Electrodeless Sulphur Lights
- New light source
by George Booth <booth-at-hpmtlgb1.lvld.hp.com> (Tue, 25 Jul 1995)
- Electrodeless lamps
by martin-h-at-mail.utexas.edu (Martin Harriman) (Wed, 26 Jul 1995)
- Sulphur lighting
by franc-at-golden.golden.net (Sun, 17 Nov 1996)
company adapting this technology to the consumer market!
by George Booth <booth-at-hpmtlgb1.lvld.hp.com>
Date: Tue, 25 Jul 1995
I found this article in the February 1995 Popular Science:
Lighting: Bright Light, Small Bulb
by Mariette DiChristina
"In this new light bulb, sulfur excited by microwaves emits a bright
white light. At the DOE's headquarters, a sulfur bulb at each end of
one 240-foot-long light pipe replaced 240 individual 175-watt
high-intensity lamps. One Tootsie-Pop-size lamp gives off the same
light as more than 250 standard 100 watt incandescent bulbs."
It has roughly the dimensions of a Tootsie-Pop, but don't let the
diminutive size fool you: Sparked by microwaves, a new sulfur bulb
packs a lighting wallop. One 5,900 watt bulb generates the same amount
of light as hundreds af today's industrial high-intensity
mercury-vapor lamps - using 20 to 30 percent less energy.
"It's a major breakthrough in lighting," says Christine Ervin of the
Department of Energy. Unlike conventional lighting, sulfur bulbs have
no electrode to wear out. That means the bulbs could operate as long
as the microwave generators (10,000 to 15,000 hours). While this is
comparable with today's high intensity lamps, those typically dim to
half their original output by that time because their phosphors
degrade. "We don't know how long it will lost ultimately," says Kent
Kipling of Fusion Lighting of Rockville, Md., which developed the bulb
under a DOE contract.
The sulfur bulbs were combined with plastic "light pipes" from 3M for
testing at two installations in Washington, D.C. - DOE's headquarters
at the Forrestol Building and the Smithsonian's Air & Space Museum.
DOE says the two test installations cost less than half the price of
the conventional lighting systems they replaced.
The sulfur bulb's hollow quartz sphere contains a small amount of
inert argon gas and yellow sulfur powder. To generate light, the bulb
is spun at 600 rpm and is simultaneously bombarded with microwaves in
a compact generator cavity originally developed for ultraviolet
industrial technology. Heated by the argon. the sulfur powder boils
Into a vapor and emits a bright white light. This light is projected
by a reflector into long plastic pipes lined with a semi-reflective
film with either a mirror or a second bulb at the far end. The light
zig-zags along the pipe, with some of it directed through the film for
illumination of an area.
The sulfur technology may sound simple to develop. But like many movie
stars, the bulb is a ten-year "overnight" success. For example, it
requires a special microwave cavity, which had been refined over
decades for industrial uses. "We must have spent more than 100
man-years to get to this point," says Michael Ury, one af the bulb's
Sulfur had also never been tried in lighting before, says Ury, because
it oxidizes metals - and so would degrade the electrodes used in
conventional bulbs. "We were always trying new ideas, crazy ideas," he
says. "I guess we just wanted to be different." Serendipitously,
Ury's colleague James Dolan picked the right microwave cavity and the
right rpm to spin the bulb on the first try. "If we didn't get
everything together like that, we might have missed it," ssys Ury.
In addition to its energy efficiency and long life, the sulfur bulb
offers other benefits. Because its bright white light is similar to
natural light, it is more aesthetically pleasing than the blue-white
color of high-intensity mercury-vepor lamps or some fluorescent lamps.
Plants may prefer it as well: NASA has a two-year contract with Fusion
to develop its light for growing plants in space. And the new bulb
produces far less of the fabric-fading ultraviolet rays generated by
other industrial lamps - a bonus for fragile museum exhibits as well
as home furniture. The disposal af mercury containing lamps also has
been an environmental problem.
While sulfur bulbs will first illuminate large spaces like shopping
centers, aircroft hangers, and factories, home applicafions are also
under development. Commercial products could appear within two yeors.
by martin-h-at-mail.utexas.edu (Martin Harriman)
Date: Wed, 26 Jul 1995
There are a couple of electrodeless lamp technologies out there, some in
production, and some prototyping (the sulfur lamp is in the latter
category). Most of these are better known (and more available) in Europe
than in North America.
Induction lamps are available from Philips, GE, and Intersource Technology.
Philips QL lamps are theoretically available now in North America, but
don't appear in their catalogs, and haven't been marketed here except to
luminaire manufacturers. Luminaires are available in Europe.
GE's Genura lamp has been available for some time in Europe; GE Lighting
was talking about a 1995 introduction for North America, initially
targeting 75 watt R30 retrofits (since these are going away October 31).
Intersource Technology has some products, but apparently none in
distribution yet; they seem to still be talking to luminaire OEMs.
