Researchers found that moths are more attracted by the brighter white lighting that is increasingly being installed on roads around Britain compared to the older traditional orange street lights.
They say moths find white light or slightly bluish light irresistible and will exhaust themselves by flying around the lights rather than mating or searching for food.
Predators also find it easier to pick the insects off due to the large congregations that gather around modern street lamps.
Professor Richard Ffrench-Constant, a biologist at the University of Exeter who led the study, said: “Just like with butterflies, we have seen moth numbers declining dramatically, but because they are active at night, we are less aware of them.
“Habitat loss has certainly played a role in the declines of moths, but we have found that they different types of moths are attracted to different wavelengths of light.”
“If you use white light or solar lamp with a broad spectrum of wavelengths, then it will attract more moths and that completely disrupts their natural behaviour.”
“They are not mating or feeding on flowers. They tend to circle around the light until they get exhausted and fall to the ground.”
There are around 2,000 species of moths in the UK compared to just 52 species of butterfly.
They play an essential role in helping to pollinate flowers while also providing a key link in the food chain for bats and birds.
Recent research of large, common moths in Britain showed that two thirds have declined by around 28 per cent in the past four decades.
Some species, such as the V-moth, once a common sight in gardens, have suffered declines of up to 99 per cent, according to the work by wildlife charity Butterfly Conservation.
While habitat loss is thought to be among the main causes for their decline, the switch from traditional orange street lighting to whiter lights has also been blamed.
It is not known why moths are attracted to street light, but some theories suggest they use natural light the stars and moon to navigate, and artificial light disorientates them.
Traditional street lights use high pressure sodium bulbs, producing an orange or yellow glow, while modern lights tend to use metal halide bulbs that produce shorter wavelength of light that appears white or slightly blue in colour.
Professor Ffrench-Constant and PHD student Robin Somers-Yeates, whose work is published in the Royal Society journal Biology Letters, found that more species were attracted to the newer lights.
They also found the lights attracted more individuals than the older moths.
Professor Ffrench-Constant said that turning street lights off at night where possible could help to reduce the toll they have on moth numbers.
Astronomers and wildlife campaigners have been pushing for a reduction in light pollution at night due to fears about the impact it has on the environment.
Professor Ffench-Constant added that using new LED bulbs in street lights may help to reduce the impact they have on moths as can produce a single colour of light.
2013年5月29日 星期三
2013年5月28日 星期二
Can Consumers Cope With The High-Priced Switch?
There’s no question that LED illumination represents the next
technological step in home lighting. But how many consumers feel the
same way? Opinions are divided as they weigh the tradeoffs between LED
price, performance, lifecycles, and environmental impacts.
The early attempts at home LED lighting failed. Its light output and color characteristics both were below standard. Today’s LEDs have improved, though, and their output and color performance probably are better than conventional light sources.
Despite those advantages, consumers still vacillate over LED prices. They also remain dubious about how long these products last and how much they’ll save in power costs after making that initial purchase. Environmental considerations are further down on their list of priorities.
LEDs will last between 50,000 and 100,000 hours. With 8760 hours in a year, an LED operating 24 hours a day would have a lifespan of 5.7 years. An LED operating just eight hours a day would last 17.1 years. Consumers often wonder how we know that these LEDs will last that long, though.
An LED’s true lifespan is related to lumen depreciation. According to the Illuminating Engineering Society, once an LED hits 30% depreciation, its lifespan is over. In other words, an LED specified with a 100,000-hour lifespan could be used effectively for about 70,000 hours. It would still work after that, but with reduced lumen output.
Lifespan and junction temperature are key elements in LED reliability. Junction temperature is the temperature at the point where an individual diode connects to its base. Maintaining a low junction temperature increases output and slows LED lumen depreciation.
The junction temperature typically should be maintained below 120°C, requiring a number of heat dissipation strategies. The three principal means of heat transfer are conduction, convection, and radiation. Generally, LEDs are encapsulated in a resin that happens to be a lousy thermal conductor
The heat issues that LEDs create stem from the P-N junction, which is formed in semiconductors by the doping process, in effect creating two semiconductors. The boundary between the two is the P-N junction, which forms a one-way street for the current to pass through.
