2013-01-14

Electrical lighting optimisation

The flat I am living in came entirely with cheap 2-foot and 4-foot T8 fluorescent lighting fixtures. Electricals were one of the first aspects I had taken care of, so I had the least work put into it. Later, I started to wonder what alternatives could be used with these fixtures.

T8 Fluorescent Bulbs versus Fitted LED Lamp Replacements
T8 light bulbs are really, really cheap. On the order of MYR 2.80 for a 2-foot (18 W) tube. It turns out that you can get LED replacements for T8 fixtures which consume about half the wattage for the same lumen output, which cost on the order of MYR 42. (Caveat: figures from the UK, we may not have these in Malaysia.) So at the electricity cost of 0.26 MYR/kWh, at usage of 4 hours/day, you're saving about MYR 3.42 / year.

It would take 11.5 years to recover the cost of the LED light. But that's a somewhat naive calculation. Assuming that the T8 system has additional costs, for the ballasts and starter, say of MYR 1 / year, and you do have to replace the bulb once every 5 years, that brings our total cost of T8 hardware over 11 years to MYR 20 - now given those assumptions, it'll only take 6.4 years for your to pay off the cost of an LED lamp replacement.
DIY LED Lamp Replacement?
I did some quick searches, and it seems that you can order bags of white LEDs, of various warmths and beam angles, from China, starting at about MYR 0.06 each, for minimum quantities of a thousand pieces, before shipping. These would each run at 3.0-3.5 V and 15-20 mA, or 0.45-0.70 W. Bear in mind that the effect of stringing them together, and the requirement for further circuitry, would add to costs, as well as power consumption.

Back of the napkin calculation: assuming a 9 W LED lamp is what you want, you're looking at soldering or breadboarding 100-200 LEDs together. Ouch - what a pain. But worth it as a hobby, perhaps. No wonder the commercially produced equivalents are so expensive. On the other hand the cost for LEDs alone should then be on the order of MYR 7-15, which is a lot cheaper than an off-the-shelf 9W LED lamp for a T8 fixture (again, which may not be available in Malaysia).

A techie cousin has also suggested LED strips, but those do not seem price competitive.
Noobish hackery
T8 Fluorescent lights are big, bright, aimless installations. I was wondering about devices for controlling the flow of light, so that instead of a single brightly lit area, I would be able to get many dimly lit areas, from a single lamp.

I was thinking of tubular structures. The first devices that turned up close in function were acrylic light tubes, that they use to transfer daylight from the surface of buildings, into the insides of buildings, such as subway stations. Acrylic tubes refract light, and result in a rather efficient transfer.

If instead you want to reflect light through a tube, your options start to dwindle. Even normal glass mirrors reflect only 90-95% of available light, per bounce, when new. (Side note: I didn't realise that these days, they don't often use mercury on mirrors - instead they're using aluminium or silver, with a few other layers of stuff for bonding the reflective layer.) Besides a glass mirror inner-tube, which is probably not an easy DIY option, flat white paints, and reflective mylar offer high degrees of reflectivity. (Another side note: it turns out that if you search for reflective surfactants on the Internet, the main demand for such stuff is from people growing marijuana at home.)

So, given limited options, being a bored smart-ass on vacation, I walked over to the largest hardware store on my street. I bought some junction connectors, and a 20-foot-long, 4-inch-thich, white PVC pipe, the kind usually used for waste water in Malaysian residences. I soon realised that this would not fit up the stairwell to my flat, so I had to saw it into two. After cleaning the pipes, I waited till nightfall, stuck a 10 W yellow CFL tube down one end of one pipe, and turned it on. I got a big yellow glow at one end, and a dim cast of light on the other. #fail.



I haven't tried painting the insides of the pipes yet - I may later. I am still looking for reflective mylin - the only place I have seen it for sale at a reasonable price around here, is on emergency camping blankets. Techie cousin has suggested chrome paint. I will have to look into that. Meanwhile, I am thinking to saw up the pipes, and to use them for the construction of relatively boring light defusal structures.

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