Variable-Emissivity Electrochromic Device for Space Thermal Control
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Solution Overview
Problem
Current electrochromic devices for spacecraft thermal control face challenges such as high weight, toxicity, expense, poor efficiency, and inability to function in high vacuum and extreme temperature conditions, particularly for micro- and nano-spacecraft, due to limitations in existing conducting polymer electrochromics that are either non-functional or 'dark' in low-emittance states, leading to rapid heating and degradation.
Innovation Solution
A flexible, variable-emittance electrochromic device utilizing IR-active conducting polymers and ionic liquid electrolytes, with a microporous membrane substrate and heat/potential activation method to incorporate counterions, enabling efficient switching and thermal management in high vacuum and extreme temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conducting polymer electrochromics are used, then electrochromic activity is achieved, but dead regions with poor structure and oligomer precipitates reduce light state performance and cause rapid heating
Solution Approach 1:
The patent changes the polymerization method from conventional electrochemical polymerization to a new approach that prevents poor structure formation. By modifying the polymerization parameters and using specific dopants, the invention eliminates dead regions and oligomer precipitates while maintaining electrochromic activity, thus preventing rapid heating and degradation.
Solution Approach 2:
The patent creates a composite structure by incorporating the conducting polymer into a porous substrate matrix. This composite approach prevents oligomer precipitate formation and eliminates dead regions by providing a structured framework that supports uniform polymer distribution, thereby improving thermal management and preventing rapid heating.
2Temperature
If existing electrochromic devices are used for spacecraft thermal control, then thermal management is achieved, but high weight, toxicity, and expense limit applicability to micro- and nano-spacecraft
Solution Approach 1:
The patent employs thin film structures of conducting polymers deposited on porous substrates, replacing bulky conventional electrochromic devices. This thin film approach dramatically reduces device weight and thickness while maintaining thermal control functionality, making the technology suitable for weight-sensitive micro- and nano-spacecraft applications.
Solution Approach 2:
The patent uses porous substrates with optimized pore sizes and conducting polymers with tailored properties to achieve local optimization of thermal control. By selecting specific material compositions and structures, the device achieves effective thermal management with minimal mass, addressing the weight constraints of small spacecraft.
3Reliability
If conventional electrolytes are used, then electrochemical function is achieved, but inability to function in high vacuum and extreme temperature conditions limits space application
Solution Approach 1:
The patent employs ionic liquid electrolytes that function as inert environments resistant to high vacuum and extreme temperature conditions. These electrolytes maintain electrochemical functionality in space environments where conventional electrolytes would evaporate or decompose, enabling reliable operation in high vacuum and thermal extremes.
Solution Approach 2:
The patent uses solid-state ionic liquid electrolytes that replace volatile liquid electrolytes, eliminating evaporation issues in vacuum. These solid electrolytes are designed to be stable and long-lasting in extreme conditions, ensuring continuous electrochemical function throughout the spacecraft mission lifecycle.
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 device achieves efficient solar radiation reflection and heat emission control, with high transparency and low solar absorptance, allowing for flexible thermal management in space environments, overcoming the limitations of existing technologies by maintaining performance across a wide temperature range and reducing material thickness.
Implementation Method 1
The change in color of an electrochromic material is generally due to a reduction/oxidation ('redox') process within the material
Implementation Method 2
Certain conducting polymers are among the few materials capable of modulating light in both the Visible and IR regions. Those materials which are active in the IR region of the electromagnetic spectrum, capable of electrochromically modulating IR light may be referred to as 'IR-active' electrochromic materials
Implementation Method 3
Redox in these materials is accompanied by inflow or outflow of counterions or 'dopants' from the polymer matrix
Implementation Method 4
an ionic liquid electrolyte in electrochemical communication with the conducting polymer layer with the ionic liquid electrolyte comprising at least one counterion and wherein the electrochromic conducting polymer layer substantially incorporates the at least one counterion of the ionic liquid electrolyte
Implementation Method 5
A high % R in the reflective (high-reflectance) state and a low % R in the absorptive (low-reflectance) state leads to high contrast (Delta % R)
Implementation Method 6
Another property relevant to the performance of reflectance-mode devices, specifically in the IR spectral region, is the emissivity; this is a property that describes the ability of a material to give out heat
Implementation Method 7
with low solar absorptance, allowing for flexible thermal management in space environments
Data Source
AI summary
Variable-emittance, electrochromic devices utilizing IR-active conducting polymers and methods of preparing the same are disclosed.