Shadow Band Pyranometer With Arcuate Arm and Self-Cleaning Tracking
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Solution Overview
Problem
Conventional shadow band pyranometers require frequent adjustments to compensate for the changing declination of the sun and can be complex and costly, with existing solutions either cumbersome or expensive, and lack effective cleaning mechanisms for the sun sensors.
Innovation Solution
A motor-driven shadow band pyranometer with a centrally located sun sensor and an arcuate shade arm that traverses 90 degrees, featuring a fluid nozzle for cleaning and optional additional sensors for automatic tracking and bird deterrence, allowing for automatic adjustment and easy maintenance without casting shadows on sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional shadow band pyranometer uses a fixed shadow band to block direct solar radiation, then it can measure diffuse solar radiation, but it requires frequent adjustments to compensate for the changing declination of the sun
Solution Approach 1:
The shadow band is replaced with a motor-driven arcuate shade arm that automatically rotates to track the sun's movement across the sky. This dynamic system continuously adjusts the shading position without manual intervention, eliminating the need for frequent adjustments while maintaining accurate blocking of direct solar radiation throughout the day
Solution Approach 2:
The system employs automatic tracking mechanisms with sensors that detect the sun's position and autonomously control the shade arm's rotation. The pyranometer system serves itself by automatically compensating for the changing declination of the sun without requiring external manual adjustment
2Ease of operation
If a two-axis sun tracker with shading balls is used to automatically track the sun, then adjustments are eliminated, but the apparatus becomes extremely complicated and costly
Solution Approach 1:
The complex two-axis tracking system is simplified by segmenting the function into a single arcuate shade arm that rotates along a predetermined arc path. This segmented approach separates the tracking function from the shading function, achieving automatic sun tracking with a simpler single-axis mechanism rather than a complex two-axis system
Solution Approach 2:
A simplified intermediary mechanism (the arcuate shade arm mounted on a motor-driven platform) is introduced to mediate between the sun's movement and the shading requirement. This intermediary component performs the tracking function with minimal complexity compared to the direct two-axis sun tracker approach
3Device complexity
If a fixed shadow band structure is used, then the structure is simple, but it cannot be easily cleaned and maintenance is difficult
Solution Approach 1:
The static fixed shadow band structure is replaced with a dynamic motor-driven platform and rotateable shade arm assembly. This dynamic structure enables the cleaning nozzle to be positioned directly over the sun sensor by rotating the platform and arm, providing easy access for cleaning while maintaining structural simplicity through standardized components
Solution Approach 2:
The system incorporates a self-cleaning capability through an integrated fluid nozzle that can be automatically positioned to clean the sun sensor. The motor-driven platform and rotateable arm enable the cleaning function to be performed easily without requiring disassembly or complex access mechanisms
Data Source
AI summary
A shadow band assembly includes a platform and an arcuate shadow arm extending upward from the platform and terminating in a free end above the platform. A sun sensor mounting location is located below the free end of the shadow arm. The arm is preferably further supported by a vertical strut. According to other embodiments, the arm is hollow and contains a fluid conduit and/or an electrical cable. A sun sensor may be mounted on top of the free end of the arm and a fluid nozzle may be mounted under the free end. A shadow band pyranometer includes the shadow band assembly, a sun sensor mounted at the mounting location and a motor drive coupled to the platform for azimuth tracking. Additional sensors with zenith tracking may also be provided.