Low-voltage halogen an energy saver?
You guys were so smart on my last thread that I’m posting another:
If you’re going for energy efficiency, does low-voltage halogen fixtures count? Hard to talk any of my clients into compact flourescents, and I don’t blame them. The people at energy star are talking about some CFs that actually dim, or dim pretty well, anyway…but it’s still flourescent.
If you count up the wattage of, let’s say four low-voltage heads on a track, at 30watts per head, that could easily replace four line voltage heads with 75 watts per head, so I’m being good to the environment, right? But that doesn’t take into account the energy the tranformer is pulling.
Anyone out there ever calculated this out?
thanks,
Michael
Replies
Transformer efficiency is very high, percentages in the high 90's. You can ignore the transformer. So, Watts are Watts, add them up and compare.
-- J.S.
If you're only considering lumens/watt, halogens are somewhat better than traditional incandescents, but still less efficient than fluorescents. If you're considering quality of life, halogens are way better than fluorescents, IMHO.
Careful lighting design can do a lot to reduce operational costs. Put bright light only where it is necessary, and don't overdo it. For instance, I've seen kitchens lit up like a stage. Put in fewer fixtures, and put them exactly where you need the light -- on the counters -- not where you don't. If you're talking dimmers, that's a hint that you have too many lights with lamps which are too big.
Jamie has it right. Halogen are a touch better than other incandescents (5-10% better) so that's a small factor. TX inefficiency will be 5-10% so it ends up being a wash. What is much more important is good design and choice of lighting fixtures. If 4 x 30 watts of spot lighting does what you need instead of 4 x 75 watts, you are far ahead. Down lights, worklights in the soffit above the cabinets or under the cabinets, and tracklighting can all help you direct light and use it more efficiently. You are trying to illuminate the work area without casting shadows being lighting from behind the people.
Look out for lampshades, tinted glass in fixtures, etc. Those can reduce the light to the room by 40-80%.
I have found I can use fluorscents (compact or 4-foot fixtures) without the objectionable color if I use them indirectly. Such as 4-foot tubes within a soffit that bounces off the wall. So no one and few things in the room see the tube directly.
Also, a mix of fluor. and incand. is easier on the eyes than all fluor.
In my shop, where I don't care about the color, I have two light switches. One for 4 x 60-watt incandescent fixtures which come on instantly. I use them if I am passing through and want quick light. I have six 2x40-watt fluorescent fixtures on the other switch. To make it really bright so I see the work well.David Thomas Overlooking Cook Inlet in Kenai, Alaska
What the others said -- halogen (low voltage or not) is slightly (5-10%) more efficient than regular incandescent, and transformer losses are similarly negligible. The major advantage would come if you were better able to focus the light where it's needed.
In general a halogen (low voltage or not) will enable a spot to more tighly focus the light (due to its smaller size), but you really have to do the numbers with the specs for the specific fixtures to know what's going to happen in a particular situation.
For general area lighting there wouldn't be much difference.
Also, if dimmability is an issue you need to take that into account. Dimming requires special transformers and dimmers, and it's generally not wise to dim halogens too much (below maybe 50-70% intensity).
happy?
The deal on dimming halogens is that it can substantially reduce their life.
Ordinary tungsten/argon/borosilicate lamps burn out because tungsten boils off the filament and condenses on the glass, darkening the glass and making the filament smaller. Eventually you run out of tungsten someplace, and the temperature there runs away, burning thru and arcing.
Tungsten/halogen/quartz lamps are supposed to operate at high enough temps that the tungsten doesn't condense on the quartz. At full voltage, that works. Dim them, and the quartz doesn't get hot enough.
We sometimes -- if time permits and the gaffer knows his stuff -- run halogens that have been dimmed at full brightness for a minute or so before turning them off. That clears the tungsten off the quartz and un-does the damage. But these are lamps that may have four digit price tags, so it can be worth the bother.
-- J.S.
Great technical info. However, it seems like the money saved by dimming would probably be significantly more than the added cost to replace the halogen a little early. Yes?
Advocate
The problem is that the dimmed bulbs darken on the inside and lose efficiency -- even more (relative) efficiency loss than you get from a dimmed incandescent to begin with (which is substantial). So you lose both life and efficiency.
How much darkening occurs, and at what level of dimming it occurs is subject to debate/conjecture, but at least in theory it's a problem.
In general, if you want efficiency then cut bulb wattage, don't dim.
If ignorance is bliss why aren't more people
happy?
Typically I put task lighting on a switch over specific work areas. Flip the switch and the light under just that cabinet/whatever comes on.
A variation I've tried once: Two runs of task lighting on two switches. Gives a faux dimming. Hit one switch to turn on one string of task lights (for the 'low' setting) on all of the work stations, hit both switches to turn on both strings (for 'high' setting).
So I wasn't actually dimming them, it was simply a matter of only turning half of them on per switch.
jt8
"The cynic is one who knows the price of everything and the value of nothing." --Oscar Wilde
> it seems like the money saved by dimming would probably be significantly more than the added cost to replace the halogen a little early
It's not just a little early. I don't remember the exact numbers, but you get something like 20% - 50% of the rated life if the halogen cycle isn't working. I don't have current prices, but some of these lamps were over a grand each in the 1970's.
