ark@alice.UUCP (Andrew Koenig) (02/02/85)
Let's see: if a 100-watt light bulb costs $1.00 and electricity costs $0.10/kwh, then the bulb costs $0.01/hour to operate. If the bulb lasts 750 hours, it uses $7.50 worth of electricity over its lifetime. Light bulbs that last longer do so by running cooler, hence more efficiently. Suppose for instance that you could buy a light bulb for $1.00 that would last forever but was 25% less efficient, so it gave as much light as a conventional 75-watt bulb. Such a bulb would cost $0.01/hour to operate, since the initial cost would be amortized over as long as you like. However, one could also use a conventional 75-watt bulb instead. They last longer than conventional 100-watt bulbs -- about 1000 hours, and also cost about $1.00. Thus the cost of the bulb is $0.001/hour and the cost of the electricity is $0.0075/hour, for a total of $0.0085/hour, which is a 15% saving over the infinite-life 100-watt bulb.
2141smh@aluxe.UUCP (S. M. Henning,) (02/04/85)
**** **** From the keys of Steve Henning, AT&T Bell Labs, Reading, PA aluxe!2141smh > Light bulbs that last longer do so by running cooler, hence more > efficiently. This article had a lot of good ideas and good analysis but this flip remark flopped. Tungsten lamps that run cooler give off much less light per watt, thus the lumens per watt is very low, thus the efficiency is very very low.
mag@whuxlm.UUCP (Gray Michael A) (02/05/85)
> **** **** > From the keys of Steve Henning, AT&T Bell Labs, Reading, PA aluxe!2141smh > > > Light bulbs that last longer do so by running cooler, hence more > > efficiently. > > This article had a lot of good ideas and good analysis but this flip > remark flopped. Tungsten lamps that run cooler give off much less > light per watt, thus the lumens per watt is very low, thus the > efficiency is very very low. There is an inconsistency in the reply above. "Much less light per watt" means that there must be, correspondingly, much more heat per watt. This would lead to running hotter, not cooler. Bulbs have only two forms of power dissipation - heat radiation and light radiation. The sum of power in each component must, by conservation of energy, add up to the power that the bulb uses. The less power dissipated as heat, the more dissipated as light; therefore, the light-producing efficiency of the bulb increases as it runs cooler for any given wattage. For an extreme example, look at a pair of 20 watt fluorescent tubes: they give off far more light than a 40 watt bulb, and they only get faintly warm. I think this is what Steve Henning meant. Mike Gray, BTL, WH
msb@lsuc.UUCP (Mark Brader) (02/07/85)
Quote battle abridged: > > > Light bulbs that last longer do so by running cooler, hence more > > > efficiently. > > > > ... Tungsten lamps that run cooler give off much less > > light per watt, thus ... the efficiency is very very low. > > There is an inconsistency in the reply above. "Much less light per watt" > means that there must be, correspondingly, much more heat per watt. This > would lead to running hotter, not cooler. Bulbs have only two forms > of power dissipation - heat radiation and light radiation. ... You must remember that heat is not the same as temperature. You can put your hands into an oven where the air is at 450 degrees F, and not get burned -- but try touching metal or water at 200 degrees F, and you will. The air is less massive* so it carries less heat. The FILAMENT of a long-life bulb runs cooler than that of an ordinary bulb, which helps it last longer; but as the last quote points out, the bulb has to dissipate energy somehow, since it gives less light per watt, and so, yes, the bulb as a whole must give out more heat. Conclusion: a long-life bulb must have a larger filament, so that it can give out more heat without being at as high a temperature. The bulb runs warmer, the filament cooler. Mark Brader
gino@voder.UUCP (Gino Bloch) (02/08/85)
[sacrifice for bug] > For an extreme example, look > at a pair of 20 watt fluorescent tubes: they give off far more light > than a 40 watt bulb, and they only get faintly warm. You are comparing blackbody radiation (filament bulb) with a mixture of blackbody and line radiation. The reason the fluorescent tubes stay cool is that they DON'T radiate as a black body, so lots of what comes out of them is visible. The reason reduced voltages on filament bulbs makes them LESS efficient is that they run at lower temperatures at the lower voltages, thus more of their (blackbody) radiation is in the infrared, thus less of the applied power results in radiation that stimulates our retinas. Any light bulb can radiate invisible radiation (IR, UV) and can also transfer heat (molecular kinetic energy) to its surroundings by conduction. This, as well as invisible radiation, is a source of inefficiecy (ie, waste). Maybe someone who is taking a lab course in thermo can measure all this stuff and end all this idle speculation ... -- Gene E. Bloch (...!nsc!voder!gino) The opinions expressed above are accidents.
