Scientists built a sunflower-inspired cooling system that delivered 135% more cooling power at solar noon than a fixed horizontal surface

Researchers in China have developed a radiative cooling system inspired by the way sunflowers track the sun, with experiments showing a 135% increase in cooling flux at solar noon compared with a fixed horizontal version of the same selective emitter. The system, called dynamic sky view factor steering (DSVFS), changes the orientation of a cooling surface to reduce its exposure to direct sunlight while retaining access to the sky. The work is reported in the September 2026 arXiv preprint Round-the-Clock Sub-Ambient Cooling via Dynamic Sky View Factor Steering. Five of the six authors, Qiuyu Chen, Minghao Dong, Zheng Zhang, Xiaodong Zhao and Zhen Chen, are affiliated with Southeast University in Nanjing. Peng Xiao is affiliated with the State Grid Electric Power Research Institute, State Grid Jiangsu Electric Power Co., Ltd., Nanjing. The study is a preprint and has not yet undergone peer review.How the sunflower-inspired cooling system worksRadiative cooling allows a surface to release heat as infrared radiation toward the sky. During the day, however, sunlight can offset that cooling effect. The DSVFS system addresses this by tilting the emitter so that its surface is aligned with the incoming direct sunlight, reducing the area exposed to the solar beam. Tilting the surface also reduces part of its view of the sky, creating a trade-off between avoiding direct sunlight and maintaining radiative heat exchange. The researchers use a solar sensor and a dual-axis gimbal to adjust the emitter's orientation as the sun moves. Under an overcast sky, the system returns to a horizontal position because solar irradiation becomes more isotropic, while at night it returns to horizontal after sunlight disappears.The selective emitter produced 71 W/m² at solar noonThe main experimental comparison involved a homemade selective radiative-cooling paint with a measured solar absorptivity of 4.6%. At solar noon, the emitter equipped with DSVFS produced 71 W/m² of cooling flux, compared with 30 W/m² for the same paint in a horizontal configuration. The researchers describe this as a 135% increase in cooling flux. Because the reported values are rounded, calculating the percentage directly from 71 and 30 gives about 137%, so 135% is best presented as the figure reported by the authors. The DSVFS emitter was also reported to be 1.1°C cooler than the horizontal emitter at noon and 2.2°C below the surrounding air. During the daytime, it averaged 0.8°C cooler than the horizontal paint and 3°C below ambient. The steering mechanism consumed an average of about 2 W/m², while the paper reports cooling-flux enhancements ranging from 40 to 360 W/m² across different emitter types.A near-blackbody emitter also achieved sub-ambient coolingThe researchers separately tested a near-blackbody emitter made from an aluminium plate coated with commercial black paint. The paint had a measured solar absorptivity of 99.6%, meaning it absorbed almost all incoming sunlight. The setup used a 25-micrometre-thick nanoporous polyethene barrier to suppress residual diffuse solar radiation while allowing infrared emission through. In the fixed horizontal configuration, the near-blackbody emitter failed to achieve sub-ambient cooling during the daytime. With DSVFS, it remained an average of 6.2°C below ambient throughout the daytime and reached 5.1°C below ambient at noon. At noon, the DSVFS emitter was also 23.9°C cooler than the horizontal black-paint emitter. The researchers additionally conducted an experiment on a cloudy day using black paint to examine the system under different weather conditions.Earlier research used direction in a different wayThe new system is related to earlier research showing that the direction of sunlight can be exploited for daytime radiative cooling. A 2018 Nature Communications study titled Passive directional sub-ambient daytime radiative cooling used a polished aluminium disk to reflect direct sunlight and a white, infrared-transparent polyethene cover to minimise diffuse sunlight. Around solar noon, the researchers measured a minimum temperature of 6°C below ambient and a maximum cooling power of 45 W/m². The study also reported a solar-black emitter reaching 5.5°C below ambient at noon. The 2026 preprint cites this work among earlier approaches involving directional control of radiative cooling.Separately, a 2017 Nature Energy study titled Sub-ambient non-evaporative fluid cooling with the sky demonstrated fluid-cooling panels using spectrally selective surfaces. The researchers reported water cooling of up to 5°C below ambient and a heat-rejection flux of up to 70 W/m². They also estimated that cooling accounted for about 15% of global electricity consumption and 10% of global greenhouse-gas emissions at the time. That study provides broader background on radiative cooling rather than evidence for the directional mechanism used in the new DSVFS system.Summer modelling suggests further cooling potentialThe researchers also modelled the potential energy benefit of DSVFS using commercial-grade paint, with a reported solar reflectivity of 75.7%, in city case studies covering June through September. The paper reports that most areas in China and the United States could save more than 150 kWh/m² during summer, with a maximum of 200 kWh/m² in the calculations. These are modelled summer results, not measured annual energy savings from a building operating with the technology. In a comparison of four representative cities, the researchers found that the commercial paint in a fixed horizontal position could not achieve sub-ambient cooling, while the DSVFS configuration produced daytime cooling-energy savings of up to 200 kWh/m².