OSRAM is one of the leading manufacturers of light bulbs in the world. They claim their OSRAM Tungsten light bulb is an “ecological” lamp3 because of a reduction in losses due to thermal radiation.
In particular, they claim that due to a sophisticated coating on the bulb the thermal (infrared) radiation is reflected and the heat emitted from the filament is reflected back to the filament. As a result, the filament is heated further. This means that less electrical energy has to be supplied to the filament.
This is the equivalent argument used by proponents of the man-made global warming hypothesis, that is that a cooler system (the atmosphere) can reflect radiation back and heat up a warmer system (the Earth’s surface).
These claims violate the Second Law of Thermodynamics.
Scientific analysis, not of the misleading marketing blurb from OSRAM, but of the physical Tungsten light bulb, however, show that there is no violation of the Second Law of Thermodynamics. Nature behaves as she always does, even in the case of these artificial devices.
The second law can be expressed in several ways, but all of them coincide with a common meaning, i.e. an ineludible universal directionality of every process taking place in the Universe.
The way in which the Second Law is expressed depends on what we are considering at a given moment; for example, we could be considering the work done by one system on another system, or the universal entropic directionality, or the process of energy transfer from one system towards another system.
Any of these cases could be the most suitable explanation; however, with respect to the unalterable directionality which leads every process and phenomenon, this definition is the one granted by quantum mechanics1, 2. The context provided by quantum mechanics for the Second Law of Thermodynamics deepens further the gap between pseudoscience and real science.
The Second Law of Thermodynamics is enunciated as follows:
“The energy is always dispersed or diffused towards the system or systems with more available microstates.”1
This law applies to every thermodynamic system and to any place in the known universe. Additionally, it considers every association and every contextual function derived from the main statement. For example, we apply this concept to gas diffusion, chemical reactions, biotic processes, work, pressure, etcetera, etcetera.
Bearing this statement in mind, let us examine the Tungsten light bulb that, allegedly, beats this universal law.
OSRAM says that its innovative Tungsten light bulb will provide the benefit of
- A reduction in losses due to thermal radiation (IRC):
Special bulb geometry and a sophisticated coating on the bulb ensure that the thermal (infrared) radiation is reflected and the heat emitted from the filament is reflected back to the filament. As a result the filament is heated further. This means that less electrical energy has to be supplied to the filament. This technology is used for all low-voltage ECO lamps (12 V) because of the optimum geometric conditions 3
And that the consumer will also take advantage from
- A reduction in the thermal losses via the filler gas (xenon):
As the size (mass and diameter) of the gas atoms increases, the thermal conductivity of the filler gas decreases. By using the appropriate lamp filler gas, the heat loss of the tungsten filament via the gas can be reduced. This means that less electrical energy is needed to heat the filament. In addition, the use of a filler gas with atoms as heavy as possible slows down the vaporization of the tungsten atoms from the filament. This prolongs the life of the lamps. Xenon is an extremely rare gas (making up only 0.0000087% of the atmosphere, or 0.087 ppm). Of all the inert gases, xenon best meets these requirements. Despite the high cost we therefore use xenon as the filler gas in al (sic) the OSRAM ECO lamps.3
The first assertion gives us the main characteristics of the lamp:
It has a Tungsten (W, from Latin Wolframium pertaining to “wolf foam”) filament, which is energized by fast unidirectional electrons and is the source of energy for the lamp, and a “special” geometry of the bulb. Additionally, the inner surface of the bulb is layered with a “sophisticated coating”3.
The second description says that the fluorescent gas inside the bulb is Xenon (Xe). 3
What is the “special” geometry of the bulb? From the picture of the product, the bulb’s “special” geometry is that of a paraboloidal integrating mirror; nothing “special” about this particular characteristic which has been exploited for many years in integrating mirror reflectometers, which are highly advantageous over spherical mirrors when the energy source is low.4, 5
Paraboloidal integrating mirrors concentrate the radiation onto a given focal point that is accurately determined by the angle of curvature of the bulb5, which, for this case, works in a similar way to a TV parabolic antenna as it concentrates the reflected quantum/waves (visible, IR, UV, radio) onto a receptor (focal point) that is built in front of the paraboloidal antenna’s surface. Magnifying glasses also work in this way, but work by refracting radiation.
In OSRAM Tungsten light bulbs, the focal point upon which the radiation is concentrated is the Tungsten filament. We, therefore, have the first explanation on the overheating of the Tungsten filament:
It is not warmed up by a colder system inside the bulb, but by IR quantum/waves reflected towards the Tungsten filament by the “special coating” covering the inner surface of the paraboloidal integrating mirror bulb.
Now, does the Tungsten filament have the ability to absorb the reflected IR quantum/waves and reach a higher temperature? The answer is: Yes, Tungsten (W), in pure form, is the metal that has the highest melting point, and it is 3422 °C6. In addition, of all pure metals, Tungsten has the lowest coefficient of thermal expansion7, which is 4.3 x 10-6 m/m K. Consequently, the Tungsten filament can reach very high temperatures, if and only if its internal energy is lower than the reflected emission.
