Aalok said:
Incident light on a PV cell generates both electricity and heat. That is because the incident light contains both visible and infrared light. If you can separate visible light and infrared light, and have only the visible light incident on the PV cell.
Would the PV cell generate heat, when it generates electricity?
Thanks in advance
“Much of the energy from sunlight reaching a PV cell is lost before it can be converted into electricity. But certain characteristics of solar cell materials also limit a cell's efficiency to convert the sunlight it receives.
Light is composed of photons—or packets of energy—that range in wavelength. When light strikes the surface of a solar cell, some photons are reflected and do not enter the cell. Other photons pass through the material. Of these, some are absorbed but only have enough energy to generate heat, and some have enough energy to separate electrons from their atomic bonds to produce charge carriers—negative electrons and positive holes (useful electrical energy).
Bandgap is the minimum amount of energy needed to free an electron from its bond, and this energy differs among semiconductor materials. The primary reason PV cells are not 100% efficient is because they cannot respond to the entire spectrum of sunlight. Photons with energy less than the material's bandgap are not absorbed, which wastes about 25% of incoming energy. The energy content of photons above the bandgap is wasted surplus—re-emitted as heat or light—and accounts for an additional loss of about 30%. Thus, the inefficient interactions of sunlight with cell material waste about 55% of the original energy.”
http://www.eere.energy.gov/basics/renewable_energy/pv_cell_conversion_efficiency.html
The efficiency of silicon PV cells decreases as the temperature increases. As the cell’s temperature increases quasiparticles, called phonons, are excited and move throughout the material, impeding the uniform movement of electrons. This impedance is what reduces efficiency.
Thin-film PV cells made from copper indium gallium selenide and cadmium telluride show great promise to increase overall efficiency. Two recent advances in PV technology are described here:
“Groningen, The Netherlands--Scientists from the University of Groningen and the FOM Foundation (Utrecht, The Netherlands) have learned how to harvest IR light by transmitting its energy to an up conversion material. This energy is then available for use in photovoltaic cells or for medical imaging.”
http://www.laserfocusworld.com/articles/2012/07/ir-light-harvested-and-efficiently-upconverted-for-photovoltaic-uses.html
“New type of photovoltaic device harnesses heat radiation that most solar cells ignore”
June 21, 2012
Source: David Chandler, MIT News Office
“About 40 percent of the solar energy reaching Earth’s surface lies in the near-infrared region of the spectrum — energy that conventional silicon-based solar cells are unable to harness. But a new kind of all-carbon solar cell developed by MIT researchers could tap into that unused energy, opening up the possibility of combination solar cells — incorporating both traditional silicon-based cells and the new all-carbon cells — that could make use of almost the entire range of sunlight’s energy.”
http://www.pennenergy.com/index/pow...wable/2012/june/new-type_of_photovoltaic.html
