about 144 individual LEDs. To give you an idea of the scale, the diameter of the light is about 20.5 inches and it weighs about 55 lbs. The press release says they will have 750 lights in and outside of the track.

Each light puts out 115,000 lumens for 1000 W. The amount of light is equivalent to 144 60-W light bulbs (which would use 8625 W of power!).

Compare the output of the LEDs at 115,000 lumens to the 18,000 lumens provided by the metal halide lights at Daytona! The 750 bulbs at Martinsville will provide 8,620,000 lumens.

A picture of the type of lights being used in Martinsville

Special plastic lenses called NEMA lenses perform two simultaneous functions: they help focus and condition the light, plus they seal the lights to protect them from the environment. These lights are also really smart: they provide real-time feedback on their status, so if there’s a problem, the track will know precisely what it is pretty quickly.

NOTE: This article includes material from a blog originally published in October, 2016. It was updated and cleaned up in 2020.


Also published on Medium.

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