Electrospun nanofiber composite for stable and scalable VO₂-based thermochromic smart windows: energy and...

State-of-the-art thermochromic glazing using VO₂ nanoparticles (NPs) is one of the most sustainable cost-efficient solutions for energy-saving smart windows. Prior developments have primarily focused on improving their optical performance, such as increasing the luminescence (visible) transmittance (Tlum) and solar modulation ability (ΔT_sol), while lowering switching temperature (TMIT). However, the current critical issues include the low environmental stability of VO₂ NPs, which determines the lifetime and lifecycle of the smart windows, and the high cost and energy-intensive manufacturing process to apply VO₂. These are unsolved issues which remain key obstacles for market adoption of VO₂ based thermochromic windows. Herein, we demonstrate a nanofiber (NF) based composite system, where W-doped VO₂ NPs embedded in crosslinked NFs were used as the active material and refractive index matched epoxy resin was used as the protection matrix, to ensure environmental stability of W-doped VO₂ NPs during the lifetime of operation. The cost-efficient, low-energy input electrospinning technique allows for precise control over the distribution of NPs in the composite, while minimizing aggregation. The room-temperature, solution-based approach offers a pathway toward cost-effective large-area fabrication. Prepared samples with excellent optical properties (Tlum∼67% and ΔT_sol ∼20%) showed no decline in thermochromic performance and retained ∼99% solar modulation ability after 1700 hours of exposure to an accelerated environmental aging test (60 °C and 95% relative humidity), and retained ∼99% solar modulation ability over 6 months of practical exposure to an average 20 °C temperature and 74% relative humidity in Florida, USA. The energy analysis showed potential annual energy saving of up to 27 kWh per VO₂ (m²) and 32 kWh per VO₂ (m²) for heating and cooling, respectively, and highlighted the impact of VO₂ glazing with improved thermal properties and various TMITon carbon emission reduction across the U.S. climate zones.