markviii wrote:I am still running Mercury Vapor outside lights because I can't stand the pukey orange light of high pressure sodium. Metal Halide looks like the best alternative, but the 100,000 hr advertised bulb life of the light in the link above has my attention.
The "banning" of mercury vapor lamps and ballasts is another steaming pant load dropped on the public by the enviro-Nazi's. We all know CFL lamps contain mercury, and all other fluorescent lamps do as well - they have to otherwise they wouldn't work. But HID (high intensity discharge) lamps also contain mercury (besides the obvious mercury vapor lamps). A 175 watt mercury lamp contains about 34mg of mercury. A 175 watt pulse start metail halide lamp contains about 30mg of mercury. Even a 150 watt high pressure sodium lamp contains 17mg of mercury.
Now, mercury vapor is the least efficient of the 3 HID lamp types, so one could blither on about CO2 and mercury emissions from coal fired power plants. But on the flip side, it is well documented that mercury vapor street light fixtures (specifically 175 watt lamps) installed in the late 50's through early 60's still have the original lamps installed!!!
If you do the math, that equates to 175,000 hours or more of operation.
Mercury lamps really don't "burn out", but just gradually fade in output. Even still, these high-hour lamps are still producing useful amounts of illumination. The "Big Three" lamp makers (Sylvania, GE, and Westinghouse) soon figured they were making lamps "too good", and soon after started making lamps that would last the rated (24,000 hour) lifetime.
Traditional metal halide lamps have very poor lumen maintenance, although the latest ceramic metal halide lamps are much better, and are available in sizes as small as 20 watts. I've been running a 35 watt lamp on an electronic ballast behind my house for 7 years now averaging about 6 hours per night in an antique "gumball" streetlight fixture
and it's still going strong. The lamp is a 3000K color temperature, so it looks similar to an incandescent lamp which would have been originally installed.
High pressure sodium lamps (that wonderful puke pinkish-orange color) and the associated fixtures in which they are installed are typically very prone to ballast and/or ignitor failure and lamp cycling. HPS lamps maintain lumen output very well, but as they approach end of life, they "cycle". As the lamp ages, the voltage required to keep the arc struck increases beyond what the ballast can supply, and the lamp goes out. As it cools, the ballast and ignitor are busily trying to restrike the arc which causes the ballast to overheat and the ignitors to fail. I've seen many new HPS streetlighting installations that have dead fixtures and cycling lamps within a year. Junk.
I find it a real treat to visit my parents in New Jersey as many areas are still lit with incandescent
streetlights. Most are fixtures installed in the 50's that are little more than the typical "NEMA" yard light head with a simple stamped aluminum reflector shaped in a half-moon or "admiral's hat" look. Slowly they are being replaced, but many still exist. 205 watt "multiple"* lamps are used, rated 12,000 hours, producing 2500 lumens. Yes, they are inefficient, but cheap to maintain with only a photocell and a bulb. Since they use electricity during off-peak times, the consumption isn't a big deal. However, they produce a very nice ambiance at night that in stark contrast to the prison yard look of HPS lighting. Besides, the street in front of my last house was lit with 200 watt HPS lamps (in a 25mph dead-end subdivision!!!
) so the electricity use was the same but it was so bright you could perform brain surgery on the sidewalk....but I digress.
LED technology is really starting to mature as of late. The light color choices have grown to match fluorescents (warm, cool, etc.) and outputs are well over 100 lumens/watt. I can even replace the 250 watt
landing light bulb on my '46 Cessna with an FAA approved LED PAR-46 lamp. Takes current draw from 20A down to about 3 amps and produces more light.
The trick to LEDs is keeping the chip die cool and driving them within their ratings. Overdriving and/or overheating will cause a much more rapid drop in lumen output over time, even losing over 50% in less than 5,000 hours.