Feb 8th 2017 | Posted in Energy by Kristin Gordon

Did viewers notice if the Patriots and the Falcons were well-lit when they took the field Feb. 5? Houston boasted that the field at NRG Stadium was illuminated exclusively by 65,000 light-emitting diode (LED) lights for Super Bowl LI. The stadium’s media relations team shared that the new lighting system uses 337 kilowatts when at full power, about 60 percent less energy than the previous system did. They even added that these lights can be dimmed for events that don’t require them at full capacity, allowing for further energy savings.

Saving money on lights can really add up, especially when it means keeping them on from dusk until dawn for drivers. Street lights play an important role in the safety and security of roadways and public places. Street lighting is used on highways and streets in order to illuminate the driving route, which makes it much easier to see if there is debris on the road, water, ice or a crossing pedestrian or animal. There are several different types of street lights that have been used over the years to expand a driver’s range of visibility.

Incandescent– These are standard electric light bulbs that were introduced more than 125 years ago by Thomas Edison. They have the lowest initial cost, good color rendering and are notoriously inefficient . They typically have short life spans and more than ninety percent of the energy used by an incandescent light bulb escapes as heat, with less than 10 percent producing light.

High pressure sodium lamp (HPS)– This is the most commonly used street light throughout the world. It produces light by running electricity through a mixture of gases, which produces light. The lamp itself is preferred because it requires little maintenance. These lamps are fairly efficient. They take a while to turn on completely and produce a yellow-orange glow.

Low pressure sodium (LPS)– This light works similarly to the HPS light. Instead of producing white light (all the colors of the rainbow), LPS lamps produce almost exclusively yellow light. While this light is fairly efficient, it takes several minutes for the bulb to turn on. The light is very yellow-orange. This yellow light makes objects it is illuminating look a different color or gray.

Fluorescent– The typical glow is strong in ultraviolet but weak in visible light. Standard fluorescent lamps for street lighting are large and produce a diffused non-directional light. They are also susceptible to low voltage failure, prone to breakage of glass parts and contain harmful mercury.

Mercury vapor– These omit a bluish-green light.  A significant portion of their light output is ultraviolet and they “depreciate”; that is, they get steadily dimmer and dimmer with age while using the same amount of energy.

Metal halide– These lamps are commonly used in streetlights, parking lot lights and stadium lights. They are very bright and contribute to a lot of light pollution. They are fairly efficient. They produce very white light and have good color rendition, meaning that objects under these lights look their true color.

Induction– Induction-based fixtures use radio frequency or microwaves to create induced electrical fields, which in turn excite gases to produce light. Induction lights have a rapid start-up and work at peak efficiency with minimal warm-up time, much like LED technology. The initial cost barriers and the rapidly evolving nature of LED technology have led to limited adoption of induction-based roadway lighting systems. Another limitation of Induction lighting is that it has limited directionality when compared to LEDs. The life of induction light is negatively affected by heat and they also contain lead.

Solar– This is a lighting system composed of an LED lamp, solar panels, battery, charge controller and there may also be an inverter. The lamp operates on electricity from batteries charged through the use of a solar photovoltaic panel.

LED– This light technology has developed rapidly in recent years and these bulbs are now being integrated into outdoor lighting solutions. While the energy savings are significant, LEDs produce a lot of blue light, too much of which studies have shown can have negative effects on human health and wildlife due to glare.

Falling LED prices, various initiatives and projects by government to make cities smarter and reducing carbon emissions are some of the key reasons why street lighting is improving and growing. Cities, counties and states are looking at several factors when upgrading their old lighting systems such as low energy consumption, long predictable life, accurate color rendering, low electrical losses, light pollution and environmental-friendly street-lighting systems such as solar street lights. Such initiatives further help in the growth of the global street-lighting market.

In January, the Michigan Department of Transportation (MDOT) and Lt. Gov. Brian Calley announced a public-private partnership that has led to the installation of LED lights along Metro Detroit freeways. Nearly 13,000 new LED lights replaced older high pressure sodium, metal halide and mercury vapor mixtures. The lights are expected to last longer, shine brighter and make installation easier. The lights will save $2 million annually in operating costs as part of a 15-year agreement between MDOT and agencies that operate freeway lighting around Metro Detroit.

Honolulu, Hawaii Mayor Kirk Caldwell began a pilot project to replace 400 street lights using federal funding. If the savings are successful, the city and county will replace 52,000 city-owned street lights with LED fixtures over a four-year span through a public-private partnership. The city streetlights consume about $6 million in electricity annually. Switching to LED is projected to save around $3 million in energy costs per year.  Neighboring islands also plan to replace their streetlights with these energy-saving bulbs.

In Las Cruces, N.M., a project to replace about 2,700 light fixtures on major streets is about to wrap up for a local electric company that was hired by the city. From high-pressure sodium light bulbs to LED fixtures, the lighting along Las Cruces’ more traveled streets is changing from amber to white. Through gross receipts taxes, city government is spending $1.5 million to upgrade city street lights to energy-saving fixtures that are expected to lead to lower electricity bills.

Since LED street lights have an expected life of 15 years, the city can anticipate a cumulative net savings of $9.5 million over the life of the installations based on a conservative electricity escalation rate of 3 percent.

City officials believe the $1.5 million investment for the newer, more efficient street lights could be paid back in about 2 1/2 years through reduced electric bills and lower maintenance costs. These new lights are warrantied for 10 years, and if they fail before then, city officials will send them back to the manufacturer for a replacement.

Another way LED lights are shinning brightly on asphalt is through a safety feature on North Texas freeways. According to the Texas Department of Transportation (TxDOT), in 2016 there were more than 1,000 wrong-way crashes on Texas roads resulting in 65 deaths. High-tech signs, located on 24 Tarrant County ramps, are flashing LED lights triggered by sensors that can spot cars going the wrong way. The sensors also send a message to a TxDOT command center. From that command center, TxDOT can post messages on light-up message boards warning other drivers that there’s a car on the highway going the wrong way. TxDOT will also alert police.


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