LEDs: A Bright Future|
Most people are by now familiar in at least some way with LED lights. Their excellent efficiency and small size are giving them a huge boost in popularity, especially in today’s energy conscious environment. Across the nation, local governments are turning to the LED light in their quests to save money and increase the efficiency and safety of their cities and towns. With energy requirements anywhere from ½ to less than a 3rd that of traditional incandescent bulbs, LEDs are becoming an obvious alternative to the expensive and short lived lighting that is currently in use. Everything from traffic signals to street lighting to the lights used on our vehicles is being looked at in a new way thanks to the rapid advancements in LED technology that have allowed the LED to now rival traditional lamps in both brightness and light quality.
To understand why LEDs are so quickly increasing in popularity it is necessary to understand what it is that sets LEDs apart from traditional filament based lamps. To do this we must first look at how a traditional incandescent lamp creates light. The common tungsten filament light bulb has changed little since Thomas Edison’s original design. A thin tungsten filament is strung between two wire contacts and suspended within a glass bulb that is filled with inert gases like Argon which reduce the degradation of the filament as it is heated. Electrical current is passed through the filament causing the filament to heat up. As the filament heats, it emits energy in the form of light and heat. Approximately 10% of the electrical energy used by a tungsten filament or “incandescent” bulb is radiated as light, with the other 90% being radiated as heat. Since only 10% of the energy used by the incandescent is actually emitted as light, a great deal of energy is completely wasted as heat. This represents a large opportunity for improvement and it is this highly inefficient operation of the incandescent bulb that has led to efforts to develop more efficient methods of producing light. While the incandescent design has endured for over 100 years, as energy becomes more expensive and the effects on our environment of producing energy become more pronounced, more efficient ways of producing illumination have become increasingly popular.
LED stands for “Light Emitting Diode”. An LED is a small piece of semi conducting material that is impregnated with other compounds. When electrical current is passed through this “doped” semi conducting material, the electrical energy is emitted by the semi conductor as “photons” or, light. The process by which LEDs produce light is known as electroluminescence and it is a much more efficient process than that used by incandescent lamps. In the process of electroluminescence as created by LEDs, little heat is created and a larger amount of the current applied to the diode is emitted as light. Since less energy is radiated as heat and the energy is more fully emitted as light, the LED has a much greater efficiency than the incandescent lamp. This means that the same amount of light can be created by an LED as compared to an incandescent lamp with a fraction of the energy an incandescent requires.
For a comparison, consider how lamps are rated. The typical ratings for the amount of illumination a lamp can produce are expressed as “lumens” and are based on how many lumens a lamp can produce relative the amount of energy consumed. Lumens themselves represent the amount of light that hits an object at a given distance. The typical incandescent bulb is rated at approximately 15 lumens per watt and the higher efficiency halogen bulbs can only achieve at best approximately 25 lumens per watt. LEDs on the other hand even in their lowest quality versions achieve approximately 50 lumens per watt, with some manufacturers now announcing in 2010 that they have produced LEDS which produce 160 lumens per watt. When comparing these numbers it is easy to see why LEDs would be such an attractive choice for improving the energy efficiency of modern lighting.
The high efficiency which LEDs are capable of has led to a great deal of focus on the development of the LED lamp for practical use. Designs like Larson Electronicss 30 Watt LED PAR 38 Spot promise to make the traditional incandescent bulb obsolete as they continue to enter the market and consumers realize the great savings in energy costs these lamps represent. The Par 38 spot is a direct replacement for the incandescent lamps used in many applications such as floodlighting and commercial and industrial specialty roles. At only 30 watts, the lamp produces 1800 lumens of light, comparable to a 150 watt halogen lamp. Further increasing the benefits to be had from LEDs is the vastly improved longevity they have compared to incandescent bulbs. While a typical incandescent is rated at only 1000-3000 hours, LEDs are typically rated at anywhere from 20,000-50,000 hours. This means that an LED lamp can last for several years after installation before requiring replacement. A Larson Electronics Par 38 spot could be installed in a garden floodlight fixture and literally be there 10 years later while the incandescent floodlights will have been replaced several times over.
It is the final benefit of longevity that has caused many cities in the U.S. to adopt programs dedicated to switching entire sectors over to energy efficient LED lighting. In cities like Cincinnati, Ohio and Raleigh, NC programs are underway to test LED lighting systems and switch out much of those cities energy hungry incandescent public lighting equipment with LED designs. In Los Angeles the city has started replacing 140,000 of its streetlights with energy efficient LEDs which are expected to return up to 60% in savings by reducing energy and maintenance costs. With life expectancies rated at 10 or more years and energy efficiency that far surpasses the lights currently in use, it is only a matter of time before they become the dominant form of illumination used in both public and private applications.