Friday, November 26, 2010
Cool Technology of the Week
I've written about my goal to be as low impact as I can be over the rest of my life, eventually retiring to a small, green engineered cabin in the woods and taking inspiration from early architectural innovators.
To support that goal, I'm always learning about new technologies that support green living.
In February I wrote about innovative lighting using LEDs. Since then, I've learned a great deal about building codes, efficiency measures, and physics. Here's how to be an intelligent consumer of emerging LED lighting technology.
You'll find that LED bulbs from Sylvania, Philips, and EcoSmart are sold based on wattage i.e. it's a replacement for a 40W bulb.
That really does not mean anything.
The amount of light produced for the wattage consumed is the measure of interest.
The "40W" LED bulbs produced by Sylvania in February produced 350 lumens of light using 8 watts of power. The current Sylvania bulbs produce 450 lumens of light using 8 watts of power. How does that compare to an incandescent? A typical incandescent 40 watt bulb produces 500 lumens of light. How about compact fluorescents? A typical compact fluorescent equivalent to a 40W incandescent bulb produces 450 lumens of light using 9 watts of power.
How do we evaluate the lighting efficiency of these bulbs? The right measure is lumens/watt (lm/w)
Incandescent - 500lm/40w = 12.5 lm/w
Compact Fluorescent - 450lm/9w = 50 lm/w
First generation LED 350lm/8w = 43.75 lm/w
Second generation LED 450lm/8w = 56.25 lm/w
Just announced LED products include a downlight with 1439 lumens at 82 lm/w and a new LED "60W" bulb with 810 lumens at 67.5 lm/w.
With LEDs producing more light and less heat for less energy than compact fluorescents without mercury or other toxic concerns, they are clearly the future. Also, the bulb life of LEDs is 25,000 hours. Compact fluorescents typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps have a lifespan of 750 hours or 1,000 hours.
The only issue is acquisition cost of LEDs, since total cost of ownership based on energy savings and bulb life has a reasonable return on investment. Current industry predictions are that LEDs will match the cost of compact fluorescents within 2 years.
All of this is good news for compliance with the 2009 International Energy Conservation Code (which I'll follow for my cabin in the woods). It requires:
60 lm/w for bulbs over 40W
50 lm/w for bulbs 16W to 40W
40 lm/w for bulbs 15W and under
The LEDs coming into the marketplace now accomplish this nicely. Lighting an entire house with 100 watts of power- that's cool!
Posted by John Halamka at 3:00 AM