Thermoresponsive Hydrogel-Powered Zero-Energy Greenhouse: Intelligent Shading and Water irrigation

Abstract

The compound shocks of heat waves and freshwater scarcity are collapsing the yield potential of protected horticulture. Here we present a thermoresponsive poly(N-isopropylacrylamide) hydrogel (NA-Li) that closes the water and thermal energy loop within greenhouses. Below the thermoresponsive temperatures, the embed hygroscopic salt enables an autonomous atmospheric water harvesting at wide humidity environments. Above the thermoresponsive temperatures, the poly(Nisopropylacrylamide) chains collapse, squeezing out the liquid water (≈ 1.02 Kg m⁻²) to directly irrigate drylands. Simultaneously, the film's solar transmittance drops from 85% to 15%, thereby lowering the interior greenhouse temperatures (1.16.0ºC) to mitigate sunscald, and to reduce soil-and transpiration-driven water loss. As a proofof-concept application, greenhouse trials confirmed the noticeable efficacy of NA-Li in promoting crop surviving rates under thermal shock and doubling productivity, saving 73.6kg/d•m 2 water consumption. By synchronizing atmospheric water capture, ondemand irrigation and adaptive radiative shading in a single material, this study connected the interdisciplinary fields of horticulture, thermal energy managements, water and materials, which could provide a feasible solution to water and temperature management in greenhouses and a technical route for interdisciplinary research.