Would it be scientifically valid to rate lamp fixtures (not just the bulbs) by wattage?
I have a theory that people would be happy to buy more efficient lamp fixtures if they knew how much energy some of them waste.
And that the wasted energy would have a measurement, watts, when tested with a few standard bulbs. Just as bulbs now carry a little table of watts, lumens, etc. the fixtures would have watt waste ratings for the most common bulbs they are used with.
For instance, say a generic clear 27w energy star bulb gives off 1850 lumens.
Lets say that’s a “bench measurement” of the “best case”, say a bare bulb suspended in a test box with two power wires touching the contacts.
Some fixtures, such as an open ceramic garage ceiling fixture might test at 1781 lumens, for a loss of 1/27th or 1w.
Another fixture, a recessed can with a non-reflective interior and a thick frosted lens, might conceal 1/3 of the light, for a rating of 9w.
The same test is repeated with a 100w incandescent bulb and the numbers are nearly quadrupled, and the second fixture would rate 33w with that bulb.
So, again, the question is whether that is a scientific way to rate power “consumption” (i.e., waste) of a fixture?
Most of the lamp fixtures I have seen just have wires and a mechanical switch. Where do you think the energy loss is coming from? The only place I can see is the lamp shade.
As an aside lamp fixtures do have wattage ratings. But they are there for fire safety reasons. Do not put a bulb large than 60W or the lamp could overheat and cause a fire.
The maximum bulb size is clearly a different rating than the power consumption of the fixture itself. I hope you see that.
And the power consumed (wasted) is the heat created and absorbed.
Taken to the extreme, a space heater can be produced that consists entirely of bulbs enclosed in a lightproof box. It would release no light and it would have a wattage rating of the full amount of energy consumed.
Also, besides heat given off, a small amount of the energy may be lost to chemical reactions (baking) of the surrounding materials. This is how ceilings get charred when too large a bulb is used. And it’s also the principle of the toy “Easy Bake Oven”
Sorry, slight hijack, but using compact flourescent (sp?) bulbs will cut down greatly on your energy use, saving you scads of money and making the energy lost from the lampshade less of a concern. Also no worries about using a bulb too big for the fixture and potentially starting a fire.
I don’t think so. Too many variables. What shade are you using? What shape bulb?
For example, your recessed can example. Typically, a recessed can uses a focussed spotlight or floodlight type of bulb. Testing it with a standard incandescent would be just wrong. Actually, I’m sort of at a loss to believe that fixtures cause a substantial unintended decrease in light. Certainly a shade will diminish and diffuse a light, but that’s pretty much intentional. Most people aren’t too happy with bare lightbulbs dangling in their homes…
The shade is part of the fixture. They are rated together.
Your can example would be tested with as many kinds of bulbs as are commonly used. If Underwriter Labs thinks they would never be used with a clear bulb, but only a reflector bulb, then that would be the bulb rated. Or, since they like to rate things, they would probably rate both plus a compact fluorescent.
As to your failure to care about the waste, that’s fine. The question is not how to convince people how much waste is enough, but whether the number can be scientifically described so they can decide for themselves.
But…many lamps and fixtures are sold without shades.
You still must make your case that many fixtures are inefficient in their use of light. I frankly don’t see it. As I point out, in your example of recessed cans – * all * the light from the floodlight is directed downwards and there typically is no frosted cover except for the one on the bulb itself. I don’t see a source of great inefficiency. And as you implicitly point out, the style of bulb makes far more difference than the fixture. Replace an incandescent with a fluorescent and you’re likely going to save money. Replace a fixture with another fixture and you’re likely going to end up using the same amount of electricity unless somehow the fixture allows you to use a smaller bulb or fewer of them. But that seems frankly unlikely as most fixtures are added not to give more light, but to give more even light.
Finally, what you’re proposing seems very difficult to do. Let’s take your base case – a bare light bulb. Where are you measuring the light output? If I needed a task light, much of the light given off by the bare bulb would be useless to me. I’d find a fixture that focused the beam where I needed it to be much more useless, even if the lumens at some given spot were less than an equivalently rated “bare” light bulb would generate.
