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11ТЕХНИЧЕСКИЕ НАУКИ
FEATURES OF OPERATION OF SOLAR POWER INSTALLATIONS IN VARIOUS CLIMATE CONDITIONS
ISOZODA DILOVARSHOKH TARIK
Candidate of Chemical Sciences, Associate Professor, Rector of the Tajik Energy University,
Kushoniyon district, Tajikistan
MAKHSUMOV ILKHOM BURKHONOVICH
Candidate of Technical Sciences, Head of the Department of Relay Protection and Automation of the Tajik Power Engineering Institute, Kushoniyon district, Tajikistan
ODINAEV NEKKADAM KHUSHKADAMOVICH
Candidate of Technical Sciences, Dean of the Faculty of Electromechanics and Innovative Technologies of the Tajik Power Engineering Institute, Kushoniyon district, Tajikistan
ABDULLOEV BAKHTIOR TOLIBJONOVICH
Candidate of Technical Sciences, Senior Lecturer at the Department of Relay Protection and Automation of the Tajik Power Engineering Institute, Kushoniyon District, Tajikistan
Annotation. The article shows the problems that exist in solar energy during the operation of power plants in various climatic conditions, provides possible solutions and developments that help reduce negative factors for the generation of electrical energy by solar modules.
Keywords: solar power plants, pollution, overheating, icing, orientation of solar modules.
Introduction
Solar energy according to the latest trends is rapidly developing. This development is observed not only in countries with increased insolation, but also in other, more northern regions, including our country. This is explained by the introduction and development of devices that capture not only direct sunlight, but also scattered (diffuse) solar radiation and have a high degree of solar energy conversion efficiency.
However, during the operation of solar power plants, there are problems that lead to underproduction of electricity, the rapid failure of solar modules, a reduction in the service life and, related to this in the future, the problems of recycling used solar panels. The experience of operating solar power plants has shown that these problems are solved in one way or another, depending on the place and climatic conditions of operation.
Let's consider the most characteristic reasons that reduce photogeneration at solar power plants.
1. Dust content of solar modules
No matter how high the conversion rate of solar energy is, electricity production may decrease due to pollution of the surface of the solar module. Pollution can reduce the efficiency of solar installations by 25-30% due to surface shading and reduced absorption of sunlight. Such a problem is in any region where solar power plants are operated. In southern countries, pollution occurs due to dust storms, deposition of pollen and leaves of plants, pollution by birds and animals. For industrial areas, these are precipitation containing mixtures, emissions from industrial enterprises, transport, etc., which significantly reduce the production of electricity at solar power plants.
Such a situation is observed, for example, for the territory of industrial Chelyabinsk and other cities of the region. Dust particles, depending on their size, can stay in the atmosphere for different periods of time. The smaller they are, the longer their time in the air. Fine dust settles on the front
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surface of the modules located in the emission distribution zone and literally eats into the glass structure. It is very difficult to clean such a dust layer. There are several ways to clean dusty surfaces of solar modules. For example, for small areas, manual cleaning is used. For large volumes, a mechanical or robotic cleaning system is used. However, all of them are associated with significant financial and time costs, require human and water resources.
Therefore, dusting and pollution is easier to prevent than to spend huge amounts of money on cleaning. The device developed by us is intended for this purpose. The operation of the device is based on the principle of electron-ion technology (EIT) [1].
The device is a grid of thin wire, which is supplied with a high (9-12 kV) voltage. Rows of wire, which play the role of collecting electrodes, are connected to the terminal of a high voltage source (HVS) with a negative potential (Fig. 1)
Air containing suspended particles
Figure 1. Scheme of the device for protecting the solar module from dust pollution
The cleaning process occurs due to the impact of several electric forces of the interelectrode gap on a charged dust particle. Having their positive charge, the particles are deposited on the nearest negative electrode. The surface of the module remains clean, and the grille is removed and washed at regular intervals. The degree of capture of fine particles is calculated based on the Deutsch formula, taking into account the forces of gravity, panderomotor force, drag force of the medium and dust characteristics:
For dust particles with a natural electric charge, the degree of purification is 77%, and when using corona electrodes, which additionally charge dust particles, it reaches 95%. This way of preventing pollution will be quite effective with large arrays of solar panels.
2. Overheating of solar modules
This rather serious problem is typical for regions with elevated air temperatures. It is known that for every 5°C increase in ambient temperature above the standard 25°C, the predicted DC power
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output can decrease by 2.25%. It should also be taken into account that if overheating is constant, then degradation of the modules occurs and their photogeneration decreases. Decrease in the energy characteristics of the solar module with an increase temperature can be seen from its current-voltage (CV) and power characteristics.
This problem has become serious at the Orsk solar power plant in the Orenburg region. The air temperature in the summer months in 2019 was observed up to 40 degrees, and in the former Soviet republics of Central Asia, this temperature is normal. To protect the modules from overheating, various methods are currently used - from cooling with water to the use of complex heat removal mechanisms. In some cases, the use of such methods justifies itself, but for large solar power plants, simple, inexpensive and effective means are needed.
