Solar Thermal Power Plant

The solar thermal power plant or solar thermal plant is one of the most important industrial installations that use solar energy. We are going to tell you what it is, how it works and the different types of solar thermal power plants used today.

A solar thermal power plant or solar thermal plant is a complex where sunlight is harnessed and converted into electrical energy by concentrating the sun's rays.

This method is carried out by means of the photothermal process. In these plants photothermal processes are carried out, where the heat from the sun's rays heats a fluid producing steam, which is then directed to the turbines. In this way, electrical energy is obtained as a result.

Solar thermal tower power plant

Solar thermal power plants based on central receiver technology transform the energy from the sun into other, usually electrical, energy by means of a thermodynamic cycle.

In general, a solar thermal tower power plant is composed of a series of different subsystems:

- Collector subsystem.

- Receiver subsystem.

- Power subsystem.

- Storage subsystem.

- Electrical subsystem.

- Control subsystem.

- Data processing and acquisition subsystem.

The low density of energy coming from the Sun makes it necessary to concentrate it in order to increase the performance of the thermodynamic transformation. In this way, the collector subsystem will be in charge of redirecting this energy, concentrating it in a central receiver located at a considerable height in a tower.

Heliostats

This collector subsystem is made up of a series of heliostats, reflecting surfaces placed in an orderly fashion on a terrain, which are automatically oriented through the control subsystem that governs them to continuously track the sun. In this way, the sun's rays are reflected at a certain point on the receiver.

Thus, the heliostats are oriented according to the position of the sun, achieving a higher power density in the receiver, with the consequent increase in temperature.

Heat utilization and conversion into electrical energy

The resulting thermal energy is used by a heat transfer fluid with which heat is exchanged and transformed into electrical energy by the power subsystem or, if required, directly for industrial use.

In order to avoid the shutdown of the power subsystem when blockages occur due to cloud transients, this type of power plant usually has an energy storage or buffer subsystem, which also helps to compensate energy between the receiver and power subsystem, so that it provides or stores it while maintaining production at all times.

On the other hand, commercial plants have an electrical subsystem to condition the electrical energy produced by the power subsystem, so that it is subsequently fed into the grid or used directly in the plant itself.

Finally, it is important to highlight the vital importance of a Supervisory Control and Data Acquisition (SCADA) subsystem to be able to analyze the operations carried out in the plant and evaluate its performance, thus offering possibilities for future improvements.

We can classify solar power plants according to the type of collector used to concentrate sunlight:

Parabolic trough solar power plant.

The operating basis is the same as the previous one. In this case, there is a set of parabolic trough collectors, through which a tube passes just at the focal point of these collectors. This results in the concentration of the incident sunlight in the tube, through which a heat transfer fluid circulates.

Solar power plant with Fresnel reflectors

In this case, the receiver on which the sun's rays are concentrated is higher than the collectors, as in the tower solar power plant. The operation is similar, although these collectors are located much closer to the receiver, which is shaped like a tube and is arranged along the entire length of the collector. It is the cheapest option due to the materials used and the simple operation, although they have a considerably lower yield compared to the other options.

How do solar thermal power plants work?

The operation of a solar thermal power plant is based on a technique that collects the sun's rays. Subsequently, the energy is concentrated in a heat carrier, which in most cases contains water. This type of storage is one of the most common today, as its technology is based on molten salts in thermal storage. With this stored heat, electricity can be generated if another liquid, usually water, is brought to boiling point.

In other words, the solar thermal power plant is where the sun's heat is used to bring water to boiling point, generating steam that will move the generator, with the end product being electrical energy. In order to increase the heat, a large amount of energy from the sun's rays must be gathered in an adequate manner.

Working temperature

In order to achieve optimum thermodynamic performance, temperatures must reach 100°C and up to 300°C, since at lower temperatures they will not be able to provide good performance. The collection of this solar energy is done by means of collectors. These collectors can be mirrors that point to a central tower where the heat that will later heat the fluids is generated or other types of collectors that concentrate the heat in a tube through which the heat transfer fluid circulates.

In this way, it can be said that it is a method of unlimited energy since its main source is solar energy and it is considered renewable energy. This reduces the manufacture of fossil fuels and significantly reduces the amount of this energy that we use.