Quartz Glass Receiver Window Thickness to Prevent Devitrification
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Solution Overview
Problem
Solar radiation receivers face efficiency limitations due to devitrification of quartz glass windows at high temperatures, which reduces their service life and increases maintenance costs, while existing cooling methods either reduce energy absorption or are complex and energy-intensive.
Innovation Solution
A solar radiation receiver with a dome-shaped quartz glass window of varying thickness, configured to maintain a temperature difference of at least 150°C across the window, decoupling the outside temperature from the inside absorber temperature, and a method for producing such windows using a plasma-densified SiO2 grain layer to achieve high dimensional stability and reproducibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the absorber temperature is increased to improve energy conversion efficiency, then the energy conversion efficiency is improved, but the window temperature increases causing devitrification of the quartz glass
Solution Approach 1:
The invention changes the physical parameter of the window (wall thickness) to alter the temperature distribution. By increasing the wall thickness to at least 7 mm, the thermal insulation capability is enhanced, creating a larger temperature gradient across the window wall that keeps the outer surface temperature below the devitrification threshold while allowing the inner surface to withstand high absorber temperatures for efficient energy conversion.
Solution Approach 2:
The invention addresses the temperature problem by transitioning from a two-dimensional surface issue to a three-dimensional volume issue. Instead of trying to cool the outer surface directly, the solution lies in the third dimension - the wall thickness - which provides thermal resistance and creates a temperature gradient through the window material, decoupling the inner and outer surface temperatures.
2Temperature
If active cooling measures are implemented to reduce window temperature, then the window temperature is reduced, but the device complexity and energy consumption increase
Solution Approach 1:
The window structure serves its own cooling function through its inherent thermal insulation properties. The thick quartz glass wall acts as a thermal barrier that naturally limits heat transfer to the outer surface, eliminating the need for external active cooling systems. The structure itself provides the temperature control function without requiring additional mechanical cooling devices.
Solution Approach 2:
The invention extracts the cooling function from the system by relying on the passive thermal insulation property of the thick quartz glass wall. Instead of adding an active cooling subsystem, the solution removes the need for such systems by utilizing the material's inherent thermal resistance to naturally maintain the outer surface temperature below devitrification levels.
3Loss of energy
If the window wall thickness is increased to reduce heat conduction, then the temperature difference across the window is increased, but the manufacturing complexity and cost increase
Solution Approach 1:
The invention changes the critical parameter of wall thickness to at least 7 mm, which fundamentally alters the thermal performance of the window. This parameter change provides sufficient thermal insulation to maintain the required temperature gradient while remaining within manufacturable limits for quartz glass components, balancing thermal efficiency with manufacturing feasibility.
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 configuration allows for higher absorber temperatures and increased energy conversion efficiency while minimizing devitrification risks, reducing maintenance needs, and enabling longer window service life without the need for active cooling or infrared shielding.
Implementation Method 1
densifying the SiO2 grain layer under action of a plasma and by applying a negative pressure acting from the outside through the porous wall on the grain layer so as to form a blank of the window
Implementation Method 2
densifying the SiO2 grain layer... to form a blank of the window... mechanically removing an outer portion of the blank so as to form a preform of the window
Implementation Method 3
due to heat conduction the window outside is also heated up to temperatures of several 100 degrees Celsius
Implementation Method 4
Due to its dome-shaped configuration the back reflection of radiation out of the absorber is reduced
Implementation Method 5
The solar radiation enters via the window into a so-called absorber which has an operating gas flowing therethrough and which thereby heats up the same in a solar thermal manner
Data Source
AI summary
Common solar radiation receivers are equipped with a chamber for transmission of an operating gas which is directed along to an absorber for solar radiation for thermal absorption. The absorber has a dome-shaped entry window made of quartz glass, wherein the inner side facing the absorber assumes a nominal interior temperature Ti of at least 950° C. during proper use, preferably at least 1000° C., whereas the outer side facing away from the absorber is exposed to the environment and subject to risk of devitrification. The invention relates to modifying the known solar radiation receiver so that a high absorber temperature can be set and thus a high efficiency of the solar thermal heating is enabled, without increasing the risk of devitrification in the region of the outer side of the entry window.