What is the difference between solar photovoltaic and thermal?
The energy carried by solar radiation can be harnessed by different technologies depending on the desired end use. Photovoltaic solar technologies directly convert this radiation into electricity, while solar thermal technologies exploit the heat energy that this radiation creates in materials that have absorbed it.
In the case of photovoltaic solar, part of the solar radiation is captured using a photoconductive cell. The photons composing this radiation set electrons in motion within the cell, producing an electric current. A paving of mirrors or lenses can concentrate the solar radiation on a small high-performance cell converting a broader part of the light spectrum into electrical energy. This is known as concentration photovoltaic technology.
In the case of solar thermal, it is the heat resulting from the absorption of radiation by thermal collectors that is exploited. This heat energy is transferred to a fluid that can, for example, heat a surface (e.g., floor) or sanitary water (in a "water heater"). Solar thermal energy can also be used to cool buildings by absorbing heat.
It should be noted that it is also possible to convert solar thermal energy into electricity through a thermodynamic concentration solar system: the radiation is concentrated using mirrors on a heat transfer fluid that it heats to high temperature. The high-pressure steam resulting from the fluid's heat drives a turbo alternator to produce electricity.
