my country faces a severe water shortage, frequent droughts, and serious soil erosion. Furthermore, the power grid cannot fully cover remote mountainous areas, significantly impacting the lives, drinking water, and agricultural production of people in these regions. In recent years, my country's photovoltaic (PV) industry has developed rapidly, with costs declining year by year. PV products are beginning to enter people's lives. Among them, PV water pumping systems combine PV products with water pumping, innovatively applying them to domestic water supply, agricultural irrigation, ecological restoration, and grassland animal husbandry. As a novel application in the PV field, PV water pumping systems not only avoid the large capital investment required for power grid infrastructure construction but also solve the problems of power and water shortages in agricultural production.
A typical photovoltaic (PV) water pumping system mainly consists of four parts: PV modules, PV support structures, a water pumping inverter, and a water pump. It uses clean solar energy to directly drive the pump, pumping water instead of storing electricity, eliminating the need for energy storage devices and significantly reducing construction and maintenance costs. Due to its environmental friendliness, energy efficiency, ease of installation and maintenance, and cost-effectiveness, the system is widely used.
The design of a photovoltaic (PV) water pumping system begins with a thorough preliminary survey of the customer's needs, including information such as the system's intended use, daily water consumption, pump head, and local sunlight conditions. Only by fully understanding the customer's specific requirements can the optimal solution be provided to maximize their satisfaction. The design of a PV water pumping system mainly includes three parts: pump selection, pumping inverter selection, and PV module design.
1. Water pump selection
1.1 Flow Determination
The flow rate of a water pump, also known as its delivery capacity, is mainly determined based on the customer's water consumption and local sunlight conditions. The following formula can be used as a reference for design:
1.2 Head Determination
Head refers to the height that a water pump can lift water to. It is an important performance parameter of the pump and can be measured according to the actual conditions of the customer's project. The following is the calculation method for head:
Pump head = static head + horizontal conveying distance + head loss
Static head refers to the elevation difference between the pump's suction point and its elevated control point, such as when pumping water from a deep well to a higher water tank. In the case of a clear water tank, static head is the elevation difference between the pump's suction inlet and the higher water tank; as shown in the diagram, static head is H1 + H3.
The horizontal conveying distance is shown in Figure H2. Generally, when calculating the head, every 10m in the horizontal direction is counted as 1m of head.
The head loss is usually 6 to 9% of the net head, such as at pipe bends and water head, which is generally 1 to 2 meters.
Once the flow rate and head of the water pump are determined, the pump model can be basically determined. If the customer is pumping water from a deep well, the size of the water pump should be smaller than the diameter of the deep well.
2. Water pump inverter selection
The photovoltaic (PV) pumped water inverter is the most important piece of equipment in a PV pumped water system. As the controller and regulator of the entire system, it continuously performs maximum power point tracking and adjusts its output frequency in real time according to changes in solar radiation, thereby controlling and regulating the operation of the water pump. The power of the pumped water inverter is mainly determined by the power of the water pump motor. For reliable system operation, it is generally recommended to select an inverter with a power not less than that of the water pump motor, while also considering the water pump's input voltage and wiring method (single-phase or three-phase), to ultimately determine the model of the pumped water inverter.
3. Photovoltaic module design
In remote mountainous areas where there is no power grid or diesel generator as a supplementary power source, the power of the photovoltaic water pumping system is entirely provided by the electricity generated by the photovoltaic modules. In order to ensure that the water demand of customers is met, considering the impact of factors such as the tilt angle of the photovoltaic panels, temperature, shading, and dust on the system, as well as the oversizing capability of the water pumping inverter, it is generally recommended that the power of the photovoltaic modules be between 1.1 and 1.5 times the rated power of the inverter, and generally 1.2 times is sufficient.
Typical design scheme for a 4.5.5kW water pumping system
Project Background:
The project site lacks mains power and a generator. A photovoltaic water pumping system was designed for a client to draw water from a deep well for farmland irrigation. Details are as follows:
a) The well is approximately 60 meters deep, with a head of approximately 50 meters and a diameter of approximately 250 mm;
b) A total of 80 mu of dry land needs irrigation, requiring approximately 70 cubic meters of water per day;
c) Irrigation devices: The local average daily sunshine duration is approximately 4 hours.
4.1 Water Pump Selection
Based on the above information, the required water pump flow rate is 70 m³/(4h*0.85) = 20.6 m³/h, and the head is 50 meters. The Ruirong R150-DS-05 water pump can be selected, with a 4kW motor and a suitable well diameter of 150mm, which meets the requirements. The specific parameters of the water pump are as follows:
4.2 Selection of Pumping Inverter
Based on the water pump motor power of 4kW and the input voltage of three-phase 380Vac, the water pump inverter selected is Jingfuyuan's SPRING5500, with a rated output power of 5.5kW.
4.3 Photovoltaic Module Design
The selected pumped water inverter, SPRING5500, has a rated output of 5500W. Considering the good local lighting conditions, a component with a capacity of 1.1 times can be selected, i.e., 1.1 × 5500 = 6050W.
Founded in 2003, Shenzhen Jingfuyuan Technology Co., Ltd. is a national high-tech enterprise integrating R&D, production, sales, and service. The company has long focused on the power electronics industry, offering photovoltaic water pumping inverters ranging from 0.55-75kW, with single-phase and three-phase AC outputs, supporting various water pump motors, and an IP65 protection rating (for power ratings above 22kW, an outdoor cabinet is added, increasing the protection rating to IP54). Suitable for outdoor use, it can be equipped with a diesel engine or mains power as a backup power source, supporting 24/7 water pumping. Jingfuyuan adheres to the philosophy of "diligence pays off, striving for excellence," and endeavors to create greater value for its customers.