As electrons move from one crystal to another within the structure of the semiconductor, they fill electron holes and emit photons (light). The heat is generated from the P-N junction by electrical energy that has not been converted into light. This heat must be conducted to the atmosphere via a heatsink. The junction temperature drops when the total thermal resistance from the junction point to atmospheric release is minimized.
Drive current and ambient temperature also can influence the junction temperature. The higher the drive current, the greater the heat generated at the junction. Heat must be moved away from the junction to maintain the specified light output, lifespan, and color. The amount of heat that can be removed depends on the ambient temperature and the design of the thermal path from the junction to the surroundings.
Each LED lighting design must efficiently transfer as much heat as possible away from the LED P-N junction. A severely heat-stressed LED will lose efficiency and light output will diminish, possibly resulting in product failure.
There are other advantages, too. LEDs don’t emit ultraviolet (UV) radiation, which means that organic items like manuscripts and paintings won’t be degraded. LEDs also are useful in the kitchen because they don’t attract insects. Their light doesn’t flicker either, benefitting migraine sufferers as well.
Environmentally, LEDs are way ahead of conventional lighting systems. They don’t include toxic chemicals such as mercury, which can be found in fluorescent lights, nor do they rely on filaments or combustible gases to produce light. They also are manufactured from materials that can, in the main, be recycled.
The early attempts at home LED lighting failed. Its light output and color characteristics both were below standard. Today’s LEDs have improved, though, and their output and color performance probably are better than conventional light sources.
Despite those advantages, consumers still vacillate over LED prices. They also remain dubious about how long these products last and how much they’ll save in power costs after making that initial purchase. Environmental considerations are further down on their list of priorities.
LEDs will last between 50,000 and 100,000 hours. With 8760 hours in a year, an LED operating 24 hours a day would have a lifespan of 5.7 years. An LED operating just eight hours a day would last 17.1 years. Consumers often wonder how we know that these LEDs will last that long, though.
An LED’s true lifespan is related to lumen depreciation. According to the Illuminating Engineering Society, once an LED hits 30% depreciation, its lifespan is over. In other words, an LED specified with a 100,000-hour lifespan could be used effectively for about 70,000 hours. It would still work after that, but with reduced lumen output.
Lifespan and junction temperature are key elements in LED reliability. Junction temperature is the temperature at the point where an individual diode connects to its base. Maintaining a low junction temperature increases output and slows LED lumen depreciation.
The junction temperature typically should be maintained below 120°C, requiring a number of heat dissipation strategies. The three principal means of heat transfer are conduction, convection, and radiation. Generally, LEDs are encapsulated in a resin that happens to be a lousy thermal conductor
The heat issues that LEDs create stem from the P-N junction, which is formed in semiconductors by the doping process, in effect creating two semiconductors. The boundary between the two is the P-N junction, which forms a one-way street for the current to pass through.
As electrons move from one crystal to another within the structure of the semiconductor, they fill electron holes and emit photons (light). The heat is generated from the P-N junction by electrical energy that has not been converted into light. This heat must be conducted to the atmosphere via a heatsink. The junction temperature drops when the total thermal resistance from the junction point to atmospheric release is minimized.
Drive current and ambient temperature also can influence the junction temperature. The higher the drive current, the greater the heat generated at the junction. Heat must be moved away from the junction to maintain the specified light output, lifespan, and color. The amount of heat that can be removed depends on the ambient temperature and the design of the thermal path from the junction to the surroundings.
Each LED lighting design must efficiently transfer as much heat as possible away from the LED P-N junction. A severely heat-stressed LED will lose efficiency and light output will diminish, possibly resulting in product failure.
There are other advantages, too. LEDs don’t emit ultraviolet (UV) radiation, which means that organic items like manuscripts and paintings won’t be degraded. LEDs also are useful in the kitchen because they don’t attract insects. Their light doesn’t flicker either, benefitting migraine sufferers as well.
Environmentally, LEDs are way ahead of conventional lighting systems. They don’t include toxic chemicals such as mercury, which can be found in fluorescent lights, nor do they rely on filaments or combustible gases to produce light. They also are manufactured from materials that can, in the main, be recycled.
