Monday, January 28, 2013

LED Surface Mount Light Energy Savings At True Brightness Ratings

Versus point-source lighting, there is a  beneficial shape factor of about two, for naturally-directional LED illumination. I have proven this in side-by-side comparison tests. It is explained here:
This link leads to download of a Word document. If you prefer, view it online, attributed to Firefly, as PDF.

Since about half of the illumination from an LED chip array is lost in shaping as a point-source "bulb", there will be little use in the future for fixtures that present light as a point source. Directional light, then rated for illumination  brightness rather than omni-directional lumens, will always be more efficient. It is the presentation of the light that matters, and there will be surface mount LEDs fed through A19 and other sockets, upon light cans and other fixtures.

At end of January, 2013, I recognize two good LED plate lights, produced by Lighting Science Group, as product Glimpse. Let us compare operating costs of Glimpse, and other currently-available lighting,  unitized to Brightness Number 4, that of the old 100 watt incandescent light bulb. That is, for illumination other than B4, multiply costs and savings by the ratio (4/ Brightness number), for same-basis comparison. Where illumination from a given source location is increased, fewer neighboring lights are needed, or productivity improves in direct proportion. If you want that "100 watts", and a Glimpse light is brighter, you might dim it, without waste of energy in the dimming.

Here is a Table of luminaire cost and savings comparisons, adjusted to a common basis at B4, except that there is further economy in installation cost of surface mount LEDs. The table displays dollar value and greater carbon savings, taking credit for a brightness advantage of surface mount LEDs, vs. all light in bulb form. The listed CFL is not dimmable, and gives dreary light. I think its lifespan is very overrated. Surface mount LEDs do win over CFLs on lifetime cost. Bulbs that fail have additional cost disadvantage in matters of safety while dead or in replacement. Aren't we happy to now have mufflers that last the life of a car?

(The table has been updated 6/6/2013 to include important Sylvania LED Disk Lights.)

Well, now, how do those savings numbers compare to listings on packaging?

Package math is for electricity only, and credits the T91 as equal to a 75 watt incandescent. Savings:
 35,000 * 0.11 * (75 - 14.5 )/ 1000 = $233.

I don't understand the sloppy math of this packaging.

Let me re-do my math of this T91, for electricity only, with brightness as of a 167 watt bulb:
35,000 * 0.11 * (167 - 14.5)/ 1000 = $587. There is more at issue here, than how to do math.

Package math is for electricity only, and credits 100 watt equivalence. Savings:
 10,000 * 0.11 * (100 - 23 )/ 1000 = $85.
This isn't error. It is permitted propaganda.

Who is responsible for not standing up against deception? 

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