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This discussion relates to Technology Review's article Quantum Leap in Lighting.

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  jmaximus9
  

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  05/13/2009 02:11 AM

  Cost needs leap first

  I don't care how good it works when a standard light bulb can be bought at WalMart for less than a dollar and these cost about $100.  It would take  my lifetime to payback the difference. Also these compact florescent light bulbs do not give off the light they claim, nor do the last as long. So I am skeptically that these bulbs would really last for  40,000 hours.

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    hankejh
    

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    05/13/2009 10:36 AM

    Re: Cost needs leap first

    I agree - these are a total rip off at $40-100.  I have used a broad variety of LED "bulbs" over the past two years - none of them lasted more than a few thousand hours.  They're all crap with wrap-around marketing. 
    
    I've also achieved a warmer light cast by using yellow/orange markers - this worked quite well, but the LEDs eventually die (and not in 40,000 hours - most were dead around 4k hours, some sooner).

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    wookey
    

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    05/13/2009 07:14 PM

    Re: Cost needs leap first

    In fact over 10 years of nightly lighting (say in living room) the difference in running cost between on old incandescent and one of these LED lights is about $400 (at 30cents/kWh which seems like a plausible average price over the next 10 years (at least in the UK - I don't know what expected prices in the US are). So if the bulb really does last for the 14,000 hours in question then you will save $350-odd.
    
    So it really is worth investing in low-power bulbs, even expensive ones like this, in well-used areas. CFLs are nearly as efficient (30-50lumens/watt) and also very cheap so if you don;t like the upfront prices get those instead. But in fact what you really want is the most efficient lights money can buy.

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      Tysto
      

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      05/13/2009 07:50 PM

      Re: Cost needs leap first

      And the cost of replacing a dog every 8-10 years dictates that you buy a tortoise.

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        Shiladie
        

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        05/16/2009 09:30 PM

        Re: Cost needs leap first

        Tysto, what they are commenting on, is that this new light's benefits over other LED lighting schemes, are not benefits over the classic 1$ vacuum bulb.
        This is more like paying 1000$ for a dog that lives a bit longer, or 10$ for a normal dog, yes worth it for some, not for the general public.

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    briang1621
    

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    06/19/2009 10:08 PM

    Re: Cost needs leap first

    Your totally spot on, 95% of consumer look at price verse longevity. Plus anything more than $5 per bulb is just a novelty!
    Brian Glassman

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  mahonj
  

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  05/13/2009 03:46 AM

  No major benefit in efficiency vs CFLs

  They quote an efficiency of 65 L/W for their LEDs.
  They then say that CFLs generate 30 L/W, but CFLs are in the range 50-60 L/w, and so there is no real energy advantage (apart from a good CRI) for a bulb that costs about 20x as much.
  
  They should license the dot technology to the whole LED industry and let other people get the price down.

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    IggyDalrymple
    

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    05/13/2009 08:22 AM

    Re: No major benefit in efficiency vs CFLs

    WalMart sells a bulb that looks like this for a price in the $40s.
    
    My limited experience is that while they are fine for dramatic effects, they won't bathe a room with light like incandescents and CFLs.

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    dconner3905
    

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    05/13/2009 08:43 AM

    Re: No major benefit in efficiency vs CFLs

    I agree 65 lm/W is not very impressive and CFL are better than 30 lm/W.  Cree, Phillips, Nichia all have LED’s that operate at much higher efficiencies, 125+ lm/W and higher.  The other question I have is how much power is the device operating at?  In other words how bright is it?  They show the fins so presumably the array generates some heat, but is that simply because of low efficiency?  
    
    To get a brighter LED, more power is needed and then the whole system (diode, encapsulant, phosphor, and lens) get hotter.  The ability to run hotter for a very long time really has to be in place if this technology is to be successful.  Otherwise too many devices will be needed to get the brightness up and then costs will kill you.   A few years ago 100$/ bulb for 65 lm/W might have actually been competitive with the industry, but they have made some nice strides in recent years.
    
    If this method is heat stable there could also be a competitive advantages over YAG type phosphors since those loose efficiency with temperature.  Thus there is some diminishing returns when running the devices at more and more power.
    
    Interesting technology. 

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    carlp
    

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    05/14/2009 03:26 PM

    Re: No major benefit in efficiency vs CFLs

    If the phosphors in CFL's are really so bad, why not use quantum dots there too?  Answer may be a surface area vs light concentration question if these dots are expensive for some reason.  
    
    I'm very upset by how bad the driver circuitry is in the many LED lamps I have bought is.   No one seems to think it is important to deal with dimmer switches or FET on/off switches, and since every light in any prosperous American home is a FET (in an x10 or photocontrol or motion sensor) now a days, it is annoying that the bulbs don't work at all. 
    
    I've also experience the low life span for LEDs.
    
    But what would really make a great product is an LED light that decided to dim with declining AC power compatible with an incandescent.   This could easily be designed in.  Burning out with low power AC is NOT the right feature. 

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