Highly Insulating and Light Transmitting Aerogel Glazing for Super Insulating Windows (HILIT+): - confidential final technical report, EU-FP5 contract ENK6-CT-2002-00648.

The first main objective deals with “aerogel process optimisation”. The general goal was to demonstrate that the elaboration process, developed during the recent HILIT project, permitted to obtain a significant amount of light transmitting, insulating and transparent 15-20 mm monolithic and crack-free nano-structured aerogel materials through a reasonably fast and reproducible process. The applicative part of this project aimed at elaborating, studying and optimising “state-of-the-art” (0.5 W/m2 K) aerogel glazings for windows. An important issue was the risk of outside condensation and rime and its avoidance. The final aerogel window is optimised with regard to its production and performance in view of the technical, economical and life cycle aspects. The aerogel production process has been optimised and tuned so monolithic silica aerogel sheets are produced with more than 85% crack free sheets per batch. Furthermore the production time has been reduced to 1/3 of the initial production time through detailed theoretical and experimental analyses of especially the supercritical washing step included in the drying phase. At the same time the production plant have been modified to recycle most of the chemicals involved in the production process. A large number of aerogel glazing prototypes have been made with partly evacuated aerogel in between two layers of low iron and anti-reflection coated glass panes with an airtight edge seal solution based on multi-layered plastic foil developed for vacuum insulation purposes. The edge seal solution shows only a very limited thermal bridge effect. The final glazing has a total solar energy transmittance above 85% and a U-value of 0.7 W/m2 K for about 14 mm aerogel thickness, which for a 20 mm thickness corresponds to a U-value of approximately 0.5 W/m2K. No other known glazing exhibits such an excellent combination of solar transmittance and heat loss coefficient. The annual energy savings compared to triple low energy glazing is in the range of 10 – 20% depending on type of building. Beside the application in glazing production the HILIT+ aerogel material it self has a large variety of applications: • Thermal insulation in various fields from cryogenic applications (spatial tankers, …) to high-temperature applications (ovens, …) passing by moderate temperatures (pipelines, risers, geothermal resources, …) • Due to the large internal surface of aerogel (up to 1000 m²/g), the material is proposed to serve as substrate for catalytic materials. • The special pore structure of aerogel could be used for gas filters in the 20 to 100 nm region. • The sound velocity within aerogel is in the range of 100 to 300 m/s, which should be one of the lowest for an inorganic material. Due to the low density, the acoustic impedance of aerogel could help boost the efficiency of piezoelectric transducers. • Waste encapsulation, spacers for vacuum insulation panels, membranes, etc.