Monday, October 4, 2010

A New Hope

If you recall my award winning blog post, "The end of the EZ Bake oven" about the evils of compact Fluorescent (CF) bulbs, things looked pretty beak at the end.

However "there is another". In fact there are several others. According to the article quoted in my last post:
General Electric Corp., the world’s largest maker of traditional bulbs, said that by 2010, it hoped to have on the market a new high-efficiency incandescent bulb that will be four times as efficient as today’s 125-year-old technology. It said that such bulbs would closely rival fluorescent bulbs for efficiency, with no mercury.
How can you improve on what is essentially a piece of wire? Well, according to this article, the filament can be pitted with a laser to make it more efficient. Additionally, reflective coatings inside the bulb can direct infrared photons back to the filament, requiring less energy to keep it hot. Well, here it is, the end of 2010 and we haven't seen these bulbs hit the streets, but there are other promising technologies.

Plasma bulbs have very high efficiencies, approaching 14%, but it is difficult to make them operate at low enough power to operate in the home. For instance, the lowest power plasma bulbs made are 100 watts, which in light output is like a 1000 watt incandescent bulb! In addition plasma bulbs require quite a bit of electronics to operate. The bulb is essentially a microwave oven, heating a noble gas until it becomes a plasma.

Most other technologies have bigger problems that make them unsuitable. The two really promising technologies in development right now are LED and OLED lamps. Note that these are "lamps" and not "bulbs", since they are solid, not hollow. Despite the fact that both have "LED" in their name, they are quite different in many respects.

An LED, or Light Emitting Diode is, well, a diode that emits light. A diode is a device that passes an electric current in one direction only. Because of the nature of semiconductors, all diodes emit some light, but it takes some tweaking to do it efficiently and make that light visible. And LED is about 15-20% efficient in emitting visible light, making them far better than either incandescents of CFs. However, that light is monochromatic, meaning one color. Because of this, they are perfect for applications where the light is supposed to be colored, such as auto tail lights or traffic lights (or perhaps not).

There are two ways to get usable (white) light for household use. One is to use several LEDs of different colors. In fact, by manipulating the brightness of three or more LEDs we can make a lamp that can change color to fit the homeowner's mood. A simpler (though less efficient) way is the so called "white LEDs" that are used in flashlights. This is an LED that emits ultraviolet light, coated with phoshors, just like the fluorescent tube. It is superior to a fluorescent tube in that the LED is more efficient, doesn't contain mercury, isn't breakable (under normal circumstances) and lasts pretty much forever (50,000 hours or more).

So why don't we see them used everywhere? Heat. Ironically, although an LED produces very little heat compared to an incandescent bulb, since it is monochromatic the heat isn't being given off as infrared radiation. It sits inside the LED and can destroy it if it gets hot enough.

OLEDs, or Organic LEDs, are a newer technology. Yes, they are LEDs, but instead of using semiconductive crystals of materials like Gallium Arsenide Phosphide the use thin films of polymers (plastic), as thin as 50nm (a human hair is about 100,000nm thick). Because they are so thin, there is a high ratio of surface area to mass, meaning the light doesn't have to travel far before it is out of the LED and free to go out and light up the room. It also means there is more surface to cool off the device.

Unlike LEDs, OLEDs do wear out. They have a life span of about 14,000 hours before they degrade to 80% of their original brightness. On the other hand, they are up to twice as efficient as LEDs (or 20x as efficient as incandescents), which is why they are often found in cell phones, where battery life is important. One OLED technology, Phosphorescent OLEDs (PHOLEDs) claims it can reach up to 50% efficiency. And of course they are made without mercury or other toxic substances.

So when can I buy my OLED light bulb? According to this post we should see them starting to hit the market within the next year or two. However, if this roll out is like most in the tech industry, don't hold your breath. I'm sure they will be very expensive at first, but the technology can be printed with inkjet-like printers, which means once factories are tooled up they have the potential to be much cheaper than CFs. So perhaps the best course of action for the environment is to stock up on incandescents to make it to 2014 or so.

In researching these two posts I learned a lot about lighting technologies, the problems involved, the innovations taking place and tradeoffs in various designs. It was illuminating. No doubt I'll be posting more on the subject.

One final note. I'm sure "green" people and government will be touting how their regulation produced this lighty goodness. However, it should be known that OLEDs have been aggressively developed since before this legislation, and not because they would "save the Earth" but because they would increase the battery life of cell phones and media players. Here's a case where market forces alone produced innovation.


It's conspiracy of the Classic Coke kind. ;-)

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