Application of Renewable Energy in Agriculture of the Republic of Uzbekistan

Abstract

Among the Central Asian republics, Uzbekistan is unique in that approximately 80% of its territory lies within a plain, characterized by an arid geographic zone and dry climate. Agricultural production in these regions is possible only through artificial irrigation. In recent years, global climate change and challenges related to transboundary water use have led to a reduction in water availability. The average annual water allocation to Uzbekistan is estimated at 51–53 billion m³, of which 90–91% is consumed by the agricultural sector. Due to the uneven distribution of water resources and the complex topography of irrigated lands, water supply is supported by numerous pumping stations operated by the state, water users associations, farms, and clusters. Additionally, well-based pumping systems are employed to maintain groundwater levels and ensure irrigation. On average, these facilities consume around 8.0 billion kWh of electricity annually. The agricultural sector faces several critical challenges, including crop water deficits caused by water shortages, slow adoption of water-saving technologies, and limited implementation of drip irrigation on household plots, dachas, and greenhouses that play a key role in food supply. Moreover, the delivery of water to fertile lands situated far from main power lines and water sources remains problematic. This article aims to explore the integration of solar energy solutions to support drip irrigation in both large-scale agricultural lands (ω = 1.0–100.0 ha and above) and small-scale areas such as homestead plots, dachas, and greenhouses (ω = 0.01–1.0 ha), as well as their application in small- to medium-sized pumping stations. Based on the research and experimental design work carried out, three mobile photovoltaic units—MPPU-8-500-4000, MPPU-2-550-1100, and MPPU-4-500-2000—were developed and implemented to address water and energy shortages in agriculture.

1. Introduction

Between 1991 and 2024, the combined population of Central Asian countries grew substantially—from around 51.8 million to approximately 83.5 million—placing heavy pressure on regional resources [1]. During the same period, irrigated land expanded from roughly 7.421 million hectares in 1990 to about 10.38 million hectares by 2024 [2,3], further intensifying water demand. Climate change is reducing glacier areas, with projections suggesting up to a 40% loss [4,5]; this trend threatens fresh water supplies by reducing glacial runoff that feeds major rivers. The runoff of the Amu Darya River is expected to decline by 10–15%, and that of the Syr Darya by 6–10% [2,3], compromising regional water availability. At the same time, crop water requirements are forecasted to increase—by about 5% by 2030, 10% by 2050, and up to 16% by 2080 [6]—making irrigation even more demanding. Together, these combined factors jeopardize the region’s capacity to provide adequate drinking water and sustain food production for its growing population [7,8].

In the conditions of Central Asia, and including the Republic of Uzbekistan, where there is a large difference in the annual precipitation layer (90 ÷ 300 mm) and annual evaporation layer (1500 ÷ 2000 mm) (i.e., evaporation is more than precipitation: autumn-winter period 5 ÷ 7 times; in the growing season 17 ÷ 23 times), high temperature during almost the entire growing season, low relative air humidity, and lack of natural soil moisture prevent normal plant development [9]. Therefore, effective farming here is impossible without irrigation and reclamation.

Climate change strongly affects the hydrological cycle [10]. The hydrological cycle is a process of gradual increase or decrease in water resources (river, river basin) during some period of time. If in the 1960s in Central Asia the hydrological cycle of water bodies was 11 years, now this cycle is 4–7 years [10]. Thus, the duration of the hydrological cycle of water resources in Central Asian countries has decreased.

For instance, the severe decline in water availability that precipitated the 1999–2001 droughts in Karakalpakstan resulted in a marked contraction of irrigated agricultural areas. If in 1999 irrigated lands amounted to 500 thousand ha, in 2000 it decreased to 389.2 thousand ha, and in 2001 to 201.7 thousand ha [11]. According to the established limits, 6.5 billion m³ of water was annually allocated for irrigation of agricultural crops during the growing season. Water availability in the republic, for example, in May 2000 amounted to 45–50%, and in the following 3 months (June, July, August) it decreased from 48 to 19% of demand. In 2001, water availability in May, July, and August was 12, 19, and 16% of water demand, respectively.

In order to adapt agriculture to water scarcity under climate change, it is necessary to introduce water-saving technologies on all irrigated lands. At present, all countries of Central Asia are introducing various methods of water-saving technologies [12,13]. In the Republic of Uzbekistan, a number of decrees and resolutions of the President of the Republic of Uzbekistan aimed at efficient use of water resources and introduction of water-saving technologies in agriculture have been adopted [14,15,16]. The concept of water sector development in the Republic of Uzbekistan for 2020–2030 states, “to bring the total area of land covered by water-saving technologies in crop irrigation to 2 million hectares, including drip irrigation technologies—up to 600 thousand hectares” [14].

Today in Uzbekistan, modern types of water-saving technologies such as drip irrigation (water saving in row crops up to 40–60% in gardens up to 60–80%) are widely used [17,18,19,20], sprinkling [21] and its types—“Center Pivot” [22,23], “Impact Sprinkler” [24,25] and “Rainstar Raveler” [26], which save water up to 40%, as well as “Pulsar” [27], which saves up to 20% of water resources.

Irrigation water in the Republic of Uzbekistan is the most expensive [28,29,30]. Because of the uneven distribution of water resources and the complex topography of irrigated areas, approximately 60 percent of the 4.3 million hectares under irrigation are supplied via 1687 state-operated pumping stations and installations. They have the following average indicators: water flow rate—6909 m³/s; annual volume of water supplied to the fields—28.3 billion m³; total volume of pumped water due to the operation of cascades of pumping stations is 59.9 billion m³; annual electricity consumption is about 8 billion kW∙h [15,27]. Especially large and unique systems of machine irrigation are the Karshi Main Canal with 7 cascades of pumping stations, and the Amu-Bukhara Machine Canal. The two canals have 689 thousand hectares of irrigated land (679 thousand hectares in the Republic of Uzbekistan and 10 thousand hectares in Turkmenistan), where 2.5 million people live and work [30,31].

