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Why Energy Efficient Lighting?

Lighting consumes 22% of the electrical power generated in the U.S.

When you select energy-efficient lighting, you:

• Save a lot of money
• Reduce the need for additional power plants
• Reduce greenhouse gases and other pollution
• Are able to use lighting in ways you never thought possible

Engineers on large remodeling projects find that energy-efficient lighting affords a higher payback than any other energy-efficient system. That includes heating, ventilation, air conditioning, appliances and computer equipment.

Sustainable resource consumption is everyone’s responsibility. Choosing energy-efficient lighting is the easiest way to save money on power. The choice is up to you. What you choose matters to you and the environment.

Why LED's?

Light Emitting Diodes are semiconductors used to create light. There are other types of Solid State Lights ("SSL,") but LED's are the most relevant for general illumination.

LED’s have the brightest future for the broadest range of applications. And they engender environmental sustainability because they consume less power, last much longer and contain no toxics.

LED’s will radically change the energy consumption patterns of the world over the next few years. There’s a phenomenal amount of resources being devoted to improving LED technology worldwide. The U.S. has committed an uncharacteristically large amount of industrial policy support for LED research and development, as you can easily discover for yourself, if you choose to wade through the copious recent studies commissioned on the subject. Asia is a hotbed of cutting-edge manufacturing technology and Europe and Canada have led the way in energy efficient initiatives accompanied by some of some of the most innovative design styles you can find anywhere.

How Can a Light Emitting Diode Produce Light?

readsA diode is the simplest sort of semiconductor device. Broadly speaking, a semiconductor is a material with a varying ability to conduct electrical current. Most semiconductors are made of a poor conductor that has had impurities (atoms of another material) added to it. The process of adding impurities is cal doping. In the case of LEDs, the conductor material is typically aluminum-gallium-arsenide (AlGaAs). In pure aluminum-gallium-arsenide, all of the atoms bond perfectly to their neighbors, leaving no free electrons (negatively-charged particles) to conduct electric current. In doped material, additional atoms change the balance, either adding free electrons or creating holes where electrons can go. Either of these additions makes the material more conductive.

A semiconductor with extra electrons is cal N-type material, since it has extra negatively-charged particles. In N-type material, free electrons move from a negatively-charged area to a positively charged area. A semiconductor with extra holes is cal P-type material, since it effectively has extra positively-charged particles. Electrons can jump from hole to hole, moving from a negatively-charged area to a positively-charged area. As a result, the holes themselves appear to move from a positively-charged area to a negatively-charged area.

A diode comprises a section of N-type material bonded to a section of P-type material, with electrodes on each end. This arrangement conducts electricity in only one direction. When no voltage is applied to the diode, electrons from the N-type material fill holes from the P-type material along the junction between the layers, forming a depletion zone. In a depletion zone, the semiconductor material is returned to its original insulating state -- all of the holes are fil, so there are no free electrons or empty spaces for electrons, and charge can't flow.

At the junction, free electrons from the N-type material fill holes from the P-type material. This creates an insulating layer in the middle of the diode cal the depletion zone. To get rid of the depletion zone, you have to get electrons moving from the N-type area to the P-type area and holes moving in the reverse direction. To do this, you connect the N-type side of the diode to the negative end of a circuit and the P-type side to the positive end. The free electrons in the N-type material are repel by the negative electrode and drawn to the positive electrode. The holes in the P-type material move the other way. When the voltage difference between the electrodes is high enough, the electrons in the depletion zone are boosted out of their holes and begin moving freely again. The depletion zone disappears, and charge moves across the diode.

When the negative end of the circuit is hooked up to the N-type layer and the positive end is hooked up to P-type layer, electrons and holes start moving and the depletion zone disappears.

If you try to run current the other way, with the P-type side connected to the negative end of the circuit and the N-type side connected to the positive end, current will not flow. The negative electrons in the N-type material are attracted to the positive electrode. The positive holes in the P-type material are attracted to the negative electrode. No current flows across the junction because the holes and the electrons are each moving in the wrong direction. The depletion zone increases. When the positive end of the circuit is hooked up to the N-type layer and the negative end is hooked up to the P-type layer, free electrons collect on one end of the diode and holes collect on the other. The depletion zone gets bigger.

