> =A0There has been some discussion just how efficient so called "White" > LEDs really are as replacements for household lighting compared to CFLs > (which often have inflated claims of brightness and life in retail) or > Florescent tubes. > http://www.theregister.co.uk/2010/08/25/led_save_energy_not/ I read the linked page and gave the PDF the barest of skims - I'll definitely study it in more detail "later". BUT while history appears to be on their side, I don't think reality is. No necessarily convincing reasons, but many relevant factors. We are used to daylight. Full sunlight is 100,00 lux (at 1 standard sun - YMMV) and down to say 10% of that is acceptably bright - so 10,000 lux. BUT the eye has a logarithmic response capability and after a small while we get used to much lower light levels and see them as 'very bright'. The surface of a typical LCD screen at full brightness is ~ 300 lux. We would not expect, need or want all surfaces around us to be that bright. 1 lux =3D 1 lumen/m^2. Based on my own experiences - 5 lux allows discernible colour but is annoying. 10 lux allows good colour distinction but is 'a bit dim'. 20 lux is quite reasonable and most people would accept that. 50 lux is nice and bright and 100 lux is very very acceptable. Published figures of desirable levels often set far higher figures than tha= t. Look at your LCD screen on full and decide. If utterly pushed I could give you LED lighting NOW that delivered 150 l/W (lumen/Watt). That would be hard and uneconomic. I can give you 100-120 l/W with reasonable ease. Commercial products in the 80-100 l/W range are available now. Some which claim this are lower to much lower but this is doable. Lets assume that lighting asymptotes to 150 l/W in the next while. At 100 lux acceptable level =3D 100 l/m^2 you get 1.5 m^2/Watt. A say 15' x 15' room =3D~4.5 x4.5m ~=3D 20 m^2 will require "only" about 14 Watts of 150 l/W lighting to illuminate it to 100 l/W IF you can get the light efficiently onto surfaces. Without careful planning you may need to about double that to say 25 to 30 Watts. That's not much more than a allegedly 100 Watt replacement CFL which are arguably more like 80W incndescent equivalent. A good CFL gives around 70 l/W for cool white and say 50-60 for warm white. Bad ones, of which there are many, give as little as half that. A good straight tube fluorescent can give in excess of 100 l/W BUT it's 360 degree cylindrical radiation pattern with need for reflectors and the propensity of people to feel they needs diffusers means delivered efficiency is noticeably lower. SO - if you could light your rooms to ABOVE comfortably bright, would you. You can do that now, and some few do. But most people are happy to very happy with light levels of 100 l/W. Spot area lighting can boost levels where needed. What this implies is that lighting levels at delivered efficiencies somewhat above what are now given by CFLs or linear tube fluorescents are in the range of future LED lighting. Current best in class LED lighting is about equal to tube fluro or above CFL in actual delivered light. Why will we want to use more light? You could choose to light more areas and things - but advances and dropping prices in electronics make light on demand easier as do LED instant-on features. It is not hard to imagine that most homes in future would have lighting which, when on, drops to a low but acceptable maintenance level and then 'brights up' as people move through the house. That is of course wholly doable now for suitable money. Most people can't be bothered and it will only be fully worthwhile if energy costs increase in real terms. This may yet happen [tm]. I picked 150 l/W as top efficiency as it is somewhere around 50% absolute efficiency depending on color temperature etc. Make your own assumptions. A single Nichia "Raijin" LED (NSPWR60-K1) (so far my favorite LED) will produce 15 lumen from a minuscule 150 mW input. On a 0.7 x 0.7 m work area that will deliver 30 lux mean - extremely acceptable for "western" activities such as reading or craft work. A higher level than m,any 'western' children use for homework etc. A willingness to use such point area lighting could drastically reduce lighting energy use. I have a 20 W CFL above my keyboard and immediate desk area at present. 1 to 3 Watt of LED lighting could easily do an acceptable job in the same role. FWIW I have a 100 Watt CFL in my dining room !!! :-). Not 100W equivalent but 100W input. Probably about 5000 lumen out. Brighter you do not need :-). Russell McMahon On 25 August 2010 23:29, Michael Watterson wrote: > > =A0There has been some discussion just how efficient so called "White" > LEDs really are as replacements for household lighting compared to CFLs > (which often have inflated claims of brightness and life in retail) or > Florescent tubes. > > http://www.theregister.co.uk/2010/08/25/led_save_energy_not/ > > << Federal boffins in the States say that the brave new future in which > today's 'leccy-guzzling lights are replaced by efficient LEDs may not, > in fact, usher in massive energy savings. >> > > This assumes that LEDs actually DO give energy saving for same light outp= ut. > > Yet there may be no energy saving! > > Their conclusion studying 300 years worth of lighting is that as the > cost reduces we light more. So don't save energy. --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .