USE OF ENVIRONMENTALLY SAFE SOLAR ENERGY FOR LOW POWER WATER SUPPLY IN RURAL AREAS

ABSTRACT

The article presents the results of the development of a universal solar power plant for individual use for the electrification of farms and water lifting, based in the Tashkent State Technical University at the Faculty of Physics and Engineering. The developed unit is designed to lift water from wells and boreholes, and has a capacity of 10 cub. meters per day.

АННОТАЦИЯ

В статье представлены результаты разработки универсальной солнечной электростанции индивидуального использования для электрификации фермерских хозяйств и подъема воды, основанной в Ташкентском государственном техническом университете на Инженерно-физическом факультете. Установка предназначена для подъема воды из колодцев и скважин, имеет производительность около 10 куб. м. в сутки.

Keywords: intellectual charge controller, lead-acid battery, sulfation, battery life, water pump.

Ключевые слова: интеллектуальный контроллер, свинцово-кислотный аккумулятор, сульфатирование, ресурс аккумулятора, водяной насос.

1. Introduction.  It is undeniable that nowadays, the issues of transformation and the use of an inexhaustible and environmentally friendly solar energy are discussed more frequently than previously. Implementation of solar energy will facilitate or eliminate such problems as preservation of natural resources, improvement ecology, and reduction of carbon emissions and improving of living conditions. One of the potential areas of advantageous solar power implementation is getting elec­tricity using photovoltaic (solar) elements. Moreover, it would be more beneficial, if photovoltaic cells were used in areas, where there is no access to a steady power supply. In these regions, the most perspective option is the electrification of power pumps to lift water from wells and lighting munic­ipal buildings. Inasmuch as there is a very large number of potential .consumers of low-powered wa­ter-lifting plant with a capacity of consumption less than one cubic meter of water per day. This is a rural farmstead, field camps, farmers, and other non electrified remote places of residence which are located in rural areas without constant electricity and water supply.

4 The prototype accomplishes small-scale water-lifting; it is versatile and has the function of small solar power plants.

PV part of the installation include:

• photovoltaic solar panels (100 watts or more);

• lead-acid battery;

• intellectual charge controller;

• inverter.

Water-lifting part of the installation includes:

• pump controller;

• submersible vibrating pump (capacity of about 300W).

Pump controller is used to adjust the water level in the water tank. The pump controller is installed after the batteries.

2. The existing technical solutions and their drawbacks. Batteries have a limited storage capacity for energy and once they are “full”, excess charge can begin to cause harm. There are two types of controllers: series and shunt. Series controllers stop the flow of current by opening the circuit between the battery and the PV array. Shunt control­lers divert the PV array current from the battery, sometimes to an artificial load. Both types use sol­id, state battery voltage measurement devices and shunt controllers are 100% solid state. Several charge controllers on the market use a 3 stage charging approach with bulk, absorption, and float modes to ensure that voltage and. current settings accurately match the batteries' actual state of charge. This reduces the time needed to bring the battery to full charge and can extend the life of the battery.

Stand-alone PV systems are very important for the rational choice of battery capacity and proper control of the battery charge and discharge. In this sense, water lifting units have significant differences. Mainly solar power energy is consumed during evening and night time, and most of the time the batteries either are charged, or are discharged. In the water-lifting installations situation is different.

To reduce the required battery capacity and increase the efficiency of the water pump, solar power and battery are used simultaneously. By the end of a sunny day the battery is almost fully discharged. Therefore, all night it will be stored in a discharged state. However storage in the dis­charged state is unacceptable for lead-acid battery, since it leads to a rapid sulfation (crystallization of lead sulfate) of the plates and damage of the battery for a few months (.http://www,wmdsimxom/Batteries/BatteiyJFAQ.htm).

Sulfation is a normal process that occurs in lead-acid batteries resulting from prolonged op­eration at partial states of charge. Even batteries which are frequently fully charged suffer from the effects of sulfation as the battery ages. The sulfation process involves the growth of lead sulfate crystals on the positive plate, decreasing the active area and capacity of the cell. During normal battery discharge, the active materials of the plates are converted to lead sulfate. The deeper the discharge, the greater the amount of active material that is converted to lead sulfate. During recharge, the lead sulfate is converted back into lead dioxide and sponge lead on the positive and negative plates, respectively. If the battery is recharged soon after being discharged, the lead sulfate converts easily back into the active materials.

However, if a lead-acid battery is left at less than full state of charge for prolonged periods (days or weeks), the lead sulfate crystallizes on the plate and inhibits the conversion back to the active materials during recharge. The crystals essentially “lock away” active material and prevent it prom reforming into lead and lead dioxide, effectively reducing the capacity of the battery. If the lead sulfate crystals grow too large, they can cause physical damage to the plates. Sulfation also leads to higher internal resistance within the battery, making it more difficult to recharge.