jay@unm-la.UUCP (02/10/85)
> For an extreme example, look > at a pair of 20 watt fluorescent tubes: they give off far more light > than a 40 watt bulb, and they only get faintly warm. > For an extreme test of your theory, place your finger firmly on the ballast that drives those tubes. :-) -- Jay Plett {{ucbvax,gatech}!unmvax, lanl}!unm-la!jay
jin@hropus.UUCP (Jerry Natowitz) (05/10/86)
How many cats does it take ... (:-) Couple of questions on light bulbs for you folks out there: 1) What is the spectrum (at least as filtered by the bulb) of the blue flash that a dying light bulb (or the filament thereof) produces? As a child I used to think that the bulbs gave off X-rays when they died (I have no idea where that belief came from). 2) I use Bulbsavers on some of my light bulbs. Bulbsavers are stick-on thermisters, a device that changes from a high electrical resistance to a very low resistance when they heat up. The theory (well proven by my experience) is that the bulbs last longer because the thermister reduces thermal shock to the filament caused by the rush of current that normally occurs when turning on a light. I have read that the light output of "thermistered" bulbs is decreased even at normal operating temperature and have noticed a "yellow shift" in the spectrum. My question is: how much of a decrease in light output do these things cause and what change in the light spectrum does occur? BTW, it takes a few seconds for a thermistered bulb to light up. It's quite funny to see the puzzled reaction of people used to instant light when they turn one of these suckers on. -- Yours in hair, Bear ihnp4!houxm!hropus!jin
ark@alice.UucP (Andrew Koenig) (05/11/86)
I have heard that those "lightbulb saver" gadgets (which I think, by the way, are not thermistors but diodes) are not worth the money. Reason: light bulbs are less efficient at lower temperatures. If instead of using a diode you replace the light bulb with one of lower wattage that gives the same amount of light, the extra efficiency will save you enough electricity to pay for the light bulb by the time it burns out.
bl@hplabsb.UUCP (Bruce T. Lowerre) (05/14/86)
> 2) I use Bulbsavers on some of my light bulbs. Bulbsavers are stick-on > thermisters, a device that changes from a high electrical resistance > to a very low resistance when they heat up. > The theory (well proven by my experience) is that the bulbs last longer > because the thermister reduces thermal shock to the filament caused by > the rush of current that normally occurs when turning on a light. > I have read that the light output of "thermistered" bulbs is decreased > even at normal operating temperature and have noticed a "yellow shift" > in the spectrum. > > My question is: how much of a decrease in light output do these things > cause and what change in the light spectrum does occur? > > BTW, it takes a few seconds for a thermistered bulb to light up. It's > quite funny to see the puzzled reaction of people used to instant light > when they turn one of these suckers on. It's not the sudden rush of current that is hard on the filament but the AC current. I've seen slow motion movies of filaments warming up when being lit. The alternating magnetic field plus the softening of the filament as it warms up causes it to do a lot of "break dancing" (excuse the pun).
