Researchers from China's Northwest A&F University have proposed to combine photovoltaics with compressed air energy storage (CAES) to power sprinkler irrigation systems.
They explained that sprinklers usually work at higher working pressure and more energy consumption than drip irrigation and subsurface irrigation systems, and that photovoltaics alone may have some limitations in solving issues derived from its intermittent energy supply. “The spraying quality cannot be guaranteed,” they added. “Therefore, energy storage devices are often needed for a stable energy supply.”
The CAES-PV irrigation system designed by the group consists of a water source, a 150 W water pump, a 240 W PV array consisting of two 120 W panels, a pressure tank made of carbon steel, a time-delay switch, and a sprinkler. The PV panels power the pump to draw water from the water source and inject it into the closed pressure tank.
“With the increased water in the tank, the air in the tank is gradually compressed,” it stressed. “When the internal energy of the air in the tank reaches the critical value, the valve of the tank opens and the internal energy of the air is converted into kinetic energy of the spray water, supporting the spraying lasts for a few seconds.”
The system performs this process in cycles triggering pulse spraying.
Through a series of tests, the academics found that the proposed CAES-PV sprinkler is able to provide stable standardized intermittent pulse spraying. “Reasonable selection of energy storage regulation factor and nozzle combination spacing can achieve a spraying uniformity coefficient of 91.5 %,” they specified, noting that the system can also provide high pressure and low intensity high-quality spraying.
The novel system design is presented in the paper “Solar photovoltaic coupled with compressed air energy storage: A novel method for energy saving and high quality sprinkler irrigation,” published in Agricultural Water Management.
“Due to the limited research in this respect, further research should be carried out in terms of the energy conversion efficiency of CAES-SPV sprinkling irrigation system, as well as soil water infiltration, soil microenvironment changes and their effects on crop yield and quality under low-intensity and long-term intermittent spraying,” the research group said, looking forward to improving the technology.
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