In addition, more than 10,280 small pumping stations and installations are operated by farms and clusters [15]. To regulate the groundwater table and irrigate agricultural land, as well as to provide rural populations with drinking water, 12,400 vertical wells with vertical pumping units are operated [15]. Water supply for all types of water-saving technologies introduced in agriculture in Uzbekistan is carried out through the above-mentioned pumping stations and installations or through separately installed pumping units [28]. According to data from the Ministry of Water Resources of the Republic of Uzbekistan, the cost of irrigation water supplied via pumped (mechanized) systems typically exceeds that of gravity-fed delivery by a factor of 8–10.

With climate change and limited access to non-renewable energy sources around the world, since the 1980s, countries have been seriously concerned about environmental safety about the ecological purity of the land and water that will soon be inherited by our descendants. Moreover, experts have long warned that, should production continue to expand at current rates—and if the energy enabling that production remains reliant on existing sources—within approximately one century, the planet would likely become thoroughly contaminated, with scarcely any pristine ecosystems remaining. Therefore, the generation of environmentally friendly or “green” energy is important for reducing environmental pollution, combating climate change, and ensuring sustainable development [32]. Integrating photovoltaic systems into irrigation management to improve resource efficiency and sustainability in water-scarce regions [33].

This article aims to explore the integration of solar energy solutions to support drip irrigation in both large-scale agricultural lands (ω = 1.0–100.0 ha and above) and small-scale areas such as homestead, dacha plots, and greenhouses (ω = 0.01–1.0 ha), as well as their application in small to medium-sized pumping stations.

2. Materials and Methods

The developed 3 mobile photovoltaic installations were tested in the field in various regions of Uzbekistan in the period 2022–2024. The Mobile Photovoltaic Power Unit (MPPU-8-500-4000) was tested on farms with an area of 8–10 hectares in Namangan, Kashkadarya, Khorezm, Bukhara, Surkhandarya provinces, and the Republic of Karakalpakstan. The Mobile Photovoltaic Power Unit (MPPU-2-550-1100) was tested in household and dacha plots of the Andijan, Kashkadarya, Tashkent, and Namangan provinces. The Mobile Photovoltaic Power Unit (MPPU-4-500-2000) was tested at 29 irrigation pumping stations in the Andijan, Namangan, Ferghana, Jizzakh, Surkhandarya, Bukhara, and Navai provinces of Uzbekistan. During the tests, there were used research methods such as observation, instrumental measurements, parametric tests, and data analysis. Attention was also paid to drip irrigation regimes for crops (cucumbers) during the joint operation of a mobile photovoltaic installation. Drip irrigation of cucumbers was mainly carried out after sunset. Mobile Photovoltaic Power Unit MPPU-2-550-1100 was operated as follows: all parts of the system were checked and put into working order; polyethylene pipes with droppers were stretched under cucumber seedlings; the tank for mineral fertilizers was filled with a solution of a certain concentration; photovoltaic panels (N = 1.1 kW) provided power to the pump supplying water, and it started work by filling a container with a volume of W = 2.0 m³ from the source. If there is no water source near the irrigated area, the installation can be filled with water from a remote source and delivered to the irrigation plot. By opening taps on the water tank and the fertilizer tank, water was supplied to the drip irrigation system, and the stability of the drippers was monitored. After the plants were saturated with water, the automatic irrigation system stopped supplying water. After the irrigation of the first cucumber plantation was completed, the drip pipes were collected and transferred to the next site. Subsequent irrigations were also performed in the above sequence.

During the growing season, the irrigation regime of cucumbers was also studied based on field experiments. The irrigation regime was studied in the following sequence: for each watering, the date of watering, its duration (beginning and end), as well as the total time spent on watering were recorded. The readings of the water measuring device were also taken—volumes (at the beginning and at the end of the tests), the total volume of water used for one irrigation, the ambient and air temperature were measured, including the temperature of the water supplied through the solar panel. At the end of the growing season, the following were calculated: the total time spent on watering during the growing season (ΣT); the readings of the water measuring device at the beginning and at the end of the experiments (ΣW); the total volume of water supplied (ΣW); and the average temperature of the atmosphere and the water supplied (by the photoelectric panel) to the drip system.

3. Results and Discussion

The territory of Central Asian countries, including the Republic of Uzbekistan, is rich in renewable energy sources such as the following: water; wind; solar; geothermal; and bioenergy [34,35,36]. According to the statement of the President of the Republic of Uzbekistan, the share of renewable energy sources in electricity generation in Uzbekistan will reach 54% by 2030.

In terms of renewable energy potential in Uzbekistan, solar energy is the leader, followed by water energy and then wind energy. Due to the high level of solar radiation in Uzbekistan, solar energy has great potential [35]. According to the Asian Development Bank, the highest solar insolation in Uzbekistan is 1800 to 2000 kW/m² per year (Figure 1). Uzbekistan has an average of 330 sunny days per year, a duration of sunshine at +42 °C (in desert areas the temperature rises to +70 °C) 2850–3050 h, duration of daylight hours of 14–17 h. The territory of the Republic of Uzbekistan at latitudes 16 and 20, the duration of daylight hours is 16–17 h [35,37,38].

Solar energy is increasingly integrated throughout the agricultural sector and the broader economy. It powers solar-driven pumping systems that support water-saving irrigation technologies—including drip irrigation, sprinkle irrigation, and subsurface irrigation methods—and provides electricity for lighting and low-power field operations within research stations, residential buildings, livestock and poultry facilities, rural structures, and greenhouses. Additionally, solar energy is employed in the design of crop drying systems for fruits and other produce [39,40,41].

