Tennis Lighting: The Life and Slow Death of Metal Halide
By Jonathan Bailin, Ph.D., USPTA
Tennis Coaching & Sport Science
For over 50 years, most tennis courts around the world have been lighted with Metal Halide (MH) fixtures, yet few who use them understand their unique qualities. They may seem to last endlessly, but that’s far from the truth. More importantly, the long reign of MH may be coming to an end in favor of new, more efficient, “green” technology.
First, though, a little background. Metal Halide technology is a member of a family of High Intensity Discharge (HID) lighting systems, which includes street and shopping center lighting. In HID lighting, electricity heats a metal for several minutes until it vaporizes inside a bulb to give off light, and plenty of heat, which is energy lost. In this case over 6,000 degrees Fahrenheit, which is a lot of lost energy!
MH bulbs are housed inside a fixture, or “can,” which has reflectors that focus the light from the back and sides of the bulb downward and outward. Most current MH light is not direct light; it is reflected from the back and sides of the bulb. This makes a difference in its actual and perceived intensity compared to the direct LED lighting you see in office and home lamps.
For a shopping center or highway, the HID metal to be heated is sodium, which comes in two types, Low Pressure Sodium (LPS) or High Pressure Sodium (HPS). Each gives off a “champagne” or yellowish color. LPS and HPS are great for black and white security cameras but not very pleasant for the human eye as it washes out color. This makes people a bit uncomfortable and they do not want to loiter too long in this light. On the other hand, LPS/HPS is very cheap and long-lasting, so it is great for parking lots, alleys, and highways.
For sports, the metal of choice inside the bulb is mercury. Older players might remember the name “mercury vapor.” Since mercury gave off a bluish light, trace amounts of other metals (or halides) were added to help stimulate our eye’s sense of color, so Metal Halide was born. MH is also much better for television, so prime-time sports went “cha-ching”!
Downside of Metal Halide
But, there are some negatives to MH. First, experts tell us MH bulbs lose 5 to 10 percent of their illumination per year. This is according to Ricc Bieber of Bieber Lighting Consultants and Greg Moreland of Moreland Lighting LLC. Most lamps we know are either fully on performing near maximum, off, or burned out. But MH is different in that it degrades quickly then levels off for years. Also, most lamps familiar to the public do not require warm up. That 6,000 degrees takes a while!
Why do the experts say 5 to 10 percent degradation? Because a hot MH bulb attracts dust and particulates, like the warm computer at your desk, and some environments have more particulates in the air than others. Either way, it’s a significant drop in performance.
I recently conducted an experiment with Bieber Lighting and Moreland Lighting and confirmed this and more. We compared the illumination of old 1,000-watt MH bulbs behind dirty lenses, clean lenses, and new 1,000-watt MH bulbs, all with two types of light meters.
Our results showed that just cleaning the lenses can result in up to 24% more light, and replacing the old bulbs created up to another 40% more light to the court. Plus, it’s smart to do both at once. My vendor charges $105 for the trip, $95 per lamp (for six or more per court), which includes labor.
At that time, all capacitors should be checked and changed if needed and noisy transformers replaced. For an eight-light court, I would plan to budget $900 to clean the lenses and replace the bulbs from my vendor.
MH performance drops then flat-lines at what lighting experts call “mean lumens,” which is around 40 percent of new bulb capacity. This is despite the fact that it often still ignites and might “appear” to work for many years after that. Here are our MH lighting tips:
1) Clean lenses and properly operating MH bulbs should be uncomfortable to look at directly.
2) Bulbs and lenses can be cleaned, but never the reflectors.
3) Budget for MH bulb replacement and lens cleaning at the same time, between three to five years max.
Life After Metal Halide
MH has served us well for a long time, but it may be time for some changes. Let’s start with the hard costs of MH. We have to make some assumptions, but this analysis will give you a point of comparison between an MH court and its most likely successor, LED technology.
Let’s assume a typical tennis court with eight 1,000-watt MH fixtures, or 8,000 total watts. That’s like eight hair dryers going full blast. A busy outdoor facility might run them an average of four hours a night (an indoor club obviously much more) and 180 nights a year (some climates more, some less).
In my city, a kilowatt-hour of electricity costs about 15 cents, times eight fixtures, or $1.20 per hour to light one court. Multiply by four hours and you get $4.80 for the night, times 180 nights a year is $864 in electricity costs to light one court. For seven years, then, electricity cost is $6,048.
