An experiment is proposed to test the possibility of direct conversion of thermal energy into electrical energy by creating a semiconductor structure using carbon nanotubes.
Contents:
The problem of spontaneous combustion of peat.
Fires on peat-lands often turn into real natural disasters. It is extremely difficult to extinguish burning lignin or peat. These fires flare up and spread slowly, but can last a very long time — for many months, and sometimes for several years. Peat can burn underground without oxygen, even in winter under snow. It can burn under a layer of sand, below the water level.
To set something on fire, you need a local concentration of energy — to light a match, collect sunlight with a lens, or something like that. Thermal radiation is homogeneous, isotropic and distributed according to Planck’s law. The laws of entropy cannot allow radiation to spontaneously concentrate in any particular place to create fire conditions. But is this the general case? Are there any special conditions in nature when thermal radiation behaves completely differently and exhibits self-organizing properties?
When answering the question whether thermal radiation can be coherent, you need to understand why as a rule it is not coherent. In order for individual radiation sources to be able to coordinate their actions the influence of the external environment should be neglected. For stimulated emission to take place the external electromagnetic field must significantly exceed the influence of the environment. In lasers, radiation usually occurs at internal electronic levels and ordinary heat does not have any effect on the process. In the case of thermal radiation, inter-atomic and inter-molecular bonds, on the contrary, have such a strong influence on the radiation process that no any stimulated emission may appear.
Is it possible to isolate individual emitters from the external environment in such a way that their thermal radiation will cause mutual stimulated coherent emission? Let us consider the geometric structure of lignin and peat. These substances are the remains of woody and partially destroyed plant cells. Cell membranes have an ultra-structure that can be compared to reinforced concrete: cellulose micro fibrils in their properties correspond to reinforcement, and lignin, which has high compressive strength, corresponds to concrete.
Although individual polymer molecules also contribute to the overall thermal radiation, cellulose has its own frequencies associated with its linear geometry. Long filaments can emit completely independently of the surrounding lignin and constitute a separate subsystem in the material. These molecules emit waves with an arbitrary frequency and phase, and these parameters will only be affected by the same macro-molecules located at a distance less than the coherence length. Due to the fact that the characteristic emission time of macro-molecules can be significant, this length will be sufficient to cover a large number of neighbors at once.
Near-field radiation is defined as approximately one-sixth of the radiation wavelength. There is a standing wave in this zone, which means that a resonator is not required for polymer molecules. The longer the wavelength studied by the macro-molecule, the greater the number of neighbors that will fall into the region where stimulated emission is possible. A ball of lignin with a diameter of 0.33 millimeters, if we take the near zone for millimeter radiation, contains tens of millions of cellulose molecules. Under such conditions, sooner or later all macro-molecules in one region will emit coherently.
In lasers, individual photons cannot have exactly the same wavelengths. In particular, they are greatly influenced by the Doppler shift associated with the thermal motion of atoms in the radiation medium. The condition for coherence of stimulated emission must be understood as such a mutual arrangement of waves in which the integral of the squared amplitude of an added waves, taken over the entire coherence length, will be maximum. In pulsed lasers, especially mode-locked lasers, the relative position of the photons is such that a very short train is obtained, and the shorter the train, the better the synchronization and the wider the overall frequency response of the entire radiation.
If individual macro-molecules in the composition of lignin emit coherently, then the resulting radiation should be collected into an object similar to a bell-shaped delta function, and the spatial size of such an object will be determined by the frequency width of the radiation of the macro-molecules. Most likely, in the case of peat, such radiation will be in the long-wave infrared and terahertz ranges. Now the radiation will be able to gather coherently in one place to heat the substance and a fire will become inevitable.
The ionization in the cell membrane.
If there is some useful physical mechanism that living organisms use, one can try to copy it or at least take the principle of its operation as a basis: modern helicopters are very far from real living dragonflies. How could we use the processes that underlie the occurrence of tension on the membrane of a living cell?
The membrane of any cell consists of a bi-layer of lipids, most of which are phospholipids. Phospholipid molecules have a hydrophilic (“head”) and a hydrophobic (“tail”) part. When membranes are formed, the hydrophobic portions of the molecules face inward of the membrane, and the hydrophilic portions face outward, on both outer sides of the membrane. This is very similar to a laser, where the role of a resonator is played by hydrophilic heads, and the hydrophobic tails are a matrix of antennas. In addition to good mechanical protection, such a structure is apparently capable of ionizing membrane atoms. A voltage of 0.1 volt appears on the membrane, which, with a membrane thickness of 10 nanometers, creates a field strength of ten million volts per meter, astronomic value which is close to the breakdown voltage. The theory of ion channels, which today explains the membrane potential, was created by physicians in the middle of the last century, when the word “laser” was not yet known.
When using intra-cavity laser spectroscopy, an increase in sensitivity of five orders of magnitude is observed. In the article «Principles of cold nucleosynthesis.» I tried to substantiate the assumption that the interaction of studying with matter in a standing wave can have a quasi-classical character similar to the Compton effect: a photon interacts as if its effective “interaction size” decreased by as much as the speed of light is greater than the speed of sound, that is, by these five orders of magnitude. In this case, infrared radiation in a standing wave will be able to be absorbed by the atom semi-classically — electrons will be knocked out of the atom in exactly the same way as an infrared laser pulse breaks through a copper coin.
Creation of a thermal battery.
Based on the foregoing, one can try to detect the internal thermal photoelectric effect experimentally. To do this, you need to transform a regular solar panel to create a structure reminiscent of a cell membrane: metal — p-n junction — metal, where carbon nanotubes are placed on (or in) the n-type semiconductor. The metal will act as a resonator (hydrophilic heads of phospholipids), and nanotubes will act as independent radiating antennas (hydrophobic tails of phospholipids).
If the ultrastructure of nanofiber antennas will be capable spontaneously, in the dark, at room temperature, to create a voltage at the p-n junction, an analogue of a solar battery will arise, where the role of solar radiation will be played by ordinary heat.