Wednesday, October 21, 2009

We need a fundamental shift in lighting

The title of this post may not mean what you think it means. At first, you may think I mean "we need to change all lights to LEDs," but in fact, it's really "we have to completely change how we build light fixtures before we can change all lights to LEDs."
The US Department of Energy has a contest going to award $10 million to the company that builds a 60-W lightbulb replacement using LEDs. There are several important stipulations that make this tricky, including dimmability using standard phase-cut wall dimmers, efficacy (luminous efficiency), color temperature and so on. Philips has produced the first entry, and certainly others are on the way.
The problem with this whole concept (while valid) is that everyone still seems to think that a lightbulb should look like the screw-in Edison base incandescent bulb. CFLs are the same way -- trying to fit a new technology into an old socket. Because of this, many CFL bulbs don't last very long because they get too hot in standard fixtures.
What we need to do is redesign the fixtures from the ground up. LEDs produce light and heat, and the heat they produce must be removed or the LED will fail quickly. The 20,000 hour (or longer) life of an LED presupposes that the LED is kept reasonably cool. Here's where the fundamental shift needs to happen.
Light bulbs, as a concept, need to be completely changed. Most luminaries (fixtures) are designed to take light from a point source (a light bulb) and spread that light evenly over a certain area. One notable exception is the linear fluorescent fixture. It takes light from a linear (long line) source and spreads it out. Take the same concept and apply it to LEDs, and we will be getting somewhere. Spread the LEDs out across the entire surface of the fixture, and the heat will be spread out and the light can still be focused nicely into the living/work space.
The "bulbs" can be individually replaced and certainly don't have to be replaced all at once. When one or two LEDs fail, the fixture can keep working (wire the LEDs in parallel, not series).
To make it even more fun, mount each LED on a metal-based circuit board (they are used a lot in high-power electronics) and include a small permanent magnet at each LED mounting location in the fixture, and now the LED elements are held in place magnetically. The electrical contacts can just be spring metal, and no real connector is required.
Part of the reason I'm posting this idea, rather than patenting it and keeping it to myself, is that now it can't be patented, because this is "prior art." I'd like many manufacturers to take the idea, build compatible fixtures and LED elements, and sell them to everyone.
If we want to accelerate the LED lighting revolution, I believe that a completely new paradigm is required.

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