In 2015, the “TashGRES” pumping station—operated by the Tashkent Regional Department of “Pumping Stations and Energy”—was retrofitted with a 4.2 kW photovoltaic system to satisfy its auxiliary electrical demands, notably for lighting the station and its surroundings. This solar installation remains in continuous operation to date. The Danish company “Grundfos” started to install different SQFlex solar pumps (SQFlex 1, SQFlex 3A, SQFlex 5A, SQFlex 7, SQFlex 9, SQFlex 14) in different capacities (N = 100, 200, 400, 800, and 1700 W) to lift water from underground and aboveground water sources (Figure 2) [42].

Development, research, and implementation of mobile photovoltaic installations in agriculture were conducted in three directions. The research work was carried out on the basis of subprojects within the framework of the project “Modernization of the National Innovation System of Uzbekistan” of the Ministry of Innovative Development of the Republic of Uzbekistan, financed by the World Bank. Based on the conducted work, the following mobile photovoltaic installations were developed and implemented:

• Mobile Photovoltaic Power Unit (MPPU-8-500-4000) with capacity—N = 4000 W, providing electricity to water lifting plants for water supply for drip irrigation of lands with area—ω = 10 and more hectares.
• Mobile Photovoltaic Power Unit (MPPU-2-550-1100) with capacity—N = 1100 W, providing electricity to water lifting plants for water supply for drip irrigation of lands with area—ω = 0.01–1.0 hectares.
• Mobile Photovoltaic Power Unit (MPPU-4-500-2000) with capacity—N = 2000 W, providing electricity for the own needs of medium and small irrigation pumping stations (for pumping water from drainage systems and lighting).

Content of signs: M—mobile; P—photovoltaic; P—power; U—unit; numbers: first numbers—2, 4, 8 number of solar panels; second numbers—capacity of solar panels; third numbers—total capacity of the installation.

3.1. Mobile Photovoltaic Power Unit with Capacity—N = 4000 W (MPPU-8-500-4000)

When using autonomous photovoltaic power plants in continuous mode, the batteries will also operate under constant load without drastic changes in basic parameters and service life. In the case of variable operation modes and long-term shutdowns, being without shelter or conservation, battery parameters and lifetime may change significantly.

Usually, autonomous photovoltaic power plants used in drip irrigation systems are installed permanently. After the irrigation period, they are left either on the field, covering them with polyethylene films or other temporary protective shelters, or transferred to sheltered places (sheds, rooms, etc.). Being subjected to dismantling after the end of the irrigation period and installation before the irrigation period, photovoltaic installations may be subjected to mechanical impacts. Parts of a PV system left in the field without shelter or preservation may be subjected to the following damage [37,43]:

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mechanical impacts-impacts or vibrations, which may damage internal components; and structures, as well as rupture of electrical connections;

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damage to grounding and cable insulation;

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corrosion or oxidation of contacts or connections;

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discharge of batteries (when stored for more than 1 week—loss of capacity by 30–40%, more than 1 month—by 80–100%, which can put it out of operation);

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damage of photovoltaic panels, inverters, connections and other parts under the influence of rain, snow, ice and moisture from them;

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in heavy snowfall or hurricane-force winds, panels and fasteners may snap off;

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and other damage.

To avoid these problems, all components of the PV power plant were placed on a mobile cart (Figure 3).

MPPU-8-500-4000 provides electric power to the pumping unit supplying water to the drip irrigation system. MPPU-8-500-4000 on a cart consists of 8 solar panels with a capacity of 500 Wh (total capacity 4.0 ÷ 4.2 kWh), inverters, batteries, controllers, and other parts, as well as a pumping unit that provides sufficient pressure and water flow for drip irrigation of gardens. MPPU-8-500-4000 on a cart has the following advantages compared to a stationary installation:

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can be used all year round;

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the capability to adjust the orientation of solar panels in accordance with the Sun’s daily trajectory can enhance electricity generation efficiency by up to 45%;

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moving the MPPU-8-500-4000 itself;

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to prevent efficiency losses in the photovoltaic system during hot summer conditions, the panels were equipped with a water-cooling system designed to maintain their operating temperature within the range of 25–28 °C;

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water supply to furrows and drip irrigation system.

The energy generated by MPPU-8-500-4000 can be consumed for the following additional functions:

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service of several fields (farms) during the period of (drip) irrigation;

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power supply of electrical appliances at small production facilities of farms in the fall and winter periods;

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lighting, heating and cooling of dwellings and greenhouses;

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lighting, heating and cooling of stores, barber stores, butcher stores, workshops, offices and other public service facilities;

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provision of electric power to equipment for fodder preparation for cattle of livestock farms;

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supply of drinking water for livestock and poultry;

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can be used for other purposes.

In addition, work is underway to develop a device to remove dust from the surface of dusty solar panels.

3.2. Mobile Photovoltaic Power Unit with Capacity-N = 1100 W (MPPU-2-550-1100)

Dekhkan and farms play an important role in providing the population of the Republic of Uzbekistan with food [44]. These farms provide themselves and the population with food products produced by them, as well as produce for export.

Today in our country more than 9.8 million families are engaged in agriculture on 1,043,700 hectares (belonging to landowners on 692,200 hectares—homestead and 351,500 hectares—dacha plots, as well as in 31,300 greenhouse farms located on 7175 hectares) of land. In the country, homestead landowners account for 84% of potatoes grown in the country, 71% of vegetable production, 55–60% of apples, grapes, and fruits, and more than 94% of livestock production. These indicators show that the food needs of the country’s population are met mainly by products grown in private subsidiary farms. In addition, due to the lack of water and electricity, 784.7 thousand irrigated lands with complex soils (sandy, fine sandy, and small stone) in the mountainous and foothill areas of our country, located far from the main power lines and water resources, are abandoned. These lands can also be supplied with water by solar-powered pumping units, which will increase crop yields. By supplying these lands with groundwater, with the help of well pumping units powered by solar energy, it is possible to obtain high yields of crops, which constitute foodstuffs.

