Photovoltaic
The
"photovoltaic effect" is the basic physical process through which a
PV cell converts sunlight into electricity. Sunlight is composed of photons, or
particles of solar energy. These photons contain various amounts of energy
corresponding to the different wavelengths of the solar spectrum.
When photons strike a PV cell, they may be
reflected or absorbed, or they may pass right through. Only the absorbed
photons generate electricity. When this happens, the energy of the photon is
transferred to an electron in an atom of the cell (which is actually a
semiconductor). With its newfound energy, the electron is able to escape from
its normal position associated with that atom to become part of the current in
an electrical circuit. By leaving this position, the electron causes a
"hole" to form. Special electrical properties of the PV cell—a
built-in electric field—provide the voltage needed to drive the current through
an external load (such as a light bulb).
Thermoelectric
Thermoelectric
The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice-versa. A
thermoelectric device creates a voltage when there is a different temperature
on each side.Conversely, when a voltage is applied to it, it creates a
temperature difference. At the atomic scale, a applied temperature gradient causes charge carriers in the
material to diffuse from the hot side to the cold side.
This effect can be used
to generate electricity, measure temperature or change the temperature of
objects. Because the direction of heating and cooling is determined by the
polarity of the applied voltage, thermoelectric devices are efficient temperature
controllers.
No comments:
Post a Comment