In future photocells will probably be used to produce energy from renewable sources like the wind, geothermal and the sun. A photocell is a photoelectric cell. This is a device, which detects light and in response produces an electric reaction.
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A photocell is a type of resistor. When struck by light, the cell allows current to flow more freely. In future, photocells will be used to generate energy from renewable sources. Examples are sun, wind, wave, tidal, geothermal, biomass among others.