Greenhouses that supply themselves with water and provide people in densely populated regions with vegetables: this is the concept that researchers at the National University of Singapore (NUS) used to develop a simple solution to address two of the world’s biggest problems – water scarcity and food shortage.
They created a solar-powered, fully automated device called ‘SmartFarm’ that is equipped with a moisture-attracting material to absorb air moisture at night when the relative humidity is higher and releases water when exposed to sunlight in the day to irrigate plants daily without manual intervention. The SmartFarm device consists of a container with a movable top cover, copper-based hydrogel, a timer, solar panels, a control panel system, motors and tracks for opening and closing the top cover during irrigation, and acrylic wipers.
A specially designed copper-based hydrogel is used to draw moisture from the air. This material is extremely absorbent and takes in moisture up to 300 times its weight. The color of the material changes from brown to dark green to light green when it is saturated with moisture.
At night, the top cover, which is powered by solar energy, opens to allow the copper-based hydrogel to attract atmospheric moisture. During the day, at a pre-set timing, the top cover closes to confine the water vapor allowing it to be condensed on the enclosure’s surface, particularly on the top cover. When the moisture stored in the copper-based hydrogel is completely released due to heating, the top cover automatically opens, and water droplets which are wiped off by the parallel wipers, fall onto the soil to irrigate the plants. The remaining water droplets on the walls of the device continue to provide a humid environment for healthy plant growth.
According to the researchers, one gram of the copper-based hydrogel releases 2.24 grams of water per hour. To make sure that the collected water is suitable, the NUS team tested the quality. And they found that it meets the WHO’s standards for drinking water. Hence, the water collected by the copper-based hydrogel is suitable for drinking and agricultural purposes.
“The SmartFarm concept greatly reduces the demand for freshwater for irritation and is suitable for urban farming techniques such as large-scale rooftop farming,” said Asst Prof Tan. “This is a significant step forward in alleviating water and food scarcity in the near future.“
As a proof-of-concept, the NUS team successfully cultivated Ipomoea Aquatica – commonly known as kangkong, a popular vegetable in Southeast Asia – using the SmartFarm device.
The hydrogel itself was earlier tested by Hawai’i Space Exploration Analog and Simulation (HI-SEAS) for its application for humidity control for space-based agriculture. The team is currently exploring ways to scale the technology in large-scale applications.
