Definition

A light-emitting diode (the LED acronym comes from English – Light-Emitting Diode), namely a diode that emits light, is a light emitting semiconductor element that has electric characteristics similar to a diode. When the electric current flows from the anode to the cathode, the diode shall emit either light, or infrared or ultraviolet rays, depending on the semiconductor material and the electric frequency.

How a diode works is pretty complicated to explain, but we present you an analogy so that one can easier see: the LED diode is the physical opposite of the solar cell. While in case of the solar cell the light hits on a panel and is absorbed by the silicon and then converted into electric current, in case of the LED diode the process is exactly reverse: the direct current is converted inside the silicon semiconducting element into light, which is spread through a lens. The great challenge is to obtain this light of a high quality.

The quality area of the LED technology is very wide. The best LED diodes emit light of a quality similar to the one of the halogen light. These diodes are not even identified on the market by the consumers as being LED diodes. Everybody certainly know the low quality cold LED light of the pocket flashlights and bicycle lights. Starting with the October 1, 2010, the manufacturers of domestic LED lamps must state the color temperature and the color rendering index. Thus, the consumers may choose a LED lamp according to the quality and light color they desire.

History

Since When Do We Use LEDs?

1960
Colored light emitting diodes have already been used in the 60s for digital displays and light commercial displays. The light yield and the energy efficiency of these colored LEDs (red, yellow, green, blue) were quite low, much lower than those of a light bulb. Nick Holonayk Jr. (an American researcher) is considered the inventor of the LED.

2000
It was not until the year 2000 that it has been possible to produce white LEDs too. The color rendering capacity of the first generation of white LEDs was bad, while the energy efficiency was similar to that of light bulbs. These LEDs were mainly used for road markings, pocket flashlights and bicycle lights.

2006-2009
From 2006 to 2009 a major breakthrough took place: LED efficiency improved three times, almost reaching the level of energy saving lamps. Simultaneously, the color rendering capacity has been greatly improved, the best products on the market reaching today the quality of halogen lamps. Thus, the LEDs can also be used for room illumination.

2009-2012
Between 2009 and 2012, well known manufacturers such as Cree, Bridgelux or Osram launched on the market LEDs of up to 200 lm / Watt. The quality and the energy efficiency will continue to increase, but probably the progress will not be as spectacular as in the recent years.

FUTURE
In some years, LEDs could significantly change many light application areas. Many disadvantages of today’s energy saving lamps (such as lighting delay, diffuse light, electric smog) can be overcame by using LEDs.

Use

Where Do We Already Use LEDs?

Nowadays, we already use LEDs as a replacement for any light source, from regular E27 light bulbs, spotlights, fluorescent lights, traffic signals, headlights up to street lights. And these are only a few of the LED uses. Of course, due to the fast growing LED market, one can find low quality up to despicable quality products on the market. This is why a lot of people do not dare to upgrade to LED because they think it does not work the same.

People often have in mind only the small, highly luminous LEDs and they are not aware of the existence of high quality products. They only know the products found in Baumarkt, Supermarkt or various catalogues. Unfortunately, only a few people know the high quality products sold by specialized electrical retailers. However, consumers should be interested only in LED products providing this level of quality.

Only these LEDs provide a pleasant light, as we are all used to, and not an intense or annoying one. You will notice no difference in lighting when you enter a room where these LEDs are used. And that’s why it pays to invest in quality products. Because then you can use LEDs everywhere. From stadiums to industrial halls lighting.

Features

The Light-Rendering Capability / Chromatic of Light

As LED lamps may emit light in almost every color possible, starting with October 2010 the manufacturers must specify the color temperature on the packaging. This is measured using the Kelvin (K) measurement unit for temperature, and is classified in three groups:

  • Warm white color: 2700 – 3300 K (2700K electric bulb, 3000K halogen lamp, 827/830 energy saving lamp)
  • Neutral white color: 3300 – 5000 K (840 energy saving lamp)
  • Cold white color / daylight white: > 5000 – 10,000 K (6500K daylight, 865 energy saving lamp)

We have to mention that the lower the color temperature is, the more energy efficient a LED lamp is. The 6000 Kelvin daylight LED lamps have a 25% higher efficiency than the 3000 Kelvin warm white ones. Usually, people consider more pleasant warm white lights for home lightning, as cold white lights, if generally used to light a room, may look blue and sterile. On the contrary, the cold white light is preferred at work as is considered to have an activating effect. The temperature color (measured in Kelvin) is specified on the packaging, as follows: “alb cald” / “warmweiss / “warm white”, respectively “alb rece” / “lumina diurnal” / “kaltweiss” / “tageslichtweiss” / “cold white” / “daylight”.

Even if the same color of the lamps is specified, the LED lamps may emit a very different and wide spectrum of colors and shades, due to their spectral composition of the light. The light emitted by cheap LED lamps is not warm enough and becomes disturbing. In order to present the difference between the different qualities of the products, many manufacturers also state the Ra index o the laps. The lamps having a high color rendering index (CRI = Color Rendering Index) emit colors with a natural and real light. This is the important difference between similar lamps. Our advice is to choose those products having a Ra index of at least 75. Due to the fact that this index does not have to be specified on the packaging, it is possible that one could find it only browsing the Internet or written in the technical guides.

