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The Best Science Writing Online 2012
Showcasing more than fifty of the most provocative, original, and significant online essays from 2011, The Best Science Writing Online 2012 will change the way...
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[Below is the original script. But a few changes may have been made during the recording of this audio podcast.]
It's the twinkling lights that make a Christmas Tree so festive.
And, the recent upgrades from the bulbous models of yesteryear, also shine a light on the future of lighting.
That's because many modern light strands are composed of LEDs—light emitting diodes. Diodes are electrical devices made up of two different materials that conduct electricity. In the case of the light-emitting variety, a semiconductor casts off light when electricity flows into it.
This is important as it is a more efficient way of producing light than conventional light bulbs, whose glow relies on heating tungsten filaments to at least 3,100 degrees Fahrenheit. LEDs are also more efficient than fluorescent light bulbs, which require less electricity than Edison's invention to excite gases to emit light.
Some LEDs under development require 10 times less electricity than an equivalent conventional light bulb and less than half the electricity required by a fluorescent light source. That has convinced cities from Raleigh, North Carolina to Anchorage, Alaska to adopt them for public lights.
The U.S. Department of Energy estimates that this switch would reduce electricity demand for lighting by 62 percent and avoid the need for at least 133 new power plants.
This would mean a lot fewer greenhouse gases going into the atmosphere and warming the earth, all thanks to a technology refined in part for your Christmas tree.
—David Biello
60-Second Earth is a weekly podcast from Scientific American. Subscribe to this Podcast: RSS | iTunes
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Reply | Report Abuse | Link to thisDavid, 60 seconds is supposed to be the time it takes to READ the article, not WRITE the article. Using the term "10 times less" is just plain wrong! Just because you write about science doesn't give you the right use poor English. Please re-read William Zinser's "On Writing Well" for a refresher course. There is a chapter specifically about science writing. Your readers deserve the best.
Bill Allyn
I've become a firm believer in the efficiency of LEDs. Not only because of the incredible brightness of my flashlight powered by a small button-cell, but also because of the string of 50 flashing multi-colored LEDs I have around my cubicle that have been flashing every day for the past ten days, powered by a single AA battery. That's at least 90 hours, and still going strong. I can see automobile headlight LEDs in the near future. This is a quietly revolutionary technology. If all the lights were replaced with LEDs today, the reduction in energy consumption would be phenomenal.
Reply | Report Abuse | Link to thisMy bike already has LED lights, powered by a dynamo (not batteries). What I like best is that they seem to last forever. With conventional bulbs (halogen) I had one or two replacements each winter. Now I'm using the same LED for 4 years.
Reply | Report Abuse | Link to thisGreat! It is technology! It indicates the future without retrogrades.
Reply | Report Abuse | Link to thisGood to see new technology occupying a space reserved for ecological matters.
Awesome, another prescriptivist would-be copy editor flooding the article with his pedantry.
Reply | Report Abuse | Link to thisNo English speaking individual would be confused by the use of "ten times less" as a substitution for "a tenth of".
There is a woeful lack of information on the efficiency of light sources. Efficency has two major components:-
Reply | Report Abuse | Link to this1 The amount of energy used to generate a given level of illumination. I understand that automotive light bulbs are considerably more efficient than domestic incandescen light bulbs.
2 The power factor (Cos phi) required to provide the necessary power in the power supply system. I understand that the conventional incandescent bulb operates at a power factor of about 1.0 because it is purely resistive. Becaue of the nature of the drivers in fluorescent bulbs, the power factor could be as low as .35 unless suitably compensated for with a built in capacitor
3 The energy consumed in manufacturing the light source.
Then there are additional parameteres such as mercury in fluorescent bulbs which cause disposal problems
There is a woeful lack of information on the efficiency of light sources. Efficency has two major components:-
Reply | Report Abuse | Link to this1 The amount of energy used to generate a given level of illumination. I understand that automotive light bulbs are considerably more efficient than domestic incandescen light bulbs.
2 The power factor (Cos phi) required to provide the necessary power in the power supply system. I understand that the conventional incandescent bulb operates at a power factor of about 1.0 because it is purely resistive. Becaue of the nature of the drivers in fluorescent bulbs, the power factor could be as low as .35 unless suitably compensated for with a built in capacitor
3 The energy consumed in manufacturing the light source.
Then there are additional parameteres such as mercury in fluorescent bulbs which cause disposal problems
Normally, electricity is distributed in the net as AC, while LEDs need DC to work. Cars, handheld lamps, etc. have got a DC source (the battery) while domestic and public lighting need an AC-DC converter to feed LEDs. The efficiency of the converter should be included when calcutating the cost of LED lighting. Thatnotwithstanding, I believe that, apart from this (slight) correction, the savings would be really HUGE and I am enthousiastic on the use of LEDs
Reply | Report Abuse | Link to thisexcellent! do give us periodic updates of this.
Reply | Report Abuse | Link to thisalkemi,
Reply | Report Abuse | Link to thisI have looked at my Xmas lights. They actually flicker and they have more wires than the old series incandescent strings. I believe that they are built as a pair of series - one going each direction in the current. Diodes block current in one direction, and running them in series divides the voltage each diode sees. So, for example, we have 120 volts divided by 35 LEDs = 4 volts, in a pulsed DC; and going the other direction, the same thing. This is a very cheap and simple way to provide low voltage DC without complicated electronics. I suppose the same thing could be done in an LED light panel, I suppose.
gar37bic,
Reply | Report Abuse | Link to thisI wonder if you meant that your LEDs do not need an AC-DC converter. If this is the case, simply check the plug: if it contains the converter, then it is box-shaped and, on the rear surface, reports information on the characteristics of the AC and DC (something like, e. g.: "Input: AC 120V Output DC 4V"). Otherwise, that means that diodes themselves are used ad rectifiers, as you suppose. In this last case, however, the number of wires should be small, in fact 2: one for the first series of the couple, and one for the second.
alkemi,
Reply | Report Abuse | Link to thisYes, no converter. They look just like an 'old-style' string of incandescents with a those combo plug-sockets at each end, so you can connect additional strings at either end. My note was written late at night and left out some details, but you have the essence. By stringing the LEDs in series, the maker can make a workable product at a lower cost. The wiring - two wires out of each socket, but in the length between all the LEDs there are three. I am guessing one is a common, while the two others are the 'hot' side of the 'left' and 'right' series. But it's hard to tell - the string is one of those multi-colored 'icycle' strings. Hmm. Looking closer, the little groups hanging down to form the icycles each have two-wires, except for the middle one which has three.
Anyway, the principle remains the same - a 120VAC fixture can be constructed by using numerous LEDs in two opposing-direction series.
Actually, you would have to know the exact value of "less" in order to calculate "ten times less." It's a really imprecise expression and should not appear in a science article.
Reply | Report Abuse | Link to thisA discussion of science requires precision in order to be meaningful. In the above example, one would need an exact definition of "less" to know what "ten time less" means. In a science context this is not trivial or pedantic.
Reply | Report Abuse | Link to thisI installed 54 LED light fixtures from Cree (LR6) last year. Each one of them produces the light of a 65W incandescent bulb using only 12W. I am saving about $100 to $150 per month on my electric bill. They will pay for themselves in another year. They have a life expectancy of 50,000 hours and are somewhat dimmable. I am very happy with them. I wish more households would switch to them.
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