Typical Solar Pumping System Design
China's per capita water resource shortage, droughts, serious soil erosion, and the power grid can’t fully cover the remote mountainous areas, these problems are seriously affecting people's lives, water usage, and agricultural production. In recent years, China's PV industry has developed rapidly, and the cost has been declining year by year. PV products have begun to step into people's lives. Among them, solar pumping system is the combination of PV products and water pumping, it applies to people’s daily water usage, agricultural irrigation, and ecological restoration etc. occasions. Solar pumping system, as a new application in the field of PV industry, it can not only avoid a large amount of capital investment in power grid infrastructure construction, but also solve the problem of lack of electricity and water in agricultural production.
Typical solar pumping system is mainly composed of four parts, including PV panel, PV bracket, solar pumping inverter and water pump. The system drive the pump to pump water with solar energy directly, it replaces electricity storage with water storage and doesn’t need the extra energy storage devices. It will greatly reduce the system construction costs and operation/maintenance costs. The system is widely used by people because of its environment-friendly, energy saving, easy installation and maintenance, and economical efficiency.
In order to design the solar pumping system, firstly, we need to do a good customer demand survey in the early stage, such as: system use, customer's daily water consumption, lift and local lighting information etc. Only when we fully understand the specific needs of customers, can we provide the best solution to them. The design of solar pumping system is mainly included three parts: pump selection, pumping inverter selection and PV panel design.
Pump selection:
The flow determination
The flow of the pump is also called the water delivery volume. The flow of the system is mainly determined by the customer's water consumption and local lighting conditions. For details, please refer to the following formula:
Lift determination
The lift refers to the height that the pump can pump water. It’s 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 the lift:
Pump lift=Static lift + Horizontal transport distance + Lift loss
The static lift refers to the height difference between the suction point of the pump and the high control point. For example, pumping water from a deep well and sending it to a high water tank. The static lift is the height difference between the suction inlet of the water tank and the high point of the water tank. As showed above, the static lift is H1+H3; Horizontal transport distance as showed in above H2. Generally, when calculates the lift, every 10 m in the horizontal direction is counted as 1 m lift.The lift loss is usually 6 to 9% of the net lift, generally 1~2 m.
After the flow and lift of the pump are determined, the pump model can be basically determined too. If the customer is pumping the water in a deep well, it is also necessary to consider that the size of the pump must be smaller than the diameter of the deep well.
Solar pumping inverter selection
The Solar pumping inverter, as the controller and regulator of the whole system, so it’s the most important part in the system. It always performs maximum power point track and adjusts the output frequency according to the solar radiation, and then controls and regulates the pump work. The power of the solar pumping inverter is mainly determined by the pump motor. For the reliable operation of the system, it is generally recommended to select the power of the inverter not less than the power of the pump motor, at the same time, considering the input voltage and wiring mode of the pump (single-phase or three-phase), and finally determine the model of the solar pumping inverter.
The design of the PV panel
In remote mountainous areas, there is no power grid or diesel generator as a supplementary power source. The power of the solar pumping system is all from the electricity generated by the PV panels. In order to satisfy the customer's water usage demand, we need to consider the influence factors of the system, such as the PV panel tilt angle, local temperature, shadow obscuration, dust and the over-distribution capability of the pumping inverter. Generally we recommend that the power of the PV module is between 1.1 and 1.5 times the rated power of the inverter, generally 1.2 times.
5.5kW typical solar pumping system design
Project background：
Design a solar pumping system for the customer, pumping water from deep wells for farmland irrigation, the specific information is as follows:
a） The depth of the well is about 60 meters, the lift is about 50 meters, and the diameter is about 250mm:
b）Total 80 mu of dry land needs to be irrigated, and water consumption is about 70 square meters per day.；
c）The average local sunshine time is about 4 hours/day.
Pump selection
According to the above information, we know pump flow is 70m³/(4h*0.85)=20.6m³/h, lift is 50 meters, The pump can choose Ruirong's R150-DS-05 model, the power of the motor is 4kW, applicable well diameter is 150mm. Following is the pump specifications:
Solar pumping inverter selection
The pump motor power is 4kW, the input voltage is three-phase 380Vac, so the pump inverter selects JFY SPRING 5500 model, the output rated power is 5.5kW.
The design of the PV panel
The selection of pumping inverter is SPRING 5500, rated output power is 5500W, considering the local good lighting conditions, we recommend the power of the panel is 1.1 times rated power of the inverter.
Shenzhen Jingfuyuan Technology Co., Ltd (Abbr. JFY) was Founded in 2003. It’s a national high-tech enterprise that integrating R&D, production, sales and service. The company has been focusing on the power electronics field over 15 years, It has 0.55kW-75kW solar pumping inverter, single phase/three phase AC output , supports a variety of pump motors, IP65 protection level (22kW or more power increased outdoor cabinet, protection grade is IP54), suitable for Outdoor use, and can choose diesel or commercial power as the backup power source, support 24 hours a day to pump water. JFY always adheres the conception of " God rewards the diligence and Strive for excellence" and will try our best to create more value for customers.
