Thermal-Responsive Smart Windows with Passive Dimming and Thermal Energy Storage

Chromogenic smart windows are one of the key components in improving the building energy efficiency. By simulation of the three-dimensional network of polymer hydrogels, thermal-responsive phase change materials (TRPCMs) are manufactured for energy-saving windows. For simulated polymer hydrogels, tetradecanol (TD) and a color changing dye (CCD) are filled in situ in poly(n-butyl isobutyrate) (PBB) networks. TRPCMs convert solar energy into thermal energy through a dark blue CCD. The TD phase change material (PCM) absorbs heat energy to become a transparent liquid. Simultaneously, the CCD changes from blue to colorless and transparent at around 45 °C. As a result, as-prepared TRPCMs transform from an opaque state at room temperature to a high-transparency state after melting (74.5%). TRPCMs also show a good thermal storage capacity, with a phase transition enthalpy exceeding 161.9 J g^-1. As-prepared smart materials can simultaneously achieve photothermal conversion, thermal energy diffusion, latent heat storage, and resistance to liquid leakage at the phase interface between opaque and transparent states, providing more options for the design of energy-saving buildings.