- LED
- Fluorescent
Friday, June 28, 2013
LED Bulb vs Compact Fluorescent
Currently two energy savings lighting technologies compete on the market:
Wednesday, June 26, 2013
LED lifetime, real versus advertised
We continue the quest to find the answer to the question "Are the savings promised by LED technology always real?"
First we saw how LED performance in real life can be very different from the one advertised, either because of the influence of temperature on brightness or because some producers simply provide false data.
Now we will discuss about the main argument that every seller or producer of LED lamps out there uses to convince: LED lifetime.
LEDs have the potential to last a long time, tens of thousands of hours, much longer than all the other lighting technologies. Therefore, the savings that come from not replacing the lamps or fixtures so often offset by a significant degree the initial, higher cost, of the LED lamp or fixture. In some cases, replacements cost for a lamp can be 16 times higher than the cost of the lamp itself and thus the long life LED is a very convincing argument.
I have read recently about the plan of the city of Los Angeles to replace, over the next 4 years, 140.000 of the cities street lights with LED lamps. It is, to date, the largest such street LED light replacement program in the world, with an estimated total budget of $57 million. As expected, the LED fixture lifetime was the main reason for this retrofit. It is reported that the lifetime of the LED retrofits that will be used is 10 to 12 years compared to four to six years for a typical street lamp.
LED lifetime vs LED fixture lifetime
To discuss about the lifetime of a LED fixture we first need to approach the issue of LED life.
All lighting technologies (LED, incandescent, halogen, fluorescent, HID and so on) see their brightness diminish as time passes. An incandescent bulb can loose 50% or more of its light output in 40.000 hours, as this 110 years old bulb shows but out of any number of bulbs used, in 1000 hours half of them will fail outright. Therefore, the advertised lifetime of any incandescent bulb is around 1000 hours, being equal to the time it takes for 50% of the installed bulbs to fail and not the 40.000 hours it takes too loose 50% of its brightness.
The same way is used to calculate the lifetime of any other lamp or fixture, except LED:
For a high performance LED the L70 lifetime could be equal with 80.000 hours or more, as the graph above shows.
The obvious question that appears from such a graph: How does the LED producer know the LED has a L70 of 80.000 hours, did he test it for so long? What about this LED bulb producer who claims his bulb has lifespan of 50.000 hours:
Because it would take more than 5 years to test a L70 claim of 50.000 hours and almost 9 years to test one of 80.000 hours, no producer in the world does it. It would make no sense, as the product tested will be long outdated by the time the test results arrive. And because such a test requires specialized equipment, a lab and plenty of technical knowledge, now one else does it either.
Still the market is saturated with products that promise a L70 lifetime of 15.000 to 70.000 hours! Where do these numbers come from?
The source of the L70 lifetime data divides and creates chaos, turmoil in the LED market. Some say the market is a wild west, others a jungle because, until very recently, there was no standard way to calculate LED lifetime. L70 LED lifetime information comes from a combination of testing the LED for 100 to 10.000 hours and then extrapolating the results for X0.000 hours. How rigorously the test is done (sample size, measurements, time) and how good is the projecting method used decides the outcome.
When there are no rules and the interest is to have a higher LED L70 lifetime, a significant phenomenon of false advertising appears. As with LED luminous flux, the savings promised by LED technology can occur only if the producer gives true information about lifetime.
In futures posts we will briefly present the standard way in which to obtain L70 lifetime, stay tuned!
First we saw how LED performance in real life can be very different from the one advertised, either because of the influence of temperature on brightness or because some producers simply provide false data.
Now we will discuss about the main argument that every seller or producer of LED lamps out there uses to convince: LED lifetime.
LEDs have the potential to last a long time, tens of thousands of hours, much longer than all the other lighting technologies. Therefore, the savings that come from not replacing the lamps or fixtures so often offset by a significant degree the initial, higher cost, of the LED lamp or fixture. In some cases, replacements cost for a lamp can be 16 times higher than the cost of the lamp itself and thus the long life LED is a very convincing argument.
I have read recently about the plan of the city of Los Angeles to replace, over the next 4 years, 140.000 of the cities street lights with LED lamps. It is, to date, the largest such street LED light replacement program in the world, with an estimated total budget of $57 million. As expected, the LED fixture lifetime was the main reason for this retrofit. It is reported that the lifetime of the LED retrofits that will be used is 10 to 12 years compared to four to six years for a typical street lamp.
LED lifetime vs LED fixture lifetime
To discuss about the lifetime of a LED fixture we first need to approach the issue of LED life.
All lighting technologies (LED, incandescent, halogen, fluorescent, HID and so on) see their brightness diminish as time passes. An incandescent bulb can loose 50% or more of its light output in 40.000 hours, as this 110 years old bulb shows but out of any number of bulbs used, in 1000 hours half of them will fail outright. Therefore, the advertised lifetime of any incandescent bulb is around 1000 hours, being equal to the time it takes for 50% of the installed bulbs to fail and not the 40.000 hours it takes too loose 50% of its brightness.
