Vacuum Solar Thermal Panel Seal With Elastic Belt Stress Relief
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Solution Overview
Problem
Existing vacuum solar thermal panels face limitations such as significant dead space between heat absorbers, external heat transfer fluid circuitry, and the use of toxic materials like lead, which restrict long-term high vacuum applications and reduce efficiency at high temperatures.
Innovation Solution
A flat vacuum solar thermal panel design featuring a vacuum envelope with glass and metal plates, a metallic peripheral frame, and a bulk glass-metal seal that reduces stress and uses non-toxic materials, along with infrared low-emitting coatings to enhance efficiency at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soft metal (lead) is used to solder glass plates to metallic spacing frame, then vacuum tight sealing is achieved, but toxicity and environmental restrictions increase
Solution Approach 1:
The invention changes the material parameter from soft metal (lead) to glass frit, transforming the sealing mechanism from metal-based soldering to glass-based fusion bonding. This parameter change eliminates toxicity while maintaining vacuum tight sealing capability through the glass frit's ability to flow and bond glass plates to the metallic frame at elevated temperatures.
Solution Approach 2:
The invention employs a composite sealing system using glass frit as the bonding material that combines properties of both glass and metal adhesion. The glass frit forms a composite joint between the glass plates and metallic spacing frame, achieving vacuum tight sealing without the harmful effects of lead-based soft metals.
2Ease of manufacture
If surface coatings are applied to glass for metallization, then soldering to metallic spacing frame is enabled, but coating deterioration occurs faster than bulk materials
Solution Approach 1:
The invention extracts the metallization function from surface coatings and replaces it with bulk glass frit material. Instead of relying on thin surface coatings that deteriorate quickly, the glass frit provides bulk material properties for durable bonding, eliminating the need for separate metallization layers while achieving both soldering capability and long-term reliability.
Solution Approach 2:
The invention achieves homogeneous bonding through glass frit that matches the thermal and mechanical properties of the glass plates. This homogeneity ensures uniform stress distribution and bonding strength throughout the seal, preventing the differential expansion and coating delamination issues that plague heterogeneous coating-based approaches.
3Adaptability or versatility
If organic sealing materials (glue, silicon rubber, polysulfide) are used, then flexibility and stress relief are improved, but gas permeation occurs over time preventing long term high vacuum
Solution Approach 1:
The invention changes the material parameter from organic polymers to inorganic glass frit, fundamentally altering the sealing mechanism. The glass frit maintains flexibility through its ability to flow and conform to interfaces at bonding temperature, then solidifies into a rigid yet stress-absorbing seal that is impermeable to gas, ensuring long-term vacuum maintenance without the permeation issues of organic materials.
4Reliability
If rigid glass-metal seal is used to maintain vacuum tightness, then sealing reliability is improved, but stress from thermal expansion and pressure differences damages the seal
Solution Approach 1:
The invention changes the physical state parameter of the sealing material from solid-rigid to viscous-flow at bonding temperature. The glass frit is applied in a softened state where it can flow and conform to the glass-metallization interface, creating a mechanically compliant seal that absorbs thermal expansion stresses while maintaining vacuum tightness, then solidifies to provide structural integrity.
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 provides a reliable, long-lasting vacuum envelope with reduced stress on the glass-metal seal, increased efficiency by up to 30% at 265°C, and eliminates the use of toxic materials, while maintaining vacuum tightness and thermal performance.
Implementation Method 1
said glass material is heated above its melting temperature and then cooled below said temperature to make the glass material adhering to the peripheral belt
Implementation Method 2
to make the glass material adhering to the peripheral belt and joining it to the glass plate
Implementation Method 3
with attached multiple heat absorbers in good thermal contact with the same pipe enclosed in said vacuum envelope... provided with a metallic peripheral belt... and a bulk glass-metal seal
Data Source
AI summary
A vacuum solar thermal panel including a vacuum envelope defining a sealed volume and able to withstand atmospheric pressure when evacuated, at least one heat absorber being disposed inside the vacuum envelope, a pipe entering and exiting the envelope and being in contact with the heat absorber, the vacuum envelope including a first plate made of glass, a peripheral frame, a metallic peripheral belt being joined to the first plate by way of a vacuum tight bulk glass-metal seal, including glass material and obtained by fusion and subsequent solidification. The metallic peripheral belt includes at least one elastically deformable portion that prevents the bulk glass-metal seal from getting damaged and is no more vacuum tight when subject to the evacuation process of the envelope and the thermal treatments of the panel and the potential reciprocal displacements of the glass plate and the joined metallic peripheral belt.