Solar power plants - operating principles

Solar power plants: principles of operation and types of complex systems

In order to obtain electric current under the influence of sunlight in volumes that are significant for the economic sector and households, two technologies have been developed:

·         photovoltaic - solar panels immediately convert solarization into electricity;

·         thermoelectric installations - a liquid heat transfer medium is used.

Combined solar power plants may well be attributed to the third type. For correct operation and high efficiency of the photovoltaic modules, they must be steadily cooled. This became the point of contact for both technologies. Hybrid systems collect electricity from both the panels and the cooling loop, which dramatically increases the efficiency and hence the profitability of the installation.

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Generation of electricity by solar panels

Photovoltaic effect

·         The absorption of a quantum by an electron leads to its transition to a higher energy level, that is, to the outer orbit of the atom. Here, the connection with the nucleus weakens, the electron leaves the atomic limits and, under the action of the Galvani potential (internal electric field), rushes to the anode. Thus, one component of the electric current is formed.

·         After the electron leaves, a vacant place remains in its place, which is called a "hole". It is occupied by electrons from a neighboring atom located in the zone of a lower positive potential. That is, in fact, the "holes" move to the cathode. This is the second component of the photovoltaic current.

The source of the Galvani potential is the interface between the sun-sensitive semiconductors. Solar panels, in turn, are arrays of such cells that are electrically connected.

Types of photovoltaic cells

The most common are monocrystalline (the basis is a single silicon crystal with a homogeneous structure) and polycrystalline (compounds of dissimilar small silicon crystals) panels. They differ somewhat in efficiency and price, but in principle they are used on equal terms in solar power plants.

Another modification is film polymer solar cells. Materials with different functions - electron donors and electron acceptors - are deposited on a transparent base layer by layer. The result is a flexible, thin and light structure, but its area efficiency is much lower. In addition to scientific laboratories, the technology is used to create energy efficient windows in homes and cars.

In the spring of 2018, a research group at the University of Warwick (Coventry, UK) announced the discovery of a third type of photovoltaic effect called flexo-photovoltaics. The difference lies in the fact that the deformation gradient acts as an impetus for the generation of solar electric current. That is, if crystals of Si, TiO2 or SrTiO3 are deformed with a sharp object, they turn into photovoltaic cells. This discovery could significantly reduce the cost of building solar power plants.

The main units of a solar power plant based on panels

In order for the electricity generated by the panels to be consumed by household appliances, you will need:

·         the panel itself;

·         inverter - converts direct current into alternating current of a given frequency;

·         drive, that is, the battery;

·         charge / discharge controller that extends the life of expensive storage batteries;

·         special converters and meters, if the system is interfaced with the public power grid.

Thermoelectric solar plants

The main difference is that electricity is produced indirectly. The main structural element is heliostats - huge mirrors coupled with a positioning mechanism relative to the sun.

Photo Solar power plants: principles of operation and types of complex systems

Heliostats can take different shapes - round parabolic, parabolic-cylindrical concentrators. They collect sunlight into a concentrated beam and direct it to a heat sink filled with a heat transfer fluid. Most often, for these purposes, mineral oils with a high boiling point are used, which are called terminol.