Toroidal Heliostat Curvature for Passive Astigmatism Control
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Solution Overview
Problem
Heliostats in concentrating solar power installations face inefficiencies due to astigmatism, which causes variations in the size of the reflected image throughout the day, leading to wasted energy and increased heat loss, and existing solutions to minimize astigmatism are complex and costly.
Innovation Solution
A toroidal heliostat with a reflector frame that passively adjusts its curvature in sagittal and tangential directions through gravitational, thermal, and mechanical means, optimizing focal lengths to maintain consistent energy delivery and reduce manufacturing and maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a spherical or planar reflective surface is used in a heliostat, then the device complexity and manufacturing cost are reduced, but astigmatism causes the reflected image size to vary throughout the day, leading to energy waste and reduced efficiency
Solution Approach 1:
The patent applies a toroidal curvature to the reflective surface instead of a spherical or planar surface. The toroidal shape has different radii of curvature in orthogonal directions (tangential and sagittal), which allows independent optimization of focal lengths to compensate for astigmatism. This curved surface maintains consistent image size and energy density throughout the day while managing the complexity through a statically pre-formed geometric shape.
2Loss of energy
If a toroidal reflector with different focal lengths for tangential and sagittal directions is used, then astigmatism effects are minimized and energy concentration is improved, but the manufacturing precision and alignment requirements increase
Solution Approach 1:
The patent pre-calculates and pre-forms the toroidal reflector with specific static curvatures in orthogonal directions during manufacturing. The radii of curvature in the tangential and sagittal directions are determined in advance based on the desired focal point and operational parameters. This preliminary design and fabrication of the correct geometric shape eliminates the need for complex active adjustment mechanisms during operation, thereby reducing operational complexity while maintaining manufacturing precision requirements.
3Productivity
If active curvature adjustment mechanisms are implemented to optimize focal lengths, then energy delivery consistency is improved, but the device complexity and maintenance costs increase significantly
Solution Approach 1:
The patent employs a statically pre-formed toroidal reflector that passively maintains optimal curvature characteristics without requiring active adjustment mechanisms. The reflector's geometry is designed to inherently compensate for astigmatism and maintain consistent energy delivery throughout the day. This self-service approach eliminates complex actuators, sensors, and control systems that would be required for active curvature adjustment, thereby reducing device complexity and maintenance requirements while preserving energy delivery consistency.
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 passive adjustment of focal lengths in the toroidal heliostat enhances energy concentration and efficiency, reducing the complexity and cost associated with active curvature adjustment systems while minimizing astigmatism effects, leading to improved power delivery and reduced energy losses.
Implementation Method 1
A toroidal heliostat with a reflector frame that passively adjusts its curvature in sagittal and tangential directions through gravitational, thermal, and mechanical means
Implementation Method 2
A toroidal heliostat with a reflector frame that passively adjusts its curvature in sagittal and tangential directions through gravitational, thermal, and mechanical means
Implementation Method 3
A toroidal heliostat with a reflector frame that passively adjusts its curvature in sagittal and tangential directions through gravitational, thermal, and mechanical means
Implementation Method 4
A heliostat is a device generally provided in a fixed location that includes a reflective surface to reflect solar energy toward a predetermined, fixed target
Data Source
AI summary
A toroidal heliostat and reflector frame for a heliostat are provided which passively adjust the apparent sagittal and/or tangential focal lengths of the reflector. This adjustment is provided by way of passive deflection of the reflector caused by one or more of gravitationally-induced deflection of one or more components of the heliostat; differential thermal expansion of materials of the heliostat; and/or relative movement between two or more components of the heliostat. Careful design of the heliostat enables optimisation of the power delivery profile and/or shape of the reflected image throughout the day.