At present, the introduction of various types of water-saving technologies, especially drip irrigation systems on large crop areas (ω = 1.0 ÷ 100.0 hectares and more), has accelerated in our country [17,18,20]. However, no proper attention is paid to the installation of drip irrigation systems on small (ω = 0.01 ÷ 1.0 hectares) homestead and dacha plots, as well as in greenhouses. In addition, the drip irrigation regime for crops in different hydromodule zones, both on large areas of land and on homestead and dacha plots of citizens, as well as in greenhouses, i.e., how many times during the growing season it is necessary to water the crop and how much water it consumes for one irrigation, is not studied.

To date, cultivation on homestead and dacha plots, as well as within greenhouse settings, has predominantly relied on furrow irrigation. In furrow irrigation, a large amount of water and mineral fertilizers are wasted. With drip irrigation, water and mineral fertilizers go directly to the roots of plants, which eliminates the waste of water and mineral fertilizers. Irrigation of crops on homestead and dacha plots and in greenhouses, using water-saving technologies and renewable sources of (solar) energy, allows you to achieve high yields even in low-water years.

For drip irrigation of small areas (ω = 0.01 ÷ 1.0 hectares), the scientific team “Suvchi” developed the mobile low-pressure drip irrigation unit with photovoltaic panels (Figure 4) [45]. The unit consists of the following main units.

3.2.1. Low Pressure Drip Irrigation System

The proposed low-pressure belt labyrinth drip irrigation system was developed at the National Research University “Tashkent Institute of Irrigation and Agricultural Mechanization Engineers” (NRU “TIIAME”) [46]. The main working part of the low-pressure drip irrigation system is a polyethylene pipe with a dripper. The spacing between drip slots within the oval tube is configurable. The standard configuration for the developed system offers drip slot spacings of 20, 40, and 50 cm. However, alternative spacing arrangements can be accommodated upon request. The drip irrigation pipe, made of non-elastic plastic, consists of a main pipe and a small-sized tube made as a single unit. If the diameter of the polyethylene pipe with drip irrigation is 25 mm, the height of the oval tube taking water from the main pipe is 3 ÷ 5 mm high and the width is 6 ÷ 8 mm. The oval tube takes water from the main pipe through a slit opened every 20 cm. The received water passes through resistances in the tube and carries a drop to the base of the plant through the slit-droppers opened every 20 cm (Figure 5).

One of the main elements of the system is the hydraulic resistance elements in the oval tube. The resistance elements are located along the length of the oval tube walls, on opposite sides, alternately and at equal distances from each other. These hydraulic resistances ensure the same number of droplets at the beginning and at the end, regardless of the length of the irrigation tube. For example, if 1 L of water falls out of the drip slit at the end of the elastic pipe with a length of 500 m in 1 h, the same amount of water is transferred from the drip slit at the end of the irrigation pipe [47].

The principal rivers of Uzbekistan—the Amu Darya and the Syr Darya—as well as their associated irrigation canals, transport substantial loads of suspended sediment within their water flows [48]. These solid particles, in addition to abrasive corrosion of drip irrigation system drippers, also clog the drippers, making them unusable. To prevent the drip lines from failing, coarse sediment particles are trapped in settling tanks and coarse filters, and very fine particles are trapped in fine filters. However, colloidal particles in the water can also pass through fine filters. In addition, any standing or flowing water contains a large number of microorganisms. Mucus, formed by a mixture of colloidal particles and microorganisms in the water, clogs the droppers. If after the termination of irrigation the droppers are not cleaned from the accumulated mucus with a specially prepared mixture, the droppers will completely fail and become unsuitable for further use [49,50,51]. In water with high salinity (up to 3 g/L), used for irrigation in periods of water shortage, this process is greatly accelerated, and as a result, the drip irrigation system very quickly fails.

Drip irrigation pipes made of flexible polyethylene material with a thickness of 100 µm are very light, do not take up much space, and are very easy to transport over long distances. The length of the rolls, which are 6.0 cm wide, can range from several hundred meters to several kilometers. Figure 6 shows the rolls of different sizes,

Table 1. Dimensions of polyethylene pipe coils.

№	Rolls:
	Diameter, cm.	Length, m	Whole, kg
1	23	243	2.4
2	35	622	6.2
3	48	1220	12.2

shows the dimensions of the rolls, and

Table 2. Technical characteristics of flexible polyethylene pipe with drip tip.

№	Characteristics	Unit of Measurement	Quantity
1	Diameter	mm	25
2	Drip type	labyrinthine slot
3	Water flow rate per drip (depending on pressure)	L/s	1–4
4	Distance between drips	cm	20, various
5	Droplet irregularity: - at 500 m;            - at 1000 m.	% %	10 15
6	Water pressure required for system operation	m	1.6–2.0
7	Minimum furrow length	m	250.0
8	Optimum field slope		0.003–0.006
9	Operating period	year	1–2
10	Operating period of main plastic pipes	year	12–15

shows the technical characteristics of flexible polyethylene pipe with drip. For the low pressure drip irrigation system, a 2.0 m³ water tank and a 0.5 m³ liquid fertilizer tank are installed [52]. The drip irrigation system developed by NRU “TIIAME” has the following advantages [53]:

• Not only colloidal particles and microorganisms contained in irrigation water, but also sand with a diameter of 0.5 mm, as well as suspended sediment moving in the water, can freely pass through the drip lines.
• Operation at a low head of 1.6 ÷ 2.0 m (without installation of a pump creating a head of 20 ÷ 30 m).
• Low cost, simplicity of construction, possibility of installation and operation, repair and dismantling by any water user.
• Production of raw materials and equipment necessary for the system in Uzbekistan.