2013年5月21日 星期二
LED headlights ready for prime time
My trucking job mostly involves night driving between Toronto and Montreal, in all weather conditions. So I’m keenly aware of the importance of a good headlight system. And commercial drivers obsess about lights all the time – just leave your fog lights on after the mist has cleared and you’ll hear about it on the CB. Don’t get me wrong. The halogen bulbs in my dedicated Volvo do a pretty good job illuminating the road. But recently I’ve noticed that the clearest and brightest low beams belong to Freightliners, specifically Penske-owned Cascadias, as they slide past me on the Big Road.
I recalled seeing a news blurb somewhere about Penske outfitting its tractor fleet with LED headlights, and was genuinely thrilled when editor James Menzies asked me to test drive one of the retrofits. So one April night my godson Zak and I booked a newish 10-speed Freightliner Cascadia with a 425-horse Cummins ISX engine, and went looking for “the darkness on the edge of town.”
Truck lighting has come a long way since 1896 when Karl Benz mounted candles on his prototype truck. From lanterns to acetylene lamps to sealed beams, to halogen, HID-Xenon and finally LED headlights, it’s always been about seeing and being seen. Over the years, lighting solutions have paralleled – and sometimes lagged behind – other aspects of the automotive trade. But occasionally something new comes along that significantly moves the bar several notches.
The round two- and four-headlight sealed beam systems that we’re all familiar with were standard for 50 years or more, and rectangular headlights, mostly found on trucks, became more common after the 1970s. A major step forward came in the early 1980s when bulbs could be changed separately from the lens and reflector, followed in 1983 by the halogen bulb. By replacing the vacuum lamps with halogen (a combination of several gases) the tungsten filaments burned brighter.
Halogen remains the mainstay among trucking fleets but that could be changing. It tends to yellow with age and grow dimmer, and the bulb life is only about 1,000 hours. You often notice the difference when replacing a burned-out headlight. The new one burns much brighter. Depending on the manufacturer, halogen headlights can lose 20% of their luminosity in only 160 hours. Compare this to the “new generation” LED low beams which might eventually lose 7% of their output, but would take 20,000 hours to do so.
At 16 years of age, Zak is a physicist-in-training, and patiently explained to me the difference between candle power and lumens, photons, neutrons and electrons, as we spent several hours trundling the back roads between Toronto and Georgetown looking for dark stretches of highway. This is the time of year when a lot of animals are moving around and getting struck, so we were actually hoping to see some wildlife darting in front of the truck.
This didn’t happen, but the directional fluting of the beams onto the shoulders of the road was excellent. “Sixty degrees,” Zak announced when we stopped, measuring the sideways flaring of the headlights with his protractor.
This is an intentional design feature, according to Brad Van Riper, chief technology officer at Truck-Lite, which produces the solar charger.
By comparison, no one flashed their high beams at me while test driving the Penske Cascadia, but I personally think the intensity of both systems is about the same, though they have slightly different penumbras, and they are both brighter than that to which Joe Highway is accustomed. I was nervous about the amount of light the LEDs were emitting. But to the credit of the Truck-Lite engineers, the horizontal cut-off of the LED’s beam lined up just below a car’s trunk lid at a stop light. LEDs are monochromatic and narrowly focused. To fill out the rest of the light spectrum Truck-Lite used a blue chip that is coated with a phosphor.
“There are many ways of doing this,” says Van Riper, “but the most effective way is by coating the top surface of the LED with a phosphor and when the blue wave length light sees the phosphor, it releases photons that fill the rest of the spectrum, giving you white light.”
I recalled seeing a news blurb somewhere about Penske outfitting its tractor fleet with LED headlights, and was genuinely thrilled when editor James Menzies asked me to test drive one of the retrofits. So one April night my godson Zak and I booked a newish 10-speed Freightliner Cascadia with a 425-horse Cummins ISX engine, and went looking for “the darkness on the edge of town.”
Truck lighting has come a long way since 1896 when Karl Benz mounted candles on his prototype truck. From lanterns to acetylene lamps to sealed beams, to halogen, HID-Xenon and finally LED headlights, it’s always been about seeing and being seen. Over the years, lighting solutions have paralleled – and sometimes lagged behind – other aspects of the automotive trade. But occasionally something new comes along that significantly moves the bar several notches.
