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replacing CFLs with LEDs

Discussion in 'Environmental Discussion' started by dhanson865, Jul 24, 2013.

  1. 70AARCUDA

    70AARCUDA Active Member

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    ...supposedly, 3-year warranty, but I personally would wonder more about the "life-time" of that built-in fan.
     
  2. dhanson865

    dhanson865 Expert and Devil's advocate

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    amazon review said it was practically inaudible, a fan run at low enough voltage / RPMs can last decades.

    I've got 80mm, 92mm, and 120mm fans that I've been running in PCs for 5-10 years that still work. Some are noisier than when they where new and got rotated out of the PC I care about most but none stopped spinning.
     
  3. 70AARCUDA

    70AARCUDA Active Member

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    You obviously have more faith in such fans than I do. In my prior work, such mechanical devices had a finite life-span which shortened with both vibration and heat proximity...as appears in their illustration. And, obviously, when the *unservicable* fan goes, the whole LED assembly becomes a throw-away device, without any expectation of "repair/replacement."
     
  4. dhanson865

    dhanson865 Expert and Devil's advocate

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    sort of. I agree that the unserviceable nature is a big factor. I wouldn't want pay more than $10 for a light bulb of any kind so this is out my desired price range.

    As to heat, the temp of my 6/7W bulbs in a can light is about 80F from a casual check of my temp gun vs 150F for a CFL in the same can light.

    Also the electrical components (capacitors more than anything) are more temperature sensitive than that fan is and if one of those fails I consider it practically unserviceable as well (cheaper to buy a better quality product than to constantly repair a poorly made one).

    I'm just thinking a fan cooled LED if done right might be just as reliable as a non fan cooled that doesn't have adequate thermal mass / heatsink material like many current under $6 bulbs that are borderline too hot / not enough mass.

    I'd rather it just use less power and be cheaper to boot but I did think it was interesting and I'm not willing to exclude it just because it has a fan.

    bottom line: Price alone keeps me away.

    edit: fixed Amazon URL
     
    #144 dhanson865, Nov 20, 2014
    Last edited: Nov 20, 2014
  5. dhanson865

    dhanson865 Expert and Devil's advocate

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    another thought is that fan is only good if the socket is on the bottom with the light pointing up, airflow would be horrible in a can light. Might explain why one review called it quiet and another called it loud.
     
  6. 70AARCUDA

    70AARCUDA Active Member

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    "Trumpet...ing" due to motor sitting at bottom of a coronet-shaped light fixture?
     
  7. dhanson865

    dhanson865 Expert and Devil's advocate

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    I'm thinking more of a thermal issue than an acoustic issue.

    The intake of the fan is pointed towards the socket and heat rises.

    If the socket is below the bulb (floor lamp, table lamp) then the socket is on the bottom and the fan is exhausting towards the top working with the rising heat.

    If the socket is beside the bulb (ceiling fixture) the rising heat bounces off the ceiling so the issue is how open is the enclosure and how much air exchange is there in general, doesn't matter which way the bulb faces.

    If the socket is above the bulb (can light, desk/swivel facing down) you get a feedback loop with the heat of the bulb rising into the fan intake then being flushed back down to the heat of the bulb and repeating. The fan is fighting against the natural flow of heat and will ramp up faster and faster if thermally controlled. I'm assuming the RPM/voltage of the fan ramps up with temperature.
     
  8. dhanson865

    dhanson865 Expert and Devil's advocate

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    OK so another big user of fluorescent lighting in my house are the old TVs I'm still using.

    Given this power label from the EPA/FTC (you know those lovely yellow/black tags that tell you the power cost of a device)

    11 cents per kWh (actual)
    TV on 5 hours per day (actual)
    yearly usage 64 kWh (they might round this to nearest hWh)
    total cost $7 (they always round the nearest dollar)

    what is the average instantaneous power draw in watts for this TV? What is the simplest formula to work to that number?

    W = 1000 × kWh / h is a given formula

    1000 x 64 kWh / 5 hours = 12,800 (seems high for a TV, maybe I need to multiply the hours out by 365, 365 x 5 = 1825 hours a year)

    1000 x 64 kWh / 1825 hours = 35 watts (seems reasonable but if so my old TV uses 10 times the power at 42" as an new 42")

    assuming that is correct here are the comparisons for the LG LB6300 TV line

    42" : 1000 x 64 kWh / 1825 hours = 35 watts
    47" : 1000 x 70 kWh / 1825 hours = 38 watts
    50" : 1000 x 81 kWh / 1825 hours = 44 watts (not IPS, this size should be avoided for picture quality, power efficiency, and price reasons)
    55" : 1000 x 81 kWh / 1825 hours = 44 watts
    60" : 1000 x 94 kWh / 1825 hours = 52 watts
    65" : 1000 x 137 kWh / 1825 hours = 75 watts


    I don't have the power meter reading handy but I'm thinking my old 42" TV pulls something over 300 watts.

