Spectrums: CFL (top) has mercury’s characteristic violet and green. Incandescent (middle) spectrum is smooth with strong reds (warm). LED (bottom) has a bright peak in blue.
If only there were a light bulb as efficient as a compact fluorescent light (CFL), but without the ghastly green light and brain-eating toxic mercury. Am I asking too much? The inventors of the Electron Stimulated Luminance (ESL) lights don’t think so. A company called Vu1 plans to sell ESL bulbs in Europe and the Mideast in 2013. Vu1 lights are based on cathode ray tube (CRT) technology, are dim-able and have the cozy glow of incandescent light bulbs. How did Vu1 accomplish this magic? It helps that I know a little bit about CRTs from the days when my brother and I repaired old televisions.
The Hard Way of Learning About CRTs
Nature Abhors a Vacuum, So Do I: It was the mid 1980s. My brother glared at me in that moment between the sound of breaking glass and the horrible bang-whoosh which tugged at our eardrums and filled the room with a greenish-white cloud, Dad is gonna be mad! I didn’t have time to say, shut up! as we bolted from the room, but I knew it was my fault. I held my breath to avoid inhaling poisonous mercury fumes from the fluorescent light I had just dropped across the back of Dad’s television.
It was a 1940s vintage Admiral TV with an AM/FM radio, phonograph and a 12 ½ inch picture tube. It was nearly old enough to have displayed the last time the Chicago Cubs had won the World Series in 1945. It had been around for Elvis’s debut and the moon landings. My father had begun to restore it the night before his wedding and my brother had fully repaired it in the mid 1980s– only a few weeks before I destroyed it.
When we mustered the courage to return to the room, we saw that the fluorescent tube was intact but the neck of the TV’s picture tube had broken off. Air rushing into the vacuum had blown a hole in the screen’s phosphor coating. I wondered, what we should fear more; mercury vapors, phosphorescent dust– or Dad.
CRT televisions faded into history, but fluorescent lights continue to be my bane. Our kitchen is equipped with dimmer switches. The prison-style bare bulb fixture in our bathroom is too fragile to support heavy CFL bulbs. Some fixtures require screw base bulbs, others have bayonet, candelabra or T-50 floodlight sockets. Until recently only one style of CFL light bulbs was available in Ireland, so we installed these into as many fixtures as possible. The CFLs in recessed sockets overheated and the ones we installed in the cool damp bathroom lasted only a few months. The ones on the dimmer switch didn’t work at all. Soon I had a collection of dead CFL light bulbs, waiting for the environment minister to devise a disposal plan for the toxic mercury inside them. His eventual plan was for citizens to ‘look it up on the Internet’– so here I am. Meanwhile, this became one of the first countries in the world to ban incandescent light bulbs. Am I screwed?
How do ESL lights work?
ESLs work just like the Cathode Ray Tube (CRT) in Dad’s old TV. There are differences but let me first explain how a CRT works. Inside the fragile glass neck there is a piece of metal called a cathode. The cathode is electrically heated with a filament similar to those used in incandescent bulbs. This allows electrons to ‘boil’ off of the metal’s surface.
These electrons won’t go far unless you remove the air and push many more electrons onto the cathode, giving it a negative charge. Since like charges repel, the negative electrons leave the cathode and fly towards a positively charged piece of metal near the front of the tube called an anode. This assembly is called an electron gun.
Once you have electrons shooting out of an electron gun, you need to give them a target. In an X-Ray machine the target is a chunk of metal which stops the electrons and forces them to give up their energy as X-Rays. In a CRT, the electrons strike a phosphorescent powder, causing it to glow. Electromagnets sweep the electron beam back and forth over the screen, painting a picture.
In a color CRT, three electron beams pass through a metal shadow mask, full of holes which direct the beams to red, green and blue phosphor dots.
There is Nothing Wrong With Your Television Set
During our TV repair years, my brother and I would occasionally find one with bad horizontal and vertical oscillator tubes. This disabled the beam steering magnets which left an extremely bright dot shining in the center of the screen. ESLs don’t use a shadow mask or beam steering magnets but they do have an electron gun and a bright phosphor screen. Vu1 has taken advantage of advancements in phosphor chemistry and small, high voltage power supplies to make what appears to be an ecologically friendly light..
What about X-Rays?