The round two- and four-headlight sealed beam systems that we’re all familiar with were standard for 50 years or more, and rectangular headlights, mostly found on trucks, became more common after the 1970s. A major step forward came in the early 1980s when bulbs could be changed separately from the lens and reflector, followed in 1983 by the halogen bulb. By replacing the vacuum lamps with halogen (a combination of several gases) the tungsten filaments burned brighter.
Halogen remains the mainstay among trucking fleets but that could be changing. It tends to yellow with age and grow dimmer, and the bulb life is only about 1,000 hours. You often notice the difference when replacing a burned-out headlight. The new one burns much brighter. Depending on the manufacturer, halogen headlights can lose 20% of their luminosity in only 160 hours. Compare this to the “new generation” LED low beams which might eventually lose 7% of their output, but would take 20,000 hours to do so.
At 16 years of age, Zak is a physicist-in-training, and patiently explained to me the difference between candle power and lumens, photons, neutrons and electrons, as we spent several hours trundling the back roads between Toronto and Georgetown looking for dark stretches of highway. This is the time of year when a lot of animals are moving around and getting struck, so we were actually hoping to see some wildlife darting in front of the truck.
This didn’t happen, but the directional fluting of the beams onto the shoulders of the road was excellent. “Sixty degrees,” Zak announced when we stopped, measuring the sideways flaring of the headlights with his protractor.
This is an intentional design feature, according to Brad Van Riper, chief technology officer at Truck-Lite, which produces the solar charger.
By comparison, no one flashed their high beams at me while test driving the Penske Cascadia, but I personally think the intensity of both systems is about the same, though they have slightly different penumbras, and they are both brighter than that to which Joe Highway is accustomed. I was nervous about the amount of light the LEDs were emitting. But to the credit of the Truck-Lite engineers, the horizontal cut-off of the LED’s beam lined up just below a car’s trunk lid at a stop light. LEDs are monochromatic and narrowly focused. To fill out the rest of the light spectrum Truck-Lite used a blue chip that is coated with a phosphor.
“There are many ways of doing this,” says Van Riper, “but the most effective way is by coating the top surface of the LED with a phosphor and when the blue wave length light sees the phosphor, it releases photons that fill the rest of the spectrum, giving you white light.”
Market Revenue for LED Drivers in General Lighting to Triple
Global revenue for light-emitting diode (LED) drivers used in general lighting applications will more than triple from 2012 to 2015 as the market for solid-state illumination booms, according a new report entitled “LED Driver ICs – World – 2013” from IMS Research, now part of IHS. The market governing LED driver integrated circuits (ICs) for lighting will surge to $666 million USD in 2015, up from $214 million in 2012, as shown in the figure. Growth will moderate somewhat during the following years but revenue is expected to continue to expand, reaching $810 million in 2018.
According to Stephanie Pruitt, light and LEDs analyst for IHS, major advances and cost reductions in lamps, luminaires and automotive lighting are spurring the rapid growth of the market for LEDs in general lighting applications. This, in turn, is generating major opportunities for LED driver ICs.
An LED driver is a power supply designed to suit the electrical characteristics of an LED or an array of LEDs. The residential sector represents the greatest opportunity for growth in the LED lighting driver market. Homes have the largest number of sockets available for LED bulbs. The most common form factor for residential solar led light is the classic A-type lamp (i.e., the pear-shaped bulb used since early in the 20th century). Also popular is the MR16 type of bulb used for directional lighting. Other major opportunities for LED drivers in general illumination lie in the retail as well as the street/parking light markets.
As growth ramps up in general lighting, the rate of expansion, however, is slowing in some areas. For instance, cell phone display backlighting has become a saturated market, while television and signage backlighting now are growing at a slower pace. Computer and office equipment is still generating some respectable growth, mainly due to the boom in tablet devices. LED driver IC suppliers such as Macroblock, Texas Instruments and Skyworks continue to dominate in their respective markets. However, many companies that once concentrated on these sectors have seen flat or declining revenue. These companies, along with new entrants, are switching focus to the increasingly important lighting sector.
The lamp uses Chroma White Technology, which for the first time uses wireless colour tuning. Using a smart device like an iPod, it can be wirelessly programmed to alter the colour temperature from 2200K to 6500K. It has been explained that “The spectral distribution of light can also be adjusted to stimulate the circadian rhythm in the same way daylight would.”