We have seen that the reflected radiation is concentrated on the Tungsten filament by the “sophisticated geometry” of the bulb; the energy reflected by the “special coating” and sent towards the Tungsten filament (the focal point) is, therefore, higher than the energy of the filament. Consequently, the energy in the OSRAM Tungsten light bulb is dispersed from a Tungsten surface in a higher energy state (the point where the radiation is concentrated) to the remaining structure of the filament where the molecules are in an energetically lower state.
The filament will not absorb reflected radiation beyond its limited and limiting available microstates, while the walls will not reflect radiation outgoing from the filament above their reflectance coefficient. Furthermore, the Tungsten filament will not emit radiation beyond its total emissivity power at maximum temperature. Remember that the Tungsten filament is not a blackbody and it does not behave like a blackbody.
So, there is not any violation to the Second Law of Thermodynamics.
Additionally, the second characteristic of the Tungsten light bulb refers to its content, which OSRAM says is Xenon (Xe). What OSRAM does not specify is that the noble gas Xenon inside the light bulb can be excited by the energy released by the Tungsten filament and transformed into ephemeral Xe dimers, i.e. Xe2.
The noble gas Xenon was first used in strobe lights for high speed photography, but was soon playing an important role in the manufacture of other devices, such as halogen lamps, nuclear reactors, lasers, etcetera.
After receiving a load of energy from the Tungsten filament, the over-energized Xenon fills its outer shell of electrons by taking an electron from a neighboring atom and forms a dimer, which is called an excimer.
After ~3 ns, the excimer returns to its energetic ground state and the absorbed energy is released towards other atoms and the Tungsten filament8. Nevertheless, each ~3 ns, the environment surrounding the Tungsten filament gets warmer than the Tungsten filament8. Consequently, we have again the same case of the reflected and concentrated radiation, i.e. the energy is transferred from a system with a higher energy density towards other systems with a lower energy density.
What we are seeing here is the same process that occurs in auroras, that is, a current of plasma. The plasma created by Xe excimers reaches an energy density that could be 1000 times higher than that of the source of photons9, that is, than the energy density of the Tungsten filament.
To avoid the light bulb overheating and exploding, OSRAM has integrated a resistor, to control the energy transferred to the Tungsten filament, and small magnetic ballasts, integrated in one or both extremes of the light bulb, to absorb the bulk of the excess of heat produced during the functioning of the lamp.
That is how the OSRAM “ECO-lamp” works. We do not see here any violation to the Second Law of Thermodynamics.
First of all, we notice an incorrect statement in the opening argument from the OSRAM technical description of its Tungsten light bulb.
The first effect of warming of the Tungsten filament is produced by concentrating IR quantum/waves onto the surface of the Tungsten filament, which is caused by a paraboloidal integrating mirror bulb within which the Tungsten filament is placed.
After the focal spot on the Tungsten filament’s surface is heated up, the energy transfer occurs to the remaining molecules of the Tungsten filament, which are energetically “colder” than the focal spot.
Once the Tungsten filament warms up, it starts emitting more radiation toward the volume of “normal” Xe inside the bulb, the “normal” Xe becomes excited and is transformed into an excimer, formed by two atoms of Xe (Xe2), which reaches an energy density state that is higher than that of the Tungsten filament and establishes a plasma current that transfers energy towards the Tungsten filament, i.e. from a warmer system (Xe2) towards the colder system (the Tungsten filament).
There is NOT any violation to the Second Law of Thermodynamics going on inside OSRAM Tungsten ECO-lamps.
In trying to convince potential clients of the ecological benefits of its product, OSRAM presents a misleading explanation that could be wrongly interpreted as a “violation to the Second Law of Thermodynamics”. In fact, as I have demonstrated, this is not what happens in either OSRAM lamps, or in the climate system, nor anywhere in the observable universe.
- Lambert, Frank L. Entropy Is Simple, Qualitatively. J. Chem. Educ., 2002, 79 (10), p 1241.
- Fried, Michael N. and Unguru, Sabetai. Apollonius of Perga’s Conica. 2001. Koninklijke. Netherlands.
- Modest, Michael F. Radiative Heat Transfer-Second Edition. 2003. Elsevier Science, USA and Academic Press, UK.
- Salvermoser, M. and Murnick, D. E. High-efficiency, High-Power, Stable 172 nm Xenon Excimer Light Source. Appl. Phys. Lett. 83, Page 1932 (2003).
- Suplee, Curt. The Plasma Universe. 2009. Division of Plasma Physics of the American Physical Society. Cambridge University Press. NY.
By Nasif S. Nahle
University Professor, Scientist and Director of Scientific Research Division at Biology Cabinet, Mexico