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Do compact fluorescent lights always make sense?

  1. Mar 21, 2007 #1

    Ivan Seeking

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    It hits me every time that I replace one in the house during the nine months of the year that we run the heater.

    I would imagine that the energy required to make one is significantly higher than for an incandescent bulb. And they don't seem to last as long as they used to. It makes me wonder about the energy break even point by going with CFs.
     
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  3. Mar 21, 2007 #2

    russ_watters

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    Well, the energy required to manufacture them is calculated into the cost of the lamp, so you already have all the info you need. If you buy a 12W lamp for $4 to replace a a $.50 50W incandescent, you need to run it for 710 hours to break even on the initial investment (not counting the net savings in HVAC costs or longevity). At that rate, they make sense even if they last the same amount of time as regular incandescents.

    Several of my downstairs lamps are on for an average of 3-4 hours a night, so those lamps pay back in about 6-8 months.

    I use them everywhere except my downstairs powder room, which is typically occupied for less time than it takes to warm up the lamp.
     
  4. Mar 21, 2007 #3

    Ivan Seeking

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    I don't think it can be treated so simply. How do you directly relate the energy of mnfc to cost? Can we assume that it takes eight times as much energy to make a CF? And what is the energy cost [in watthours] of making the bulbs? How does this compare to the watthour life of the bulb; or I guess more specifically, the energy savings?

    Also, if I am paying to heat my house [literally 75% of the time] anyway, what is the advantage?

    Also, what is the inductance/capacitance of CFs as compared to incandescents? High L or C can result in additional line losses from the supply.

    I keep thinking that for cold weather country, the advantage might wash out when all is considered. Oh yes, and I am interested in the actual energy savings, not the financial cost to me.
     
    Last edited: Mar 21, 2007
  5. Mar 21, 2007 #4

    turbo

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    Your heating system should be designed to produce heat as efficiently as possible and deliver it to where it is needed. Incandescent bulbs produce heat, yes, but they consume about 4x as much power as CFs to produce the equivalent amount of light, and they are probably not optimally-placed to provide heat where you need it. All of our lights that get any significant usage have been converted to CFs. There are a couple of conventional incandescents in the very cold spots (cellar, outside lights and garage), but that's it. It cuts our electricity bill, and it's nice to know that we don't have to air-condition away that waste heat in the summer months.
     
  6. Mar 21, 2007 #5

    brewnog

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    I won't use electricity to heat my house out of principle, because of the low overall efficiency. As a result, I've got CF bulbs everywhere except my bathrooms and cupboards. They're only 79p here anyway.
     
  7. Mar 21, 2007 #6

    FredGarvin

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    The only thing I really think people overlook with CFs is the mercury that is in every bulb. That requires proper disposal which a lot of people do not do. The cost of proper environmental clean up seems to be missing from the cost quotes I see all the time.
     
  8. Mar 21, 2007 #7

    Ivan Seeking

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    Sure, but you use wood heat. And considering that most lights are in the rooms being used, the placement of the bulbs makes sense.
     
  9. Mar 21, 2007 #8

    Ivan Seeking

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    We have the options of wood or electricity. Of course, in the Pacific NW, we have plenty of hydroelectric power.

    What do you use for heat?
     
  10. Mar 21, 2007 #9
    do light fixture manufacturers make different diffusers for CF bulbs?
     
  11. Mar 21, 2007 #10

    Ivan Seeking

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    I had never considered the issue of disposal.

    Line losses due to reactance is a huge issue in industry. Are CFs designed to have the minimum reactance? I would imagine that an incandescent bulb is almost purely resistive.

    I tried to do a quick check of the input capacitance of a CF, but it seems that my tester needs new batteries.

    For the record, I am not down on CFs, in fact we have them all over the house, but these issues have bugged me for a long time. Also, the hidden energy cost of manufacturing can be deceiving since these are produced overseas. And even here in the US, a large factory pays much less for power than you or I do. And, what are the byproducts of manufacturing? Are developing nations dumping toxins into the environment in order to manufacture CFs?
     
    Last edited: Mar 22, 2007
  12. Mar 22, 2007 #11

    russ_watters

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    Because if that wasn't part of the cost of the lamp, the company who manufactured it wouldn't turn a profit.
    No, it has to be less than that since it also takes more labor/time/materials - but the cost is in there.
    What do you use to heat your house? I use propane, so the energy cost is only a little higher for electricity (maybe 20%). If you use natural gas, the difference is more like 50%.

    Also, because of the fact that air conditioning takes more energy than heating, you probably lose as much in the summer as you gain in winter. For most people in the northeast, with gas heat and summer electric bills about equal to their winter heating bills, the balance is tipped toward losing more in the summer.
    Residential users don't pay for power factor....because it isn't significant. (but yes, incandescents are essentially 100% resistive). Also, newer lamps use electronic instead of magnetic ballasts, and they are much better on the reactance: http://en.wikipedia.org/wiki/Electrical_ballast
    It certainly lengthens the payback, but unless you use zero air conditioning and heat your house with electric resistance, the payback is still there. Feel free to play with your own numbers - it is a useful exercise that I do from time to time...
    Energy or pollution? Regardless, besides the obvious reason of it effecting us more directly, I prefer using the money because of the difficulty in translating the energy of electricity into the energy in the resources it came from. Ie, if your electricity is primarily hydro (which it could be, where you live), it is essentially free (in the thermodynamic and pollution sense, not the financial one). But even then, if there was extra hydro power, they'd just sell it to another electric company that makes up their peak load with gas turbines at 50% efficiency or so (this is the fallacy of many "green energy" companies). So it is probably best to just take the fractions of all the types of electricity for the comparison...