Renowned for their LED tape lights and strip lights, Simple Lighting provides a range of domestic and commercial lighting solutions. Heavily involved in the LED industry for a number of years, the specialists are often approached by customers looking to save money through the energy efficient lights. A representative shares their thoughts on the recent news.
We have seen so many breakthroughs and progressions recently in the LED industry, but it’s important that there are solid efforts such as this, to help get them onto the market and accessible for the average person.
“We’re not surprised the DECC are providing a grant to make this happen, as LEDs are so much more environment friendly than incandescent or fluorescent bulbs. This is largely due to the fact that they only lose 20% of their energy to heat compared to 80%.”
Established in 2009, Simple Lighting Company aims to provide high quality lighting at some of the most competitive prices on the web. The company has grown considerably in recent years and supplies over 4000 products, specialising in LED lighting, LED tape lights, LED strip lights as well as indoor and outdoor lighting. Simple Lighting Company considers customer service its priority, regularly adding new products to the website.
According to Stephanie Pruitt, light and LEDs analyst for IHS, major advances and cost reductions in lamps, luminaires and automotive lighting are spurring the rapid growth of the market for LEDs in general lighting applications. This, in turn, is generating major opportunities for LED driver ICs.
An LED driver is a power supply designed to suit the electrical characteristics of an LED or an array of LEDs. The residential sector represents the greatest opportunity for growth in the LED lighting driver market. Homes have the largest number of sockets available for LED bulbs. The most common form factor for residential solar led light is the classic A-type lamp (i.e., the pear-shaped bulb used since early in the 20th century). Also popular is the MR16 type of bulb used for directional lighting. Other major opportunities for LED drivers in general illumination lie in the retail as well as the street/parking light markets.
As growth ramps up in general lighting, the rate of expansion, however, is slowing in some areas. For instance, cell phone display backlighting has become a saturated market, while television and signage backlighting now are growing at a slower pace. Computer and office equipment is still generating some respectable growth, mainly due to the boom in tablet devices. LED driver IC suppliers such as Macroblock, Texas Instruments and Skyworks continue to dominate in their respective markets. However, many companies that once concentrated on these sectors have seen flat or declining revenue. These companies, along with new entrants, are switching focus to the increasingly important lighting sector.
The lamp uses Chroma White Technology, which for the first time uses wireless colour tuning. Using a smart device like an iPod, it can be wirelessly programmed to alter the colour temperature from 2200K to 6500K. It has been explained that “The spectral distribution of light can also be adjusted to stimulate the circadian rhythm in the same way daylight would.”
Renowned for their LED tape lights and strip lights, Simple Lighting provides a range of domestic and commercial lighting solutions. Heavily involved in the LED industry for a number of years, the specialists are often approached by customers looking to save money through the energy efficient lights. A representative shares their thoughts on the recent news.
We have seen so many breakthroughs and progressions recently in the LED industry, but it’s important that there are solid efforts such as this, to help get them onto the market and accessible for the average person.
“We’re not surprised the DECC are providing a grant to make this happen, as LEDs are so much more environment friendly than incandescent or fluorescent bulbs. This is largely due to the fact that they only lose 20% of their energy to heat compared to 80%.”
Established in 2009, Simple Lighting Company aims to provide high quality lighting at some of the most competitive prices on the web. The company has grown considerably in recent years and supplies over 4000 products, specialising in LED lighting, LED tape lights, LED strip lights as well as indoor and outdoor lighting. Simple Lighting Company considers customer service its priority, regularly adding new products to the website.
2013年5月2日 星期四
Jumping ship
The fluorescent lights of Woolworth 104 did their best to keep me and my peers awake and participating in our Writing Seminar on a stormy Wednesday night. As is the case with most night classes (from what I have heard), we unloaded the baggage from our entire day right as we dropped our backpacks and book bags, slumping into the wooden chairs that would serve as our foundations for the next 1.5 hours.
To liven up the scene a bit, my professor asked us each week to introduce ourselves by name, and then to state a specific fact, wish or other piece of information. Some weeks it was guilty pleasures, other weeks it was favorite food or our vacation spot. This week it was summer plans.