larry@kitty.UUCP (Larry Lippman) (05/18/86)
In article <446@hropus.UUCP>, jin@hropus.UUCP (Jerry Natowitz) writes: > > 1) What is the spectrum (at least as filtered by the bulb) of the > blue flash that a dying light bulb (or the filament thereof) produces? > As a child I used to think that the bulbs gave off X-rays when they > died (I have no idea where that belief came from). The blue flash from a "dying" lightbulb is actually the momentary ionization of the argon in the nitrogen-argon fill gas mixture. When the filament fails, a momentary arc is struck as the pieces fall apart; this arc results in the ionization. No significant ionization takes place in a conventional incandescent lamp during normal operation. There could be a slight grain of truth to the x-ray story. X-rays are given off when electrons strike a HARD target material - like the tungsten lamp filament. Most x-ray tubes use anodes (i.e., the target) which are made of tungsten. It is quite possible that a momentary, miniscule amount of very _soft_ x-rays would be given off during the brief ionization which accompanies an incandescent lamp failure. I cannot overemphasize how brief and miniscule such x-ray emanation might be. Without doing some calculations, I am not certain if in fact there is enough energy in a 120 volt lamp to create x-rays all - but I would guess there is. Such x-ray radiation would be modulated at 60 Hz, and chances are only a few cycles would exist. > 2) I use Bulbsavers on some of my light bulbs. Bulbsavers are stick-on > thermisters, a device that changes from a high electrical resistance > to a very low resistance when they heat up. > The theory (well proven by my experience) is that the bulbs last longer > because the thermister reduces thermal shock to the filament caused by > the rush of current that normally occurs when turning on a light. > I have read that the light output of "thermistered" bulbs is decreased > even at normal operating temperature and have noticed a "yellow shift" > in the spectrum. > > My question is: how much of a decrease in light output do these things > cause and what change in the light spectrum does occur? There is always some resistance to the thermistor - even when hot - so the lamp will never see the full line voltage. If you have noticed a "yellow shift", then the lamps must be operating at a REALLY LOW voltage. An incandescent lamp behaves like a black body, and hence lamp energy is measured as "color temperature" - the temperature of an equivalent black body in degrees Kelvin. Normal household incandescent lamps have color temperature ratings of 2700 to 3100 degrees K. Lamp operating current determines color temperature (of a given lamp). It might surprise you to learn that while operating a _given_ lamp from 2700 to 3100 degrees K. (by varying current) causes a change in OVERALL radiated energy of almost 50%, the spectral distribution change in the VISIBLE portion (400 to 700 nanometers) is almost nil. Notice that I have not said what happens when an incandescent lamp is run much below 2700 degrees K.; below that value, an incandescent lamp becomes extremely inefficient, and will, of course, show a spectral shift toward red. In very rough terms - for small values of less than 20% from the rated value of the lamp - a change in lamp current results in an exact corresponding change in lamp energy output; i.e., decreasing lamp current by 10% results in roughly 10% less lamp energy (watts). Also for small values of less than 20%, a change in lamp current results in TWICE the amount of visible light output; i.e., decreasing lamp current by 10% results in 20% less visible light output (lumens). Also, notice that I have been referring to lamp current rather than lamp voltage. While decreasing lamp voltage decreases lamp current, it is a non-linear function, and the current is really the parameter which determines energy output. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York ==> UUCP {bbncca|decvax|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry ==> VOICE 716/688-1231 {rice|shell}!baylor!/ ==> FAX 716/741-9635 {G1, G2, G3 modes} seismo!/ ==> "Have you hugged your cat today?" ihnp4!/
larry@kitty.UUCP (Larry Lippman) (05/18/86)
