Seasonal Solar Heat Storage for a Greenhouse, +15C in -40′ Geo Liquid (2018)
Scientists have developed a transparent airgel that allows sunlight to pass through but blocks heat from escaping and is able to maintain high temperatures. It can be used to create a passive system that replaces vacuum collectors, for collecting and supplying heat to homes or for industrial processes requiring more than 200 °C.
The key to the effectiveness of the new lightweight foam, composed primarily of air and silica, is its high transparency. This was achieved due to the exact ratio of the various materials used to create it by mixing the catalyst with grains of a silica-containing compound in a liquid solution, forming a kind of gel, and reducing pores during the drying process. The resulting airgel transmits 95% of sunlight while maintaining its insulating properties.
In tests on a rooftop at the Massachusetts Institute of Technology campus, a passive device consisting of a heat-absorbing dark material covered with a layer of new material was able to heat up and maintain a temperature of 220 °C in the middle of winter when the ambient air was below zero.
Previously, similar results could be achieved using concentrating systems with mirrors to focus light on a central point or expensive vacuum solar collectors. However, the developed airgel makes it possible to create simple heating or heat systems for the chemical or food industry. The team also offers direct connections to pipes and heat transfer devices, without pumps or any moving parts..
Recently, a conductive airgel has also been developed that remains elastic even in liquid nitrogen..
text: Ilya Bauer, photo: Massachusetts Institute of Technology