I immediately began to dread my turn at this introduction. After around five or so humble, toned-down announcements of international visits and prestigious opportunities — New York, China and Germany to name a few — we arrived at myself. I sheepishly replied, “I’m not sure what I’m doing yet.”
Don’t get me wrong. The lights didn’t flicker and the class was not agape. I’m not trying to pretend that my professor pointed a chalkboard eraser at my head, banishing me to the furthest corner of campus (Forbes — just kidding). But the mixture of my own bitterness and the change in his reaction to my explanation that I was still looking for internship opportunities in the San Francisco Bay Area — my hometown — produced a sour taste. How was he supposed to react? How was anyone supposed to pretend that “still looking around” was as exciting of a response as “South Africa?”
This was already a sore subject for me as the road had already been rocky enough. Just days earlier, I was forced to reject an internship offer because, due to University policy, I could not receive academic credit for it. My heart sank as I read an email that stated that the company of interest could not offer me a position if I did not receive academic credit for my work — “otherwise we would hire you as an intern in a heartbeat,” they said.
As I grimly continued my search for unpaid internships with nonprofit and government organizations, I realized that this was part of a much larger problem at Princeton. The University, without exceptions, does not offer academic credit for jobs and internships in which students participate. Many companies, without exceptions, do not offer positions to candidates who cannot receive academic credit. Many companies offering unpaid internships seek to give students something for their time and effort, so as not to be perceived as using a major swath of the American population as a free work force. The semblance of an unfair labor transaction is a scar that no organization wants to sport.
To be fair, when this situation arises, Career Services can write a letter of support indicating that it approves of students’ unpaid participation in such internships, essentially giving employers the green light to hire students without compensating them (monetarily or with academic credit). But for many, as in my case, a letter of support is simply not enough.
The problem here is, with the lack of reconciliation between two disparate philosophies, the students get left behind. I have looked through countless pages of internships with reputable organizations, and the same language serves as my instantaneous obstacle: “applicants must receive college course credit, no exceptions.” I’m still looking for something to do in my area this summer.
To liven up the scene a bit, my professor asked us each week to introduce ourselves by name, and then to state a specific fact, wish or other piece of information. Some weeks it was guilty pleasures, other weeks it was favorite food or our vacation spot. This week it was summer plans.
I immediately began to dread my turn at this introduction. After around five or so humble, toned-down announcements of international visits and prestigious opportunities — New York, China and Germany to name a few — we arrived at myself. I sheepishly replied, “I’m not sure what I’m doing yet.”
Don’t get me wrong. The lights didn’t flicker and the class was not agape. I’m not trying to pretend that my professor pointed a chalkboard eraser at my head, banishing me to the furthest corner of campus (Forbes — just kidding). But the mixture of my own bitterness and the change in his reaction to my explanation that I was still looking for internship opportunities in the San Francisco Bay Area — my hometown — produced a sour taste. How was he supposed to react? How was anyone supposed to pretend that “still looking around” was as exciting of a response as “South Africa?”
This was already a sore subject for me as the road had already been rocky enough. Just days earlier, I was forced to reject an internship offer because, due to University policy, I could not receive academic credit for it. My heart sank as I read an email that stated that the company of interest could not offer me a position if I did not receive academic credit for my work — “otherwise we would hire you as an intern in a heartbeat,” they said.
As I grimly continued my search for unpaid internships with nonprofit and government organizations, I realized that this was part of a much larger problem at Princeton. The University, without exceptions, does not offer academic credit for jobs and internships in which students participate. Many companies, without exceptions, do not offer positions to candidates who cannot receive academic credit. Many companies offering unpaid internships seek to give students something for their time and effort, so as not to be perceived as using a major swath of the American population as a free work force. The semblance of an unfair labor transaction is a scar that no organization wants to sport.
To be fair, when this situation arises, Career Services can write a letter of support indicating that it approves of students’ unpaid participation in such internships, essentially giving employers the green light to hire students without compensating them (monetarily or with academic credit). But for many, as in my case, a letter of support is simply not enough.
The problem here is, with the lack of reconciliation between two disparate philosophies, the students get left behind. I have looked through countless pages of internships with reputable organizations, and the same language serves as my instantaneous obstacle: “applicants must receive college course credit, no exceptions.” I’m still looking for something to do in my area this summer.
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