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Are light emitting diodes ready for prime time residential lighting? That question is surprisingly controversial. I am not really sure myself about the answer to the general question. I am sure that for low level lighting LEDs entirely rule.
Up to this point in the history of the world there has not been a practical and efficient way to make a small amount of light for a long time. Incandescents are particularly bad for efficiency and life. Electroluminescent were the closest thing pre-LED era but they are an area emitter and are thus hard to shade effectively. They also need high voltage wiring.
The result of this is that the system of vision intended to allow people to function at night is not really used by most people. People can see at levels down to 0.01 lux. Typical residential living spaces are lit to levels between 50 to 100 lux. That is as much as 4 orders of magnitude more than the absolute minimum required.
It may be that we have hit a technological threshold. If low level lighting is more practical then perhaps it will become more common. It is interesting to consider how a hypothetical low level lighting enthusiast would arrange the lighting in a house.
Let us first invent a specification. All living areas should be lit to the level of moonlight on a clear night. One source claims this is .3-1 lux. Brighter would interfere with things like sleep. Darker would mean a longish time to adapt after turning off a light. Tropical moonlight would be a bit bright I think so let's aim for the lower end of .3 lux.
For a 3m X 3m room we would have around 10m2 to illuminate. Lux is lumens per square metre so to hit .3 lux we would need 3 lumens. LEDs with an efficacy of 30 lumens/watt are available so our power budget could assume around 0.1W per lamp. Since this is mostly best case I'll double the assumption to 0.2W. It would likely take 7 of these lamps to light my house. So the total power draw is 1.4W giving us a yearly power consumption of 12 kW/h. That would cost me $0.72CAN a year.
The fixtures could be built in at time of construction. Retrofit would be easy as you would only have to snake in something like alarm wire to power the lights. The lights could be designed to run off the door bell transformer. If instead you ran them off a small sealed lead acid battery charged from a wall wart you could claim that you had established a sort of residential emergency egress lighting system.
The proposed level of lighting would of course mostly serve for navigating through the house. This would still simplify things. Most rooms would not need any ceiling lights and associated switches/wiring. Hallways and stairways would not need three way switched lights.
In general safety would be greater at night. I used to fall over the stool in my kitchen on a semi-regular basis before I installed my always-on counter light. I did get quite good at it but it would be unrealistic to think I would not eventually do it badly. The compact fluorescent that lights my basement stairs sometimes likes to wait just long enough for me to miss the top step before producing light after I turn it on. A little bit of light would help there too.
Our house of the future would probably need some built in higher level lighting. A ceiling mounted light for the dining room table is nice. Vanity lighting for the bathroom mirror is essential to allow the residents to maximize their apparent reproductive fitness. Kitchen counters and the stove would need bright lighting. Pretty much the rest of the lighting inside the house would be provided with lamps.
When one deals with lighting one is dealing with some fairly primal stuff. I always need to turn on the main light in the bathroom before having a bath. I think I am afraid to go in the dark water. Perhaps at some level I am afraid of alligators. When fluorescent lighting become popular people immediately started illuminating work spaces to some almost insane levels. Legend has it that photographers of that era used to have trouble believing the result of their light meter readings. They were seeing outside daylight levels of lighting inside buildings. A decade or so later "de-lamping" became popular when it became fashionable to care about power consumption. My point is that people like it when it is bright indoors and the brighter the better. Perhaps low level lighting as a way of life will never become popular simply because of that.
Here are some interesting/related links;
posted at: 22:37 | path: /ledlight | permanent link to this entry