The same way is used to calculate the lifetime of any other lamp or fixture, except LED:
Lamp lifetime = the time when 50% of the tested or installed lamps fail
LED is the only lighting technology to date for which it takes longer for the lamp to fail than to loose enough light output to make the lamp unusable.
LED lifetime for use in general lighting = the time when the light output (lumens) has reached 70% of the value from the beginning. It is called L70 lifetime.
For a high performance LED the L70 lifetime could be equal with 80.000 hours or more, as the graph above shows.
The obvious question that appears from such a graph: How does the LED producer know the LED has a L70 of 80.000 hours, did he test it for so long? What about this LED bulb producer who claims his bulb has lifespan of 50.000 hours:
Because it would take more than 5 years to test a L70 claim of 50.000 hours and almost 9 years to test one of 80.000 hours, no producer in the world does it. It would make no sense, as the product tested will be long outdated by the time the test results arrive. And because such a test requires specialized equipment, a lab and plenty of technical knowledge, now one else does it either.
Still the market is saturated with products that promise a L70 lifetime of 15.000 to 70.000 hours! Where do these numbers come from?
The source of the L70 lifetime data divides and creates chaos, turmoil in the LED market. Some say the market is a wild west, others a jungle because, until very recently, there was no standard way to calculate LED lifetime. L70 LED lifetime information comes from a combination of testing the LED for 100 to 10.000 hours and then extrapolating the results for X0.000 hours. How rigorously the test is done (sample size, measurements, time) and how good is the projecting method used decides the outcome.
When there are no rules and the interest is to have a higher LED L70 lifetime, a significant phenomenon of false advertising appears. As with LED luminous flux, the savings promised by LED technology can occur only if the producer gives true information about lifetime.
In futures posts we will briefly present the standard way in which to obtain L70 lifetime, stay tuned!
Friday, June 21, 2013
About this blog
This blog is written and maintained by Mr. Victor Floroiu, the man behind the LedRise.com concept. He has 9 years experience in retail and distribution business of LED components and fixtures, having started his first company in this market in 2004.
The main goal of this blog is to help people make an informed buying decision when purchasing LED technology. I will try, as much as possible, to write in an easy to understand language and keep "tech talk"" to a minimum.
This blog aims to give the basic knowledge and is not written for the skilled professionals in the lighting filed. Therefore technical terms as "luminous flux", "lumen maintenance" and so on are usually translated in plain English.
The main goal of this blog is to help people make an informed buying decision when purchasing LED technology. I will try, as much as possible, to write in an easy to understand language and keep "tech talk"" to a minimum.
This blog aims to give the basic knowledge and is not written for the skilled professionals in the lighting filed. Therefore technical terms as "luminous flux", "lumen maintenance" and so on are usually translated in plain English.
Thursday, June 20, 2013
LED performance, the gap between advertised and real luminous flux (2)
In this previous post we have written about how the brightness (luminous flux) of a LED lamp varies with the operating temperature and have said that some producers only advertise the performance at an optimal, lab temperature, of 25 ºC.
We have also shown that the savings promised by LED technology are real only for high performance LEDs.
Now we will talk about another, more serious, aspect about the advertised performance of LED lamps: false advertised brightness.
The brightness (luminous flux) of a light source is impossible to measure at home. One needs specialized measurement equipment and knowledge to measure the luminous flux and some producers take advantage of this aspect to claim their LED lamp has a lot more lumens than in reality.
Lets look at the specs of the LED bulb below:
The producer of this particular light bulb claims his "High Brightness 5W LED Bulb" has a impressive 550 lumens. But is it true? How can we find out the answer without a lab to do the measurements?
Fairly easy, we use comparison and common sense.
For comparison we go to the website of a known brand, in the case of LED bulbs this can be: Samsung, Philips, Osram, Toshiba and we look at the specifications of a LED bulb with similar wattage:
The Samsung LED bulb above has 490 lumens for 6.5 Watts and we can find products with similar specifications at the other brands too. Thus, our common sense tells us that the little known producer that claims his bulb has 5 Watts and 550 lumens is not telling the truth.
The savings promised by LEDs occur only if the producer gives honest information about his product`s performance.
We have also shown that the savings promised by LED technology are real only for high performance LEDs.
Now we will talk about another, more serious, aspect about the advertised performance of LED lamps: false advertised brightness.
The brightness (luminous flux) of a light source is impossible to measure at home. One needs specialized measurement equipment and knowledge to measure the luminous flux and some producers take advantage of this aspect to claim their LED lamp has a lot more lumens than in reality.
