Bio-Inspired, Low-Cost, Self-Regulating Valves for Drip Irrigation in Developing Countries

Abstract

We use nonlinear behavior of thin-walled structures — an approach inspired by biological systems (the human airway, for example) — to address one of the most important problems facing subsistence farmers in developing countries: lack of access to inexpensive, water-efficient irrigation systems. An effective way of delivering water to crops is through a network of emitters, with up to 85% of the water delivered being absorbed by plants. However, of the 140 million hectares of cropped land in India alone, only 61 million are irrigated and just 5 million through drip irrigation. This is, in part, due to the relatively high cost of drip irrigation. The main cost comes from the requirement to pump the water at relatively high pressure (>1bar), to minimize the effect of uneven terrain and viscous losses in the network, and to ensure that each plant receives the same amount of water. Using a prototype, we demonstrate that the pressure required to drive the system can be reduced significantly by using thin-walled structures to design emitters with completely passive self-regulation that activates at approximately 0.1bar. This reduction in driving pressure could help bring the price of drip irrigation systems from several thousand dollars to approximately $300, which is within reach of small-scale farmers. Using order-of-magnitude calculations, we show that due to increased sensitivity of the proposed design to the applied pressure differential, a pressure compensating valve for drip irrigation could be built without using costly silicone membranes.

A Novel Pressure Compensating Valve for Low-Cost Drip Irrigation

“…In previous work [4], we developed a bio-inspired pressure compensating solution which exploits the nonlinear behavior of thin-walled structures such as blood vessels. The work within this paper presents an alternative to this approach which exploits the physics observed in the resonating nozzle of a deflating balloon.…”

“…This relatively high cost makes drip irrigation infeasible for millions of subsistence farmers, who typically cultivate one acre (0.4ha) of land or less [2]. These farmers have minimal resources for investment in new equipment, yet they are the [4]. ones who need it most, as higher agricultural yields would significantly improve their quality of life.…”

Control of Flow Limitation in Flexible Tubes

“…The ability to parametrically design Starling resistors to achieve a desired activation pressure and operating flow rate could be valuable to numerous industrial applications. For example, Zimoch et al [2] demonstrated that pressure compensating Starling resistors could be designed to deliver the correct flow rate and activation pressure for low-cost drip irrigation.…”