When conducting field studies in 2009 in the Surkhandarya region, the following disadvantages of low-pressure polyethylene pipe with drip line were found [54].

• When reaching the water column head of 2.5–3.0 m or stuck low-pressure polyethylene pipe in weeds, there were cases of its cracking.
• In low-pressure drip irrigation system, the number of droplets remains constant over time. In this case, the critical stage of crop growth, i.e., the time of full maturation and ripening of grains, is not reached, resulting in yield losses.
• When water supply was stopped (due to a malfunction), the water in the pipe heated up to 75–80 °C, which led to deformation of the polyethylene pipe with drippers (stretching in width and length, expansion of the joints of drippers) and even melting of the polyethylene pipe.

To eliminate these disadvantages, the Institute of “Chemistry and Physics of Polymers” of the Academy of Sciences of the Republic of Uzbekistan has developed a new polymer material. Polyethylene pipe made of this polymer material does not deform even at a temperature of 170 °C, is resistant to impacts from a height of 5 m, and is able to provide plants with sufficient water during their growing season.

Determination of drip water flow rate.

Water flow rate of drip tubes in low-pressure polyethylene pipes was determined on the basis of field and laboratory experiments [21]. In field and laboratory conditions, 10 drip lines were selected by the length of the drip tube. Under them, containers for droplet reception were installed. The time of droplet reception was equal to 1 h. Water flow rate per unit of time relative to the received volume was determined by the following Formula:

Q = W/t, L/h.

(1)

In Formula (1): W—volume of water received per unit of time (liter or m³); t—unit of time (hour).

Since the water flow depends mainly on the head of the water column, the head was gradually increased from 10 cm. The drippers did not work until the pressure reached 50 cm; only when it reached 50 cm; droplets start falling from the drippers. The volume of water falling from the 10 drippers at each head was measured, and the average value was calculated. The experiments showed that the intensity of the droplets increased with increasing head. When the pressure reached 1.8 m, the dropper did not produce droplets, but small continuous streams. Thus, the following limit has been established for drippers in low-pressure polyethylene pipe:

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droplet limit −0.5 m;

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the limit of transition from a drop to a water jet −1.8 m.

According to the results obtained, a graph of the dependence of the flow rate of water droplets from the head of the water column was plotted (Figure 7). The obtained graph is expressed by the following Equation (2):

H = f (Q) = 1.02 Q^0.61, L/h.

(2)

3.2.2. Photoelectric Solar Panels

The photovoltaic system of mobile installation of low-pressure drip irrigation, consists of the following: 2 solar panels with capacity-N = 0.55 kW each (with total capacity-N = 1.10 kW); accumulator for 100 A; inverter with built-in controller; position controller of photovoltaic panels and connecting wires (

Table 3. Physical and technical characteristics of 1100 W PhEB parts.

Maximum power of PhEB, Pmax	550 W	2 PhEB 1100 W
PhEB efficiency, η	20.88%	20.88%
PhEB no-load voltage, Uoc	53.90 V	53.90 V
Operating voltage	45.3 V	45.3 V
PhEB short-circuit current, Isc	12.6 A	25.2 A
Current at load	11.04 A	22.08 A
Fill factor, ff	0.71–0.73	0.71–0.73
Cellular polycarbonate thermal collector capacity, V	17 L	17 × 2 = 34 L
Cellular polycarbonate thermal conductivity, r	0.2–3.9 W/m·°C	0.2–3.9 W/m·°C
GEL 100 A hour batteries (4 pcs).		400 Ah, 48 V
Controller with optimum load point tracking		1100 W, 48 V, 30 A
Inverter with pure sine waveform		1100 W, 48 V, 30A

).

The mobile low-pressure drip irrigation unit with a photovoltaic device, can draw irrigation water from mine and tube wells, rivers and canals, lakes, springs, streams, and even rainwater ponds. Scientific innovations obtained during the development of the plant include the following:

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introduction of drip irrigation on small areas (ω = 0.01–1.0 hectare)—farm, homestead, and dacha plots, as well as in greenhouse farms;

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the possibility of using renewable energy sources (solar);

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cooling of solar panels in hot periods of the year (at t = 40–50 °C);

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low cost of the system, simplicity of construction;

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during the non-vegetation period (autumn–winter), the energy produced by the PV system can be used for other purposes (for supplying electrical equipment of small production enterprises of farms; for lighting, heating, and cooling of residential houses, stores, hairdressing salons, butcher stores, workshops, offices, and other consumer service facilities; for preparing fodder for livestock and poultry farms and supplying drinking water for livestock and poultry farms, etc.);

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manufacturing of all parts from local raw materials;

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utilization of solar energy for the operation of the water pumping device;

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use of compact tanks for water and fertilizer intake instead of a water intake basin;

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no need for qualified specialists for operation;

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ease of installation and operation, repair and dismantling, storage;

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possibility to develop an irrigation regime for rice crops (melon crops) on small areas.

3.2.3. Pumping Installation

The pumping unit, using the energy generated by the photovoltaic system, pumps water into a tank with a volume of W = 2.0 m³, located at a height of H = 1.8 m. For this purpose, a pump brand, EVN-130-4, of the Chinese company EPA, founded in 2009 (Figure 8) [55], was selected. The main characteristics of the pump EVN-130-4 are presented in

Table 4. EVN-130-4 pump indicators.

1	Mains voltage, V	220
2	Power consumption, W	370
3	Insulation class	23
4	Warranty, month	12
5	Diameter of outlet opening, mm	25
6	Flow rate, l/min	90
7	Rotation speed, rev/m	2850
8	Frequency, Hz	50

.