Sulfation is a common problem experienced with lead-acid batteries in many PV applications. As the PV array is sized to meet the load under average conditions, the battery must sometimes be used to supply reserve energy, during periods of. excessive load usage or below average insolation. As a consequence, batteries in most PV systems normally operate for some length of time over the course of a year at partial states of charge, resulting in some degree of sulfation/The longer thе period and greater the depth of discharge, the greater the extent of sulfation.

To minimize sulfation of lead acid batteries in photovoltaic systems, the PV array is generally designed to recharge the battery on the average daily conditions during the worst insolation month of the year. By sizing for the worst month’s weather, the PV array has the best chance of minimizing the seasonal battery depth of discharge. In hybrid systems using a backup source such as a generator or wind turbine, the backup source can be effectively used to keep the batteries fully charged even if the PV array can not. In general, proper battery and array sizing, as well as periodic equalization charges can minimize the onset of sulfation (Don A. Gagon, 1999).

3. The proposed solution. In order to resolve the problem, there was developed a intellectual controller of battery charge-discharge, which works according to the principle of predicting the state of the battery and consequently prevents the rapid sulfation of the plates (Gumerov Yu., Zuev A.,2007).

In operation, the solar water-lifting plant is monitored current charge (from solar), current discharge (the current water pump) and the degree of battery charge (voltage and temperature on it). Using the information about the current charge and time of day you can predict the necessary time off for the pump (information about previous sunny day is also used). The remainder of the current solar time of the day should be sufficient to obtain the necessary degree of battery charge. Thus, the degree of battery charge at the end of a sunny day can be adjusted up to 100%, which is very constructive effect on their lifespan. In the intellectual charge controller is used microcontroller ATMegal6.

4. Results. The proposed technical solution of the controller of battery charge in water-lifting installation can reduce the required electrical capacity of batteries and increase their life (above 200%), and thereby obtain significant advantages in price and maintenance of costs (up to 30% of total costs during the product life cycle).

Figure 1. Photovoltaic solar panels with the developed intellectual charge controller

* Charge controller sense the level of charge in die batteries and will disconnect the solar array from the batteries as they reach full charge.

* The battery charger have MPPT function and can be used for low-power PV system ap­plications [3]. For MPPT function current-sensing techniques are used.

* For effective miniaturization, the battery charger is designed with high frequency operation.

* The charge controller will display interesting information about the system, including battery voltage and the amount of energy being generated by the solar array.

Characteristics of solar water-lifting system (fig. 2) with intellectual charge controller are in table 1.

Table1

Solar water-lilting system characteristics

Figure 2. Preliminary tests of solar water-lifting installation in capacity to 100 W, with height of lifting of water of 15-20meters.

Conclusions

The intellectual optimized charge profile, as presented in this paper, increase the battery, life more then 200%. It is makes installation very reliable and efficient, thereby obtain significant ad­vantages in price and maintenance of costs (up to 30% of total costs during the product life cycle),

References:

1. Yusupjanova M.B., Tashmukhamedova D.A., Umirzakov B.E. Composition, morphology and electronic structure of the nanophases created on the SiO2 surface by Ar+ ion bombardment // Technical Physics, 2016, Vol. 61, No. 4. p.627 – 629.
2. Tashmukhamedova D.A., Yusupjanova M. B., Tashatov A. K., Umirzakov B. E. Study of the Influence of Implanted Atoms on the Coefficients of the Sputtering of Silicon and Silicon with a Thin Oxide Film // Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques, 2018, Vol. 12, No. 5. pp. 902–905. (01.00.00, №39; №4 Journal Citation Reports, IF=0.36)
3. Тожибоев А.К., Султонов Ш.Д. Измерение, регистрация и обработка результатов основных характеристик гелиотехнических установок // Universum: технические науки : электрон. научн. журн. 2021. 11(92).
4. Тожибоев А. К., Хакимов М. Ф. Расчет оптических потерь и основные характеристики приемника параболоцилиндрической установки со стационарным концентратором //Экономика и социум. – 2020. – №. 7. – С. 410-418.
5. Тожибоев А. К., Немадалиева Ф. М. Комбинированные солнечные установки для теплоснабжения технологических процессов промышленных предприятий. результаты разработки и испытаний //Современные технологии в нефтегазовом деле-2018. – 2018. – С. 253-256.
6. Хакимов М. Ф., Тожибоев А. К., Сайитов Ш. С. Способы повышения энергетической эффективности автоматизированной солнечной установки //Актуальная наука. – 2019. – №. 11. – С. 29-33.
7. Эргашев С. Ф., Тожибоев А. К. Расчёт установленной и расчётной мощности бытовых электроприборов для инвертора с ограниченной выходной мощностью //Инженерные решения. – 2019. – №. 1. – С. 11-16.
8. Тожибоева М. Д., Хакимов М. Ф. Исследование спектральных характеристик прозрачно-тепловой изоляции приемника //Universum: технические науки. – 2021. – №. 10-5 (91). – С. 17-19.