WHY LEDs?

Why, Dr. Chipalkatti asked, are LEDs so interesting? First, they are very energy-efficient light sources. They are already more efficient than incandescent lamps and, because 20 percent of electricity use in the United States is related to lighting, energy experts have estimated a potential annual savings of $30-$70 billion in energy costs by 2020.

In addition, LEDs as a general rule are very long lasting. Different colors have different lifetimes, but the typical red or yellow LEDs have estimated life-times of about 100,000 hours, or more than 10 years. Even when they reach this lifetime they do not burn out as traditional bulbs do; rather, they begin to lose brightness gradually but remain useable to some degree. Another feature that brings long lifetimes is their robustness. They are solid-state devices; there are no filaments to break or electrodes or glass to shatter. This long lifetime allows people to spread the cost of their lighting system over a much longer period than traditionally possible.

Another selling point for LEDs is that they are very reliable devices. Because they can be used in rugged conditions, they are well suited for exterior applications such as traffic lights, where the cost, inconvenience, and even danger of changing a light bulb in the middle of traffic are considerable.

Finally, the quality of the light may be adjusted for the user. It is unlikely that a user would want to change from a blue light to red, although this is possible, however more subtle changes may be desirable, such as changing from a warm white light suitable for winter to a cool white light for summer.

A NEED FOR BRIGHTNESS . . .

He discussed some key indicators of future performance, such as brightness. White LEDs are now capable of 15 to 20 lumens per watt, and are expected to reach the range of 100 lumens per watt or more in the next decade or less. This expectation, he said, was backed by laboratory research by all the companies and government labs in this field. Earlier data indicate that prices and performance of new technologies can improve by perhaps a factor of 20 per decade, and that prices may drop by a factor of 10 per decade. The question that remains is, during the introduction of a new technology, what are the critical “trip wires” that trigger broader use of the technology. In the business this is called the price point. Some people have suggested that about 10 cents per lumen is such a point. For the industry to reach this point as soon as possible a more concerted effort by all major players will be required.

. . . AND A NEW LIGHTING INFRASTRUCTURE

Dr. Chipalkatti returned to the phenomenon of the disruptive technologies and to how they had been accepted in the past. He said that the advent of the



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