    I also have a couple of 27" CRT tvs in the house (one sees regular use).

    I'm thinking that replacing the Living room TV is a no brainer on the size upgrade desire but that means the hand me down effect of moving the 42" LCD to the spot where the 32" LCD is and the 32" LCD replaces a 27" CRT.

    I guess the next question is can the old LCDs be inefficient enough that getting a new TV could pay for itself. If the new TV saves 70% of the power draw maybe I save $50 a year in power but the 42" TV costs $500 so it'd have to last 10 years.

    So if my math is right I can't justify replacing TVs purely on power savings even if the savings are significant just because the purchase price is significant as well. Of course I live in an area with cheap electricity (think 10 cents a kWh), maybe a different choice for those of you in states with higher power costs.

    Next step then is to give away or sell extremely cheap the 27" CRT TVs that drop off the bottom of my hand me down chain.
     
  9. SageBrush

    SageBrush Senior Member

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    Good 42" TVs are a lot less than $500. Go to slickdeals.com and set up an alert for 'LED TV'
    I recently bought a 55" TCL for $500 shipped that I am very happy with.
    The old TV was not mine to dispose of, but I did recoup $50 on the digital to analog converter box that was no longer needed, and I save its power draw.

    For power draw, divide the annual Wh by 1825
    E.g. 64 kWh annual is 64000/1825 = 35 watts (over a year used 5 hours a day)

    ---
    For cost savings I would first figure out my power savings per device, and say over a week figure out how many hours a day it is on.

    So, e.g,
    Device #1: old watts 300, new 80; 5 hours a day
    Device #2: old watts 200, new 100; 4 hours a day

    Then I know that I am saving 220*5 + 100*4 Wh a day.
     
    #149 SageBrush, Jan 27, 2015
    Last edited: Jan 27, 2015
  10. GregP507

    GregP507 Senior Member

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    Most of the heat released by a light bulb itself is radiant, not convective. Most heat-lamps shine downward. Heat is generated on the surfaces which absorb the radiant heat, and some of that heat is transferred to the surrounding air which is convected upwards. The rest is reflected the other direction, where it strikes something else, and is re-radiated until all of it is eventually absorbed.

    All electric lights produce heat; which is basically the difference between luminous efficiency and 100%. For example, if an incandescent light is 2% efficient, 98% of the energy is converted to heat. An LED light may be 15% efficient, therefore 85% is wasted as heat.

    One thing to remember is that all electric heaters are 100% efficient, despite claims that some types are more efficient than others. Here is an example: mePCjc4c0vjbR3e5MqStcfw.jpg

    I've seen these damned things advertised for more than 20 years as "more efficient" than other electric heaters, a claim which defies basic physics BTW. Originally they were sold on TV for over $800. then in hardware stores for $400, then discount stores for $100. I saw this one on Ebay for $18. Still more expensive than a basic electric heater. There must be a lot of these things to get rid of.
     
    #150 GregP507, Jan 27, 2015
    Last edited: Jan 27, 2015
  11. wjtracy

    wjtracy Senior Member

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    Gee I think any LCD TV is OK.
    The way I look at it, in the winter I am happy my TV makes some heat because fam room is too cold.
     
  12. icarus

    icarus Senior Member

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    All electric heat is 100% efficient...that is if you are referring to resistance electric heat. Heat pumps can BR significantly more that 100% EF depending on design, Delta T etc. A ground source Heat pump can be 125-200% efficient. That is for every BTU used to power the system it can deliver 1.5-2 BTUs to the room. The mini split air source heat pumps are very EF and very reasonably priced. You can even do a DYI install with out having to p urge and charge.

    Icarus
     
  13. fuzzy1

    fuzzy1 Senior Member

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    Not exactly. Electric efficiency calculations shouldn't count the wire losses outside the desired heating space (back at least to the meter, if not farther) any more than combustion heat appliances should be allowed to count the heat dumped out the chimney exhaust.