The interaction between electrons and holes in this setup has an interesting side effect -- it generates light!

Light is a form of energy that can be released by an atom. It is made up of many small particle-like packets that have energy and momentum but no mass. These particles, cal photons, are the most basic units of light.

Photons are released as a result of moving electrons. In an atom, electrons move in orbitals around the nucleus. Electrons in different orbitals have different amounts of energy. Generally speaking, electrons with greater energy move in orbitals farther away from the nucleus.

For an electron to jump from a lower orbital to a higher orbital, something has to boost its energy level. Conversely, an electron releases energy when it drops from a higher orbital to a lower one. This energy is released in the form of a photon. A greater energy drop releases a higher-energy photon, which is characterized by a higher frequency. As we previously saw, free electrons moving across a diode can fall into empty holes from the P-type layer. This involves a drop from the conduction band to a lower orbital, so the electrons release energy in the form of photons. This happens in any diode, but you can only see the photons when the diode is composed of certain material. The atoms in a standard silicon diode, for example, are arranged in such a way that the electron drops a relatively short distance. As a result, the photon's frequency is so low that it is invisible to the human eye -- it is in the infrared portion of the light spectrum. This isn't necessarily a bad thing, of course: Infrared LEDs are ideal for remote controls, among other things.

Visible light-emitting diodes (VLEDs), such as the ones that light up numbers in a digital clock, are made of materials characterized by a wider gap between the conduction band and the lower orbitals. The size of the gap determines the frequency of the photon -- in other words, it determines the color of the light. While all diodes release light, most don't do it very effectively. In an ordinary diode, the semiconductor material itself ends up absorbing a lot of the light energy.

LEDs are specially constructed to release a large number of photons outward. Additionally, they are housed in a plastic bulb that concentrates the light in a particular direction.

Applications

LED’s are already the best light source for traffic signals, vehicular tail lights, emergency lighting and flashlights. Increasingly, they are viable for accent, task, landscape, portable and even area lighting. LED’s let you do things you just can’t do effectively with other light sources, especially due to LED’s low power consumption.

Imagine powering a string of lights ½ mile long from a single electrical socket. You can, with our commercial line of LED Christmas lights! With LED’s you can use more light than ever before, and still save money. Plus, they last so long, you can design complicated installations without worrying about frequent and costly bulb replacement projects. LED’s have been used to create the most innovative lighting for stage shows, restaurant and hotel interiors, building exteriors and bridges.

General applications of LED’s include:

• Accent lighting. Nothing beats LED’s for color. Programmable color changing, underwater applications, tiles, strings, ropes and tubes are all easier with LED’s. LED landscape lighting provides innovative colors, compact designs and increasingly effective solar-powered solutions that do not require underground cabling. LED lamps are in the trendiest hotels and restaurants around the world.
• Task lighting. Reading lamps, portable work lights, flashlights, wearable head lamps—LED’s are compact, lightweight and highly directional.
• Area lighting. LED’s are increasingly competitive for illuminating larger spaces; however, LED’s are not yet effective for illuminating large halls, parking lots, streets and the like. Use care in selecting LED’s for area lighting. We encourage you to order a sample to check to see if the light levels are adequate for your purposes.

Haitz’ Law says that the luminous efficacy (light output per watt of power consumed) doubles every 18 months. That’s fast! It means that LED’s will become the dominant light source for many area lighting applications with certainty—it’s just a matter of time. New products for path and area lighting are being introduced constantly, and we’ll bring you the latest ones that meet our tough standards.

• Portable lighting. LED’s are great for flashlights and wearable safety products, such as flashing vests. They’re bright, last an extremely long time and promote long battery life because they use so little power. No wonder LED flashlights are the choice for serious SCUBA divers and marksmen, as well as law enforcement and fire departments.