Comparing LEDs and Incandescent Bulbs: Opposite Ends of the Lighting Spectrum|
Article- February 2012 By Larson Electronics.com
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Today more than ever, consumers have an extensive array of lighting options to choose from. Along with old standbys like the incandescent bulb and the fluorescent tube, efforts to improve lighting efficiency and affordability have produced newer technologies like compact fluorescents and LEDs that have greatly widened available lighting solutions. Regardless of how a particular lighting technology operates however, all lighting is little more than a way of converting electrical energy. At the basic level, electrical energy is simply fed into a device, and light energy is outputted. The differences in how well each does this though are quite distinct, and are a significant part of the reasons why some lighting is better suited to some tasks than others. Additionally, how well these different lighting technologies convert electrical energy plays a large role in their efficiency, which is to a great extent the driving force behind the emergence of newer lighting technologies.
When it comes to converting electrical energy to light energy, the best possible result is one that produces a lot of light from a small amount of electricity. Here we’ll consider two lamp types at total opposite ends of the spectrum and see just how far lighting has come in the last 130 years.
Incandescent Light Bulbs
Of all the lighting types, the venerable incandescent light bulb has been around the longest. Simple in design and easily manufactured, the incandescent bulb has been the workhorse of lighting for over 120 years. The basic incandescent light bulb produces slightly yellowish illumination. Early light bulbs were clear and produced very yellow light, which is now normally compensated for with coatings placed on the inside surface of the glass bulb to improve the whiteness of the light produced. The light produced by these bulbs is generally considered soft or “warm white”, meaning they radiate light strongly in the red yellow end of the light spectrum, which in turn imparts a normally unnoticed yellowish cast to objects they illuminate. This is the type of light most familiar to people, and the most popular as well as it imparts a “warmer” and more relaxing feel to the location being illuminated. To get an idea of just how much color an incandescent bulb imparts to objects it illuminates, try turning on a normal table lamp and noting the appearance of white objects in a room. Then try turning on a cool white fluorescent lamp, and you’ll notice a distinct change in the appearance of those same objects. They will appear whiter and sharper under the fluorescent as compared to the incandescent.
The long history of incandescent bulbs gives them many advantages
They are cheap to produce. They are a fully developed lighting technology.
They are easy to replace.
They cost very little to purchase.
They can be used in a wide variety of fixtures.
However, the incandescent bulb also has some serious drawbacks.
Since they have reached full development, there is little efficiency or design improvement possible. The incandescent was developed at a time when efficiency and applications were not major considerations. As a result, the incandescent was developed to produce illumination along the cheapest and most economical guidelines of the times, rather than for optimal output and efficiency. This led to a design that offers little potential for improvement and in fact, the basic design of the incandescent light bulb has changed very little since its beginnings.
Incandescent light bulbs are highly inefficient and waste more of the energy put into them as heat rather than producing light. It is estimated that up to 90% of the electrical power consumed by an incandescent light bulb is wasted as heat.
Incandescent light bulbs are short lived, lasting at the most around 2500 hours and usually only 500-1,000 hours before burning out and requiring replacement.
The color of light produced by incandescent bulbs can only be altered by coating the bulb with colored materials or installing the bulb with lenses or filters. This greatly reduces the amount of light radiated by the bulb, increases the temperature at which it operates, and limits their practical usage to basic lighting applications.
The newest form of lighting, and potentially the most efficient, is the LED. LEDs resemble solid state electronics more than they do a light bulb, and produce light in a wholly different manner. Rather than heat a wire filament within a vacuum tight glass bulb, LEDs pass electrical current through pieces of coated semi-conducting material. As the electricity passes through this material, electrons essentially collide and combine, which results in the formation of photons, also known as light. This light is then radiated from the surface of the semi-conducting material. The process by which LEDs produce light is called electroluminescence, and it is far more efficient than the process of resistance used in incandescent lamps. Very little energy is wasted as heat in an LED, and more of the electrical energy converted to light. This allows LEDs to produce the same amount of light as an incandescent while using only a fraction as much electrical energy. Even better, LEDs can last for well over 50,000 hours, making them far longer lived than most other forms of lighting.
As well as efficiency, LEDs are extremely durable. There is no glass, no gases, or fragile wire filaments used in an LEDs construction. They more closely resemble circuitry in design, which is why LEDs are considered a “solid state” form of lighting. An LED can fall on the floor and it will not shatter. This makes them ideal for use in things like work lights and commercial lights where a lot of abuse takes place.
LEDs produce light that is well defined and made up of a very limited part of the light spectrum. What this means is that unlike incandescent lamps which radiate all parts of the light spectrum, LEDs produce light only within a well defined portion of the light spectrum. Additionally, incandescent bulbs also emit light in the invisible parts of the light spectrum as well, including infrared and ultraviolet. LEDs however, produce very ‘clean” light. There is very little infrared or ultraviolet light produced, and the color temperature of the LED tends to lean towards the blue-white end of the light spectrum. In the past this posed something of a problem for consumers as they felt the light produced by LEDs was too ‘cold” and found that it was less appealing in residential settings. However, LED manufacturers have overcome this by coating the semi-conducting material in LEDs with specific substances which alter the color spectrum of the light produced, allowing them to raise or lower the color temperature of the LED according to its intended application. This also allows manufacturers to produce LEDs which produce light of a specific color without the need for lenses for filters. As a result, a red or blue LED is even more efficient than an incandescent with a red or blue coating or lens as all of the light is emitted rather than filtered.
Despite all the apparent improvements in light production LEDs have brought to the table, there remain some caveats that continue to limit their acceptance among the general public. Chief among these is the fact that LEDs are notably more expensive to purchase than incandescent bulbs. At first glance this appears a major problem, but when we consider the 50,000 hour+ lifespan of the LED, we realize that we eventually save money because we rarely have to replace them.
When we consider these two forms of lighting, it becomes quite apparent that traditional lighting in the form of incandescent bulbs has a very finite potential that is likely nearing the end of its useful life. Concerns with energy and maintenance costs are driving more consumers towards the efficiency offered by LEDs, and new energy standards being enacted worldwide are actively calling for an end to production of the incandescent bulb. At this point in time, the incandescent light bulb could be considered to be in its old age and ready for retirement, while the LED is just beginning to enter its prime.