In short, you’d be increasing the complexity of everyone’s life for a barely perceptible benefit.
A fixture is limited to the size (i.e. wattage) of bulb it can accommodate. This is due to a number of reasons. Here are a few:
Heat conducted from lamp into socket materials.
Heat conducted from lamp into wiring insulation.
I[sup]2[/sup]R heat due to resistance of conductors (wiring and conductors in socket).
I[sup]2[/sup]R heat due to contact resistance (interface between bulb and socket).
So how do they come up with a wattage rating for a fixture? I don’t know. I guess one way is to measure the temperature at a bunch of places on/in the fixture, and keep increasing the bulb wattage until one of the temperatures exceeds a safety rating.
Rating a lighting fixture, per se, makes no sense. The fixture does not consume energy during use. However, the design of the fixture may impede efficient light output, but isn’t that the point of the fixture?
The bottom line is the bottom line, and nothing more. If I can save money by using bulbs of a smaller wattage and still find the light output and light quality to my satisfaction, I will do it. Unfortunately I do not have any energy saver bulbs inside my house because all the energy saver bulbs are really fluorescent lights. I have yet to find any energy saver fluorescent lights that match the light quality my color-blind eyes will accept.
Well, if you want people to think hard about one of your questions, you might motivate them by convincing them that it’s any actual problem worth solving.
Anyway, the answer is probably “no”. Wattage just isn’t a good measure of light output. You’ll notice that there are various bulbs out there that advertise things like “60 Watts, but as bright as a normal 75 Watt bulb”. You’d probably need something like lumens/watt or something like that. And for most fixtures, that’s going to be a variable number depending on where you are in relation to the fixture. At best you could probably say something like “If you put a typical 100 Watt bulb in this fixture, you’re going to think it’s a 92.3 Watt bulb, the shade is so dim.”
Bottom line, you’re going to save more energy if you stop worrying about the fixtures and just turn off the light when you leave the room like Dad always said to.
The fixture does consume energy during use. That’s the whole point, not whether it uses energy, but what’s the correct way to describe it.
No, the point of a fixture is never to reduce the light output. Who would intentionally buy something to reduce output? You’re saying that if you had a choice of two lamps, externally identical, but one gave off less light for the same amount of electricity that you would prefer that one? I find that odd. But you know what, the question is not whether I can convince you to save. I’m sure you would never intentionally buy something to save money, or energy. The question is (and I repeat for those who seem to have forgotten):“the question is whether that is a scientific way to rate power “consumption” (i.e., waste) of a fixture?”
The point of a fixture is often to reduce the light output. Unless you decorate by hanging bare 60 Watt bulbs in your apartment. You place a shade on a lamp to diffuse the otherwise overly harsh light from the bulb. Unavoidably, some of this light is lost to being absorbed by the shade and emitted as heat. Nonetheless, it’s a tradeoff virtually everyone who owns a lamp has made.
Yeah, fine, as snidely as you asked it, here’s how to rate your power consumption. Place your fixture in a very large transparentcalorimeter. Measure the energy you’re putting into your lamp and the resulting temperature of the fixture. Any light that’s absorbed by the fixture rather than leaving the transparent calorimeter will show up as heat. It might even be a detectable amount of heat compared to the heat generated by the inefficiency of the electricity-to-light conversion if it’s a bright enough light. Compare multiple fixtures. The one that generates the least heat wins. Don’t run the experiment very long – the interior of the calorimeter is going to get catastrophically hot pretty quickly, destroying your fixture and your bulb.
Caveats: I’m not sure whether the differing mass of different fixtures is going to cause a problem. You have to make sure your calorimeter is transparent to all frequencies that the fixture operates in, but still insulates. I assume a double-walled thermos of glass with a vacuum inside would do the job. But you’ll need a physicist to say for sure.
An alternative mechanism is to measure every photon generated by the fixture and compare it to the energy input. Unless you have just a whole bunch of photodiodes handy, this isn’t going to work.