Recycling

Disposal of LED Waste

LED lamps contain electronic components. These must be disposed of as the rest of electronic waste (computers, radios, irons, etc.), in specially designed centers. Unlike energy saving lamps, LEDs do not contain toxic mercury. Starting with August 1st, 2005, all retailers have the obligation to take back all energy saving lamps and LED lamps free of charge. In order to finance the recycling procedure, an advance recycle fee (ARF) is levied on the sale of new products. Thus, all LED waste can be disposed of only via retailers.

The take-back obligation includes, in particular, LED lamps, energy saving lamps, incandescent bulbs but also special lamps, such as mercury vapor lamps or solarium tubes. The take-back and recycling obligation does not apply to the regular electrical bulbs and halogen bulbs, which can still be disposed of mixed with regular household waste.

Common misconception

12 most common misconceptions about LED lamps

Misconception #1: LED technology is a discovery of the XXI century.

The truth is that the first LEDs emerged on the market in the 60’s. They were red, lowly efficient, and were being used, for instance, in the manufacturing of the digital watches. About 40 years had to pass until the first white lighting LEDs were produced.

 

Misconception #2: LEDs emit 90% light and don’t provide residual heat.

The truth is that nowadays, the white light emitting diodes may transform 20 to 25% of current into light, the rest of it being residual heat. This heat is released on the back side of the LED’s surface, thus explaining why the actual ray of light is emitted without residual heat.

 

Misconception #3: LEDs are more energy efficient than fluorescent lamps.

The truth is that the current energy efficiency of a light-emitting diode is similar to the energy saving lamps (about 50 – 60 Lumens per Watt). The best fluorescent lamps have an efficiency of about 100 de Lumens per Watt. Due to their highly focused light, LEDs can emit a very high luminance focused on a small spot. The intensity and quality of light are values that cannot be directly compared with, the same as using a garden hose with a small nozzle one may spray water at a long distance, even if the water flow is low.

 

Misconception #4: LEDs emit cold and poor quality light.

The truth is that the quality scale of the LED technology is huge. The best LEDs emit a light having a quality similar to the one of the halogen lamps. This type of LEDs is still quite expensive and, also, one may be familiar only with the cold and poor quality LED light of the pocket flashlights and bicycle lights. Hence, the consumer doesn’t even identify them as LED lamps.

 

Misconception #5: The lifetime of a LED is virtually unlimited.

The truth is that only high quality LEDs have a long lifetime (20,000 up to 50,000 hours). This involves a high quality power supply unit (a current transformer from 230V to a lower direct voltage) and a manufacturing process that shall efficiently manage the residual heat of the LED chip. The body of the lamp must be made of a metal material and it must not get hot, but slightly warm (as the body’s temperature) during operation.

 

Misconception #6: The white LEDs are a mixture of red-green-blue (RGB) light.

The truth is that the white LED light can be obtained by mixing the base colors. However, the quality of the light emitted this way is low because the important components of the light spectrum are missing. The high quality white LEDs are a combination between a blue LED and a fluorescent layer, similar to the energy saving lamp.

 

Misconception #7: Lighting using LEDs is no longer cost efficient.

The truth is that the use of LED lamps is highly dependent of the scope of use. A LED system used in a restaurant, a shop or a hotel, having a yearly average use time of 4,000 hours, shall have 5 years depreciation and 15 years rated lifetime. The Retrofit lamps (LED lamps having the shape of halogen or fluorescent lamps) are not currently efficient for domestic use.

 

Misconception #8: LED lamps don’t feature the light intensity adjustment.

The truth is that compared with the classic light bulbs, the luminosity of the LED lamps can be adjusted only for those specifically mentioning to provide this feature. As most of the devices on the market being used for adjusting the luminosity are available for lamps of at least 20W, the luminosity can be adjusted only if several LEDs are connected together (as their power ranges between 4W to 20W).

 

Misconception #9: LEDs produce electric smog, the same as energy saving lamps.

The truth is that LEDs need a ballast device, like the energy saving lamps do. But unlike energy saving lamps, the light-emitting diodes need direct current (producing almost no radiation), whilst the energy saving lamps require high frequency alternating current. Measurements performed at ETH Zurich prove that LED lamps emit as low radiation such as light bulbs.

 

Misconception #10: The LEDs production involves high energy consumption.

The truth is that the energy consumption during the LEDs manufacturing amounts for less than 5% of the energy consumption during the entire lifetime. Contrary to what most people believe, the residual waste occurred during the manufacturing process is very low: over 90% of the LED chips can be reused. This is the reason for the wide differences between the products on the market.

 

Misconception #11: LED’s white light is different from lamp to lamp.

The truth is that the colors of light are not standardized for LED yet and the manufacturers provide almost any white light tone. The LED lamps can have the precisely desired color and can be changed if necessary. The problem of different white light tones shall be solved in the near future.

 

Misconception #12: Defective LEDs can be disposed of as domestic waste.

The truth is that the LED lamps contain electronic components. At the end of their (long, hopefully) lifetime, they must be properly disposed of, as the rest of the electronic waste (computers, radios, irons, etc.), in specially designed centers. Unlike energy saving lamps, LEDs do not contain toxic mercury.