Active Electrochromic Thermal Control Devices, 14-R9878Printer Friendly Version
Inclusive Dates: 10/01/08 03/31/10
Background - Thermal management is critical for optimum functionality of many systems. These systems can include sensitive electronics with high-power processors or billion dollar spacecraft orbiting Earth. In general, there are two types of thermal control systems: active and passive. An active system is typically used in addition to the passive system when the passive system is not adequate. Examples of active thermal control systems include heat pipes, heat exchangers, evaporators and louvers.
SwRI researchers developed novel active thermal control devices based on solid-state, thin-film electrochromic (EC) materials. By proper choice of the electrochromic material, the reflectance [or equivalently, the emissivity (ε)] of the device in the infrared is modulated by applying an external electrical potential. The emissivity is reversed by changing the polarity of the applied potential.
Approach - The primary objective of this project was to demonstrate the feasibility of fabricating novel active thermal control devices based on thin-film electrochromic materials. The following specific objectives were achieved during the project to meet the primary objective.
- During this project, SwRI fully characterized numerous organic and inorganic
electrochromic materials. Furthermore, techniques were developed for
fabricating electrochromic devices that operate in the longwave infrared (8
to 12 microns). The final demonstrator device used a novel current collector
configuration resulting in a unique device design. The final device demonstrated an emissivity modulation from a
high emissivity state (ε~0.8) to a low emissivity state (ε~0.5) by applying
a small voltage. Lastly, the devices demonstrated emissivity modulation over
10,000 cycles at high (90 °C) and low (-30 °C) temperatures. Figure 1.
Thermal infrared image of an electrochromic thermal control device in its high emissivity state (left) and low emissivity state (right).
Figure 1. Thermal infrared image of an electrochromic thermal control device in its high emissivity state (left) and low emissivity state (right).