INCREASING THE ENERGY EFFICIENCY OF AN AUTONOMOUS SOLAR PLANT WITH A STATIONARY CONCENTRATOR

ABSTRACT

The article discusses ways to increase the energy efficiency of a solar installation using automation, the choice of the optimal structural scheme, as well as accepted methods of orientation of the installation to the sun and the use of a convenient tracking system.

АННОТАЦИЯ

В статье рассматриваются способы повышения энергоэффективности солнечной установки с помощью автоматизации, выбор оптимальной конструктивной схемы, а также принятые способы ориентации установки на солнце и использование удобной системы слежения.

Keywords: Solar installation, orientation, automatic tracking system, control signal, threshold, tracking schedule, differential sensor, improving device efficiency

Ключевые слова: Солнечная установка, ориентация, автоматическая система слежения, управляющий сигнал, порог, график слежения, дифференциальный датчик, повышение эффективности устройства

I. Introduction. Humanity needs energy, and its needs are increasing every year.  At the same time, the reserves of traditional natural fuels (oil, coal, gas, etc.) are finite.  In connection with these problems, it is becoming increasingly necessary to use non-traditional energy resources, primarily solar, wind, geothermal energy, along with the introduction of energy-saving technologies.

At present, in Uzbekistan there is an acute problem of the development of energy-saving and environmentally friendly technologies and industries.  At the same time, it is possible to achieve energy saving in production and at home not only by limiting energy consumption, but also by making optimal use of renewable energy sources.  Among renewable energy sources, solar radiation is the most promising in terms of the scale of resources, environmental cleanliness and ubiquity.  The climatic and geographical conditions of our state are such that the sun is the most acceptable and promising source of energy.

The improvement of autonomous solar power plants (ASEU) primarily depends on the rational use of their technical capabilities.  Therefore, when designing modern efficient autonomous solar power plants, the problem of system design of power plants should be solved in order to increase their energy efficiency.

To optimize solar installation it is advisable to use optical and software system for the tracking of solar concentrators. This allows to achieve the required accuracy and the operational control of tracking systems, and therefore contribute to the energy efficiency hub for various purposes. As you know, there are developed various systems of power plants based on conversion of solar energy into thermal energy.

II. Improving the efficiency of energy systems. The efficiency of energy systems in their long-term functioning, to a large extent depends on the chosen structural scheme, design, materials, accepted ways of exploitation and utilization of energy sources [1]. Currently widely used structural diagram energy systems and facilities without the implementation of extreme regulatory regime of its power [2]. In such stand-alone solar power plants are mainly used simple temperature controllers, current, voltage, charge and discharge the battery, and others. To increase the coefficient of energy efficiency of a solar power plant of not less than 30-50% is possible by the following main ways [3]:

– implementation of the mode of selection of hot water or power;

– implementation of continuous automatic tracking of a solar collector or photovoltaic panels with the Sun;

– optimization design of the solar cell with the aim of achieving a minimum heating of the solar cells.

- design optimization of heat sink and its thermal insulation to achieve minimum heat loss and maximum heat performance.

The effect of the implementation of the mode of power regulation of solar installations depends on the range of variation of the operating temperature of a solar power plant. Solar installations are used in widely varying operating conditions. They are strongly influenced by the environment. Their performance characteristics are nonlinearity and instability.

Implementation of automatic tracking solar plants follow the Sun, is the most effective way to improve energy efficiency of power plants.

From a preliminary analysis of energy efficiency of systems of automatic tracking of the Sun is that the efficiency for Fergana relative to the horizontal location of solar collectors is:

– when placing the solar collector at an angle equal to the latitude location where you are installing the solar installation – 40%;

– when using single-axis system for solar tracking 62 percent;

– if you use dual-axis tracking system the Sun is 71%.

The average for various regions of Uzbekistan energy efficiency through the use of systems for tracking the Sun increases by 11% for single-axis systems and 26% for biaxial.

The feasibility of optimizing the design of solar collectors with the aim of improving the energy efficiency ratio is due to the sensitivity of the heat of solar units to the temperature. With increasing temperature of the heat efficiency of solar installations, and most other solar plants, is reduced. It is therefore necessary to take all measures to optimize the operating temperature of the heat sink and its thermal insulation.

Stepping method of search of extremum power is most suitable for use in standalone solar power plants, since approval extreme regulator with automatic shut-off valve operating temperature of the coolant or the charger is carried out simply by a discrete adjustment of the feedback circuit to the channel voltage of the solar battery.

The regulator of any extreme performance (analog-to-digital, digital, microprocessor) hardly increases the weight control apparatus has small power consumption and increases the efficiency of the solar installation to a maximum value [1, 4].

III. The choice of optimal structural scheme of the automated system for solar power installations.

In Fig. 1 is a block diagram of the automated system for solar power installations.

This system includes two chains of independent control.  In the first chain, an automatic tracking system for solar collectors based on the Arduino microcontroller was developed.  The controller, receiving signals from photoelectric tracking sensors, generates a control signal in a discrete format.  The generated signal is issued to the control unit, which, amplifying, controls the operation of the electric drive, consisting of a single-turn SEM electric motor (electric single-turn mechanism) with a gearbox.  The tracking mechanism provides guidance of the solar collector in the sun.  The permissible error (threshold) between the signals in the inclined planes of the sensor photocells, at which it is necessary to monitor the collector for the Sun, is 5% (this value can be set in the controller) [5].

Figure 1. Solar Collector Automation System

 Once the optimal position is found, the microcontroller sets a timer and waits for the next cycle of work after a specified time.  This process will continue until the reset button is pressed.  The tracking graph is shown in the following figure [6].

Figure 2. Schedule tracking solar installation for the sun

In the second chain, the microcontroller maintains the temperature parameter of the input and output of the heated water in the collector.  The following instruments and devices participate in the automation chain:

- microprocessor meter regulator TPM 212 (analog output signal);

- narrowing device (washer) to create a differential pressure;

- differential sensor (differential meter (input signal 4-20 mA));

- temperature sensor - thermocouple (measuring range up to 850 degrees);

- electric valve (input signal 4-20 mA);

- A computer for recording and recording data.

The technical result of the second part of automation is to increase the efficiency and reliability of the solar power plant.  Improving the efficiency of the device is achieved by improving the mode of thermal accumulation, since a portion of hot water not used by the consumer, making a repeated cycle of receipt in the solar thermal collector, transfers part of its energy to the heat accumulator.  Improving the reliability of the solar device is achieved by increasing the rate of periodic heat removal of solar radiation in batches, by applying water selection over an automatically set temperature range, which prevents the accumulation of scale in the inner surfaces of the working channels of the solar thermal collector [7].

Conclusion

Thus, achieving the energy efficiency of a solar installation can be achieved in the following ways:

- it is advisable to track the solar collectors behind the Sun on the basis of the requirements to ensure accuracy of pointing to the Sun and the minimum consumption of electric energy by electric drives;

- in order to save energy, at the end of the cycle of pointing the solar collector to the Sun, it is necessary to turn off the drivers of the electric drive and organize the positioning mode, which can significantly reduce the consumption of electric energy.

- An analysis of the developed designs of orienting systems showed that for standard designs, the tracking error is of the order of 0.1-0.6 degrees.  considered valid.  However, it should be noted that the higher the tracking accuracy, the higher the efficiency of the solar power plant.

- increasing the reliability of the solar device is achieved by increasing the rate of periodic heat removal of solar radiation in batches, by applying water selection over an automatically set temperature range, which prevents the accumulation of scale in the inner surfaces of the working channels of the solar thermal collector.

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