    But otherwise, the statement is reasonably close to reality. In a properly wired building, any of them will be close to 100%.
    The manufacturer's site doesn't appear to claim greater efficiency than other electrics. Re-sellers are a different matter.

    And if it provides a spot or zone heating boost that allows a central heat system to be turned down, then it can be "more efficient".
    An Energy Star ground source heat pump must be at least 310% - 410% efficient on a certain test, depending on type (open- or closed-loop, water-to-water or -air, etc.)
     
    #153 fuzzy1, Jan 27, 2015
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  14. icarus

    icarus Senior Member

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    ^thanks for the heat pump numbers.

    I don't think line loss outside the building envelope would be enough to change the basic calc. The real issue with electric heat is it takes way more energy at the generating station (plus cumulative line losses) that the appliance generates. Something in my memory says it takes 2 BTUs to get one in the envelope.

    Icarus
     
  15. fuzzy1

    fuzzy1 Senior Member

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    Yes, line loss isn't enough to change the basic calculation, but is just enough to set aside the common 100% efficiency claim. At full production power, my solar system is losing 1.3% just in long wire losses from the PV modules to service meter, not counting extra losses at joints and switch contacts. Many electric heaters in home use will see 1 to 2% in similar losses (for 240V heaters, double that for 120v), depending on the wire run length.

    For other losses, I'm seeing claims that electric distribution system losses are typically 8-15%, or just 6%. A government spreadsheet shows estimated losses near 7% in 1996, dropping closer to 5% in 2012.

    The power plant efficiencies vary sharply by type. I seem to remember big old thermal plants, coal and nukes, being in the low 30% range. Newer coal plants should be better, but still well below the 60%-ish of the best combined cycle natural gas systems. Big hydro plants should be in the 90%-ish range, so reaching 95%.

    Note that with these numbers, the best natural gas electric plants driving the best heat pumps should provide well over twice as much residential heat as the best possible natural gas furnace.
     
    #155 fuzzy1, Jan 28, 2015
    Last edited: Jan 28, 2015
  16. icarus

    icarus Senior Member

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    Thanks,

    That said, I love my 95.6% natural gas combi boiler!

    Icarus
     
  17. SageBrush

    SageBrush Senior Member

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    I agree with the sentiment but my numbers come out different:
    1. A condensing home furnace burning NG has an EF of about 90%
    2. A central NG electric plant might get up to 60% thermo efficiency, and then has ~ 6% line losses and the electricity is consumed in a heat pump that in a cold environment brings in 1.5 - 2.0 heating units for every one consumed. That works out to a range of 1.5*0.6*0.94 to 2.0*0.6*0.94, or 84.6 - 112.8%
    The real issue is that very few households can connect to a grid that has an average thermo efficiency of 60%. Mini-duct+PV+tight_house is much more to my liking, with the grid for back-up.
     
    #157 SageBrush, Jan 28, 2015
    Last edited: Jan 28, 2015
  18. fuzzy1

    fuzzy1 Senior Member

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    The 1.5 - 2.0 factors should be for an air-source system (with R134a or R410 working fluids) in a particularly cold climate. For a climate more closely approximating the HSPF seasonal profile, an Energy Star air source heat pump must bring in at least 2.3* heating units (single package system) or 2.4* units (split system). My mini-split, six years old, is rated 2.9*. Better units were available then, and better still now.

    R744 systems should degrade much less in colder climates, though I have no idea when they'll become readily available.

    Energy Star ground-source systems have higher minimum ratings of 3.1 to 4.1 heating units per unit consumed, though operate in different conditions, e.g. warmer heat source.

    * I'm converting HPSF units to equivalent COP, and hope I'm doing it right:
    HSPF 8.0 = 2.34
    HSPF 8.2 = 2.40
    HSPF 10 = 2.93
    HSPF 11 = 3.22
     
  19. SageBrush

    SageBrush Senior Member

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    ^^ Thanks

    I'd be wary of the Energy Star specs. Not only are the temperatures relatively high, I gather that the unit is operated in its most favorable condition. New England type real world reports I keep reading are 2.0 or less.
     
  20. GregP507

    GregP507 Senior Member

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    Where does the energy from wire losses go? Heat. That's close enough to 100% for me. Even the energy that runs the fan ends up as heat in the room. Same for the faint amber glow glow of light from the quartz tubes; the light is absorbed as heat. If 100% of the electricity being pulled by an electric heater doesn't end up heating the room, I'd like to know where else it goes.

    I don't count wire losses behind the meter, because I don't pay for it (at least not directly).
     
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