Lets look at the specs of the LED bulb below:
The producer of this particular light bulb claims his "High Brightness 5W LED Bulb" has a impressive 550 lumens. But is it true? How can we find out the answer without a lab to do the measurements?
Fairly easy, we use comparison and common sense.
For comparison we go to the website of a known brand, in the case of LED bulbs this can be: Samsung, Philips, Osram, Toshiba and we look at the specifications of a LED bulb with similar wattage:
The savings promised by LEDs occur only if the producer gives honest information about his product`s performance.
Wednesday, June 19, 2013
LED performance, the gap between advertised and real luminous flux (1)
LED technology has made the decision to buy lighting products very complicated. We are promised important savings in energy and maintenance costs and asked in return to pay a higher price, at times dozens of times higher than other lighting technologies: incandescent, halogen or fluorescent.
But are the savings always real?
The answer is: it depends...
In this series of articles we will discuss the elements that can define the answer to this question.
Brightness
When we want to replace our old lights with LED or have a new project that needs light, the first thing we take into consideration is brightness. In tech talk this is measured in lumens and is called luminous flux. Unlike a few years ago, today we can see the luminous flux on most lamp packing at the supermarket or find it on the internet at almost all online shops that sell lamps.
It got like this because brightness has became a very important criteria in the buying decision, so important that some producers/distributors or retailers are willing to give misleading information just to score points in the race for the customers wallet.
Therefore, in the case of some products there is a gap between the advertised brightness and the real, so large that can turn the hole savings argument to buy LEDs on its head.
How temperature affects LED brightness
The performance of LEDs is greatly influenced by ambient and junction temperature (the one inside the LED) as every degree beyond 25 ºC decreases its brightness (lumen output). The amount of lumens lost is what makes buying LED lamps complicated.
A good LED, a Nichia SMD LED for example, will loose less than 10% if the nearby ambient temperature reaches 60 ºC, a very common value inside most fixtures.
On the other hand, a not so good LED, an OEM 3258 SMD for example, will loose at 60 ºC almost half of its brightness.
Most LED producers advertise their products with the performance at 25 ºC but only some mention the temperature at which it was measured and even fewer provide a graph to show the connection between the two values, as the ones above.
Therefore, are the savings promised by LEDs always real?
The savings are real for a high performance LED and false for a low performance one.
When buying LED technology we should always take in consideration this aspect, especially if the price of the product is low or the producer is not a known brand.
Some top brands of LEDs: Cree, Nichia, Osram, Philips, Bridgelux, Citizen...
But are the savings always real?
The answer is: it depends...
In this series of articles we will discuss the elements that can define the answer to this question.
Brightness
When we want to replace our old lights with LED or have a new project that needs light, the first thing we take into consideration is brightness. In tech talk this is measured in lumens and is called luminous flux. Unlike a few years ago, today we can see the luminous flux on most lamp packing at the supermarket or find it on the internet at almost all online shops that sell lamps.
It got like this because brightness has became a very important criteria in the buying decision, so important that some producers/distributors or retailers are willing to give misleading information just to score points in the race for the customers wallet.
Therefore, in the case of some products there is a gap between the advertised brightness and the real, so large that can turn the hole savings argument to buy LEDs on its head.
How temperature affects LED brightness
The performance of LEDs is greatly influenced by ambient and junction temperature (the one inside the LED) as every degree beyond 25 ºC decreases its brightness (lumen output). The amount of lumens lost is what makes buying LED lamps complicated.
A good LED, a Nichia SMD LED for example, will loose less than 10% if the nearby ambient temperature reaches 60 ºC, a very common value inside most fixtures.
On the other hand, a not so good LED, an OEM 3258 SMD for example, will loose at 60 ºC almost half of its brightness.
Therefore, are the savings promised by LEDs always real?
The savings are real for a high performance LED and false for a low performance one.
When buying LED technology we should always take in consideration this aspect, especially if the price of the product is low or the producer is not a known brand.
Some top brands of LEDs: Cree, Nichia, Osram, Philips, Bridgelux, Citizen...
The new Cree XM-L2 LED, what has improved?
Now, with the new XM-L2 Cree, narrows the gap between advertised and real world performance by improving the LED itself and also binning it at 85°C instead of the lab standard of 25°C.
At 25°C the min. luminous flux for 700mA for Cool White increased by 41 lumen to 341 (Bin U2) a 13.6% increase.
At 85°C we cannot compare the two versions but Cree promises a maximum of 1052 lumen Watt which means a 20% performance real world increase.
The change in binning temperature is actually a quiet and important evolution of the LED industry which we will approach in another post. For now lets look below and see why at higher temperature the performance gap between the old XM-L and the new XM-L 2 gets larger.
At 100 °C the XM-L2 losses only 3-4% of flux compared with 15-16% of the older XM-L.
You can purchase both versions in our shop here.
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