Solar thermal receivers with multi-scale light trapping geometry and features
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Solution Overview
Problem
Conventional solar thermal receivers suffer from significant radiative and convective heat losses due to their design, which reduces their efficiency and requires expensive coatings that degrade over time, limiting the effectiveness of concentrated solar power systems.
Innovation Solution
The design incorporates a fractal arrangement of solar absorbing surfaces and panels at multiple scales, where reflected and radiated energy is trapped by other panels, reducing local radiative view factors and heat losses, and enhancing solar absorptance and thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional panel configurations are used to face incoming solar irradiance, then solar absorptivity is maximized, but radiative and convective heat losses to the environment are also maximized
Solution Approach 1:
The receiver is segmented into multiple cylindrical panels arranged in a circular array, each panel independently oriented to face the sun. This segmentation allows each panel to optimize solar absorption while the overall circular configuration minimizes radiative heat losses by reducing the total surface area exposed to the environment compared to conventional flat plate configurations.
Solution Approach 2:
The invention transitions from conventional two-dimensional flat plate configurations to a three-dimensional circular array of cylindrical panels. This dimensional change allows the receiver to maintain high solar absorptivity through proper panel orientation while simultaneously reducing radiative heat losses by utilizing the volumetric efficiency of a circular geometry, where the interior panels are shielded from environmental radiation.
2Productivity
If receiver temperature is increased to improve power cycle efficiency, then thermal efficiency increases, but radiative heat loss (proportional to T^4) becomes significant
Solution Approach 1:
The circular array segmentation creates interior panels that are thermally coupled to the system but geometrically shielded from the environment. These interior panels can be maintained at high temperatures for efficient power cycles while their radiative heat losses are minimized because they face other receiver panels rather than the cold environment, effectively creating a thermal radiation shield within the circular configuration.
Solution Approach 2:
The interior panels act as intermediary surfaces between the exterior panels and the thermal energy storage/transfer system. They mediate the thermal radiation by absorbing and re-emitting energy internally within the circular array, reducing the direct radiative pathway from high-temperature surfaces to the cold environment, thus enabling high operating temperatures with reduced net radiative losses.
3Use of energy by moving object
If expensive coatings are applied to increase solar absorptivity, then solar energy absorption improves, but the coatings degrade over time requiring reapplication
Solution Approach 1:
The invention applies different surface treatments to different panels within the circular array. Exterior panels receive solar-absorbing coatings optimized for high solar absorptivity, while interior panels utilize geometric light trapping through their cylindrical shape and arrangement, reducing reliance on expensive coatings. This local differentiation allows the system to achieve high overall solar absorptivity while reducing the total amount of degradable coating material required.
Solution Approach 2:
The cylindrical geometry of the panels and their circular arrangement create self-service light trapping, where reflected sunlight from one panel automatically impinges on adjacent panels without requiring additional coating layers. This geometric self-service mechanism reduces dependence on expensive, degradable coatings by using the receiver's own structure to enhance solar absorption, thereby improving long-term reliability and reducing maintenance requirements.
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 increases thermal efficiency by up to 10% and reduces heat losses by 50%, achieving higher performance and cost savings while maintaining high temperatures, and enabling a smaller receiver footprint with improved energy conversion efficiency.
Implementation Method 1
one or more of the plurality of solar panels is arranged to reflect and/or radiate solar energy to one or more other solar panels to trap the reflected and/or radiated solar energy
Implementation Method 2
one or more of the plurality of solar panels is arranged to reflect and/or radiate solar energy to one or more other solar panels to trap the reflected and/or radiated solar energy
Implementation Method 3
a plurality of solar absorbing surfaces arranged such that light or heat reflected from or emitted from, respectively, one or more of the plurality of solar absorbing surfaces impinges one or more other solar absorbing surfaces
Data Source
AI summary
Solar receivers including a plurality of multi-scale solar absorbing surfaces arranged such that light or heat reflected from or emitted from one or more of the plurality of solar absorbing surfaces impinges one or more other solar absorbing surfaces of the solar receiver. The disclosed receivers increase the amount of absorbed energy from a concentrated light source, such as a heliostat field, and reduce radiative and convective heat losses.