Fluorescent vs Incandescent lights
Glen Turner writes about silly people who think that fluorescent lights don’t save energy over their lifetime [1].
A compact fluorescent light (one that is designed for the same socket as an incandescent globe) is not the most efficient light source, the Luminous Efficiency page on Wikipedia [2] lists a CFL as having an efficiency of between 6.6% and 8.8% while fluorescent tubes can be up to 15.2% efficient and low pressure sodium lamps are 27% efficient! But given that low pressure sodium lights are unsuitable for most uses due to being monochromatic and having a long warm-up time and the fact that fluorescent tubes are often not suitable due to design an 8.8% efficiency is pretty good. LEDs can give up to 10.2% (and prototypes offer 22%) but don’t seem to be available in a convenient and reliable manner (they are expensive and the ones I’ve tried have been unreliable).
When comparing fluorescent with incandescent one factor to consider is the power used. While high-temperature incandescent lights are quoted as having 5.1% efficiency and a 100W 110V tungsten incandescent globe is quoted as having 2.6% efficiency a 40W 110V globe will only have 1.9%. If you want to save energy then you probably don’t want to use 100W globes, using less light is the first way of saving energy on lighting! So the efficiency of incandescent lights used for the comparison should probably be closer to 1.9% than 2.6%.
Now the theoretical performance won’t always match what you get when you buy globes. There is some variation of quality between manufacturers and there are at least two distinct “colours” of fluorescent lights (one is about 5800K - similar to our sun, the other is something over 8000K - blue-white), I expect some difference in efficiency between lights of different colour range.
I see CFL lights marketed as being 5 times more efficient than incandescent lights, my observation is that they appear to be about 4 times more efficient (IE I replace a 40W incandescent with a 10W CFL or a 60W incandescent with a 14W CFL). Glen claims that an 8W CFL can replace a 60W incandescent globe, the only possibility of getting a factor of 7 or more efficiency improvement (according to the data on the Wikipedia page) would be to replace some 5W incandescent globes with CFL. In my experience (converting two houses that I lived in to CFL and the conversions of some friends) such an efficiency benefit is not possible on direct electricity use.
However in a hot climate any waste heat needs to be removed with an air-conditioner. So when a 60W incandescent light is replaced by a 14W CFL there is 46W of waste heat removed, with an ideal efficiency of a heat-pump it would take 15W to remove that heat from a building (and possibly more if it’s a large building). So in summer we are not comparing 60W to 14W, it’s more like 75W to 14W.
The issue of economics that Glen raises is more complex than it seems because governments often give companies significant discounts on electricity costs, EG in Australia aluminium refineries are subsidies heavily so they pay much less than home users. So hypothetically it could be possible to manufacture a device made entirely of aluminium which saves electricity (and therefore money for the user) but not enough to cover the electricity used in aluminium refining. However when we consider the margins of the various middle-men it seems quite unlikely that such a hypothetical situation could actually happen.
As for the issue of mercury in fluorescent lights there are two things to consider. One is that it is possible to recycle mercury (in Australia at least), the other is that coal fired power plants have a lot of mercury in their smoke…
If incandescent bulbs had not changed in the past decade or two, I’d gladly switch to CFLs. However, several brands of incandescent bulbs started introducing variants with more “natural” light. We switched our entire house over to GE’s “Reveal” bulbs; I’ve also seen a few good recommendations for Sylvania’s “Daylight” bulbs. We’ve tried various kinds of CFLs, and none of them put out light of sufficient quality to compete with these. Until they do, we won’t switch.
January 3rd, 2008 at 8:35 am(Hmmm. I just noticed that Sylvania offers a Daylight CFL; I haven’t seen that in the store before. I may give that a try.)
January 3rd, 2008 at 8:38 amhttp://farragut.flameeyes.is-a-geek.org/articles/2008/01/01/talking-about-lights
http://farragut.flameeyes.is-a-geek.org/articles/2007/08/12/mirror-lights
Diego “Flameeyes” Pettenò has some interesting posts about this topic, see the above two URLs.
January 4th, 2008 at 10:45 amThere’s a serious problem with all CFL lights and that is that they have a spiky spectrum that can’t match sunlight–even if you filter it. On the other hand, incandescent lights have a smooth spectrum that can be matched to sunlight when you filter it (see high end incandescents such as Solux). Two lights can be matched to the same color temperature and white points while still having different spectra (this is because these are summary numbers and don’t tell you that much about the actual distribution w.r.t. wavelength). So you could have two equally “white” lights that each make colored objects appear different than the other. And only incandescents can have the spectrum matched to sunlight–that means you’re losing out on color reproduction compared to natural light if you use CFLs or other lights. Considering that studies have shown correlation between natural light and productivity and health (I can give references), I’d tell anyone considering switching to CFLs to think again.
June 16th, 2008 at 4:48 pmBorislav: Please cite references.
I expect that the correlation between pollution free air and health is considerably stronger than the correlation between natural light and health.
