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Renewables Pyro, Piezo, Thermo, Photo, Tribo - Types of Electricity Piezoelectricity - charge that accumulates in certain solid materials in response to applied mechanical stress (some crystals, biological matter such as DNA and bone, and some ceramics). Is an inverse process - putting electricity into a piezosensitive structure creates mechanical deformation. Used in sonar - Piezotransducer + hydrophone. Since sound is a pressure wave, the piezo which is very sensitive to changes in pressure, can generate an electrical waveform when a pressure wave strikes it. Pyroelectricity - ability of some materials to hold an electric charge when they are heated or cooled. Change in temp causes atoms within the crystal structure to move resulting in polarization and thus voltage. Eventually the charge leaks out even at a constant temperature - the electrons re-align to reduce voltage. First discovered in BC when certain materials were observed to attract not ashes but not cold ones. Passive Infrared Sensors use this principle. Heat of a human or animal several feet away is detectable. Thermoelectricity - system temp stays the same, the differential creates varying charge across parts of the material. Peltier Junction utilizes this to create a temperature differential. Triboelectric Effect - "contact electricity" - Through rubbing, charge gets built up. The scientific name for "static electricity". |