Why Use LED Lights at Martinsville?

Since Martinsville announced this week they will install a LED lighting system, I thought it would be fun to take a look at LED lights and why Martinsville chose them over traditional lighting. Martinsville will be the first major motorsports facility to install a LED system.

Illumenating Tracks

Lighting racetracks is a relatively new thing. In 1998, Musco Lighting revolutionized NASCAR by enabling night racing at Daytona. Racetracks pose special challenges for lighting, especially when they are large like Daytona. Lighting a football field is one thing, but lighting a 2.5-mile racetrack uniformly is a significantly greater challenge.

It’s not just a matter of throwing light on the track: the lights have to enable the drivers and spectators to see, while minimizing glare and meeting the technical demands of television broadcasting. To light the Superstretch, Musco had to develop a lamp that was more than 100 times bright than the high beam headlights of a passenger car at the time.

We measure brightness in lumens, a unit weighted to describe how the human eye perceives light brightness. (The weighting is necessary because 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 (which is often correlated to the bulb’s quality) and whether it’s clear or frosted.

Musco’s system for Daytona 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. Not only is it huge (I estimate 18,000 lumens given the numbers Daytona provided), it’s enclosed by a parabolic metal shell polished to a mirror-like finish to focus light onto the track.

Martinsville, at a half-mile, is far from the challenge of Daytona, but because it is one of the few NASCAR tracks without lighting, the folks there have a unique opportunity to avail themselves of all the technological advances that have been made in the last 18 years.

And there have been a lot of them!

A Brief History of Light

In the beginning, God said…

Okay, maybe we’ll be a little briefer than that.

Contrary to what you were probably told in school, Thomas Alva Edison did not invent the incandescent light bulb. As I’ve harped on many times, rarely does one person “invent” something.

The battery was invented in the the early 1800s. We already knew that wires made of metal or carbon would glow when heated, but when Humphry Davy hooked up his new battery to a piece of carbon, the carbon became so hot that it glowed. The word incandescent actually means “emitting light as a result of being heated.” We call whatever material we are making glow the ‘filament’. That’s the part that breaks and forces you to buy a new light bulb.

There were a lot of challenges to harnessing this glow so it would be useful. Heating destroyed the filament because it basically evaporated atoms away. The earliest filaments were more like flashbulbs than light bulbs.

A big step forward was realizing that if you put the filament in a container and removed as much air as possible, the filament would last much longer because there are fewer air molecules around to degrade the filament. As scientists developed better and better vacuum pumps, filaments lasted longer. Platinum turned out to be a good choice for a filament in terms of longevity, but platinum is very expensive and could never be commercially useful.

In 1874, two Canadians (Woodward and Evans) filed a patent for a light bulb made of carbon rods held between electrodes in glass cylinders filled with nitrogen. They were unable to commercialize their light bulb and ended up selling their patent to Edison.

Between 1878 and 1880, Edison had his research lab test over 3,000 materials to see which ones would make the best filaments. In 1880, Edison put the first commercially viable light bulb on the market. Edison’s contribution was making the incandescent light bulb long lasting and affordable enough to use in the average house.

What’s Wrong with Incandescent Light Bulbs?

Incandescent Bulbs have many attractive qualities. They are cheap; readily available in myriad shapes, sizes and wattages; easy to install; and easy to dispose of. So why are most governments around the world banning them?

Because running an incandescent light bulb is like throwing money out the window. Only around 3% of the electricity that goes into the bulb comes out in the form of light. The rest is turned into heat.

The best measure of efficiency for light bulbs is how many lumens (brightness) you get per Watt of power you put into the bulb. Take a look at the chart below, which compares some common types of lighting.

Incandescents are the least efficient light, 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%.

If you’re paying attention, you’ll note that metal halide bulbs can be even more efficient than LEDs — and that metal halide fixtures are used at Daytona and all the other race tracks.

Efficiency isn’t the only consideration. As is typical in engineering problems, you’re trying to balance a whole bunch of different factors.

Lifetime and Light Output

Let’s define lifetime as how long before the light breaks and doesn’t give off any light.

1. The average lifetime of an incandescent bulb is 1000 hours and the bulb maintains the same level of brightness throughout all but the very, 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 may have a lifetime around 15,000 hours; however, 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. This means they have to be replaced significantly before the end of their lifetime.

