Metal Halide vs Fluorescent efficiency

[(unknown)]

I enjoyed the article comparing the efficiency of different kinds of lighting but would be curious to see one addition: Metal Halide.

It's my understanding that they produce far more lumens per watt than anything else.  Although they produce a LOT of lumens and use a lot of watts and take forever to come on, especially if they're still hot from being turned off recently.  So they're not useful for in-house lighting.

I use 3 400-watt ones and 8 250's (3.2Kw total) in my 7200 sq ft workshop and there's so much light I almost need shades.  

An unscientific comparison tells me they're much brighter per watt.  In my 1200 sq ft garage (with 12 foot walls -- the workshop has 16 foot walls) I've got 24 F40T12's (by my reckoning, about 1Kw of draw) and the brightness in the big building seems much greater than in the smaller one.  3.2Kw of juice to light 6 times as much floor area (more brightly) as it's taking 960 watts to light in the smaller building.  Assuming the same brightness in both buildings, the fluorescents in the smaller building are using .8 watts per foot and the metal halids are using.44 watts per foot in the bigger building.  Hope I'm doing my math right.  Those numbers look surprisingly small.

After reading the article, I'm going to replace the garage's F40's with T8's, perhaps of lower wattage, since the building is only used for parking cars, and separate the lights onto two circuits/switches so I can just have a few of them running full-time and fire up the rest only when I'm working in there.

Anyway, I'd be curious to see someone who knows what they're talking about (I'm a relative newbie but will post later about some of the many AE projects I've got happening and in the works) do and apples/apples comparison of metal halide vs fluorescent for those of us who need to light large areas.

[richhagen]

I am by no means an expert, but the light output of metal halide lamps varies quite a bit by the design/style of the bulb and the ballast.  Efficiencies of up to 115 lumens per watt are possible, which exceeds the best flourescents at about a hundred lumens per watt, and is beat out only by high pressure sodium.  The light quality of the metal halide lamps is better than the sodium though which is noted for that strong orange 5890 angstrom line in the light output profile.  Since they are an HID light source, they would be best in a space with high enough ceilings or distance, or a special fixture, to spread the light out from the source sufficiently.  Another advantage over most high-efficiency flourescents would be that they are probably less sensitive to the ambient temperature.  Rich Hagen

[desertcoyote]

New Pulse start metal halide light have a CRI-good color rendering index, as good as the new T-5 HPO-high power output fluorescent. If you have a place were the lights are turned on and left one, for say a work day at a time these probably are the best cost/efficiency choice. For applications that require on-off operation the re-strike time of several minutes is not compatible with human beings.

However, For the above reason SCE-southern california edison, and PGE - pacific power and electric are rebating or just outright replacing for free older systems with the high bay T-5 fluorescent systems. The most compelling advantage of the T5-HPO's is that they can be coupled with Motion/Occupancy sensor systems, that well operate at maximum efficiency when nobody is using the space (that is OFF!). Plus California Title 24 energy efficiency requires mandatory-approved lighting control systems most all new commercial construction that requires more than ~0.8W/sqft. LEED certification, light harvesting, auto dimming are all now gaining momentum and will dominate the lighting industry for the new future. Metal halides and their like will be delegated to parking lots and such.