Portable Spectrophotometer for Solar Tube Reflection and Transmission
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Solution Overview
Problem
Existing optical measurement devices for characterizing the reflection and transmission coefficients of solar thermal energy collector tubes are not portable, sensitive, or capable of performing quick and accurate spectral measurements under high-intensity ambient light conditions, lacking the necessary dynamic range and mechanical configuration for efficient in-field use.
Innovation Solution
A portable device utilizing LEDs to cover specific wavelength ranges, combined with four photodetectors and digital signal processing for high sensitivity measurements, and wireless data transmission to a computer for storage, allowing simultaneous measurement of transmission and reflection coefficients without adjustments, and capable of operating in ambient light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a broad spectrum light source with a movable diffraction grid is used for spectral measurement, then wavelength selection is continuous and flexible, but the device becomes complex, delicate, and has low dynamic measurement range
Solution Approach 1:
The continuous spectrum is segmented into discrete wavelength bands using fixed filters. Each filter corresponds to a specific wavelength range, allowing the system to cover the solar spectrum through multiple discrete measurement channels rather than requiring a continuous scanning mechanism
Solution Approach 2:
Multiple fixed filters covering different wavelength ranges are combined in a single measurement system. The filters are positioned to simultaneously or sequentially measure different spectral regions, merging their functions into one integrated device that achieves spectral coverage without moving parts
2Adaptability or versatility
If a movable diffraction grid is used for wavelength selection, then continuous wavelength variation is achieved, but the input light power becomes very low
Solution Approach 1:
The spectral separation is performed preliminarily through fixed filters positioned in the optical path before the light reaches the detector. This preliminary filtering approach eliminates the need for moving diffraction grids during measurement, maintaining high light throughput while achieving spectral resolution
Solution Approach 2:
The mechanical movable diffraction grid is replaced with a static optical system using fixed filters. This substitution eliminates moving parts while maintaining spectral measurement capability, and preserves light power by avoiding the losses associated with mechanical scanning and diffraction
3Measurement precision
If conventional spectrophotometers are used for measuring solar collector tubes, then spectral characterization is possible, but the devices are not portable and cannot operate effectively under high-intensity ambient light
Solution Approach 1:
The system uses periodic modulation of the light source or measurement sequence to distinguish the measurement signal from ambient light. By modulating the illumination and synchronizing the detection, the system can extract the desired spectral information while rejecting the unmodulated ambient light background
Solution Approach 2:
The fixed filters act as intermediaries that selectively transmit specific wavelength ranges while blocking others. This allows the system to measure in the presence of ambient light by focusing only on specific spectral bands where the measurement signal can be distinguished from the background
4Measurement precision
If sequential measurement at different wavelengths is performed using fixed filters, then spectral measurement is achieved, but transmission and reflection measurements require position adjustments
Solution Approach 1:
The optical paths for transmission and reflection measurements are merged into a single integrated system. Multiple detectors are positioned to simultaneously receive light for both transmission and reflection measurements, allowing both types of measurements to be performed at all wavelengths without mechanical repositioning
Solution Approach 2:
The system is designed with multi-functionality to perform both transmission and reflection measurements using the same optical components and detectors. The fixed filters and detectors serve multiple measurement modes simultaneously, eliminating the need for separate measurement setups or position adjustments
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
Enables accurate, quick, and sensitive spectral characterization of solar thermal energy collector tubes, improving measurement efficiency and flexibility for in-field use, particularly in high-intensity light conditions.
Implementation Method 1
several light-emitting diodes or LEDs, which cover the wavelength range within which absorbing tubes want to be characterized
Implementation Method 2
Four photodetectors for each pair of used LEDs, for obtaining reflection, transmission and reference signals for each wavelength
Data Source
AI summary
Portable spectrophotometer and method for characterizing solar collector tubes for simultaneously and on-field characterizing reflection and transmission coefficients. This device includes all the components needed to take this measurement, such as a module that takes the measurement of the reflection coefficient (R) of the inner tube (1′), a module that takes the measurement of transmission coefficient (T) of the outer tube (1″), an electronic data acquisition and processing system (12), an external computer (13) for controlling the device and sending the measured data (17) and a communication system (15) between device and the computer (13).