MIT aerogel captures solar heat for domestic and industrial applications

Aerogels are paradoxical materials. So ephemeral as to seem barely there, they have extraordinary properties. The MIT team, a collaboration between engineers from different specialities, has developed a material claimed to be capable of transmitting solar light while efficiently trapping solar heat.

In a paper in the journal ACS Nano, Evelyn Wang, head of the Department of Mechanical Engineering, graduate student Lin Zhao, professor of power engineering Gang Chen and colleagues describe how they produced the aerogel (which they refer to as a greenhouse medium) by controlling the hydrolysis and condensation rates of tetramethyl orthosilicate (TMOS). They discovered a novel process to do this, which, they explain, not only improves the optical transparency of the material but also reduces the fabrication time from weeks to days.

The key to making it work was in the precise ratios of the different materials from which the aerogel was synthesised, the paper explains. The process consists of mixing a catalyst with grains of a silica-containing compound in a liquid solution, and then drying the resulting gel to leave a matrix which is mostly air but which retains the mechanical strength of the original mixture. Producing a mixture which dries out much faster than conventional hydrogel precursors produced a gel with much smaller pore size between its grains, resulting in less scattering of light.