Materials

Ultra-clear aerogel designed for better, less costly solar collectors

Ultra-clear aerogel designed f...
A sample of the aerogel, with parallel laser beams running through it to make it visible for the photo
A sample of the aerogel, with parallel laser beams running through it to make it visible for the photo
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A sample of the aerogel, with parallel laser beams running through it to make it visible for the photo
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A sample of the aerogel, with parallel laser beams running through it to make it visible for the photo
A test device installed on a rooftop at MIT proved the effectiveness of the aerogel
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A test device installed on a rooftop at MIT proved the effectiveness of the aerogel

We may hear a lot about photovoltaic panels, but solar collectors are also quite useful – the devices collect heat from sunlight, which is used in applications such as the heating of homes. Now, MIT has announced the development of a new material that could make them cheaper and more efficient than ever.

Currently, solar collectors often incorporate an array of reflectors that focus sunlight onto one central collection device. That device in turn incorporates a clear sheet of glass over top of a dark, heat-absorbing material, with a vacuum in the empty space between them. Such setups can be expensive and complex, however, plus much of the gathered heat simply escapes back out through the glass panel.

With that in mind, a team at MIT developed a silica-based aerogel to replace the glass.

The material is clear enough to let a lot of sunlight through, but it also has a high enough insulating value to keep the heat inside. As a result, when a collector that incorporated the aerogel was tested on an MIT rooftop at outdoor winter temperatures below 0 ºC (32 ºF), the heat-absorbing material within it was able to maintain a temperature of 200 ºC (392 ºF).

A test device installed on a rooftop at MIT proved the effectiveness of the aerogel
A test device installed on a rooftop at MIT proved the effectiveness of the aerogel

Consisting of "abundant and inexpensive" ingredients, the aerogel starts out as a liquid that gets rapidly dried out. What's left behind is a material that's mostly made up of air, and that has very small spaces between its silica grains due to the quick-drying process. This quality makes it much more transparent than other insulating aerogels, with a light transmission rate of over 95 percent – by contrast, previously-developed aerogels have only been able to manage about 70 percent.

It is now hoped that once the technology is developed further, solar collectors incorporating the aerogel could be used to heat water in pipes, that water then being pumped through home heating systems. Before that can happen, though, the cost of the drying process needs to be brought down – a specialized device known as a critical point dryer is currently required, and it isn't suitable for commercial-scale production of the collectors.

A paper on the research was recently published in the journal ACS Nano.

Source: MIT

1 comment
Don Duncan
Why can't a glass that lets in IR but not out be made, since the IR radiated from inside is shorter wave length?