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What is solar thermal energy?

Solar thermal energy is the energy that is produced from the use of thermal energy that produces the heat of the sun's rays. The energy produced by this solar radiation can be used for multiple uses such as heating and hot water in the home and for air conditioning and even cooling in industrial processes. Yes, heat can also serve to provide cold.

In summer, when we enjoy more hours of sunlight, this solar thermal energy can be used to heat drinking water or to generate electricity, while in winter, when the hours of light are scarcer and the sun heats less, we can use it as support for other energy extraction systems.

How does solar thermal energy work?

Unlike photovoltaic energy, which also uses the sun's energy and converts it into electricity through a semiconductor device called a photovoltaic cell, solar thermal energy is transferred through a heat-carrying medium which, in this case, is usually a thermal oil.

This energy is produced following the following circuit:

  1. Sunlight falls on plates called collectors, which are the ones that start the process by collecting solar radiation.

  2. These collectors send the accumulated heat to an exchanger that is usually a turbine through a system of pipes, valves, pumps ... This first procedure is called the primary circuit.

  3. Once the energy has moved the turbine or the exchanger, it is transferred to an auxiliary generator that can be a boiler or a thermos that also works as an accumulator of said energy. This last step of the procedure forms the secondary circuit.

The collectors that start the process can be of different types according to the temperature they collect and according to the form and functionality they perform. Depending on the temperature they support, we can find low temperature collectors, that is, less than 65ºC, medium temperature collectors supporting up to 300ºC and, finally, high temperature, reaching radiation of up to 500ºC.

Among the high temperature collectors, the best known are:

- Cylindrical-parabolic collectors in which the sun falls on mobile mirrors that send their rays to a tube with a fluid that is the one that will reach the exchanger generating energy.

Photo: Kaxu Solar One Solar Plant, 100 MW, in the town of Poffader (South Africa), designed by Arsinger, SL

- Solar power tower or heliostat field: in which the sun hits mobile mirrors that send its rays to a central tower in which the water is heated, evaporates and that steam moves the turbine that generates the  Energy  electrical.

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