We suggested using a special structured film based on a hologram as a thermal protection. Due to the internal structure of the film, the infrared (thermal) component of the solar spectrum is reflected in it and the surface of the module does not overheat. Field tests in the Republic of Tajikistan have shown that the use of the film prevents overheating of the panel and at the same time photogeneration is slightly increased, which suggests that the use of the developed films on a large Solar Power Plant will be quite efficient [3].
On fig. 2 shows images of modules obtained with a thermal imager, with and without film.
a) b)
Figure 2. Infrared images of the solar module: a) without film, b) with film
The difference in temperature values is explained by the fact that the structured film hologram pattern allows concentrating the sun's rays, thereby increasing the performance of solar modules without reducing the volt-ampere and power indicators, while protecting the module surface from overheating.
3. Icing modules
This problem exists mainly not only for regions with long cold periods of the year, but also for places where precipitation in the form of ice and snow is possible. A decrease in ambient temperature does not significantly affect photogeneration, but ice or snow covering the module, similar to surface pollution, can significantly reduce power generation.
To solve this problem, the authors of [2] proposed the use of an electrothermal anti-icing system for the solar module (Fig. 3):
1 2 3 4
Figure 3. The device of the heating system (internal elements of the solar module): 1 - solar module frame; 2 - solar cell; 3 - front panel; 4 -current-carrying circuit; 5 - heat-
insulating material (polystyrene); 6 - foil isolon.
Conductive cables are connected either manually or automatically when precipitation or temperature sensors are triggered. Thermal energy is transferred from the conductive loop to the inner surface of the solar module and from there via heat transfer to the front panel. Under the influence of temperature, snow or ice melts, while the ice crust does not form.
The developed system is energy efficient, since 10 times less energy is spent to heat the solar module than the amount of energy generated by the module.
4. Orientation of solar modules
The use of solar tracking systems (trackers) undoubtedly leads to an increase in electricity generation by solar power plants. For these purposes, either uniaxial or biaxial orientation systems are used. They tend to be discrete or have only a few fixed tracker positions during daylight hours. In addition, to date, both of them have reached a relative efficiency limit (for 2-axis systems, it is approximately 40%). If there is no rapid growth in the efficiency of solar cells, the development of solar energy can go along the path of improving and attracting new methods and objects that are not included in the traditional paradigm of creating solar tracking systems and objects that can obtain more efficient results of solar energy conversion [4]. In order to track the point of maximum power, which is obtained at a right angle of the beam to the surface, a constant movement of the module behind the sun is necessary. The concept of designing and creating such systems is based on a fundamentally new three-coordinate positional spherical manipulator with a solar battery installed on a movable platform, driven by three coaxial valve inductor motors controlled by an extreme regulation system to track the point of maximum energy efficiency. The manipulator is controlled using a developed and patented program [5].
V,
f
Figure 4. Movement trajectories of the manipulator platform in space
The development of the complex was supported by a grant from the Russian Foundation for Basic Research - PhD students, in 2019 No. 19-31-90156 "Fundamental research of the synergistic effect from the combination of a discrete structure (double gear) of gearless valve-reluctance electric drives of spherical positional parallel manipulators with a multi-parameter system of extreme control and its impact on the energy efficiency of solar tracking systems (with the prospect of using other classes in position-tracking systems)". It should be noted that this orientation system will find its application not only in solar energy, but also in navigation systems of any complexity.
Conclusion
In this paper, we consider the peculiarity of the operation of solar systems in different climatic conditions, in order to find ways to improve their efficiency. The dusting of solar modules and their negative impact on the efficiency of photovoltaic modules are considered. To improve the efficiency of the modules and prevent dusting, a device has been developed that is based on the principle of electron-ion technology and is capable of cleaning dust particles with a natural electric charge of up to 77%. Another feature that is considered in the work is the overheating of solar modules in high temperature operating conditions. For the efficient operation of solar modules, the authors developed a holographic thermal protective film that allows to reduce the temperature of the module by 4 degrees in hot conditions. Icing is another feature of the modules that, in low temperature conditions, the solar system may encounter. Icing of modules occurs during their operation in conditions of precipitation in the form of ice and snow. To solve this problem, it was proposed to use an electrothermal anti-icing system for the solar module, which consumes 10 times less energy to heat the module. And also in this work the problem of orientation of solar modules is considered. To solve this problem, the authors developed a solar tracking system for efficient operation of solar modules.
REFERENS:
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2. Dolgosheev V.V., Martyanov A.S., Korobatov D.V., Bodrova E.S. Electrothermal anti-icing system of the solar module. Alternative Energy and Ecology (ISJAEE). 2017; (10-12):24-32. https://doi.org/10.15518/isjaee.2017.10-12.024-032.
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