Application prospects of photovoltaic water pumps in rural arid areas

Photovoltaic water pump system is a typical "light energy, machine, electricity integration" system from a technical point of view. It involves the latest technologies of solar energy collection, conversion and power electronics, motors, water machines, computer control and other disciplines, and has great significance for energy conservation. Therefore, it has been listed as a high-tech and a direction for further development by many countries. Many countries in the Middle East and Africa hope to transform their homes into oases in arid areas with abundant groundwater resources by relying on solar water pumps, water-saving micro-irrigation, modern agriculture and other new technologies.

The basic working principle of the photovoltaic water pump system is: using solar cells to directly convert solar energy into electrical energy, and then driving the photovoltaic water pump through the controller to drive the motor. Photovoltaic water pump system can be widely used for water use for people and livestock in areas without electricity, agricultural irrigation, and water use at highly dispersed points such as border defense and island outposts. Because photovoltaic water pumps have the advantages of no noise, full automation (start at sunrise and stop at sunset), high reliability, good adaptability of water supply and evaporation ("when it is very dry, it will dry up"), etc. International organizations such as the United Nations International Development Agency (UNDP), the World Bank (WB), and the Economic and Social Commission for Asia and the Pacific (ESCAP) have fully affirmed its advancement and rationality. At present, with the support of these international organizations, there are tens of thousands of photovoltaic water pumps of different specifications operating in different regions and countries around the world, especially in developing countries such as Asia, Africa, Latin America and the Middle East, which have brought considerable economic benefits to the people in many poor areas and accelerated the pace of poverty alleviation in these areas.

As the main component of the photovoltaic water pump system, the solar photovoltaic power generation device has received considerable attention in the past few decades because of its noise-free, pollution-free, and no waste. At present, photovoltaic power generation in the world is developing rapidly. From the perspective of energy supply security and clean utilization, many countries in the world regard the commercial development and utilization of solar energy as an important development direction. The European Union, Japan and the United States focus on renewable energy, especially solar energy, for energy supply security after 2030. It is expected that solar power generation will account for more than 10% of the world's electricity supply by 2030 and more than 20% by 2050. At the end of 2006, Japan had installed a total of 1,600MW, and the country's photovoltaic module production accounted for 50% of the world. Four of the world's top 10 manufacturers are in Japan. Today, photovoltaic power generation has been connected to the grid in Japan, Germany, the United States, and Italy. Thousands of office buildings, laboratories, residents, and mechanical equipment are enjoying stable, reliable, pollution-free, noise-free, and waste-free solar power.

my country began to study solar cells in 1958, and successfully applied them to the Dongfanghong 2 satellite launched by my country for the first time in 1971. After 1973, they were used on the ground, such as navigation lights and railway signals, and instrument signals of high-mountain meteorological stations, with relatively low power. With the country's strong support for the development of the photovoltaic industry and the photovoltaic market, my country's solar cells are no longer only used in low-power power systems, but are more widely used in various industries to solve the increasingly serious energy crisis. my country's production of solar cells is far greater than its use. Various forms of water pumps are energy-consuming products. The electricity consumed by pump products in the world accounts for about 20% of the total power generation. In order to save energy, vigorously promoting photovoltaic water pump systems is a development need.

The solar photovoltaic water pump system is a device that uses a water pump to pump water, powered by solar energy. The photovoltaic water pump system is a typical "light-electricity-machine-control" integrated system, involving multiple fields such as solar energy conversion, signal acquisition, power electronics conversion, circuit design and system control. The battery is responsible for collecting solar energy and converting it into DC power input into the system to provide power for the system; the voltage and current output by the battery array are often not well matched with the load. At this time, it is necessary to go through the DC conversion link, and go through boost (such as Boost circuit) or buck (such as Buck circuit) to obtain the required voltage and current; in order to enable the load to continue to work on rainy days or at night, it is necessary to add a battery to the system to store excess energy during the day or summer and release it at night or in winter to balance energy distribution or achieve no light operation; the photovoltaic water pump system is greatly affected by external conditions, and the operation of the system is in continuous change, which is difficult to maintain in a stable state. Certain control measures need to be taken to ensure the efficient and stable operation of the system, such as: tracking the maximum power point of the battery array, preventing overcharging and over-discharging of the battery, monitoring the operation status of the entire system, and implementing certain electrical protection and fault alarms. If there is an AC load, an inverter is also required to achieve DC-AC conversion.

The climate in central and western my country (Xinjiang, Qinghai, Gansu and Inner Mongolia, etc.) is dry, with perennial drought and little rain, and water resources are extremely scarce, resulting in land desertification at a rate of 2500km2 per year and a worsening ecological environment. Due to the low irrigation and drainage guarantee rate, 2/5 of the cultivated land cannot be irrigated. In some severely drought-stricken areas, even drinking water is not solved, which seriously hinders the economic and social development of the region. However, some areas in these areas are rich in groundwater. If the groundwater resources in these arid areas can be reasonably utilized, it will surely bring huge economic and social benefits to those areas. In addition, these areas are far away from the ocean, with less cloud cover, more sunny days, strong solar radiation (some areas have an annual solar radiation of 5000~6000MJ/m2), and long sunshine time (annual sunshine time reaches 2500~3500h), so photovoltaic power generation and water extraction naturally become the best choice to solve the power supply and water supply problems in these areas. In recent years, the continuous price reduction of photovoltaic devices and the continuous improvement of the efficiency of solar cells have provided very favorable conditions for the promotion of photovoltaic water pump systems. The investment of photovoltaic water pumps can greatly improve the production capacity of agriculture and animal husbandry, increase agricultural and animal husbandry output, and change the agricultural status quo in arid areas. Water conservancy is the lifeblood of agriculture. With water, agriculture can be developed and farmers' lives can be improved. Therefore, in the long run, the economic and social benefits are very obvious.