In article <5436@alice.uUCp>, ark@alice.UucP (Andrew Koenig) writes: > I have heard that those "lightbulb saver" gadgets (which I think, by > the way, are not thermistors but diodes) are not worth the money. > Reason: light bulbs are less efficient at lower temperatures. > If instead of using a diode you replace the light bulb with one of > lower wattage that gives the same amount of light, the extra efficiency > will save you enough electricity to pay for the light bulb by the > time it burns out. Standard lightbulbs are available in a 130 volt rating, as opposed to the normal 120 volt rating. Operating a 130 volt lamp at 120 volts does not appreciably lower the light output, but seems to appreciably increase lamp life (as compared to 120 volt lamps). I have used 130 volt lamps in outdoor lights around my house and in vapor-tight fixtures in my barn for a number of years with excellent results. These lamps seem to take the thermal shock much better than a 120 volt lamp (like when an outdoor lamp is turned on at 0 degrees F.). I have also tried lamps rated as "rough service" lamps, but have had much better luck with the 130 volt variety for outdoor use. Believe it or not, I have 130 volt lamps in my barn which are over six years old. I specifically chose the 130 volt lamps for use in guarded, vapor-tight fixtures, because it is a pain in the you-know-what to change lamps in that type of fixture. You can get 130 volt lamps from any wholesale electrical supply firm (which will generally sell to anyone over-the-counter on a cash basis). The price is about the same as for regular 120 volt lamps. ==> Larry Lippman @ Recognition Research Corp., Clarence, New York ==> UUCP {bbncca|decvax|rocksanne|rocksvax|watmath}!sunybcs!kitty!larry ==> VOICE 716/688-1231 {rice|shell}!baylor!/ ==> FAX 716/741-9635 {G1, G2, G3 modes} seismo!/ ==> "Have you hugged your cat today?" ihnp4!/
gordon@cae780.UUCP (05/20/86)
In article <1039@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: > Standard lightbulbs are available in a 130 volt rating, as opposed >to the normal 120 volt rating. Operating a 130 volt lamp at 120 volts does >not appreciably lower the light output, but seems to appreciably increase >lamp life (as compared to 120 volt lamps). > ... > ... I have also tried >lamps rated as "rough service" lamps, but have had much better luck with >the 130 volt variety for outdoor use. ... I heartily second the 130v suggestion. The "rough service" bulbs are very useful too, but not because of longer life in normal service -- they survive much better in things like garage/workshop extension lights where vibration and rough handling usually kill the bulbs long before they can burn out. FROM: Brian G. Gordon, CAE Systems Division of Tektronix, Inc. UUCP: tektronix!cae780!gordon {ihnp4, decvax!decwrl}!amdcad!cae780!gordon {hplabs, resonex, qubix, leadsv}!cae780!gordon USNAIL: 5302 Betsy Ross Drive/#58137, Santa Clara, CA 95052-8137 AT&T: (408)748-4817 [direct] (408)727-1234 [switchboard]
timothym@tekigm2.UUCP (05/22/86)
Hi, About lightbulbs - Has anyone else besides me measured their line voltage that comes into their house? I measured mine after several of my lights blew, were replaced then blew again in what seemed an abnormally short period of time. My measurment turned up a nominal voltage of 127.5 volts RMS (with a true RMS DVM made by Beckman). I called the power company, Portland General Electric, and I got the reponse "This is the normal voltage we set the lines to, to avoid the chance of brown-outs in the winter time." I just had to ask myself if PGE's motives were more pocketbook oriented. Quick calculations say that power usage will increase as the square of the voltage. What this means is that a lamp rated at 120 volts (when a common line voltage used to be 117 volts RMS) is being run at 127 volts, thereby reducing its life expectantcy to approximately 65 to 76 percent of normal (That's right folks, a 5 percent increase in lamp voltage results in 20 percent increase in light out put and a 30 percent decrease in lamp life). In lamps, the voltage increase only amounts to about a 2 to 4 percent increase in current draw, but this increase combined with refridgerators, stoves, Tv's, and most other appliances, amounts to a * VERY * large increase in overall use of electricity. In general, a 5 percent increase in current, with a 5 percent increase in line voltage will result in a 10 percent increase of wattage. In simple terms: A lamp running at 120 volts, 1.00 amps = 120 watts A lamp running at 127 volts, 1.05 amps = 133 watts OR A 10.8 PERCENT INCREASE IN POWER USAGE ! Not a bad way at all for the utility companies to bolster a shrinking consumer power usage market. And 99 percent of the people out there (you), are not even aware that you've been had. I tried to get PGE to lower the line back to 117 volts, but they refused to do so because I was also tied to four other houses. When I mentioned the problem to my neighbors, they all were totally unknowlegeable about AC theory and they refused to complain along with me, although one did complain about higher than normal electric bills. The moral - you can't fight PGE ! Oh well, any comments or suggestions are more than welcome. -- Tim Margeson (206)253-5240 tektronix!tekigm2!timothym @@ 'Who said that?' PO Box 3500 d/s C1-937 Vancouver, WA. 98665
pmk@prometheus.UUCP (Paul M Koloc) (05/23/86)
