The present project seeks to show the feasibility for the manufacturing of a solid-state variable transmission glazing based on the phenomenon of electrochromism. The resulting device has memory and can be electrically controlled to obtain gradual but reproducible changes in optical properties through the visible and near infrared range of wavelengths. This can be performed manually or computer controlled as part of the energy management system in buildings.
This is the third phase of an ongoing project started in 1989. The result of the previous two phases of this project has been to demonstrate suitable materials for the construction of a five layer device. In particular an electrochromic coating, a counter-electrode (or storage layer) and a polymeric electrolyte have been established with electrochromic efficiency of the order of 30 cm2/C, a charge capacity in excess of 20 mC/cm2 and ionic conductivity of between 10-5 to 10-4 Siemens/cm respectively.
In addition good life time and durability have been shown in small area (100 mm x 100 mm) devices and a technology demonstrator with the same area has been constructed with performance close to that envisaged for a commercially viable product.
Device design and more specifically, coating design will be explored in an attempt to optimise solar control performance . This will include the use of the near infrared absorption inherent in this type of device as well as the use of variable near infrared reflectance, obtained in highly crystalline materials. Life time assessment will form a major part of the investigations (Pilkington) and electrochemical assessment (Southampton) will be a crucial topic needed for establishing key mechanisms and parameters giving rise to device performance. In addition it will enable us to predict possible changes in behaviour resulting from the expected long cycling schedule that this type of advanced glazing will undergo in practice.
Expected Achievements and Exploitation
- the production of low-cost active coatings for variable transmission windows;
- a portfolio of technologies and materials with performance compatible with the requirements for a commercially viable product;
- an understanding of the factors affecting device performance and life time.
Funding SchemeCSC - Cost-sharing contracts
OX3 0BP Oxford
SO17 1BJ Southampton