# Twice as Efficient -- and Lasts "Forever"



## Canuke (Jun 24, 2007)

Ah, but I'm not talking about LED -- it's a HID, actually.

A HID in the microwave.

http://www.ecogeek.org/content/view/736/

_More than 50% of the energy is emitted as light, which is 2x more than ordinary metal halide lamps, and four times more than ordinary fluorescents._

_The device is so long lived because there is no connection between the electricity source and the bulb itself. As long as the microwave emitter keeps emitting, and the glass tube never breaks, the device will last forever._


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## TorchBoy (Jun 24, 2007)

What happens to the other 50% of the energy that isn't converted to light? Is it all absorbed by the bulb as heat?

Edit: Microwave emitters lose power as they age, but it would be reasonably easy to compensate with electronics, bumping up the power output depending on the age of the microwave emitter.


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## IMSabbel (Jun 24, 2007)

Ah, they dont show details, but it looks EXACTLY like the sulfur-plasma lights that made a short run through the industry in the early 90s.

Yes, those lamps are more efficient than HID _and_ last easily 10 times as long.


But of course there is a drawback: The efficiency is only for the energy input in microwaves.
And of course, the _system_ is only as efficient and dureable as the microwave generator PLUS the lamp together. 

In practice, they archived about the same eddiciency than HIDs, including magneton losses, but needed a new driver every 2-4000 hours, completely negating the livetime issue (what good is not having to buy a new bulb if you have to change the generator in the same timeframe).


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## 2xTrinity (Jun 24, 2007)

IMSabbel said:


> Ah, they dont show details, but it looks EXACTLY like the sulfur-plasma lights that made a short run through the industry in the early 90s.
> 
> Yes, those lamps are more efficient than HID _and_ last easily 10 times as long.
> 
> ...



I would be curious if those would be able to compete with the newest fluorescent systems -- the ones with several high-intensity T5 tubes with electronic ballasts. I have seen some warehouse stores switch to those from old HID fixtures, and apparently they are more efficient, while providing a much better quality light. From what I understand those are seeing lifetimes pushing 20,000 hours, while maintaining most of their initial brightness. 

The problem I see with the big point sources -- and this is true of HIDs for things like warehouse lighting, is that the light has to be diffused using special fixtures, which certainly must take a toll on the efficiency.


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## yuandrew (Jun 24, 2007)

I've remembered reading about "electrodeless lamps" using microwaves or radio frequency to excite the gasses inside the lamp. The best example, of course, was the Sulfur lamp using microwaves. If I remember correctly, the best Sulfur lighting system produced around 180 to 200 lumens per watt. The high power output made them more practical for large area lighting (there were examples of them being used in warehouses and an airplane hanger); however, making them small enough for lower lighting levels such as residential use was difficult.

The GE Genura and the Sylvania Icetron were electrodeless lamps operating at 2.4ghz (same as microwave oven frequency) which used the fluorescent lamp operation principle. Instead of electrodes; the "ballast" generated the RF which goes into a coil at the base of the lamp. The RF then excites the gasses to produce UV which then excites a Tri-phospore coating. I know my Carl's Jr restaurant has several GE Genura compact fluorescent bulbs used as track lights from a demo program by GE back in 1998 or 99. I recall during my last visit that many of the bulbs were still working but the older ones were a lot dimmer than ones that had just been changed; most likely due to the phospore degrading over time.

GE was also supposed to produce a microwave powered lamp based on metal halide technology I've heard.

One of my older fluorescent lamp experiments:  I had also though about doing the same thing with a mercury vapor arc tube but I lost the arc tube before I could do it.
http://www.youtube.com/watch?v=cZctmAiDxvk


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## IMSabbel (Jun 25, 2007)

2xTrinity said:


> I would be curious if those would be able to compete with the newest fluorescent systems -- the ones with several high-intensity T5 tubes with electronic ballasts. I have seen some warehouse stores switch to those from old HID fixtures, and apparently they are more efficient, while providing a much better quality light. From what I understand those are seeing lifetimes pushing 20,000 hours, while maintaining most of their initial brightness.
> 
> The problem I see with the big point sources -- and this is true of HIDs for things like warehouse lighting, is that the light has to be diffused using special fixtures, which certainly must take a toll on the efficiency.



Well, in _large scale_ applications, they ARE more efficient (i have numbers like 150 lm/W in memory).
But there are huge problems in downsizing the light. Even a small bulb has huge energy output, as it is a volume source, and making the bulb very small will increase losses a lot.

So a typical light might be 4-6 cm spherical bulb with an output of well over 200k lumens.

Maybe they manage to build more stable microwave supplys now, compared to a decade ago. In that case, they would really be a nice source to illuminate huge spaces (Football stadium, warehouses, ect). But they are so hard to scale down that i cannot see them working in a car light (at least not more efficient than hid).


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## 65535 (Jun 29, 2007)

considering it isn't designed to heat water molecules the microwave unit may outlast any emitter tuned to waters resonant frequency.


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## TorchBoy (Jun 29, 2007)

But unless you can improve efficiencies the total prototype system will only be about 25% which is comparable with current sodium vapour and some LED prototypes. Microwave emitters have been around for a while so I don't imagine much improvement happening there.


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## 2xTrinity (Jun 29, 2007)

IMSabbel said:


> Well, in _large scale_ applications, they ARE more efficient (i have numbers like 150 lm/W in memory).
> But there are huge problems in downsizing the light. Even a small bulb has huge energy output, as it is a volume source, and making the bulb very small will increase losses a lot.
> 
> So a typical light might be 4-6 cm spherical bulb with an output of well over 200k lumens.
> ...


Even for large applications, from the white papers I have been reading, total system efficiency is far below 150 lumens per watt for a number of reasons -- since the light is coming from a single point source, there are significant optical losses involved with the reflectors and diffusers needed to disperse the light -- on the order of 50% fixture efficiency from what I was reading. Additionaly, those large high power bulbs generally required continuous forced-air cooling, so altogether, I recall total system efficiencies of closer to 50 lumens/watt. In the case of the Air and Space museum, I believe efficiency was even lower because they used filters to reduce the color temperature from 6000K, to the 4200K of the halide lamps that were replaced.

Most of the studies concluded that power efficiency was nearly the same, but that maintenance was cheaper without as many bulb replacements. Also, the inherent lack of ultraviolet light in the microwaves is a benefit for applications like museums. 

Most of the studies claiming that their product is better than fluorescent lamps will make a faulty comparison between their state of the art product, and much much older fluorescent fixtures, such as magnetic ballasted T12s. I woudl rather see a fairer comparison with a state of the art fluorescent, such as a high-output T5 fixture. I've seen a lot of warehouse stores switch to those from old Halide fixtures with very good results -- more even lighting, and more consistent color. Fluorescent fixtures can achieve much higher system efficiency than 50 lumens/watt because the light is already largely diffused, much more efficient fixtures are possible than with a 200K lumen point-source, or even a 5K lumen point-source like an HID. The best T5s can maintain around 90 mean bulb-lumens per watt, with expected lifetimes of 20,000 hours or more. Extra UV filtering may be required in some application, and for large installations, the extra maintenance cost associated with replacing bulbs may still be quite significant.


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