Solar panels convert solar energy into electricity. but the solar energy incident on solar panels is in form of heat . So, is it possible for a solar panel to generate electricity if we supply heat source?
Solar cells are made out of N-type and P-type semiconductor material that use the visual light spectrum to generate electricity. Solar radiation with wavelengths of 380 nm to 750 nm (violet to red) strike the material with enough energy to knock electrons from their weak bonds and create an electric current. The unused wavelengths (ultraviolet & infrared) do not have enough energy to dislodge the electrons and are absorbed as heat.
Hi,
It should be mentionned that some PV components are sensitive to near infrared photons. For instance silicon pannels cutoff wavelength is about 1050 nm. See for instance this note :
http://www.nrel.gov/docs/fy12osti/54251.pdf
If you can heat some material that can withstand it to, say, 1000K, it will emit a measurable fraction (that can be calculated by the blackbody law - much less than 50%) of power in the band of sensitivity of the silicon PV. So the efficiency should be expected to be less than 5%... You can test it with a lamp bulb.
So Payman Salami, although beeing to resctrictive about the useful spectrum of Silicon, is right for the practical point of view.
Some materials are more sensitive to infrared than silicon...
Regards to all,
Vincent
Generally, the current solar cell absorption spectrum is as described by Vincent and Payman for practical purposes. Theoretically, yes it is possible to use hot surfaces or low energy photons to produce electricity by a method of up-conversion where you combine two or more low energy photons to get photons with energy equal to Eg. Similarly, you can also use down-conversion in the UV region of the spectrum. However, these techniques are still at R&D stage.
For more on these techniques, you may consult literature including; www.researchgate.net/publication/44391170_Modifying_the_solar_spectrum_to_enhance_silicon_solar_cell_efficiency__An_overview_of_available_materials/file/72e7e521c6f6785082.pdf&sa=X&scisig=AAGBfm2_vTgoKpJKTbnjPEZCqSGGaSjsrA&oi=scholarr.
For current commercial PV cells (Si, a-Si:H, CdTe/CIGS, GaAs),heating your solar cells may actually be counter-productive since low energy photons will result in thermalization leading to cell temperature rising above its operation temperature and hence reducing its efficiency.
Article Modifying the Solar Spectrum to Enhance Silicon Solar Cell E...
Dear Rajesh
The type of solar cell capable of this is more the antenna type solar cells. You can read more on this topic "solar antennas", and also seacrh interesting articles on using the infrared IR spectrum radiation of the earth at night to generate power.
You can search about this subject a lot of intersting articles in journal solar cells
This article can also help; http://spie.org/x109067.xml?WT.mc_id=KNRSOLARE.
Do not forget ot mention that generation depends on the type of solar PV technolgy. ACtually, there are more than10 technologies.
ThermoPhotoVoltaics (TPV) involves the use of radiation from a hot body other than the sun to generate electricity via photovoltaic cells. My experiments involved Yttria and Ytterbia stabilized Zirconia microballons heated to 2200 degrees K to irradiate Silicon photovoltaic cells. A body of literature on TPV is available on the web.
Depends what you mean by solar panel. There is solar thermal power generation, where radiation from the sun heats a medium (water, liquid salt) that then drives a turbine, and photovoltaic power generation, where radiation from the sun excites electron-hole pairs in a solar cell that then produces an electrical output directly. There is also thermophotovoltaics, which aim to combine the two concepts into one device.
So: solar thermal, yes; photovoltaic, no, heat is actually counterproducitve as noted above; thermophotovoltaic: probably. Generally though there are more direct and established methods of converting heat to power: thermoelectrics, and heating steam to drive a turbine.
Have a look at the programme of the 11th World Conference on Thermophotovoltaic Generation of Electricity (TPV-11): https://www.photovoltaic-conference.com/parallel-events/parallelevents-2014/11th-world-conference-thermopv.html
A PV panel uses only a fraction of the solar spectrum to transform radiation into electricity. Silicon cells do not produce any current beyond 1100 nm, which is in the near IR. In contrast, heat corresponds to the far infrared, at wavelengths of 10 µm or more (the lower the temperature, the larger the peak wavelength). Therefore, NO, solar panels _cannot_ produce electricity from heat. Actually when the panel's temperature increases its efficiency decreases!
The known solution for your question would be the thermoelectric effect, http://en.wikipedia.org/wiki/Thermoelectric_effect
There are thermal electric cells that are designed to change thermal energy to electricity. Their structure may be similar to solar cells, but their band gap is different. Thermal energy does not supply enough power for electrons to be promoted to the conduction band in common solar cells.
Directly converting thermal energy (whether conducted through radiation, convection, or conduction) is done using thermophotovoltaics, thermoelectric generators, thermionic generators, and magnetohydrodynamics generators.
Alternatively, it is possible to use upconversion technologies to convert a stream of low energy photons (e.g., IR) into a stream of higher energy photons (e.g., visible).
Most of these technologies are; however, still under R&D.
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