Evaporative/solar/thermal radiation regulations

Buildings are estimated to account for approximately 40% of worldwide energy consumption. Dynamic outgoing thermal radiation modulation is an established technique for building thermal management, yet its performance is severely limited by its intrinsic power regulation capability and weather conditions. Theoretically, evaporative cooling (EC) could potentially offer one magnitude higher cooling power. However, the combined regulation of evaporation, outgoing thermal radiation, and solar transmittance for all weather conditions has not been investigated. This paper prototyped a design of triple evaporation/solar/thermal radiation regulative (TER) device which integrates an entangled smart hydrogel composite with a low-E overcoating, achieving a near unity dynamic regulation for evaporation (ΔE_vap, 93.2%), coupled with moderate solar and thermal radiation modulation. The reversible water retention/release mechanism of hydrogel was systematically elucidated by density function theory calculation, small-angle neutron scattering, and ab initio molecular dynamics calculations to understand the improved ΔE_vap due to entanglement. In simulations of an actual-sized building heating/cooling energy saving, this TER device displays a tripled annual heating/cooling energy saving compared with dual solar/thermal radiation regulative design (979 MJ vs. 276 MJ). This advancement in heat-regulative devices offers substantial potential for dynamic thermal management.