Smart Thermal Radiator based on Thermo-chromic Coatings on Aluminum
Traditionally in the absence of air, the thermal control of spacecraft relies on removing heat through radiative heat transfer to deep space via space radiators. Due to orbit parameters and operational needs the overall internal spacecraft heat load may change. As the radiator continues to reject heat, parts of the spacecraft and equipment may further cool down. To compensate this effect on-board heaters are used to maintain the structures and equipment within their desired temperature limits.
Thermochromic radiators are one way to address this challenge. Specially prepared coatings are applied to the space radiator which can either reject the heat at the higher temperatures, or reject less heat at the lower temperatures. LSMO (Lanthanum Strontium Manganese Oxide) coatings are well known to exhibit thermochromic characteristics which can match this requirement. These coatings however are difficult to apply directly to aluminum radiator substrates, requiring a costly and complex buffer layer for proper adhesion. In addition this buffer layer can degrade the thermo-optical characteristics of the radiator.
The Canadian Space Agency (CSA) research and engineers have developed two technologies that improve the performance and the fabrication of smart thermal radiators for spacecraft;
- an improved topcoat for thermochromic coating material that reduces solar absorptivity,
- a simplified low cost method to deposit the thermochromic coating on a modified aluminum substrate.
The topcoat reduces the absorption of inbound solar radiation by the thermal radiator. The improved deposition process involves modifying the aluminum surface to improve the adhesion of the LSMO thermochromic coating without a separate buffer layer. This increases the heat transfer efficiency, enhances robustness and reduces mass and manufacturing costs. It is anticipated that the technology may be extended to applications where other substrate materials are used.
Figure 1 compares the measured temperature dependence of εT of the La1-xSrxMnO3 (x = 0.175 and 0.3)-coated silicon, and aluminum substrates to that of copper substrate, whereby the fabricated LSMO coating on Si and aluminum substrates was measured by calorimetric method.
Figure 2 illustrates total hemispherical emittance.
Applications for smart thermochromic coatings include satellite thermal radiators, electro-optical instruments in space, and smart windows. For applications based on LSMO coatings on aluminum substrate, the technology is strongly applicable to space thermal radiators, and represents a meaningful improvement to the state of the art. The opportunity for application of the technology in commercial consumer products such as smart windows is potentially significant, but additional research and development is required.
The Business Opportunity
The thermochromic coating technology developed by CSA represents an opportunity for industry to directly apply this coating innovation to the space thermal radiators or other applicable products, in order to improve the performance, robustness and cost.
The technology has been developed and may be demonstrated by CSA to interested parties. Provisional patent applications protecting the technology have been filed in USA and Canada. The CSA is seeking partners who are interested in licensing the intellectual property and know-how, or collaborating in further development.
Technology Transfer Details
A commercialization license for this technology is available.
The business opportunity may be referred to by its CSA case ID: 51032
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