Vacuum Solar Thermal Panel Perimeter Structure for Low Weight
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Solution Overview
Problem
Existing vacuum solar thermal panels are heavy due to thick perimeter walls required for stiffness, making them difficult to handle and maintain the vacuum tight glass-metal seal.
Innovation Solution
A lightweight and thin perimeter wall structure is achieved using a metallic perimeter frame with strategically placed bearing elements and traction rods, supported by longitudinal and transverse elements, which are tensioned to resist atmospheric pressure without significant deformation, and heat absorbers and pipes are designed for minimal contact and thermal expansion accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the perimeter wall is made thick to obtain desired stiffness, then the structural strength is improved, but the panel weight increases and becomes difficult to handle
Solution Approach 1:
The perimeter wall is segmented into a modular structure consisting of a perimeter frame, longitudinal elements, transverse elements, and bearing elements. This segmentation allows each component to be optimized for its specific function, enabling the use of thinner, lighter materials while maintaining overall structural stiffness through the coordinated arrangement of multiple elements.
Solution Approach 2:
The perimeter wall employs a composite structure combining metallic materials (frame and support elements) with glass plates. This composite approach allows the metal components to provide structural strength and stiffness while the glass provides thermal insulation and vacuum containment, achieving high strength-to-weight ratio.
2Weight of stationary object
If the perimeter wall is made thin to reduce weight, then the panel becomes easier to handle, but the perimeter wall suffers excessive deformation under atmospheric pressure
Solution Approach 1:
The perimeter wall is divided into multiple functional segments: the perimeter frame provides the basic structure, longitudinal elements provide span-wise support, transverse elements provide cross-support, and bearing elements provide localized support points. This segmentation distributes the atmospheric pressure loads across multiple components, preventing excessive deformation of individual thin elements.
Solution Approach 2:
The support structure extends into three dimensions with longitudinal elements running the length of the panel, transverse elements crossing perpendicular to them, and bearing elements positioned at specific points. This 3D framework provides multi-directional support, significantly enhancing the stiffness-to-weight ratio compared to a simple flat wall structure.
3Power
If the pipe has extensive contact with the vacuum envelope, then heat transfer efficiency is improved, but heat loss to the vacuum envelope increases
Solution Approach 1:
The pipe is extracted from direct contact with the vacuum envelope and repositioned to contact only the heat absorber plates. This separation eliminates the thermal bridge between the pipe and the vacuum envelope, preventing heat loss to the envelope while maintaining efficient heat transfer from the heat absorbers to the fluid in the pipe.
Solution Approach 2:
The heat absorber plates serve as an intermediary between the pipe and the vacuum envelope. Heat is transferred efficiently from the pipe through the heat absorber plates, which are in contact with both, while the pipe itself remains isolated from the vacuum envelope, preventing direct heat loss to it.
4Reliability
If rigid support structure is used to maintain vacuum tight seal, then sealing reliability is improved, but accommodation of thermal expansion is reduced
Solution Approach 1:
The support structure incorporates dynamic elements that can adapt to thermal expansion. The bearing elements and their mounting arrangements allow for movement and adjustment, enabling the structure to accommodate changes in dimensions of the glass plates and pipe due to thermal effects while maintaining the vacuum seal integrity.
Solution Approach 2:
The structure is designed to accommodate parameter changes in the materials due to temperature variations. The bearing elements and support connections are configured to allow for dimensional changes in the glass plates and metal components, adjusting their positions or forces to maintain sealing contact while accommodating thermal expansion and contraction.
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 results in a significantly lighter panel that maintains structural integrity and minimizes heat transfer losses, allowing for easier handling and assembly while maintaining efficient heat transfer and thermal expansion accommodation.
Implementation Method 1
Vacuum is kept inside the envelope enclosing the heat absorbers and part of the pipe connected to them, in order to prevent heat from escaping to the external environment by means of convection
Implementation Method 2
a glass plate transparent to visible solar radiation... The solar radiation enters the envelope through the glass plate, is absorbed by the heat absorbers and converted into heat
Data Source
AI summary
A vacuum solar thermal panel includes a vacuum envelope defining a sealed volume able to withstand atmospheric pressure when evacuated. The envelope includes a first plate made of glass, a second plate facing the first plate, a perimeter frame disposed between the first and second plate close to their edge, a metallic perimeter belt joining the perimeter frame to the first plate, a plurality of spaced apart bearing elements disposed against the edges of the first and second plate, and a plurality of traction rods joining the bearing elements with the perimeter frame to pull the perimeter frame toward the bearing elements, in order to limit the deformation of the perimeter frame under the external atmospheric pressure, when the envelope is evacuated.