As mentioned earlier, plan on $900 per court for MH maintenance. (Individual bulbs may burn out sooner, but this is a reasonable average vendor cost to maintain appropriate light levels.) Over a seven-year period, you should replace all eight bulbs twice near the beginning and end of this period, or $1,800. So we have $1,800 in maintenance plus $6,048 of electricity over seven years, for a total operating cost of $7,848 per court.
What Can We Expect Next?
Instead of a bulb that loses enormous amounts of energy to heat and sends light in all directions, the likely successor to MH is based on a light-emitting diode, or LED. You know them from the screens in your TV, phone, and computer. So, why hasn’t LED technology jumped into sports as quickly?
Even the major lighting companies have struggled trying to push enough electricity into the light emitter for sports. But unlike the heat in your computer, the heat for a sports light must be dissipated passively, without a fan.
It’s been a tricky problem but there are also obvious and huge incentives to get it right. Direct light is much more efficient; over 50 percent of MH light is reflected and tends to spill where it is not wanted. LED light can be easily directed to where it’s needed most. Because this single light source is only 4 inches wide, the chances of significant glare are extremely low compared to the 24-inch tube and reflectors used in MH.
In the new LED sports lamps, the light emitter is encased behind 3 inches of shatterproof, solid glass without an air gap. The manufacturer calls it “explosion proof.”
Since there is no air in the LEDs, there is no air pollution, dust, or condensation to block its light over time, like in MH. The clear glass lens and the spokes of LED fixtures passively draw heat away.
LED technology lends itself to an open architecture of customized mounting design choices. This customization also favors American, medium-sized companies that are able to quickly adapt to end-user needs. These companies could use American raw materials, employees, and new factories serving a large new market. Investment, anyone?
Savings With LED
The best innovation, though, may be the savings. LED technology is an impressive environmental alternative to MH power consumption because there is very little wasted electricity.
To give you more than 1,000 watts of equivalent light with better distribution, you would need to change each MH can and pole arm to a fixture for your court that holds one or two LED fixtures. Let’s assume two for now. (Right now, we don’t know if one or two LED fixtures will be equivalent to one MH 1,000-watt fixture. One complication is that the two light sources cannot be compared with a standard light meter.)
The double lamp LED fixtures pictured on this page, for instance, use only 300 watts, so with 16 LED’s per court (2,400 watts vs. 8,000 watts), there’s 70 percent savings, or $5,494, in just electricity over seven years. That’s very “green” news, and there’s more.
Because the LED emitter is encased in shatterproof glass, mounted to a heavy-gauge aluminum base, the parts/bulbs are unconditionally, 100 percent guaranteed for five years, but the expected life is 10 years for the LED chip and the housing is guaranteed for 20 years. (That’s why the manufacturer advises a conservative, budgeting choice of seven years maintenance-free.)
So, we have another $1,800 saved in maintenance. Add that to the $5,494 saved in electricity, and you have a total of $7,294 in savings per court over seven years. Pretty impressive.
Again, unlike an MH “can,” the LED lamp stays room temperature, saving on air-conditioning for indoor use. It won’t break or explode, won’t attract dust or condensation, is instant on/off, does not degrade in performance, can be placed on a motion sensor or a dimmer for mood lighting a party, and can even be remotely controlled from a smart phone!
LED fixtures are designed so that any licensed electrician can do the retrofit job. To remove the eight old MH arms/cans and install the new LEDs on eight poles, in parts and labor, is around $15,000, so over seven years about 50 percent of those costs are returned, at current electric rates. Most general contractors will agree that‘s pretty impressive for any construction upgrade.
What if only one LED fixture is needed to replace an MH can? Can solar panels run LEDs? Stay tuned for more on this impressive and innovative green technology in sports lighting.
Jonathan Bailin, Ph.D., USPTA, received his doctorate in Biomechanics/Exercise Physiology while coaching for the women’s tennis team at the University of Southern California. In 1995, he founded and moderated the first panel of physicians and specialists on the web to address the epidemic of Repetitive Strain Injuries, such as Carpal Tunnel Syndrome. A nationally noted author, speaker, and consultant on sports medicine and ergonomics topics for over 20 years, he coaches in Marina Del Rey, Calif., and can be reached at TennisDr.com or ErgonomicsDr.com.
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