June 16th, 2008 at 5:48 pmhttp://www.coe.uga.edu/sdpl/research/daylightingstudy.pdf
I quote:
“Using multivariate linear regression analysis, the study examined 21,000 school records from 3 school districts in 3 states and daylighting conditions in over 2,000 classrooms. Data indicate students with the most classroom daylighting progressed 20 percent faster on math tests and 26 percent on reading tests in one year than those with the least. Similarly, students with the largest windows progressed 15 percent faster in math and 23 percent faster in reading than those with the least.”
That’s just for the productivity.
For health, just consider the references cited at en.wikipedia.org/wiki/Light_therapy and the notes about studies where artifical light wasn’t as beneficial (since photons are photons are photons, the only difference between daylight and a given light source is the spectrum–thus to reproduce sunlight you just need to match its spectrum).
ebte, you forget that carbon dioxide is not pollution–it’s a greenhouse gas, but even if you double CO2 concentration in the air, that has no direct impact on health due to the increased CO2 getting in your lungs; it’s not toxic, and is therefore NOT pollution.
The only serious pollution one gets for electricity generation is burning coal, but that just says coal is a polluting energy source, not that using more electricity necessarily causes pollution!
There’s also a detailed discussion on other CFL problems by an electrical engineer I respect here: sound.westhost.com/articles/incandescent.htm
I haven’t even started talking about the radio-interference from the CFL power supplies polluting the spectrum and interfering with anyone trying to listen to shortwave radio, as well as ham radio services, but I realize that’s a problem for a niche, so I won’t go into it.
The point is that in terms of energy efficiency, what we should be doing is finding more clean energy rather than taking away from technological progress and comfort/convenience–increased efficiency is never free and forces a compromise.
P.S. I live in Vancouver and it’s cloudy and sunless for at least six months of the year here, so proper light is all the more important here. Add to that that nine months of the year the house is being heated, so any ‘waste’ from indoor appliances is used up and thus they are all 100% efficient.
I’ve had this whole argument already on another forum, when I was startled to hear that the Canadian government decided to ban incandescent bulbs… insanity–if people should choose they want to save energy, that’s fine, but it’s not the place of a nanny state to force people to do so. http://www.head-fi.org/forums/f11/incandescent-bulb-ban-233906
June 16th, 2008 at 6:09 pmBorislav: That’s a good reference to support the claim that sunlight is better than artificial light. But it doesn’t seem to support the claim that incandescent light is better than fluorescent light (if I missed something please cite the page number).
http://en.wikipedia.org/wiki/Full-spectrum
The next issue is how the efficiency and price of Full Spectrum fluorescent lights (as described in the above page) compares to regular fluorescent lights.
Both coal and nuclear power are polluting energy sources. Once we replace all coal and nuclear power plants with renewable energy then we can look at other health measures related to energy use.
The westhost.com article is very partisan in favor of incandescent. For example it cites the heat problems of enclosed light fittings for CFLs but doesn’t note the fire risk of halogen down-lights and incandescent lights in sealed fittings.
I agree that getting clean energy is the best thing to do. It’s a pity that the coal, oil, and nuclear industries are so effective at preventing that. I also agree that “waste heat” is not a problem in winter. I use my old incandescent globes in winter.
Also I think that taxing products you want to deprecate rather than banning them is the best thing to do.
June 16th, 2008 at 10:54 pmThe difference between the lights insists on the variance in color. It will also deploy electromagnet charges to determine the 200MPA that will eventually mount to a glass chamber which in turn decreases voltage.
July 31st, 2008 at 2:13 pmetbe, it was addressed in my first post here: an incandescent has a continuous spectrum, which means that in practice it can be filtered to match sunlight _exactly_. You cannot do this with the spiky spectrum of a CFL because there are no sufficiently narrowband filters in existence (and also since most energy is concentrated in the spikes, you’d be losing way more efficiency).
July 31st, 2008 at 4:29 pmBorislav: The difference between sunlight and artificial light is not limited to the spectrum. Sunlight comes from a single source in the sky, it varies in intensity through the course of the day.
I believe that fluorescent lights can be constructed with a range of different compounds used in the fluorescent paint to give a range of light frequencies. The question is how much of a range is really required. I find it difficult to believe that exactly matching the frequency range of the sun is necessary for health - if there was I’m sure that someone would have determined the optimum latitude for healthy living by now.
July 31st, 2008 at 8:34 pmThis isn’t just about matching exactly, it’s not even close. The spectrum of a fluorescent is a polar opposite of the smooth spectrum of natural light. Typical fluorescent: http://commons.wikimedia.org/wiki/Image:Fluorescent_lighting_spectrum_peaks_labelled.gif
August 1st, 2008 at 3:19 amAlso note that your hypothesis that source location does not fit in with the productivity study I mentioned, since that’s dealing with light coming in from windows which bias the direction, then reflected diffusely around by walls, etc. Moreover, even outdoors all the irradiance does not come directly from the sun, since a very large portion of light is scattered and comes from all directions of the hemisphere of the sky (the sky is much dimmer than the sun’s apparent disk, but it also has an enormous half-angle in comparison). Direction of the light is basically a non-issue.
Er, I meant solid angle, not half angle… that’ll teach me to post before my morning coffee -.-
August 1st, 2008 at 3:20 am