Energy-efficient technologies, particularly electrochromic devices (ECDs), have shown significant potential for use in smart window applications. These devices can effectively modulate optical properties, including transmittance and color, at low voltage. This review discusses the structure and working principles of ECDs, as well as their material components. Key elements include electrochromic (EC) films, such as tungsten oxide (WO3), which achieve 73.1% optical modulation and a coloration efficiency of 70.5 cm2/C. Additionally, transparent conducting electrodes, like silver (Ag) nanowires, offer 85% transmittance at a wavelength of 550 nm and have a resistance of 30 Ω/sq. Furthermore, the electrolytes used in these devices include quasi-solid PVA-H2SO4 systems with an ionic conductivity of 285.5 mS/cm. Highlighted automation approaches include integration with luminescent solar concentrators (Solar Energy 231:857–879, 2022), as reported by A. Purabgola (Thin films for planar solar cells of organic-inorganic perovskite composites. In hybrid perovskite composite materials, Woodhead Publishing, UK, 2021) (LSCs) and electrochromic supercapacitors (ECSs), yielding devices with tunable visible transmittance from 36.8 to 10.2%, coloration time of 0.9 s, and energy density of 23.3 mWh/m2. Another system using a dual-mode triboelectric nanogenerator (TENG) demonstrated voltage outputs up to 140 V and power densities of 130 mW/m2, with the ECD switching from 53.5% to 20.9% transmittance at 695 nm. A galvanic-cell-powered flexible ECD using W18O49 nanowires achieved self-coloration within 14 s, with bleaching times as low as 250 s, and retained 80% contrast after 450 cycles. Photovoltaic and triboelectric-assisted configurations show self-sufficiency ratios exceeding 8:1, where harvested energy surpasses consumption for switching and sensing functions. Building-scale simulations at LBNL and NREL further confirm that EC glazing can achieve net-positive regulation, consuming less than 2 W m−2 while reducing total building energy by 25–32% across multiple climates. The study also explores quartz as a high-stability substrate and basalt-based materials as potential solid electrolytes. These results highlight the feasibility of self-powered, durable, and high-performance ECDs for intelligent, off-grid applications. Future directions include improving NIR modulation, cycling life, and eco-friendly material integration to enable scalable deployment in sustainable architecture. Graphical Abstract

Self-Regulating Electrochromic Windows: A State-of-the-Art Review of Energy-Autonomous Systems

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发表日期：

2026年2月17日

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B. Aadinarayanan,
Balasubramanian Kandasubramanian

摘要

Energy-efficient technologies, particularly electrochromic devices (ECDs), have shown significant potential for use in smart window applications. These devices can effectively modulate optical properties, including transmittance and color, at low voltage. This review discusses the structure and working principles of ECDs, as well as their material components. Key elements include electrochromic (EC) films, such as tungsten oxide (WO₃), which achieve 73.1% optical modulation and a coloration efficiency of 70.5 cm²/C. Additionally, transparent conducting electrodes, like silver (Ag) nanowires, offer 85% transmittance at a wavelength of 550 nm and have a resistance of 30 Ω/sq. Furthermore, the electrolytes used in these devices include quasi-solid PVA-H₂SO₄ systems with an ionic conductivity of 285.5 mS/cm. Highlighted automation approaches include integration with luminescent solar concentrators (Solar Energy 231:857–879, 2022), as reported by A. Purabgola (Thin films for planar solar cells of organic-inorganic perovskite composites. In hybrid perovskite composite materials, Woodhead Publishing, UK, 2021) (LSCs) and electrochromic supercapacitors (ECSs), yielding devices with tunable visible transmittance from 36.8 to 10.2%, coloration time of 0.9 s, and energy density of 23.3 mWh/m². Another system using a dual-mode triboelectric nanogenerator (TENG) demonstrated voltage outputs up to 140 V and power densities of 130 mW/m², with the ECD switching from 53.5% to 20.9% transmittance at 695 nm. A galvanic-cell-powered flexible ECD using W₁₈O₄₉ nanowires achieved self-coloration within 14 s, with bleaching times as low as 250 s, and retained 80% contrast after 450 cycles. Photovoltaic and triboelectric-assisted configurations show self-sufficiency ratios exceeding 8:1, where harvested energy surpasses consumption for switching and sensing functions. Building-scale simulations at LBNL and NREL further confirm that EC glazing can achieve net-positive regulation, consuming less than 2 W m⁻² while reducing total building energy by 25–32% across multiple climates. The study also explores quartz as a high-stability substrate and basalt-based materials as potential solid electrolytes. These results highlight the feasibility of self-powered, durable, and high-performance ECDs for intelligent, off-grid applications. Future directions include improving NIR modulation, cycling life, and eco-friendly material integration to enable scalable deployment in sustainable architecture.

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