Reversible Optical Window Coating for Seasonal Infrared Control
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Solution Overview
Problem
Conventional windows allow both visible and infrared solar light into buildings, leading to temperature regulation challenges, as they either increase heating needs in winter or cooling demands in summer, with existing smart passive windows failing to efficiently reflect or absorb infrared light based on seasonal changes.
Innovation Solution
A passive window filter coated with alternating thin metallic and dielectric layers, which can be reversed to change its optical properties depending on the direction of solar light incidence, featuring an infrared absorbing layer on one side and an infrared reflecting layer on the other, along with a photochromic and UV absorbing material for adaptive visible light control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional glass windows are used to allow visible light into buildings, then interior lighting is improved, but infrared heat from solar light also enters causing temperature regulation problems
Solution Approach 1:
The window is divided into two distinct sides: one side with infrared absorbing properties and the other with infrared reflecting properties. This segmentation allows selective infrared management while maintaining visible light transmission, resolving the contradiction between lighting and temperature control.
Solution Approach 2:
Different regions of the window (front and back sides) are given different optical properties - one side absorbs infrared while the other reflects it. This local differentiation enables the window to optimize thermal performance for different seasonal conditions while preserving illumination benefits.
2Adaptability or versatility
If a passive reversible window-filter with alternating metallic and dielectric layers is implemented, then infrared reflection and absorption capabilities are achieved, but device complexity increases
Solution Approach 1:
The window-filter is made asymmetric by implementing different infrared interaction properties on each side - one side absorbs infrared while the other reflects it. This asymmetric design enables seasonal adaptability through simple flipping without requiring complex active control mechanisms.
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
The solution effectively regulates indoor temperatures by reflecting or absorbing infrared light based on the season, reducing heating and cooling loads while maintaining visible light transmission, thus enhancing energy efficiency and comfort.
Implementation Method 1
absorb most of the infrared light in winter (colder) temperatures
Implementation Method 2
reflect most of the infrared light in summer (warmer) temperatures
Implementation Method 3
The filter is made asymmetric by implementing a photochromic material on one side
Data Source
AI summary
An energy efficient optical window has different optical properties when irradiated by solar light from front or back side of the window. The window is used to reflect most of the infrared light at summer times, leaving the interior cooler and to absorb most of the infrared light at winter times, making the interior hotter by heat transfer from the hot window pane. Mechanical reversal of the window, inside out, is used to apply the needed version for winter and summer. The window is coated with alternating thin metallic and dielectric layers that transmit most of the visible light while reflecting most of the infrared part of the spectrum when impinged by solar light on one side and transmit most of the visible light while absorbing most of the infrared part of the spectrum when impinged by solar light on the other side.