-- J.S.
Why not compact flourescents? I'm an architect in New York (super high energy costs). I think that we have seen the beginning of the end of the incandescent lamp - it's the SUV of light bulbs using appx 90% of its energy consumption to heat the filaments, halogens are a little better but not much. Flourescents on the other hand last much longer and use much less energy. Everyone is always reluctant to use flourescent light because it is always associated with cheap, cool colored light. If you explain to people that you can use flourescent lamps with a 2800-3000k temp aka warm, (same as incandescent), you cannot tell the difference, except when your electric bills comes. I have found that if you explain light, lamps, and color temperature to every new client and not one wants to incandescent lamps any longer. Whatever you do DO NOT use lamps that simulate "daylight", these lamps look great at noontime, and worse than most cool flourescents at any other time of the day or night.Peter G
We agree about fluorescents, except in regard to colour temperature. A true daylight rendition fluorescent looks great all day long, whereas some of the cheaper "daylight" fluorescents are ghastly as you said. For some people like me, there's actually a profound psychological effect when you see daylight or a close facsimile. Personally I find the "warm" fluorescent colouring to be sickening. The same goes for the appearance of electronic ballast "dimmed" fluorescents- the flicker is perceptible and very off-putting.
For the generation of "mood" for entertaining etc., aside from candles there still is nothing that beats a dimmed halogen bulb. Using the same bulb to generate raw light intensity is short-term thinking- to save the installation of a couple of light fixtures you pay a fortune in electricity to run the lamps later. Planning for a mix is the most sensible.
Why not flourescents? Because they're ugly. Perhaps you can't tell, but I've always been able to tell flourescent light from incandescent. There's no hiding the sharp green spectral spikes from the mercury vapor. Incandescents, whether halogen or argon, produce the kind of black body spectral distribution that our eyes evolved to use.
-- J.S.
I doubt that you can tell the light from a modern full-spectrum compact fluorescent with electronic ballast from incandescent.
Many times when you "sense" fluorescent lighting you're sensing either the flicker or the pattern of lighting from linear lamps. You don't notice these with the modern compact fixtures.
If ignorance is bliss why aren't more people
happy?
I've been an architect choosing, designing and overseeing lighting installations in my work for 20 years and know quite a bit about lighting, lamps, temperature of lamps, color rendering index of lamps, etc........The problem is most people dont know too much about lighting and associate flourescent lamps with cheap cool colored long tube fixtures with a dismal CRI (color rendering index), on buzzing magnetic ballasts.When you use a flourescent or compact florescent fixture w/ a lamp of 2800K± (warm) I seriously doubt you can tell the difference from an incandescent lamp of a similar lumen output. The first thing I do when talking to people about lighting is to explain the difference between warm and cool colored lamps. When people find out they can use lights that can last 5-10 x's longer, use a fraction of the electricity, and look great, they tend to change their thinking on non -incandescent lighting.Peter G
Peter, I've been considering using flourescents (4' units possibly) as the primary lighting in the kitchen of my current project house. My thought was to mount them on top of the cabinets (no soffits) and reflect the light either up against the wall above, or up against the ceiling (8' ceiling in K).
There will be smaller, task lighting in work areas, but I wanted the hidden flourescents to be the primary room lighting.
Do you have recommendations on bulbs and/or fixtures which would fit the bill without making people feel like they're sitting in an office building?
jt8
"The cynic is one who knows the price of everything and the value of nothing." --Oscar Wilde
I was going to let Peter answer since he has so much more experience and knowlege in this area than me. I'm an engineer, but not in the lighting field. Since he hasn't answered yet, I'll get you started.
I recommend warmer fluorescent lamps, with a color temperature 3500K or below. The lower the color temperature the redder or warmer the light.
I also recommend a color rendering index above 80.
Electronic ballasts are the only way to go, in my opinion.
If you follow those three things, you'll be fine. Peter can help you fine tune if you need more detail.
Lamps such as those described above are not carried by the big box stores. You'll have to get them from a good electrical supply house. Expect to pay between $3 and $10 per lamp.
> When you use a flourescent or compact florescent fixture w/ a lamp of 2800K± (warm) I seriously doubt you can tell the difference from an incandescent lamp of a similar lumen output.
I've done exactly that. In a waiting room at Cedars/Sinai Hospital, I noticed a difference between some of the can lights. Sure enough, when I looked up into them, some were PAR incandescents, others were CFL's. Probably it comes from a background in cinematography. But I'm sure most people could learn to see the difference.
-- J.S.
In comparison you can tell because the CFs are generally whiter. Harder to tell without a "reference".
If ignorance is bliss why aren't more people
happy?
In this case they weren't whiter, and sometimes I can tell without a reference. It's kinda like vinyl siding and pergo vs. real wood.
-- J.S.
So you look for the lap joints, eh??
If ignorance is bliss why aren't more people
happy?
