Shadow Band Pyranometer Assembly for Automatic Solar 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, which can be retrofitted to existing equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional shadow band pyranometer is used, then direct solar radiation can be blocked throughout the day, but frequent adjustments are required to compensate for changing solar declination
Solution Approach 1:
The shadow band is made movable and adjustable in position relative to the pyranometer sensor. The band can be rotated about the sensor axis and tilted at various angles, allowing dynamic repositioning to maintain effective shadow blocking as solar declination changes throughout the year, eliminating the need for frequent manual adjustments
Solution Approach 2:
The shadow band is divided into multiple segments or sections that can be independently positioned and adjusted. This segmentation allows each portion of the band to be optimized for blocking solar radiation at different times of day and seasonal angles, improving overall blocking effectiveness while reducing adjustment frequency
2Extent of automation
If shading balls with motor drive are used to track the sun, then automatic shadow blocking is achieved, but the apparatus becomes extremely complicated and costly
Solution Approach 1:
The shadow band serves multiple functions: it blocks direct solar radiation, provides a reference for diffuse radiation measurement, and can be positioned to accommodate different solar angles throughout the year. This multi-functionality eliminates the need for complex motorized tracking systems while achieving automatic adaptation to changing solar positions
Solution Approach 2:
The complex motor drive mechanism and active tracking system are removed from the design. Instead, the shadow band passively adapts to solar position changes through its adjustable geometry, extracting the essential shadow-blocking function while eliminating unnecessary mechanical complexity
3Device complexity
If a fixed shadow band structure is used, then the design is simple, but the band casts shadow on additional sensors and requires frequent adjustment
Solution Approach 1:
The shadow band structure incorporates dynamic adjustment capabilities allowing the band to be tilted and rotated to maintain optimal positioning relative to the sensor as solar declination changes. This dynamic geometry maintains shadow blocking accuracy without requiring frequent manual intervention
Solution Approach 2:
The shadow band is positioned asymmetrically at an optimized angle and distance from the sensor, creating an asymmetric geometric relationship that maximizes shadow blocking effectiveness while minimizing the band's own shadow impact on the sensor across different solar positions
4Measurement precision
If sun sensors are exposed to direct sunlight, then they can measure total solar radiation, but they require frequent cleaning to maintain accuracy
Solution Approach 1:
The shadow band acts as an intermediary element that selectively blocks direct solar radiation from reaching the pyranometer sensor during certain times of day while allowing diffuse radiation to reach the sensor. This intermediary positioning protects the sensor from direct sunlight exposure that would require frequent cleaning, while still enabling accurate diffuse radiation measurement
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
Eliminates the need for frequent adjustments, prevents shadowing of sensors, facilitates easy cleaning, and provides automatic tracking capabilities, enhancing the operational efficiency and durability of shadow band pyranometers while being cost-effective and adaptable.
Implementation Method 1
a fluid nozzle for cleaning... facilitates easy cleaning
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.