Modeling and designing the future of drip irrigation : a validated parametric analysis used to design low power, pressure compensating drip emitters

Abstract

Drip irrigation is a means of distributing the exact amount of water a plant needs by dripping water directly onto the root zone. It can produce up to 90% more crops than rain-fed irrigation, and reduce water consumption by 70% compared to conventional flood irrigation. In the coming years, the demand for new, low-cost, low-power drip irrigation technology will continue to grow, particularly in developing countries. It will enable millions of poor farmers to rise out of poverty by growing more and higher value crops, while not contributing to overconsumption of water. The key inhibitor to drip adoption has been the high initial investment cost. A cost and pressure analysis revealed that a reduction in activation pressure of pressure compensating (PC) drip emitters - which can maintain a constant flow rate under variations in pressure, to ensure uniform water distribution on a field - can reduce the cost of off-grid drip systems by up to 50%. These emitter have been designed and optimized empirically in the past. In this thesis, I present a parametric model that describes the fluid and solid mechanics that govern the behavior of a common PC emitter architecture, which uses a flexible diaphragm to limit flow. The model was validated by testing nine prototypes with geometric variations, all of which matched predicted performance to within R2 = 0.85. This parametric model was then coupled with a genetic algorithm to achieve a lower activation pressure of 0.15 bar for not only the 8.2 lph emitter, but also the 4, 6, 7 lph emitters. These new drip emitters, with attributes that improve performance and lower cost, are a step closer to making drip irrigation economically accessible to all throughout the world.