Thermoelectric energy

Solar thermoelectric energy includes a group of new technologies to concentrate the energy coming from the Sun with the aim of reaching medium and high temperatures enabling the production of electric energy. This will be possible by injecting the steam generated at high pressure into the turbine that will activate an electric generator.

If we manage to apply and develop this technology, we could produce a very competitive energy, which is renewable and eco-friendly.

Solar thermoelectric energy can be classified into medium and high temperature systems, the difference between them is the temperature that exit fluids reach.

In medium temperature systems, the most usual applications that have been developed so far have been the production of very hot water and steam for industrial processes and the production of electricity in small power stations from 30 to 2,000 Kw. There are other applications such as desalination or refrigeration using solar energy. The maximum temperatures reached with these technologies are around 400º.

Regarding medium temperature stations, the most developed technology belongs to the Parabolic Cylinder Collectors.

In high temperature systems, solar radiation can be used for the production of electricity on a large scale. Using a classic process activating a turbine with pressurized steam turning heat into mechanical energy and later turning this mechanical energy into electrical energy. We can get high amounts of electricity in this way.

High temperature systems can be classified into Tower Thermoelectric Power Stations and Parabolic Dishes Thermoelectric Power Stations. Both are based on technological processes similar to those used in medium temperature systems, but they have a high capacity to concentrate the solar rays and to reach higher temperatures, around 800ºC reaching sometimes 1000ºC in the most advanced Tower Thermoelectric Power Stations. These ones are composed of a group of sollar mirrors to concentrate the solar radiation in a collector placed at the central tower.

Power stations using parabolic dishes use a parabolic reflector with the shape of a dish to concentrate the solar light on a collector placed on a focal point of the dish. The dish absorbs the reflected energy, making the fluid reach a temperature of about 750ºC. This heat is used to produce electricity by changing it into mechanical energy using the Stirling engine or the Brayton turbines.

Parabolic dish concentrators are small units with an engine-generator on the focal point of the reflector. Typical sizes range from 5 to 15 metres of diameter and from 5 to 50 Kw of electric energy.

Thanks to its parabolic optics, ideal to focalize a point, and its solar trajectory control, dish concentrators achieve maximum concentration of solar energy and therefore the best output if we compare it to other types of concentrators.

Between the characteristics of the concentration collectors we could highlight that they take advantage of the direct solar radiation. That is to say, they can only pick up solar rays that really reach their surface. They cannot pick up diffused solar radiation. This makes them ideal for Andalusia where the climate is very sunny.

Solar thermoelectrical energy will grow a lot over the next years since the technology has been proved and the central and regional government is supporting it strongly. The new projects will enable to make use of an abundant resource in areas where other renewable technologies cannot work. For this reason, we must support this technology in order to reach a sustainable growth.

Source: Ecological Research Institute.

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