Thermophotovoltaics (TPVs) are a class of power generating systems that are used to convert thermal energy to electrical energy. They consist of, at a minimum, an emitter and a photovoltaic power converter. However, most TPV systems also include additional components such as concentrators, filters and reflectors. The basic principle of operation is similar to that of traditional photovoltaics (PV) where a p/n junction is used to absorb optical energy, generate and separate electron/hole pairs, and in doing so convert that energy into electrical power. The difference is that the optical energy is not directly generated by the sun, but instead by a material at high temperature (termed the emitter), causing it to emit light. In this way thermal energy is converted to electrical energy.
The emitter can be heated by sunlight or combustion. In this sense, TPVs provide a great deal of versatility in potential fuels. In the case of solar TPVs, extremely large concentrators are needed to provide reasonable temperatures for efficient operation.
Vast improvements can be made on this basic concept by taking advantage of filters or selective emitters to create emissions in a narrow wavelength range that is optimized for the specific photovoltaic (PV) converter used in the system. In this way TPVs can overcome a fundamental challenge for traditional PVs, making efficient use of the entire solar spectrum. For blackbody emitters, photons with energy less than the bandgap of the converter cannot be absorbed to generate electron/hole pairs and are either reflected and lost or passes through the cell. Photons with energy above the bandgap can be absorbed, but the excess energy, ΔG = Ephoton − Eg , is again lost, generating undesirable heating in the cell. In the case of TPVs, similar issues can exist, but the use of either selective emitters (emissivity over only a narrow wavelength range), or optical filters that only pass a narrow range of wavelengths and reflect all others, can be used to generate emission spectra that can be optimally converted by the PV converter. In this way, these photons are not lost or used inefficiently, in principle, drastically increasing the overall system efficiency. In the case of reflective filters, the emitter must be able to absorb over this range to make effective use those photons not converted.
In order to achieve the maximum efficiency, all photons should be converted. A process often termed photon recycling can be used to approach this. Here reflectors are placed behind the converter and anywhere else in the system that photons might not be efficiently directed to the collector. These photons are directed back to the concentrator where they can be converted, or back to the emitter, where they can be reabsorbed to generate heat and additional photons. An idealized TPV system would use photon recycling and selective emission to utilize all photons and allow them to be optimally converted.
What I got from this-
These things still pick up on light, but it is infrared light and the cells are tuned to only accept a certain band of spectrum. I am assuming that the cells are tuned to match the source and not the other way around. So if you planned to use these inside a coal power plant and wanted to use the heat generated by the coal to power these panels, the cells would then be set to match the spectrum of the source. This is a cool idea. I would love to learn more about this, and please correct any of the information I listed, it is just from wikipedia. Cheers bro, keep the knowledge flowing