3.2.4. Four-Wheeled Cart with Metal Structure

Low-pressure drip irrigation system, including tanks for water (W = 2.0 m³) and mineral fertilizer (W = 0.05 m³), as well as main pipes and flexible polyethylene pipes with drippers, photovoltaic panels, solar system, a battery, and an inverter with a built-in controller; a position controller of photovoltaic panels and connecting wires; and a pumping device for water supply to the drip irrigation system and its suction and pressure pipelines, are mounted on a four-wheeled mobile cart consisting of metal structures (Figure 6).

3.2.5. Automated Control System

The automated control system, provides automatic operation of the pumping device depending on the water level in the water intake and water tank. In addition, given that the irrigation of crops is carried out mainly at night, the developed program allows the owner of the irrigated field to remotely start, control, and stop the drip irrigation system. This, in turn, creates convenience for farmers living away from homestead and dacha plots, as well as greenhouse farms.

3.2.6. Field Studies to Determine the Drip Irrigation Regime with the Installation of MSUE-2-550-1100

Field studies to determine the drip irrigation regime for vegetable crops (cucumbers) using the MSUE-2-550-1100 system were conducted in 2024 (23 April–14 August) and 2025 (9 April–10 July) in fields (in open ground) [56] of Komolov Muzaffar LLC in the Upper Chirchik district of the Tashkent region of the Republic of Uzbekistan. The growing season in this area is 200 days, which allows for two to three harvests of cucumbers. The water source is a vertical well with a vertical pumping unit, ECV8-100-63.

A plot with an area of ω = 0.1 hectares was selected for field studies (in 2024 in contour K-5/3 and in 2025 in contour K-5/1). Information about the experimental field is given in

Table 5. Information about the experimental field, cucumbers, hydromodular area, irrigation norms for furrow, and drip irrigation, as well as water savings with drip irrigation.

Field Research Location	Information About the Experimental Field:						Cucumber Information:											Hydromodular Region: IV-b						Water Savings Compared to Furrow Irrigation, %
	Area, ha	Contour Number	Number of Furrows, pcs	Total Length of Furrows, m	Soil Type	Groundwater Depth, m	Variety	Planting Scheme	Planting Day	Germination Day	Water Supply Day	Distance Between Seedlings, m	Number of Seedlings, pcs.	Number of Fruits Per Seedling, pcs.	Total Number of Fruits, pcs.	Average Weight of 1 Fetus, g.	Yield, kg/ton	Irrigation:
																		Furrow			Drip
																		Irrigation Period	Irrigation Rate, M3/ha	Number of Waterings, times	Irrigation Period	Irrigation Rate, M3/ha	Number of Waterings, times
2024, growing season from 23 April to 20 July (89 days)
M. Komolov LLC in the Upper Chirchik District of the Tashkent Region of the Republic of Uzbekistan	0.1	K-5/3	22	1100	Heavy clay	15.0–18.0	Asterix F1	0.9 × 0.30	23.04	29.04	02.05	0.30 × 0.30	3367	13	47,671	115	5482/54.80	26.04–31.06	3600	12	23.04–20.07	2200	34	38.9
2025, growing season from 11 April to 13 July (95 days)
M. Komolov LLC in the Upper Chirchik District of the Tashkent Region of the Republic of Uzbekistan	0.1	K-5/1	22	1100	Heavy clay	13.0–16.0	AMyp F1 Amur F1	0.90 × 0.30	11.04	16.04	18.04	0.30 × 0.30	3367	12	44,000	126	5545/55.50	26.04–31.06	3600	12	11.04–13.07	2420	38	32.8

. Cucumber seeds were planted as follows: on 23 April 2024, at an average air temperature of 21 °C (seeds of the Dutch variety “Asterix F1”) and on 11 April 2025, at an average air temperature of 25 °C (seeds of the Dutch variety “Amur F1”). Seed germination was observed on 29 April 2024 (after 7 days) and on 16 April 2025 (after 6 days). Leaf formation was observed in 2024, after 7 days (6 May) and in 2025, after 6 days (21 April).

The first watering was carried out in 2024, two days (1 May) after sprouting and in 2025, also two days (18 April) after sprouting. There were 34 waterings in 2024 and 38 waterings in 2024. Water consumption per seedling at the beginning and end of the growing season was 1 L, and during the rest of the growing season, 2 L. Depending on the air temperature, water for irrigation was supplied every 3–4 days at the beginning of the growing season, and every 2 days during flowering and fruiting. The flow rate of low-pressure system drippers, depending on the pressure, is as follows: at a pressure of 0.6–1.0 m, 0.5–1.0 L/h; at a pressure of 1.0–1.5 m, 1.0–1.8 l/h; and at a pressure of 1.5–2.0 m, 1.8–2.5 l/h [57]. Information about the experimental field, cucumbers, the hydromodular area, irrigation norms for furrow and drip irrigation, as well as water savings with drip irrigation, is given in Table 5. The results of comparisons of vegetation water consumption for furrow [9] and drip irrigation in 2024 and 2025 show that water savings amounted to 38.9% and 32.8%, respectively (Figure 9a,b).

3.3. Mobile Photovoltaic Power Unit with Capacity—N = 2000 W (MPPU-4-500-2000)

Irrigation pumping stations annually for their own needs consume about 1–3% of the total amount of electricity consumed, which is mainly spent on auxiliary systems (drainage system, lighting system, etc.) [58,59,60,61]. Sometimes an accident in the power system or other unforeseen circumstances leaves a pumping station without electricity for some time (in rare cases for several days), which can lead to flooding of the underground part of pumping stations with filtration water without its pumping [62,63,64,65]. To solve this problem, a mobile photovoltaic installation for medium and small pumping stations was proposed (Figure 10).

