Thermoresponsive hydrogel-powered zero-energy greenhouses: intelligent shading and water irrigation

While greenhouse cultivation boosts food production to address population growth, its energy-intensive temperature control and irrigation systems pose significant sustainability challenges. 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 embedded hygroscopic salt enables autonomous atmospheric water harvesting in a wide range of humid environments. Above the thermoresponsive temperatures, the poly(N-isopropylacrylamide) chains collapse, directly squeezing out the liquid water to irrigate drylands, without extra condensers. Simultaneously, the dropped transmittance of solar light efficiently decreases the interior temperatures (1.1-6.0 °C) to mitigate sunscald and reduces soil- and transpiration-driven water loss. As a proof-of-concept application, greenhouse trials confirmed the noticeable efficacy of NA-Li in promoting crop survival rates under thermal shock and doubling productivity, saving 1.02 kg m^-2 water consumption. By synchronizing atmospheric water capture, on-demand irrigation and adaptive radiative shading in a single material, this study connected the interdisciplinary fields of horticulture, thermal energy management, water and materials, which could provide a feasible solution to water and temperature management in greenhouses and a technical route for its sustainable development.