Electrochromic Window UV Protection and Charge Sweeping
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Solution Overview
Problem
Traditional electrochromic (EC) window coatings are static and not well-suited for varying climates, as they do not effectively modulate near-infrared (NIR) radiation and can suffer from irreversible photochromic darkening due to ultraviolet (UV) exposure, leading to reduced optical dynamic range and durability.
Innovation Solution
An electrochromic system comprising a working electrode, counter electrode, and a solid-state polymer electrolyte, with an ionically conductive and electrically insulating protective layer, and a control unit that applies a sweep voltage when the open circuit voltage drops below a threshold, periodically sweeping away photoelectrochemically generated charge to prevent darkening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional EC materials are used to modulate visible light, then visible spectral region control is improved, but NIR radiation remains unchanged and UV exposure causes performance degradation
Solution Approach 1:
The patent segments the spectral control function by introducing separate functional layers: a working electrode for visible light modulation and a Bragg reflector for UV radiation reflection. This segmentation allows independent optimization of visible light control and UV protection, resolving the contradiction between visible light modulation and UV-induced degradation.
Solution Approach 2:
The patent introduces a Bragg reflector as an intermediary layer between the EC materials and UV radiation. This intermediary reflects UV radiation away from the working electrode, protecting the EC materials from UV degradation while maintaining their visible light modulation functionality.
2Loss of energy
If static window coatings are used to reject solar heat gain, then energy efficiency in warm climates is improved, but adaptability to varying climates is reduced
Solution Approach 1:
The patent transforms static window coatings into dynamic electrochromic systems that can reversibly change optical properties. The EC materials and Bragg reflector configuration enable dynamic adjustment of both visible and NIR radiation transmission, allowing the window to adapt to varying climate conditions and optimize energy efficiency across different environments.
3Illumination intensity
If photochromic darkening occurs from UV exposure, then temporary shading is achieved, but irreversible darkening reduces optical dynamic range
Solution Approach 1:
The patent applies preliminary anti-action by placing the Bragg reflector to prevent UV radiation from reaching the working electrode in the first place. This preventive measure stops photochromic darkening before it occurs, maintaining the full optical dynamic range and reversible electrochromic functionality throughout the device lifetime.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enhances the modulation of NIR and visible spectral regions, reduces irreversible darkening, and improves the long-term durability of EC devices by periodically removing trapped charge, maintaining optical performance and energy efficiency across different climates.
Implementation Method 1
a solid state electrolyte disposed between the counter electrode and the working electrode
Implementation Method 2
an ionically conductive and electrically insulating protective layer disposed between the electrolyte and the working electrode
Implementation Method 3
an ionically conductive and electrically insulating protective layer disposed between the electrolyte and the working electrode
Implementation Method 4
a first Bragg reflector configured to selectively reflect UV radiation away from the working electrode
Implementation Method 5
EC window coatings undergo a reversible change in optical properties when driven by an applied potential
Data Source
AI summary
An electrochromic system and method for controlling photochromic darkening of an electrochromic device, the system including an EC device, a control unit, a voltage detector, and a power supply. The EC device includes a working electrode, a counter electrode, a solid-state polymer electrolyte disposed therebetween, and an ionically conductive and electrically insulating protective layer disposed between the electrolyte and the working electrode. The control unit is configured to control a sweep voltage applied between the working and counter electrodes, such that the sweep voltage is applied when an open circuit voltage (OCV) between the working and counter electrodes is less than a threshold voltage.