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The proposed system uses compressed air to store energy and prevent irrigation pipes from clogging. Two experimental systems were built and tested in China and blockages were reduced by up to 93%.
Researchers at Northwest A&F University in China have developed a novel photovoltaic-powered drip irrigation system, which stores energy in the form of compressed air. The use of compressed air not only regulates the performance of the system, but also ensures uniformity in irrigation output and improves anti-clogging of pipes.
“Photovoltaic-powered drip irrigation is a vital approach to address irrigation needs in regions with limited water resources and energy deficiencies, thereby ensuring the supply of livelihood and horticultural products to local inhabitants,” the academics say. “However, the susceptibility of the drip irrigation system to clogging, as well as fluctuations in photovoltaic output, can significantly affect the quality of irrigation.”
To maximise the systems water-energy balance, the researchers used a sealed pressure tank with a mixture of air and water. This tank is situated between a pump and the drip tubes. The tank is initially filled with air, and once solar energy is available, the pump pushes the water into the tank, effectively compressing the air inside. Once a certain pressure is reached, a valve opens, releasing the stored water in pulses. Once the water is released, the air expands again, allowing the cycle to repeat.
The experimental systems
“During the cycle process, the air volume in the pressure tank undergoes an expansion during each pulse drip irrigation process, thus ensuring consistency of both pulse jet time and discharge rate,” the group explains. “Although the solar panel power and pump water lifting performance vary due to variations in solar irradiance or cloud occlusion during different periods of the day, these differences only alter the water lifting and injection time of each pulse period at different times of the day, without affecting the pulse jet process.”
To test the novel system, the scientists built two experimental setups in Yangling, China. To analyse hydraulic performance, they used a 374 W photovoltaic panel powering a 16 L/min pump. The pump drove water through a 48-metre central pipe, to which eight lateral pipes, each six metres long, were connected. Six emitters were placed on each pump, giving a total of 48 emitters in the entire system. A measuring cup was placed beneath each of them.
The second experimental system focused on anti-clogging performance. For this purpose, muddy water with a sand content of 2 g/L was flowed through four drip tapes. One tape received water directly from the contaminated water tank via a pump, while the other three had a pressure tank between the pump and the tape. In the latter three, the system used the same water-air pressure technique as in the first configuration.
The results
“The system operates in intermittent cyclic pulse drip irrigation mode, with the emitter flow rate varying based on the peak pressure power to ensure flow uniformity of no less than 91.76%,” the group explained. “In addition, the dynamic pulse pressure generated by the system significantly improves the emitter’s anti-clogging performance. During intensified clogging tests, sediment deposition in the side pipe was reduced by 78.95% to 93.36% compared to constant-pressure continuous drip irrigation systems.”
In addition, the team conducted an economic analysis of the system, finding that it will cost $373.13 to implement, equivalent to the initial investment of $103.84 for traditional drip irrigation. However, if only the operating energy consumption and environmental benefits are taken into account, an annual operating benefit of up to $19.41 per mu, which is the traditional Chinese unit of land area, equivalent to about 667 m2, can be achieved.
"The system offers substantial economic and environmental benefits without significant increases in system investment costs, while providing clean and readily available energy for the efficient operation of drip irrigation systems, thus positively contributing to food security," the scientific team concluded.
The system was presented in “ The incorporation of solar energy and compressed air into the energy supply system enhances the environmentally friendly and efficient operation of drip irrigation systems,” published in Agricultural Water Management . |