In article <2214@cae780.UUCP> gordon@cae780.UUCP (Brian Gordon) writes: >In article <1039@kitty.UUCP> larry@kitty.UUCP (Larry Lippman) writes: >>Standard lightbulbs are available in a 130 volt rating . Operating >>a 130 volt lamp at 120 volts does not appreciably lower the light output, >>but seems to appreciably increase lamp life (as compared to 120 volt lamps). >> .. as "rough service" lamps, [ I ] had much better luck with the 130 volt >>variety for outdoor use. ... > >I heartily second the 130v suggestion. The "rough service" bulbs are very >useful too, they survive ... .vibration and rough handling which usually >kill the bulbs long before they can burn out. > Operating the lamps at lower temperatures prevents "excessive embrittlement and evaporation (burn-out)". But the lower the temperature the less the light output and luminous efficiency. Since AC current drives the lamps in such a way that the temperature spikes at 120 times per second during 60 hertz operation it would be better to operate them at a very much higher frequency or by regulated DC. Direct current desk lamps were a kind of fad a five or six years ago, but they were over driven and used small auto "tail-light" bulbs. It would seem to me a compact and EFFICIENT Direct Current device could be made to drive even 120 volt variety bulbs with MORE radiant efficiency and cooler peak and maybe even average temperatures. +---------------------------------------------------------+--------+ | Paul M. Koloc, President: (301) 445-1075 | FUSION | | Prometheus II, Ltd.; College Park, MD 20740-0222 | this | | {umcp-cs | seismo}!prometheus!pmk; pmk@prometheus.UUCP | decade | +---------------------------------------------------------+--------+
king@kestrel.UUCP (05/24/86)
From: timothym@tekigm2.UUCP (Timothy D Margeson) Newsgroups: net.consumers,net.sci Date: 22 May 86 19:40:27 GMT Reply-To: timothym@tekigm2.UUCP (Timothy D Margeson) Hi, About lightbulbs - Has anyone else besides me measured their line voltage that comes into their house? I measured mine after several of my lights blew, were replaced then blew again in what seemed an abnormally short period of time. My measurment turned up a nominal voltage of 127.5 volts RMS (with a true RMS DVM made by Beckman). I called the power company, Portland General Electric, and I got the reponse "This is the normal voltage we set the lines to, to avoid the chance of brown-outs in the winter time." I just had to ask myself if PGE's motives were more pocketbook oriented. Quick calculations say that power usage will increase as the square of the voltage. What this means is that a lamp rated at 120 volts (when a common line voltage used to be 117 volts RMS) is being run at 127 volts, thereby reducing its life expectantcy to approximately 65 to 76 percent of normal (That's right folks, a 5 percent increase in lamp voltage results in 20 percent increase in light out put and a 30 percent decrease in lamp life). Suspicion is often healthy, but I think misplaced in this case. An increase in house voltage will not increase power consumption significantly in the long run. Induction motors usually consume no more power at a slightly higher voltage than at their nominal (the power factor decreases) and if they do, they are undersized and they put out more power than with the nominal voltage, making (eg.) your refrigerator turn off sooner. Thermostatically controlled heating devices consume no more power at the higher voltage. Flourescant light bulbs consume no more power (again, the power factor decreases). Even incandescant light bulbs will consume no more power at the higher voltage, because PG&E's customers will find themselves installing smaller bulbs. Consumers will run non-thermostatic heating devices such as broilers for a shorter time. Electronic devices might consume a bit more power depending on power supply design. -- Tim Margeson (206)253-5240 tektronix!tekigm2!timothym @@ 'Who said that?' PO Box 3500 d/s C1-937 Vancouver, WA. 98665
jsdy@hadron.UUCP (Joseph S. D. Yao) (08/25/86)
In article <238@prometheus.UUCP> pmk@prometheus.UUCP (Paul M Koloc) writes: > ... It would seem to me a compact and >EFFICIENT Direct Current device could be made to drive even 120 >volt variety bulbs with MORE radiant efficiency and cooler peak >and maybe even average temperatures. Is this an old message spat back by another machine, or is this really coming around again? These devices exist. They're called diodes. Simple (not full-wave) diodes packaged in discs to go at the bases of light bulbs are available from almost all cheap mail order catalogues, or at your corner electric hardware store. The mail order calls them "Light Savers" and charges ~ $2.50 per. [Yes, diodes still spike @ 60/sec; but they do save the bulb life. Maybe the "Light Saver II" has a full-wave rectifier or an LC smoother in it. I've never cracked one; I was told a long time ago what was sposed to be in it.] -- Joe Yao hadron!jsdy@seismo.{CSS.GOV,ARPA,UUCP} jsdy@hadron.COM (not yet domainised)