One of the first things I thought of when I heard about ESLs was, I thought we were trying to get rid of CRTs. My second thought was, What about X-Rays? In 1967 a General Electric manufacturing defect resulted in TVs which emitted 10-100,000 times the X radiation considered safe. Most TVs gave off some X-Rays, color ones more so, because the electron accelerating voltage was higher, at about 25,000 volts. The shadow mask stopped some electrons, converting their energy to X rays. To filter these, old TV screens were made of thick leaded glass.
ESL’s lack of a shadow mask and relatively low accelerating voltage of 5000V means they are unlikely to emit many more X-rays than a typical CFL bulb and nowhere near as much as the sun.) ESL lights have passed Underwriter’s Laboratory X-Ray testing in the U.S.
Throw Them in the Trash? You must be joking!
There is an old joke that fluorescent lights don’t give off light, they suck up dark and the tube gets black when it’s full of dark. But they’re actually mercury vapor discharge lights. A tiny heater boils a little bit of mercury, then 100-1000 volt ‘spark’ is sent through the vapor. The resulting light has some orange, a lot of green and a strongly ultraviolet component. A fluorescent phosphor coating converts the UV to white light. The mercury in CFLs does create a disposal problem which, along with previously mentioned advantages seems to give ESLs the edge.
But I wonder why we didn’t worry about long tube fluorescents which had much more mercury and sometimes even a little bit of radioactive Krypton in their starters. One reason may be that we weren’t as environmentally aware, another is that those lights seemed to last forever. When they flickered, someone would replace the ballast transformer and they’d continue to shine. I suspect most of my CFL duds have a perfectly good tube and a failure somewhere in the ballast or equivalent electronic components. The bare mercury tube and electronics have independent failure modes so why are they not independently replaceable?
From Cradle to Where?
So which is more dangerous, phosphor dust or mercury? Shards of glass imploding through a high vacuum or radioactive Krypton? I don’t know. But it bothers me that anyone is suggesting that a new technology is “trash bin safe.” The Wall Street Journal estimates that there are about 12 billion light bulbs in the world.
A back-of-the-envelope calculation based on 8 hours of light/day and a typical lifespan of 6000 hours gives a replacement interval of 750 days. ESLs are longer and heavier than CFL or incandescent bulbs. They weigh about a pound so that would come to 16 million pounds of e-waste per day. Some jurisdictions forbid disposing of CRTs and if Canada’s $0.25 per pound e-waste charge is typical, ESL disposal could cost the world millions of dollars per day.
I Take My Europium, Shaken, Not Stirred, and Very Very Rare
Vu1′s SEC filing says that their blue and green phosphors are zinc based and that the red phosphor, necessary for ESL’s warm reddish-yellow light, is based on the rare-earth element Europium (Eu).
Grab a magnifying glass and have a close look at your computer’s LCD screen here: . . . . . . . . . . . .
Those tiny red squares glow with the light of Europium. Grab a Euro note and you have some Europium. But if you’d invested in Europium rather than Euros, you’d be up about 1000%, the price of this rare-earth has soared to over $3000/kg. Pure europium costs upwards of $1,300,000/kilogram.
The thing about rare-earths is that they’re– well, rare. There are only about 150,000 tons of europium in the world. If that sounds like a lot, consider this. If ESLs were made of pure europium, we could throw away the entire world’s supply in 18 days. If container ships burned europium instead of oil, a single ship could use up the global supply in less than two years.
So you really don’t want to be throwing europium in the trash can. In fact the two best places to mine rare-earths are China and waste electronics heaps. It would be much better if ESLs were designed for repair. Most of the parts in dad’s old TV were replaceable. When the picture tubed dimmed, you would take it to be rejuvenated.
A high voltage would shake the dust from the cathode and it was as good as Frankenstein’s monster after a lightning bolt. Years later when the tube failed again, you might have the electron gun rebuilt. As long as fluorescent tube-wielding teenagers like me didn’t go near it, TVs could be repaired indefinitely. In fact a few 1940s televisions continue to operate today.
ESLs are an amazing technology and I can hardly wait until they become widely available in Europe and the Middle East. I’d like to see them replace most kinds of compact fluorescent bulbs, but I hope the manufacturer rethinks the end-game.
They’re too amazing to end up in the trash can.
Photo credits: Admiral TV photo by puuikibeach via Flickr.
Compact Fluorescent spectrum photo by Brian Nitz
CRT image created by Søren Peo Pedersen via Wikipedia
Photo of child with old CRTs by Thousandways via Wikimedia CC-BY-SA-2.5