Installation of thermal solar energy

What Is Solar Thermal Energy?

Solar thermoelectric energy is a technology to generate electrical energy or electricity using thermal energy that comes from the Sun (solar heat). This type of energy is also often called thermoelectric energy.

What is solar thermal energy?

This process of electricity generation is carried out in so-called thermoelectric solar plants or solar thermal power plants. The first solar thermal power plants were built in Europe and Japan in the early 1980s.

How Does a Solar Thermal Power Plant Work?

The operation of a solar thermal plant is similar to that of a thermal power plant or that of a nuclear power plant. The distinctive element between them is the fuel or the heat source.

Thermal power plants use fossil fuels such as coal or gas to generate heat, nuclear power plants use the nuclear energy present in uranium atoms to generate thermal energy. On the other hand, thermoelectric plants use solar radiation.

The sun's rays are concentrated by mirrors in a receiver that reaches high temperatures of up to 1,000 degrees Celsius. This heat energy is used to heat a fluid and generate steam. The steam generated, which has a high pressure, allows a steam turbine to move. At the same time, this turbine drives a generator that will be in charge of converting mechanical energy into electricity.

Energy Conservation Law

As the law of conservation of energy announces: In all this process energy is transformed. Therefore, electricity is not created but is a succession of energy transformations:

  1. First of all we have the internal energy of the atoms that make up the Sun.
  2. They are transformed into nuclear energy in nuclear fusion reactions .
  3. Energy travels to Earth in the form of electromagnetic energy.
  4. This energy is transformed into heat energy by impacting against the solar collectors.
  5. Heat energy is converted into mechanical energy thanks to steam turbines.
  6. Finally a generator transforms mechanical energy into electrical energy.

What Techniques Are Used to Concentrate Solar Radiation?

There are different types of concentrators with which different maximum temperatures are obtained with their corresponding thermodynamic efficiencies. They are as follows:

  • Parabolic cylindrical solar concentrator . A parabolic cylindrical solar concentrator consists of a linear parabolic reflector that concentrates light onto a receiver positioned along the reflector's focal line.
  • Compact linear Fresnel reflector . Fresnel reflectors are made of many thin, flat strips of mirrors that focus sunlight onto tubes into which the working liquid is pumped.
  • Stirling Disc . A Stirling disk is a reflector that follows the Sun in two axes. In particular, the disc is a unique parabolic reflector that concentrates light into a receiver positioned at the focal point of the reflector.
  • Central tower solar power plant.  A central tower solar power plant consists of a set of reflectors called heliostats that concentrate sunlight onto a central receiver installed in a tower. Because the relative position of the Sun varies, heliostats must have the ability to reorient themselves by tracking on two axes.

What Are the Advantages and Disadvantages of This Technology?

Like all technologies, solar thermal power plants have advantages and disadvantages:

Advantages of Solar Thermal Power Plants

The main advantage is that the fuel used is solar radiation. A free and inexhaustible resource. For this reason it is considered renewable energy. Regarding fossil energy plants, they do not use fossil fuels, therefore they do not emit greenhouse gases and do not contribute to worsening the problem of climate change.

Disadvantages of Solar Thermoelectric Energy

The main drawback is in the schedule and weather that do not allow a constant amount of electrical energy to be generated. Initially, the first plants could only operate during the hours of solar irradiation, but today it is possible to store heat during the day to produce electricity at night.

On the other hand, the maintenance of these facilities involves constantly cleaning large surfaces of reflectors. For this reason, the consumption of water and chemical products is abundant.

    What Is the Influence of Geography on Solar Thermoelectric Plants?

    Concentrated thermal energy systems always consist of mirrors and / or lenses that group direct sunlight and a receiver that contains a liquid heated by the grouped light.

    The diffuse part of sunlight, that is, the part of light scattered by clouds and particles in the atmosphere, cannot be grouped together and is therefore not used by this type of system. As a result, solar thermal systems are only suitable for areas with little cloud.

    In the Netherlands, for example, on average, 60% of light consists of diffused light. Therefore, solar thermal energy cannot be used in the Netherlands and Flanders, but there is sufficient solar energy in the  tropics  and in southern Spain, Italy and Greece.

    Why Are Solar Farms Not Created in Deserts?

    Theoretically, mirror power plants in the  Sahara  in an area the size of France (1/5 of the Sahara) can provide current global energy consumption. However, in Europe, two practical obstacles hold investors back:

    • Cooperation between European and North African countries is such that investment risks are greater in North Africa than within the EU.
    • The organization of electricity transmission between the continents, although there are  already  power lines .

    Published: March 29, 2017
    Last review: April 12, 2020