Transparent Self-Cooling Window Coatings for Greenhouse Overheating
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Solution Overview
Problem
Greenhouses experience overheating due to excessive non-productive solar radiation, particularly infrared light, which can raise temperatures above 50°C, adversely affecting vegetation productivity, while existing coatings either fail to manage this effectively or compromise transparency.
Innovation Solution
A multi-layered window coating system comprising a passive cooling layer, near-infrared radiation absorption layer, and optionally a near-infrared radiation reflecting layer, formulated with specific metal oxides, binders, dispersing agents, and wetting agents, applied via spraying to maintain transparency and reduce infrared radiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If solar radiation is blocked to reduce temperature, then temperature control is improved, but visible light transmittance deteriorates
Solution Approach 1:
The coating system is divided into multiple functional layers: a first coating layer containing metal oxide particles for infrared radiation management, and a second coating layer with different composition for complementary functionality. This segmentation allows each layer to target specific wavelength ranges, managing thermal radiation while preserving visible light transmission through coordinated design of the layered structure.
Solution Approach 2:
The coating system applies different material compositions and optical properties to different layers, creating local quality variations. The first coating layer is optimized for infrared radiation rejection with specific metal oxide concentrations, while the second layer provides complementary properties. This local differentiation enables selective radiation management across the spectrum while maintaining overall transparency in the visible range.
2Temperature
If infrared radiation is rejected to cool the greenhouse, then temperature control is improved, but coating complexity increases
Solution Approach 1:
The coating system is designed to perform multiple functions simultaneously: the first coating layer with metal oxide particles provides both infrared radiation rejection and contributes to visible light transmission, while the second coating layer complements these functions. This multi-functionality reduces the need for additional separate cooling systems, managing thermal radiation and maintaining transparency through an integrated approach.
3Loss of energy
If metal oxide particles are added to block infrared radiation, then thermal efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The coating system utilizes variations in metal oxide particle concentration, particle size distribution, and layer thickness as controllable parameters to optimize infrared radiation rejection. By adjusting these parameters within specified ranges and applying systematic formulation approaches, the system achieves effective thermal management while maintaining practical manufacturability through controlled variation rather than requiring extreme precision.
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 coating system maintains over 70% visible light transmittance while reducing air temperature by 2-8°C, effectively managing greenhouse temperatures and enhancing thermal efficiency.
Implementation Method 1
The passive cooling layer has a high emissivity in the 8-13 μm range, allowing it to radiate heat to the sky
Implementation Method 2
a near-infrared radiation absorption layer
Implementation Method 3
a near-infrared radiation reflecting layer
Data Source
AI summary
The invention relates to a window for a building structure containing optically transparent and self-cooling coatings on a substrate. The optically transparent and self-cooling coatings has a multi-layered structure including a passive cooling layer, a near-infrared radiation absorption layer and a near-infrared radiation reflecting layer. The optically transparent and self-cooling coatings have a visible light transmittance of more than approximately 70%. In addition, an air temperature under the window under ventilation condition is reduced by at least approximately 2° C., and an air temperature under the window under insulated condition is reduced by at least approximately 8° C.