John,I'm with you on this. I hate fluorescent light, and can always tell the difference. I keep waiting for lamps that I will like, so I can buy them for my shop and house, but it hasn't happened. Maybe it is the sharp spectral line from the mercury, but they look wrong. Good old black body radiation looks the best.I don't work in a specialized lighting field, except I was a housepainter in my teens. Does that count? LOLBill
I'll bet you that many folks who "hate" fluorescent lighting have been in office buildings where fluorescent cans were employed that they would have sworn were incandescent.
Unfortunately, even though good quality fluorescents are available commercially, they haven't really broken into the home market -- you can't buy the good stuff at HD or Menards, eg.
If ignorance is bliss why aren't more people
happy?
> I don't work in a specialized lighting field, except I was a housepainter in my teens. Does that count?
It could be. Especially if you had to deal with color matching. All this stuff, like interlace flicker, 3-2 pulldown, MPEG mosquito noise, etc. is a matter of learning what to look for.
-- J.S.
For those of us who are not technically savy about lighting, appreciate your being more specific on the lamp of 2800K± (warm). Manufacturer/product name, price range, etc.
Currently building new home and find experience in big box stores quite daunting as there are so many types of bulbs, etc. Lighting stores in this area push the IC canned lights which are not very energy efficient. We will have some of all; just hope all is sufficient??
Just as critical as the K rating of the lamp is the CRI. This is a scale from 0-100. Generally lamps better than 85 or so are hard to tell from incandescent. Your typical "workshop" lamp is around 50. The CRI tells how broad-spectrum the light is. The K tells how "warm" (curiously, with hotter K temps being "cooler").
Unfortunately, as often as not neither the K nor the CRI is listed on the package.
If ignorance is bliss why aren't more people
happy?
> (curiously, with hotter K temps being "cooler").
Higher temps mean more energy. Given that the distribution curve shape stays the same, it has to shift to higher frequencies, which means shorter wavelengths. The red end is long, like 700 nm, the blue end is short, like 400 nm. That's the tech side of it.
Now on the art side of things, red and orange are associated with fire and sunlight, which feel warm. Blues are what you see later in twilight when it's getting cold, on an overcast day, etc. So, the subjective feel is the other way around from the science.
-- J.S.
If ignorance is bliss why aren't more people happy?
I will gracefully bow out but not because ignorance is bliss! Perhaps I was asking too simple a question to anticipate a simple explanation to be shared with others who also are obviously not educated in the lighting world.
Or perhaps you replied to the wrong person?
No doubt, the lighting manufacturers could improve their sales if the K or CRI was identified on packaging so the general public would be more knowledgeable about their products.
It's confusing even to someone who's modestly savy like myself.
Several things going on:
Using fluorescent lighting in other than kitchen/bath/workshop is relatively new (due to energy concerns, and improving fluorescent technology), and the public isn't familiar with it, or the concepts involved.
The CRI is a relatively new concept, and manufacturers are afraid of confusing the public with too much info by putting it on packages or otherwise discussing it. Even degrees K (warm/cool) is a new enough concept in the residential lighting arena that the public is unfamiliar with it. Some people will choose not to buy products with too much technical lingo on the package (though I've noticed a few products packaged with the info in an inobstrusive way that shouldn't scare anyone off).
To add to the confusion/complexity there are a number of new form form factors -- T8, T5, various sprial and U-shaped lamps, etc -- and new considerations relative to the type of ballast -- regular magnetic, high-output magnetic, electronic, etc.
Some manufacturers would prefer to keep the public ignorant of these terms, so that they can continue to use vague terms like "warm", "cool", "daylight", "full spectrum", etc, to push inferior products.
The retail vendors haven't caught on either, and neither sell a complete line of lamps nor provide complete specs on what they do sell.
But the net result is that if you aren't a commercial lighting specialist it can be hard to find the right, good quality fluroescent lighting fixtures and lamps for a given application. And once you have them, obtaining replacement lamps may be a struggle.
If ignorance is bliss why aren't more people
happy?
Actually in the last couple of years I have seen more and more listings of both CRI and color temp.At least on the common tubular tubes. Both on the package sleave and on the shelf label (at least at Lowes).For CFL's it is not as common, but all CFL's that I have seen specs on are have a CRI of 80-85.EFI (http://www.efi.org) has the specs on most of the CFL's that they sell and some of them are available in multiple color temps.For the tubular ones even if they aren't listed on the package you can find them marked on the tube if you know the meaning.You will have a 4 digit color temp followed by a phosporus designation.The SPX series is a CRI in the low 80's. But not everyone uses the same designation. The GE bulb catalog has a cross reference to other trademarks that are equivalent to SPX.As far as the color temp it depends on what you want to do. I have 4100 SPX in my shop and thing that it is a good comprimise.In my office I have Chroma 50's. That is a very high CRI, 5000k bulb. Got them at Wallyworld sold as "Sunlight" bulbs on the outter package, cut Chroma 50's on the tube. Used to be the standard in graphics industries where they did color matching.I like the bright "sunlight like" light.
Have a look here for good info and CRI = 95 lamps:
http://www.kinoflo.com/
-- J.S.