    Reconciling all that is extremely complicated.

    Besides, energy is a commodity, so the watts and $$ tend to even out. But if it is the pollution you are worried about, you'll have to do that national energy balance calculation...
     
    Last edited: Mar 22, 2007
  13. Mar 22, 2007 #12

    russ_watters

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    That is a real issue and difficult to evaluate. You don't waste any money or energy by manufacturing in China, but you certainly do create more air pollution.
     
  14. Mar 22, 2007 #13

    brewnog

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    Natural gas central heating and cooker.
     
  15. Mar 22, 2007 #14

    Ivan Seeking

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    That's the problem with estimating the energy for production as well. For example, are they made using dirt cheap energy from coal fired plants in China? And, as an example, if it takes eight times as much energy to make a CF, this might be significant to the perceived energy savings, but we don't see it because the factory gets its powers for pennies on the dollar as compared to the US. Then there is the resulting air pollution.

    It seems to me that mine-to-lamp study is needed. Solar cells once seemed like a win-win, but now we know that a good part of that twenty to thirty year pay-back [actually, its better than that now...more like fifteen years I think for good areas] results from the invested energy. So, pulling numbers from thin air here, maybe for ten years of the thirty years life of a solar panel, the energy "saved" by the consumer was already spent to make the solar cells. Then, throw in a wall full of lead acid batteries that have a relatively short life, and one has to wonder...

    It may be that our situation is somewhat unique - resistive electric heat and almost no need for A/C. But even then, I would rather run nuclear or hydro supplied electric resisitive heat than a green house gas producing source like wood, or propane.
     
    Last edited: Mar 22, 2007
  16. Mar 22, 2007 #15

    AlephZero

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    The correlation between selling price and energy cost to manufacture is probably zero.

    Q: If you could manufacture a incandescent bulb for 10 cents and a long life low energy bulb for 5 cents, what prices would you sell them for?

    A: You would charge more for the low energy bulb, because "green" people would pay more for it. The people who can't afford them will keep buying incandescent bulbs, but that's not a problem, because you make a profit on them as well.

    Has anbody got specific proposals for replacing global capitalism with an alternative system that actually works? I wouldn't bet my own money on that...
     
  17. Mar 22, 2007 #16
    A tree rotting somewhere after it has fallen contributes to green house gas also. Just because you aren't burning it doesn't necessarily mean you are 'saving the planet'.
     
  18. Mar 22, 2007 #17

    turbo

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    Thank you. I burn wood to heat my house, and I burn very dry clean wood at high temperatures. This is carbon that is actively cycling through our environment, not carbon that has been sequestered for millions of years. There is a difference, people. Please start thinking in time-spans that extend beyond today, next month, next year, etc.
     
    Last edited: Mar 22, 2007
  19. Mar 22, 2007 #18

    Ivan Seeking

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    That may be true, but I would also bet that we couldn't possibly heat the country with wood. Why? We couldn't grow the trees fast enough. Also, I have a large stump that is now almost sawdust but that has been here for at least twenty years. I could have burned it in a week. We need buffers.

    I know that if we have a cold winter and have to run entirely on wood, and I'm talking about hardwoods like oak and alder, we can use as much as five cords. That is maximum of about 640 cubic feet of wood, and about 400 cubic feet per winter as an average. That is a lot of wood! That is a lot of carbon. And I know that my three acres of trees cannot produce that much excess wood. That's why we don't use the wood stove any more.
     
    Last edited: Mar 22, 2007
  20. Mar 23, 2007 #19
    Actually that isn't much wood at all Ivan.
    -
    I'm sure we couldn't grow trees fast enough to heat all the indoor space there is to heat in this country throughout the year. I'm not saying that there is. I'm also not saying that wood heat is right for you specifically Ivan. BUT, it is right for some people and it makes sense for them to burn it. Why claim that since it isn't right for you that it isn't right for anyone else? Let those who are able to utilize it do so. Also, concerning 'buffers'. Keeping forested areas cleaned up of dead standing or fallen trees helps prevent forest fires, so burning it gradually for heating is also a buffer.
     
  21. Mar 23, 2007 #20

    turbo

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    Our 10 acres can easily provide enough wood the heat this house. We burned about 3 cords this winter. Ash, oak, birch, and white maple, mostly, but we burned some very dry softwood harvested from dead trees during the warmer periods. We burned perhaps 2-5 gallons of heating oil to maintain the house at a low temperature a couple of time when we were gone for the day. Honestly, I can't tell if the level indicator in the oil tank has actually moved at all. Burning wood not only saves money on fuel, it is a sustainable way to heat our house that helps reduce our dependence on outside energy (not just heating oil, but the electricity required to run the furnace's burner, blower, etc).
     
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