Cost

As you probably know if you’ve been to the hardware store to buy light bulbs, LED bulbs are significantly more expensive (sometimes 5–10 times more expensive than the incandescent lamps); however, if the bulb lasts 25 times longer and costs less to power, you end up saving money by using the more expensive bulb. 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

There isn’t much we can do to improve the efficiency of incandescent bulbs, but some of the other forms of lighting (especially LED) 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.

Ease of Use

Yes, you turn on a light and it works. But metal halides take awhile to come on. LED lights are pretty immediately on/off. Because LEDs are basically computer chips, the manufacturers can build diagnostics into the lights and the lights can provide feedback to the users on how they’re doing. That may not be important to you if it’s the bulb in your desk lamp, but when it’s a structure a couple dozen feet above the track, you’d sort of like some advance notice, right?

So Why Didn’t Everyone Just Use LED lights to Light Their Tracks?

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

What’s a “LED” anyway?

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

When made of specific semiconductors, passing a current through the diode causes the diode to emit light through a process called electroluminescence. 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. (You need infrared goggles to see infrared light.) Plus, the amount of light emitted was pretty miniscule.

As we started developing new types of semiconductors, we discovered some materials have much stronger electroluminescence than others. In the 1950’s, scientists looked at LEDs as a possible infrared (i.e. light-based) communication mechanism. It wasn’t until the 1960s that scientists started trying to develop LEDs and optimize their properties.

The first visible light LED was created in 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…

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. During that time, the brightness of the existing red and red-orange LEDs were improved, mostly because we started to understand the process of electroluminescence in different types of semiconductor materials. Scientists used that understanding to create brand new semiconductor materials that would produce different color light. Green LEDs followed.

Have you noticed that we’re discovering LED colors according to the rainbow? ROYGBIV, right? That is because the colors we see correspond to different wavelengths. The wavelengths get smaller as we go down the rainbow. Red light is actually bigger than blue light.

The semiconductors we knew about were naturally producing light in the larger wavelengths. We had to manipulate the materials to get yellow, then green. It was surprisingly not until 1994 that blue LEDs bright enough to use for anything were created. It was such a monumental advance that the scientists who made the seminal breakthrough were awarded the Nobel prize in 2014. (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 do we care about color when we’re lighting a racetrack? Because you can’t make white without colors.

The Challenge of White LEDs

There are three ways to make white light using LEDs:

• Color mixing: combine red, blue and green LEDs
• Phosphor conversion: Use different phosphors to absorb some of the LED light and re-emit it in a different color
• Hybrid: uses a combination of the first two.

The graphic below is from the Department of Energy. I was going to redraw it, but they did such a good job…

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. The difference is that, in the first case, you are looking at reflected light and 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.

Phosphors and Blue Light

The second way to get white light from a LED is to use a blue LED and a yellow phosphor. Isaac Newton figures out way back when that you can make white light using blue and yellow light. (Surprise: know how you make yellow light? You mix red and green.)

A phosphor converts some of the blue light to yellow, the lights combine and you get white. You’re actually doing color mixing just like above, but you’re doing it inside the light instead of with three separate lights. These lights can be changed in color a little, but we’re talking about going from a bluish-white light to warmer, reddish-white light.

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 to be installed at Martinsville (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 provided is equivalent to 144 60-W light bulbs (which would use 8625W of power!). Compare the output of the LEDs at 115,000 lumens to the 18,000 lumens provided by the metal halide lights that were installed at Daytona! The 750 bulbs at Martinsville will provide 8.62 million lumens.

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.

Isn’t Going with LEDs Just a Politically Correct Thing?

LED systems are more expensive than the traditional metal halide lighting systems. Martinsville’s system will cost about $5M. That seems like a lot, especially without the guarantee of a night race.

ISC (which owns Martinsville Speedway) is a business. They aren’t going to make a choice that is going to cost them a ton of money for a few brownie points or a little extra publicity. Most people are excited Martinsville is getting lights and could give a hoot less that they’re LEDs. ISC chose this system because it represents the best long-term investment in their property. They’re getting a low-maintenance, state-of-the-art lighting system that will last a long time, and be much cheaper to run than a metal-halide system.

NOTE: Musco, who pioneered racetrack lighting, also offers LED systems. I didn’t want anyone read this article and think that Musco was the old technology and Eaton the new.

Originally published at Building Speed.