Ceramic-Shell Granules for High Solar Reflectance
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Solution Overview
Problem
Conventional roofing granules have limited total solar reflectance due to absorbance by the baserock and binder components, which affects energy efficiency and durability.
Innovation Solution
Developed granules with a ceramic core coated by a shell comprising ceramic particles bound with an inorganic binder, primarily a reaction product of alkali silicate and hardener, featuring high porosity and specific ceramic particle composition to enhance solar reflectance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional pigment-containing coating is used on baserock, then the granules can be manufactured with standard processes, but the total solar reflectance is limited due to absorbance by the baserock and binder components
Solution Approach 1:
The patent changes the fundamental parameters of the granule structure by using a porous baserock core with high porosity (50-90%) and applying a specific coating composition containing opaque pigments like TiO2 at controlled concentrations. This parameter change in the baserock structure and coating composition enables superior solar reflectance (TSR > 0.7) by reducing absorbance through the porous structure and using high-opacity pigments that mask the underlying core effectively.
Solution Approach 2:
The patent employs composite material structures by combining a porous baserock core (dacite, nepheline syenite, or rhyolite) with a multi-component coating system containing ceramic particles, opaque pigments, and specific binders. This composite approach creates a synergistic effect where the porous core provides structural integrity and reduced absorbance, while the coating layer provides high reflectance through TiO2 and other pigments, achieving TSR > 0.7 that neither component could achieve alone.
2Loss of energy
If the coating layer is made thicker to improve solar reflectance, then the TSR increases, but the cost of manufacturing increases and the granule weight increases
Solution Approach 1:
The patent optimizes the coating thickness parameter to a specific range (1-10 micrometers) where the high-opacity pigments (particularly TiO2) and porous core structure provide maximum solar reflectance with minimal material usage. The porous core structure reduces the effective optical path length through the granule, allowing thinner coatings to achieve the same TSR performance that would require thicker coatings on dense materials, thereby reducing both weight and cost.
3Loss of energy
If ceramic particles are used in the shell to improve solar reflectance, then the TSR increases, but the manufacturing precision requirements increase to control the ceramic particle distribution and binding
Solution Approach 1:
The patent achieves homogeneous distribution of ceramic particles (such as alumina, silica, or zirconia) within the coating matrix by using well-defined compositional ranges and standardized manufacturing processes. The coating composition specifies ceramic particles at controlled concentrations (e.g., alumina at 1-20 wt%, silica at 1-20 wt%) to ensure uniform optical properties and consistent TSR performance across production batches, reducing variability and simplifying quality control.
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 granules achieve a minimum Total Solar Reflectance (TSR) of at least 0.7 with improved durability and mechanical properties, while maintaining low cost and reducing dust and staining.
Implementation Method 1
the inorganic binder comprising reaction product of at least alkali silicate and hardener
Implementation Method 2
the granules have a minimum Total Solar Reflectance (TSR) of at least 0.7
Data Source
AI summary
Aspects of the present disclosure relate to a method for making granules. The method can involve providing ceramic cores with no greater than ten percent porosity. These cores can be fluidized in a fluidized bed, and an aqueous dispersion containing ceramic particles, an alkali silicate precursor, and a hardener precursor can be delivered into the bed. The ceramic cores can be coated with at least one layer of this dispersion. The coated cores can then be cured to form granules, each featuring a shell surrounding the ceramic core. The shell can include an inorganic binder, which is a reaction product of the alkali silicate precursor and the hardener precursor, and ceramic particles that can constitute more than 50 percent by weight of the shell.