Frugal lighting

[nicksanspam]

This morning I put two $20 Kill-a-Watt meters on two power strips with a 100 W bulb screwed into one plug socket 80 cm from a "100 W equivalent"

23 W 10,000-hour Commercial Electric compact fluorescent with a 9-year guarantee ($8.97 for 4 from Home Depot) and compared the outputs with a Bunsen grease-spot photometer (a drop of oil on a piece of white paper :-)

Robert Bunsen (1811-1899) also invented the Bunsen burner. He was known as an inept experimentalist with radical theories who isolated a foul-smelling compound which he named cacodyl oxide and a whole series of related compounds which turned out to be highly explosive. At one point, Bunsen accidentally blew up his lab and was laid up in bed for a long time.

The grease spot disappeared (indicating equal illumination on both sides) when the paper was 42.4 cm from the incandescent bulb, so it had (42.4/(80-42.4))^2 = 1.27 times the CF light output. After a minute or so, the 100 watt bulb consumption dropped from 100 to 99 watts and the CF rose from 22 to 24, so the CF was 99/(1.27x24) = 3.24 times more efficient, with 3.24 times more lumens per watt.

After warmup, a "150 W equivalent" 42 W CF ($5.97 from Home Depot) used

35 watts and made the spot disappear 36.2 cm from the 100 W bulb when it drew 98 watts, so it was (36.2/(80-36.2))^2 = 0.683 times brighter than the CF, which was 98/(0.683x35) = 4.10 times more efficient.

Nick

[Stubby]

[Joseph Meehan]

Good Job.

[Harry Chickpea]

Nick, this is much more useful than a lot of your pie in the sky calculations. Well done.

BTW, if the CFs were in a pack of four, did you test for variations? That would be useful information as well.

Also, did you check the lumen output either by using a standard candle, or a photometer (perhaps one in a camera?). Incandescent lamps dim with age, so using an older 100 watt lamp might have affected the results.

[Mary Fisher]

He might have been inept but his name has lasted longer than many who were ept :-)

How many of his critics' inventions are still used?

Mary

[William P.N. Smith]

Many Thanks!

[m Ransley]

How did you measure 42.4cm from the bulb, or is that like R 3 aluminum foil..........

[nicksanspam]

I lined up the center of each bulb on the 0 and 80 cm marks on a Craftsman 939675 8m/26' measuring tape, then moved the paper along the tape until the grease spot disappeared at 42.4 cm.

Nick

[Derek Broughton]

This part may not have been vital - but it's the sort of thing I love to know :-)

I'm sure many of his calculations are useful to people who want to be frugal - but I'm stunned that Nick managed this without a line of Basic code :-)

The numbers are interesting - the 23W CF really was approximately 23W but the 42W CF was much less. I'm not at all surprised that the 23W bulbs really aren't 100W-equivalent - typical marketing hype - but those results are acceptable to me.

Don't CFs dim with age? Can we then expect the relative efficiency to improve over time?

[danny burstein]

In Derek Broughton writes: [ various snippages ]

- also, keep in mind that the lumen ratings for traditional fluorescents are the initial output, but... it's _after_ 100 hours of burn in.

When first lit, they tend to be a modest amount brighter than spec. There's a rapid 'burn off" (for want of a better description, and then, at a nominal 100 hrs, they stabilize (to a slight long term downward slope).

So if you used brand new CFLs, you're seeing a bit of an artificial peaking...

[nicksanspam]

Surprising...

No. I'm not sure how standard standard candles are. I've used CSA standard fingers...

I believe they do.

I doubt that. Don Klipstein might help here.

Nick

[yourname]

I think they dim cause the mercury sticks somewhere or soemthing, but no current drop I would think

[cnctutwiler]

//

Tut writes:

Nick, if you replace one of the lamps with a burning candle, you can calculate the strength of the each lamp in candles vs lamp wattage.

E=C/d^2--------> C1/d1^2=C2/d2^2

where: E=foot-candles C1= one candle C2= candles of light source d1= distance to oil drop for burning candle d2= distance to oil drop of lamp under test

[<usenet2006]

I almost read that as meaning "the grease spot" that was left on the floor where Robert Bunsen was standing at the moment of the lab explosion.

[Don K]

Yeah, I&#39;ve got some of those 100W equivalent, $8.97 bulbs, with a 9-year guarantee too.

I don&#39;t need a grease-spot photometer to tell me they don&#39;t put out as much light as a 100W bulb. My own eyes can tell me that. It takes a

150W equivalent to be a 100W equivalent, IMO.

The one in the hallway went out after about a year and a half to two years. I don&#39;t know where my receipt is, so I guess I&#39;m out a few bucks.

These CFL&#39;s sure are frugal. Just make sure you send in any rebates and keep track of your receipts and the packing material for the next 9 years.

Don

[nicksanspam]

It worked out to 79%, but still an energy bargain.

Maybe not. These bulbs have a phone number [phone] and a date code V# xxxxx printed on the base. I called the number and gave them the code and they sent me a new one, after one died.

Nick

[Mary Fisher]

I think that too.

We pencil the installed date and the supplier on the item itself. We&#39;ve only twice had to return them and they&#39;ve been replaced with no receipt and no question.

Customer goodwill is important to stores. The items are cheap and it&#39;s recognised that some will fail.

Mary

[You]

No, not typically. Very few Gas Discharge lights dim with age unless the excitation voltage drops significantly. The Gas doesn&#39;t wear out, but the electronics that fire the voltage may.....

No, again not typically. Very few electronic systems get better as the components age, so efficency should slowly drop a bit with age....

[nicksanspam]

IIRC, most do.

Nick

[Mary Fisher]

In my experience they do.

Mary