I think I know where you’re coming from, pocelene. Given that both optical and electrical power can be measured in the same units (Watts), you’d think it should be easy enough to come up with an efficiency figure that is simply given by the equation
Light Power/Electrical Power.
The complications arise from the distribution of the light. Each different model of lampshade throws the light into a unique distribution, and the optical power measured drops relative to the distance to the light source in an inverse-square law kind of way, so the distance of measurement would need to be specified for any figures given. Also the light distribution is not always uniform.
Some standards have evolved over the years to measure light output, as for commercial concerns efficiency is key. You can measure light output in foot-candles (fc), lux (lx), watt per meter square (W/m2) and micromole per meter square per second (m mol m2 s). The last seemingly clumsy spec is for greenhouse lighting, and refers to the photosynthetically active radiation (PAR) in the 400nm to 700nm range. The human eye sees from about 380nm to 780nm, so if you’re talking about optical efficiency you have to do something similar to the greenhouse lamp PAR rating and only measure the wanted spectrum. The lamp may be emitting a lot of optical power in the infra-red and/or ultra-violet ranges, and you can essentially look at this as wasted power if you only want light to see by. Likewise, any visible light in a UV or IR lamp can also be considered to be waste power.
Most household lampshades and reflectors are quite inefficient - they’re designed to look nice. There are efficient reflectors out there, used for industrial purposes like floodlighting or greenhouse lighting. They don’t look very nice.
pocelene’s basic premise is sound, it’s just that it’s complicated to measure, too complicated for most users to understand a specification if it was given, and most domestic users don’t care anyway. And given the abuses by marketing monkeys about stating loudspeaker and audio amplifier powers, I wouldn’t trust them not to massage the efficiency figures of lamp reflectors if they had to give them.
I really like the concept of a ratio. An efficiency (waste) ratio, as it were.
And ratios can be expressed in percents, which are easy to calculate with.
That would could then be supplemented with a couple of examples.
Perhaps it would say: “Lamp Efficiency rating is 75% - with a 100w lamp you get the same light as a bare 75w bulb.”
There would undoubtedly be a second or third such line for other recommended classes of bulbs.
“Lamp Efficiency rating for a compact fluorescent is 68% - with a 27w lamp you get the same light as a bare 18w bulb.”
[ aside re the side issues you brought up]
Q: Why anybody should even dare to attempt to actually do the measurements, because it will just be ignored by the uncaring masses? A: Those same uncaring masses have created a huge compact fluorescent bulb section in every hardware store in the country.
Q: What good is knowing that an ugly fixture is more efficient than a pretty one? A: There are plenty of fixtures that are both ugly and inefficient. And also those that look nearly identical, but are more efficient. They already make these. They usually have a reflective surface somewhere. For example, a desk lamp with a black interior will get much hotter and require a larger bulb than one with a shiny interior. Both types actually, currently, do, in fact, exist, right now, today, at a lamp store near you. That’s the comparison that people could judge with a number, if the number were available. The people who already buy all those energy star appliances today. And certainly ALL interior designers picking out a few tens of thousands of identical lamps for a new Vegas hotel.
Q: How can we prevent hucksters from distorting the results. Presumably, if the numbers were computed by the same folks who already give us a fluorescent’s “equivalent wattage”, the numbers would be equally as valuable. Let Underwriters Laboratory put its seal on them.
Re: Measurement for non-uniform fields is too hard to be solved by modern science. First, they presumably already have such equipment to measure the lumens given off by non-uniform floodlights, spotlights, and other reflector bulbs.
And if they don’t have it already, it’s not much of a challenge to make such a tool. It’s not rocket science. A primitive method is to suspend the lamp inside a box lined with mirrors. Place a photographer’s light meter in a hole at one end of the box. Compare the number to that given off by a various bare bulbs of different wattages. There are no calculations, just reading a meter. I’m sure there are fancier refinements possible, such as using parabolic reflectors to aim the light, but I think the simple box will give all the measurements needed for consumer information.
[end of aside]