Development of 3D Reversible Smart Energy‐Saving Devices for Adaptive Energy Management

Conventional 2D thin-film-based energy-saving devices face limitations in controlling phase transition temperatures and in material selectivity. In contrast, 3D devices offer better temperature tunability and broader material options for surface coatings. However, existing designs still face challenges like limited deformation and asymmetric structures, hindering adaptation to varying sunlight incidence and azimuth angles. This study proposes symmetric 3D devices incorporating a shape memory alloy actuator, black paint for solar absorption, and a polydimethylsiloxane (PDMS)/Al2O3 composite as an RC film, exhibiting the following characteristics: i) reversible, continuously tunable 3D mechanical deformation between solar heating (SH) and radiative cooling (RC) modes via a temperature-responsive actuator; ii) autonomous operation without external power or manual intervention, ensuring energy-saving functionality; and iii) effective operation across diverse climates with durable, flexible, and adaptable design and adjustable transition temperatures for enhanced thermal responsiveness. Theoretical simulations confirm maximum cooling power reduction of 6.8% in summer and heating power reduction of 5.6% in winter. Performance evaluations under varying tilt angles and solar incidence, along with climate simulations across 15 global zones, validate the effectiveness and adaptability of the device for real-world applications. These findings highlight its potential as a scalable, sustainable, energy-efficient solution for future architectural and environmental uses.