Vacuum Solar Panel Exhaust Cycle With Selective Absorber Heating
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Solution Overview
Problem
Existing methods for performing an exhaust cycle of vacuum solar thermal panels are limited by the maximum temperature of the glass-metal seal, leading to incomplete outgassing and increased internal pressure during panel stagnation, which affects the panel's performance and getter pump capacity.
Innovation Solution
A method that includes a selective heating phase for specific components, such as the solar absorber, to a higher temperature than the vacuum envelope, achieved through irradiation with visible light or Radio Frequency electromagnetic radiation, allowing for more complete outgassing while maintaining the temperature of the envelope components within sustainable limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the panel temperature is increased above the glass-metal seal transformation temperature to achieve complete outgassing, then the outgassing efficiency is improved, but the glass-metal seal suffers structural stress and deformation
Solution Approach 1:
The heating process is segmented into two distinct phases: a first heating phase that heats the overall panel to a maximum temperature sustainable by the glass-metal seal (below transformation temperature), and a second selective heating phase that selectively heats only the solar absorber to a higher temperature (above transformation temperature) using electromagnetic radiation. This segmentation allows different components to be heated to different temperatures appropriate for their thermal tolerances.
Solution Approach 2:
The invention applies local quality by selectively heating only the solar absorber component to high temperatures using electromagnetic radiation (visible light or RF), while keeping the vacuum envelope and glass-metal seal at lower temperatures. The solar absorber is irradiated with electromagnetic radiation that is absorbed and converted to heat locally, creating a temperature gradient where the absorber reaches temperatures above 300°C while the seal materials remain below their transformation temperatures.
2Strength
If the maximum exhaust temperature is limited to below glass-metal seal transformation temperature, then the seal structural integrity is preserved, but the outgassing is incomplete and internal pressure increases during stagnation
Solution Approach 1:
Electromagnetic radiation (visible light or radio frequency radiation) is used as an intermediary to transfer energy selectively to the solar absorber. This intermediary allows heat to be delivered to the absorber without directly heating the glass-metal seal, as the radiation is absorbed by the selective coating of the absorber and converted to thermal energy locally. This mediator enables the absorber to reach temperatures above seal transformation temperatures while the seal remains intact.
Solution Approach 2:
The invention replaces the conventional mechanical/thermal heating system (oven heating that heats everything uniformly) with an electromagnetic radiation-based heating system. This substitution allows selective heating of the solar absorber without uniformly heating the entire panel structure, enabling the absorber to reach higher temperatures while the seal materials remain below their transformation temperatures.
3Ease of manufacture
If uniform heating of the entire panel is used to achieve outgassing, then the heating process is simple, but the glass-metal seal temperature exceeds sustainable limits
Solution Approach 1:
The invention changes the heating parameter from uniform thermal conduction heating to selective electromagnetic radiation heating. By using electromagnetic radiation with specific characteristics (visible light or RF frequencies) that are selectively absorbed by the solar absorber's selective coating, the heating process becomes component-specific rather than uniform. This parameter change allows the absorber to reach temperatures above 300°C while the seal materials remain below their transformation temperatures.
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 approach enables more effective outgassing during the exhaust cycle, reducing internal pressure and preserving the pumping capacity of the getter pump, thus extending panel lifetime and reducing the need for getter material.
Implementation Method 1
The solar radiation thus enters the vacuum envelope through the glass plate and is absorbed by the heat absorbers and converted into heat
Implementation Method 2
the panel temperature is increased in order to provide energy to facilitate desorption of gases from the inside surfaces
Data Source
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AI summary
The present application relates to a method for performing an exhaust cycle of a vacuum solar thermal panel comprising a heating phase of the overall panel up to a maximum temperature (Tm), being the temperature sustainable by at least a panel component. According to the invention it is foreseen a further heating phase being a selective heating phase of some selected panel components, this further heating phase being performed at a second temperature (Th) which is greater than the maximum temperature (Tm).