The power of the developed unit is 2000 W (4 panels of 500 W each); it has four helium batteries of 200 A∙h (total capacity of 800 A∙h), an inverter for 3 kW, a two-phase electric meter, air cooling system in summer, and two output sockets (Figure 9).

The mobile platform of the unit is a cart of its own design; it gives the possibility of free movement on the territory of the pumping station to supply the generated electricity directly to the consuming equipment. Also, the mobile platform gives the possibility to increase electricity generation during the day by directing the solar panels perpendicular to the sun by the pumping station personnel. In addition, the solar panels have the ability to adjust the angle of inclination relative to the sun from 0 to 45 °C.

The developed installations have been implemented at 29 irrigation pumping stations in seven regions of Uzbekistan, such as the following: “Obi-Khayot”, “Ulugnar”, “Gulbahor-1p”, “Asaka-Adir”, “Raish-Hakent-1”, “Raish-Hakent-2” and “Gulistan” in Andijan province; “Alat”, “Paykent”, “Jondor-3”, “Yomonjar”, ‘Soktari’ and “Karakul” in Bukhara province; “Kanimeh-1”, “Navai” and “Urtachul” in Navaiya Province; “Namangan”, “Bulakbashi” and “Rezaksay-3” in Namangan province, “Amu-Zang-1”, “Amu-Zang-2”, “Babatag”, “Sherabad” and “Jaykhun” in Surkhandarya province; “DGNS”, “DNS-2”, and “DNS-3” in Jizzakh province; as well as “Dangara” and “Furkat-1” in Fergana province.

To drain the drainage system together with the photovoltaic installation, one submersible centrifugal pump with a head of 8–12 m, a flow rate of 20–30 m³/h, and a power of 750 W was installed at each pumping station. The pumps have an automatic float on-off system, which enables automatic operation of pumps in the drainage well of the pumping station depending on the water level in it (Figure 11). During the daytime, part of the electricity generated by the mobile photovoltaic system is consumed for the pumping unit, and the rest is stored in batteries. The capacity of the batteries is sufficient for continuous operation of the pumping unit for 12 h.

To drain the drainage system together with the photovoltaic installation, one submersible centrifugal pump of thte EVN-P30-6-750-3 brand manufactured by EPA was installed at each pumping station. The main technical characteristics of the pump are summarized in

Table 6. Main technical characteristics of pump EVN-P30-6-750-3.

1	Mains voltage, V	220
2	Power consumption, W	750
3	Nominal pressure head, m	6
4	Maximum pressure head, m	10
5	Speed of rotation, r/min	3000
6	Nominal flow capacity, m3/h	30
7	Diameter of outlet opening, mm	75
8	Frequency, Hz	50

.

The use of a low-power submersible pumping unit (750 W) for drainage water allows for a reduction—and in some pumping stations, complete elimination—of the need to operate higher-capacity drainage pumps installed in the station building as specified by the project design.

During 2023–2024, systematic monitoring of both electricity production by the mobile installation and its subsequent consumption was conducted at each selected pumping station across both the growing and non-growing seasons. Daytime measurements—recorded via an electric energy meter attached to the mobile unit—captured the energy usage of the submersible pump and station lighting. Each pumping station underwent 4 discrete measurement campaigns during both seasonal periods. Observations of mobile photovoltaic systems installed at pumping stations during the growing season revealed that 75–80% of the generated electricity was consumed by submersible pumps, as increased pumping led to higher volumes of gland filtration water. The remaining 20–25% of the electricity was utilized for lighting the pump station building at night. In winter, when the main pump units are shut down and filtration in the engine room is minimized, 72–77% of the generated electricity is allocated to building lighting and the personal needs of operating personnel. Furthermore, the use of the installation MPPU-4-500-2000 at pumping stations helps prevent flooding of the underground section of the station building in the event of an emergency power outage.

3.4. Cooling System for Photovoltaic Solar Panels

In the countries of Central Asia, including the Republic of Uzbekistan, every year in the June and July months, a strong increase in air temperature is expected. For example, in the daytime hours of 6–8 July 2025 in Uzbekistan, the air warmed up to 41–45 °C, and in the north, south, and desert zones of the country—up to 44–50 °C [66]. The use of photovoltaic batteries (PV) of traditional design in the summer period of the year in the hot, dry climate of the country to generate electricity is not effective, as there is a significant reduction in capacity under the influence of temperature and pollution of atmospheric air of up to 50% and more [66].

In order for the solar panels to work with high efficiency, their temperature should not exceed t = 25–27 °C. In order for the solar panels of MPPU-2-550-1100 and MPPU-8-500-4000 installations to work with high efficiency in hot periods of the day (t = 40–50 °C), a water cooling system is installed on their back side (Figure 12). Compared to conventional uncooled solar panels, the capacity of cooled panels can increase by 1.5–2.0 times [67]. In addition, work is underway to develop a device to remove dust from the surface of dusty solar panels.

3.5. Clean Energy Production

The developed mobile low-pressure drip irrigation unit has such advantages as low cost, simple construction, all parts are made of local raw materials, use of renewable-solar energy, no need for qualified specialists for operation, easy repair work. Electricity generated by solar panels in the mobile drip irrigation unit is clean energy that does not pollute the environment. Its utilization results in environmental cleanup and fossil fuel savings. Below we will consider how much gas and conditional fuel can be saved due to the energy produced by the units MPPU-2-550-1100, MPPU-4-500-2000, and MPPU-8-500-4000 (Table 6). The calculations take into account the combustion of 0.15 m³ of gas fuel and the saving of 0.122835 conventional fuel for the production of 1 kWh of electricity. The Government of the Republic of Uzbekistan, along with exempting the population from paying property and land taxes, also guarantees payment of 1000 soum*kWh for each 1.0 kW of electricity produced when installing renewable energy sources and generating electricity [68,69].

