Microwave-excited lamp could be 50% efficient and "never" wear out

[Kolesar]

What do you think of this? It sounds like a gas-discharge tube. I wonder how long the microwave generator would last.

Everlasting light
Sep 6th 2007
From The Economist print edition

Energy: Researchers have developed an environmentally friendly light bulb that uses very little energy and should never need changing

ALTHOUGH it symbolises a bright idea, the traditional incandescent light bulb is a dud. It wastes huge amounts of electricity, radiating 95% of the energy it consumes as heat rather than light. Its life is also relatively short, culminating in a dull pop as its filament fractures. Now a team of researchers has devised a light bulb that is not only much more energy-efficient—it is also expected to last longer than the devices into which it is inserted. Moreover, the lamp could be used for rear-projection televisions as well as general illumination.

The trick to a longer life, for light bulbs at least, is to ensure that the lamp has no electrodes. Although electrodes are undeniably convenient for plugging bulbs directly into the lighting system, they are also the main reason why lamps fail. The electrodes wear out. They can react chemically with the gas inside the light bulb, making it grow dimmer. They are also difficult to seal into the structure of the bulb, making the rupture of these seals another potential source of failure.


Scientists working for Ceravision, a company based in Milton Keynes, in Britain, have designed a new form of lamp that eliminates the need for electrodes. Their device uses microwaves to transform electricity into light. It consists of a relatively small lump of aluminium oxide into which a hole has been bored. When the aluminium oxide is bombarded with microwaves generated from the same sort of device that powers a microwave oven, a concentrated electric field is created inside the void.


If a cylindrical capsule containing a suitable gas is inserted into the hole, the atoms of the gas become ionised. As electrons accelerate in the electric field, they gain energy that they pass on to the atoms and molecules of the gas as they collide with them, creating a glowing plasma. The resulting light is bright, and the process is energy-efficient. Indeed, whereas traditional light bulbs emit just 5% of their energy as light, and fluorescent tubes about 15%, the Ceravision lamp has an efficiency greater than 50%.

Because the lamp has no filament, the scientists who developed it think it will last for thousands of hours of use—in other words, for decades. Moreover, the light it generates comes from what is almost a single point, which means that the bulbs can be used in projectors and televisions. Because of this, the light is much more directional and the lamp could thus prove more efficient than bulbs that scatter light in all directions. Its long life would make the new light ideal for buildings in which the architecture makes changing light bulbs complicated and expensive. The lamps' small size makes them comparable to light-emitting diodes but the new lamp generates much brighter light than those semiconductor devices do. A single microwave generator can be used to power several lamps.

...snip last paragraph for copyright reasons....
http://www.economist.com/science/tq/displaystory.cfm?story_id=9719129

[PetrusMonsFormicarum]

1. No Planned Obsolescence?

Without the potential for future, repeated sales, this probably won't fly.

The original incandescent bulb has planned obsolescence; we've all been repeatedly buying them for decades. The technology exists (has existed since the things were invented) to have a permanent lightbulb (Edison's original bulb has never popped). Same with autos, major appliances, etc.

One of inventor Nikola Tesla's lifelong goals was to develop broadcast power, and he succeeded. Imagine living in a world without power cords or power lines. GE imagined that and saw a massive loss in profits over the coming years in both repeat sales and maintenance: it's the infrastructure where they stick it to you. GE quashed Tesla's efforts and buried his notes.

Perhaps a paradigm shift is approaching, where we all will decide that creating real, durable goods is better for us and the planet. I certainly hope so.

[papau]

2. Nikola Tesla's "broadcast power" never really shown to have "worked"

Tesla built a giant Tesla coil in Colorado Springs in an effort to broadcast power across the globe. The coil could generate extremely high voltages and emit huge lightning-like sparks from a big copper ball atop a tall tower. Tesla's idea was that the earth was a quiver with electrical energy, like a taut violin string. If one plucked the string at any point, the vibrations would be transmitted throughout its length. Same with the globe. The giant coil was to be Tesla's bow.

In his first test of the coil Tesla burned out a generator at the Colorado Springs electric plant. Later there were reports that he managed to light 200 incandescent bulbs at a distance of 26 miles. But this was never confirmed (Tesla coils can illuminate fluorescent bulbs, but usually at a distance of only a few feet.) It's hard to see how you'd avoid wasting huge amounts of energy if it did work.

Telsa attempted a second try at "broadcast power" on Long Island via $150,000 from J.P. Morgan for an even larger coil. But the machine was never completed and in 1905 the project was abandoned.