The QL lamps have separate power supplies, CRI >80, efficacy about 65-70
lumens per watt (i.e., comparable to compact fluorescent & MH), and average
rated life about 100,000 hours (don't you love statistical extrapolation?).
The "big" lamps put out 6000 (initial) lumens.
The Genura is packaged as a complete unit with a medium screwbase, slightly
smaller than the R30 it replaces. Its CRI is 82, efficacy a bit lower than
MH (but much higher, of course, than the incandescent it replaces), and
average rated life of 10,000 hours. It puts out 1100 initial lumens.
The induction lamps are in production, and are well received in Europe.
Their power supplies run at 2.65MHz. The QL is FCC certified for
commercial (but not residential) use; the Genura should be certified for
residential use. The induction lamps use RE phosphors, and so can produce
the same flavors of light as compact fluorescents.
The sulfur lamps are still prototypes. Their efficacies are also projected
to be comparable to the compact fluorescents and MH lamps, with life in the
10,000 to 20,000 hour range. The big problem seems to be getting an
affordable, efficient, and most of all reliable microwave source. They are
running at 2.45GHz to take advantage of the components already available
for microwave ovens. There have also been some complaints about the color
rendering of the prototypes.
One should also point out that 5900 watt, 450,000 lumen lamps have limited
applications in residential construction. Make a pretty nice oven, though,
or you could bleach out your carpets to a nice neutral beige.
Date: Sun, 17 Nov 1996
In 1994, DOE announced that a new, highly efficient lighting system
was illuminating the exterior of the Forrestal Building in Washington,
D.C., and the Space Hall of the Smithsonian's National Air and
Space Museum. The new system is a technological breakthrough that
couples high-power sulfur lamps to a light pipe system that distributes
the light. The lighting of the two buildings is the first working
U.S. example of the high-power version of the sulfur lamp. In
these installations, a hollow pipe distributes focused light from
the sulfur lamp evenly over large areas.
The sulfur lamp bulb consists of a spherical quartz envelope filled
with a few milligrams of sulfur and an inert noble gas, such as
argon, which is weakly ionized using microwaves. The argon heats
the sulfur into a gaseous state, forming diatomic sulfur molecules,
or dimers. The dimers emit a broad continuum of energy as they
drop back to lower energy states--a process called molecular emission.
Molecular sulfur emits almost entirely over the visible portion
of the electromagnetic spectrum, producing a uniform visible spectrum
similar to sunlight but with very little undesirable infrared
or ultraviolet radiation. Conventional mercury lamps and most
other high-intensity discharge (HID) sources are built around
atomic emission and produce an artificial-looking light with many
Unlike conventional sources whose outputs typically diminish 75%
over time, sulfur lamps will maintain their efficiency and light
output over their entire lifetimes. By eliminating the need to
compensate for lamp lumen depreciation, fewer sulfur lamps can
provide a required light level, possibly for long lives of up
to 50,000 hours. In addition, sulfur lamps contain no mercury,
an environmentally toxic substance used in all other conventional
The sulfur lamp was developed originally by scientists (now at
Fusion Lighting in Rockville, Maryland) who discovered that sulfur
excited by microwave energy could be used in place of mercury
in ultraviolet industrial lamps to produce a high-quality white
light. These lamps operated at power and light output levels (3.5
KW input and 450,000 lumens) too high for most commercial applications.
The high wattage required air-cooling and spinning the lamps to
operate them. Applying their expertise in electrodeless discharge
lamps, LBL researchers developed lower-power lamps using radio
frequencies instead of microwaves. In 1993, they demonstrated
an RF-driven sulfur lamp that produced up to 15,000 lumens with
an RF input of only 100 watts--a luminous efficacy of approximately
150 lumens per RF watt. While the lamps still needed to be rotated,
lower-power operation allowed the air cooling to be eliminated.
Although they are prototypes, the first-generation lamps at the
Forrestal Building and the National Air and Space Museum are nonetheless
energy- efficient. The Forrestal Building's 280-foot light pipe
and two sulfur lamps replaced about 280 mercury HID fixtures,
resulting in a measured energy savings of more than 65% and saving
DOE approximately $8000 annually in energy costs. Because the
sulfur lamp system replaced an old mercury system at the end of
its maintenance cycle, the new light levels were roughly four
times those of the old system. Maintenance costs are also lower,
saving an additional $1500 per year.
DOE is funding Fusion Lighting through LBL to develop a microwave-
operated, high-power sulfur lamp of 1000 watts, producing 125,000
lumens. It is best suited for applications like sports stadiums,
convention centers, aircraft hangars, large maintenance facilities,
highway and street lighting, and shopping mall and industrial
lighting. Another DOE-funded project at Fusion Lighting is aimed
at developing a commercial RF-driven sulfur lamp at lower power
(50-100 watts)--small enough for use in homes and commercial buildings.