According to the data in

Table 7. Amount of saved gas, fuel equivalent and economic effect from electricity generation by mobile photovoltaic units MPPU-2-550-1100, MPPU-4-500-2000, and MPPU-8-500-4000.

Operating Period of Solar Panels-330 Solar Days	Electricity Generated, kWh	Energy Savings:		Economic Benefit, kWh∙Sum (USD) *
		Gas, m3	Conventional Fuel
Mobile Photovoltaic Power Unit with capacity-N = 1100 W (MPPU-2-550-1100)
In 1 h	1.1	0.165	0.13512	1100 (0.0867)
In 1 day	26.4	3.96	3243	26,400 (2.08)
In 1 year	7920	1188	973.0	7,920,000 (624.10)
Mobile Photovoltaic Power Unit with capacity-N = 2000 W (MPPU-4-500-2000)
In 1 h	2.0	0.30	0.2457	2000 (0.1576)
In 1 day	48.0	7.20	11.80	48,000 (3.79)
In 1 year	15,840.0	2376	1946.0	15,840,000 (1220.0)
Mobile Photovoltaic Power Unit with capacity-N = 4000 W (MPPU-8-500-4000)
In 1 h	4.0	0.60	0.49134	4000 (0.3152)
In 1 day	96.0	14.40	47.169	96,000 (7.565)
In 1 year	31,680.0	4752.0	3892.0	31,680,000 (2496.40)

Notes: * 1.0 kWh of electricity is sold for 1000 soums (US$ 0.0788). US$. 1.0 USD. USD (as of 1 July 2025) = 12,690.0 soums.

, for 1 year the installation of MPPU-2-550-1100-E generates 7920 kWh of electricity, saves 1188 m³ of gas and 973 conventional fuel due to the generated electricity, as well as brings a profit of 7,920,000 soums (624.10 USD) for the generated electricity; MPPU-4-500-2000 generates 15,840 kWh of electricity, saves 2376 m³ of gas and 1946 conventional fuel due to the generated electricity. MPPU-4-500-2000 generates 15,840 kWh of electricity saves 2376 m³ of gas and 1946 of fuel equivalent for the electricity generated, and generates a profit of 15,840,000 soums (1220.0 USD) for the electricity generated. MPPU-8-500-4000 generates 31,680 kWh of electricity, saves 4752 m³ of gas and 3892 of conditional fuel at the expense of the generated electricity, and generates a profit of 31,680,000 soums (2496.4 USD) for the generated electricity. Due to the high demand for this unit, millions of units are planned to be produced in the coming time.

4. Conclusions

Based on the research and experimental design work carried out, three mobile photovoltaic units—MPPU-8-500-4000, MPPU-2-550-1100, and MPPU-4-500-2000—were developed and implemented to address water and energy shortages. The main conclusions are as follows:

1.

Mobile Photovoltaic Power Unit MPPU-8-500-4000 is designed for water supply to agricultural farms and cluster fields with an area of ω = 10.0 ha or more. This unit has the following advantages:

-

its mobility enables year-round use for supplying drip irrigation systems of one or several farms during the growing season, as well as for powering electrical equipment at small production facilities of farms in the autumn–winter period;

-

the ability to adjust the orientation of solar panels in accordance with the daily trajectory of the sun increases electricity generation efficiency by 1.5–2 times;

-

to prevent efficiency losses of the photovoltaic system during hot summer conditions, the panels are equipped with a water-cooling system that maintains their operating temperature in the range of 25–27 °C.

2.

Mobile Photovoltaic Power Unit MPPU-2-550-1100 is designed for water supply to households and garden plots, greenhouses, as well as dehkan farms with an area of ω = 0.01–1.0 ha. This unit offers the following advantages:

-

its mobility enables year-round use for drip irrigation of several small plots belonging to one or more farms during the growing season, as well as for lighting and supplying small-capacity electrical appliances in private households in the autumn–winter period;

-

the system is equipped with water cooling to maintain the operating temperature of photovoltaic panels within 25–27 °C during summer;

-

the capability to adjust the orientation of the solar panels in line with the sun’s daily trajectory increases electricity generation efficiency by 1.5–2 times.

3.

Mobile Photovoltaic Power Unit MPPU-4-500-2000 is designed for supplying energy to auxiliary needs (drainage systems and lighting) of small and medium-sized irrigation pumping stations. This unit provides the following benefits:

-

the application of the MPPU-4-500-2000 at pumping stations prevents flooding of the underground part of the station building in the event of an emergency power outage;

-

the use of a low-power submersible pumping unit (750 W) for drainage water reduces, and in some stations even eliminates, the need to operate more powerful drainage pumps installed in the station building according to the design.

4.

Mobile photovoltaic power units MPPU-8-500-4000, MPPU-2-550-1100, and MPPU-4-500-2000 can also be applied for water and energy supply in other sectors of the economy.

5.

Observations of mobile photovoltaic systems installed at pumping stations during the growing season revealed that 75–80% of the generated electricity was consumed by submersible pumps, as increased pumping led to higher volumes of gland filtration water. The remaining 20–25% of the electricity was utilized for lighting the pump station building at night. In winter, when the main pump units are shut down and filtration in the engine room is minimized, 72–77% of the generated electricity is allocated to building lighting and the personal needs of operating personnel.

6.

The deployment of mobile, low-pressure drip irrigation systems integrated with photovoltaic panels on household and garden plots, greenhouses, as well as dehkan farms (ω = 0.01–1.0 ha), represents a sustainable adaptation measure to climate change. Such systems can enhance the reliability of water supply for agricultural crops in Uzbekistan, across Central Asia, and in other arid regions, thereby strengthening food security and supporting the resilience of rural communities.