|Elliott Sound Products||ESL - Electron Stimulated Luminescence|
Rod Elliott (Elliott Sound Products)
Page Created and Copyright © 23 September 2009
Updated 13 March 2012
There's not a lot of information available on ESL™ lamps as yet, as this is a new technology. The process is proprietary to Vu1, and is either patented or patent pending. The use of patent protection is a pity (although completely understandable), since it precludes others from using the technique - although if sensible licensing arrangements are made it may not be an issue. If these lamps are successful, they will solve the problems inherent in many other bulb-shaped light sources.
ESL lights are expected to last for about 6,000 hours, offer full range dimming, no warm-up time, and a light output of around 40 lumens/Watt (according to the manufacturer's website). Unfortunately, there is no information available that I could find that discusses the way they work, and full scale manufacturing isn't due to start until late 2009/2010 (this information is pure hearsay - there's nothing on the website). Without anything for anyone outside the company to test and verify, all claims must be taken with a grain of salt, because the only info presently available seems to be from "tame" consultants and industry experts. A little scepticism is a good thing when someone claims to have solved a major problem, but provides zero technical info that would allow others to examine the likelihood of success.
Vu1 claims that their lighting will kill CFL lamps, but this remains to be seen. At 6,000 hours, it's not the longest lasting lamp around, and without knowing what's inside it's almost impossible to determine if this is actually possible or likely. It's also claimed that LED lighting is doomed, but this is simply nonsense. While LEDs should not be constrained to traditional bulb shapes, they offer much higher luminous efficacy than the ESL, and if kept cool will outlast ESLs by a factor of almost 10 times.
Because there's so little real information available at present, there's not very much that can be said about these new light sources. When more data becomes available, it will be published here. I am especially interested in the technicalities - they claim to have 8 patents pending, but no technical details are available.
The choice of acronym is either unfortunate or deliberate - 'ESL' has been used for some time for Energy Saving Lighting, so web searches are seriously polluted with extraneous results. At this stage, it's not possible to take any of the claims too seriously, because they are just that ... claims. Now, if Vu1 were to send me a few samples, I'd be more than happy to test them and publish the results.
According to the Vu1 website, the ESL uses an electron beam and phosphor, much like a cathode ray tube as used for television sets in the recent past. They claim that the electron emitter (the cathode) generates a 'wash' of electrons, not focussed like a TV tube's beam. This broad 'beam' strikes the phosphor at the front of the lamp, and causes it to glow brightly.
With no further details to mitigate what seems like pure marketing hype, I see some flaws in the description. In order to get a bright emission from the phosphors, the electron beam needs to be travelling fast, and/or have a significant current. In a TV tube this is done using a very high acceleration voltage, and is essential because of the entire screen having to be illuminated by a single flying spot. For a lamp, the current is present all (or most) of the time, so instantaneous intensity is not such an issue. However, all phosphors degrade over time because of the bombardment by electrons, and this limits the life. No details are given about light output after 6,000 hours. It may only be half as bright as when new at the end of life, but no information is made available.
For an electron beam to work at all, the tube/bulb/whatever must be almost a complete vacuum. Nothing really hard there, as it's been done in countless CRT applications for many years, as well as valves (vacuum tubes). The cathode materials must be carefully selected to give good emission, and these will also deteriorate over time. The final part of the puzzle is the high voltage supply. Again, this is relatively simple using small switchmode power supplies, a little transformer and high voltage diode(s). The basic technology is pretty straightforward, but the details of the cathode materials and phosphors are essential to be able to make any kind of informed comment.
Since Vu1 claims a very good power factor (>0.92), the power supply probably doesn't use a filter capacitor, which would be electrolytic and have a very short life due to the heat. The remaining electronics also have to withstand high temperatures though - the ESL is claimed to generate "half the heat" of an incandescent lamp. This is still a lot of heat, and electronic parts don't like running hot.
At the time of writing, the ESL lamp has to be considered more of a curiosity than a real product. Making something work in a lab is very different from having it work reliably at the hands of the average consumer, who will usually never consider the temperature and ventilation needs because this was never necessary with incandescent lamps. Until these lamps become available and can be independently tested to determine if they live up to the claims made, the available data do not indicate that this is earth-changing technology. At 40 lumens/Watt, it's already easily beaten by some CFLs, and many newer LED lamps.
Since this article was written, ESL lamps have gone on sale in the US, and I've read through a few pages of customer reviews and comments. There is still no useful information available though, so the circuit details are still unknown. It should come as no surprise that some purchasers love these lamps, and others are less enthusiastic.
Those on offer are rated at 19.5W (120V only from what I've seen so far), and are claimed to last 11,000 hours. The claimed output is 500 lumens, so luminous efficacy is just over 25lm/W - well below that of comparable CFLs or LED lamps. This is too low to obtain US 'Energy Star' certification and is somewhat disappointing.
There is a bit of additional information at Green Prophet, but that needs to be read with the consideration that there may or may not be an ulterior motive. I have no affiliation with the site, and the link is provided as a reader service - nothing more. A search for 'ESL lamp' will find a fair number of hits, but the available information is still very limited. Note that when searching, you may get a lot of hits on 'Energy Saving Lighting' - this mostly has nothing to do with the ESL technology.
Naturally, if some kind soul wanted to send me an ESL lamp (working or not), I would cheerfully accept it, and find out what's inside. If you happen to fit the category of 'kind soul', my postal address is available from the Contact page.
|Copyright Notice. This material, including but not limited to all text and diagrams, is the intellectual property of Rod Elliott, and is Copyright © 2008. Reproduction or re-publication by any means whatsoever, whether electronic, mechanical or electro-mechanical, is strictly prohibited under International Copyright laws. The author / editor (Rod Elliott) grants the reader the right to use this information for personal use only, and further allows that one (1) copy may be made for reference. Commercial use in whole or in part is prohibited without express written authorisation from Rod Elliott.|