Solar Thermal Unit Split-Flow Design to Reduce Radiative Losses
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Solution Overview
Problem
Conventional solar thermal units have inefficiencies due to hot outer surfaces leading to radiative losses and uneven heat distribution, which reduces their thermal energy conversion efficiency.
Innovation Solution
The solar thermal unit employs a split-flow design with a glazing layer and a porous light absorbing material layer, where a heat-absorbing fluid flows through multiple paths, collecting heat from both surfaces and internal layers, creating a temperature gradient that directs heat away from the outer layers and retains it in insulated areas, enhancing energy conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solar thermal units are used with a simple absorber design, then the structure is simple and easy to manufacture, but radiative losses occur from hot outer surfaces and heat distribution is uneven, reducing thermal energy conversion efficiency
Solution Approach 1:
The absorber is segmented into multiple layers including a selective absorber layer, a transparent insulating layer, and a reflective layer. This segmentation allows each layer to perform its specific function: the selective absorber layer absorbs solar radiation, the transparent insulating layer reduces radiative losses, and the reflective layer redirects heat back into the absorber, thereby reducing energy losses while maintaining manufacturing feasibility
Solution Approach 2:
Different regions of the absorber assembly are given different thermal and optical properties. The selective absorber layer has high solar absorptance but low thermal emittance, the transparent insulating layer has specific thermal conductivity properties, and the reflective layer has high reflectance. This local differentiation of material properties optimizes heat retention and distribution while managing radiative losses
2Device complexity
If conventional solar thermal units are used with uniform heat distribution, then the structure is simple, but hot outer surfaces create radiative losses to the environment
Solution Approach 1:
The absorber is divided into functional layers with the transparent insulating layer positioned between the selective absorber and the environment. This segmentation creates a thermal barrier that reduces radiative losses from outer surfaces while allowing the selective absorber to maintain its heat-absorbing function, thereby reducing energy losses without excessive structural complexity
Solution Approach 2:
The transparent insulating layer acts as an intermediary between the hot selective absorber layer and the cooler external environment. This intermediary layer has high transparency to solar radiation but low thermal conductivity, allowing it to block radiative losses while maintaining heat distribution within the absorber system
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 configuration results in improved thermal energy conversion efficiency by reducing radiative losses and optimizing heat retention within the unit, with the potential for integrated solar thermal and photovoltaic energy generation.
Implementation Method 1
a porous light absorbing material layer spaced apart from the glazing layer. The heat absorbing fluid may flow through the solar thermal unit along a fluid path from the inlet to the outlet
Implementation Method 2
The temperature gradient may increase along the depth of the solar thermal unit in the direction that the heat absorbing fluid flows along either fluid path from the inlet to the outlet
Implementation Method 3
The solar thermal unit may also have an insulation layer below and spaced apart from the porous light absorbing material layer
Implementation Method 4
A solar thermal unit may have a glazing layer having an outer surface and an inner surface, the inner surface being below and spaced apart from the outer surface
Data Source
AI summary
Solar thermal units and methods of operating solar thermal units for the conversion of solar insolation to thermal energy are provided. In some examples, solar thermal units have an inlet, and a split flow of heat absorbing fluid to either side of the solar thermal unit, along a first fluid flow path and a second fluid flow path. Optionally, one or more photovoltaic panels can be provided as part of the solar thermal unit, which may convert solar insolation to electric power that may be used by a system connected to the solar thermal unit.