Solar Power Meets Water Supply: The Intricate Workings of Solar Water Pumps

Solar water pump (also known as photovoltaic water pump), is today the world's sun-rich areas, especially the lack of electricity without electricity in the remote areas of the most attractive way of water supply, the use of everywhere available, the inexhaustible solar energy, the system fully automatic sunrise, sunset and rest, no personnel care, maintenance workload can be reduced to a minimum. It is an ideal green energy system that integrates economy, reliability and environmental benefits.

System composition

Photovoltaic array

It is mainly to convert the light energy of the sun into electrical energy to provide working power for the load pump motor.

Photovoltaic water inverter or controller

The operation of the solar water pump is controlled and adjusted, the electric energy emitted by the solar array is used to drive the water pump, and the output frequency is adjusted in real time according to the change of sunshine intensity, so that the output power is close to the maximum power of the solar battery array.

Motor (drive motor)

The drive motors used in different systems are also different. In the large-scale photovoltaic pump system, there is still no lack of AC asynchronous transmission mode, but due to the continuous development of modern control technology, in order to further improve the amount of lift provided by the unit peak watt, it has begun to be replaced by the multi-machine group control technology of flexible control by multiple pumps.

Water pump

For photovoltaic pump systems, the choice of pump type is also important. In a system with low power, if the user requires a high head but a small flow, it is appropriate to choose a positive displacement pump, and in other cases it may be possible to use centrifugal or axial flow pumps. The selection and consideration of pump type for photovoltaic pump system.

DC permanent magnet brushless motor drives the pump

DC motor has been widely used in motion control system because of its good mechanical characteristics, wide speed range, large starting torque, high operating efficiency, simple control, etc., but its brush and commutator also bring low reliability, need frequent maintenance and other weaknesses. In the past 20 years, with the rapid development of high-power switching devices, analog and digital integrated circuits, computer technology, and high-performance magnetic materials, brushless DC motors using electronic commutation principle have also been rapidly developed. It has been rapidly expanded from the initial application of aerospace and military facilities to industrial and civilian fields, and its use is increasingly widespread. Small power brushless DC motor has been widely used in computer peripherals, office automation and audio and video equipment, and in some electric transmission systems, its application is more and more extensive.

For several years brushless DC motor began to be used as a drive motor in photovoltaic pump system, this is because the motor has a high efficiency that is not easy to achieve by general AC motor, it is expected to greatly reduce the amount of relatively expensive solar cells, with significant economy. However, since the photovoltaic pump usually requires the motor to dive into the water to run, so the research work in this paper in addition to the need to solve the conventional DC brushless motor operation drive technology, but also requires the motor to adapt to the requirements of diving, that is, must also solve the reliable insulation problem of the winding. From the mechanical seal point of view to find ways to solve the sealing problem of submersible motor is a way of thinking, but it is difficult to overcome its complex structure, the corresponding mechanical loss of large problems.

working principle

Brushless DC solar water pump (motor)

The motor brushless DC pump is composed of a brushless DC motor and an impeller. The shaft of the motor is connected with the impeller. There is a gap between the stator and the rotor of the pump, and the water will penetrate into the motor for a long time, increasing the possibility of the motor burning out.

own advantage

(1) Reliable: photovoltaic power supplies rarely use moving parts and work reliably.

(2) Safe, no noise, no other public hazards. Does not produce any solid, liquid and gas harmful substances, absolute environmental protection.

(3) Simple installation and maintenance, low operating cost, suitable for unattended and other advantages. Especially for its high reliability and much attention.

(4) Good compatibility, photovoltaic power generation can be used in conjunction with other energy sources, and it can also be convenient to increase the capacity of the photovoltaic system according to needs.

(5) The degree of standardization is high, and the series and parallel components can meet the needs of different electricity consumption, and the versatility is strong.

(6) Solar energy is available everywhere and has a wide range of applications. 

However, the solar system also has its disadvantages, such as: energy dispersion, intermittent, strong regional. The upfront cost is high.

Systems Perspective

The efficiency of silicon solar panels is difficult to improve in a short period of time, although the second generation of thin film solar cells and the third generation of organic solar cells have obvious advantages in cost, but compared with the large-scale production of silicon solar panels is not competitive. For some time to come, silicon panels will still occupy a large share of the market. Therefore, in the future, the direction of research and development of solar water pump systems should focus on the following three aspects:

(1) Develop high-efficiency pumps and motors to improve the high-efficiency range of motors and pumps under a wide range of speed and flow changes and reduce the threshold power of the system. Develop low-cost, high-reliability intelligent controllers to improve the performance match between components and cope with changing weather conditions, thereby improving the dynamic quality and overall efficiency of the system. At the same time, the development and promotion of comprehensive technologies for the complementary utilization of wind, light and heat energy in small and medium scale should be improved.

(2) The general method of long-term performance prediction of solar water pump system under multi-factor changes such as climate, light, water level, and water demand and the system design method based on dynamic changes, the database of different regions is established to gradually replace the method of using static average value estimation;

(3) With the reduction of panel prices and the development of small and medium-sized solar systems, in the future, on the basis of optimizing panel power, the evaluation of system operational reliability should be increased to improve the long-term operational reliability of the system and the stability of water supply.